Great efforts had been made to use indirect non-destructive tests in the geotechnical evaluation of rocks, especially sandstones, employing different empirical equations. However, most of these equations have been der...Great efforts had been made to use indirect non-destructive tests in the geotechnical evaluation of rocks, especially sandstones, employing different empirical equations. However, most of these equations have been derived from hard and compacted sandstones data</span><span style="font-family:"">;</span><span style="font-family:"">therefore, the focus of this research is on weak and weakly compacted sandstones, aiming firstly to obtain empirical equations for estimating their characteristics, secondly to demonstrate and visualize the correlations between the studied variables, and finally to cluster <span>the studied samples based on their characteristics. To attain these aims</span></span><span style="font-family:"">,</span><span style="font-family:""> twenty</span><span style="font-family:""> oriented block samples were collected from Nubia sandstone, central Eastern Desert, Golden Triangle area, Egypt. These samples were prepared and tested according to standard test methods, including uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), Schmidt rebound number (SRN), porosity (<i><i>n</i></i>), bulk density (<span>ρ</span>), and ultrasonic P-wave velocity (UPV). The loss on ignition (LOI) was also employed as a physicochemical test for classifying the studied samples and indicating pores filling materials. The results revealed that these sandstones are characterized mainly by high <i><i>n</i></i>, low <span>ρ</span>, and low UPV values and these give an indication of weakly compacted and weakly cemented sandstone with shallow burial diagenetic conditions. Based on UCS and elastic modulus values, these sandstones are mainly classified as very low strength and highly yielding rocks. The results of regression analysis show satisfactory correlations between physical and mechanical characteristics, indicating the suitability of obtained empirical equations to deduce these properties. Principal component analysis revealed that the LOI, BTS, SRN, and USC have a positive correlation to each other and weakly correlated with <i><i>ρ</i></i> and UPV, which positively correlated to each other and negatively correlated to <i><i>n</i></i>. The results of agglomerative hierarchical clustering revealed that the studied samples can group into three main clusters depending on their USC, LOI, and <i><i>n</i></i><span> </span>values.展开更多
Amorphous microwires(AMWs)are well known for their high strength and elastic limit,making them excellent candidates for various engineering applications.However,one of the key challenges in utilizing AMWs is their inh...Amorphous microwires(AMWs)are well known for their high strength and elastic limit,making them excellent candidates for various engineering applications.However,one of the key challenges in utilizing AMWs is their inherent variability in mechanical performance,particularly in achieving stable fracture strength across different compositions.This study provides critical insights into the relationship between microstructure and mechanical behavior by investigating CuZr-based AMWs with varying compositions during quasi-static tensile fracture.Specifically,uniaxial tensile tests on Cu_(48)Zr_(48)Al_(4),Cu_(45)Zr_(45)Co_(10),and Cu_(48)Zr_(47.2)Al_(4)Nb_(0.8) AMWs,combined with log-normal and Weibull statistical analysis,revealed that Cu_(48)Zr_(47.2)Al4Nb_(0.8) exhibits the highest fracture reliability(mTr=3.97)and fracture threshold(σμTr=1307 MPa),while Cu_(48)Zr_(48)Al_(4) showed the lowest performance(m_(Tr)=3.08,σ_(μTr)=1085 MPa).Moreover,a standard power-law relationship exists between the characteristic size L of the fracture surface and the degree of order O was established,linking atomic mixing enthalpy and atomic radius to structural homogeneity and fracture behavior.This study provides an important perspective for optimizing AMW compositions to achieve higher fracture strength and improve the reliability for engineering applications.展开更多
Hot compression tests in the temperature range of 340-450 ℃ and strain rate range of 0.001-1 s^-1 of spray-formed 7055 aluminum alloy were carried out to study its hot deformation behavior. Three phenomenological mod...Hot compression tests in the temperature range of 340-450 ℃ and strain rate range of 0.001-1 s^-1 of spray-formed 7055 aluminum alloy were carried out to study its hot deformation behavior. Three phenomenological models including Johnson-Cook, modified Fields-Backofen and Arrhenius-type were introduced to predict the flow stresses during the compression process. And then, a comparative predictability of the phenomenological models was estimated in terms of the relative errors, correlation coefficient（R）, and average absolute relative error（AARE）. The results indicate that Johnson-Cook model and modified Fields-Backofen model cannot well predict the hot deformation behavior due to the large deviation in the process of line regression fitting. Arrhenius-type model obtains the best fit through combining the effect of strain rate and temperature.展开更多
