Extensive efforts have been devoted to the design of micro-, nano-, and/or molecular structures of sulfur hosts to address the challenges of lithium–sulfur(Li–S) batteries, yet comparatively little research has been...Extensive efforts have been devoted to the design of micro-, nano-, and/or molecular structures of sulfur hosts to address the challenges of lithium–sulfur(Li–S) batteries, yet comparatively little research has been carried out on the binders in Li–S batteries. Herein, we systematically review the polymer composite frameworks that confine the sulfur within the sulfur electrode, taking the roles of sulfur hosts and functions of binders into consideration. In particular, we investigate the binding mechanism between the binder and sulfur host(such as mechanical interlocking and interfacial interactions), the chemical interactions between the polymer binder and sulfur(such as covalent bonding, electrostatic bonding, etc.), as well as the beneficial functions that polymer binders can impart on Li–S cathodes, such as conductive binders, electrolyte intake, adhesion strength etc. This work could provide a more comprehensive strategy in designing sulfur electrodes for long-life, large-capacity and high-rate Li–S battery.展开更多
Soil seed banks are a vital part of ecosystems and influence community dynamics and regeneration.Although soil seed banks in different habitats have been reported, how soil seed banks vary with elevational gradients i...Soil seed banks are a vital part of ecosystems and influence community dynamics and regeneration.Although soil seed banks in different habitats have been reported, how soil seed banks vary with elevational gradients in different climatic zones is still unknown. This paper investigates seed density,species composition and nonconstituent species of forest soil seed banks in Yunnan Province, southwest China. Similarity between the soil seed bank and standing vegetation was also examined. We collected soil samples from sites spanning 12 elevations in tropical rain forests, subtropical evergreen broadleaved forests and subalpine coniferous forests, and transported them to a glasshouse for germination trials for species identification. The soil seed banks of tropical and subtropical forests had much higher seed densities and species richness than those of subalpine forests. Seeds of woody species dominated the soil seed banks of tropical and subtropical forests, while herbs dominated those of subalpine forests.The nonconstituent species in the soil seed banks were all herbs and were most abundant in tropical forests, followed by subtropical forests but were completely absent from subalpine forests.展开更多
Silicon is a promising anode material for rechargeable Li-ion battery (LIB) due to its high energy density and relatively low operating voltage. However, silicon based electrodes suffer from rapid capacity degradation...Silicon is a promising anode material for rechargeable Li-ion battery (LIB) due to its high energy density and relatively low operating voltage. However, silicon based electrodes suffer from rapid capacity degradation during electrochemical cycling. The capacity decay is predominantly caused by (i) cracking due to large volume variations during lithium insertion/extraction and (ii) surface degradation due to excessive solid electrolyte interface (SEI) formation. In this work, we demonstrate that coating of a-Si thin film with a Li-active, nanoporous SiOx layer can result in exceptional electrochemical performance in Li-ion battery. The SiOx layer provides improved cracking resistance to the thin film and prevent the active material loss due to excessive SEI formation, benefiting the electrode cycling stability. Half-cell experiments using this anode material show an initial reversible capacity of 2173 mAh g^-1 with an excellent coulombic efficiency of 90.9%. Furthermore, the electrode shows remarkable capacity retention of ~97% after 100 cycles at C/2 charging rate. The proposed anode architecture is free from Liinactive binders and conductive additives and provides mechanical stability during the charge/discharge process.展开更多
On account of the high theoretical capacity, high corrosion resistance, environmental benignity, abundant availability and low cost, the research on a-Fe_2O_3 has been gradually fastened on as promising anodes materia...On account of the high theoretical capacity, high corrosion resistance, environmental benignity, abundant availability and low cost, the research on a-Fe_2O_3 has been gradually fastened on as promising anodes materials toward lithium-ion batteries(LIBs). A high-performance anode for LIBs based on α-Fe_2O_3 nanoplates have been selectively prepared. The α-Fe_2O_3 nanoplates can be synthesized with iron ionbased ionic liquid as iron source and template. The α-Fe_2O_3 nanoplates as the anode of LIBs can display high capacity of around1950 mAh g^(-1) at 0.5 A g^(-1) which have exceeded the theoretical capacity of α-Fe_2O_3. On account of unique nanoplate structures and gum arabic as binder, the α-Fe_2O_3 nanoplates also exhibit high rate capability and excellent cycling performance.展开更多
