Extracts from lo-han-kuo (Siraitia grosvenorii) are of high sweetness and low calories, and they have been widely used as a natural sweetener to reduce the risk of obesity and diabetes. In the current study, lo-han-kuo extracts were extracted using subcritical water under different operation condition. The study revealed that the optimal extracting parameters were: extraction time of 20 min, extraction temperature of 140 °C, and the addition of 15% ethanol. Antioxidant activity, contents of total flavonoids, and total phenolic compounds of lo-han-kuo extracts were also investigated. A mathematical model was established to describe the relationship between antioxidant capacity and content of bioactive components in lo-han-kuo extract, and it was found that antioxidant capacity of the extracts was mainly attributed to the yields of total mogrosides (P<0.05).
Polyphenols in Chinese Kushui rose (Rosa sertata × Rosa rugosa) leaves were first extracted and analysed in this study. Among four fractions (ethyl ether, ethyl acetate, n-butanol, and water layer) of crude extracts, the ethyl acetate fraction showed the highest ABTS•+ scavenging activity, and the n-butanol fraction exhibited the maximum components in composition. On-line HPLC-ABTS•+ analysis indicated that there were more than 30 antioxidant compounds from Chinese Kushui rose leaves. The identified polyphenols could be classified into quercetin derivatives, gallic acid derivatives, and proanthocyanidins. Gallic acid was the most antioxidative compound.
Effects of gaseous hydrogenation on crystallization behavior of melt-spun Mg63Pr15Ni22 amorphous ribbons have been investigated. The crystallization peak temperature Tp1 shifted to higher temperature with increasing heating rate for the un-hydrogenated Mg63Ni22Pr15 metallic glass, however, it is nearly unchanged for the hydrogenated sample. The present work indicates that the crystallization
is a nucleation-and-growth process for the un-hydrogenated Mg63Ni22Pr15 metallic glass. However, the crystallization of hydrogenated sample begins with nucleation and then diffusion-controlled
growth takes place.
Polyaniline/multi-walled carbon nanotube (PANI/MWNT) composites were prepared by in situ polymerization. Transmission electron
microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) were used to characterize the PANI/MWNT composites.
Thermal stability and glass transition temperature (Tg) were measured by thermogravimetry (TG) and temperature modulated differential scanning calorimetry (TMDSC), respectively.
The TG and derivative thermogravimetry (DTG) curves indicated that with augment of MWNTs content, the thermal stability of
PANI/MWNT composites increased continuously. While, Tg increased and then decreased with the MWNTs content increasing from 0 to 20 mass%.
Comparative investigations of new regenerated cellulosic fibers, bamboo viscose fiber and Tencel, together with conventional
viscose fibers have been carried out to explain the similarity and difference in their molecular and fine structure. The analyses
jointly using SEM, XRD and IR reveal that all the three fibers belong to cellulose II. Tencel consists of longer molecules
and has a greater degree of crystallinity, while bamboo viscose fiber has a lower degree of crystallinty. TG-DTG-DSC study
shows three fibers resemble in thermal behavior with a two-step decomposition mode. The first step is associated to water
desorption, suggesting that bamboo viscose fiber holds better water retention and release ability, the second a depolymerization
and decomposition of regenerated cellulose, indicating that Tencel is more thermally stable in this process than bamboo and
conventional viscose fiber.