Among all the renewable energy sources,the installed capacity of solar power generation is the fastest growing in recent years,so photovoltaic(PV)power generation still has great market potential.Compared with low-pow...Among all the renewable energy sources,the installed capacity of solar power generation is the fastest growing in recent years,so photovoltaic(PV)power generation still has great market potential.Compared with low-power systems,large-scale PV systems are more commercially attractive,because they can reduce the cost of the system per watt.The PV inverters with centralized and string structure have been applied in large-scale PV plant,but it is difficult to further increase the voltage and power levels for a single converter.In addition,the line-frequency isolation transformer requires a large amount of materials and has a large volume and weight.Therefore,it is a current trend for large-scale PV system to increase the voltage and power levels to directly connect to the medium-voltage power grid.Based on this,this paper investigates and compares several topologies of PV inverters without line-frequency transformer,including the MMC structure and the three-phase cascaded H-bridge(CHB)structure,which are able to directly connect to the 35kV medium-voltage power grid,and can not only make the voltage and power levels higher,but also further reduce the cost and volume of the whole system.展开更多
Background and aims:Hepatocellular carcinoma(HCC)is a prevalent malignancy with poor prognosis.This study uses integrated bioinformatic analyses to explore potential competing endogenous RNA(ceRNA)network chains in HC...Background and aims:Hepatocellular carcinoma(HCC)is a prevalent malignancy with poor prognosis.This study uses integrated bioinformatic analyses to explore potential competing endogenous RNA(ceRNA)network chains in HCC.Methods:HCC expression profile data were obtained from the Gene Expression Omnibus dataset,and differential expression analysis was conducted to identify differentially expressed mRNAs(DEmRNAs),microRNAs(DEmiRNAs),and long non-coding RNAs(DElncRNAs)between HCC and normal liver tissue samples.Univariate Cox regression analysis was performed to identify mRNAs associated with the prognosis of HCC patients.Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were used to classify the identified genes functionally.Cytoscape software was used to construct a protein–protein interaction network.Using the intersection method,a ceRNA network was established to align data from two databases(miRTarBase and miRcode).Pearson correlation analysis was conducted to evaluate the relationships between lncRNAs and mRNAs.Results:A total of 106 prognosis-related DEmRNAs were identified between HCC and normal samples.A total of 132 DEmiRNAs and 42 DElncRNAs were dysregulated in HCC.A ceRNA network of three lncRNAs,six miRNAs,and eight mRNAs was constructed.High expression of MCM10,CDKN3,RRM2,KIF3A,and ALYREF correlated with a poor prognosis,while high expression of CPEB2,COLEC10,and PBLD was associated with a better prognosis for HCC patients.Expression analysis confirmed the differential expression of these genes in HCC samples.Correlation analysis revealed that a MAGI2-AS3/hsa-miR-450b-5p/COLEC10 axis might play a crucial role in the progression of HCC.Conclusion:The ceRNA network constructed could provide insight into HCC tumorigenesis and might lead to new molecular biomarkers for diagnosing and treating HCC.展开更多
Recent research on photothermal therapy(PTT) has sparked significant interest in the development of new organic photothermal agents(PTAs),ranging from single-molecule to aggregated levels.However,controlling aggregati...Recent research on photothermal therapy(PTT) has sparked significant interest in the development of new organic photothermal agents(PTAs),ranging from single-molecule to aggregated levels.However,controlling aggregation pathways for PTAs with ultrahigh photothermal conversion efficiency(PCE) remains a major challenge.Herein,a two-pronged approach utilizing “Haggregation” and “intramolecular motion” was employed to enhance the PCE of an acceptor-substituted squaraine dye(NSQs).The C2vmolecular symmetry of the NSQs,which possess a ground state dipole moment(μg),promotes H-dimeric aggregates through dipole-dipole counteraction.Peripheral triphenylethylene or diphenylamine groups were added to this H-dimeric nanoplatform.This was done to enhance intramolecular motions for heat generation and also to extend conjugation,which redshifted the optical absorption and balanced the blue-shift induced by H-aggregation.With this technique,an organic PTA with NIR-II absorption was developed,and its nanoparticle achieved a remarkable PCE of 86.3% under 1,064 nm laser excitation.Femtosecond transient absorption spectroscopy and quantum mechanical calculations demonstrated the accelerated internal conversion process in NIR-II PTAs for rapid heat generation.The NSQs nanoparticles exhibit superior photothermal therapeutic properties for in vivo photoacoustic imaging-guided PTT,demonstrating the potential of bottom-up design to enable synergistic engineering strategies towards efficient phototheranostic agents.展开更多