Time-series-based forecasting is essential to determine how past events affect future events. This paper compares the performance accuracy of different time-series models for oil prices. Three types of univariate mode...Time-series-based forecasting is essential to determine how past events affect future events. This paper compares the performance accuracy of different time-series models for oil prices. Three types of univariate models are discussed: the exponential smoothing (ES), Holt-Winters (HW) and autoregressive intergrade moving average (ARIMA) models. To determine the best model, six different strategies were applied as selection criteria to quantify these models’ prediction accuracies. This comparison should help policy makers and industry marketing strategists select the best forecasting method in oil market. The three models were compared by applying them to the time series of regular oil prices for West Texas Intermediate (WTI) crude. The comparison indicated that the HW model performed better than the ES model for a prediction with a confidence interval of 95%. However, the ARIMA (2, 1, 2) model yielded the best results, leading us to conclude that this sophisticated and robust model outperformed other simple yet flexible models in oil market.展开更多
A simple but useful method of analysis of hyperbolic processes is presented and its application is illustrated by using the growth of human population in Africa, the economic growth in Western Europe and the examinati...A simple but useful method of analysis of hyperbolic processes is presented and its application is illustrated by using the growth of human population in Africa, the economic growth in Western Europe and the examination of the fundamental postulates of the Unified Growth Theory. It is shown how this method can revolutionize the interpretation of the historical economic growth and the growth of human population and how it can help to understand the current growth. Examples used to illustrate the application of this method show that, contrary to the accepted interpretations, the Industrial Revolution and the accompanying unprecedented technological development had no impact on the economic growth even in Western Europe and that Galor’s Unified Growth Theory fails the scientific test.展开更多
The use of benthic indicators has increased dramatically during the last decades. The number of articles published on the subject, as well as the number of citations, has been particularly increasing since the early 9...The use of benthic indicators has increased dramatically during the last decades. The number of articles published on the subject, as well as the number of citations, has been particularly increasing since the early 90’s, notably in relation with the implementation of directives for the management of aquatic/marine ecosystems such as the Water Framework Directive and the Marine Strategy Framework Directive. Current benthic indicators suffer from severe drawbacks and their practical use is still discussed and might have reached a dead end. Indicators based on species composition are not totally satisfactory, mainly because they exhibit a high spatio-temporal variability (e.g. variable at both seasonal and pluri-annual scales) and are user-dependent (e.g. divergent results from US orEuropeexperts.) In turn, modifications of behaviour, metabolism, phenotype or stable isotopes composition in invertebrates usually occur at short time scales, compared to detectable changes in community composition, and makes their use particularly relevant as indicators of perturbation. It is argued in this paper that these functional indicators might be relatively quickly implemented in the intertidal, and represent an effective alternative to current benthic indicators.展开更多
Restoration of grassland such as exclusion of grazing has been considered to increase aboveground plant diversity and soil fertility. However, knowledge on the effect of long-term exclusion of grazing on soil bacteria...Restoration of grassland such as exclusion of grazing has been considered to increase aboveground plant diversity and soil fertility. However, knowledge on the effect of long-term exclusion of grazing on soil bacterial community structure and diversity is not well understood. The two sites were selected in the Inner Mongolian grassland, i.e., one fenced off since 1979 (UG79) and the other continually grazed by sheep (FG) all along. Soil microbial biomass was measured using fumigation method and bacterial community structure and diversity were assessed using methods of Denaturing Gradient Gel Electrophoresis (DGGE) and clone library. Results showed that the UG79 soil had significantly higher microbial biomass carbon and nitrogen compared with the FG soil. There was a clear separation in soil bacterial community structure, but not in bacterial diversity between the two sites. Moreover, 55 clones from the UG79 soil and 56 clones from the FG soil were selected and sequenced. Phylogenetic analysis of all clone sequences indicated that bacterial communities were dominated by the groups of Actinomycetes, Proteobacteria and Bacteroidetes, but there were no significant differences in bacterial diversity between the two sites, consistent with the results obtained from DGGE. The results highlighted that although long-term exclusion of grazing increased soil microbial biomass, but it did not harbor higher bacterial diversity compared with freely grazed site.展开更多
To understand the research trends and areas of focus on the grassland degradation(GD),a bibliometric study based on the Science Citation Index-Expanded(SCI-E)was performed.This study presented a comprehensive overview...To understand the research trends and areas of focus on the grassland degradation(GD),a bibliometric study based on the Science Citation Index-Expanded(SCI-E)was performed.This study presented a comprehensive overview of the field based on the annual papers,research areas,temporal trends in keywords,marked journals,institutions,and authors.In the SCI-E database,GD publications first appeared in1970.Thus,we chose the study period between 1970 and 2020.The results showed that the annual number of publications increased in exponential model,with an especially rapid increase after 2009.Dong S.K.,Wang S.P.,and Liu S.L.were the most competitive authors based on their large numbers of papers and citations.A keyword analysis indicated that“grazing,alpine grassland,soil carbon and nitrogen,plant diversity,vegetation restoration”was the most popular study area.The institution with the greatest research publications and most citations was the Chinese Academy of Sciences.Journal of Arid Environments was one of the most popular journals for researchers to publish their research and had greater influence in the field with larger citations than other journals.Environmental science and ecology,soil science,plant science,biodiversity protection,geoscience,and water resources were the most popular Web of Science research areas.The keywords knowledge map mainly divides into four clusters,which are“vegetation”,“soil carbon”,“climate change”,and“grazing”.The ten clusters of the author’s co-occurrence analysis showed that the research areas of GD mainly concentrate on alpine grassland of Qinghai Tibetan Plateau and temperate steppe of Inner Mongolia.Especially under global climate change and the increasing human activities,they were continually increasing close attention to the present.The research methods are mainly in the combination of micro and macro view,such as high-throughput sequencing of the microbial community,remote sensing,quantitative analysis of models,etc.The current international research frontiers are alpine meadow degradation and the assessment of ecosystem service in degraded grassland.To distinguish human activities and climate change to the GD rate is also a new research hotspot in recent years.As the first bibliometrics paper in GD,this paper presents an attempt to better understanding of the progress on GD research.展开更多
Aims Quantifying the relative importance of the mechanisms that drive community assembly in forests is a crucial issue in community ecol-ogy.The present study aims to understand the ways in which niche-based and spati...Aims Quantifying the relative importance of the mechanisms that drive community assembly in forests is a crucial issue in community ecol-ogy.The present study aims to understand the ways in which niche-based and spatially based processes influence community assembly in areas in different climatic conditions and how these processes change during the transition from seedling to adult.Methods In this study,we investigated how taxonomic and phylogenetic beta diversity in seedling and adult stages of forest trees change across three elevational transects in tropical,subtropical and subalpine for-ests in Southwest China,and the relationships of these changes to the environment and inter-site distances.We quantified the relative contribution of environmental conditions and spatial distribution to taxonomic and phylogenetic beta diversity of both seedling and adult life stages along each elevational transect.We also quantified the taxonomic and phylogenetic similarity between seedlings and adult trees along elevations.Important Findings Taxonomic and phylogenetic beta diversity of both seedlings and adult trees increased with an increase in both environmental distance and spatial distance in all three transects.On both taxonomic and phylo-genetic levels,the effects of environmental filtering and spatial dispos-ition varied between life stages and among forest types.Phylogenetic similarity between seedlings and adult trees increased with elevation,although the taxonomic similarity did not show clear elevational pat-terns.Our results suggest that the relative contribution of niche-based and space-based processes to taxonomic and phylogenetic assem-blages varies across major plant life stages and among forest types.Our findings also highlight the importance of ontogenetic stages for fully understanding community assembly of long-lived tree species.展开更多
