Sediment carbon sequestration plays an essential role in mitigating atmospheric CO2 increases and the subsequently global greenhouse effect. To clarify the late Quaternary strata and carbon burial records in YeUow Riv...Sediment carbon sequestration plays an essential role in mitigating atmospheric CO2 increases and the subsequently global greenhouse effect. To clarify the late Quaternary strata and carbon burial records in YeUow River delta （YRD）, detailed analysis of benthic foraminifera, total carbon （TC）, organic carbon （Corg）, sedimentary characteristics and moisture contents of sediments, was performed on core ZK3, 30.3 m in length and obtained from YRD in 2007. Eight depositional units （designated U1-U8 in ascending order） were identified. A comprehensive analysis method of historical geography and sedimentary geology was used to de- termine the precise depositional ages of the modem Yellow River delta （MYRD）, from which pre-MYRD ages were deduced. The results indicates that the maximum burial rates of TC, inorganic carbon （IC） and Corg occurred in the delta front （U5）, and the mini- mum in the shallow sea （U3）. Remarkable high sedimentation rates in the MYRD are responsible for burial efficiency of carbon, with an average rate of Corg burial reaching 2087±251 g（m2yr）-1, and that of IC reaching 13741±808g（m2yr）-1, which are much higher than those of other regions with high contents of Corg. Therefore, YRD has a significant burial efficiency for carbon sequestration.展开更多
Hepatitis C virus (HCV) is a member of the Flaviviridae family and causes acute and chronic hepatitis. Chronic HCV infection may result in severe liver damage including liver cirrhosis and hepatocellular carcinoma. Th...Hepatitis C virus (HCV) is a member of the Flaviviridae family and causes acute and chronic hepatitis. Chronic HCV infection may result in severe liver damage including liver cirrhosis and hepatocellular carcinoma. The liver is the primary target organ of HCV, and the hepatocyte is its primary target cell. Attachment of the virus to the cell surface followed by viral entry is the first step in a cascade of interactions between the virus and the target cell that is required for successful entry into the cell and initiation of infection. This step is an important determinant of tissue tropism and pathogenesis; it thus represents a major target for antiviral host cell responses, such as antibody-mediated virus neutralization. Following the development of novel cell culture models for HCV infection our understanding of the HCV entry process and mechanisms of virus neutralization has been markedly advanced. In this review we summarize recent developments in the molecular biology of viral entry and its impact on pathogenesis of HCV infection, development of novel preventive and therapeutic antiviral strategies.展开更多
This paper establishes the theoretical hypothesis of carbon intensity convergence, and through statistics to analyze and describe the whole country and the eastern and western regions with the use of mixed regression ...This paper establishes the theoretical hypothesis of carbon intensity convergence, and through statistics to analyze and describe the whole country and the eastern and western regions with the use of mixed regression model and fixed effects regression method, and test σ -convergence, absolute convergence and conditional convergence in order to have an empirical study on carbon convergence hypothesis.展开更多
Conventional analysis methods of cable structures do not consider sliding of cables inside the joint,which may lead to inaccuracy of the theoretical behavior of the structure.In order to develop an effective method fo...Conventional analysis methods of cable structures do not consider sliding of cables inside the joint,which may lead to inaccuracy of the theoretical behavior of the structure.In order to develop an effective method for cable sliding,a two-node cable element based on the analytical solution for an elastic catenary was studied.The cable sliding stiffness and the effect of friction were investigated.To validate the proposed numerical method,analyses of two examples given in the literature were conducted.The results demonstrated that the method given in this paper is accurate and effective,and can take into account cable sliding in cable structures.In addition,it was shown that the effect of cable sliding on the behavior of cable structures is significant.It was also shown that the friction at the support hampers the flow of the cable force,leading to unequal cable tensions on both sides of the support.展开更多
