Assessment on the mechanical,structural, and thermal attributes of green graphene-based water soluble polymer electrolyte composites

In the current study, graphene oxide (GO) was prepared using green chemistry with modified Hummer's method without incorporating sodium nitrate (NaNO₃). Solvent casting was employed to fabricate GO-doped poly(ethylene oxide) (PEO), that is, PEO/GO composites with various proportion of Na₂SO₄ and were then subjected to characterization via advanced spectroscopic techniques for different physicochemical aspects to estimate their potential applications as marketable products. XRD analysis explored that fabricated composites are more crystalline than neat PEO. PEO/GO/Na₂SO₄ composite films offered maximum crystallinity. SEM displayed the same trend. TG/DTA thermogram exposed better thermal stability than pristine polymer. FTIR studies confirmed complexation among hybrid's components. Elongation-at-break and Young's modulus displayed an enhancing behavior with an incremental loading of salt and filler. In terms of mechanical performance, composite of PEO with 0.37 wt % GO and 0.08 g salt was found to be an ideal composition during the course of study. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48376.     

Isolation and identification of lipase producing thermophilic Geobacillus sp. SBS-4S: cloning and characterization of the lipase

A thermophilic microorganism, SBS-4S, was isolated from a hot spring located in Gilgit, Northern Areas of Pakistan. It was found to be an aerobic, gram-positive, rod-shaped, thermophilic bacterium that grew on various sugars, carboxylic acids and hydrocarbons at temperatures between 45°C and 75°C. Complete 16S rRNA gene sequence of the microorganism exhibited homology to various species of genus Geobacillus. A highest homology of 99.8% was found with Geobacillus kaustophilus. A partial (0.7 kbp) chaperonin gene sequence also showed a highest homology of 99.4% to that of G. kaustophilus whereas biochemical characteristics of the microorganism were similar to Geobacillus uzenensis. Based on biochemical characterization, 16S rRNA and chaperonin gene sequences, we identified SBS-4S as a strain of genus Geobacillus. Strain SBS-4S produced several extracellular enzymes including amylase, protease and lipase. The lipase encoding gene was cloned, expressed in Escherichia coli and the gene product was characterized. The recombinant lipase was optimally active at 60°C with stability at wide pH range (6-12). The enzyme activity was enhanced remarkably in the presence of Ca(+2). The K(m) and the V(max) for the hydrolysis of p-nitrophenyl acetate were 3.8mM and 2273 μmol min(-1)mg(-1), respectively. The ability of the recombinant enzyme to be stable at a wide pH range makes it a potential candidate for use in industry.     

Vibrations of functionally graded cylindrical shells based on elastic foundations

In this paper, a study on the vibrations of functionally graded cylindrical shells based on the Winkler and Pasternak foundations is presented. The shell equations are amended by inducting the moduli of the Winkler and Pasternak foundations. The wave propagation method is employed to solve the shell dynamical equations. The method is based on the approximate eigenvalues of characteristic beam functions. The validity and accuracy of the present approach are verified by a number of comparisons.     

The moisture absorption of glass fibre reinforced vinylester and polyester composites

The water absorption characteristics of unidirectional glass reinforced vinylester and polyester laminates in distilled water and in 95% relative humidity at 25°C, 50°C, 60°C and 70°C were investigated. The results show that the calculated values and the experimental data agree reasonably well, but deviation occurred at higher temperatures.     

An application of univariate marginal distribution algorithm in MIMO communication systems

The paper discusses a sequence detector based on univariate marginal distribution algorithm (UMDA) that jointly estimates the symbols transmitted in a multiple input multiple output (MIMO) communication system. While an optimal maximum likelihood detection using an exhaustive search method is prohibitively complex, it has been shown that sphere decoder (SD) achieves the optimal bit error rate (BER) performance with polynomial time complexity for smaller array sizes. However, the worst‐case complexity of SD is exponential in the problem dimensions, this brings in question its practical implementation for larger number of spatial layers and for higher‐order signal constellation. The proposed detector shows promising results for this overly difficult and complicated operating environment, confirmed through simulation results. A performance comparison of the UMDA detector with SD is presented for higher‐order complex MIMO architectures with limited average transmit power. The proposed detector achieves substantial performance gain for higher‐order systems attaining a near optimal BER performance with reduced computational complexity as compared with SD. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermodynamic parameters of activation for photodegradation of phenolics