基金European Community financial participation for the Integrated Project(NUE-CROPSFP7-CP-IP222645)现代农业产业技术体系建设专项资金(CARS-03)中央级公益性科研院所基本科研业务费专项资金(202-14)资助
基金Supported by National Natural Science Foundation of China(No.31070409)the Agricultural and Forestry Promotion Fund of Nanhai Agroforestry Extension Centre,Guangdong Province(No.084101001)
基金supported by the Australian Research Council Future FellowshipDiscovery Projects and Griffith University Ph.D. Scholarships
文摘Extensive efforts have been devoted to the design of micro-, nano-, and/or molecular structures of sulfur hosts to address the challenges of lithium–sulfur(Li–S) batteries, yet comparatively little research has been carried out on the binders in Li–S batteries. Herein, we systematically review the polymer composite frameworks that confine the sulfur within the sulfur electrode, taking the roles of sulfur hosts and functions of binders into consideration. In particular, we investigate the binding mechanism between the binder and sulfur host(such as mechanical interlocking and interfacial interactions), the chemical interactions between the polymer binder and sulfur(such as covalent bonding, electrostatic bonding, etc.), as well as the beneficial functions that polymer binders can impart on Li–S cathodes, such as conductive binders, electrolyte intake, adhesion strength etc. This work could provide a more comprehensive strategy in designing sulfur electrodes for long-life, large-capacity and high-rate Li–S battery.
基金supported by the National Key Basic Research Program of China (2014CB954100)Yunnan Provincial Foundation of Science and Technology (2014GA003)the QueenslandChinese Academy of Sciences Biotechnology Fund(GJHZ1130)
文摘Soil seed banks are a vital part of ecosystems and influence community dynamics and regeneration.Although soil seed banks in different habitats have been reported, how soil seed banks vary with elevational gradients in different climatic zones is still unknown. This paper investigates seed density,species composition and nonconstituent species of forest soil seed banks in Yunnan Province, southwest China. Similarity between the soil seed bank and standing vegetation was also examined. We collected soil samples from sites spanning 12 elevations in tropical rain forests, subtropical evergreen broadleaved forests and subalpine coniferous forests, and transported them to a glasshouse for germination trials for species identification. The soil seed banks of tropical and subtropical forests had much higher seed densities and species richness than those of subalpine forests. Seeds of woody species dominated the soil seed banks of tropical and subtropical forests, while herbs dominated those of subalpine forests.The nonconstituent species in the soil seed banks were all herbs and were most abundant in tropical forests, followed by subtropical forests but were completely absent from subalpine forests.
基金financial support from ARC Discovery Projects (DP150101717 and DP180102003)
文摘Silicon is a promising anode material for rechargeable Li-ion battery (LIB) due to its high energy density and relatively low operating voltage. However, silicon based electrodes suffer from rapid capacity degradation during electrochemical cycling. The capacity decay is predominantly caused by (i) cracking due to large volume variations during lithium insertion/extraction and (ii) surface degradation due to excessive solid electrolyte interface (SEI) formation. In this work, we demonstrate that coating of a-Si thin film with a Li-active, nanoporous SiOx layer can result in exceptional electrochemical performance in Li-ion battery. The SiOx layer provides improved cracking resistance to the thin film and prevent the active material loss due to excessive SEI formation, benefiting the electrode cycling stability. Half-cell experiments using this anode material show an initial reversible capacity of 2173 mAh g^-1 with an excellent coulombic efficiency of 90.9%. Furthermore, the electrode shows remarkable capacity retention of ~97% after 100 cycles at C/2 charging rate. The proposed anode architecture is free from Liinactive binders and conductive additives and provides mechanical stability during the charge/discharge process.
