Photo- and radiation-induced preparation of nanocrystalline copper and cuprous oxide catalysts

Spherical copper nanoparticles have been prepared by photo- or radiation-induced reduction of aqueous solutions containing 10⁻³ mol.dm⁻³ copper sulphate or formate, 1.3 mol.dm⁻³ propan-2-ol and polyvinyl alcohol as a stabilizer. Increase of initial copper concentration to 10⁻² mol.dm⁻³ resulted in formation of different reaction product—octahedral cuprous oxide nanoparticles. Solutions were irradiated by means of electron beam, ⁶⁰Co γ rays (dose rate 70 Gy.h⁻¹) or by 400 W medium-pressure mercury lamp and were characterised by UV-Vis spectrophotometry, X-Ray Powder Diffraction, TEM and SEM. Pink to violet colour of colloidal copper solutions corresponded to measured copper surface plasmon band at circa 580 nm and has been found to be very sensitive to oxygen, which causes dissolution of particles. Therefore, the influence of purging by nitrogen gas prior to irradiation was thoroughly examined and has been found to only hinder, not alter irradiation effects. Moreover, the evolution of absorption spectrum of colloidal copper solution in contact with air has been measured, revealing interesting non-monotonous dependence on the air exposure time, probably caused by formation of protective oxide layer. Catalytic activity of prepared cuprous oxide has been measured by catalytic decomposition of hydrogen peroxide and has been found to be higher or comparable to commercial cuprous oxide.     

Selective ion exchange separation of uranium from concomitant impurities in uranium materials and subsequent determination of the impurities by ICP-OES

An ion exchange method has been developed for the separation of uranium from trace level metallic impurities prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES) in uranium materials. Selective separation of uranium from trace level metallic impurities consisting Cr, Co, Cu, Fe, Mn, Cd, Gd, Dy, Ni, and Ca was achieved on anion exchange resin Dowex 1 × 8 in sulphate medium. The resin (100–200 mesh, in chloride form) was packed in a small Teflon column (7.8 cm × 0.8 cm I.D.) and brought into sulphate form by passing 0.2 N ammonium sulphate solution. Optimum experimental conditions including pH and concentration of sulphate in the liquid phase were investigated for the effective uptake of uranium by the column. Uranium was selectively retained on the column as anionic complex with sulphate, while impurities were passed through the column. Post column solution was collected and analyzed by ICP-OES for the determination of metallic impurities. Up to 2,500 μg/mL of uranium was retained with >99% efficiency after passing 25 mL sample through the column at pH 3. Percentage recoveries obtained for most of the metallic impurities were >95% with relative standard deviations <5%. The method established was applied for the determination of gadolinium in urania–gadolinia (UO₂–Gd₂O₃) ceramic nuclear fuel and excellent results were achieved. Solvent extraction method using tributylphosphate (TBP) as extractant was also applied for the separation of uranium in urania–gadolinia nuclear fuel samples prior to the determination of gadolinium by ICP-OES. The results obtained with the present method were found very comparable with those of the solvent extraction method.     

Role of the shape of various bacteria in their separation by Microthermal Field-Flow Fractionation

The steady-state movement of the spherical and non-spherical particles, such as prolate or oblate rotational ellipsoids, cylinders, or parallelepipeds, suspended in a liquid and exposed to a unidirectional temperature gradient, is analyzed theoretically. The differences in the ratios of the rotational to translational diffusion coefficients of the non-spherical to spherical particles, the heterogeneity of thermal conductivity of the particle body, and the heterogeneity in surface chemical nature make possible to separate the particles according to differences in shape. Preliminary experimental separations of Gram-positive and Gram-negative, nearly spherical and rod-shaped bacteria performed by Microthermal Field-Flow Fractionation confirmed that the fractionation of the cells according to differences in shape is possible.     

Determination of non-steroidal anti-inflammatory drugs in sewage sludge by direct hollow fiber supported liquid membrane extraction and liquid chromatography–mass spectrometry

In this study, a three-phase hollow fiber liquid-phase microextraction (HF-LPME) method combined with liquid chromatography–mass spectrometry was developed for direct determination of four non-steroidal anti-inflammatory drugs (ketoprofen, naproxen, diclofenac and ibuprofen) in sewage sludge. The drugs were extracted from non-spiked and spiked slurry samples with different amounts of sludge into an organic phase and then back-extracted into an aqueous phase held in the lumen of the hollow fiber. High enrichment factors ranging from 2761 to 3254 in pure water were achieved. In sludge samples, repeatability and inter-day precision were tested with relative standard deviation values between 10–18% and 7–15%, respectively. Average concentrations of 29 ± 9, 138 ± 2, 39 ± 5 and 122 ± 7 ng/g were determined in dried sludge from Källby sewage treatment plant (Sweden) for ketoprofen, naproxen, diclofenac and ibuprofen, respectively.     

