Zero-crossing second derivative spectrophotometry for simultaneous determination of palladium and nickel using 1-(2-pyridylazo)-2-naphthol in mixed micellar solutions

1-(2-Pyridylazo)-2-naphthol (PAN) has been used for the simultaneous determination of nickel and palladium at trace levels. PAN complexes of nickel and palladium in the pH 1.98 form red and green colored complexes, respectively, which are soluble in aqueous 4:1 Triton X-100 to sodium dodecylsulfate (SDS) micellar media with total detergent concentration of 3.2%. Under optimum conditions, calibration graphs for the simultaneous determination by second derivative spectrophotometry were obtained. Zero crossing second derivative spectrophotometry at 668 and 572 nm, respectively for palladium and nickel was used for the simultaneous determination. The method is able to determine palladium to nickel ratio 70:1 to 1:6 (Wt/Wt), accurately. Accuracy and reproducibility of the determination method on the known various amounts of palladium and nickel in their binary mixtures were tested. Effects of diverse ions on the determination of palladium and nickel to investigate selectivity of the method also were studied.     

Calculation of the ground‐state energy and studies of other properties of exotic helium atoms with the use of boundary conditions of wave function

The minimum energy and average distance between particles of doubly muonic helium atoms Heμμ (He²⁺ + 2μ ), are calculated with the use of a wave function that satisfies boundary conditions such as the behavior of the wave function when two particles are close to each other or far away from each other. In this wave function, the muon–muon correlation in doubly muonic helium atoms is described to arrive at the correct behavior for r₁₂ tending to zero and infinity. It is shown that the obtained results are very close to the values calculated by others. Finally, to confirm the method and results, calculated values are compared with a similar electronic system, and it is shown that the small differences in the energies of Heμμ and He are due to the reduced masses, as expected. In addition to being very simple, the proposed wave function provides relatively accurate values for the energy and expectation values of r²ⁿ, emphasizing the importance of the local properties of the wave functions. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Experimental investigation on thermal-hydraulic characteristics of a tube equipped with modified vortex-generator inserts

The heat transfer, pressure drop, and overall performance specification of a straight circular tube fitted with vortex-generator inserts are investigated experimentally. To modify the thermal-hydraulic performance, the longitudinal spacing of winglets is varied along the flow direction. The experiments are performed in the turbulent regime (7,470 ≤ Re ≤ 18,670). Good agreement is obtained when the results are compared and validated with previous correlations proposed for the plain tube. The results show that the use of vortex-generator inserts inside the tube yields a higher heat transfer coefficient and pressure drop than the plain tube, and these parameters augment with increasing the number of winglets. The effect of variation of longitudinal spacing of winglets along the vortex-generator inserts on the heat transfer coefficient is higher that the pressure drop. It is also detected that the variation of this parameter affects each arrangement of winglets exclusively.     

Preparation of magnetite/poly(styrene-divinylbenzene) nanoparticles for selective enrichment-determination of fenitrothion in environmental and biological samples

In the present study, a cross-linked nano-sized spherical magnetic poly(styrene-divinylbenzene) is synthesized and used as an adsorbent for enrichment-determination of fenitrothion. A miniemulsion polymerization procedure was used to prepare the adsorbent. The magnetic adsorbent was characterized by FT-IR, SEM and TEM. The prepared magnetic adsorbent nanoparticles were mixed with magnetite nanoparticles for faster and more efficient magnetic precipitation. The reduced fenitrothion was coupled with 3-methyl-2-benzothiazolinone hydrazone and then the blue colored complex was extracted. The blue derivative of fenitrothion was eluted by a 1 mL aliquot of 1-propanol prior to spectrophotometry at 571 nm. Beer's law was obeyed in the range of 2–230 ng mL⁻¹ of fenitrothion with relative standard deviation and recovery in the ranges of 0.9–5.1% and 97.2–100.0%, respectively. Selectivity of the method was evaluated, and the method was successfully applied to the determination of fenitrothion in various water, soil, urine and human plasma samples.     