Hepatocellular carcinoma(HCC)has emerged as a formidable global health challenge since it ranks the sixth most common malignant tumor and the third most common cause of cancer-related death(1).One of the most importan...Hepatocellular carcinoma(HCC)has emerged as a formidable global health challenge since it ranks the sixth most common malignant tumor and the third most common cause of cancer-related death(1).One of the most important factors in the creation of the increased incidence of HCC is the increasing rate of metabolic syndrome(MS),which is a complex interaction of metabolic abnormalities represented by obesity,insulin resistance,dyslipidemia,and hypertension.It was believed that chronic hepatitis B and C were one of the major etiologies of HCC,but additionally,the changed landscape of etiology now points toward MS and its comorbidities,such as non-alcoholic fatty liver disease,as major contributors in promotion of development and progress of HCC(2,3).展开更多
The Serling Co region is located at the transitional zone of the interaction between the Indian monsoon and the westerlies over the Tibetan Plateau. The Serling Co lake covers a water area of2,389 km2(June 2017) in a ...The Serling Co region is located at the transitional zone of the interaction between the Indian monsoon and the westerlies over the Tibetan Plateau. The Serling Co lake covers a water area of2,389 km2(June 2017) in a 45,530 km2drainage basin. Under the dramatic hydro-meteorological changes on the Tibetan Plateau in recent decades, and complex hydrological compositions of rivers and lakes in the basin, the lake area expanded by 43%, from1,667 km2in 1976, to 2,389 km2in 2017 (1)In 2014 it surpassed Nam Co as the largest lake on the Tibetan Plateau [2], and exerts significant effect on regional environmental conditions.展开更多
Widespread lakes on the Tibetan Plateau(TP)are valuable archives for investigating climate and environment changes, which could provide essential information on the mechanisms of past climate changes on the TP and the...Widespread lakes on the Tibetan Plateau(TP)are valuable archives for investigating climate and environment changes, which could provide essential information on the mechanisms of past climate changes on the TP and their interaction with the global climate systems.However, there is a lack of in-depth investigation of modern limnological processes in the Tibetan lakes, which hampers the understanding of paleolimnological records and lake ecosystem succession. In this study, we performed continuous temperature monitoring at two lakes, Bangong Co, a freshwater lake in the western TP, and Dagze Co, a brackish lake in the central TP, in order to characterize the patterns of seasonal temperature variability, stratification,and mixing. Temperature data for an entire hydrological year demonstrate that Bangong Co is a dimictic lake and that Dagze Co is a meromictic lake. The higher salinity in the deep water at Dagze Co prevents the lake from overturning completely, and this finding is supported by simulations using a physical limnological model Lake Analyzer. Continuous lake water temperature monitoring provides fundamental data for classifying Tibetan lakes, as well as the hydrological basis for understanding their paleolimnological records and ecosystem succession.展开更多
The Tibetan Plateau(TP)is home to about 1400 lakes with areas greater than 1 km2[1].A trend towards warmer and wetter conditions on the TP has resulted in substantial expansion of the lake area since the mid-1990s,whi...The Tibetan Plateau(TP)is home to about 1400 lakes with areas greater than 1 km2[1].A trend towards warmer and wetter conditions on the TP has resulted in substantial expansion of the lake area since the mid-1990s,which has attracted widespread attention[1-3].Meanwhile,climate change can alter lake ice duration and lake mixing regimes[4].展开更多
