Use of a Reflectance Spectroscopy Accessory for Optical Characterization of ZnO-Bi(2)O(3)-TiO(2) Ceramics

The optical band-gap energy (E(g)) is an important feature of semiconductors which determines their applications in optoelectronics. Therefore, it is necessary to investigate the electronic states of ceramic ZnO and the effect of doped impurities under different processing conditions. E(g) of the ceramic ZnO + xBi(2)O(3) + xTiO(2), where x = 0.5 mol%, was determined using a UV-Vis spectrophotometer attached to a Reflectance Spectroscopy Accessory for powdered samples. The samples was prepared using the solid-state route and sintered at temperatures from 1140 to 1260 °C for 45 and 90 minutes. E(g) was observed to decrease with an increase of sintering temperature. XRD analysis indicated hexagonal ZnO and few small peaks of intergranular layers of secondary phases. The relative density of the sintered ceramics decreased and the average grain size increased with the increase of sintering temperature.     

Stability of PVDF hollow fibre membranes in sodium hydroxide aqueous solution

The stability of PVDF hollow fibre membranes in sodium hydroxide (NaOH) aqueous solutions were investigated in this study. PVDF hollow fibre membranes were prepared from each of the three commercial raw PVDF materials (Kynar 761, Solef 1015 and Solef 6010) from two major suppliers (Atofina Chemicals Inc., USA and Solvay, Belgium) for comparison purposes. The effect of NaOH concentration, treatment time and temperature on mechanical properties, thermal properties and crystalline structure of the PVDF hollow fibre membranes were investigated through mechanical strength measurement, surface area analysis, XRD, FTIR and DSC analyses. The obtained results indicate that the reaction between PVDF and NaOH was initiated even at low concentrations of NaOH and was aggravated with the extended treatment time, resulting in the decrease in mechanical strength and crystallinity of PVDF hollow fibre membranes. The reaction was accelerated and intensified by increasing the concentration of NaOH and/or treatment temperature. At 70 °C, the mechanical integrity of the PVDF membranes was completely destroyed in 4 wt% NaOH solution within 24 h or in 10 wt% NaOH solution within 8 h. The deterioration of stability in NaOH solutions is considered universal for all PVDF employed in this study, irrespective of the raw materials or the corresponding hollow fibre membranes.     

Effect of In Situ Polymerization of Styrene onto Natural Rubber on Adhesion Properties of Styrene-Natural Rubber (SNR) Adhesives

Styrene-based deproteinized natural rubber (SNR) latex was synthesized by in situ polymerization. Three pre-vulcanization systems [conventional-cured (CV), semi-efficient-cured (Semi-EV), and efficient-cured (EV)] were studied in terms of tensile and adhesion properties. Good tensile properties were observed for CV and EV SNR. The Semi-EV SNR showed the best adhesion properties based on the good anchorage performance in all substrate pairings (polystyrene–polystyrene, polystyrene–rubber, and rubber–rubber). The pH modification on SNR latex via KOH addition has beneficial effects of removing protein layers, resulting in more styrene grafting sites in the rubber molecules. Consequently, the tensile and adhesion properties of the SNR are improved as more styrene polymers are grafted onto the rubber matrix. Semi-EV SNR with pH 12 has superior adhesive performance; hence, it is suitable for use as a pressure-sensitive adhesive.     

New Statistical Concepts for Prediction Viscosity,Critical Temperature,and Critical Pressure of Homologous Hydrocarbon Series (C n H2n+2)

Abstract

A new model for prediction viscosity, critical temperature, and critical pressure for homologous hydrocarbon series C _n H_2n+2 as a function of carbon number only. The new model has a general formula: η or T _c or P = A ₁ C ^{A ₂} (2+2C) ^{A ₃} . This new model provides accurate and computationally reliable prediction for the corresponding properties (η, T _c , and P _c ) value.     

Design,fabrication and testing of a PMMA-based passive single-cell and a multi-cell stack micro-DMFC

A passive, air-breathing polymethyl methacrylate (PMMA) based single-cell and a multi-cell stack micro-direct methanol fuel cell (DMFC) with 1.0 cm² active area with a novel cathode plate structure and assembly layer are designed, fabricated and tested. The fuel cell is completely passive with no auxiliary device such as pump or fan. Oxygen is taken from the surrounding air, and the methanol solution is stored in a built-in reservoir. The performance of the single cell is tested with different methanol concentrations ranging from 1.0 M to 5.0 M, and the optimum performance is achieved by using methanol at a concentration of 4.0 M. A stack with 6 cells is fabricated and tested with the optimum methanol concentration of 4.0 M, and power levels produced by different catalyst loadings on the anode are compared. Besides, this study also considers the cost analysis of micro-DMFC. The combination of a catalyst loading of 3.0 mg cm⁻² Pt/Ru on the anode and 2.0 mg cm⁻² Pt on the cathode yield the highest power of 12.05 mW at 1.08 V and 11.2 mA. The total cost for the micro-DMFC in this study is only about USD 2 mW⁻¹.     

