Species richness in any area results from the interplay of the processes of speciation,extinction,and dispersal.The relationships between species richness and climate should be considered as an outcome of the effects ...Species richness in any area results from the interplay of the processes of speciation,extinction,and dispersal.The relationships between species richness and climate should be considered as an outcome of the effects of climate on speciation,extinction,and dispersal.Diversificationrate represents the balance of speciation and extinction rates over time.Here,I explore diversificationrates in mosses across geographic and climatic gradients worldwide.Specifically,I investigate latitudinal patterns and climatic associations of the mean diversificationrate of mosses at global,hemispheric,and smaller scales.I findthat the mean diversificationrate of mosses is positively correlated with species richness of mosses,increases with decreasing latitude and increasing mean annual temperature and annual precipitation,and is more strongly associated with mean annual temperature than with annual precipitation.These findingsshed light on variation of species richness in mosses across the world.The negative relationship between species richness and latitude and the positive relationship between species richness and mean diversificationrate in mosses suggest that higher moss species richness at lower latitudes might have resulted,at least to some degree,from higher moss diversificationrates at lower latitudes.展开更多
This study examines the return connectedness between decentralized finance(DeFi)’s and the Association of Southeast Asian Nations(ASEAN)stock markets using the quantile vector autoregressive framework,which allows us...This study examines the return connectedness between decentralized finance(DeFi)’s and the Association of Southeast Asian Nations(ASEAN)stock markets using the quantile vector autoregressive framework,which allows us to investigate the connectedness at conditional quantiles.Our sample includes four major DeFi’s and six ASEAN stock markets,spanning from March 2018 to December 2022.The static results indicate a moderate level of return transmission between the system at mean and median quantile.This propagation increases substantially under extreme market conditions,establishing an asymmetric transmission across quantiles.Despite being a relatively new asset class,DeFi dominates the equity market and acts as the primary shock transmitter to the system in most instances.The dynamic analysis reveals that total system connectedness fluctuates over time and quantiles.The total system connectedness peaked during the COVID-19 and the Russia–Ukraine conflict period,indicating the impact of global events on system transmission.The optimal weight and hedge ratio estimated using the DCC-GARCH model indicate that DeFi is beneficial for portfolio construction and risk management.The rising trend in dynamic optimal weight and hedge ratio during the COVID-19 pandemic demonstrates that investors should decrease their investments in DeFi and increase hedging costs.Therefore,portfolio managers and investors should readjust their portfolio allocation in a timely manner according to different market states to build additional effective hedging and diversification strategies to avoid large losses and to reduce portfolio risk exposure.展开更多
Elucidating the origins and mechanisms of polyploidization requires tracing the evolutionary history of polyploid species,particularly those with complex origins.Agropyron cristatum,traditionally regarded as an autopo...Elucidating the origins and mechanisms of polyploidization requires tracing the evolutionary history of polyploid species,particularly those with complex origins.Agropyron cristatum,traditionally regarded as an autopolyploid,exhibits characteristics indicative of a segmental allopolyploid.Here,we used phylogenetic analysis based on a low-copy nuclear gene(i.e.,Pgk1),SLAF-seq,and plastome data from 20 diploid and 120 tetraploid Agropyron individuals to determine whether tetraploid A.cristatum arose from an allopolyploid or autopolyploid event.Phylogenetic analyses based on Pgk1 and SLAF-seq data identified two distinct A.cristatum lineages that corresponded to the two main Agropyron habitats in Central Asia–Europe and East Asia–Qinghai-Tibet Plateau.These findings,taken together with molecular dating and gene flow analyses,suggest that the East Asian tetraploid A.cristatum originated via both autopolyploidy from A.cristatum and hybridization between diploid A.cristatum and A.mongolicum,with each diploid cytotype acting as a maternal donor.Furthermore,the Central Asia–Europe tetraploid A.cristatum originated solely via autopolyploidy of diploid A.cristatum.Our findings also indicate that rapid diversification of Agropyron was likely driven by climate oscillations,geographic isolation,introgressive hybridization,and chloroplast capture.These findings challenge simplistic views of autopolyploids and underscore substantial potential for achieving high levels of genetic and adaptive diversity through recurrent hybridization and reticulate evolution.展开更多
