SUMMARYThe phylogenetic and epidemic relationships of 104 clinical isolatesof Clostridium difficilefrom three hospitals of different geographical and population sources in China were investigated by multilocus sequence typing. Twenty-two sequence types (STs) were identified, four of which, ST117, ST118, ST119 and ST129, were novel. No geographically specific and host population-specific phylogenetic lineages were found and there was no correlation between geographical origin or host population and strain genotype. ST37 was the dominant type in our survey but the four novel STs underline the high genetic diversity and unique polymorphisms inC. difficilefrom China.

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Based on the principle of vacuum counter-pressure casting, a low gas pressure infiltration technology was developed to fabricate the Ni-coated carbon fiber reinforced A357 alloy composites. The soundness and microstructure of the as-cast composites were investigated. The results show the relative density increases with the increase of melt temperature, while it firstly increases and then declines as the fiber temperature and infiltration pressure increased. The enhancement of melt and fiber temperature can eliminate the incomplete infiltration defects and improve the uniformity of fiber distribution. The insufficient infiltration pressure leads to some micro-pores in the matrix alloy. However, the over high fiber temperature and infiltration pressure may result in the separation of nickel coating and the fiber aggregation respectively, both of which are responsible for the partial un-infiltrated or insufficient filling defects. The appropriate infiltration parameters identified in this study could provide a reference for inhibition of the hazard interfacial reactions by optimizing the low gas pressure infiltration process.

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