We present a quantitative mean annual air temperature(MAAT)record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers(brGDGTs)from a sediment core from Xiada Co,an alpi...We present a quantitative mean annual air temperature(MAAT)record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers(brGDGTs)from a sediment core from Xiada Co,an alpine lake on the western Tibetan Plateau(TP).The record indicates a relatively stable and warm MAAT until 2200 cal yr BP;subsequently,the MAAT decreased by~4.4℃at~2100 cal yr BP and maintained a cooling trend until the present day,with centennial-scale oscillations centered at~800 cal yr BP,~600 cal yr BP,and~190-170 cal yr BP.MAAT decreased abruptly at~500-300 cal yr BP and reached its minimum for the past 4700 years.We assessed the representativeness of our record by comparing it with 15 published paleotemperature records from the TP spanning the past~5000 years.The results show divergent temperature variations,including a gradual cooling trend,a warming trend,and no clear trend.We suggest that these discrepancies could be caused by factors such as the seasonality of the temperature proxies,the length of the freezing season of the lakes,the choice of proxy-temperature calibrations,and chronological errors.Our results highlight the need for more high-quality paleotemperature reconstructions with unambiguous climatic significance,clear seasonality,site-specific calibration,and robust dating,to better understand the processes,trends,and mechanisms of Holocene temperature changes on the TP.展开更多
Long-chain n-alkanes are one of the most common organic compounds in terrestrial plants and they are well-preserved in various geological archives.n-alkanes are relatively resistant to degradation and thus they can pr...Long-chain n-alkanes are one of the most common organic compounds in terrestrial plants and they are well-preserved in various geological archives.n-alkanes are relatively resistant to degradation and thus they can provide high-fidelity records of past vegetation and climate changes.Nevertheless,previous studies have shown that the interpretation of n-alkane proxies,such as the average chain length(ACL),is often ambiguous since this proxy depends on more than one variable.Both vegetation and climate could exert controls on the n-alkane ACL,and hence its interpretation requires careful consideration,especially in regions like the Qinghai-Tibet Plateau(QTP)where topography,biome type and moisture source are highly variable.To further evaluate the influences of vegetation and climate on the ACL in high-elevation lakes,we examined the n-alkane distributions of the surface sediments of 55 lakes across the QTP.Our results show that the ACL across a climatic gradient is significantly affected by precipitation,rather than by temperature.The positive correlation between ACL and precipitation may be because of the effect of microbial degradation during deposition.Finally,we suggest that more caution is needed in the interpretation of ACL data in different regions.展开更多
The Yarlung Tsangpo,the longest river in the southern Tibetan Plateau(TP),has attracted much research attention aimed at understanding the factors controlling its modern hydrology and possible future discharge in the ...The Yarlung Tsangpo,the longest river in the southern Tibetan Plateau(TP),has attracted much research attention aimed at understanding the factors controlling its modern hydrology and possible future discharge in the context of ongoing climate change.However,partly due to the complex regional climatic background,no consistent conclusions have been reached,especially for its upper reaches.Paleohydrological reconstructions of the source region of the Yarlung Tsangpo can potentially improve our understanding of the history of humidity and its response to climatic variability.In this study,we used a 97 cm gravity core from Gongzhu Co to reconstruct the hydrology change during the late Holocene.The core was dated using AMS^(14)C and Pb/Cs methods,and we used measurements of element contents(determined by high-resolution XRF scanning),grain size,IC/TOC,and magnetic susceptibility to reconstruct hydroclimatic changes in the source of the Yarlung Tsangpo watershed since~4000 yr ago.Combined with a modern meteorological data set,we found that PC1 of the XRF data,the Ca/(Fe+Ti)ratio,and EM1 of the grain size data were indicative of changes in humidity.Our records demonstrate a wet interval during~4-1.7 ka BP(ka=1000 yr,BP represents years before 1950 AD),followed by a dry period during since~1 ka BP.Comparison with independent regional paleoclimatic records revealed shifts in the dominant factors controlling humidity.The wet interval during~4-1.7 ka BP was coeval with a strengthened Westerlies,implying a dominant moisture supply from northern high latitudes.However,the extremely low values of Ca/(Fe+Ti)ratio during~4-2.5 ka BP indicate potential glacial freshwater source,which is corroborated by the concurrent high magnetic susceptibility values and increased grain size.The rapid drying trend during~1.7-1 ka BP suggests a switch in moisture supply from the Westerlies to the Indian Summer Monsoon(ISM).We attribute the drought conditions after~1 ka BP to a weakened ISM,although a Westerlies influence and the potential effect of high temperatures on evaporation cannot be excluded.We suggest that future hydroclimatic research in this region should attempt to distinguish the individual moisture contributions of the ISM and the Westerlies during the last millennium.展开更多
