Nafion effect on the lead dioxide electrodeposition kinetics

Electrodeposition of lead dioxide in the presence of Nafion in solution is described by a four-stage kinetic scheme. The limiting stage at low polarizations is that of the second-electron transfer, and at high polarizations, the stage of delivery of lead compounds to the electrode surface. Nafion adsorption at the oxide profoundly affects the process kinetics.     

Characterization of titanium dioxide nanoparticles dispersed in organic ligand solutions by using a diffusion-ordered spectroscopy-based strategy

Diffusion-ordered NMR spectroscopy (DOSY NMR) is presented as a tool for the determination of the diffusion coefficients of organic ligands in suspensions of titanium dioxide nanoparticles. The nanoparticles were prepared by a sol-gel process by hydrolysis and condensation reactions of titanium tetra-n-butoxide in the presence of pentane-2,4-dione (acacH: acetylacetone), as well as para-toluenesulfonic acid (pTsA) and n-butanol (nBuOH). NMR spectroscopic studies were performed in various deuterated solvents, on both dispersed xerosols and diluted sols. The bipolar-pulsed field gradient longitudinal eddy-current delay (LED) pulse sequence was used for data acquisition. The data were processed by inverse Laplace transformation (ILT), by using a maximum entropy algorithm, to afford 2D DOSY spectra. Different diffusion regimes for organic ligands in the bound and unbound states were successfully discriminated, more particularly in [D3]acetonitrile, thus allowing assessment of their interactions with the nanoparticles.     

The sensitivity of thermal-lens and phase-shift (interferometric) techniques in photothermal spectroscopy: A comparative study

The thermal-lens and phase-shift (interferometric) techniques of photothermal spectroscopy are studied theoretically for the coaxial and mutually orthogonal propagations of probing and pumping beams. Respective expressions for the amplitude of detected signals are derived for the case of the volume absorption of pumping radiation. The sensitivities of the two techniques are numerically analyzed for different parameter values. It is demonstrated that the phase technique offers higher sensitivity especially if the size of the region with a perturbed temperature field is much larger than the probing beam radius.     

Characteristics of the elastic strain of a Ge(111) surface under a mechanical load

Estimates are obtained for various components of the elastic strain in a Ge(111) surface layer under isotropic lateral tension. Agreement with the reversible components of surface thinning, derived from energy shifts in the volume and surface plasma peaks, suggests that the latter have an elastic character. It is conjectured that the anomalously high strain in a thin surface layer is due to the partially quasielastic variation of the relief of strained semiconductor surfaces. Fiz. Tverd. Tela (St. Petersburg) 41, 641–644 (April 1999)     

Internal friction in magnesium reinforced by short Al2O3 fibres after thermal cycling

This paper describes the influence of thermal cycling on the damping behaviour of composites with Mg matrix and two contents (26.0 and 34.1 vol.%) of Saffil short fibres. The composites were prepared by squeeze casting. The logarithmic decrement, as a characteristic of the process responsible for the damping behaviour, was measured after ten thermal cycles between room temperature and an upper temperature. The upper temperature was varied within the range from 100 to 450°C.The strain dependence of the logarithmic decrement can be divided into two regions. A region of strain amplitude independent damping at low strains is followed by a region with amplitude dependent damping at higher strains. The damping level in the strain amplitude independent region depends weakly on the upper temperature of the cycle whereas the values of the logarithmic decrement in the strain amplitude dependent region depend very sensitively on the upper temperature of cycles. The observed experimental data can be explained considering creation of new dislocations during thermal cycling following recovery processes at higher upper temperatures of the cycle.     

Long-service-life plasma arc torch

An arc plasma torch having a long service life is described. Its water-cooled copper electrodes are coated with a film of a nanostructured carbon material. Electron microscopy and Raman spectroscopy instrumental studies of the electrode coating showed that it consisted of the composite nanosized carbon material including largely single-walled and multi-walled carbon nanotubes and other carbon forms with a certain amount of copper atoms intercalated in the carbon matrix.     

Lagrangean relaxation based heuristics for lot sizing with setup times

We consider a lot sizing problem with setup times where the objective is to minimize the total inventory carrying cost only. The demand is dynamic over time and there is a single resource of limited capacity. We show that the approaches implemented in the literature for more general versions of the problem do not perform well in this case. We examine the Lagrangean relaxation (LR) of demand constraints in a strong reformulation of the problem. We then design a primal heuristic to generate upper bounds and combine it with the LR problem within a subgradient optimization procedure. We also develop a simple branch and bound heuristic to solve the problem. Computational results on test problems taken from the literature show that our relaxation procedure produces consistently better solutions than the previously developed heuristics in the literature.     

Photochemistry of 2-alkoxymethyl-5-methylphenacyl chloride and benzoate

Irradiation of 2-(alkoxymethyl)-5-methyl-alpha-chloroacetophenones (1a-c) and 2-(methoxymethyl)-5-methylphenacyl benzoate (1d) in dry, nonnucleophilic solvents afforded 3-alkoxy-6-methylindan-1-ones (3a-c) in very high chemical yields. 3-Methylisobenzofuran-1(3H)-one (2) was, however, isolated as a major photoproduct in the presence of trace amounts of water. Quenching experiments and laser flash spectroscopy revealed that the indanone derivatives 3 are formed by 1,5-hydrogen migration from the lowest triplet excited state of the acetophenones 1 and cyclization of the resulting photoenols. In contrast, production of the lactone 2 in wet solvents was found to result from two consecutive photochemical transformations. The photoenols produced by photolysis of 1a-c add water as a nucleophile to form 2-acetyl-4-methylbenzaldehyde (4), which is further converted to 2 via a second, singlet state photoenolization process. Exhaustive photolysis of 1a in methanol produced the acetal 2-(dimethoxymethyl)-5-methylacetophenone (7a) as the exclusive product. The remarkable selectivity of these photoreactions may well be useful in synthetic organic chemistry.     

Structural and Magnetic Characteristics of Nanogranular Co–Al2O3 Single- and Multilayer Films Formed by the Solid-State Synthesis

The results of structural and magnetic investigations of nanogranular Co–Al₂O₃ films formed from Co₃O₄/Al thin-film layered structures upon vacuum annealing are reported. The Co₃O₄/Al films have been obtained by sequential reactive magnetron sputtering of a metallic cobalt target in a medium consisting of the Ar + O₂ gas mixture and magnetron sputtering of an aluminum target in the pure argon atmosphere. It is shown that such a technique makes it possible to obtain nanogranular Co–Al₂O₃ single- and multilayer thin films with a well-controlled size of magnetic grains and their distribution over the film thickness.