We reviewed a study addressing the development and validation of a prediction model for moderately severe and severe acute pancreatitis in pregnancy. We identified some statistical deficiencies in this article. In add...We reviewed a study addressing the development and validation of a prediction model for moderately severe and severe acute pancreatitis in pregnancy. We identified some statistical deficiencies in this article. In addition, we believe that the role of cholesterol as a predictor should be described in more detail.展开更多
Based on multiple datasets, correlation and composite analyses, and case studies, this paper investigated possible influences of the Indian Ocean dipole(IOD) mode on the eastward propagation of intraseasonal oscillati...Based on multiple datasets, correlation and composite analyses, and case studies, this paper investigated possible influences of the Indian Ocean dipole(IOD) mode on the eastward propagation of intraseasonal oscillation in the tropical atmosphere. The results showed that(1) the 30-60 day outgoing longwave radiation anomalies in the southeastern Indian Ocean and the 30-60 day 850-hPa zonal wind anomalies over the equatorial central Indian Ocean were significantly correlated with the IOD index;(2) during positive IOD years, the anomalously cold water in the southeastern Indian Ocean and the 850-hPa anomalous easterlies over the equatorial central Indian Ocean might act as barriers to the continuously eastward propagation of the intraseasonal convection, which interrupts the Madden-Julian oscillation(MJO) propagation in the eastern equatorial Indian Ocean and western Pacific; and(3) during negative IOD years, the anomalously warm water in the southeastern Indian Ocean and the low-level westerly anomalies over the equatorial central Indian Ocean favor the eastward movement of MJO.展开更多
Introduction:Secondhand smoke(SHS)exposure remains a significant public health threat to human health.Understanding the spatial distribution characteristics of SHS exposure is essential for developing targeted,region-...Introduction:Secondhand smoke(SHS)exposure remains a significant public health threat to human health.Understanding the spatial distribution characteristics of SHS exposure is essential for developing targeted,region-specific tobacco control strategies and interventions.This study analyzed the spatial clustering of SHS exposure and its influencing factors in China in 2022.Methods:This study utilized data from the 2022 China National Adult Tobacco Survey(NATS).Descriptive statistical analyses were performed using Stata(version 17.0;StataCorp LLC,College Station,Texas,USA).Spatial analyses were conducted using GeoDa(version 1.22;Dr.Luc Anselin’s team,Arizona State,USA)to examine global spatial autocorrelation,local spatial autocorrelation and ordinary least squares(OLS)spatial regression.Provincial-level figures of SHS exposure rates were visualized using GraphPad Prism(version 9.5;GraphPad Software,Boston,USA).Results:In 2022,the SHS exposure rate among nonsmoking adults aged 15 years and above in China was 52.4%.The distribution of SHS exposure in China exhibited significant provincial clustering(Moran’s I=0.337,Z=4.626,P=0.001).LISA analysis identified High-High clusters of SHS exposure in Yunnan,Guizhou,Sichuan,Chongqing,Guangdong,and Hainan,while Henan emerged as a Low-Low cluster.Key factors influencing regional SHS exposure included smoking rates,tobacco control measures in homes,indoor workplaces,and healthcare institutions,population coverage of comprehensive smoke-free regulations,and cognition of SHS harm and smoking harm.Conclusions:Although SHS exposure rates in China have decreased,they remain a significant concern.Targeted interventions should be implemented in southwestern and central southern China,with strengthened smoke-free management in key settings including homes,indoor workplaces,and medical institutions.Additionally,expanding the coverage of comprehensive smoke-free laws and regulations is recommended.展开更多