Investigating the dynamics of vegetation is an essential basis to know how to protect ecological environments and to help predict any changes in trend.Because of its fragile alpine ecosystem,the Tibetan Plateau is a p...Investigating the dynamics of vegetation is an essential basis to know how to protect ecological environments and to help predict any changes in trend.Because of its fragile alpine ecosystem,the Tibetan Plateau is a particularly suitable area for studying vegetation changes and their driving factors.In this study,we present a high-resolution pollen record covering the last two centuries extracted from Gongzhu Co on the western Tibetan Plateau.Alpine steppe is the predominant vegetation type in the surrounding area throughout the past 250 years with stable vegetation composition and abundance,as revealed by pollen spectra dominated by Artemisia,Ranunculaceae,Cyperaceae,and Poaceae.Detrended canonical correspondence analysis(DCCA)of the pollen data reveals low turnover in compositional species(0.41 SD),suggesting that the vegetation in the Gongzhu catchment had no significant temporal change,despite climate change and population increases in recent decades.We additionally ran DCCA on ten other pollen records from the Tibetan Plateau with high temporal resolution(1-20 years)covering recent centuries,and the results also show that compositional species turnover(0.15-0.81 SD)is relatively low,suggesting that the vegetation stability may have prevailed across the Tibetan Plateau during recent centuries.More high-resolution pollen records and high taxonomic-resolution palaeo-vegetation records(such as sedaDNA),however,are needed to confirm the vegetation stability on the Tibetan Plateau.展开更多
1Introduction.The Tibetan Plateau(TP)is the largest and highest terrain on the Earth,comprising more than 80%of continents higher than 4000 m above sea level.The extremely high elevation resulted in cold and arid clim...1Introduction.The Tibetan Plateau(TP)is the largest and highest terrain on the Earth,comprising more than 80%of continents higher than 4000 m above sea level.The extremely high elevation resulted in cold and arid climate,sparse vegetation,limited available water resources,thin oxygen on TP,as well as desolated landscape,which makes it one of the most unfriendly habitable places on the Earth.However,ancient humans lived on TP as early as 200 thousand years ago(Chen et al.,2019;Zhang et al.,2020),and developed ancient civilizations,including the Tibetan Empire,Guge Kingdom in historical periods.展开更多
基金This work was supported by National Natural Science Foundation of China(51937003).
文摘Among all the renewable energy sources,the installed capacity of solar power generation is the fastest growing in recent years,so photovoltaic(PV)power generation still has great market potential.Compared with low-power systems,large-scale PV systems are more commercially attractive,because they can reduce the cost of the system per watt.The PV inverters with centralized and string structure have been applied in large-scale PV plant,but it is difficult to further increase the voltage and power levels for a single converter.In addition,the line-frequency isolation transformer requires a large amount of materials and has a large volume and weight.Therefore,it is a current trend for large-scale PV system to increase the voltage and power levels to directly connect to the medium-voltage power grid.Based on this,this paper investigates and compares several topologies of PV inverters without line-frequency transformer,including the MMC structure and the three-phase cascaded H-bridge(CHB)structure,which are able to directly connect to the 35kV medium-voltage power grid,and can not only make the voltage and power levels higher,but also further reduce the cost and volume of the whole system.
基金funded by Special clinical project of Shanghai Municipal Health Commission(No.20224Y0299 and No.20244Y0233)National Natural Science Foundation Incubation Project(No.2022MS039 and 2022GZR005)+2 种基金the National Natural Science Foundation of China(82372813 for Wang MD)the Natural Science Foundation of Shanghai(No.22ZR1477900 for Wang MD)Shanghai Science and Technology Committee Rising-Star Program(No.22QA1411600 for Wang MD,24YF2758600 for Diao YK).
