The Dongnan Cu–Mo deposit,located in the southeast of the Zijinshan ore field(the largest porphyry–epithermal system in Southeast China),represents the complex magmatic and metallogenesis events in the region.The pe...The Dongnan Cu–Mo deposit,located in the southeast of the Zijinshan ore field(the largest porphyry–epithermal system in Southeast China),represents the complex magmatic and metallogenesis events in the region.The petrogenesis and metallogenesis of granitoids from the deposit are not determined,especially the interactions between ore-bearing(granodiorite porphyry)and barren samples(granodiorite and diorite).In the paper,the whole rock geochemical features shared a similar affinity to the middle-lower content and revealed that they derived from partial melting of the Cathaysian basement with the contribution of mantle materials,even represented that they generated in the plate subduction;LA-ICP-MS zircon U–Pb ages show that these granodiorites,granodioritic porphyry and diorite,were generated during 114–103 Ma.The ore-bearing samples mostly presented ε_(Hf)(t)of negative values(peak value is-4 to-3)with old two-stage Hf model ages(t_(DM)^(2))(peak value is 1.10–1.15 Ga),while the barren sample showed slightly negative ε_(Hf)(t)(peak value is-1 to 0)values with young t_(DM)^(2)(peak value is 1.00–1.05 Ga).The value of zircon Ce^(4+)/Ce^(3+)ratio mostly higher than 450 was first verified for the ore-bearing samples in the Dongnan Cu–Mo deposit,and the values of ore-bearing were found to be higher than those from the barren,which suggests that the ore-bearing formed in more oxidized parental magma with higher oxygen fugacity.Based on the geochemical characteristic of the element and isotope,we concluded that the Early Cretaceous multiphases magmatic activities,low melting temperature and low pressure of pluton,and high oxygen fugacity of zircon,were the favorable conditions for metallogenesis of Dongnan Cu–Mo deposit.展开更多
Background:The reputation system has been designed as an effective mechanism to reduce risks associated with online shopping for customers.However,it is vulnerable to rating fraud.Some raters may inject unfairly high ...Background:The reputation system has been designed as an effective mechanism to reduce risks associated with online shopping for customers.However,it is vulnerable to rating fraud.Some raters may inject unfairly high or low ratings to the system so as to promote their own products or demote their competitors.Method:This study explores the rating fraud by differentiating the subjective fraud from objective fraud.Then it discusses the effectiveness of blockchain technology in objective fraud and its limitation in subjective fraud,especially the rating fraud.Lastly,it systematically analyzes the robustness of blockchain-based reputation systems in each type of rating fraud.Results:The detection of fraudulent raters is not easy since they can behave strategically to camouflage themselves.We explore the potential strengths and limitations of blockchain-based reputation systems under two attack goals:ballot-stuffing and bad-mouthing,and various attack models including constant attack,camouflage attack,whitewashing attack and sybil attack.Blockchain-based reputation systems are more robust against bad-mouthing than ballot-stuffing fraud.Conclusions:Blockchain technology provides new opportunities for redesigning the reputation system.Blockchain systems are very effective in preventing objective information fraud,such as loan application fraud,where fraudulent information is fact-based.However,their effectiveness is limited in subjective information fraud,such as rating fraud,where the ground-truth is not easily validated.Blockchain systems are effective in preventing bad mouthing and whitewashing attack,but they are limited in detecting ballot-stuffing under sybil attack,constant attacks and camouflage attack.展开更多