基金financially supported by the National Natural Science Foundation of China (No.21506081,21506077)Jiangsu University Scientific Research Funding (15JDG048)+1 种基金Chinese Postdoctoral Foundation (2016M590420)Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘On account of the high theoretical capacity, high corrosion resistance, environmental benignity, abundant availability and low cost, the research on a-Fe_2O_3 has been gradually fastened on as promising anodes materials toward lithium-ion batteries(LIBs). A high-performance anode for LIBs based on α-Fe_2O_3 nanoplates have been selectively prepared. The α-Fe_2O_3 nanoplates can be synthesized with iron ionbased ionic liquid as iron source and template. The α-Fe_2O_3 nanoplates as the anode of LIBs can display high capacity of around1950 mAh g^(-1) at 0.5 A g^(-1) which have exceeded the theoretical capacity of α-Fe_2O_3. On account of unique nanoplate structures and gum arabic as binder, the α-Fe_2O_3 nanoplates also exhibit high rate capability and excellent cycling performance.
文摘Time-series-based forecasting is essential to determine how past events affect future events. This paper compares the performance accuracy of different time-series models for oil prices. Three types of univariate models are discussed: the exponential smoothing (ES), Holt-Winters (HW) and autoregressive intergrade moving average (ARIMA) models. To determine the best model, six different strategies were applied as selection criteria to quantify these models’ prediction accuracies. This comparison should help policy makers and industry marketing strategists select the best forecasting method in oil market. The three models were compared by applying them to the time series of regular oil prices for West Texas Intermediate (WTI) crude. The comparison indicated that the HW model performed better than the ES model for a prediction with a confidence interval of 95%. However, the ARIMA (2, 1, 2) model yielded the best results, leading us to conclude that this sophisticated and robust model outperformed other simple yet flexible models in oil market.
文摘A simple but useful method of analysis of hyperbolic processes is presented and its application is illustrated by using the growth of human population in Africa, the economic growth in Western Europe and the examination of the fundamental postulates of the Unified Growth Theory. It is shown how this method can revolutionize the interpretation of the historical economic growth and the growth of human population and how it can help to understand the current growth. Examples used to illustrate the application of this method show that, contrary to the accepted interpretations, the Industrial Revolution and the accompanying unprecedented technological development had no impact on the economic growth even in Western Europe and that Galor’s Unified Growth Theory fails the scientific test.
文摘The use of benthic indicators has increased dramatically during the last decades. The number of articles published on the subject, as well as the number of citations, has been particularly increasing since the early 90’s, notably in relation with the implementation of directives for the management of aquatic/marine ecosystems such as the Water Framework Directive and the Marine Strategy Framework Directive. Current benthic indicators suffer from severe drawbacks and their practical use is still discussed and might have reached a dead end. Indicators based on species composition are not totally satisfactory, mainly because they exhibit a high spatio-temporal variability (e.g. variable at both seasonal and pluri-annual scales) and are user-dependent (e.g. divergent results from US orEuropeexperts.) In turn, modifications of behaviour, metabolism, phenotype or stable isotopes composition in invertebrates usually occur at short time scales, compared to detectable changes in community composition, and makes their use particularly relevant as indicators of perturbation. It is argued in this paper that these functional indicators might be relatively quickly implemented in the intertidal, and represent an effective alternative to current benthic indicators.
文摘Restoration of grassland such as exclusion of grazing has been considered to increase aboveground plant diversity and soil fertility. However, knowledge on the effect of long-term exclusion of grazing on soil bacterial community structure and diversity is not well understood. The two sites were selected in the Inner Mongolian grassland, i.e., one fenced off since 1979 (UG79) and the other continually grazed by sheep (FG) all along. Soil microbial biomass was measured using fumigation method and bacterial community structure and diversity were assessed using methods of Denaturing Gradient Gel Electrophoresis (DGGE) and clone library. Results showed that the UG79 soil had significantly higher microbial biomass carbon and nitrogen compared with the FG soil. There was a clear separation in soil bacterial community structure, but not in bacterial diversity between the two sites. Moreover, 55 clones from the UG79 soil and 56 clones from the FG soil were selected and sequenced. Phylogenetic analysis of all clone sequences indicated that bacterial communities were dominated by the groups of Actinomycetes, Proteobacteria and Bacteroidetes, but there were no significant differences in bacterial diversity between the two sites, consistent with the results obtained from DGGE. The results highlighted that although long-term exclusion of grazing increased soil microbial biomass, but it did not harbor higher bacterial diversity compared with freely grazed site.
