Conventional- versus microwave-hydrothermal leaching of glass from sintered kaolinite to make porous mullite

A microwave-hydrothermal treatment with 1 and 5N-NaOH solution was used at 150°C and 190°C to dissolve excess silica glass and thus make porous mullite ceramics from a fired New Zealand kaolin honeycomb. The effect of microwave-hydrothermal (M-H) treatment time on the dissolution of the glass was examined and compared to the result of conventional-hydrothermal (C-H) treatment. As expected, the rate of the dissolution of glass was faster with M-H treatment compared to C-H treatment. The dissolution of 40–43% glass was almost complete after M-H treatment in 1N-NaOH for 6 hrs at 150°C, in¹N-NaOH for 3 hrs at 190°C, in⁵N-NaOH for 1.5 hrs at 150°C, and in 5N-NaOH for 35 minutes at 190°C. When the M-H treatment in 5N-NaOH solution at 190°C was more than 45 minutes, nonporous prismatic crystals were formed on the honeycomb and these crystals decreased the specific surface area. There were no changes in the morphology of mullite whiskers or in the structure of porous mullite body after M-H treatments in NaOH solutions compared to that of C-H treatment. The M-H treatment has been shown to be a rapid technique to prepare porous mullite ceramics from fired kaolin honey comb.     

Chemiluminescence of tryptophan enhanced by electrochemical energy

Electrochemiluminescence (ECL) was used to detect tryptophan in aqueous solutions in the presence of a brominating agent. Using platinum and glassy carbon electrodes, the ECL mechanism of tryptophan was studied. Tryptophan was oxidized at 0.78 V vs. sce in 0.1 M NaOH aqueous solution to the excited intermediate at a platinum electrode (0.44 V at a glassy carbon electrode). The intermediate was further oxidized and emitted light. The ECL signal was clearly observed when the applied potential was enough to oxidize the tryptophan. The ECL spectrum was measured, showing maximum emission peaks at 544 nm, 434 nm and 404 nm. Above 1.0 V, the brominating agent was oxidized which results in suppression of the ECL signal. A weak ECL signal was observed at an applied potential below 0.5 V, which indicates that this reaction is chemiluminescence (CL), enhanced by the applied potential. This method cannot be used for routine analysis because of the high detection limit of tryptophan (1.0 μmol), but can be used to obtain emission mechanism information.     

A diffusive badge sampler for volatile organic compounds in ambient air and determination using a thermal desorption-GC/MS system.

A sensitive personal badge sampler packed with Carbopack B for ambient levels of volatile organic compounds and an analytical system using a thermal desorption-preconcentration-GC/MS have been developed. The capacity of the new sampler was sufficient for an 8-h sampling period, and the analytical method was sensitive enough for the measurement of sub-ppb levels for a 2-h sampling period. The samplers were compared to diffusive samplers (OVM 3500) for typical environmental concentrations. There was a good correlation between the results obtained with the new samplers and the OVM samplers.     

Bonding in fabric-cement systems: Effects of fabrication methods

This paper compares the effects on the bond between fabric and cement matrix of three different processing methods: casting, pultrusion and vacuum condition. The fabrics included bonded glass mesh, woven polyvinylalcohol, and warp knitted weft insertion polypropylene. Pullout tests were performed to examine the bond between fabric and cement matrix. A microstructural analysis was conducted and correlated with pullout data. Improved bonding was obtained for fabric-cement composites produced with the pultrusion process, particularly for fabrics composed of multifilament yarns that have open junction points and no sizing to seal individual yarns. This improved bonding results from the impregnation of the fabric in the cement chamber during the pultrusion process, which filled the spaces between the filaments of the multifilament yarns.     

JAXA-GCF project - high-quality protein crystals grown under microgravity environment for better understanding of protein structure

Since 2003, Japan Aerospace Exploration Agency (JAXA, former NASDA) has been conducting a project on a semi-annual basis (JAXA-GCF) to obtain high-quality protein crystals in the microgravity environment using the Russian transportation system. For this project, protein samples were mostly provided by Japanese users for whom JAXA provided technical and clerical support for crystallization experiments in microgravity. For the project, JAXA has constructed a user-friendly support service for microgravity experiments and provided regular and frequent flight opportunities. To simplify and improve technological matters, JAXA devised a gel-tube method crystallization device, which is effective both in space and on ground, based on the counter-diffusion technique. JAXA also provided ground-based techniques for efficient preliminary optimization of crystallization conditions using a 1-dimensional simulation and for harvesting and cryoprotecting crystals before X-ray diffraction experiments. These improvements have significantly increased the success rate of obtaining useful results. In conclusion, JAXA has developed technologies for growing, in microgravity, high-quality protein crystals, which may diffract up to atomic resolution, for a better understanding of 3-dimensional protein structures through X-ray diffraction experiments.     

Effect of pH on the polarization behavior of Zr65Al7.5Ni10Cu17.5 amorphous alloy in a phosphate-buffered solution

The present study evaluates the effects of surface finishing and dissolved oxygen in phosphate buffered saline solution on the corrosion behavior of Zr₆₅Al_7.5Ni₁₀Cu_17.5 amorphous alloy for the application of the alloy to biomaterials. Non-polished and polished alloys were polarized in deaerated electrolyte, and the polished alloy was also polarized with various concentrations of dissolved oxygen. The surface of the alloy was characterized using X-ray photoelectron spectroscopy. The corrosion resistance of the alloy decreased with metallic nickel and hydroxide ion in surface oxide after polishing. The pitting corrosion resistance also decreased with the hydroxide ion after polishing. On the other hand, the pitting-corrosion resistance increased with aerating 4% O₂ because of the decrease of hydroxide ion and adsorbed phosphate ion in the surface oxide. However, oxygen above 4% O₂ prevented dissolution of nickel, causing the decrease of the pitting-corrosion resistance. When the pH was 2.2, the dissolved oxygen did not influence the pitting-corrosion resistance because of the increased solubility of the surface oxide.     

Variations in the composition of various acyl lipids,tocopherols and lignans in sesame seed oils roasted in a microwave oven

Seeds from various strains of cultivated Sesamum indicum Linn (colour of seeds: black, brown and white) were exposed to microwave roasting for 16 and 30min at a frequency of 2450 MHz and were studied not only for different acyl lipids and their fatty acid compositions, but also for the contribution of anti-oxidants to the oxidative stability of the oils. Lipids from all-seeded strains were comparable in their total fatty acid composition, with linoleic, oleic, stearic and palmitic acids as the major acids. The total lipids were isolated by thin-layer chromatography into the following five fractions: triacylglycerols (TAG), diacylglycerols, free fatty acids, polar lipids and steryl esters. The TAG were slightly and randomly hydrolysed by microwaves, but was still representing 900 g kg^?1 of the total lipids at 30min of roasting. Although burning and bitter tastes occurred at the time, the tocopherols and lignans still amounted to over 80% of the original level. The results suggested that the oxidative stability of the oils would probably be due to the synergism between endogenous antioxidants and browning substances produced during microwave roasting.