Heavily populated by Beijing and Tianjin cities, Bohai basin is a seismically active Cenozoic basin suffering from huge lost by devastating earthquakes, such as Tangshan earthquake. The attenuation （Qp and Qs） of th...Heavily populated by Beijing and Tianjin cities, Bohai basin is a seismically active Cenozoic basin suffering from huge lost by devastating earthquakes, such as Tangshan earthquake. The attenuation （Qp and Qs） of the surficial Quaternary sediment has not been studied at natural seismic frequency （1-10 Hz）, which is crucial to earthquake hazards study. Borehole seismic records of micro earthquake provide us a good way to study the velocity and attenuation of the surficial structure （0-500 m）. We found that there are two pulses well separated with simple waveforms on borehole seismic records from the 2006 Mw4.9 Wen＇an earthquake sequence. Then we performed waveform modeling with generalized ray theory （GRT） to confirm that the two pulses are direct wave and surface reflected wave, and found that the average vp and Vs of the top 300 m in this region are about 1.8 km/s and 0.42 km/s, leading to high ve/vs ratio of 4.3. We also modeled surface refleeted wave with propagating matrix method to constrain Qs and the near surface velocity structure. Our modeling indicates that Qs is at least 30, or probably up to 100, much larger than the typically assumed extremely low Q（-10）, but consistent with Qs modeling in Mississippi embayment. Also, the velocity gradient just beneath the free surface （0-50 m） is very large and velocity increases gradually at larger depth. Our modeling demonstrates the importance of borebole seismic records in resolving shallow velocity and attenuation structure, and hence may help in earthquake hazard simulation.展开更多
Often as a result ofbiofilm formation, drinking water distribution systems （DWDS） are regularly faced with the problem of microbial contamination. Quorum sensing （QS） systems play a marked role in the regulation o...Often as a result ofbiofilm formation, drinking water distribution systems （DWDS） are regularly faced with the problem of microbial contamination. Quorum sensing （QS） systems play a marked role in the regulation of microbial biofilm formation; thus, inhibition of QS systems may provide a promising approach to biofilm formation control in DWDS. In the present study, 22 bacterial strains were isolated from drinking water-related environments. The following properties of the strains were investigated： bacterial biofilm formation capacity, QS signal molecule N-acyl-L-homoserine lactones （AHLs） production ability, and responses to AHLs and AHL analogs, 3-chloro-4-（dichloromethyl）-5-hydroxy-2（5H）- furanone （MX） and 2（5H）-furanone. Four AHLs were added to developed biofilms at dosages ranging from 0.1 nmol.L J to 100nmol.L1. As a result, the biofilm growth of more than 1/4 of the isolates, which included AHL producers and non-producers, were significantly promoted. Further, the biofilm biomasses were closely associated with respective AHLs concentrations. These results provided evidence to support the idea that AHLs play a definitive role in biofilm formation in many of the studied bacteria. Meanwhile, two AHLs analogs demon- strated unexpectedly minimal negative effects on biofilm formation. This suggested that, in order to find an applicable QS inhibition approach for biofilm control in DWDS, the testing and analysis of more analogs is needed.展开更多
基金supported by National Natural Science Foundation of China (No.40676067)Knowledge Innovation Program of Chinese Academy of Sciences (No.kzcx2-yw-116-1)
文摘Heavily populated by Beijing and Tianjin cities, Bohai basin is a seismically active Cenozoic basin suffering from huge lost by devastating earthquakes, such as Tangshan earthquake. The attenuation （Qp and Qs） of the surficial Quaternary sediment has not been studied at natural seismic frequency （1-10 Hz）, which is crucial to earthquake hazards study. Borehole seismic records of micro earthquake provide us a good way to study the velocity and attenuation of the surficial structure （0-500 m）. We found that there are two pulses well separated with simple waveforms on borehole seismic records from the 2006 Mw4.9 Wen＇an earthquake sequence. Then we performed waveform modeling with generalized ray theory （GRT） to confirm that the two pulses are direct wave and surface reflected wave, and found that the average vp and Vs of the top 300 m in this region are about 1.8 km/s and 0.42 km/s, leading to high ve/vs ratio of 4.3. We also modeled surface refleeted wave with propagating matrix method to constrain Qs and the near surface velocity structure. Our modeling indicates that Qs is at least 30, or probably up to 100, much larger than the typically assumed extremely low Q（-10）, but consistent with Qs modeling in Mississippi embayment. Also, the velocity gradient just beneath the free surface （0-50 m） is very large and velocity increases gradually at larger depth. Our modeling demonstrates the importance of borebole seismic records in resolving shallow velocity and attenuation structure, and hence may help in earthquake hazard simulation.
文摘Often as a result ofbiofilm formation, drinking water distribution systems （DWDS） are regularly faced with the problem of microbial contamination. Quorum sensing （QS） systems play a marked role in the regulation of microbial biofilm formation; thus, inhibition of QS systems may provide a promising approach to biofilm formation control in DWDS. In the present study, 22 bacterial strains were isolated from drinking water-related environments. The following properties of the strains were investigated： bacterial biofilm formation capacity, QS signal molecule N-acyl-L-homoserine lactones （AHLs） production ability, and responses to AHLs and AHL analogs, 3-chloro-4-（dichloromethyl）-5-hydroxy-2（5H）- furanone （MX） and 2（5H）-furanone. Four AHLs were added to developed biofilms at dosages ranging from 0.1 nmol.L J to 100nmol.L1. As a result, the biofilm growth of more than 1/4 of the isolates, which included AHL producers and non-producers, were significantly promoted. Further, the biofilm biomasses were closely associated with respective AHLs concentrations. These results provided evidence to support the idea that AHLs play a definitive role in biofilm formation in many of the studied bacteria. Meanwhile, two AHLs analogs demon- strated unexpectedly minimal negative effects on biofilm formation. This suggested that, in order to find an applicable QS inhibition approach for biofilm control in DWDS, the testing and analysis of more analogs is needed.