文摘Background and aims:Hepatocellular carcinoma(HCC)is a prevalent malignancy with poor prognosis.This study uses integrated bioinformatic analyses to explore potential competing endogenous RNA(ceRNA)network chains in HCC.Methods:HCC expression profile data were obtained from the Gene Expression Omnibus dataset,and differential expression analysis was conducted to identify differentially expressed mRNAs(DEmRNAs),microRNAs(DEmiRNAs),and long non-coding RNAs(DElncRNAs)between HCC and normal liver tissue samples.Univariate Cox regression analysis was performed to identify mRNAs associated with the prognosis of HCC patients.Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were used to classify the identified genes functionally.Cytoscape software was used to construct a protein–protein interaction network.Using the intersection method,a ceRNA network was established to align data from two databases(miRTarBase and miRcode).Pearson correlation analysis was conducted to evaluate the relationships between lncRNAs and mRNAs.Results:A total of 106 prognosis-related DEmRNAs were identified between HCC and normal samples.A total of 132 DEmiRNAs and 42 DElncRNAs were dysregulated in HCC.A ceRNA network of three lncRNAs,six miRNAs,and eight mRNAs was constructed.High expression of MCM10,CDKN3,RRM2,KIF3A,and ALYREF correlated with a poor prognosis,while high expression of CPEB2,COLEC10,and PBLD was associated with a better prognosis for HCC patients.Expression analysis confirmed the differential expression of these genes in HCC samples.Correlation analysis revealed that a MAGI2-AS3/hsa-miR-450b-5p/COLEC10 axis might play a crucial role in the progression of HCC.Conclusion:The ceRNA network constructed could provide insight into HCC tumorigenesis and might lead to new molecular biomarkers for diagnosing and treating HCC.
基金supported by the National Natural Science Foundation of China (22063005)the Natural Science Foundation of Jiangxi Province (20212ACBA203012,20224BAB214003,20232BAB-203031)the Interdisciplinary Innovation Fund of Natural Science,Nanchang University (9167-27060003-ZD2101,9167-28220007-YB2113)。
文摘Recent research on photothermal therapy(PTT) has sparked significant interest in the development of new organic photothermal agents(PTAs),ranging from single-molecule to aggregated levels.However,controlling aggregation pathways for PTAs with ultrahigh photothermal conversion efficiency(PCE) remains a major challenge.Herein,a two-pronged approach utilizing “Haggregation” and “intramolecular motion” was employed to enhance the PCE of an acceptor-substituted squaraine dye(NSQs).The C2vmolecular symmetry of the NSQs,which possess a ground state dipole moment(μg),promotes H-dimeric aggregates through dipole-dipole counteraction.Peripheral triphenylethylene or diphenylamine groups were added to this H-dimeric nanoplatform.This was done to enhance intramolecular motions for heat generation and also to extend conjugation,which redshifted the optical absorption and balanced the blue-shift induced by H-aggregation.With this technique,an organic PTA with NIR-II absorption was developed,and its nanoparticle achieved a remarkable PCE of 86.3% under 1,064 nm laser excitation.Femtosecond transient absorption spectroscopy and quantum mechanical calculations demonstrated the accelerated internal conversion process in NIR-II PTAs for rapid heat generation.The NSQs nanoparticles exhibit superior photothermal therapeutic properties for in vivo photoacoustic imaging-guided PTT,demonstrating the potential of bottom-up design to enable synergistic engineering strategies towards efficient phototheranostic agents.
文摘Hepatocellular carcinoma(HCC)has emerged as a formidable global health challenge since it ranks the sixth most common malignant tumor and the third most common cause of cancer-related death(1).One of the most important factors in the creation of the increased incidence of HCC is the increasing rate of metabolic syndrome(MS),which is a complex interaction of metabolic abnormalities represented by obesity,insulin resistance,dyslipidemia,and hypertension.It was believed that chronic hepatitis B and C were one of the major etiologies of HCC,but additionally,the changed landscape of etiology now points toward MS and its comorbidities,such as non-alcoholic fatty liver disease,as major contributors in promotion of development and progress of HCC(2,3).
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDA20020100)the Key Project of National Natural Science Foundation of China (41831177)+1 种基金China Ministry of Science and Technology Project (2018YFB05050000)the 13th Five-year Informatization Plan of Chinese Academy of Sciences (XXH13505-06)
文摘The Serling Co region is located at the transitional zone of the interaction between the Indian monsoon and the westerlies over the Tibetan Plateau. The Serling Co lake covers a water area of2,389 km2(June 2017) in a 45,530 km2drainage basin. Under the dramatic hydro-meteorological changes on the Tibetan Plateau in recent decades, and complex hydrological compositions of rivers and lakes in the basin, the lake area expanded by 43%, from1,667 km2in 1976, to 2,389 km2in 2017 (1)In 2014 it surpassed Nam Co as the largest lake on the Tibetan Plateau [2], and exerts significant effect on regional environmental conditions.