Aerobic anoxygenic phototrophic bacteria(AAPB)repre sent a major group of bacterioplankton assemblages in many water systems and some are assumed to be closely associated with phytoplankton.However,studies on relation...Aerobic anoxygenic phototrophic bacteria(AAPB)repre sent a major group of bacterioplankton assemblages in many water systems and some are assumed to be closely associated with phytoplankton.However,studies on relationships between AAPB and cyanobacterial blooms are in scarcity.The dynamics of the abundance and diversity of AAPB was compared based on pufM gene in Meiliang Bay(featured by cyanobacterial blooms)and East Bay(featured by macrophyte)of Taihu Lake,a shallow subtropical lake in the East China plain.AAPB abundance was not significantly different between the two sites,and they were positively correlated with dissolved organic carbon(DOC)concentration.The ratios of AAPB to total bacteria varied from 3.4%to 11.5%and peaked in winter in both site s.No significant differences of AAPB community compositions were detected between the two sites,but there was a separation between warm seasons(June,August,and October)and cold seasons(December,February,and April).Rhizobiales and Limnohabitans-like pufM sequences were significantly contributors for the difference between two seasons,and specially enriched in cold seasons.Chlorophyll a(Ch1 a)and DOC were the most significant variables influencing the AAPB community structure.Furthermore,Porphyrobacter and Rhodospirillales-like pufM sequences were positively correlated with Ch1 a,indicating potential influence of cyanobacterial blooms on these AAPB taxa.These results suggested that diverse AAPB ecotypes coexisted in Taihu Lake,and their ecological role in carbon cycling in the lake may not be ignored.展开更多
Background:Methane(CH4)oxidation driven by soil aerobic methanotrophs demonstrates the capacity of grassland as a CH4 sink.Methods:In this study,we compared the oxidation characteristics of atmospheric-level and eleva...Background:Methane(CH4)oxidation driven by soil aerobic methanotrophs demonstrates the capacity of grassland as a CH4 sink.Methods:In this study,we compared the oxidation characteristics of atmospheric-level and elevated concentration(10%)CH4 in a typical grassland(steppe)on the Loess Plateau,an alpine meadow(meadow)on the Qinghai-Tibet Plateau,and an inland arid-area artificial grassland(pasture)in northwest China and investigated the communities of active methanotrophs and their contribution to CH4 oxidation using DNA-based stable-isotope probing and Illumina Miseq sequencing.Results:The results showed that the oxidation of atmospheric CH4 only occurred in steppe and meadow soils where the USCγgroup of methanotrophs was numerically dominant in the methanotroph community.Pasture soils,with their very low relative abundance of USCγ,did not show atmospheric CH4 oxidation.However,a DNA-stable isotope probing experiment with 10%CH4 indicated that conventional CH4 oxidizers(Methylocaldum and Methylocystis)rather than USCγcommunities assimilated significant amounts of 13CH4 for growth.Conclusions:The CH4 oxidation mechanisms in the three experimental grassland soils varied significantly.The USCγgroup may be obligate oligotrophic microorganisms or their growth requires specific unknown conditions.展开更多
Cyanobacteria,specifically Microcystis,usually form massive blooms in eutrophic freshwater lakes.Cyanobacterial samples were collected from eight sites of both Lake Taihu and Lake Chaohu in late summer to determine th...Cyanobacteria,specifically Microcystis,usually form massive blooms in eutrophic freshwater lakes.Cyanobacterial samples were collected from eight sites of both Lake Taihu and Lake Chaohu in late summer to determine the diversity and distribution pattern of cyanobacteria and Microcystis in large,shallow,entropic lakes with significant spatial heterogeneity and long-term Microcystis bloom.Molecular methods based on denaturing gradient gel electrophoresis and clone library analysis were used.A similar heterogeneous distribution pattern of cyanobacteria in both lakes was observed.Most parts of these two lakes with high trophic level were dominated by Microcystis.However,in the regions with low trophic levels as well as low concentrations of chlorophyll a,Synechococcus occupied a considerable percentage.Different morphospecies and genotypes dominated the bloom-forming Microcystis populations in these two lakes.Microcystis viridis and Microcystis novacekii were dominant in Lake Chaohu,whereas Microcystis flos-aquae was dominant in Lake Taihu.Only 2 of the13 Microcystis operational taxonomic units were shared between these two lakes.Analysis of molecular variance based on 16S to 23S internal transcribed spacer sequences indicated the significant genetic differentiation of Microcystis between these two lakes(F st = 0.19,p < 0.001).However,only 19.46% of the genetic variability was explained by the population variation between lakes,whereas most(80.54%) of the genetic variability occurred within the lakes.Phylogenetic analysis revealed no phylogeographic structure of Microcystis population in these two lakes,as illustrated by their cosmopolitan nature.Our results revealed that spatial heterogeneity within lakes has more impact on the cyanobacterial diversity than geographical isolation in a local scale.展开更多
