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  • Author or Editor: A.K. Ray x
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The effect of % methacrylic acid (%MAA), % neutralization (%N) and ion type (Na+ or Zn++) on the crystalline properties of neutralized ethylene-methacrylic acid copolymers (ionomers) were studied using differential scanning calorimetry (DSC). Two endothermic melting peaks were observed for all the nine ionomers studied, the lower melting point (LMP) due to ordered ionic clusters and the higher melting point (HMP) due to polyethylene crystallites. Effects of %MAA, %N and ion type on LMP and HMP for as-received, aged and annealed samples are compared. Effect of types of pretreatments on LMP and HMP of ionomers at high and low %MAA contents for both ion types are discussed. Most of these results are explained from the point of view of crystalline morphology of ionomers.

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Present study demonstrated the isolation of most promising β-galactosidase producing bacterial strain SB from soil. Morphological, biochemical, and 16s rRNA sequence analysis identified the bacterial strain as Arthrobacter oxydans. Several chemicals, including SDS, Triton X-100, Tween 20, isoamyl alcohol, and toluene-acetone mixture, were applied for extraction of intracellular β-galactosidase from the bacterial strain Arthrobacter oxydans. Among these, Tween 20 was recorded to be most effective. Role of pH, temperature, and shaker speed on production of β-galactosidase was evaluated using Box-Behnken design of response surface methodology. According to Box-Behnken analysis, optimum production of β-galactosidase (21.38 U (mg–1 protein)) is predicted at pH 6.76, temperature 36.1 °C, and shaker speed 121.37 r.p.m. The parameters are validated with the nearest value.

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Abstract  

Thermal analysis has been employed in a study of the degradation of heritage Sydney sandstone used in St Mary’s Cathedral in Sydney, Australia. TG and DSC have been used to characterise the clay components removed from weathered and unweathered sandstone. Two types of kaolin clays — kaolinite and its polymorph, dickite — have been identified. A higher amount of dickite present in the clay of weathered sandstone indicates that a kaolinite-to-dickite transformation occurs upon weathering. XRD hot stage analysis was also used to demonstrate the presence of a more thermally stable polymorph of the kaolinite.

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Abstract  

Differential thermal analysis has been used for quantitative determination of heats of aluminothermic redox reaction of MnO2 and V2O5 over a wide range of temperatures. Heat of reaction V2O5−Al and MnO2−Al systems have been determined using the calibration plot established. The experimentally determined values compare well with those predicted from thermodynamic data available in the literature. It has been found that V2O5−Al system involves a higher heat of reaction in comparison to the MnO2−Al system.

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Thermogravimetric (TG) analysis was applied to the characterisation of the pozzolanic reaction in mortars containing the supplementary cementitious materials (SCMs) pitchstone fines (PF) and fly ash (FA) as partial replacements for Portland cement (PC). TG analysis was used to determine the proportion of calcium hydroxide (CH) present from the hydration of the PC based on the dehydroxylation of the CH present in the blended PC-SCM mortars. The consumption of CH indicated that both SCMs underwent the pozzolanic reaction and that PF was found to compare favourably in its pozzolanic reactivity of FA, the industry and globally accepted standard artificial pozzolan.

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Summary Many of Sydney’s heritage buildings and monuments were built as a result of the first European settlement in the 1800s. These buildings not only display the richness of the Australian culture, but also capture the architectural and historical values of its past. Although many of these buildings still appear to be strong and sound, many signs of deterioration have been detected in recent years. Conservators from various disciplines such as science, architecture and engineering are working closely together to develop suitable solutions to stop or at least slow down the degradation process of these precious buildings. This study demonstrates the usefulness of thermal analysis in determining the weathering mechanisms of marble and sandstone taken from two of Sydney’s landmarks, the Captain Arthur Phillips Monument at Sydney’s Botanic Gardens and Sydney’s St Mary’s Cathedral. This paper reports the findings of the weathering behaviours of both marble and sandstone samples determined using thermal analysis techniques.

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