基金supported by the National Natural Science Foundation of China (41072120, 41321061)
文摘Widespread lakes on the Tibetan Plateau(TP)are valuable archives for investigating climate and environment changes, which could provide essential information on the mechanisms of past climate changes on the TP and their interaction with the global climate systems.However, there is a lack of in-depth investigation of modern limnological processes in the Tibetan lakes, which hampers the understanding of paleolimnological records and lake ecosystem succession. In this study, we performed continuous temperature monitoring at two lakes, Bangong Co, a freshwater lake in the western TP, and Dagze Co, a brackish lake in the central TP, in order to characterize the patterns of seasonal temperature variability, stratification,and mixing. Temperature data for an entire hydrological year demonstrate that Bangong Co is a dimictic lake and that Dagze Co is a meromictic lake. The higher salinity in the deep water at Dagze Co prevents the lake from overturning completely, and this finding is supported by simulations using a physical limnological model Lake Analyzer. Continuous lake water temperature monitoring provides fundamental data for classifying Tibetan lakes, as well as the hydrological basis for understanding their paleolimnological records and ecosystem succession.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program (2019QZKK0206)the National Natural Science Foundation of China (41701041, 41975125, and 41988101)。
文摘The Tibetan Plateau(TP)is home to about 1400 lakes with areas greater than 1 km2[1].A trend towards warmer and wetter conditions on the TP has resulted in substantial expansion of the lake area since the mid-1990s,which has attracted widespread attention[1-3].Meanwhile,climate change can alter lake ice duration and lake mixing regimes[4].
基金financially supported by the National Natural Science Foundation of China(Grant No.41901105)the Research and Practice Project of Teaching Reform in universities of Henan Province(No.2022SYJXLX062)+2 种基金the Key Scientific and Technological Research Project of Henan Province(No.222102320128)the Training Plan of young backbone teachers in Henan Colleges and universities(Nos.2020GGJS158,2023GGJS096)the Nanhu Scholars Program for Young Scholars of XYNU.
文摘We present a quantitative mean annual air temperature(MAAT)record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers(brGDGTs)from a sediment core from Xiada Co,an alpine lake on the western Tibetan Plateau(TP).The record indicates a relatively stable and warm MAAT until 2200 cal yr BP;subsequently,the MAAT decreased by~4.4℃at~2100 cal yr BP and maintained a cooling trend until the present day,with centennial-scale oscillations centered at~800 cal yr BP,~600 cal yr BP,and~190-170 cal yr BP.MAAT decreased abruptly at~500-300 cal yr BP and reached its minimum for the past 4700 years.We assessed the representativeness of our record by comparing it with 15 published paleotemperature records from the TP spanning the past~5000 years.The results show divergent temperature variations,including a gradual cooling trend,a warming trend,and no clear trend.We suggest that these discrepancies could be caused by factors such as the seasonality of the temperature proxies,the length of the freezing season of the lakes,the choice of proxy-temperature calibrations,and chronological errors.Our results highlight the need for more high-quality paleotemperature reconstructions with unambiguous climatic significance,clear seasonality,site-specific calibration,and robust dating,to better understand the processes,trends,and mechanisms of Holocene temperature changes on the TP.
基金financially supported by the National Natural Science Foundation of China(Grant No.42171159)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0601).
文摘Long-chain n-alkanes are one of the most common organic compounds in terrestrial plants and they are well-preserved in various geological archives.n-alkanes are relatively resistant to degradation and thus they can provide high-fidelity records of past vegetation and climate changes.Nevertheless,previous studies have shown that the interpretation of n-alkane proxies,such as the average chain length(ACL),is often ambiguous since this proxy depends on more than one variable.Both vegetation and climate could exert controls on the n-alkane ACL,and hence its interpretation requires careful consideration,especially in regions like the Qinghai-Tibet Plateau(QTP)where topography,biome type and moisture source are highly variable.To further evaluate the influences of vegetation and climate on the ACL in high-elevation lakes,we examined the n-alkane distributions of the surface sediments of 55 lakes across the QTP.Our results show that the ACL across a climatic gradient is significantly affected by precipitation,rather than by temperature.The positive correlation between ACL and precipitation may be because of the effect of microbial degradation during deposition.Finally,we suggest that more caution is needed in the interpretation of ACL data in different regions.
