Evergreen broad-leaved forestis one of the most important vegetation types in China.Because of the human activities,evergreen broad-leaved forest has been destroyed extensively,leading to degraded ecosystem.It is urge...Evergreen broad-leaved forestis one of the most important vegetation types in China.Because of the human activities,evergreen broad-leaved forest has been destroyed extensively,leading to degraded ecosystem.It is urgent to conserve and restore these natural forests in China. In this paper,the tendency and rate of species diversity restoration of the evergreen broad-leaved forest in Daming Mountain has been studied.The main resultsare as follows:(a)In subtropical mid-mountain area,species diversity in degraded evergreen broad-leaved forestcan be restored. Through analyzing b diversity index of communities in different time and space,it was found that the species composition of communities tend to be the same as that in the zonal evergreen broad-leaved forest.(b)The restoration rate of evergreen broad-leaved forest was very fast.Planting Chinese fir after clear-cutting and controlled burning of the forest,178 species appeared in a 600m^2 sample area after 20 years’natural recovering.Among the sespecies,58 were tree layer and the height of community reached 18m.The survey suggested that it would take only 20 years for the degraded forest to develop into community composed of lightdemanding broad-leaved pioneer trees and min-tolerance broad-leaved trees,and it need another 40~80 years to reach the stage consisting of min-tolerance evergreen broad-leaved trees.(c)Species number increased quickly at the early stage(2-20years)during vegetation recovering process toward the climax,and decreased at the min-stage (50-60 years),then maintained a relatively stable level at the late-stage (over 150 years).展开更多
To assess the hemodynamic performance and biocompatibility of China-made solid pyrolytic carbon bileaflet valve prosthesis so as to provide evidences for clinical trial,fifteen sheep aged 5-6 months underwent mitral r...To assess the hemodynamic performance and biocompatibility of China-made solid pyrolytic carbon bileaflet valve prosthesis so as to provide evidences for clinical trial,fifteen sheep aged 5-6 months underwent mitral replacement with 21-mm JiuLing valve under cardiopulmonary bypass. The first ten sheep underwent preliminary study to establish the trial methods and the matching of animal weight and prosthesis size, other five underwent formal experiment. The hemodynamic parameters of the prosthesis were determined by means of open cardiac catheterization and echocardiography intraoperatively and 2.5 years after operation respectively. The biocompatibility was evaluated by observing animal survival and valve thrombosis or thromboembolism.In result,all of the five sheep undergoing formal experiment survived well. There were no any prosthesis-related complications including mechanical valve failures, endocarditis, thrombosis, thromboembolism, and paravalvular leak. The transvalvular gradients were 5.2±1.7mmHg, 6.1±0.3mmHg and 6.8±0.4mmHg, the former was measured by catheterization intraoperatively, the two later were achieved by catheterization and echocardiography respectively 2.5 years after operation. The gradients increased mildly with the marked increase in cardiac output under dobutamine stress.The results of this study demonstrated that the JiuLing valve prosthesis has good biocompatibility and excellent hemodynamic performance.展开更多
A large class of non-coding RNAs found in small molecule RNAs are closely associated with the regula-tion of gene expression, which are called microRNA (miRNA). MiRNAs are coded in intergenic or intronic regions and c...A large class of non-coding RNAs found in small molecule RNAs are closely associated with the regula-tion of gene expression, which are called microRNA (miRNA). MiRNAs are coded in intergenic or intronic regions and can be formed into foldback hairpin RNAs. These transcripts are cleaved by Dicer, generating mature miRNAs that can silence their target genes in different modes of action. Now, research on small molecule RNAs has gotten breakthrough advance in biology. To discover miRNA genes and their target genes has become hot topics in RNA research. This review attempts to look back the history of miRNA discovery, to introduce the methods of screening miRNAs, to localize miRNA loci in genome, to seek miRNA target genes and the biological func-tion, and to discuss the working mechanisms of miRNAs. Finally, we will discuss the potential important roles of miRNAs in modulating the genesis, development, growth, and differentiation of organisms. Thus, it can be predicted that a complete understanding of miRNA functions will bring us some new concepts, approaches and strategies for the study of living beings.展开更多
