Synthesis,characterization and SEESR spectroscopic investigations of indole/aniline copolymers

Indole/aniline copolymers were synthesized electrochemically and the polymerization mechanism was investigated via in‐situ simultaneous electrochemical electron spin resonance (SEESR) spectroscopy. The Radical cationic intermediates of substituted indole and aniline were detected during the electrochemical oxidation. The resulting ESR‐spectra with hyperfine splitting were simulated and radicalic structures were identified. It was suggested that the polymerization occurs over positions C‐3 and C‐6 of indole molecule and over the nitrogen and para‐position of aniline. Furthermore, aniline, indole and aniline/indole copolymers were investigated depending on applied potential via electrochemical impedance spectroscopy (EIS). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Response of matrix chains to nanoscale filler particles

A new generation of on-lattice MC simulations for dense melts of coarse-grained POE chains has been developed so that the MC simulations include nanoscale filler particles. In this novel approach, filler particles and polymer chains are built from the same chemical structural building unit. Early simulations pointed an ambiguous behavior for the response of the matrix chains to the introduction of the nanoparticles. When the size of nanoparticles is comparable to that of matrix chains, or even smaller, a significant amount of chain expansion (for matrix chains) is always the case, which challenges the current theoretical considerations in this field. Our recent simulations show that the chain expansion behavior is not triggered by an artificially created “extra volume” effect. Furthermore, the relation between chain expansion behavior and a potential enhancement in the free volume is found to be irrelevant based on our analysis on the pair correlation and scattering functions.     

Critical evaluation of thermodynamics of complex formation of metal ions in aqueous solutions: VI. Hydrolysis and hydroxo-complexes of Zn at 298.15 K

The standard thermodynamic properties of Zn²⁺, its hydrolysis reactions and hydroxo-complex formation are critically evaluated on the basis of published experimental studies and specific interaction theory (SIT) for activity coefficient modelling. A set of thermodynamic data and interaction coefficients are recommended.     

Antimicrobial Activity of Lactoperoxidase System Incorporated into Cross-Linked Alginate Films

ABSTRACT:  In this study, the antimicrobial effect of lactoperoxidase (LPS) incorporated alginate films was investigated on Escherichia coli (NRRL B-3008), Listeria innocua (NRRL B-33314), and Pseudomonas fluorescens (NRRL B-253) in presence of different concentrations of H₂O₂ (0.2, 0.4, and 0.8 mM) and KSCN (1, 2, and 4 mM). The incorporation of 70 nmol ABTS/min/cm² LPS into alginate films gave 0.66 to 0.85 nmol ABTS/min/cm² enzyme activity at 0.2 to 0.8 mM H₂O₂ concentration range. The antimicrobial activity of LPS system on target bacteria changed according to the concentrations of KSCN and H₂O₂. The growth of all tested bacteria was prevented for a 6-h period by applying LPS system in presence of 0.4 or 0.8 mM H₂O₂ and 4 mM KSCN. At 0.8 mM H₂O₂ and 4 mM KSCN, the LPS system also inhibited growth of L. innocua and P. fluorescens for a 24-h incubation period, whereas E. coli growth could not be inhibited for 24 h under these conditions. At 0.2 mM H₂O₂ and 1 to 4 mM KSCN, a considerable inhibitory effect was obtained only on P. fluorescens . The decreasing order of the resistance of studied bacteria to LPS system is as follows: E. coli , L. innocua , and P. fluorescens . The developed antimicrobial system has a good potential for use in meat, poultry, and seafood since alginate coatings are already used in these products. Further studies are needed to test the LPS incorporated edible films in real food systems.     

A review of water flooding issues in the proton exchange membrane fuel cell

We have reviewed more than 100 references that are related to water management in proton exchange membrane (PEM) fuel cells, with a particular focus on the issue of water flooding, its diagnosis and mitigation. It was found that extensive work has been carried out on the issues of flooding during the last two decades, including prediction through numerical modeling, detection by experimental measurements, and mitigation through the design of cell components and manipulating the operating conditions. Two classes of strategies to mitigate flooding have been developed. The first is based on system design and engineering, which is often accompanied by significant parasitic power loss. The second class is based on membrane electrode assembly (MEA) design and engineering, and involves modifying the material and structural properties of the gas diffusion layer (GDL), cathode catalyst layer (CCL) and membrane to function in the presence of liquid water. In this review, several insightful directions are also suggested for future investigation.     

Nucleotide degradation and biogenic amine formation of wild white grouper (Epinephelus aeneus) stored in ice and at chill temperature (4 °C)

Sensory (cooked and uncooked), chemical (proximate composition, TVB-N, nucleotide degradation products and biogenic amines) and microbiological quality (TVC and total coliform) changes were investigated during storage of ungutted white grouper kept in ice and at chill temperature (4 °C). According to the sensory assessment, the shelf life of white grouper was 16 days in ice and 4 days for fish stored at chill temperature. TVB-N values increased with storage time. Amines found in white grouper stored in ice were TMA, putrescine, cadaverine, 2-phenylethylamine, dopamine, agmatine, tryptamine and serotonin. Histamine, spermine, spermidine were never detected with either storage condition. The acceptability limit in terms of microbial count was exceeded at 8 days in ice and at 4 days for fish stored at chill temperature. Total coliform count was 2.8 log₁₀ cfu/ml at 1 day and reached 10⁵ cfu/ml for both storage conditions.     