Based on eddy covariance measurements over two kinds of land surfaces(a degraded grassland and a maize cropland)in a semiarid area of China in 2005 and 2008,the effects of different gap filling methods,energy balance ...Based on eddy covariance measurements over two kinds of land surfaces(a degraded grassland and a maize cropland)in a semiarid area of China in 2005 and 2008,the effects of different gap filling methods,energy balance closure and friction velocity threshold(u*)on annual net ecosystem exchange(NEE)were analyzed.Six gap filling methods,including mean diurnal variation(MDV),marginal distribution sampling(MDS),and nonlinear regressions method,were investigated by generating secondary datasets with four different artificial gap lengths(ranging in length from single half-hours to 12 consecutive days).The MDS generally showed a good overall performance especially for long gaps,with an annual sum bias error less than 5 g C m-2 yr-1.There was a large positive annual sum bias error for nonlinear regressions,indicating an overestimate on net ecosystem respiration.The offset in the annual sum NEE for four nonlinear regressions was from 8.0 to 30.8 g C m-2 yr-1.As soil water content was a limiting factor in the semiarid area,the nonlinear regressions considering both soil temperature and soil water content as controlling variables had a better performance than others.The performance of MDV was better in daytime than in nighttime,with an annual sum bias error falling between-2.6 and-13.4 g C m-2 yr-1.Overall,the accuracy of the gap filling method was dependent on the type of the land surface,gap length,and the time of day when the data gap occurred.The energy balance ratio for the two ecosystems was nearly 80%.Turbulent intensity had a large impact on energy balance ratio.Low energy balance ratio was observed under low friction velocity during the night.When there was a large fetch distance in a wind direction,a low energy balance ratio was caused by mismatch of the footprints between the available energy and turbulent fluxes.The effect of energy balance correction on CO2 flux was evaluated by assuming the imbalance caused by the underestimation of sensible heat flux and latent heat flux.The results showed an average increase of 10 g C m-2 yr-1 for annual NEE in both ecosystems with an energy balance correction.On the other hand,the u*threshold also have a large impact on annual sum NEE.Net carbon emission increased 37.5 g C m-2 yr-1 as u*threshold increased from 0.1 to 0.2 m s-1,indicating a large impact of imposing u*threshold on net ecosystem carbon exchange.展开更多
基金funded by the National Natural Science Foundation of China (Grant Nos. 41406082, ZR2014DQ010, 40872167 and 41240022)Governmental Public Research Funds of China (Grant Nos. 201111023, 1212010611402 and GZH201200503)
文摘Sediment carbon sequestration plays an essential role in mitigating atmospheric CO2 increases and the subsequently global greenhouse effect. To clarify the late Quaternary strata and carbon burial records in YeUow River delta （YRD）, detailed analysis of benthic foraminifera, total carbon （TC）, organic carbon （Corg）, sedimentary characteristics and moisture contents of sediments, was performed on core ZK3, 30.3 m in length and obtained from YRD in 2007. Eight depositional units （designated U1-U8 in ascending order） were identified. A comprehensive analysis method of historical geography and sedimentary geology was used to de- termine the precise depositional ages of the modem Yellow River delta （MYRD）, from which pre-MYRD ages were deduced. The results indicates that the maximum burial rates of TC, inorganic carbon （IC） and Corg occurred in the delta front （U5）, and the mini- mum in the shallow sea （U3）. Remarkable high sedimentation rates in the MYRD are responsible for burial efficiency of carbon, with an average rate of Corg burial reaching 2087±251 g（m2yr）-1, and that of IC reaching 13741±808g（m2yr）-1, which are much higher than those of other regions with high contents of Corg. Therefore, YRD has a significant burial efficiency for carbon sequestration.