The photocatalytic degradation of three phenolics namely phenol, 4-chlorophenol and 4-nitrophenol were carried out in aerated aqueous suspension of TiO₂ irradiated by ultraviolet light. The influence of temperature at optimized pH and TiO₂ concentration was studied. The degradation kinetics were somewhat accelerated by increase in temperature in the range 25–45 °C and apparent activation energy was calculated to be 9.68–21.44 kJ mol^?1. Thermodynamic parameters of activation were also assessed for the degradation process. Formation of acidic species results in decrease in pH of solution. The appearance and the evolution of main intermediate species like hydroquinone, benzoquinone and catechol during the degradation process were computed by UV–vis spectral analysis.     

Physico-chemical,morphological and thermal analysis for the combined pozzolanic activities of minerals additives

The research was aimed to evaluate the physico-chemical, morphological and thermal analysis of combined pozzolanic activities of minerals additives. Fly ash and ground granulated blast furnace slag were added, separately and collectively, as mineral replacement in ordinary Portland cement. Tests carried out on specimens cured at different ages were: compressive strength, ultrasonic pulse velocity, X-ray diffraction (XRD) analysis, scanning electron microscopic (SEM) studies, differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA), etc. The results indicated that the compressive strength and ultrasonic pulse velocity development rate of concrete specimens were significantly influenced by the addition of mineral additives. SEM data showed that the fly ash particles were more embedded and surrounded by slag. XRD analysis and DTA/TGA investigation have revealed different reaction kinetics of paste. The peak intensity of calcium hydroxide was significantly retarded by the addition of fly ash and slag, especially in combination, attributed to the dilution effect and calcium hydroxide consumption by pozzolanic reaction.     

Family B DNA polymerase from a hyperthermophilic archaeon Pyrobaculum calidifontis: cloning, characterization and PCR application

The 2352 bp gene coding for 783 amino acid family B DNA polymerase from Pyrobaculum calidifontis was cloned and expressed in Escherichia coli. Expression of the gene resulted in the production of Pca-Pol in soluble fraction. After heat denaturation of the host proteins, the Pca-Pol was further purified by ion exchange and hydrophobic interaction chromatographies. Activity gel analysis showed the presence of a catalytically active polypeptide of about 90 kDa. The mass of the protein, determined by Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry was found to be 89,156 Da. The isoelectric point of the enzyme was found to be 6.13. The optimal pH and magnesium ion concentration for the enzyme activity were 8.5 and 4mM, respectively. Unlike other commercially available DNA polymerases the enzyme activity of Pca-Pol was inhibited by monovalent cations such as ammonium and potassium. The half-life of the polymerase at 95 °C and 100 °C was 4.5h and 0.5h, respectively. The enzyme possessed 3'→5' exonuclease activity and was able to amplify, under suitable conditions, up to 7.5 kb DNA fragments by polymerase chain reaction which makes it a potential candidate for amplification of long DNA fragments.     

Adsorption of VO2+ by poly[(tetrafluoroethylene)‐co‐(perfluorovinyl ether)] copolymer grafted with acrylic acid using γ‐irradiation

Grafted films were prepared by the reaction of acrylic acid (AAc) onto poly[(tetrafluoroethylene)‐co‐(perfluorovinyl ether)] copolymer (PFA) using γ‐irradiation by the mutual technique. The grafted copolymer was complexed with the vanadyl group, VO²⁺, in aqueous solution. The grafted copolymer–metal complexes were examined by infrared and ultraviolet spectrometry, energy‐dispersive spectroscopy (EDS) and X‐ray diffraction (XRD). The amount of vanadium in the grafted films was estimated using EDS. The thermal stability of the films was investigated through thermogravimetric and differential scanning calorimetry measurements. The degree of crystallinity of the grafted and complexed films decreased by treatment with VO²⁺ ions and also by heating at 300 °C. When heated at a temperature above 300 °C, the grafted chains degraded till they disappeared and the original polymer was almost completely separated. XRD investigation revealed that the metal oxide may be formed as a separate phase with subsequent decrease in the crystallinity of the copolymer. Furthermore, scanning electron microscope (SEM) investigation of the grafted and modified films, both unheated and heated (300 °C), showed changes in the structure and morphology. The tendency of the graft copolymer to adsorb and/or bind to VO²⁺ from aqueous solution is of promising use in the field of waste treatment of rare metals in the environment. Copyright © 2004 Society of Chemical Industry