Enhancement of sensitivity of glucose sensors from alizarin–boronic acid adducts in aqueous micelles

The sensitivity of glucose sensors fabricated from alizarin–boronic acid adducts was improved by an assistance of surfactants. Basically, Alizarin Red S (ARS) is not a fluorescence active compound. However, the fluorescence emission can be observed when forming an adduct with 2-formylphenyl boronic acid (2-FPBA). Using displacement strategy, the fluorescence intensity of the ARS/2-FPBA adduct decreased as a linear function of the glucose concentration. A simple and sensitive method was developed by incorporating the ARS/2-FPBA adduct in the hydrophobic core of micelles. Various parameters that could possibly affect the fluorescence quenching ability including solution pH, concentration of 2-FPBA, types of surfactants and concentrations of surfactants were investigated. The optimum condition for the determination of glucose by the proposed assay was 2 mM cetyltrimethylammonium bromide (CTAB) in 0.05 M phosphate buffer pH 7.0. The fluorescence intensity of the ARS/2-FPBA adduct in the presence of CTAB was remarkably 13 times higher than that in the buffer solution. Moreover, the linear working concentration range was found to be 1.2–80 mM, and the calibration sensitivity was 14 times higher than that from the system containing only buffer solution.     

Influence of process parameters on SAC305 lead-free solder powder produced by centrifugal atomization

In the present work, a centrifugal atomizer was constructed in order to study the effects of operating parameters: rotating speed, melt feed rate, shape and size of atomizer, and oxygen content in the atomizer chamber, on the characters of SAC305 powder. It was evidenced from the experimental results that the median size of the atomized powders became smaller with increasing rotating speed, decreasing melt feed rate, and the use of larger atomizer. At same operating conditions, a cup shaped atomizer was able to give approx. 11% finer powder compared to that from a flat-disk shaped one. Median particle size appeared to be smaller with decreasing oxygen content in the chamber. SEM micrographs revealed that SAC305 particles atomized under atmospheric condition were found to form various shapes: ligament, teardrop, flake, and irregular. The shape of powder particles tends to be rounder with decreasing oxygen content in the chamber. Fine particles of SAC305 powder (− 45 μm) containing oxygen less than 100 ppm could be synthesized by purging nitrogen gas into the atomizing chamber. Production yield of the SAC305 powder increased with increasing atomizer's rotating speed, lower melt feed rate, and larger atomizer.     

K-doped LaNiO3 perovskite for high-temperature water-gas shift of reformate gas: Role of potassium on suppressing methanation

LaNiO₃ perovskite has been successfully used as a catalyst precursor for high temperature water-gas shift (HT-WGS) reaction of reformate gas to produce additional hydrogen from the hydrocarbon reforming. The Ni⁰ nanoparticles with the particle size of ca. 21 nm obtained after reduction of LaNiO₃ perovskite can effectively suppress CO methanation during HT-WGS reaction using pure CO/H₂O gas. However, for HT-WGS reaction of reformate gas (including CO, H₂O, CO₂ and H₂), LaNiO₃ perovskite exhibits lower catalytic activity with significant CH₄ formation predominantly via CO₂ methanation. In this work, the CO₂ methanation during HT-WGS reaction of reformate gas was suppressed by the addition of potassium onto LaNiO₃ perovskite. This is due to the adsorption of H₂O on the potassium which is located at the interface between La₂O₃ and Ni⁰ nanoparticle (as deduced from XPS and HRTEM results) that forms stable KOH, blocking the methanation of CO₂ adsorbed on the La₂O₃ with H₂ adsorbed on the Ni⁰ nanoparticles. Moreover, the formation of stable KOH also promotes the formation of formate (HCOO) – a key intermediate for WGS reaction over the reduced LaNiO₃ perovskite – even at high reaction temperature by continuously supplying hydroxyl group to react with CO adsorbed on the Ni⁰ nanoparticle, which helps to maintain the catalytic activity for WGS reaction at high reaction temperature.     