Purpose-This paper provides a comprehensive analysis of the Brazilian freight railway system,examining the efficacy of the current concession renewal model in light of persistent structural problems such as market con...Purpose-This paper provides a comprehensive analysis of the Brazilian freight railway system,examining the efficacy of the current concession renewal model in light of persistent structural problems such as market concentration,cargo dependence on export commodities and underutilization of the network.Situating Brazil within the broader international debate on railway reforms,the paper evaluates whether the ongoing early renewal of concessions can deliver a more diversified and competitive freight system.Design/methodology/approach-The study adopts a sequential mixed-methods research design that integrates longitudinal quantitative analysis with qualitative institutional and policy evaluation.The quantitative component examines time-series indicators published by ANTT,DNIT and INFRA S.A.from 1999 to 2023 to identify structural patterns in traffic growth,investment,safety and market concentration.The qualitative component employs a process-tracing logic to reconstruct the evolution of concession renewals and the implementation of Railway Law 14.273/2021,drawing on concepts from regulatory economics,institutional theory and industrial organization.These empirical streams are synthesized through an analytical framework that connects three dimensions-regulatory design,market structure and system performance-allowing for a systematic assessment of how Brazil’s institutional configuration shapes incentives,competitive dynamics and network utilization.Findings-The analysis confirms that the early renewal of concessions has successfully secured substantial private investment for capacity expansion on existing trunk lines.However,it has perpetuated the vertically integrated model,reinforcing the market power of incumbent operators and failing to significantly promote intramodal competition or cargo diversification.The system remains dominated by iron ore and agricultural commodities,with general cargo representing a minuscule share.The new authorization regime and short-line railway policies present a viable pathway for market opening but face significant operational and institutional barriers to implementation.Originality/value-This research offers a timely and critical assessment of a pivotal moment in Brazilian railway policy.It moves beyond a simplistic evaluation of volume growth to a structural analysis of market failures and the interplay between concession renewal and regulatory innovation.The findings provide actionable insights for policymakers in Brazil and other emerging economies seeking to balance private investment with public interest goals in railway infrastructure,highlighting the necessity of complementary,pro-competitive measures alongside financial investment.展开更多
Autonomous learning and its importance has attracted more and more attention,on the basis of which,independent read-ing activities should emphasizes the student as the center in the activity.So the choice of independe...Autonomous learning and its importance has attracted more and more attention,on the basis of which,independent read-ing activities should emphasizes the student as the center in the activity.So the choice of independent reading materials should bebased on their requirement.The materials should have the features of interesting and informative,varied style,content suitable forteaching materials,etc.At last how English teacher guide and conduct the students’activities of self-monitoring and self-assess-ment.展开更多
This study examined livelihood diversification and cropland use pattern in Keerma village, located in Jinchuan County, eastern Tibetan Plateau. Through stratified random sampling survey, participatory rural appraisal,...This study examined livelihood diversification and cropland use pattern in Keerma village, located in Jinchuan County, eastern Tibetan Plateau. Through stratified random sampling survey, participatory rural appraisal, investigation of households＇ plots and statistical methods, 63 households and 272 cropland plots were systemically investigated and sampled. The results show： （1） Different types of household have variety livelihood strategies, portfolio and income. Livelihood diversification and introducing and expanding off-farm activities can be the future trend, whereas, adverse natural environment, socio-economic conditions and peasants＇ capabilities together affect sustainable livelihood and land use. （2） Each livelihood strategy has its own impact on land use, mainly affecting land use type and land use intensi- fication level. （3） Diversification into off-farm activities could be the key of building sustainable livelihood and the essential approach of realizing sustainable land use in the region.展开更多
文摘Species richness in any area results from the interplay of the processes of speciation,extinction,and dispersal.The relationships between species richness and climate should be considered as an outcome of the effects of climate on speciation,extinction,and dispersal.Diversificationrate represents the balance of speciation and extinction rates over time.Here,I explore diversificationrates in mosses across geographic and climatic gradients worldwide.Specifically,I investigate latitudinal patterns and climatic associations of the mean diversificationrate of mosses at global,hemispheric,and smaller scales.I findthat the mean diversificationrate of mosses is positively correlated with species richness of mosses,increases with decreasing latitude and increasing mean annual temperature and annual precipitation,and is more strongly associated with mean annual temperature than with annual precipitation.These findingsshed light on variation of species richness in mosses across the world.The negative relationship between species richness and latitude and the positive relationship between species richness and mean diversificationrate in mosses suggest that higher moss species richness at lower latitudes might have resulted,at least to some degree,from higher moss diversificationrates at lower latitudes.
