The deep structure of the eastward-subducting Indian plate can provide new information on the dynamics of the India-Eurasia collision.We collected and processed waveform data from temporary seismic arrays(networks)on ...The deep structure of the eastward-subducting Indian plate can provide new information on the dynamics of the India-Eurasia collision.We collected and processed waveform data from temporary seismic arrays(networks)on the eastern Tibetan Plateau,seismic arrays in Northeast India and Myanmar,and permanent stations of the China Digital Seismic Network in Tibet,Gansu,Qinghai,Yunnan,and Sichuan.We combined these data with phase reports from observation stations of the International Seismological Center on the Indian plate and selected 124,808 high-quality P-wave relative travel-time residuals.Next,we used these data to invert the 3-D P-wave velocity structure of the upper mantle to a depth of 800 km beneath the eastern segment of the arcuate Himalayan orogen,at the southeastern margin of the Tibetan Plateau.The results reveal a high-angle,easterly dipping subducting plate extending more than 200 km beneath the Indo-Myanmese arc.The plate breaks off at roughly 96°E;its fragments have passed through the 410-km discontinuity(D410)into the mantle transition zone(MTZ).The MTZ beneath the Tengchong volcanic area contains a high-velocity anomaly,which does not exceed the Red River fault to the east.No other large-scale continuous subducted plates were observed in the MTZ.However,a horizontally spreading high-velocity anomaly was identified on the D410 in some regions.The anomaly may represent the negatively buoyant 90°E Ridge plate or a thickened and delaminated lithospheric block experiencing collision and compression at the southeastern margin of the Tibetan Plateau.The Tengchong volcano may originate from the mantle upwelling through the slab window formed by the break-off of the subducting Indian continental plate and oceanic plate in the upper mantle.Low-velocity upper mantle materials on the west side of the Indo-Myanmese arc may have supplemented materials to the Tengchong volcano.展开更多
How Escherichia coli bacteria develop a particular colonial, 3-D biofilm morphological pattern is still a poorly understood process. Recently, we reported a new E. coli K-12 morphotype exhibited by old macrocolonies d...How Escherichia coli bacteria develop a particular colonial, 3-D biofilm morphological pattern is still a poorly understood process. Recently, we reported a new E. coli K-12 morphotype exhibited by old macrocolonies described as volcano-like. The formative developmental process of this morphotype has been presented as a suitable experimental model for the study of 3D patterning in macrocolony biofilms. Here, we report the optical microscopy observations and genetic analysis that have unveiled the existence of a novel autoaggregative behaviour which generates massive lumpiness over the surface of the volcano-like macrocolonies. These lumpy formations are generated by the autoaggregation and strong interaction of tightly packed bacterial cells in structures with a chondrule-like appearance which give the colony’s surface its characteristic microscopic lumpy phenotype. Furthermore, they exhibit different levels of maturation from the edge to the center of the colony. Hence, its generation appears to follow a spatiotemporal program of development during the macrocolony’s morphogenesis. Interestingly, the agar’s hardness influences the morphology exhibited by these formations, with high agar concentration (1.5%, 15 g/L) suppressing its development. This new auto-aggregative E. coli’s behaviour does not require the activity of the biofilm master regulator CsgD, the adhesiveness of flagella, pili type 1, adhesin Ag43, β-1,6-N-acetyl-D-glucosamine polymer-PGA, cellulose or colanic acid, but it is under glucose repression and the control of cAMP receptor protein (CRP). The possible physiological role of these chondrule-like formations in the adaptability of the colony to different stressful environmental conditions is discussed.展开更多
Wangtian’ e volcano, about 30 km south of Tianchi volcano is another large scale volcano center on the south slope of Changbaishan with its nearly 4 000 km^2 area of volcanic rocks distributed over the border area of...Wangtian’ e volcano, about 30 km south of Tianchi volcano is another large scale volcano center on the south slope of Changbaishan with its nearly 4 000 km^2 area of volcanic rocks distributed over the border area of the Chinese side. Based on the field occurrence, petrology and K-Ar age dating of its volcanic rocks, it can be shown that the Wangtian’e volcano had experienced two developing stages of shield forming and cone forming, while its volcanic activities can be divided into three periods: Changbai period (? —2.87 Ma), Wangtian’e period (2.69—2.41 Ma) and Hongtoushan period (2.12 Ma). Its petrographic change goes from trachybasalt→basaltic trachyandesite, trachyte→alkalic rhyolite, with a feature of bimodal volcanic rock combination similar to yet a bit different from that of Tianchi volcano, and is a new scene for study of volcanic magma evaluation of Changbaishan volcanoes.展开更多
