Formation of By‐products in Pure and Aqueous Acrylic Acid – Kinetic Measurements and Formation Mechanisms

During acrylic acid (AA) storage, a quality loss occurs due to the formation of by‐products such as diacrylic acid (DiAA), triacrylic acid (TriAA), and higher oligomers. This problem intensifies in the presence of water since the formation rate of oligomers increases and further by‐products such as 3‐hydroxypropionic acid (3‐HPA) and 3‐hydroxydiacrylic acid (3‐HDiAA) are formed. However, water is often essential during storage and transport to raise the flash point or reduce the melting point. In this work, the formation kinetics are investigated for all mentioned components in pure and aqueous AA. The formation mechanisms of 3‐HPA and 3‐HDiAA are assumed as acid‐catalyzed ester hydrolyses of DiAA or TriAA. The introduced reactions are modeled with the measured kinetic data in order to confirm the proposed reactions.     

Solving Einstein's equations on supercomputers

In 1916, Albert Einstein published his famous general theory of relativity, which contains the rules of gravity and provides the basis for modern theories of astrophysics and cosmology. For many years, physicists, astrophysicists and mathematicians have striven to develop techniques for unlocking the secrets contained in Einstein's theory of gravity; more recently, computational science research groups have added their expertise to the endeavor. Because the underlying scientific project provides such a demanding and rich system for computational science, techniques developed to solve Einstein's equations will apply immediately to a large family of scientific and engineering problems. The authors have developed a collaborative computational framework that allows remote monitoring and visualization of simulations, at the center of which lies a community code called Cactus. Many researchers in the general scientific computing community have already adopted Cactus, as have numerical relativists and astrophysicists. In June 1999, an international team of researchers at various sites ran some of the largest such simulations in numerical relativity yet undertaken, using a 256-processor SGI Origin 2000 supercomputer at the National Center for Supercomputing Applications (NCSA). Other globally distributed scientific teams are running visual simulations of Einstein's equations on the gravitational effects of colliding black holes     

Fast and intuitive generation of geometric shape transitions

We describe a novel method for continuously transforming two triangulated models of arbitrary topology into each other. Equal global topology for both objects is assumed. However, extensions for genus changes during metamorphosis are provided. The proposed method addresses the major challenge in 3D metamorphosis, namely, specifying the morphing process intuitively with minimal user interaction and sufficient detail. Corresponding regions and point features are interactively identified. These regions are parametrized automatically and consistently, providing a basis for smooth interpolation. Suitable 3D interaction techniques offer a simple and intuitive control over the whole morphing process.     

Low doses of eicosapentaenoic acid, docosahexaenoic acid, and hypolipidemic eicosapentaenoic acid derivatives have no effect on lipid peroxidation in plasma

It was of interest to investigate the influence of both high doses of eicosapentaenoic acid (EPA) and low doses of 2-or 3-methylated EPA on the antioxidant status, as they all cause hypolipidemia, but the dose required is quite different. We fed low doses (250 mg/d/kg body wt) of different EPA derivatives or high doses (1500 mg/d/kg body wt) of EPA and DHA to rats for 5 and 7 d, respectively. The most potent hypolipidemic EPA derivative, 2,2-dimethyl-EPA, did not change the malondialdehyde content in liver or plasma. Plasma vitamin E decreased only after supplementation of those EPA derivatives that caused the greatest increase in the fatty acyl-CoA oxidase activity. Fatty acyl-CoA oxidase activity increased after administration of both EPA and DHA at high doses. High doses of EPA and DHA decreased plasma vitamin E content, whereas only DHA elevated lipid peroxidation. In liver, however, both EPA and DHA increased lipid peroxidation, but the hepatic level of vitamin E was unchanged. The glutathione-requiring enzymes and the glutathione level were unaffected, and no significant changes in the activities of xanthine oxidase and superoxide dismutase were observed in either low-or high-dose experiments. In conclusion, increased peroxisomal β-oxidation in combination with high amounts of polyunsaturated fatty acids caused elevated lipid peroxidation. At low doses of polyunsaturated fatty acids, lipid peroxidation was unchanged, in spite of increased peroxisomal β-oxidation, indicating that polyunsaturation is the most important factor for lipid peroxidation.     