文摘This study examines the return connectedness between decentralized finance(DeFi)’s and the Association of Southeast Asian Nations(ASEAN)stock markets using the quantile vector autoregressive framework,which allows us to investigate the connectedness at conditional quantiles.Our sample includes four major DeFi’s and six ASEAN stock markets,spanning from March 2018 to December 2022.The static results indicate a moderate level of return transmission between the system at mean and median quantile.This propagation increases substantially under extreme market conditions,establishing an asymmetric transmission across quantiles.Despite being a relatively new asset class,DeFi dominates the equity market and acts as the primary shock transmitter to the system in most instances.The dynamic analysis reveals that total system connectedness fluctuates over time and quantiles.The total system connectedness peaked during the COVID-19 and the Russia–Ukraine conflict period,indicating the impact of global events on system transmission.The optimal weight and hedge ratio estimated using the DCC-GARCH model indicate that DeFi is beneficial for portfolio construction and risk management.The rising trend in dynamic optimal weight and hedge ratio during the COVID-19 pandemic demonstrates that investors should decrease their investments in DeFi and increase hedging costs.Therefore,portfolio managers and investors should readjust their portfolio allocation in a timely manner according to different market states to build additional effective hedging and diversification strategies to avoid large losses and to reduce portfolio risk exposure.
基金funded by the following projects:the National Natural Science Foundation of China(Nos.31870360 and 32171603)Xining Science and Technology Major Project(2023-Z-13)+2 种基金Qinghai Provincial Science and Technology Major Project(2023-SF-A5)Youth Innovation Promotion Association(Chinese Academy of Sciences,Grant/Award Number:Y2023116)the Qinghai Provincial central guide local science and technology development funds project(2025ZY002).
文摘Elucidating the origins and mechanisms of polyploidization requires tracing the evolutionary history of polyploid species,particularly those with complex origins.Agropyron cristatum,traditionally regarded as an autopolyploid,exhibits characteristics indicative of a segmental allopolyploid.Here,we used phylogenetic analysis based on a low-copy nuclear gene(i.e.,Pgk1),SLAF-seq,and plastome data from 20 diploid and 120 tetraploid Agropyron individuals to determine whether tetraploid A.cristatum arose from an allopolyploid or autopolyploid event.Phylogenetic analyses based on Pgk1 and SLAF-seq data identified two distinct A.cristatum lineages that corresponded to the two main Agropyron habitats in Central Asia–Europe and East Asia–Qinghai-Tibet Plateau.These findings,taken together with molecular dating and gene flow analyses,suggest that the East Asian tetraploid A.cristatum originated via both autopolyploidy from A.cristatum and hybridization between diploid A.cristatum and A.mongolicum,with each diploid cytotype acting as a maternal donor.Furthermore,the Central Asia–Europe tetraploid A.cristatum originated solely via autopolyploidy of diploid A.cristatum.Our findings also indicate that rapid diversification of Agropyron was likely driven by climate oscillations,geographic isolation,introgressive hybridization,and chloroplast capture.These findings challenge simplistic views of autopolyploids and underscore substantial potential for achieving high levels of genetic and adaptive diversity through recurrent hybridization and reticulate evolution.
