Sintering of Multilayered Porous Structures: Part I‐Constitutive Models

Theoretical analyses of shrinkage and distortion kinetics during sintering of bilayered porous structures are carried out. The developed modeling framework is based on the continuum theory of sintering; it enables the direct assessment of the cofiring process outcomes and of the impact of process controlling parameters. The derived “master sintering curve”‐type solutions are capable of describing and optimizing the generic sintering shrinkage and distortion kinetics for various material systems. The approach utilizes the material‐specific parameters, which define the relative kinetics of layer shrinkages such as the relative intensity of sintering, and employs the conversion between real and specific times of sintering. A novel methodology is also developed for the determination of the ratio of the shear viscosities of the layer's fully dense materials. This new technique enables the determination of all input parameters necessary for modeling sintering of bilayers using experimental techniques similar to optical dilatometry applied to each individual layer and to a symmetric trilayered porous structure based on the two‐layer materials utilized in the bilayered system. Examples of sintering different porous bilayered systems are presented to justify the capability of the model in predicting and optimizing sintering kinetics.     

Mechanistic modelling of kinetics and mass transfer for a solid–liquid system: Leaching of zinc with ferric iron

A systematic approach was developed to consider liquid–solid reactions with rough solid particles and shrinking particle model. The model is able to predict the reactivities of both non-porous and porous solid particles; the reaction order with respect to the solid material varies from zero (non-porous slab) to one (porous particle).As a model system, leaching of zinc sulphide (sphalerite) with ferric iron in an acidic environment was considered. The modelling was based on experimental data obtained in a batch reactor system, for which both conventional mixing and ultrasound was applied. Rival models based on plausible reaction mechanisms were derived and discriminated qualitatively and with regression analysis. The best model described the leaching reaction as a stepwise process, where ferric ions react with solid zinc sulphide in consecutive surface reaction steps. Shrinking particle model along with the surface roughness approach was used. The model predicts first order behaviour with respect to zinc sulphide, while the reaction order with respect to ferric iron varies from one to two as the reaction progresses. This is in accordance with experimental observations. The intrinsic kinetics, liquid–solid mass transfer and the effect of ultrasound were well described by the best kinetic model.     

Experimental and DEM study of segregation of ternary size particles in a blast furnace top bunker model

Size segregation of pellets in the top bunker (hopper) of a blast furnace is an important factor affecting the radial distribution of the charged burden and indirectly also the distribution of gas in the shaft and cohesive zone. This paper studies size segregation of ternary size pellets during the discharging process of a hopper model through experiments and simulations. The simulations, which are based on the discrete element method (DEM), are first validated using four experimental cases applying different bunker filling methods. The effects of various variables, such as fine mass fraction, particle friction coefficients, diameter ratio of fine to coarse and filling method (random, layered or industrial filling), as well as the interaction with wall (static and rolling friction) on the segregation are investigated. The results show that even though many factors affect the extent of segregation during the discharging process, the most important factors are the filling method, diameter ratio of fine to coarse, wall-particle static and rolling friction, interparticle rolling friction as well as mass fraction of fine particles. Reducing wall-particle rolling or static friction or the fraction of fine particles decreased the extent of size segregation.     

α-Dioxygenases (α-DOXs): Promising Biocatalysts for the Environmentally Friendly Production of Aroma Compounds

Fatty aldehydes (FALs) can be derived from fatty acids (FAs) and related compounds and are frequently used as flavors and fragrances. Although chemical methods have been conventionally used, their selective biotechnological production aiming at more efficient and eco-friendly synthetic routes is in demand. α-Dioxygenases (α-DOXs) are heme-dependent oxidative enzymes biologically involved in the initial step of plant FA α-oxidation during which molecular oxygen is incorporated into the C_α-position of a FA (C_n) to generate the intermediate FA hydroperoxide, which is subsequently converted into the shortened corresponding FAL (C_n-1). α-DOXs are promising biocatalysts for the flavor and fragrance industries, they do not require NAD(P)H as cofactors or redox partner proteins, and they have a broad substrate scope. Here, we highlight recent advances in the biocatalytic utilization of α-DOXs with emphasis on newly discovered cyanobacterial α-DOXs as well as analytical methods to measure α-DOX activity in vitro and in vivo.     

