Modified composite cation exchange membrane with enhanced stability and electrochemical performance

Journal of Solid State Electrochemistry - Herein, we elaborated on the feasibility of coupling polyvinyl chloride with tin aluminium molybdophosphate to form composite membranes that facilitate...     

Characterization of CuTe nanofilms grown by underpotential deposition based on an electrochemical codeposition technique

Journal of Solid State Electrochemistry - This study reports the synthesis of semiconductor CuTe nanofilms using underpotential deposition (UPD) technique based on the simultaneous,...     

Quantitative characterization of chemical degradation of heat‐treated wood surfaces during artificial weathering using XPS

The X‐ray photoelectron spectroscopy (XPS) study of three heat‐treated North American wood species (jack pine, birch and aspen) was carried out to evaluate chemical modifications occurring on the wood surface during artificial weathering for different times. The results suggest that the weathering reduces lignin content (aromatic rings) at the surface of heat‐treated wood, consequently, the carbohydrates content increases. This results in surfaces richer in cellulose and poorer in lignin. Heat‐treated wood surfaces become acidic due to weathering, and the acidity increases as the weathering time increases. Three possible reasons are given to account for the increase of acidity during weathering. The lignin content increases, whereas the hemicelluloses content decrease due to heat treatment. Heat‐treated woods have lower acidity to basicity ratios than the corresponding untreated woods for all three species because of the decrease in carboxylic acid functions mainly present in hemicelluloses. The wood composition changes induced by weathering are more significant compared to those induced by heat treatment at wood surface. Exposure to higher temperatures causes more degradation of hemicelluloses, and this characteristic is maintained during weathering. However, the wood direction has more effect on chemical composition modification during weathering compared to that of heat treatment temperature. The heat‐treated jack pine is affected most by weathering followed by heat‐treated aspen and birch. This is related to differences in content and structure of lignin of softwood and hardwood. The use of XPS technique has proved to be a reliable method for wood surface studies. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly Efficient Method Towards In Situ Immobilization of Invertase Using Cryogelation

A novel method was developed for the immobilization of Saccharomyces cerevisiae invertase within supermacroporous polyacrylamide cryogel and was used to produce invert sugar. First, the cross-linking of invertase with soluble polyglutaraldehyde (PGA) was carried out prior to immobilization in order to increase the bulkiness of invertase and thus preventing the leakage of the cross-linked enzyme after immobilization by entrapment. And then, in situ immobilization of PGA cross-linked invertase within cryogel synthesis was achieved by free radical polymerization in semi-frozen state. The method resulted in 100 % immobilization and 74 % activity yields. The immobilized invertase retained all the initial activity for 30 days and 30 batch reactions. Immobilization had no effect on optimum temperature and it was 60 °C for both free and immobilized enzyme. However, optimum pH was affected upon immobilization. Optimum pH values for free and immobilized enzyme were 4.5 and 5.0, respectively. The immobilized enzyme was more stable than the free enzyme at high pH and temperatures. The kinetic parameters for free and immobilized invertase were also determined. The newly developed method is simple yet effective and could be used for the immobilization of some other enzymes and microorganisms.     

A New Chemometric Strategy in Electrochemical Method Optimization for the Quantification of Cefdinir in Tablets,Effervescent Tablets and Suspension Samples

A new voltammetric method, based on the use of single‐use pencil graphite electrode, was developed for the quantitative determination of cefdinir by square wave voltammetry. Chemometric optimization strategy was used to select the suitable values for three experimental parameters (pH of the supporting electrolyte, frequency and square wave amplitude) by applying a 3³ full factorial design model. The optimal voltammetric conditions were found to be pH 5.0 for supporting electrolyte (Britton‐Robinson buffer), 43 mV for square wave amplitude and 108 Hz for frequency. Square wave voltammograms of calibration, validation and unknown samples were recorded between 0.0–1400 mV under the optimized voltammetric conditions. Linear regression equation was computed in the linear working range of 0.5–20 μg/mL by using the relationship between the concentration and peak current at 600 mV. The optimized voltammetric method was validated by assessing the analysis results of validation samples. Then the proposed method was applied for the quantitative determination of cefdinir in three different pharmaceutical preparations, namely film‐coated tablets, effervescent tablets and powder for oral suspension. It was concluded that the proposed voltammetric method was suitable for the quantitative analysis of commercial pharmaceutical preparations containing cefdinir.     

Intrinsic Surface‐Drying Properties of Bioadhesive Proteins

Sessile marine mussels must “dry” underwater surfaces before adhering to them. Synthetic adhesives have yet to overcome this fundamental challenge. Previous studies of bioinspired adhesion have largely been performed under applied compressive forces, but such studies are poor predictors of the ability of an adhesive to spontaneously penetrate surface hydration layers. In a force‐free approach to measuring molecular‐level interaction through surface‐water diffusivity, different mussel foot proteins were found to have different abilities to evict hydration layers from surfaces—a necessary step for adsorption and adhesion. It was anticipated that DOPA would mediate dehydration owing to its efficacy in bioinspired wet adhesion. Instead, hydrophobic side chains were found to be a critical component for protein–surface intimacy. This direct measurement of interfacial water dynamics during force‐free adsorptive interactions at solid surfaces offers guidance for the engineering of wet adhesives and coatings.     

Portfolio optimization for a large investor under partial information and price impact

This paper studies portfolio optimization problems in a market with partial information and price impact. We consider a large investor with an objective of expected utility maximization from terminal wealth. The drift of the underlying price process is modeled as a diffusion affected by a continuous-time Markov chain and the actions of the large investor. Using the stochastic filtering theory, we reduce the optimal control problem under partial information to the one with complete observation. For logarithmic and power utility cases we solve the utility maximization problem explicitly and we obtain optimal investment strategies in the feedback form. We compare the value functions to those for the case without price impact in Bäuerle and Rieder (IEEE Trans Autom Control 49(3):442–447, 2004) and Bäuerle and Rieder (J Appl Prob 362–378, 2005). It turns out that the investor would be better off due to the presence of a price impact both in complete-information and partial-information settings. Moreover, the presence of the price impact results in a shift, which depends on the distance to final time and on the state of the filter, on the optimal control strategy.