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  • Author or Editor: Lian Liu x
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Abstract

The rate of heat output is one of the suitable measurements of metabolic activity of the organism. In this article, microcalorimetry was first applied to study the effect of volatile oil of dry ginger (ginger oil) on Escherichia coli and Staphylococcus aureus growth. The power–time curves were plotted with a TAM air isothermal microcalorimeter. The parameters such as the growth rate constant μ, the peak-time T p, inhibitory ratio I, and half-inhibitory concentration IC50 were calculated. From the data, the relationships between μ and the concentration of ginger oil c were established. The results revealed that the μ of E. coli and S. aureus both gradually declined with the increase of the c, there were linear relationships between μ and c, and ginger oil had stronger inhibitory effect on S. aureus than on E. coli. Results obtained from our study strongly suggest that microcalorimetry is an ideal method to investigate the effect of drug on microorganism.

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Abstract  

In this study, α-phase nucleating agent (NA) 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS), β-phase rare earth NA (WBG), and their compound NAs were introduced into isotactic polypropylene (iPP) matrix, respectively. Crystallization kinetics and subsequent melting behavior of the nucleated iPPs were comparatively studied by differential scanning calorimetry (DSC) under both isothermal and nonisothermal conditions. For the isothermal crystallization process, it is found that the Avrami model successfully described the crystallization kinetics. The active energy of nonisothermal crystallization of iPP was determined by the Kissinger method and showed that the addition of nucleating agents increased the activation energy. Melting behavior and crystalline structure of the nucleated iPPs are dependent on the nature of NAs and crystallization conditions. Higher proportion of β-phase can be obtained at higher content of β-nucleating agent and lower crystallization temperature or lower cooling rate.

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Abstract

Crystallization behavior of isotactic polypropylene (iPP)/magnesium salt whisker (MSW) composites modified by compatibilizer PP-g-MAH was studied under both isothermal and nonisothermal conditions. Analysis of the isothermal crystallization showed that the Avrami model successfully described the crystallization process. On the basis of Lauritzen–Hoffman theory, a regime transition was observed at about 139 °C for the iPP/MSW composite, and a decrease in the fold surface free energy was calculated with the addition of MSW and PP-g-MAH. The addition of MSW filler and PP-g-MAH compatibilizer distinctly improved the crystallization temperature and accelerated the total crystallization rate of iPP. It was observed that MSW induced the formation of β-iPP but PP-g-MAH suppressed the formation of β-iPP.

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