Biological methane oxidation is a crucial process in the global carbon cycle that reduces methane emissions from paddy fields and natural wetlands into the atmosphere.However,soil organic carbon accumulation associate...Biological methane oxidation is a crucial process in the global carbon cycle that reduces methane emissions from paddy fields and natural wetlands into the atmosphere.However,soil organic carbon accumulation associated with microbial methane oxidation is poorly understood.Therefore,to investigate methane-derived carbon incorporation into soil organic matter,paddy soils originated from different parent materials(Inceptisol,Entisol,and Alfisol) were collected after rice harvesting from four major rice-producing regions in Bangladesh.Following microcosm incubation with 5%(volume/volume)^(13) CH_(4),soil^(13) C-atom abundances significantly increased from background level of 1.08% to 1.88%–2.78%,leading to a net methane-derived accumulation of soil organic carbon ranging from 120 to 307 mg kg^(-1).Approximately 23.6%–60.0% of the methane consumed was converted to soil organic carbon during microbial methane oxidation.The phylogeny of^(13) C-labeled pmoA(enconding the alpha subunit of the particulate methane monooxygenase) and 16 S rRNA genes further revealed that canonical α(type II) and γ(type I) Proteobacteria were active methane oxidizers.Members within the Methylobacter-and Methylosarcina-affiliated type Ia lineages dominated active methane-oxidizing communities that were responsible for the majority of methane-derived carbon accumulation in all three paddy soils,while Methylocystis-affiliated type IIa lineage was the key contributor in one paddy soil of Inceptisol origin.These results suggest that methanotroph-mediated synthesis of biomass plays an important role in soil organic matter accumulation.This study thus supports the concept that methanotrophs not only consume the greenhouse gas methane but also serve as a key biotic factor in maintaining soil fertility.展开更多
基金provided by the Opening Foundation of State Key Laboratory of Continental Dynamics(Grant No.21LCD08),Northwest University,China.
文摘The Dongnan Cu–Mo deposit,located in the southeast of the Zijinshan ore field(the largest porphyry–epithermal system in Southeast China),represents the complex magmatic and metallogenesis events in the region.The petrogenesis and metallogenesis of granitoids from the deposit are not determined,especially the interactions between ore-bearing(granodiorite porphyry)and barren samples(granodiorite and diorite).In the paper,the whole rock geochemical features shared a similar affinity to the middle-lower content and revealed that they derived from partial melting of the Cathaysian basement with the contribution of mantle materials,even represented that they generated in the plate subduction;LA-ICP-MS zircon U–Pb ages show that these granodiorites,granodioritic porphyry and diorite,were generated during 114–103 Ma.The ore-bearing samples mostly presented ε_(Hf)(t)of negative values(peak value is-4 to-3)with old two-stage Hf model ages(t_(DM)^(2))(peak value is 1.10–1.15 Ga),while the barren sample showed slightly negative ε_(Hf)(t)(peak value is-1 to 0)values with young t_(DM)^(2)(peak value is 1.00–1.05 Ga).The value of zircon Ce^(4+)/Ce^(3+)ratio mostly higher than 450 was first verified for the ore-bearing samples in the Dongnan Cu–Mo deposit,and the values of ore-bearing were found to be higher than those from the barren,which suggests that the ore-bearing formed in more oxidized parental magma with higher oxygen fugacity.Based on the geochemical characteristic of the element and isotope,we concluded that the Early Cretaceous multiphases magmatic activities,low melting temperature and low pressure of pluton,and high oxygen fugacity of zircon,were the favorable conditions for metallogenesis of Dongnan Cu–Mo deposit.
