Immobilized iron Schiff base histidine complexes on Al-MCM-41 and zeolite Y as catalyst for oxidation of cycloalkanes

Iron complexes of N-salicylidene-l-histidine with or without bipyridine ligand immobilized on Al-MCM-41 and zeolite Y designated as Fe(sal-l-his)(bipy)complex/Al-MCM-41 or Fe(sal-l-his)complex/Al-MCM-41 and Fe(sal-l-his)(bpy)complex/Y or Fe(sal-l-his)complex/Y respectively, were prepared and characterized by X-ray powder diffraction (XRD), FT-IR, N₂ adsorption/desorption and chemical analysis techniques. Fe(sal-l-his)/Al-MCM-41 and Fe(sal-l-his)(bipy)complex/Al-MCM-41 were found to successfully catalyze the oxidation of cyclohexane, methyl cyclohexane, cyclooctane and adamantane with H₂O₂. The oxidation results and promising catalytic behavior of Fe(sal-l-his)(bipy)complex/Al-MCM-41 for oxidation of cyclooctane with 90 % conversion and excellent selectivity toward the formation of cyclooctanone will be discussed in this presentation.     

Fabrication of GaN nanowires on porous GaN substrate by thermal evaporation

In this research, we used an inexpensive method to fabricate highly crystalline gallium nitride (GaN) nanowires (NWs) on porous GaN (PGaN) on a Si (1 1 1) wafer by thermal evaporation using commercial GaN powder using a combination of argon and nitrogen gas atmosphere without any catalyst. Microstructural studies using scanning electron microscopy and transmission electron microscope measurements revealed the role of porosity in the nucleation and alignment of the GaN NWs. The GaN NWs have diameters of 30–45 nm and lengths of around 1 μm. Further structural and optical characterizations were performed using high resolution X-ray diffraction, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. Results indicate that the NWs are of a single-crystal hexagonal GaN and have the growth direction of [0 0 0 1].     

Transient kinetics of n‐butane partial oxidation at elevated pressure

A transient Mars‐van Krevelen type kinetic model was developed for n‐butane partial oxidation over vanadyl pyrophosphate (VPP) catalyst. The model validity was verified over a relatively wide range of redox feed compositions as well as higher reactor pressure (410 kPa). Oxygen and n‐butane conversion increased with higher pressure while maleic anhydride (MA) selectivity decreased by as much as 20%. However, the overall MA yield was enhanced by up to 30%. High pressure maintains the catalyst in a higher oxidation state (as long as there is sufficient oxygen in the gas phase) and as a consequence, the catalytic activity is improved together with MA yield. High pressure also affects the redox reaction rates and activation energies. © 2012 Canadian Society for Chemical Engineering     

Catalytic effect of hydrogen chloride on the degradation of poly(vinyl chloride)

The distribution of polyenes which results from the chemical dehydrochlorination of poly(vinyl chloride) has been studied in dichloromethane (DCM) and tetrahydrofuran (THF) solvents. A higher percentage of longer polyenes is formed in DCM than in THF. On the addition of trifluoroacetic acid to DCM solutions of the polyenes, new species are formed with strong absorptions in the region 500–800 nm. The absorptions are probably due to polyenylic ions formed by protonation of the polyenes, and the interrelated changes in their intensities can be explained by the migration of short polyene sequences along the polymer chain with the formation of longer sequences. The species are extremely photosensitive and are bleached in a few seconds with light from a medium-pressure mercury lamp. The relevance of these experiments to the effect of HCl on the polyene distribution and on the rate of photocrosslinking is discussed.     

Investigation of the photocatalytic activity of magnesium-doped Viburnum Opulus-like nickel oxide microstructure under visible light irradiation

In this study, the Viburnum Opulus-like NiO microstructure was synthesized by doping with various levels of Mg (1, 2, 3, 7, and 13 wt%) with the hydrothermal method. The X-ray diffraction analysis showed the tensile lattice strain and dispersion of Mg dopants in prepared samples. The cubic phase was observed in NiO and NiO with 13 wt% Mg-doping and phase change to rhombohedral was appeared in 1–3 and 7 wt% Mg-doping samples. According to the Urbach energy value, lattice disorder was reduced in 1–3 wt% Mg-doping. The sample with 13 wt% Mg-doping exhibited 3.1 times higher Urbach energy value compared to NiO. The degradation efficiency of the Methylene blue was approximately 92.98% for Mg-doped NiO with 13 wt% Mg in 105?min due to the charge trapping by localized states and reduction of recombination of charges. The photoluminescence showed the efficient electron–hole separation for all Mg-doped samples. The excellent durability and recyclability of photocatalyst over four cycles are representing that this material has a potential application in water remediation.

     

A new PI-based optimal linear quadratic state-estimate tracker for discrete-time non-square non-minimum phase systems

A new proportional–integral (PI)-based optimal linear quadratic state-estimate tracker, derived using a proportional–integral–derivative (PID) filter-based frequency-domain shaping approach, is proposed in this paper for discrete-time non-square non-minimum phase multi-input-multi-output systems. Subsequently, a new integrated PID filter-shaped optimal PI state estimator is presented for the aforementioned systems, so that both the proposed state estimator and the state-estimate tracker are able to achieve satisfactory minimum phase-like tracking performance, for the case of arbitrary command inputs with significant variations at some isolated time instants.     