The composition of the extractives from unaffected and heartrot affected heartwood of Acacia mangium Willd

A. mangium has been studied by a successive extraction of the wood with a series of solvents with increasing polarity, followed by GC, GC/MS and DC studies of the fractions obtained. The study of the extractives of sound and affected wood with respect to yield and composition cannot explain the influence of the heartrot fungi on wood components in detail. Differences mainly have been found in the more polar fractions (acetone/water and ethanol/water, respectively). The content of lipophilic extractive constituents is with about 0.6–0.7% rather low and does not differ between sound and affected heartwood. The composition of the lipophilic extractives is not very different either.

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A. mangium wurde untersucht, wobei sukzessiv mit einer Reihe von L?sungsmitteln ansteigender Polarit?t extrahiert und die einzelnen Fraktionen mit Hilfe von GC, GC/MS und DC untersucht wurden. Die Untersuchung der Extrakte aus gesundem und befallenem Holz zeigte, da? Extraktausbeuten und Zusammensetzung den Einflu? des Pilzbefalls auf die Holzkomponenten nicht detailliert beschreiben K?nnen. Unterschied in Ausbeute und Zusammensetzung der Extrakte wurden haupts?chlich in den polaren Extraktfraktionen (Aceton/Wasser- und Ethanol/Wasser-Extrakte) gefunden. Der Gehalt an lipophilen Extraktbestandteilen ist mit etwa 0.6–0.7% eher niedrig, gesundes und befallenes Holz unterscheiden sich praktisch nicht. Auch die Zusammensetzung der lipophilen Extrakte ist kaum verschieden zwischen gesundem und befallenem Holz.

     

Increasing Resistant Starch Content in Fish Crackers Through Repetitive Cooking-Chilling Cycles

This work describes the effect of a repetitive cooking-chilling process on resistant starch content in crackers prepared from a mixture of fish and starch, which are popularly known in Malaysia as “keropok.” Three fish cracker formulations were prepared using tapioca, wheat, and sago starch. Up to four cycles of repetitive cooking-chilling increased the resistant starch content in all products; however, the hardness of chilled samples decreased, and their moisture content increased. For the fried samples, the texture became harder, the color turned darker, and linear expansion was reduced. The dried fish cracker samples prepared with sago starch yielded the highest resistant starch content. The results demonstrated that four cycles of repetitive cooking-chilling were able to enhance resistant starch in fish crackers.     

Reduced myofibroblast differentiation on femtosecond laser treated 316LS stainless steel

In-stent restenosis is a common complication after stent surgery which leads to a dangerous wall narrowing of a blood vessel. Laser assisted patterning is one of the effective methods to modify the stent surface to control cell–surface interactions which play a major role in the restenosis. In this current study, 316LS stainless steel substrates are structured by focusing a femtosecond laser beam down to a spot size of 50 μm. By altering the laser induced spot density three distinct surfaces (low density (LD), medium density (MD) and high density (HD)) were prepared. While such surfaces are composed of primary microstructures, due to fast melting and re-solidification by ultra-short laser pulses, nanofeatures are also observed as secondary structures. Following a detailed surface characterization (chemical and physical properties of the surface), we used a well-established co-culture assay of human microvascular endothelial cells and human fibroblasts to check the cell compatibility of the prepared surfaces. The surfaces were analyzed in terms of cell adherence, proliferation, cell morphology and the differentiation of the fibroblast into the myofibroblast, which is a process indicating a general fibrotic shift within a certain tissue. It is observed that myofibroblast proliferation decreases significantly on laser treated samples in comparison to non-treated ones. On the other hand endothelial cell proliferation is not affected by the surface topography which is composed of micro- and nanostructures. Such surfaces may be used to modify stent surfaces for prevention or at least reduction of restenosis.     

Estimation of Heat Capacity for Liquids

Abstract

Heat capacity of liquid in different temperatures are necessary in most engineering calculations. A general formula has been developed to calculate heat value of nonpolar or slightly polar compounds based on critical properties and molecular weight. This formula is a function of reduced temperature, critical temperature, critical pressure, molecular weight, and acentric factor. It is applied within a wide range of temperatures.