An Effective and New Method for the Synthesis of Polysubstituted Imidazoles by the Use of CrCl3.6H2O as a Green and Reusable Catalyst: Synthasis of Some Novel Imidazole Derivatives

New, efficient and environmentally adapted synthesis of polysubstituted imidazoles in one‐pot is found. The multicomponent reaction of various aldehydes, benzil, aliphatic and aromatic primary amines and ammonium acetate under solvent‐free condition is explained. The highly efficient role of CrCl₃.6H₂O as catalyst in this synthesis was shown. By this advantage, several polysubstituted imidazoles as pharmaceutical important molecules can be prepared in high yield and high purity. This method is a very easy and a rapid reaction for the synthesis of imidazole derivatives. The crude products recrystallized to afford the crystalline pure products. Furthermore, catalyst exhibited remarkable reusable activity.     

Surface treatment of nano ZnO using 3,4,5,6-tetrabromo-N-(4-hydroxy-phenyl)-phthalamic acid as novel coupling agent for the preparation of poly(amide–imide)/ZnO nanocomposites

Technological developments during the last century have led to the use of materials that inhibit or resist the spread of fire, because modern world with the increase in electronic products presents a greater risk of fire dangers. In line with this goal, a novel modifier containing bromine elements with flame retardancy potential for the surface modification of ZnO nanoparticles was produced from the reaction between tetrabromophthalic anhydride and p-aminophenol. For the synthesis of nanocomposites (NCs), the modified ZnO was embedded in the poly(amide–imide) (PAI) matrix under ultrasonic conditions. Samples were characterized by Fourier transform infrared, thermogravimetric analysis (TGA), X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy and UV-visible (UV/Vis) techniques. TGA results indicated that the addition of modified ZnO into the PAI matrix increases in the thermal decomposition temperatures of the obtained NCs and that the UV/Vis absorbance of NCs was examined and displayed better UV-protection property than the pure PAI.     

Optical,mechanical, and thermal behavior of poly(vinyl alcohol) composite films embedded with biosafe and optically active poly(amide–imide)-ZnO quantum dot nanocomposite as a novel reinforcement

Poly(vinyl alcohol) (PVA), a polyhydroxy polymer, is the synthetic resin produced in the world due to the physical properties and complete biodegradability. This work tries to introduce novel reinforcement for PVA to improve properties without effect on its biocompatibility. The present investigation deals with the fabrication of new PVA/poly(amide–imide)-zinc oxide nanocomposites (PVA/PAI–ZnO NCs) with different PAI–ZnO loading by using ultrasound irradiation. At first, the surface of ZnO nanoparticles (NPs) was modified by biosafe diacid for the better dispersion of NPs and increasing possible interactions between NPs and PAI. Then, PAI–ZnO was used as filler in the PVA matrix. Surface morphology results were amazing. The TEM images and related histograms show a noticeable size decreasing of ZnO NPs from about 31 to 3 nm after preparation of NCs. Other analyses showed that the reinforcement of PAI–ZnO NC into the PVA matrix enhances mechanical and thermal properties of the PVA composites.     

Synthesis and Dynamic NMR Study of New Stable Ylides Derived from the Reaction of Triphenylphosphine,Dialkyl Acetylenedicarboxylates,and 5-ACYL Meldrum’s Acid

Abstract

Triphenylphosphine and dialkyl acetylenedicarboxylate react smoothly in the presence of 5-acyl Meldrum's acid in dichloromethane at room temperature and lead to synthesis of new stable ylide derivatives of dimethyl (5-acetyl-2,2-dimethyl-4,6-dioxo-1,3-dioxane-5-yl)-3-(triphenyl-λ⁵-phosphanylidene) succinate. Dynamic NMR study results of rotamers are reported and compared with the previous-related reports.