Introduction:Substantial evidence indicates that electronic cigarettes(e-cigarettes)pose considerable health risks to the human body.There is a lack of surveillance data regarding adult e-cigarette use behavior in Bei...Introduction:Substantial evidence indicates that electronic cigarettes(e-cigarettes)pose considerable health risks to the human body.There is a lack of surveillance data regarding adult e-cigarette use behavior in Beijing.Methods:This study utilizes the 2016–2023 Beijing Adult Tobacco Survey data to assess the current status,changing trends,and influencing factors of e-cigarette use among urban and rural residents aged≥15 years across 16 districts of Beijing Municipality.All statistical analyses incorporated complex sampling weights.Results:The prevalence of e-cigarette ever use among Beijing residents aged≥15 years was 5.7%,8.1%,8.6%,and 6.9%in 2016,2019,2021,and 2023,respectively,while current use prevalence was 1.6%,2.1%,2.7%,and 1.8%,respectively.Males,younger individuals,those with higher educational attainment,and those living alone demonstrated greater odds of e-cigarette use.Current smokers who had attempted to quit within the past 12 months showed the highest odds of use,followed by current smokers without quit attempts and former smokers who had quit for less than 12 months.Conclusions:The public are not fully aware of the academic and clinical controversies regarding ecigarettes’effectiveness for smoking cessation and may underestimate their health risks.There is an urgent need for targeted knowledge campaigns addressing these misconceptions and for the provision of more accessible smoking cessation services.展开更多
Currently,the design of transformers insulation predominantly depends on the allowable alternating current(AC)field values for insulating oil established by Weidmann in the 1980s,lacking the research under direct curr...Currently,the design of transformers insulation predominantly depends on the allowable alternating current(AC)field values for insulating oil established by Weidmann in the 1980s,lacking the research under direct current(DC)voltage for converter transformers.This study selects naphthenic oils and paraffin-based oil transformer oil as research subjects,establishing a practical measurement platform to ascertain the oil breakdown characteristics under DC voltage.Furthermore,it statistically analyses the allowable DC field values of the oil.The findings elucidate that(1)the three-parameter Weibull dis-tribution is more suitable to conduct a statistical analysis for oil breakdown probability,yielding a fitting degree up to 99.95%.(2)For a constant electrode spacing,a 14.81%voltage increment escalates the breakdown probability of the oil gap from 3.33%to 73.33%.Concurrently,an increase in electrode spacing leads to a substantial decrement in the breakdown field strength of transformer oil,with KI25X experiencing a 54.51%reduction as electrode spacing extends from 5 to 25 mm.(3)The constant terms of the allowable DC field strength for S4,KI50X,and KI25X are found to be 19.728,17.221,and 19.281,respectively.(4)A thorough analysis for differences in physicochemical properties and electrical parameters elucidates the variations in insulation properties across different transformer oils.The findings presented in this study offer essential theoretical and technical foundations for the design,evaluation,and enhancement of insulation structures in converter transformers.展开更多
One of the largest Ordovician sea-level rises is the Evae transgression,which occurs in the lower part of the Oepikodus evae Biozone,indicative of a late Floian age.Specifically,the characteristics associated with the...One of the largest Ordovician sea-level rises is the Evae transgression,which occurs in the lower part of the Oepikodus evae Biozone,indicative of a late Floian age.Specifically,the characteristics associated with the highstand of this event included:a higher proportion of specimens of the index species O.evae than other species,a diversity acme in the evae Biozone,and a reduction of biogeographic barriers that resulted in a high proportion of species with cosmopolitan distribution.In the present contribution,the pattern of species similarity among Laurentia,Argentine Precordillera,Baltica,Kazakhstania,South China,and Australia is evaluated with a multiple coefficient analysis including only the sections that recorded the highstand of the Evae transgression.Moreover,the effect of possible terrestrial,latitudinal,physicochemical barriers and palaeogeographic distance on the species distribution is statistically analysed.Our results show a global pattern of conodont species distribution that is highly constrained by the tested palaeoenvironmental factors.This suggests that contrary to what was expected for a prominent transgression,faunal barriers did not decrease significantly during the Evae drowning peak.展开更多
During latest Devonian and early Carboniferous times,calcareous foraminifers were abundant,widely distributed,and showed the most rapid rate of evolution in the shallow?sea deposits.These factors,especially their fast...During latest Devonian and early Carboniferous times,calcareous foraminifers were abundant,widely distributed,and showed the most rapid rate of evolution in the shallow?sea deposits.These factors,especially their fast phylogenetic changes,make them an essen?tial element in biostratigraphic schemes of this time interval.However,the distribution patterns of calcareous foraminifers depend on a series of biological and non?biological factors,such as population sizes,dispersion,oceanic currents and temperatures,and substrate types,which are not always well?controlled when interpreting spatial and temporal distribution