Sustained-release from layered matrix system comprising chitosan and xanthan gum

Sustained-release tablets of propranolol HCl were prepared by direct compression using chitosan and xanthan gum as matrix materials. The effective prolongation of drug release in acidic environment was achieved for matrix containing chitosan together with xanthan gum which prolonged the drug release more extensive than that containing single polymer. Increasing lactose into matrix could adjust the drug release characteristic by enhancing the drug released. Component containing chitosan and xanthan gum at ratio 1:1 and lactose 75% w/w was selected for preparing the layered matrix by tabletting. Increasing the amount of matrix in barrier or in middle layer resulted in prolongation of drug release. From the investigation of drug release from one planar surface, the lag time for drug release through barrier layer was apparently longer as the amount of barrier was enhanced. Least square fitting the experimental dissolution data to the mathematical expressions (power law, first order, Higuchi's and zero order) was performed to study the drug release mechanism. Layering with polymeric matrix could prolong the drug release and could shift the release pattern approach to zero order. The drug release from chitosan-xanthan gum three-layer tablet was pH dependent due to the difference in charge density in different environmental pH. FT-IR and DSC studies exhibited the charge interaction between of NH₃⁺ of chitosan molecule and COO^- of acetate or pyruvate groups of xanthan gum molecule. The SEM images revealed the formation of the loose membranous but porous film that was due to the gel layer formed by the polymer relaxation upon absorption of dissolution medium. The decreased rate of polymer dissolution resulting from the decreased rate of solvent penetration was accompanied by a decrease in drug diffusion due to ionic interaction between chitosan and xanthan gum. This was suggested that the utilization of chitosan and xanthan gum could give rise to layered matrix tablet exhibiting sustained drug release.     

Evolution of competitive priorities towards performance improvement: a meta-analysis

Competitive priorities are critical operational dimensions that a business process must possess to satisfy its internal and external customers. The process of defining competitive priorities is evolving and changing over time according to a new business paradigm. Therefore, it is the right time to revisit the critical dimensions of competitive priority. The purpose of this study is threefold: (1) to identify and revise the critical dimensions of competitive priority; (2) to assess the quality of competitive priority measures across studies based on different criteria; (3) to confirm the relationship between several competitive priorities and organisational performance. The results show the different effects that competitive priorities have on organisational performance. Cost and quality priorities show evidence of strong effect size compared to the others.     

Sustained-release from Layered Matrix System Comprising Chitosan and Xanthan Gum

ABSTRACT

Sustained-release tablets of propranolol HCl were prepared by direct compression using chitosan and xanthan gum as matrix materials. The effective prolongation of drug release in acidic environment was achieved for matrix containing chitosan together with xanthan gum which prolonged the drug release more extensive than that containing single polymer. Increasing lactose into matrix could adjust the drug release characteristic by enhancing the drug released. Component containing chitosan and xanthan gum at ratio 1:1 and lactose 75% w/w was selected for preparing the layered matrix by tabletting. Increasing the amount of matrix in barrier or in middle layer resulted in prolongation of drug release. From the investigation of drug release from one planar surface, the lag time for drug release through barrier layer was apparently longer as the amount of barrier was enhanced. Least square fitting the experimental dissolution data to the mathematical expressions (power law, first order, Higuchi's and zero order) was performed to study the drug release mechanism. Layering with polymeric matrix could prolong the drug release and could shift the release pattern approach to zero order. The drug release from chitosan-xanthan gum three-layer tablet was pH dependent due to the difference in charge density in different environmental pH. FT-IR and DSC studies exhibited the charge interaction between of NH₃⁺ of chitosan molecule and COO^? of acetate or pyruvate groups of xanthan gum molecule. The SEM images revealed the formation of the loose membranous but porous film that was due to the gel layer formed by the polymer relaxation upon absorption of dissolution medium. The decreased rate of polymer dissolution resulting from the decreased rate of solvent penetration was accompanied by a decrease in drug diffusion due to ionic interaction between chitosan and xanthan gum. This was suggested that the utilization of chitosan and xanthan gum could give rise to layered matrix tablet exhibiting sustained drug release.     