文摘Background:The reputation system has been designed as an effective mechanism to reduce risks associated with online shopping for customers.However,it is vulnerable to rating fraud.Some raters may inject unfairly high or low ratings to the system so as to promote their own products or demote their competitors.Method:This study explores the rating fraud by differentiating the subjective fraud from objective fraud.Then it discusses the effectiveness of blockchain technology in objective fraud and its limitation in subjective fraud,especially the rating fraud.Lastly,it systematically analyzes the robustness of blockchain-based reputation systems in each type of rating fraud.Results:The detection of fraudulent raters is not easy since they can behave strategically to camouflage themselves.We explore the potential strengths and limitations of blockchain-based reputation systems under two attack goals:ballot-stuffing and bad-mouthing,and various attack models including constant attack,camouflage attack,whitewashing attack and sybil attack.Blockchain-based reputation systems are more robust against bad-mouthing than ballot-stuffing fraud.Conclusions:Blockchain technology provides new opportunities for redesigning the reputation system.Blockchain systems are very effective in preventing objective information fraud,such as loan application fraud,where fraudulent information is fact-based.However,their effectiveness is limited in subjective information fraud,such as rating fraud,where the ground-truth is not easily validated.Blockchain systems are effective in preventing bad mouthing and whitewashing attack,but they are limited in detecting ballot-stuffing under sybil attack,constant attacks and camouflage attack.
基金Supported by the National Natural Science Foundation of China(Nos.31971449,31370509,31100363)the CAS-SAFEA International Partnership Program for Creative Research Teams(CN)(No.KZZD-EWTZ-08)the startup funds from Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences(No.NIGLAS2011QD05)。
文摘Aerobic anoxygenic phototrophic bacteria(AAPB)repre sent a major group of bacterioplankton assemblages in many water systems and some are assumed to be closely associated with phytoplankton.However,studies on relationships between AAPB and cyanobacterial blooms are in scarcity.The dynamics of the abundance and diversity of AAPB was compared based on pufM gene in Meiliang Bay(featured by cyanobacterial blooms)and East Bay(featured by macrophyte)of Taihu Lake,a shallow subtropical lake in the East China plain.AAPB abundance was not significantly different between the two sites,and they were positively correlated with dissolved organic carbon(DOC)concentration.The ratios of AAPB to total bacteria varied from 3.4%to 11.5%and peaked in winter in both site s.No significant differences of AAPB community compositions were detected between the two sites,but there was a separation between warm seasons(June,August,and October)and cold seasons(December,February,and April).Rhizobiales and Limnohabitans-like pufM sequences were significantly contributors for the difference between two seasons,and specially enriched in cold seasons.Chlorophyll a(Ch1 a)and DOC were the most significant variables influencing the AAPB community structure.Furthermore,Porphyrobacter and Rhodospirillales-like pufM sequences were positively correlated with Ch1 a,indicating potential influence of cyanobacterial blooms on these AAPB taxa.These results suggested that diverse AAPB ecotypes coexisted in Taihu Lake,and their ecological role in carbon cycling in the lake may not be ignored.
基金National Natural Science Foundation of China,Grant/Award Numbers:42277114,91751204,41877062。
文摘Background:Methane(CH4)oxidation driven by soil aerobic methanotrophs demonstrates the capacity of grassland as a CH4 sink.Methods:In this study,we compared the oxidation characteristics of atmospheric-level and elevated concentration(10%)CH4 in a typical grassland(steppe)on the Loess Plateau,an alpine meadow(meadow)on the Qinghai-Tibet Plateau,and an inland arid-area artificial grassland(pasture)in northwest China and investigated the communities of active methanotrophs and their contribution to CH4 oxidation using DNA-based stable-isotope probing and Illumina Miseq sequencing.Results:The results showed that the oxidation of atmospheric CH4 only occurred in steppe and meadow soils where the USCγgroup of methanotrophs was numerically dominant in the methanotroph community.Pasture soils,with their very low relative abundance of USCγ,did not show atmospheric CH4 oxidation.However,a DNA-stable isotope probing experiment with 10%CH4 indicated that conventional CH4 oxidizers(Methylocaldum and Methylocystis)rather than USCγcommunities assimilated significant amounts of 13CH4 for growth.Conclusions:The CH4 oxidation mechanisms in the three experimental grassland soils varied significantly.The USCγgroup may be obligate oligotrophic microorganisms or their growth requires specific unknown conditions.
