A Spectral Method for the Electrohydrodynamic Flow in a Circular Cylindrical Conduit

This paper presents a combination of the hybrid spectral collocation technique and the spectral homotopy analysis method(SHAM for short) for solving the nonlinear boundary value problem(BVP for short) for the electrohydrodynamic flow of a fluid in an ion drag configuration in a circular cylindrical conduit. The accuracy of the present solution is found to be in excellent agreement with the previously published solution. The authors use an averaged residual error to find the optimal convergence-control parameters. Comparisons are made between SHAM generated results, results from literature and Matlab ode45 generated results, and good agreement is observed.     

Microwave assisted preparation of efficient activated carbon from grapevine rhytidome for the removal of methyl violet from aqueous solution

Grapevine rhytidome (the outer layer of bark on trunk), as an abundant and low-cost precursor, was used to prepare granular activated carbon with high surface area for the removal of methyl violet from aqueous solution. Microwave heating source was used to reduce the treatment time and energy consumption. To optimize the preparation, the effects of the different parameters, such as phosphoric acid concentration, acid/precursor weight ratio, impregnation time, microwave power, radiation time, and oven heating time on the ability of the samples for removal of methyl violet were studied. The obtained activated carbon was characterized by N₂ adsorption/desorption, SAXS, TEM and SEM methods. The adsorption of methyl violet onto the activated carbon was studied from both equilibrium and kinetic point of view and the results were compared with the commercial granular activated carbon. The rate of adsorption onto the prepared activated carbon was faster than commercial activated carbon. Different kinetic models were used to analyze the experimental kinetic data. The obtained activated carbon showed higher adsorption capacity (more than twice) for the adsorption of methyl violet in comparison with the commercial one. The equilibrium data were analyzed using different isotherm models. Adsorption was found to be maximum in the pH range 7-9.     

On the specificity of the amide VI band for the secondary structure of proteins

In this work we analyzed the specificity of the amide VI band for different types of secondary structure elements in protein structures. This band involves the bending motion of the CO group of the peptide chain that is typically observed in the spectral region from 590 to 490 cm⁻¹. The infrared absorbance spectra of a set of polypeptide model compounds of well known secondary structure was obtained at defined pH, including poly (l-lysine), poly (l-tyrosine), poly (l-alanine) and poly (l-histidine). In addition spectra of membrane proteins from the respiratory chain, namely the NADH:ubiquinone oxidoreductase, the cytochrome c oxidase and its Cu_A fragment, the cytochrome bc₁ complex, a Rieske-type protein and in addition myoglobin, have been comparatively investigated. The systematic analysis of the amide VI band of the polypeptides and the proteins allowed correlating the signal appearing at ∼525 cm⁻¹ to α-helical structures and signals at ∼545 cm⁻¹ to β-sheet contributions. Random coils have been found to contribute at ∼535 cm⁻¹ while the β-turns were observed at ∼560 cm⁻¹.     

Structural and thermal properties of monolithic silica–phosphate (SiO<Subscript>2</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript>) gel glasses prepared by sol–gel technique

A sol–gel process for producing monolithic silica–phosphate (SiO₂–P₂O₅) system different concentrations of P₂O₅, starting with tetra-ethoxysilane TEOS, and triethyl-phosphate as sources of SiO₂ and P₂O₅ was performed. The gels were heat-treated at temperatures ranging from 100 up to 900 °C. The structural and chemical analyses of the samples were determined by using X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). It was found from the XRD that the existence of phosphorus enhances the crystallization of silica gel, while the FTIR indicated the main functional groups of silica–phosphate. It is important to study the effect of hydroxyl in silica–phosphate glass. The results obtained are promising to use the prepared samples in a variety of applications, ranging from traditional application such as lighting products) to the modern application (such as optical fibers. Optical studies were measured by using the spectrophotometer in wavelength range 0.2–2.5 μm. The refractive index (n) was calculated for the prepared samples, it was found to be strongly affected by structural rearrangement resulting from the elimination of the solvent and the Si–OH, Si–O–Si and Si–O–OH bonding by phosphate and aluminum and it increases by increasing phosphate concentrations. The weight losses have investigated for prepared samples.     