patterns.For this study,a dataset of calcareous foraminifers was compiled containing the tempo?ral distribution(biozone level)of 420 species belonging to 155 genera currently described from Strunian(latest Devonian)to basal Serpukhovian(Lower Carboniferous)key sections in southern China,and the presence of those species in eleven palaeobiogeographical units.The comparison of the regional Chinese diversity curve,which has a bell?shaped form with a dou?ble peak in the Ivorian,to a global curve shows the influence of local and regional factors.Mini?mum values in the Chinese Strunian,basal Tournaisian and early late Visean can be explained by the small number of studied outcrops,unfavourable facies and depositional gaps in these stratigraphic intervals in South China.This is especially obvious in the late Visean and Serpuk?hovian,which is a peak time of global diversity.The fall observed at that time interval in southern China is easily explained by the fact that this time peried is far less intensively studied and thus fewer data are present in the database.The opposite situation is seen around the TournaisianVisean boundary.Here,a peak is found in both regional and global curves,but that up to 87%of all known species are found in southern China seems to be unlikely,especially when the normal average value are 35%-40%.This anomalously high percentage is a consequence of the work undertaken on the Global Stratotype Section and Point(GSSP),and it shows that a species deficit may exist in the global curve.*Cluster,hierarchical cluster and Nonmetric multidimensienal Scalingel(NMDS)analyses have been calculated to study the palaeobiogeographical affinities of the southern Chinese calcareous foraminifers.The palaeobiogeographical patterns for the complete studied interval or parts of it(substages)are comparable on the genus and species level and stable throughtime.The assemblages found in southern China are well connected to other palaeo(bio)geo?graphical entities supporting the idea of relatively abundant widespread and cosmopolitan taxa in the studied interval.A cluster of South China,Europe and the Russian Platform is found in all analyses.This cluster often attached to the units Far-East Russia and Turkey rep?resents the northern Palaeotethyan Realm.The relatively close affinities between South China and North America cannot be well discussed yet.Chinese data for endemicity,geographical spread and biodiversity in the Tournaisian-Visean boundary interval can be roughly correlated to 3rd-order sea-level fluctuations.Migration patterns into and out of South China can only be suspected,but not yet quantified.展开更多
文摘Great efforts had been made to use indirect non-destructive tests in the geotechnical evaluation of rocks, especially sandstones, employing different empirical equations. However, most of these equations have been derived from hard and compacted sandstones data</span><span style="font-family:"">;</span><span style="font-family:"">therefore, the focus of this research is on weak and weakly compacted sandstones, aiming firstly to obtain empirical equations for estimating their characteristics, secondly to demonstrate and visualize the correlations between the studied variables, and finally to cluster <span>the studied samples based on their characteristics. To attain these aims</span></span><span style="font-family:"">,</span><span style="font-family:""> twenty</span><span style="font-family:""> oriented block samples were collected from Nubia sandstone, central Eastern Desert, Golden Triangle area, Egypt. These samples were prepared and tested according to standard test methods, including uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), Schmidt rebound number (SRN), porosity (<i><i>n</i></i>), bulk density (<span>ρ</span>), and ultrasonic P-wave velocity (UPV). The loss on ignition (LOI) was also employed as a physicochemical test for classifying the studied samples and indicating pores filling materials. The results revealed that these sandstones are characterized mainly by high <i><i>n</i></i>, low <span>ρ</span>, and low UPV values and these give an indication of weakly compacted and weakly cemented sandstone with shallow burial diagenetic conditions. Based on UCS and elastic modulus values, these sandstones are mainly classified as very low strength and highly yielding rocks. The results of regression analysis show satisfactory correlations between physical and mechanical characteristics, indicating the suitability of obtained empirical equations to deduce these properties. Principal component analysis revealed that the LOI, BTS, SRN, and USC have a positive correlation to each other and weakly correlated with <i><i>ρ</i></i> and UPV, which positively correlated to each other and negatively correlated to <i><i>n</i></i>. The results of agglomerative hierarchical clustering revealed that the studied samples can group into three main clusters depending on their USC, LOI, and <i><i>n</i></i><span> </span>values.
