The montmorillonites (MMTs), layered, smectite-type silicates, were premodified by two different methods prior to the polymer melt intercalation. In one case MMTs were modified with cetyltrimethylammonium bromide (CTA...The montmorillonites (MMTs), layered, smectite-type silicates, were premodified by two different methods prior to the polymer melt intercalation. In one case MMTs were modified with cetyltrimethylammonium bromide (CTAB), and termed as organomontmorillonites (OMMTs); in the other case MMTs were modified by nylon, and the products were called modified montmorillonites (MMMTs). The effects of CTAB and nylon on the MMTs were investigated by using TG and WAXD. The results show that interlayer spacings of CTAB and nylon modified MMTs are larger than that of sodium MMTs. Then, polyamide 66 (PA 66)/MMT nanocomposites were obtained through the method of melt intercalation of polymers. The nanocomposites were characterized by WAXD, TEM and Molau experiments. The results indicate that the MMTs disperse homogeneously in the PA 66 matrix. The mechanical properties of nanocomposites, such as tensile properties and flexural properties, were also measured and show a tendency to increase with increase of MMT content and reach the maximum values at 5phr MMT content. The heat distortion temperature (HDT) of the nanocomposites (7 phr) is about 32 K higher than that of pure PA 66.展开更多
To date, little is still known about how alpine species occurring in the Qinghai-Tibetan Plateau （QTP） responded to past climatic oscillations. Here, by using variations of the chloroplast trnT-L, we examined the ge...To date, little is still known about how alpine species occurring in the Qinghai-Tibetan Plateau （QTP） responded to past climatic oscillations. Here, by using variations of the chloroplast trnT-L, we examined the genetic distribution pattern of 101 individuals of Potentilla glabra, comprising both the interior QTP and the plateau edge. Phylogenetic and network analyses of 31 recovered haplotypes identified three tentative clades （A, B and C）. Analysis of molecular variance （AMOVA） revealed that most of the genetic variability was found within populations （0.693）, while differentiations between populations were obviously distinct （Fst -- 0.307）. Two independent range expansions within clades A and B occurring at approximately 316 and 201 thousand years ago （kya） were recovered from the hierarchical mismatch analysis, and these two expansions were also confirmed by Fu＇s Fs values and ＇g＇ tests. However, distant distributions of clade C and private haplotypes from clades A and B suggest that they had survived the Last Glacial Maximum （LGM） and previous glaciers in situ since their origins. Our findings based on available limited samples support that multiple refugia of a few cold-enduring species had been maintained in the QTP platform during LGM and/or previous glacial stages.展开更多
基金This project was supported by the Science Funds for Henan Province's Prominent Youth and the Science Funds for Henan Province's Creative Persons.
文摘The montmorillonites (MMTs), layered, smectite-type silicates, were premodified by two different methods prior to the polymer melt intercalation. In one case MMTs were modified with cetyltrimethylammonium bromide (CTAB), and termed as organomontmorillonites (OMMTs); in the other case MMTs were modified by nylon, and the products were called modified montmorillonites (MMMTs). The effects of CTAB and nylon on the MMTs were investigated by using TG and WAXD. The results show that interlayer spacings of CTAB and nylon modified MMTs are larger than that of sodium MMTs. Then, polyamide 66 (PA 66)/MMT nanocomposites were obtained through the method of melt intercalation of polymers. The nanocomposites were characterized by WAXD, TEM and Molau experiments. The results indicate that the MMTs disperse homogeneously in the PA 66 matrix. The mechanical properties of nanocomposites, such as tensile properties and flexural properties, were also measured and show a tendency to increase with increase of MMT content and reach the maximum values at 5phr MMT content. The heat distortion temperature (HDT) of the nanocomposites (7 phr) is about 32 K higher than that of pure PA 66.
基金Supported by the Frontier Project of the Knowledge Innovation Program of Northwest Plateau Institute of Biology of the Chinese Academy of Sciences,National Natural Science Foundation of China (30725004)the Programfor New Century Excellent Talents,Ministry of Education of China (NCET-05-0886)a Grant-in Aid for Scientific Research (A) from the Ministry of Education,Culture,Sports,Science and Technology,Government of Japan(18255004)
文摘To date, little is still known about how alpine species occurring in the Qinghai-Tibetan Plateau （QTP） responded to past climatic oscillations. Here, by using variations of the chloroplast trnT-L, we examined the genetic distribution pattern of 101 individuals of Potentilla glabra, comprising both the interior QTP and the plateau edge. Phylogenetic and network analyses of 31 recovered haplotypes identified three tentative clades （A, B and C）. Analysis of molecular variance （AMOVA） revealed that most of the genetic variability was found within populations （0.693）, while differentiations between populations were obviously distinct （Fst -- 0.307）. Two independent range expansions within clades A and B occurring at approximately 316 and 201 thousand years ago （kya） were recovered from the hierarchical mismatch analysis, and these two expansions were also confirmed by Fu＇s Fs values and ＇g＇ tests. However, distant distributions of clade C and private haplotypes from clades A and B suggest that they had survived the Last Glacial Maximum （LGM） and previous glaciers in situ since their origins. Our findings based on available limited samples support that multiple refugia of a few cold-enduring species had been maintained in the QTP platform during LGM and/or previous glacial stages.