Preparation and characterization of nanocomposites in system as: SnO<Subscript>2</Subscript>–xTiO<Subscript>2</Subscript> (where <Emphasis Type="Italic">x</Emphasis> = 25, 50 and 75 mol%)

Nanocomposite samples containing various molar compositions of tin and titanium oxides were synthesized by a sol–gel method using octadecylamine as controlling template agent. The structural and the crystalline features of the samples were investigated with Fourier Transformer Infra-red, X-ray diffraction, Transmission electron microscope (TEM) where the surface area was estimated by BET analysis. The crystalline parameters and the particle size were estimated by Rietveld quantitative phase analysis. It is interesting to mention that a reduction in the lattice parameters was detected upon introduction of various molar compositions of titanium oxide revealing that a part of titania is incorporated into the SnO₂ lattice forming Ti_1−xSn_xO₂ solid solution. The quantitative analysis claims that part of titanium oxide is incorporated substitutionally in the crystal lattice of SnO₂, forming a solid solution and other parts are either segregated as separate rutile titania phase or dispersed as amorphous phase on the grain boundary of SnO₂. The results show a remarkable reduction in particle size from 42 to 5 nm and increasing in the specific surface area up to 176 m²/g upon introduction of various content of titania implying the role of titania particles in preventing SnO₂ crystallites from further growing up during the progress of calcination. TEM images show that pure tin oxide particles arranged in large aggregation in wormhole like structure, while the existence of titanium oxide are successfully creates spherical nanoparticles system organized in a definite structure. The optical absorbance spectra indicate a red shift and band gap narrowing upon introduction of titania which increase with increasing in titania contents.     

Mercury removal from aqueous solution by adsorption on?activated carbons prepared from olive stones

The textural characterization of a series of activated carbons prepared from olive stones, by carbonization at different temperatures (400, 550, 700 and 850 °C) and thermal activation with CO₂, has been investigated using N₂ adsorption at −196 °C and CO₂ adsorption at 0 °C. The effect of pre-oxidation of the carbonized precursor has also been studied, using temperature-programmed decomposition (TPD), to evaluate the effect of oxygen content of the chars in the performance of the obtained activated carbons for mercury removal. The adsorption of Hg(II) cations from aqueous solutions at room temperature by the prepared activated carbons was studied. Experimental results show that all samples exhibit a large microporosity (pore diameter below 0.56 nm). The amount of surface oxygen groups increased after pre-oxidation treatment, this enhancing the Hg(II) uptake (up to 72%). It can be concluded that these groups make the support more hydrophilic, thus providing a more efficient adsorption of Hg(II). The formation of a great amount of surface oxide groups such as carboxyl, phenol and lactone alters the surface charge properties of the carbon, this enhancing the surface-Hg(II) interaction.     

Selective solid phase extraction of platinum on an ion imprinted polymers for its electrothermal atomic absorption spectrometric determination in environmental samples

An ion-imprinted polymer (IIP) was obtained by copolymerization of methacrylic acid (as a functional monomer) and ethylene glycol dimethacrylate (as a crosslinking agent) in the presence of various chelators for Pt(II) ion and using 2,2??-azo-bis-isobutyronitrile as the initiator. Specifically, acetaldehyde thiosemicarbazone (AcTSn) and benzaldehyde thiosemicarbazone (BnTSn) were used as chelators. The IIPs were applied as sorbents for solid-phase extraction of Pt(II) and Pt(IV) ions from aqueous solutions. The effects of acidity and flow rate of the sample, of elution conditions and of potentially interfering ions were investigated. The imprinting effect of analyte is clearly demonstrated by the fact that only the IIP is capable of quantitative retention of Pt(II) and Pt(IV) ions. The method works best in the pH range from 0.5 to 1 and from 3.5 to 9.5. The ions can be recovered with an acidic solution of thiourea. The Pt-AcTSn polymer displays better sorption properties for the separation of analytes. The selectivity coefficients of the Pt-AcTSn and control polymers for Pt(IV) in the presence Pd(II), Rh(III), Ru(III), Al(III) and Cu(II) were calculated, and the sorbent capacity for Pt(IV) was found to be 4.56???g?g?^-1. The method was successfully applied to the determination of Pt(IV) by electrothermal atomic absorption spectrometry in tap water, tunnel dust and anode slime samples.

Synthesis and antimicrobial studies of bis(O,O′‐dialkyl and alkylene dithiophosphoric acid) adducts of diphenyl diselenide

Dialkyl and alkylene dithiophoshoric acids react with diphenyl diselenide in a 1:2 molar ratio in refluxing benzene to yield Ph₂Se₂·2HS₂P(OR)₂ (R = Et, Pr‐n, Pr‐i, Bu‐i and Ph) and , where G = ‐CH₂CMe₂CH₂‐, ‐CH₂CEt₂CH₂‐ and ‐CMe₂CMe₂‐. The complexes are yellow solids (in the cyclic chain) and yellow sticky solids (in the open chain), are soluble in common organic solvents and are monomeric in nature. They were characterized on the basis of elemental analyses, molecular weight determinations, IR and NMR (¹H, ¹³C and ³¹P). The spectral data revealed addition of dithiophosphate moieties to the diselenide. Studies were conducted to assess the growth‐inhibiting potential of some of the synthesized complexes against various bacterial strains. Copyright © 2011 John Wiley & Sons, Ltd.