The effect of nitrogen fertilization on tocopherols in rapeseed genotypes

Tocopherols (α-, β-, γ- and δ-tocopherol) are naturally occuring antioxidants in vegetable oils. In rapeseed oil, α- and γ-tocopherols are the predominant isomers, while δ-tocopherol contributes much lower amounts to the total tocopherol content. Enhanced tocopherol content in seeds appears favourable, and breeding for tocopherol content has become an increasingly important objective in winter oilseed rape. The main objectives of this research were to quantify the amount of tocopherols in a number of rapeseed varieties and to investigate the effect of nitrogen fertilization on tocopherol concentration in the seed. The field trials were carried out in 2004–2005 and 2005–2006 at Dardanos, Çanakkale on the Turkish West Coast (10 km south of the city centre) with 13 varieties, three replications and three nitrogen levels (N₀: 0 kg/ha, N₁: 130 kg/ha and N₂: 260 kg/ha). The trial used a randomized complete block design with 6 m² plots. Tocopherol analysis was done using an HPLC system. Significant differences were found among the varieties and between the nitrogen levels. The average total tocopherol concentration was 118.7 mg kg^?1 for N₁, 134.1 mg kg^?1 for N₂ and 133.6 mg kg^?1 for N₃ fertilization level. MDS analysis indicated a rough grouping of line versus hybrid varieties and suggested that hybrids require more breeding effort to reach the level of tocopherols existed in line varieties.     

Synthesis and in vitro antimicrobial characterization of Boron-PVA Electrospun nanofibers

Polyvinyl alcohol (PVA) electrospun nanofibers and boric acid (BA) complexes of these nanofibers were synthesized with and without using TritonX-100(TX-100) as a water soluble surfactant (PVA, PVA/BA, PVA/TX-100, PVA/TX-100/BA). The electrospun nanofibers were characterized by SEM, FTIR and TGA. Preliminary results showed that certain amount of boric acid decreased the number of Stapylococcus aureus from 6,8x10⁷(CFU/mL) to 3x10⁷(CFU/mL). In the preparation of polymer, boric acid was used as a crosslinker and antimicrobial agent whereas TX-100 was used as surfactant. The viscosity and conductivity measurements indicated that the BA increased viscosity but decreased conductivity. In contrast, TX-100 increased conductivity without considerable effect on viscosity, which affects the production and resulting nanofiber properties such as diameter and bead formation. The antimicrobial activities of the nanofibers were assayed in vitro by Gram-negative (E. coli) and Gram-positive(S. aureus) bacteria. It was observed that PVA/TX-100/BA showed better antibacterial activity against S.aureus bacteria compared to PVA and PVA/TX-100 nanofibers.     

Ceria-based nanocomposite with simultaneous proton and oxygen ion conductivity for low-temperature solid oxide fuel cells

The samarium doped ceria-carbonate (SDC/Na₂CO₃) nanocomposite systems have shown to be excellent electrolyte materials for low-temperature SOFCs, yet, the conduction mechanism is not well understood. In this study, a four-probe d.c. technique has been successfully employed to study the conduction behavior of proton and oxygen ion in SDC/Na₂CO₃ nanocomposite electrolyte. The results demonstrated that the SDC/Na₂CO₃ nanocomposite electrolyte possesses unique simultaneous proton and oxygen ion conduction property, with the proton conductivity 1-2 orders of magnitude higher than the oxygen ion conductivity in the temperature range of 200-600 °C, indicating the proton conduction in the nanocomposite mainly accounts for the enhanced total ionic conductivity. It is suggested that the interface in composite electrolyte supplies high conductive path for proton, while oxygen ions are probably transported by the SDC grain interiors. An empirical “Swing Model” has been proposed as a possible mechanism of superior proton conduction.     

Numerical investigation of heat transfer and pressure drop in enhanced tubes

This study investigates passive heat transfer enhancement techniques to determine the distribution of temperature and static pressure in test tubes, the friction factor, the heat flux, the temperature difference between the inlet and outlet fluid temperatures, the pressure drop penalty and the numerical convective heat transfer coefficient, and then compares the results to the experimental data of Zdaniuk et al. It predicts the single-phase friction factors for the smooth and enhanced tubes by means of the empirical correlations of Blasius and Zdaniuk et al. This study performed calculations on a smooth tube and two helically finned tubes with different geometric parameters also used in the analyses of Zdaniuk et al. It also performed calculations on two corrugated tubes in the simulation study. In Zdaniuk et al.'s experimental setup, the horizontal test section was a 2.74 m long countercurrent flow double tube heat exchanger with the fluid of water flowing in the inner copper tube (15.57–15.64 mm i.d.) and cooling water flowing in the annulus (31.75 mm i.d.). Their test runs were performed at a temperature around 20 °C for cold water flowing in the annulus while Reynolds numbers ranged from 12,000 to 57,000 for the water flowing in the inner tube. A single-phase numerical model having three-dimensional equations is employed with either constant or temperature dependent properties to study the hydrodynamics and thermal behaviors of the flow. The temperature contours are presented for inlet, outlet and fully developed regions of the tube. The variations of the fluid temperature and static pressure along tube length are shown in the paper. The results obtained from a numerical analysis for the helically tubes were validated by various friction factor correlations, such as those found by Blasius and Zdaniuk et al. Then, numerical results were obtained for the two corrugated tubes as a simulation study. The present study found that the average deviation is less than 5% for the friction factors obtained by the Fluent CFD program while Blasius's correlation has the average deviation of less than 10%. The corrugated tubes have a higher heat transfer coefficient than smooth tubes but a lower coefficient than helically finned tubes. The paper also investigates the pressure drop penalty for the heat transfer enhancement.