The lead dioxide electrode

The recent literature dealing with the redox mechanism of the lead-acid cell positive electrode is reviewed. The basis electrochemistry of lead dioxide in its various polymorphic modifications and states of subdivision is considered in relation to the important aspects of electrode technology of which the major industrial application of the material is the conventional lead-acid cell. The proposed mechanism of the reduction (discharge) of lead dioxide in various acidic solutions are considered in relation to the present state of electrode kinetic theory. The reverse reaction by which lead dioxide is formed and the parasitic intrusion of the self discharge are dealt with as a precursor to the total cyclic process. It is concluded that in a number of respects the mechanisms proposed do not adequately represent the totality of the experimental observations. Such shortcomings are emphasized and extensions to present research are proposed.     

Void Nucleation and Growth in Dual-Phase Steel 600 during Uniaxial Tensile Testing

Commercial dual-phase (DP) steel in sheet form and comprised of ferrite, martensite, and bainite was subjected to uniaxial tension up to fracture. The damage characteristics were studied through extensive quantitative metallography and scanning electron microscope (SEM) observations of polished sections and fracture surfaces of failed specimens. The observed void nucleation mechanisms include nucleation at the martensite/ferrite interface or triple junction (most predominant), nucleation due to the cracking of martensite particles, and nucleation at the inclusions. The void characteristics in terms of area fraction, void density, void size ranges, and void orientations were analyzed as a function of thickness strain from various regions of the different uniaxial tensile test specimens taken to fracture. The damage analysis suggests that the void nucleation occurs during the entire deformation process with an almost constant rate and this rate reduces before fracture. A nucleation strain of 0.15 has been estimated for this material.     

Control of translation initiation: a model-based analysis from limited experimental data

We have built a detailed kinetic model of translation initiation in yeast and have used a novel approach to determine the flux controlling steps based on limited experimental data. An efficient parameter estimation method was adapted in order to fit the most uncertain parameters (rate constants) to in vivo measurements in yeast. However, it was found that there were many other sets of plausible parameter values that also gave a good fit of the model to the data. We therefore used random sampling of this uncertain parameter space to generate a large number of diverse fitted parameter sets. A compact characterization of these parameter sets was provided by considering flux control. In particular, we suggest that the rate of translation initiation is most strongly influenced by one of two reactions: either the guanine nucleotide exchange reaction involving initiation factors eIF2 and eIF2B or the assembly of the multifactor complex from its constituent protein/tRNA containing complexes. It is hoped that the approach presented in this paper will add to our understanding of translation initiation pathway and can be used to identify key system-level properties of other biochemical processes.     

Freeze-dried strawberry powder improves lipid profile and lipid peroxidation in women with metabolic syndrome: baseline and post intervention effects

Background  

Strawberry flavonoids are potent antioxidants and anti-inflammatory agents that have been shown to reduce cardiovascular disease risk factors in prospective cohort studies. Effects of strawberry supplementation on metabolic risk factors have not been studied in obese populations. We tested the hypothesis that freeze-dried strawberry powder (FSP) will lower fasting lipids and biomarkers of oxidative stress and inflammation at four weeks compared to baseline. We also tested the tolerability and safety of FSP in subjects with metabolic syndrome. FSP is a concentrated source of polyphenolic flavonoids, fiber and phytosterols.     

Creep and Creep Fracture in Hot-Pressed Alumina

The creep and creep fracture behavior of two hot-pressed aluminas are presented, for both flexural and tensile testing. Steady-state power-law creep is observed with a stress exponent of about 2 for each material. Three distinct fracture regimes are found. At high stress in flexure, fracture occurs by slow crack growth with a high stress dependence of the failure time. At intermediate stresses, in both flexure and tension, creep fracture occurs by multiple microcracking after modest strains. Failure times exhibit a modest stress dependence (stress exponent of 2.5 in tension and 3 in flexure), with a constant failure strain equal to 0.09. The failure times are considerably longer in flexure than in tension, because of the constraint imposed on crack growth by the bending geometry. We conclude that flexure cannot be used for creep lifetime assessment, even in simple, single-phase materials such as Al₂O₃. At low stresses, in tension, failure also exhibits a modest stress dependence but with a much higher failure strain. The material shows the onset of super-plastic behavior.     

The flow of non-Newtonian slurries through fixed and fluidised beds

Measurements have been taken of the flow rate, pressure drop and bed height characteristics when non-Newtonian slurries flow through fixed and fluidised beds of uniformly sized spherical particles.In the case of fixed beds, the pressure drop-flow rate data has been interpreted using the capillary model of a porous medium together with rheological data for the slurries obtained from a tubular viscometer. The resulting friction factor-Reynolds number relationship is

This correlation was used to satisfactorily predict the minimum fluidisation velocity for a given solid/liquid system by equating the pressure drop to the net weight per unit area of particles in the bed. However, the correlation was not adequate for the prediction of bed expansion in the fluidised state. For systems which have a Reynolds number at minimum fluidisation, Re′_mf′ less than 40 an effect of particle diameter to bed diameter was observed. For systems having Re′_mf >40 the velocity, υ, and voidage, ?, were related to their values at minimum fluidisation by

It is therefore clear that, in the fluidised state, the capillary model does not present an adequate basis for the prediction of bed expansion.     

Microstructural Evolution in Annealed and Crept Silicon Nitride

The microstructure of a commercial sintered silicon nitride has been examined in the as-sintered condition, after annealing to a stable microstructure in either air or argon, and after creep deformation. Both as-sintered material and material annealed to a stable microstructure were crept. Extensive analytical electron microscopy has been used to determine the composition of the intergranular material (amorphous and crystalline). The as-sintered material contains an amorphous intergranular phase which partially devitrifies upon exposure to high temperatures. The residual intergranular glass is homogeneous throughout the samples (even though different crystalline products form near the surface and in the center of samples annealed in air) and stable. Creep deformation does not affect the microstructural evolution. It is, however, responsible for internal strain and some cavitation in the material.     

The use of near infrared reflectance spectroscopy to identify the origin of oak shavings used in wine aging

Near infrared (NIR) reflectance spectroscopy combined with chemometrics was used to classify toasted and untoasted oak wood shavings sourced from two countries (France and USA). Oak wood shaving samples (n = 96) were scanned in the NIR region (680–2,500 nm) using a monochromator instrument operating in reflectance mode. Principal component analysis, partial least squares discriminant analysis (PLS-DA) and linear discriminant analysis (LDA) were used to classify the samples according to their country of origin and level of toasting. Full cross validation (leave-one-out) was used as the validation method when classification models were developed. Correct classification rates of 83, 87 and 100 % for samples sourced from USA, France and toasted treatment were obtained using PLS-DA. For LDA, correct classification rates of 80.4, 85 and 100 % were achieved for samples sourced from USA, France and toasted treatment, respectively. These results demonstrated the ability of NIR spectroscopy to discriminate between oak wood shavings sourced from two different countries and two levels of toasting.