基金supported by the National Natural Science Foundation of China(Nos.52071118,52371025,and 52171154)。
文摘Amorphous microwires(AMWs)are well known for their high strength and elastic limit,making them excellent candidates for various engineering applications.However,one of the key challenges in utilizing AMWs is their inherent variability in mechanical performance,particularly in achieving stable fracture strength across different compositions.This study provides critical insights into the relationship between microstructure and mechanical behavior by investigating CuZr-based AMWs with varying compositions during quasi-static tensile fracture.Specifically,uniaxial tensile tests on Cu_(48)Zr_(48)Al_(4),Cu_(45)Zr_(45)Co_(10),and Cu_(48)Zr_(47.2)Al_(4)Nb_(0.8) AMWs,combined with log-normal and Weibull statistical analysis,revealed that Cu_(48)Zr_(47.2)Al4Nb_(0.8) exhibits the highest fracture reliability(mTr=3.97)and fracture threshold(σμTr=1307 MPa),while Cu_(48)Zr_(48)Al_(4) showed the lowest performance(m_(Tr)=3.08,σ_(μTr)=1085 MPa).Moreover,a standard power-law relationship exists between the characteristic size L of the fracture surface and the degree of order O was established,linking atomic mixing enthalpy and atomic radius to structural homogeneity and fracture behavior.This study provides an important perspective for optimizing AMW compositions to achieve higher fracture strength and improve the reliability for engineering applications.
基金Project(2013HH100055) supported by the Basic Research and Science and Technology Innovation Fund of Foshan City,China
文摘Hot compression tests in the temperature range of 340-450 ℃ and strain rate range of 0.001-1 s^-1 of spray-formed 7055 aluminum alloy were carried out to study its hot deformation behavior. Three phenomenological models including Johnson-Cook, modified Fields-Backofen and Arrhenius-type were introduced to predict the flow stresses during the compression process. And then, a comparative predictability of the phenomenological models was estimated in terms of the relative errors, correlation coefficient（R）, and average absolute relative error（AARE）. The results indicate that Johnson-Cook model and modified Fields-Backofen model cannot well predict the hot deformation behavior due to the large deviation in the process of line regression fitting. Arrhenius-type model obtains the best fit through combining the effect of strain rate and temperature.
文摘We reviewed a study addressing the development and validation of a prediction model for moderately severe and severe acute pancreatitis in pregnancy. We identified some statistical deficiencies in this article. In addition, we believe that the role of cholesterol as a predictor should be described in more detail.
基金National Science foundation of China(41005038)Chinese Public Sector(Meteorology)Research and Special Project(GYHY200906016)National Key Technology Research and Development Program of the Ministry of Science and Technology of China(2009BAC51B01,2009BAC51B02)
文摘Based on multiple datasets, correlation and composite analyses, and case studies, this paper investigated possible influences of the Indian Ocean dipole(IOD) mode on the eastward propagation of intraseasonal oscillation in the tropical atmosphere. The results showed that(1) the 30-60 day outgoing longwave radiation anomalies in the southeastern Indian Ocean and the 30-60 day 850-hPa zonal wind anomalies over the equatorial central Indian Ocean were significantly correlated with the IOD index;(2) during positive IOD years, the anomalously cold water in the southeastern Indian Ocean and the 850-hPa anomalous easterlies over the equatorial central Indian Ocean might act as barriers to the continuously eastward propagation of the intraseasonal convection, which interrupts the Madden-Julian oscillation(MJO) propagation in the eastern equatorial Indian Ocean and western Pacific; and(3) during negative IOD years, the anomalously warm water in the southeastern Indian Ocean and the low-level westerly anomalies over the equatorial central Indian Ocean favor the eastward movement of MJO.
基金Special Project of the Survey of Basic Resources for Science and Technology(2023FY100605).