Comparison of in vitro degradation of temperate forages using the gas production and filter bag techniques

BACKGROUND: Two of the most promising in vitro techniques for dynamic forage evaluation are the gas production (GP) and filter bag (FB) techniques. To improve our understanding of how these techniques describe the dynamic degradation of forages, 20 temperate forage samples were analysed by each method at different time points during a 96 h incubation period. The results of the recordings were fitted to a biphasic Michaelis–Menten model describing the degradation of rapidly and slowly degrading forage fractions. RESULTS: GP and disappearance from the FB measurements were correlated at all time points from 6 to 96 h (R² = 0.27–0.74), except at the 24 h incubation point. When GP was transformed into organic matter degradation (OMD), there was an even stronger correlation (R² = 0.54–0.75) between the techniques at all intervals. Comparison of the parameters from the Michaelis–Menten model resulted in correlations (R² = 0.83) between the sizes of the estimated forage fractions, but not between parameter determining the rates of their degradation. CONCLUSIONS: Both the GP and FB techniques have the potential to estimate the degradation of individual feed fractions in forages. Further studies in which the in vitro parameters are evaluated against livestock data, are needed to confirm the findings of this study, however. Copyright © 2007 Society of Chemical Industry     

Calcium removal from industrial wastewater by bio‐catalytic CaCO3 precipitation

High concentrations of soluble calcium in industrial wastewater present problems due to the calcification of downstream processing. The current trend towards circuit closure and increased water re‐use will escalate this problem. We investigated ureolytic microbial carbonate precipitation as a novel process for removing excess calcium from industrial effluents. Two laboratory‐scale reactors, both with a hydraulic retention time of 8 h, were fed with 1.8 dm³ of anaerobic effluent (about 11 mM Ca²⁺) from a paper recycling plant. Both reactors were inoculated with pre‐cultivated calcareous sludge and the treatment reactor was additionally dosed with urea to a final concentration of 8.3 mM . Even though the anaerobic wastewater was saturated as such with respect to CaCO₃, urea addition and hydrolysis was shown to be a pre‐requisite for precipitation. Almost all (85–90% w/v) of the soluble calcium was precipitated as CaCO₃ and removed through sedimentation in the treatment reactor. This bio‐catalytic process presents an uncomplicated and efficient method for the removal of calcium from industrial wastewater. Copyright © 2003 Society of Chemical Industry     

Yield,characteristics and composition of banana juice extracted by the enzymatic and mechanical methods

A comparative study of the enzymatic and mechanical banana juice extraction methods and the respective juices produced was carried out using Kayinja bananas (ABB genotype) imported from Uganda. In the enzymatic extraction process, macerated ripe banana pulp was incubated with a commercial enzyme preparation (Pectinex Ultra SP‐L) at 50 °C for 2 h. In the mechanical extraction process the ripe banana pulp was mixed with stretched strips of polythene and worked with a dough mixer at room temperature for 20 min (on average) until the juice appeared. Significantly (p < 0.05) higher ‘pure’ juice yield (604 g kg^?1 pulp) was obtained with the enzymatic method than with the mechanical method (541 g kg^?1 pulp). However, adding water to the spent pulp from the mechanical process and extracting dilute juice improved the juice yield to 757 g kg^?1 pulp. The enzyme‐extracted juice had significantly (p < 0.05) higher soluble solids, titratable acidity, fructose, glucose, total nitrogen, density and mineral potassium. However, the mechanically extracted juice had significantly higher sucrose, pH and viscosity. Although the mechanical extraction process suffers from occasional juice extraction failures, it offers an opportunity to extract banana juice without excessive energy expenditure, and the juice produced is wholesome with a superior flavour to that produced by the enzymatic method. © 2002 Society of Chemical Industry