Cellulose acetate electrospun fiber mats for controlled release of silymarin

In this research, the silymarin-loaded electrospun cellulose acetate (CA) fibers were prepared which containing silymarin in various amounts (i.e., 2.5-20 wt.% based on the weight of CA powder). Incorporation of silymarin in the neat CA solution did not affect the morphology of the resulting fibers, as both the neat and the silymarin-loaded CA fibers were smooth. The average diameters of silymarin-loaded CA fiber ranged between 550-900 nm. No presence of the silymarin aggregates of any kind was observed on the surfaces of these fibers, suggesting that the silymarin was encapsulated well within the fibers. These results were confirmed by lowering the glass transition temperature and the melting temperature of the silymarin-loaded electrospun CA fibers which is determined by DSC technique. The release characteristic of silymarin from the silymarin-loaded CA fiber mats was investigated by the total immersion in the solution of 1/1 phosphate buffer/methanol medium pH 7.4 at 37 degrees C. The silymarin release from the silymarin-loaded electrospun CA fiber mat is monotonously increased to reach the maximum value at 480 min. The maximum amount of silymarin released from these materials increases with the increasing of initial silymarin loading in the spinning CA solutions. Since no aggregation of silymarin was found on the surface of the silymarin-loaded fibers, the release of the silymarin from fiber mats was mainly by the diffusion.     

Co‐gasification of woody biomass and sewage sludge in a fixed‐bed downdraft gasifier

Experimental and numerical studies of cogasification of woody biomass and sewage sludge have been carried out. The gasification experiments were performed in a fixed‐bed downdraft gasifier and the experimental results show that 20 wt % dried sewage sludge in the feedstock was effectively gasified to generate producer gas comprising over 30 vol % of syngas with an average lower heating value of 4.5 MJ/Nm³. Further increasing sewage sludge content to 33 wt % leads to the blockage of gasifier, which is resulted from the formation of agglomerated ash. The numerical models were then developed to simulate the reactions taking place in four different zones of the gasifier (i.e., drying, pyrolysis, combustion, and reduction zones) and to predict the producer gas composition and cold gas efficiency. The deviation between the numerical and experimental results obtained was lower than 10%. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2508–2521, 2015     

New approach for evaluation of the antioxidant capacity based on scavenging DPPH free radical in micelle systems

A simple and sensitive method was developed to evaluate the antioxidant capacity using a 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) incorporated in surfactants. Parameters possibly affected the DPPH scavenging activity were investigated including the type of surfactant, concentration of surfactant, solution pH and concentration of buffer. The optimum micelle system for determining the antioxidant capacity was 2 mM CTAB in 0.1 M acetate buffer (pH 4.6). The IC₅₀ values of various antioxidants were calculated and compared to those prepared in methanol. Furthermore, the rate of the reaction between DPPH and antioxidants was investigated. The rate constants observed in the micelle system were significantly faster than those in methanol, and this allowed shorter analysis time. This method was validated through linearity, limit of detection and precision by comparing with conventional methanolic assay. The purposed method was applied to evaluate the antioxidant capacity from aqueous extracted plant samples with satisfactory results.     

Improvements of electromechanical properties of gelatin hydrogels by blending with nanowire polypyrrole: effects of electric field and temperature

Nanowire‐polypyrrole/gelatin hydrogels were fabricated by dispersion of nanowire‐polypyrrole into a gelatin aqueous solution followed by solvent casting. The electromechanical properties, thermal properties and deflection of pure gelatin hydrogel and nanowire‐polypyrrole/gelatin hydrogels were studied as functions of temperature, frequency and electric field strength. The 0.01%, 0.1%, 0.5%, 1% v/v nanowire‐polypyrrole/gelatin hydrogels and pure gelatin hydrogel possess storage modulus sensitivity values of 0.75, 1.04, 0.88, 0.99 and 0.46, respectively, at an electric field strength of 800 V mm^?1. The effect of temperature on the electromechanical properties of the pure gelatin hydrogel and nanowire‐polypyrrole/gelatin hydrogels was investigated between 30 and 80 °C; there are three regimes for the storage modulus behaviour. In deflection testing in a cantilever fixture, the dielectrophoresis force was determined and found to increase monotonically with electric field strength. The pure gelatin hydrogel shows the highest deflection angle and dielectrophoresis force at an electric field strength of 800 V mm^?1 relative to those of the nanowire‐polypyrrole/gelatin hydrogels. Copyright © 2012 Society of Chemical Industry