文摘Introduction:Secondhand smoke(SHS)exposure remains a significant public health threat to human health.Understanding the spatial distribution characteristics of SHS exposure is essential for developing targeted,region-specific tobacco control strategies and interventions.This study analyzed the spatial clustering of SHS exposure and its influencing factors in China in 2022.Methods:This study utilized data from the 2022 China National Adult Tobacco Survey(NATS).Descriptive statistical analyses were performed using Stata(version 17.0;StataCorp LLC,College Station,Texas,USA).Spatial analyses were conducted using GeoDa(version 1.22;Dr.Luc Anselin’s team,Arizona State,USA)to examine global spatial autocorrelation,local spatial autocorrelation and ordinary least squares(OLS)spatial regression.Provincial-level figures of SHS exposure rates were visualized using GraphPad Prism(version 9.5;GraphPad Software,Boston,USA).Results:In 2022,the SHS exposure rate among nonsmoking adults aged 15 years and above in China was 52.4%.The distribution of SHS exposure in China exhibited significant provincial clustering(Moran’s I=0.337,Z=4.626,P=0.001).LISA analysis identified High-High clusters of SHS exposure in Yunnan,Guizhou,Sichuan,Chongqing,Guangdong,and Hainan,while Henan emerged as a Low-Low cluster.Key factors influencing regional SHS exposure included smoking rates,tobacco control measures in homes,indoor workplaces,and healthcare institutions,population coverage of comprehensive smoke-free regulations,and cognition of SHS harm and smoking harm.Conclusions:Although SHS exposure rates in China have decreased,they remain a significant concern.Targeted interventions should be implemented in southwestern and central southern China,with strengthened smoke-free management in key settings including homes,indoor workplaces,and medical institutions.Additionally,expanding the coverage of comprehensive smoke-free laws and regulations is recommended.
文摘Introduction:Substantial evidence indicates that electronic cigarettes(e-cigarettes)pose considerable health risks to the human body.There is a lack of surveillance data regarding adult e-cigarette use behavior in Beijing.Methods:This study utilizes the 2016–2023 Beijing Adult Tobacco Survey data to assess the current status,changing trends,and influencing factors of e-cigarette use among urban and rural residents aged≥15 years across 16 districts of Beijing Municipality.All statistical analyses incorporated complex sampling weights.Results:The prevalence of e-cigarette ever use among Beijing residents aged≥15 years was 5.7%,8.1%,8.6%,and 6.9%in 2016,2019,2021,and 2023,respectively,while current use prevalence was 1.6%,2.1%,2.7%,and 1.8%,respectively.Males,younger individuals,those with higher educational attainment,and those living alone demonstrated greater odds of e-cigarette use.Current smokers who had attempted to quit within the past 12 months showed the highest odds of use,followed by current smokers without quit attempts and former smokers who had quit for less than 12 months.Conclusions:The public are not fully aware of the academic and clinical controversies regarding ecigarettes’effectiveness for smoking cessation and may underestimate their health risks.There is an urgent need for targeted knowledge campaigns addressing these misconceptions and for the provision of more accessible smoking cessation services.
基金National Natural Science Foundation of China,Grant/Award Number:52107148China Postdoctoral Science Foundation,Grant/Award Number:2020M680485Fundamental Research Funds for the Central-Universities,Grant/Award Number:2021MS004。
文摘Currently,the design of transformers insulation predominantly depends on the allowable alternating current(AC)field values for insulating oil established by Weidmann in the 1980s,lacking the research under direct current(DC)voltage for converter transformers.This study selects naphthenic oils and paraffin-based oil transformer oil as research subjects,establishing a practical measurement platform to ascertain the oil breakdown characteristics under DC voltage.Furthermore,it statistically analyses the allowable DC field values of the oil.The findings elucidate that(1)the three-parameter Weibull dis-tribution is more suitable to conduct a statistical analysis for oil breakdown probability,yielding a fitting degree up to 99.95%.(2)For a constant electrode spacing,a 14.81%voltage increment escalates the breakdown probability of the oil gap from 3.33%to 73.33%.Concurrently,an increase in electrode spacing leads to a substantial decrement in the breakdown field strength of transformer oil,with KI25X experiencing a 54.51%reduction as electrode spacing extends from 5 to 25 mm.(3)The constant terms of the allowable DC field strength for S4,KI50X,and KI25X are found to be 19.728,17.221,and 19.281,respectively.(4)A thorough analysis for differences in physicochemical properties and electrical parameters elucidates the variations in insulation properties across different transformer oils.The findings presented in this study offer essential theoretical and technical foundations for the design,evaluation,and enhancement of insulation structures in converter transformers.