Fabrication and characterization of electrospun fibrous nanocomposite scaffolds based on poly(lactide‐co‐glycolide)/poly(vinyl alcohol) blends

Tissue engineering involves the fabrication of three‐dimensional scaffolds to support cellular in‐growth and proliferation. Ideally, the scaffolds should be similar to the native extracellular matrix (ECM). Electrospun polymer nanofibrous scaffolds are appropriate candidates for ECM mimetic materials since they mimic the nanoscale properties of ECM. Electrospun polymer nanocomposites based on poly(lactide‐co‐glycolide) (PLGA)/poly(vinyl alcohol) (PVA) and organically modified montmorillonite (OMMT) were prepared by a solution intercalation technique followed by electrospinning. The morphology of fibrous scaffolds based on these nanocomposites was investigated using scanning electron microscopy. The scaffolds showed highly porous structure within the nanofibres of diameters ranging from 400 to 700 nm. X‐ray diffractometry gave evidence of good dispersion of the OMMT in the blends with exfoliated morphology. Measurements of the water uptake and water contact angle of the fibrous scaffolds indicated significant improvement in the hydrophilicity of the scaffolds. Evaluations of the mechanical properties and unrestricted somatic stem cell culture of the electrospun fibrous nanocomposite scaffolds revealed that the PLGA90/PVA10/1.5% OMMT and PLGA90/PVA10/3% OMMT samples are the most useful from the tissue engineering application viewpoint. Copyright © 2010 Society of Chemical Industry     

Application of Ultrasound-Assisted Extraction Followed by Solid-Phase Extraction Followed by Dispersive Liquid-Liquid Microextraction for the Determination of Chloramphenicol in Chicken Meat

In the present study, a simple and efficient preconcentration method was developed using ultrasound-assisted extraction followed by solid-phase extraction followed by dispersive liquid-liquid microextraction for the extraction and determination of trace amount of chloramphenicol in chicken meat. The sample was extracted with acetonitrile and EDTA-McIlvaine buffer under ultrasonication, followed by solid-phase extraction and dispersive liquid-liquid microextraction. In order to obtain high extraction efficiency, the parameters affecting the proposed method were evaluated and optimized. Under the optimized conditions, the calibration curve was linear in the range of 0.3–200 μg kg^?1 with good linearity (r ² > 0.995). Finally, applicability of the proposed method was successfully confirmed by extraction and determination of the chloramphenicol in chicken meat samples. Comparing to the traditional methods, the proposed method exhibits high sensitivity and high preconcentration as well as good precision.     

Beam shaping assembly optimization of Linac based BNCT and in-phantom depth dose distribution analysis of brain tumors for verification of a beam model

A Linac source of epithermal neutrons for BNCT is proposed in this work. A series of simulations has been carried out using the Monte Carlo code MCNPX for the determination of the final composition and configuration of beam shaping assembly (BSA) to moderate the photoneutron spectrum from the hybrid target that was designed in our previous work. The suggested configuration for BSA included 10 cm iron, 30 cm magnesium fluorine and 10 cm polytetrafluoroethylene (PTFE) in a cylindrical geometry. Ni, Pb, Bi and borated polyethylene were chosen as the collimator, reflector, gamma and neutron shield, respectively. Epithermal, thermal and fast neutron fluxes in the suggested design were 8.19E8 n/cm² s, 2.14E5 n/cm² s, and 4.82E7 n/cm² s, respectively, while other IAEA parameters for BNCT facility design had been satisfied.In the next step, the calculated beam parameters were measured for a SNYDER phantom placed 10 cm from the exit of the beam shaping assembly (BSA). MCNP calculation showed that the advantage depth was 8.2 cm and the maximum therapeutic ratio was 5.05, if boron concentrations in the tumor and normal tissue were assumed to be 65 and 18 ppm, respectively. The maximum dose rate for normal tissue was 37.1 cGy/min.     

Incorporation of methacryloisobutyl POSS in bio-based copolymers by nitroxide mediated polymerization in organic solution and miniemulsion

In this study, nitroxide mediated polymerization of methacryloisobutyl POSS (POSSMA) and bio-sourced monomers: isobornyl methacrylate (IBOMA) and C13 methacrylate (C13MA, an alkyl methacrylate with an average chain length of 13 units) was conducted in solution (toluene) and miniemulsion. BlocBuilder-MA (with 10 mol% acrylonitrile [AN] controlling co-monomer, for the solvent-based system) and Dispolreg 007 (for the miniemulsion) were used as the alkoxyamine for initiation and controlling the polymerization. POSSMA/IBOMA/C13MA effective terpolymerization (having 10 mol% AN controlling co-monomer) with monomer conversion (X) <72% in toluene resulted in resins with M_n up to 21.3 kg mol⁻¹ and Ð < 1.67. Next, terpolymerizations were conducted in dispersed aqueous media to completely remove the organic solvent, resulting in polymers with M_n up to 46.7 kg mol⁻¹ and Ð < 1.65. The successful chain extension of poly(IBOMA/AN) with a mixture of POSSMA/C13MA/AN (M_n = 74.1 kg mol⁻¹ and Ð = 1.55) showed high chain-end fidelity, exemplified by a clear, monomodal shift in the GPC chromatogram from the macroinitiator. Finally, it was shown that the addition of 20 mol% POSSMA improved the decomposition temperature of bio-based polymers of IBOMA/C13MA by 15%.