Meta nitration of thiacalixarenes

Nitration of thiacalix[4]arene, immobilized in the 1,3-alternate conformation, leads regioselectively to meta-substituted products. Depending on the reaction conditions, mono- and dinitro-derivatives can be isolated in acceptable yields. This unique substitution pattern is inaccessible in classical calixarene chemistry, and yields inherently chiral compounds, which makes thiacalixarenes very attractive as building blocks or molecular scaffolds.     

Polynuclear Cu(II), Ni(II) and Cd(II) coordination compounds with bis(pyrimidin-2-yl)amine and dicyanamide

In this study the synthesis, crystal structure and characterization of three new transition metal polynuclear compounds with formula [Cu(dipm)(μ-dca)₂]_n(H₂O) (1), [Ni(dipm)(μ-dca)₂]_n(C₂H₆O)_1/2 (2) and [Cd(dipm)(μ-dca)₂]_n (3) (in which dipm = bis(pyrimidin-2-yl)amine and dca = dicyanamide) are reported. The isostructural compounds 1 and 2 contain a double-bridging end-to-end dca unit connecting two metal ions and a single bridging end-to-end dca unit between subsequent metals. Compound 3 exhibits only single bridging end-to-end dca units, oriented in three directions, giving rise to a 3D framework.     

Automatic convexity of rank-1 convex functions

We announce new structural properties of 1-homogeneous rank-1 convex integrands, and discuss some of their consequences.     

On the extent of star countable spaces

For a topological property P, we say that a space X is star Pif for every open cover Uof the space X there exists Y ? X such that St(Y,U) = X and Y has P. We consider star countable and star Lindelöf spaces establishing, among other things, that there exists first countable pseudocompact spaces which are not star Lindelöf. We also describe some classes of spaces in which star countability is equivalent to countable extent and show that a star countable space with a dense σ-compact subspace can have arbitrary extent. It is proved that for any ω ₁-monolithic compact space X, if C _p (X)is star countable then it is Lindelöf.     

Language specificity in the perception of voiceless sibilant fricatives in Japanese and English: implications for cross-language differences in speech-sound development

Both English and Japanese have two voiceless sibilant fricatives, an anterior fricative /s/ contrasting with a more posterior fricative /∫/. When children acquire sibilant fricatives, English children typically substitute [s] for /∫/, whereas Japanese children typically substitute [∫] for /s/. This study examined English- and Japanese-speaking adults' perception of children's productions of voiceless sibilant fricatives to investigate whether the apparent asymmetry in the acquisition of voiceless sibilant fricatives reported previously in the two languages was due in part to how adults perceive children's speech. The results of this study show that adult speakers of English and Japanese weighed acoustic parameters differently when identifying fricatives produced by children and that these differences explain, in part, the apparent cross-language asymmetry in fricative acquisition. This study shows that generalizations about universal and language-specific patterns in speech-sound development cannot be determined without considering all sources of variation including speech perception.     

Vocal tract changes caused by phonation into a tube: a case study using computer tomography and finite-element modeling

Phonation into a glass tube is a voice training and therapy method that leads to beneficial effects in voice production. It has not been known, however, what changes occur in the vocal tract during and after the phonation into a tube. This pilot study examined the vocal tract shape in a female subject before, during, and after phonation into a tube using computer tomography (CT). Three-dimensional finite-element models (FEMs) of the vocal tract were derived from the CT images and used to study changes in vocal tract input impedance. When phonating on vowel [a:] the data showed tightened velopharyngeal closure and enlarged cross-sectional areas of the oropharyngeal and oral cavities during and after the tube-phonation. FEM calculations revealed an increased input inertance of the vocal tract and an increased acoustic energy radiated out of the vocal tract after the tube-phonation. The results indicate that the phonation into a tube causes changes in the vocal tract which remain also when the tube is removed. These effects may help improving voice production in patients and voice professionals.