Objective To investigate the occurrence of important foodbome pathogens in shellstock Pacific oysters in the food markets in South China. Methods From July 2007 to June 2008, retail oysters were collected in different...Objective To investigate the occurrence of important foodbome pathogens in shellstock Pacific oysters in the food markets in South China. Methods From July 2007 to June 2008, retail oysters were collected in different seasons from South China and analyzed for the prevalence and levels of Listeria monocytogenes, Vibrio vulnificus and Vibrio parahaemolyticus. Results None of L. monocytogenes could be detected in any of the 202 oyster samples tested, while E vulnificus and E parahaemolyticus could be detected in 67 （54.9%） and 109 （89.3%） of the 122 oyster samples analyzed, respectively, with an MPN （most probable number） value greater than or equal to 3. V. wdnificus and Eparahaemolyticus with a more than 102 MPN/g were found in 36 （29.5%） and 59 （48.4%） of the 122 oyster samples, respectively. The tdh and trh genes were detected in 4 （0.3%） and 8 （0.6%） of the 1 349 V. parahaemolyticus isolates, respectively. Of the 122 samples, 4 （3.3%） was positive for either tdh or trh. The levels of E vulnificus and total V. parahaemolyticus in oysters in South China varied in different seasons. Conclusion V. vulnificus and pathogenic V. parahaemolyticus are frequently found in oysters in south China, which may pose a potential threat to public health. Data presented here will be useful for the microbiological risk assessment in oysters in China.展开更多
Metallocene based polyethylenes were prepared by SMOPEC's 'metallocene adduct' technology in a gas phase fluidized bed model reactor. The C-13-NMR spectra of ethylene/1-butene (S-34) and ethylene/1-hexene(...Metallocene based polyethylenes were prepared by SMOPEC's 'metallocene adduct' technology in a gas phase fluidized bed model reactor. The C-13-NMR spectra of ethylene/1-butene (S-34) and ethylene/1-hexene(S-43) copolymers were studied in a manner analogous to that established by Hsieh and Cheng. The comonomer sequence distributions of copolymer samples were obtained. The results show that these metallocene based copolymers contain a small amount of butene and hexene, and the EE and EEE sequences are dominant.展开更多
基金supported by grants from the Key Projects in the National Science and Technology Pillar Program of China in the Eleventh Five-year Plan Period (Contract No. 2006BAK02A15)National Natural Science Foundation of China (Contract No. 30600499)
文摘Objective To investigate the occurrence of important foodbome pathogens in shellstock Pacific oysters in the food markets in South China. Methods From July 2007 to June 2008, retail oysters were collected in different seasons from South China and analyzed for the prevalence and levels of Listeria monocytogenes, Vibrio vulnificus and Vibrio parahaemolyticus. Results None of L. monocytogenes could be detected in any of the 202 oyster samples tested, while E vulnificus and E parahaemolyticus could be detected in 67 （54.9%） and 109 （89.3%） of the 122 oyster samples analyzed, respectively, with an MPN （most probable number） value greater than or equal to 3. V. wdnificus and Eparahaemolyticus with a more than 102 MPN/g were found in 36 （29.5%） and 59 （48.4%） of the 122 oyster samples, respectively. The tdh and trh genes were detected in 4 （0.3%） and 8 （0.6%） of the 1 349 V. parahaemolyticus isolates, respectively. Of the 122 samples, 4 （3.3%） was positive for either tdh or trh. The levels of E vulnificus and total V. parahaemolyticus in oysters in South China varied in different seasons. Conclusion V. vulnificus and pathogenic V. parahaemolyticus are frequently found in oysters in south China, which may pose a potential threat to public health. Data presented here will be useful for the microbiological risk assessment in oysters in China.
文摘Metallocene based polyethylenes were prepared by SMOPEC's 'metallocene adduct' technology in a gas phase fluidized bed model reactor. The C-13-NMR spectra of ethylene/1-butene (S-34) and ethylene/1-hexene(S-43) copolymers were studied in a manner analogous to that established by Hsieh and Cheng. The comonomer sequence distributions of copolymer samples were obtained. The results show that these metallocene based copolymers contain a small amount of butene and hexene, and the EE and EEE sequences are dominant.
