Application of a Novel CO2 DC Thermal Plasma Torch Submerged in Aqueous Solution for Treatment of Dissolved Carboxylic Acid

Plasma Chemistry and Plasma Processing - A novel direct current (DC) plasma torch, operating with a gas mixture consisting of carbon dioxide and hydrocarbon (methane), has been adapted and used for...     

One‐Pot Synthesis of New 1,5‐Disubstituted Tetrazoles Bearing 2,2‐Bis(trimethylsilyl)ethenyl Groups via The Ugi Four‐Component Condensation Reaction Catalyzed by MgBr2·2Et2O

A simple one‐pot Ugi four‐component condensation reaction has been developed for the synthesis of tetrazoles bearing 2,2‐bis(trimethylsilyl)ethenyl groups from the synthesized 4‐[2,2‐bis(trimethylsilyl) ethenyl]benzaldehyde ( 1 ), various amines, isocyanides, and trimethylsilylazide at room temperature, without solvent, and in the presence of catalytic amounts of MgBr₂·2Et₂O as catalyst.     

Chemical constituents of Jordanian propolis

Seventeen compounds, including a new lanostane triterpenoid, 24(Z)-1β-3β-dihydroxyeupha-7,24-dien-26-oic acid, have been isolated from the methanolic extracts of two samples of Jordanian propolis collected from two different places with different dominant flora. The structures of the isolated compounds were elucidated by spectral methods including IR, UV, MS and 1- and 2-D NMR.     

Impact of concentration self-quenching on the charge generation yield of fullerene based donor-bridge-acceptor compounds in the solid state

A fullerene based Donor-Bridge-Acceptor (DBA) compound, incorporating a π-extended tetrathiafulvalene electron donor, is investigated with respect to its photophysics in solution versus solid state. Solid films of neat DBA are compared with blend films where the DBA compound is diluted in the inert, low dielectric, polymer poly(styrene). It is found that the moderate intermolecular electronic coupling and donor-acceptor separation (22 ?) in this case leads to the generation of more dissociated, intermolecular charges than a mixture of the donor and acceptor reference compounds. However, the increased intermolecular interactions in the solid state lead to the excited state of the fullerene suffering from concentration self-quenching. This is found to severely affect the charge generation yield in solid films. The impact of competing intra and intermolecular interactions in the solid state upon the film photophysics is analysed in terms of a kinetic model which includes both the effects of concentration self-quenching and the impact of film composition upon the dielectric stabilisation of charge separated states. We conclude that both concentration self-quenching and dielectric stabilisation are critical in determining the photophysics of the blend films, and discuss strategies based upon our observations to enhance the charge photogeneration properties of organic films and photovoltaic devices based upon DBA compounds.     

Equation of state and stability of the helium-hydrogen mixture at cryogenic temperature

The equation of state and the stability of the helium-molecular hydrogen mixture at cryogenic temperature up to moderate pressure are studied by means of current molecular physics methods and statistical mechanics perturbation theory. The phase separation, segregation and hetero-coordination are investigated by calculating the Gibbs energy depending on the mixture composition, pressure and temperature. Low temperature quantum effects are incorporated via cumulant approximations of the Wigner-Kirkwood expansion. The interaction between He and H₂ is determined by Double Yukawa potentials. The equation of state is derived from the hard sphere system by using the scaled particle theory. The behavior of the mixture over a wide range of pressure is explored with the excess Gibbs energy of mixing and the concentration fluctuations in the long wavelength limit. The theory is compared to cryogenic data and Monte-Carlo calculation predictions. Contrary to previous similar works, the present theory retrieves the main features of the mixture below 50 K, such as the critical point and the condensation-freezing curve, and is found to be usable well below 50 K. However, the method does not distinguish the liquid from the solid phase. The binary mixture is found to be unstable against species separation at low temperature and low pressure corresponding to very cold interstellar medium conditions, essentially because H₂ alone condenses at very low pressure and temperature, contrary to helium.     

Ionic Liquid Based Ultrasound-Assisted Emulsification Microextraction for Preconcentration of Phenol Using Central Composite Design

In this work, phenol reacted with 4-aminoantipyrine (4-AAP) reagent in presence of potassium hexacyanoferrate(III) and then was extracted using ultrasound-assisted emulsification microextraction via 1-hexyl-3-methyl imidazolium hexafluorophosphate as an environmentally friendly solvent. Effects of the main experimental variables were investigated and optimized by central composite design. Under the optimum conditions (pH 9.5, 100 mg/L 4-AAP, 100 μL of ionic liquid as extraction solvent, 0.2 g/L K₃Fe(CN)₆ and 0.2 M NH₄Cl) the dynamic linear range, limit of detection and relative standard deviation were obtained as 0.2?25 μg/L, 0.07 μg/L and 2.6%, respectively. Finally, the applicability of the proposed ultrasoundassisted emulsification microextraction was examined and very good results were obtained. The results confirmed the applicability of the proposed method as a versatile, low cost and sensitive preconcentration method for determination of very low concentrations of phenol in aqueous solutions.     

The prize collecting Steiner tree problem: models and Lagrangian dual optimization approaches

We propose a generalized version of the Prize Collecting Steiner Tree Problem (PCSTP), which offers a fundamental unifying model for several well-known -hard tree optimization problems. The PCSTP also arises naturally in a variety of network design applications including cable television and local access networks. We reformulate the PCSTP as a minimum spanning tree problem with additional packing and knapsack constraints and we explore various nondifferentiable optimization algorithms for solving its Lagrangian dual. We report computational results for nine variants of deflected subgradient strategies, the volume algorithm (VA), and the variable target value method used in conjunction with the VA and with a generalized Polyak–Kelley cutting plane technique. The performance of these approaches is also compared with an exact stabilized constraint generation procedure.     

Sonochemical syntheses of xanthene derivatives using zeolite-supported transition metal catalysts in aqueous media

An efficient green method for the syntheses of biologically active xanthene derivatives by use of zeolite-supported transition metal catalysts is described. A Fe-Cu/ZSM-5 heterogeneous catalyst has the highest activity in the one-pot syntheses with a wide range of aldehydes and cyclic 1,3-diketones, under ultrasonic irradiation in water at ambient temperatures. The three-component condensation in the presence of supported metal catalysts is operationally simple, requires no expensive or toxic reagents, and gives high yields in short reaction times.