基金financially supported by the National Natural Science Foundation of China(Grant No.42025103)Basic Science Center for Tibetan Plateau Earth System(BSCTPES,NSFC project No.41988101)+1 种基金the Second Tibetan Plateau Scientific Expedition and Research program(No.2019QZKK0601)the Scientific Research Funding of Sichuan Normal University.
文摘The Yarlung Tsangpo,the longest river in the southern Tibetan Plateau(TP),has attracted much research attention aimed at understanding the factors controlling its modern hydrology and possible future discharge in the context of ongoing climate change.However,partly due to the complex regional climatic background,no consistent conclusions have been reached,especially for its upper reaches.Paleohydrological reconstructions of the source region of the Yarlung Tsangpo can potentially improve our understanding of the history of humidity and its response to climatic variability.In this study,we used a 97 cm gravity core from Gongzhu Co to reconstruct the hydrology change during the late Holocene.The core was dated using AMS^(14)C and Pb/Cs methods,and we used measurements of element contents(determined by high-resolution XRF scanning),grain size,IC/TOC,and magnetic susceptibility to reconstruct hydroclimatic changes in the source of the Yarlung Tsangpo watershed since~4000 yr ago.Combined with a modern meteorological data set,we found that PC1 of the XRF data,the Ca/(Fe+Ti)ratio,and EM1 of the grain size data were indicative of changes in humidity.Our records demonstrate a wet interval during~4-1.7 ka BP(ka=1000 yr,BP represents years before 1950 AD),followed by a dry period during since~1 ka BP.Comparison with independent regional paleoclimatic records revealed shifts in the dominant factors controlling humidity.The wet interval during~4-1.7 ka BP was coeval with a strengthened Westerlies,implying a dominant moisture supply from northern high latitudes.However,the extremely low values of Ca/(Fe+Ti)ratio during~4-2.5 ka BP indicate potential glacial freshwater source,which is corroborated by the concurrent high magnetic susceptibility values and increased grain size.The rapid drying trend during~1.7-1 ka BP suggests a switch in moisture supply from the Westerlies to the Indian Summer Monsoon(ISM).We attribute the drought conditions after~1 ka BP to a weakened ISM,although a Westerlies influence and the potential effect of high temperatures on evaporation cannot be excluded.We suggest that future hydroclimatic research in this region should attempt to distinguish the individual moisture contributions of the ISM and the Westerlies during the last millennium.
基金supported by the Basic Science Center for Tibetan Plateau Earth System(BSCTPES,NSFC project No.41988101)CAS Pioneer Hundred Talents Program(Xianyong Cao).
文摘Investigating the dynamics of vegetation is an essential basis to know how to protect ecological environments and to help predict any changes in trend.Because of its fragile alpine ecosystem,the Tibetan Plateau is a particularly suitable area for studying vegetation changes and their driving factors.In this study,we present a high-resolution pollen record covering the last two centuries extracted from Gongzhu Co on the western Tibetan Plateau.Alpine steppe is the predominant vegetation type in the surrounding area throughout the past 250 years with stable vegetation composition and abundance,as revealed by pollen spectra dominated by Artemisia,Ranunculaceae,Cyperaceae,and Poaceae.Detrended canonical correspondence analysis(DCCA)of the pollen data reveals low turnover in compositional species(0.41 SD),suggesting that the vegetation in the Gongzhu catchment had no significant temporal change,despite climate change and population increases in recent decades.We additionally ran DCCA on ten other pollen records from the Tibetan Plateau with high temporal resolution(1-20 years)covering recent centuries,and the results also show that compositional species turnover(0.15-0.81 SD)is relatively low,suggesting that the vegetation stability may have prevailed across the Tibetan Plateau during recent centuries.More high-resolution pollen records and high taxonomic-resolution palaeo-vegetation records(such as sedaDNA),however,are needed to confirm the vegetation stability on the Tibetan Plateau.
文摘1Introduction.The Tibetan Plateau(TP)is the largest and highest terrain on the Earth,comprising more than 80%of continents higher than 4000 m above sea level.The extremely high elevation resulted in cold and arid climate,sparse vegetation,limited available water resources,thin oxygen on TP,as well as desolated landscape,which makes it one of the most unfriendly habitable places on the Earth.However,ancient humans lived on TP as early as 200 thousand years ago(Chen et al.,2019;Zhang et al.,2020),and developed ancient civilizations,including the Tibetan Empire,Guge Kingdom in historical periods.