基金This work is jointly supported by the Youth Program of National Natural Science Foundation of China(Nos.41874075 and 41904057)
文摘The deep structure of the eastward-subducting Indian plate can provide new information on the dynamics of the India-Eurasia collision.We collected and processed waveform data from temporary seismic arrays(networks)on the eastern Tibetan Plateau,seismic arrays in Northeast India and Myanmar,and permanent stations of the China Digital Seismic Network in Tibet,Gansu,Qinghai,Yunnan,and Sichuan.We combined these data with phase reports from observation stations of the International Seismological Center on the Indian plate and selected 124,808 high-quality P-wave relative travel-time residuals.Next,we used these data to invert the 3-D P-wave velocity structure of the upper mantle to a depth of 800 km beneath the eastern segment of the arcuate Himalayan orogen,at the southeastern margin of the Tibetan Plateau.The results reveal a high-angle,easterly dipping subducting plate extending more than 200 km beneath the Indo-Myanmese arc.The plate breaks off at roughly 96°E;its fragments have passed through the 410-km discontinuity(D410)into the mantle transition zone(MTZ).The MTZ beneath the Tengchong volcanic area contains a high-velocity anomaly,which does not exceed the Red River fault to the east.No other large-scale continuous subducted plates were observed in the MTZ.However,a horizontally spreading high-velocity anomaly was identified on the D410 in some regions.The anomaly may represent the negatively buoyant 90°E Ridge plate or a thickened and delaminated lithospheric block experiencing collision and compression at the southeastern margin of the Tibetan Plateau.The Tengchong volcano may originate from the mantle upwelling through the slab window formed by the break-off of the subducting Indian continental plate and oceanic plate in the upper mantle.Low-velocity upper mantle materials on the west side of the Indo-Myanmese arc may have supplemented materials to the Tengchong volcano.
文摘How Escherichia coli bacteria develop a particular colonial, 3-D biofilm morphological pattern is still a poorly understood process. Recently, we reported a new E. coli K-12 morphotype exhibited by old macrocolonies described as volcano-like. The formative developmental process of this morphotype has been presented as a suitable experimental model for the study of 3D patterning in macrocolony biofilms. Here, we report the optical microscopy observations and genetic analysis that have unveiled the existence of a novel autoaggregative behaviour which generates massive lumpiness over the surface of the volcano-like macrocolonies. These lumpy formations are generated by the autoaggregation and strong interaction of tightly packed bacterial cells in structures with a chondrule-like appearance which give the colony’s surface its characteristic microscopic lumpy phenotype. Furthermore, they exhibit different levels of maturation from the edge to the center of the colony. Hence, its generation appears to follow a spatiotemporal program of development during the macrocolony’s morphogenesis. Interestingly, the agar’s hardness influences the morphology exhibited by these formations, with high agar concentration (1.5%, 15 g/L) suppressing its development. This new auto-aggregative E. coli’s behaviour does not require the activity of the biofilm master regulator CsgD, the adhesiveness of flagella, pili type 1, adhesin Ag43, β-1,6-N-acetyl-D-glucosamine polymer-PGA, cellulose or colanic acid, but it is under glucose repression and the control of cAMP receptor protein (CRP). The possible physiological role of these chondrule-like formations in the adaptability of the colony to different stressful environmental conditions is discussed.
文摘Wangtian’ e volcano, about 30 km south of Tianchi volcano is another large scale volcano center on the south slope of Changbaishan with its nearly 4 000 km^2 area of volcanic rocks distributed over the border area of the Chinese side. Based on the field occurrence, petrology and K-Ar age dating of its volcanic rocks, it can be shown that the Wangtian’e volcano had experienced two developing stages of shield forming and cone forming, while its volcanic activities can be divided into three periods: Changbai period (? —2.87 Ma), Wangtian’e period (2.69—2.41 Ma) and Hongtoushan period (2.12 Ma). Its petrographic change goes from trachybasalt→basaltic trachyandesite, trachyte→alkalic rhyolite, with a feature of bimodal volcanic rock combination similar to yet a bit different from that of Tianchi volcano, and is a new scene for study of volcanic magma evaluation of Changbaishan volcanoes.