基金supported by the Centro de Investigaciones Geol ogicas Aplicadas (CIGEA) (FCEFy NUNC)the Secretaría de Ciencia y Tecnología (Se Cy T-UNC),Universidad Nacional de C ordoba,Argentina。
文摘One of the largest Ordovician sea-level rises is the Evae transgression,which occurs in the lower part of the Oepikodus evae Biozone,indicative of a late Floian age.Specifically,the characteristics associated with the highstand of this event included:a higher proportion of specimens of the index species O.evae than other species,a diversity acme in the evae Biozone,and a reduction of biogeographic barriers that resulted in a high proportion of species with cosmopolitan distribution.In the present contribution,the pattern of species similarity among Laurentia,Argentine Precordillera,Baltica,Kazakhstania,South China,and Australia is evaluated with a multiple coefficient analysis including only the sections that recorded the highstand of the Evae transgression.Moreover,the effect of possible terrestrial,latitudinal,physicochemical barriers and palaeogeographic distance on the species distribution is statistically analysed.Our results show a global pattern of conodont species distribution that is highly constrained by the tested palaeoenvironmental factors.This suggests that contrary to what was expected for a prominent transgression,faunal barriers did not decrease significantly during the Evae drowning peak.
文摘During latest Devonian and early Carboniferous times,calcareous foraminifers were abundant,widely distributed,and showed the most rapid rate of evolution in the shallow?sea deposits.These factors,especially their fast phylogenetic changes,make them an essen?tial element in biostratigraphic schemes of this time interval.However,the distribution patterns of calcareous foraminifers depend on a series of biological and non?biological factors,such as population sizes,dispersion,oceanic currents and temperatures,and substrate types,which are not always well?controlled when interpreting spatial and temporal distribution patterns.For this study,a dataset of calcareous foraminifers was compiled containing the tempo?ral distribution(biozone level)of 420 species belonging to 155 genera currently described from Strunian(latest Devonian)to basal Serpukhovian(Lower Carboniferous)key sections in southern China,and the presence of those species in eleven palaeobiogeographical units.The comparison of the regional Chinese diversity curve,which has a bell?shaped form with a dou?ble peak in the Ivorian,to a global curve shows the influence of local and regional factors.Mini?mum values in the Chinese Strunian,basal Tournaisian and early late Visean can be explained by the small number of studied outcrops,unfavourable facies and depositional gaps in these stratigraphic intervals in South China.This is especially obvious in the late Visean and Serpuk?hovian,which is a peak time of global diversity.The fall observed at that time interval in southern China is easily explained by the fact that this time peried is far less intensively studied and thus fewer data are present in the database.The opposite situation is seen around the TournaisianVisean boundary.Here,a peak is found in both regional and global curves,but that up to 87%of all known species are found in southern China seems to be unlikely,especially when the normal average value are 35%-40%.This anomalously high percentage is a consequence of the work undertaken on the Global Stratotype Section and Point(GSSP),and it shows that a species deficit may exist in the global curve.*Cluster,hierarchical cluster and Nonmetric multidimensienal Scalingel(NMDS)analyses have been calculated to study the palaeobiogeographical affinities of the southern Chinese calcareous foraminifers.The palaeobiogeographical patterns for the complete studied interval or parts of it(substages)are comparable on the genus and species level and stable throughtime.The assemblages found in southern China are well connected to other palaeo(bio)geo?graphical entities supporting the idea of relatively abundant widespread and cosmopolitan taxa in the studied interval.A cluster of South China,Europe and the Russian Platform is found in all analyses.This cluster often attached to the units Far-East Russia and Turkey rep?resents the northern Palaeotethyan Realm.The relatively close affinities between South China and North America cannot be well discussed yet.Chinese data for endemicity,geographical spread and biodiversity in the Tournaisian-Visean boundary interval can be roughly correlated to 3rd-order sea-level fluctuations.Migration patterns into and out of South China can only be suspected,but not yet quantified.
