Radiative Effect on Natural Convection Flows in Porous Media

A regular two-parameter perturbation analysis based upon the boundary layer approximation is presented here to study the radiative effects of both first- and second-order resistances due to a solid matrix on the natural convection flows in porous media. Four different flows have been studied, those adjacent to an isothermal surface, a uniform heat flux surface, a plane plume and the flow generated from a horizontal line energy source on a vertical adiabatic surface. The first-order perturbation quantities are presented for all these flows. Numerical results for the four conditions with various radiation parameters are tabulated.     

Mixed Convection–Radiation Interaction in Power-Law Fluids Along a Nonisothermal Wedge Embedded in a Porous Medium

A boundary layer analysis has been presented for the interaction of mixed convection with thermal radiation in laminar boundary flow from a vertical wedge in a porous medium saturated with a power-law type non-Newtonian fluid. The fluid considered is a gray medium, and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The transformed conservation laws are solved numerically for the case of variable surface temperature conditions. Results for the details of the velocity and temperature fields as well as the Nusselt number have been presented.     

Hyperbranched polyesters based on polycondensation of 1,3,5‐tris(2‐hydroxyethyl) cyanuric acid and 3,5‐dihydroxybenzoic acid

A series of hyperbranched polyesters was produced by the condensation of the monomer 3,5‐dihydroxybenzoic acid with 1,3,5‐tris(2‐hydroxyethyl) cyanuric acid as a trifunctional central core. The monomer‐to‐core ratio was varied between 3 and 45. The resulting polymers were phenolic‐terminated polyesters. The degree of branching of the polyesters was calculated according to the method described by Fréchet and was found to be in the range of 0.7–0.8. The number‐average molecular weights calculated via ¹H NMR spectroscopic degree‐of‐polymerization values are in reasonable agreement with the predicted values derived from the monomer‐to‐core ratio for all prepared polyesters. Thermal and photophysical properties were also studied. Glass‐transition temperatures were determined by differential scanning calorimetry and were found to be relatively independent of the theoretical molar mass. The polyesters were found to be blue emitters, and the solutions exhibited intense fluorescence, with a maximum of 430 nm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3278–3288, 2005     

Optimal preventive maintenance policy for electric power distribution systems based on the fuzzy AHP methods

In power distribution systems, with their great vastness and various outage causes, one of the most important problems of power distribution companies is to select a suitable maintenance strategy of system elements and method of financial planning for the maintenance of system elements with the two objectives of decrease in outage costs and improvement of system reliability. In this article, a practical method is introduced for the selection of a suitable system elements maintenance strategy; moreover, to plan the preventive maintenance budget for the system elements, two methods are offered: the cost optimization method and the fuzzy Analytic Hierarchy Process (AHP) method. In the former method, a new model of system maintenance cost is offered. This model, based on system outage information, the elements maintenance costs are determined as functions of system reliability indices and preventive maintenance budget. The latter method, too, a new guideline is introduced for considering the cost and reliability criteria in the trend of preventive maintenance budget planning. In this method, the preventive maintenance budget for the elements is determined based on relative priority of elements with reliability criteria. © 2015 Wiley Periodicals, Inc. Complexity 21: 70–88, 2016     

Theoretical calculation and prediction for experimental design to obtain spin crossover complexes

DFT methods were utilized to study SCO complexes. [Fe(2btz)₂(NCX)₂] (2btz = 2,2′‐bithiazoline, X = S ( 1 ) and Se ( 2 )), [Fe(phen)₂(NCX)₂] (phen = 1,10‐phenantroline, X = S ( 3 ) and Se ( 4 )), and [Fe(bpy)₂(NCS)₂] ( 5 ) (bpy = 2,2′‐bipyridine) compounds, which have experimentally shown SCO behavior, were calculated. B3LYP, B3LYP*, OPBE, and OLYP with 6‐31G* and 6‐311 + G** basis sets were employed to calculate the ΔE_HS/LS energy gap as a clue to find complexes with SCO behavior. It is found that calculated result by B3LYP* with c₃ = 0.14 and OPBE methods and 6‐31G* basis set are in agreement with experimentally observed SCO complexes. Then, newly designed Fe(N‐N)₂(X)₂ complexes, where N‐N are bidentate nitrogen donor chelating ligands and X= SCN^‐, SeCN^‐, Cl^‐, Br^‐, I^‐, were chosen to see their potential to be SCO compounds. ΔE_HS/LS for potential SCO complexes are estimated from 0.8 to 6.5 kcal/mol in B3LYP* and 0.6–5.7 kcal/mol in OPBE. These calculations suggest [Fe(bpy)₂(NCSe)₂], [Fe(5dmbpy)₂(NCS)₂], and [Fe(3‐BrPhen)₂(NCSe)₂] compounds have the ability to show SCO behavior. © 2016 Wiley Periodicals, Inc.     