文摘Hepatitis C virus (HCV) is a member of the Flaviviridae family and causes acute and chronic hepatitis. Chronic HCV infection may result in severe liver damage including liver cirrhosis and hepatocellular carcinoma. The liver is the primary target organ of HCV, and the hepatocyte is its primary target cell. Attachment of the virus to the cell surface followed by viral entry is the first step in a cascade of interactions between the virus and the target cell that is required for successful entry into the cell and initiation of infection. This step is an important determinant of tissue tropism and pathogenesis; it thus represents a major target for antiviral host cell responses, such as antibody-mediated virus neutralization. Following the development of novel cell culture models for HCV infection our understanding of the HCV entry process and mechanisms of virus neutralization has been markedly advanced. In this review we summarize recent developments in the molecular biology of viral entry and its impact on pathogenesis of HCV infection, development of novel preventive and therapeutic antiviral strategies.
文摘This paper establishes the theoretical hypothesis of carbon intensity convergence, and through statistics to analyze and describe the whole country and the eastern and western regions with the use of mixed regression model and fixed effects regression method, and test σ -convergence, absolute convergence and conditional convergence in order to have an empirical study on carbon convergence hypothesis.
基金supported by the National Natural Science Foundation of China (Grant No. 50478075)Jiangsu "Six Top Talents" Program (Grant No. 07-F-008)+1 种基金Scientific Research Foundation of Graduate School of Southeast University (Grant No. YBJJ0817)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Conventional analysis methods of cable structures do not consider sliding of cables inside the joint,which may lead to inaccuracy of the theoretical behavior of the structure.In order to develop an effective method for cable sliding,a two-node cable element based on the analytical solution for an elastic catenary was studied.The cable sliding stiffness and the effect of friction were investigated.To validate the proposed numerical method,analyses of two examples given in the literature were conducted.The results demonstrated that the method given in this paper is accurate and effective,and can take into account cable sliding in cable structures.In addition,it was shown that the effect of cable sliding on the behavior of cable structures is significant.It was also shown that the friction at the support hampers the flow of the cable force,leading to unequal cable tensions on both sides of the support.
基金supported by the National Natural Science Foundation of China(Grant Nos.41275023,41021004))Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA05110102)
文摘Based on eddy covariance measurements over two kinds of land surfaces(a degraded grassland and a maize cropland)in a semiarid area of China in 2005 and 2008,the effects of different gap filling methods,energy balance closure and friction velocity threshold(u*)on annual net ecosystem exchange(NEE)were analyzed.Six gap filling methods,including mean diurnal variation(MDV),marginal distribution sampling(MDS),and nonlinear regressions method,were investigated by generating secondary datasets with four different artificial gap lengths(ranging in length from single half-hours to 12 consecutive days).The MDS generally showed a good overall performance especially for long gaps,with an annual sum bias error less than 5 g C m-2 yr-1.There was a large positive annual sum bias error for nonlinear regressions,indicating an overestimate on net ecosystem respiration.The offset in the annual sum NEE for four nonlinear regressions was from 8.0 to 30.8 g C m-2 yr-1.As soil water content was a limiting factor in the semiarid area,the nonlinear regressions considering both soil temperature and soil water content as controlling variables had a better performance than others.The performance of MDV was better in daytime than in nighttime,with an annual sum bias error falling between-2.6 and-13.4 g C m-2 yr-1.Overall,the accuracy of the gap filling method was dependent on the type of the land surface,gap length,and the time of day when the data gap occurred.The energy balance ratio for the two ecosystems was nearly 80%.Turbulent intensity had a large impact on energy balance ratio.Low energy balance ratio was observed under low friction velocity during the night.When there was a large fetch distance in a wind direction,a low energy balance ratio was caused by mismatch of the footprints between the available energy and turbulent fluxes.The effect of energy balance correction on CO2 flux was evaluated by assuming the imbalance caused by the underestimation of sensible heat flux and latent heat flux.The results showed an average increase of 10 g C m-2 yr-1 for annual NEE in both ecosystems with an energy balance correction.On the other hand,the u*threshold also have a large impact on annual sum NEE.Net carbon emission increased 37.5 g C m-2 yr-1 as u*threshold increased from 0.1 to 0.2 m s-1,indicating a large impact of imposing u*threshold on net ecosystem carbon exchange.