文摘Purpose-This paper provides a comprehensive analysis of the Brazilian freight railway system,examining the efficacy of the current concession renewal model in light of persistent structural problems such as market concentration,cargo dependence on export commodities and underutilization of the network.Situating Brazil within the broader international debate on railway reforms,the paper evaluates whether the ongoing early renewal of concessions can deliver a more diversified and competitive freight system.Design/methodology/approach-The study adopts a sequential mixed-methods research design that integrates longitudinal quantitative analysis with qualitative institutional and policy evaluation.The quantitative component examines time-series indicators published by ANTT,DNIT and INFRA S.A.from 1999 to 2023 to identify structural patterns in traffic growth,investment,safety and market concentration.The qualitative component employs a process-tracing logic to reconstruct the evolution of concession renewals and the implementation of Railway Law 14.273/2021,drawing on concepts from regulatory economics,institutional theory and industrial organization.These empirical streams are synthesized through an analytical framework that connects three dimensions-regulatory design,market structure and system performance-allowing for a systematic assessment of how Brazil’s institutional configuration shapes incentives,competitive dynamics and network utilization.Findings-The analysis confirms that the early renewal of concessions has successfully secured substantial private investment for capacity expansion on existing trunk lines.However,it has perpetuated the vertically integrated model,reinforcing the market power of incumbent operators and failing to significantly promote intramodal competition or cargo diversification.The system remains dominated by iron ore and agricultural commodities,with general cargo representing a minuscule share.The new authorization regime and short-line railway policies present a viable pathway for market opening but face significant operational and institutional barriers to implementation.Originality/value-This research offers a timely and critical assessment of a pivotal moment in Brazilian railway policy.It moves beyond a simplistic evaluation of volume growth to a structural analysis of market failures and the interplay between concession renewal and regulatory innovation.The findings provide actionable insights for policymakers in Brazil and other emerging economies seeking to balance private investment with public interest goals in railway infrastructure,highlighting the necessity of complementary,pro-competitive measures alongside financial investment.
文摘Autonomous learning and its importance has attracted more and more attention,on the basis of which,independent read-ing activities should emphasizes the student as the center in the activity.So the choice of independent reading materials should bebased on their requirement.The materials should have the features of interesting and informative,varied style,content suitable forteaching materials,etc.At last how English teacher guide and conduct the students’activities of self-monitoring and self-assess-ment.
基金National Natural Science Foundation of China, No.40471009 No.40601006 National Basic Research Program of China, No.2005CB422006 Acknowledgements The authors would like to thank involved Department concerned of Jinchuan County Government and Archives Bureau for supplying the Sha＇er Township Government Agriculture Statistic Annals and other assistance, Mr. Yang Zulie from Jinchuan County, Mr. Gao Zhigui and Lei Yongmao from Keerma Village for their help during the field surveys.
文摘This study examined livelihood diversification and cropland use pattern in Keerma village, located in Jinchuan County, eastern Tibetan Plateau. Through stratified random sampling survey, participatory rural appraisal, investigation of households＇ plots and statistical methods, 63 households and 272 cropland plots were systemically investigated and sampled. The results show： （1） Different types of household have variety livelihood strategies, portfolio and income. Livelihood diversification and introducing and expanding off-farm activities can be the future trend, whereas, adverse natural environment, socio-economic conditions and peasants＇ capabilities together affect sustainable livelihood and land use. （2） Each livelihood strategy has its own impact on land use, mainly affecting land use type and land use intensi- fication level. （3） Diversification into off-farm activities could be the key of building sustainable livelihood and the essential approach of realizing sustainable land use in the region.