Development of an ultrasound‐assisted emulsification microextraction method for the determination of chlorpyrifos and organochlorine pesticide residues in honey samples using gas chromatography with mass spectrometry

A simple, rapid, and efficient ultrasound‐assisted emulsification microextraction method followed by gas chromatography mass spectrometry in selected ion monitoring mode was developed for the determination of organochlorine pesticides in honey samples. The type and volume of organic extraction solvent, pH, effect of added salt content, and centrifuging time and speed were investigated. Under the optimum extraction conditions, 30 μL of 1, 2‐dibromoethane (extraction solvent) was immersed into an ultrasonic bath for 1 min at 40°C. The limits of detection and quantification for all target pesticides were 0.003–0.06 and 0.01–0.2 ng/g_, respectively. The extraction recovery was 91–100% and the enrichment factors were 168–192. The relative standard deviation for the method was <6% for intraday (n = 6) and <8% for interday precision (n = 4). The proposed method was successfully applied for the analysis of organochlorine pesticides in honey samples.     

Antibacterial effect of the red sea soft coral Sarcophyton trocheliophorum

The marine soft corals Sarcophyton trocheliophorum crude extracts possessed antimicrobial activity towards pathogenic bacterial strains, i.e. Bacillus cereus, Salmonella typhi, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Bioassay-guided fractionation indicated that the antimicrobial effect was due to the presence of terpenoid bioactive derivatives. Further biological assays of the n-hexane fractions were carried out using turbidity assay, inhibition zone assay and minimum inhibitory concentration for investigating the growth-inhibition effect towards the Gram-positive and Gram-negative bacteria. The fractions were screened and the structure of the isolated compound was justified by interpretation of the spectroscopic data, mainly mass spectrometry (GC-MS). The structure was assigned as (5S)-3-[(3E,5S)-5-hydroxy-3-hepten-6-yn-1-yl]-5-methyl-2(5H)-furanone and was effective at concentrations as low as 0.20 mg/mL. The above findings, in the course of our ongoing research on marine products, may implicate that the profound anti-microbial activity of the S. trocheliophorum soft corals, inhabiting the red sea reefs, is attributed to the presence of growth-inhibiting secondary metabolites mainly terpenoids.     

Competitive immunoassay for Ochratoxin a based on FRET from quantum dot-labeled antibody to rhodamine-coated magnetic silica nanoparticles

We report on a highly sensitive competitive immunoassay for the mycotoxin Ochratoxin (OTA) using magnetic silica nanoparticles (NPs) fluorescently labeled with rhodamine 123 (Rho123) as signal intensifier. The method is based on the measurement of fluorescence resonance energy transfer (FRET) that occurs from CdTe quantum dots covered with anti-OTA antibody to the dye Rho123 on the surface of the NPs. The immunoreaction between anti-OTA antibody and OTA brings the fluorophore (acting as the acceptor) in close proximity of the QDs (acting as the donor), and this causes FRET to occur upon photo-excitation of the QDs. The size and polydispersity of the silica coated magnetic NPs was studied via TEM. The method has a detection limit of 0.8 pg of OTA per mL. It was applied to the determination of OTA in spiked human serum. A linear relationship is found between the increase in the fluorescence intensity of Rho 123 at 580 nm and the concentration of OTA in spiked samples over the 8 to 48 pg?mL^?1 concentration range. This highly sensitive homogeneous competitive detection scheme is simple, rapid and efficient. It does not require multiple separation steps and excessive washing.

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Graphical abstract Following photoexcitation of immobilized quantum dots (QDs), FRET occurs between the QDs and Rhodamine 123. The close proximity of Rho 123 and the magnetic silica core/shell particles leads to strongly intensified emission to result in an assay for Ochratoxin A that has a detection limit as low as 0.8 pg?mL^-1