In vitro evolution of an antibody fragment population to find high-affinity hapten binders

Recently, we constructed a focused antibody library tailored to interact with haptens. High functionality of this library was demonstrated, as specific binders could be retrieved to a range of different haptens. In the current study we have developed a mutagenesis and selection strategy in order to further fine-tune the hapten binding properties of these antibody fragments. Testosterone was chosen as model antigen for the investigation. A population, rather than a single clone, originating from this focused library and enriched for testosterone binders, was subjected to random mutagenesis and different phage display selection strategies of various stringencies. These included consecutively lowering the antigen concentration and having, or not having, soluble hapten present during the phage capture and elution steps. The different selection procedures resulted in a considerable increase in apparent affinities for several of the selected populations, from which the highest affinity antibody isolated had a K(D) of 2 nM, corresponding to an approximately 200-fold affinity improvement compared with the best clone of the starting population. Importantly, the polyclonal nature of the starting material allowed for the identification of novel unrelated variants that differed in fine-specificity, demonstrating that this approach is valuable for exploring different parts of structure space.     

Volatiles from a Mite-Infested Spruce Clone and Their Effects on Pine Weevil Behavior

Induced responses by Norway spruce (Picea abies) seedlings to feeding damage by two mite species were studied by analyzing the volatiles emitted during infestation. Four specimens of a Norway spruce (Picea abies L.) clone were infested with mites of Nalepella sp., another four with Oligonychus ununguis, and four were kept mite-free as controls. After a year of infestation, spruce volatiles were collected, analyzed, and identified using SPME-GC-MS. In addition, enantiomers of chiral limonene and linalool were separated by two-dimensional GC. Methyl salicylate (MeSA), (-)-linalool, (E)-β-farnesene, and (E,E)-α-farnesene were the main volatiles induced by both species of mites, albeit in different proportions. The ability of the main compounds emitted by the mite-infested spruces to attract or repel the pine weevil, Hylobius abietis (L.), was tested. (E)-β-farnesene was found to be attractive in the absence of spruce odor, whereas methyl salicylate had a deterrent effect in combination with attractive spruce odor. The other tested compounds had no significant effects on the behavior of the weevils.     

Ammonia synthesis over multi‐promoted iron catalysts obtained by high‐energy ball‐milling

The feasibility of producing ammonia synthesis catalysts from highenergy ballmilling of a simple mixture of the constituent oxides has been investigated. The effect of ballmilling the fused oxidic precursor of the industrial KM1 ammonia synthesis catalyst has also been studied. The results show that highenergy ballmilling offers some interesting possibilities for preparing novel catalytic materials. It is observed that ballmilling of the powder oxides mixture leads to formation of solid solutions and the catalytic activity is significantly higher than that of the starting material. Furthermore, ballmilling of fused oxidic KM1 precursor is seen to give rise to more homogeneous promoter distribution and slightly higher activity. The quite small activity increase observed in this case probably reflects the fact that the fusion process has already resulted in a close to optimal promoter distribution. The choice of atmosphere during ballmilling is also seen to offer possibilities for regulating the phase composition.     

Naive empiricism and dogmatism in confidence research: A critical examination of the hard–easy effect.

Two robust phenomena in research on confidence in one's general knowledge are the overconfidence phenomenon and the hard-easy effect. In this article, the authors propose that the hard-easy effect has been interpreted with insufficient attention to the scale-end effects, the linear dependency, and the regression effects in data and that the continued adherence to the idea of a "cognitive overconfidence bias" is mediated by selective attention to particular data sets. A quantitative review of studies with 2-alternative general knowledge items demonstrates that, contrary to widespread belief, there is (a) very little support for a cognitive-processing bias in these data; (b) a difference between representative and selected item samples that is not reducible to the difference in difficulty; and (c) near elimination of the hard-easy effect when there is control for scale-end effects and linear dependency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Model prediction for ranking lead-acid batteries according to expected lifetime in renewable energy systems and autonomous power-supply systems

Predicting the lifetime of lead-acid batteries in applications with irregular operating conditions such as partial state-of-charge cycling, varying depth-of-discharge and different times between full charging is known as a difficult task. Experimental investigations in the laboratory are difficult because each application has its own specific operation profile. Therefore, an experimental investigation is necessary for each application and, moreover, for each operation strategy.     

Electrodialytic remediation of copper mine tailings with sinusoidal electric field

In this work an electrodialytic remediation cell for copper mine tailings using sinusoidal electric field was analyzed, in order to increase the removal efficiency. The sinusoidal electric field was obtained by applying simultaneously continuous-alternating voltages; in this work an alternating voltage of low frequency was applied. The system was tested considering the effect of: (1) the effective voltage applied to the cell, (2) the period for the alternating voltage, (3) remediation time, and (4) copper complexing capacity of citric acid. According to the conditions studied in this investigation, the laboratory results showed that decreasing the effective voltage improves the remediation action, due to polarity reversal of the system, which reduces polarization during the process, but in terms of the period for the alternating voltage there is no effect. As expected the remediation time and copper complexing capacity of citric acid improves the amount of remediated material and the remediation action in general.