基金This item was supportedby the National ScienceFoundationof P.R.China (No.39330040,39460022)
文摘Evergreen broad-leaved forestis one of the most important vegetation types in China.Because of the human activities,evergreen broad-leaved forest has been destroyed extensively,leading to degraded ecosystem.It is urgent to conserve and restore these natural forests in China. In this paper,the tendency and rate of species diversity restoration of the evergreen broad-leaved forest in Daming Mountain has been studied.The main resultsare as follows:(a)In subtropical mid-mountain area,species diversity in degraded evergreen broad-leaved forestcan be restored. Through analyzing b diversity index of communities in different time and space,it was found that the species composition of communities tend to be the same as that in the zonal evergreen broad-leaved forest.(b)The restoration rate of evergreen broad-leaved forest was very fast.Planting Chinese fir after clear-cutting and controlled burning of the forest,178 species appeared in a 600m^2 sample area after 20 years’natural recovering.Among the sespecies,58 were tree layer and the height of community reached 18m.The survey suggested that it would take only 20 years for the degraded forest to develop into community composed of lightdemanding broad-leaved pioneer trees and min-tolerance broad-leaved trees,and it need another 40~80 years to reach the stage consisting of min-tolerance evergreen broad-leaved trees.(c)Species number increased quickly at the early stage(2-20years)during vegetation recovering process toward the climax,and decreased at the min-stage (50-60 years),then maintained a relatively stable level at the late-stage (over 150 years).
文摘To assess the hemodynamic performance and biocompatibility of China-made solid pyrolytic carbon bileaflet valve prosthesis so as to provide evidences for clinical trial,fifteen sheep aged 5-6 months underwent mitral replacement with 21-mm JiuLing valve under cardiopulmonary bypass. The first ten sheep underwent preliminary study to establish the trial methods and the matching of animal weight and prosthesis size, other five underwent formal experiment. The hemodynamic parameters of the prosthesis were determined by means of open cardiac catheterization and echocardiography intraoperatively and 2.5 years after operation respectively. The biocompatibility was evaluated by observing animal survival and valve thrombosis or thromboembolism.In result,all of the five sheep undergoing formal experiment survived well. There were no any prosthesis-related complications including mechanical valve failures, endocarditis, thrombosis, thromboembolism, and paravalvular leak. The transvalvular gradients were 5.2±1.7mmHg, 6.1±0.3mmHg and 6.8±0.4mmHg, the former was measured by catheterization intraoperatively, the two later were achieved by catheterization and echocardiography respectively 2.5 years after operation. The gradients increased mildly with the marked increase in cardiac output under dobutamine stress.The results of this study demonstrated that the JiuLing valve prosthesis has good biocompatibility and excellent hemodynamic performance.
文摘A large class of non-coding RNAs found in small molecule RNAs are closely associated with the regula-tion of gene expression, which are called microRNA (miRNA). MiRNAs are coded in intergenic or intronic regions and can be formed into foldback hairpin RNAs. These transcripts are cleaved by Dicer, generating mature miRNAs that can silence their target genes in different modes of action. Now, research on small molecule RNAs has gotten breakthrough advance in biology. To discover miRNA genes and their target genes has become hot topics in RNA research. This review attempts to look back the history of miRNA discovery, to introduce the methods of screening miRNAs, to localize miRNA loci in genome, to seek miRNA target genes and the biological func-tion, and to discuss the working mechanisms of miRNAs. Finally, we will discuss the potential important roles of miRNAs in modulating the genesis, development, growth, and differentiation of organisms. Thus, it can be predicted that a complete understanding of miRNA functions will bring us some new concepts, approaches and strategies for the study of living beings.