基金This research is supported by the International Partnership Program of Chinese Academy of Sciences(Grant No.121311KYSB20170004-04)land the CAS Strategic Priority Research Programme,Grant(No.XDA20050103).
文摘To understand the research trends and areas of focus on the grassland degradation(GD),a bibliometric study based on the Science Citation Index-Expanded(SCI-E)was performed.This study presented a comprehensive overview of the field based on the annual papers,research areas,temporal trends in keywords,marked journals,institutions,and authors.In the SCI-E database,GD publications first appeared in1970.Thus,we chose the study period between 1970 and 2020.The results showed that the annual number of publications increased in exponential model,with an especially rapid increase after 2009.Dong S.K.,Wang S.P.,and Liu S.L.were the most competitive authors based on their large numbers of papers and citations.A keyword analysis indicated that“grazing,alpine grassland,soil carbon and nitrogen,plant diversity,vegetation restoration”was the most popular study area.The institution with the greatest research publications and most citations was the Chinese Academy of Sciences.Journal of Arid Environments was one of the most popular journals for researchers to publish their research and had greater influence in the field with larger citations than other journals.Environmental science and ecology,soil science,plant science,biodiversity protection,geoscience,and water resources were the most popular Web of Science research areas.The keywords knowledge map mainly divides into four clusters,which are“vegetation”,“soil carbon”,“climate change”,and“grazing”.The ten clusters of the author’s co-occurrence analysis showed that the research areas of GD mainly concentrate on alpine grassland of Qinghai Tibetan Plateau and temperate steppe of Inner Mongolia.Especially under global climate change and the increasing human activities,they were continually increasing close attention to the present.The research methods are mainly in the combination of micro and macro view,such as high-throughput sequencing of the microbial community,remote sensing,quantitative analysis of models,etc.The current international research frontiers are alpine meadow degradation and the assessment of ecosystem service in degraded grassland.To distinguish human activities and climate change to the GD rate is also a new research hotspot in recent years.As the first bibliometrics paper in GD,this paper presents an attempt to better understanding of the progress on GD research.
基金This research was supported by the National Natural Science Foundation of China(31400362 and 31670442)National Key Basic Research Program of China(2014CB954100)+2 种基金the West Light Foundation of the Chinese Academy of Sciences,the Chinese Academy of Sciences Youth Innovation Promotion Association(2016352)the Queensland-Chinese Academy of Sciences Biotechnology Fund(GJHZ1130)the Applied Fundamental Research Foundation of Yunnan Province(2014GA003 and 2013FB079).
文摘Aims Quantifying the relative importance of the mechanisms that drive community assembly in forests is a crucial issue in community ecol-ogy.The present study aims to understand the ways in which niche-based and spatially based processes influence community assembly in areas in different climatic conditions and how these processes change during the transition from seedling to adult.Methods In this study,we investigated how taxonomic and phylogenetic beta diversity in seedling and adult stages of forest trees change across three elevational transects in tropical,subtropical and subalpine for-ests in Southwest China,and the relationships of these changes to the environment and inter-site distances.We quantified the relative contribution of environmental conditions and spatial distribution to taxonomic and phylogenetic beta diversity of both seedling and adult life stages along each elevational transect.We also quantified the taxonomic and phylogenetic similarity between seedlings and adult trees along elevations.Important Findings Taxonomic and phylogenetic beta diversity of both seedlings and adult trees increased with an increase in both environmental distance and spatial distance in all three transects.On both taxonomic and phylo-genetic levels,the effects of environmental filtering and spatial dispos-ition varied between life stages and among forest types.Phylogenetic similarity between seedlings and adult trees increased with elevation,although the taxonomic similarity did not show clear elevational pat-terns.Our results suggest that the relative contribution of niche-based and space-based processes to taxonomic and phylogenetic assem-blages varies across major plant life stages and among forest types.Our findings also highlight the importance of ontogenetic stages for fully understanding community assembly of long-lived tree species.