基金supported by the National Major Scienceand Technology Program for Water Pollution Controland Treatment (No. 2008ZX07103-005)the National Basic Research Program (973) of China (No.2008CB418000)
文摘Cyanobacteria,specifically Microcystis,usually form massive blooms in eutrophic freshwater lakes.Cyanobacterial samples were collected from eight sites of both Lake Taihu and Lake Chaohu in late summer to determine the diversity and distribution pattern of cyanobacteria and Microcystis in large,shallow,entropic lakes with significant spatial heterogeneity and long-term Microcystis bloom.Molecular methods based on denaturing gradient gel electrophoresis and clone library analysis were used.A similar heterogeneous distribution pattern of cyanobacteria in both lakes was observed.Most parts of these two lakes with high trophic level were dominated by Microcystis.However,in the regions with low trophic levels as well as low concentrations of chlorophyll a,Synechococcus occupied a considerable percentage.Different morphospecies and genotypes dominated the bloom-forming Microcystis populations in these two lakes.Microcystis viridis and Microcystis novacekii were dominant in Lake Chaohu,whereas Microcystis flos-aquae was dominant in Lake Taihu.Only 2 of the13 Microcystis operational taxonomic units were shared between these two lakes.Analysis of molecular variance based on 16S to 23S internal transcribed spacer sequences indicated the significant genetic differentiation of Microcystis between these two lakes(F st = 0.19,p < 0.001).However,only 19.46% of the genetic variability was explained by the population variation between lakes,whereas most(80.54%) of the genetic variability occurred within the lakes.Phylogenetic analysis revealed no phylogeographic structure of Microcystis population in these two lakes,as illustrated by their cosmopolitan nature.Our results revealed that spatial heterogeneity within lakes has more impact on the cyanobacterial diversity than geographical isolation in a local scale.
基金financially supported by the National Natural Science Foundation of China (Nos. 91751204, 41630862, 41701302, 41530857, and 41877062)The first author, Ms. Nasrin Sultana, gratefully acknowledges the Organization for Women in Science for the Developing World (OWSD) Ph.D. Fellowship。
文摘Biological methane oxidation is a crucial process in the global carbon cycle that reduces methane emissions from paddy fields and natural wetlands into the atmosphere.However,soil organic carbon accumulation associated with microbial methane oxidation is poorly understood.Therefore,to investigate methane-derived carbon incorporation into soil organic matter,paddy soils originated from different parent materials(Inceptisol,Entisol,and Alfisol) were collected after rice harvesting from four major rice-producing regions in Bangladesh.Following microcosm incubation with 5%(volume/volume)^(13) CH_(4),soil^(13) C-atom abundances significantly increased from background level of 1.08% to 1.88%–2.78%,leading to a net methane-derived accumulation of soil organic carbon ranging from 120 to 307 mg kg^(-1).Approximately 23.6%–60.0% of the methane consumed was converted to soil organic carbon during microbial methane oxidation.The phylogeny of^(13) C-labeled pmoA(enconding the alpha subunit of the particulate methane monooxygenase) and 16 S rRNA genes further revealed that canonical α(type II) and γ(type I) Proteobacteria were active methane oxidizers.Members within the Methylobacter-and Methylosarcina-affiliated type Ia lineages dominated active methane-oxidizing communities that were responsible for the majority of methane-derived carbon accumulation in all three paddy soils,while Methylocystis-affiliated type IIa lineage was the key contributor in one paddy soil of Inceptisol origin.These results suggest that methanotroph-mediated synthesis of biomass plays an important role in soil organic matter accumulation.This study thus supports the concept that methanotrophs not only consume the greenhouse gas methane but also serve as a key biotic factor in maintaining soil fertility.