Zinc polyoxometalate on activated carbon: an efficient catalyst for selective oxidation of alcohols with hydrogen peroxide

[PW₁₁ZnO₃₉]^5? was immobilized on activated carbon and characterized using Fourier transform infrared, X‐ray diffraction, Brunauer–Emmett–Teller and elemental analysis techniques. Effective oxidation of various alcohols with hydrogen peroxide was performed in the presence of this catalyst. Easy separation of the catalyst from the reaction mixture, cheapness, high activity and selectivity, stability as well as retained activity in subsequent catalytic cycles make this supported catalyst suitable for small‐scale synthesis. Copyright © 2015 John Wiley & Sons, Ltd.     

Rapid and efficient synthesis of 2-imidazolines and bis-imidazolines under ultrasonic irradiation

Rapid and efficient preparation of 2-imidazolines and bis-imidazolines by reaction of ethylenediamine with nitriles in the presence of catalytic amounts of sulfur under ultrasonic irradiation is reported. The advantages of this system are short reaction times, high yields and the ability to carry out large scale reactions.     

Passive control of the flow around a square cylinder using porous media

The passive control of bluff body flows using porous media is investigated by means of the penalization method. This method is used to create intermediate porous media between solid obstacles and the fluid in order to modify the boundary layer behaviour. The study covers a wide range of two‐dimensional flows from low transitional flow to fully established turbulence by direct numerical simulation of incompressible Navier–Stokes equations. A parametric study is performed to illustrate the effect of the porous layer permeability and thickness on the passive control. The numerical results reveal the ability of porous media to both regularize the flow and to reduce the drag forces up to 30%. Copyright © 2004 John Wiley & Sons, Ltd.     

A rapid and precise technique for measuring delta(13)C-CO(2) and delta(18)O-CO(2) ratios at ambient CO(2) concentrations for biological applications and the influence of container type and storage time on the sample isotope ratios

A simple modification to a commercially available gas chromatograph isotope ratio mass spectrometer (GC/IRMS) allows rapid and precise determination of the stable isotopes ((13)C and (18)O) of CO(2) at ambient CO(2) concentrations. A sample loop was inserted downstream of the GC injection port and used to introduce small volumes of air samples into the GC/IRMS. This procedure does not require a cryofocusing step and significantly reduces the analysis time. The precisions for delta(13)C and delta(18)O of CO(2) at ambient concentration were +/-0.164 and +/-0.247 per thousand, respectively. This modified GC/IRMS was used to test the effects of storage on the (18)O and (13)C isotopic ratios of CO(2) at ambient concentrations in four container types. On average, the change in the (13)C-CO(2) and (18)O-CO(2) ratios of samples after one week of storage in glass vials equipped with butyl rubber stoppers (Bellco Glass Inc.) were depleted by 0.12 and by 0.20 per thousand, respectively. The (13)C ratios in aluminum canisters (Scotty II and IV, Scott Specialty Gasses) after one month of storage were depleted, on average, by 0.73 and 2.04 per thousand, respectively, while the (18)O ratios were depleted by 0.38 and 1.20 per thousand for the Scotty II and IV, respectively. After a month of storage in electropolished containers (Summa canisters, Biospheric Research Corporation), the (13)C-CO(2) and (18)O-CO(2) ratios were depleted, on average, by 0.26 and enriched by 0.30 per thousand, respectively, close to the precision of measurements. Samples were collected at a mature hardwood forest for CO(2) concentration determination and isotopic analysis. A comparison of CO(2) concentrations determined with an infrared gas analyzer and from sample voltages, determined on the GC/IRMS concurrent with the isotopic analysis, indicated that CO(2) concentrations can be determined reliably with the GC/IRMS technique. The (13)C and (18)O ratios of nighttime ecosystem-respired CO(2), determined from the intercept of Keeling plots, were -26.11 per thousand (V-PDB) and -8.81 per thousand (V-PDB-CO(2)), respectively.     

Molecular dynamics study on the thermal conductivity and mechanical properties of boron doped graphene

We investigated the effects of boron atoms substitution on the thermal conductivity and mechanical properties of single-layer graphene using the non-equilibrium molecular dynamics (NEMD) simulations. By performing the uniaxial tension simulations, we observed that substituted boron atoms slightly decrease the elastic modulus and tensile strength of graphene. On the other hand, it was observed that only 0.75% concentration of boron atoms in graphene reduces the thermal conductivity of graphene by more than 60% and leads to vanishing chirality effect.     

Separation of Cd(II) and Ni(II) ions by supported liquid membrane using D2EHPA/M2EHPA as mobile carrier

The separation of Cd(II) and Ni(II) ions was studied in an aqueous sulphate medium using supported liquid membrane (SLM). D2EHPA/M2EHPA was used as a mobile carrier, microporous hydrophobic PTFE film was used as a solid support for the liquid membrane, and the strip phase was sulphuric acid. The effects of different parameters such as feed concentration, carrier concentration, feed phase pH, and strip phase pH on the separation factor and flux of Cd(II) and Ni(II) ions were studied. The optimum values obtained to achieve the maximum flux were 5.0 for feed pH, 40 vol. % for D2EHPA/M2EHPA concentration in the membrane phase, 0.5 for strip pH, and 0.012 mass % for feed concentration. Under these optimum conditions, the flux values of Cd(II) and Ni(II) were 15.7 × 10^?7 kg m^?2 s^?1 and 2.6 × 10^?7 kg m^?2 s^?1, respectively. The separation factors of Cd(II) over Ni(II) were studied under different experimental conditions. At a carrier concentration of 10 vol. % and feed concentration of 0.012 mass %, the maximum value of 185.1 was obtained for the separation factor of Cd(II) over Ni(II). After 24 h, the percentages of the extracted Cd(II) and Ni(II) were 83.3 % and 0.45 %, respectively.     

Computational-Based Approach for Predicting Porosity of Electrospun Nanofiber Mats Using Response Surface Methodology and Artificial Neural Network Methods

Comparative studies between response surface methodology (RSM) and artificial neural network (ANN) methods to find the effects of electrospinning parameters on the porosity of nanofiber mats is described. The four important electrospinning parameters studied included solution concentration (wt.%), applied voltage (kV), spinning distance (cm) and volume flow rate (mL/h). It was found that the applied voltage and solution concentration are the two critical parameters affecting the porosity of the nanofiber mats. The two approaches were compared for their modeling and optimization capabilities with the modeling capability of RSM showing superiority over ANN, having comparatively lower values of errors. The mean relative error for the RSM and ANN models were 1.97% and 2.62% and the root mean square errors (RMSE) were 1.50 and 1.95, respectively. The superiority of the RSM-based approach is due to its high prediction accuracy and the ability to compute the combined effects of the electrospinning factors on the porosity of the nanofiber mats.