Air mass is inter-hemispherically redistributed, leading to an interesting phenomenon known as the Inter-Hemispheric Oscillation （IHO）. In the present article, the seasonality of the interannual IHO has been examine...Air mass is inter-hemispherically redistributed, leading to an interesting phenomenon known as the Inter-Hemispheric Oscillation （IHO）. In the present article, the seasonality of the interannual IHO has been examined by employing monthly mean reanalyses from NCEP/NCAR, EAR40, and JRA25 for the period of 1958–2006. It is found that the IHO indices as calculated from different reanalyses are generally consistent with each other. A distinct seesaw structure in all four seasons between the northern and southern hemispheres is observed as the IHO signature in both the surface air pressure anomalies （SAPAs） and the leading EOF component of the anomalous zonal mean quantities. When the SAPAs are positive （negative） in the northern hemisphere, they are negative （positive） in the southern hemisphere. Large values of SAPAs are usually observed in mid- and high-latitude areas in all but the solstice seasons. In boreal summer and winter, relatively stronger perturbations of IHO-related SAPA are found in the Asian monsoon region, which shows a large difference from the status in boreal spring and fall. This suggests that seasonal mean monsoon activity is globally linked via air mass redistribution globally on interannual timescales, showing a very interesting linkage between monsoons and the IHO in the global domain. In all seasons, large values of SAPA always exist over the Antarctic and the surrounding regions, implying a close relation with Antarctic oscillations.展开更多
During deep drawing process,the material parameters of blank have a significant effect on the quality of the drawn part and the determination of process parameters. Here,a 3D finite element model is developed for the ...During deep drawing process,the material parameters of blank have a significant effect on the quality of the drawn part and the determination of process parameters. Here,a 3D finite element model is developed for the deep drawing process of a thin-walled hemispheric surface part. Then the influences of material parameters including hardening exponent n,yield stress σs and elastic modulus E on the process are investigated by simulation. The results show that the effects of n and σs on punch force,thickness variation and equivalent strain are more notable. The maximum equivalent plastic strain occurs outside the die corner. However,when the value of n is 0.03 or σs is smaller than 120 MPa,higher equivalent plastic strain occurs at ball top.展开更多
The sediment particles play a huge role in shaping the bed load transport.In this research,240 water-tunnel experiments are carried out to investigate the incipient velocity of the observation particles in two particl...The sediment particles play a huge role in shaping the bed load transport.In this research,240 water-tunnel experiments are carried out to investigate the incipient velocity of the observation particles in two particle arrangements.To accurately predict the incipient velocity of the observation particles,the equation is conceived by the rolling instability mechanism.The incipient velocity equations and experimental data are used to analyze the trend of dispersive pressure and the effect of arrangement position on velocity.We find that it is appropriate to choose the coefficient of drag as 0.261 and the coefficient of lift as 0.198 for the incipient velocity equation of spherical particles on the hemispherical bed surface.Furthermore,the dispersive pressure is closely related to the flow state,particle size,and particle arrangement,which leads to the incipient velocity of the observation particle being at a minimum when the interference particle angle is 45°.Finally,the particle spacing and the projected area changed with the arrangements,directly affecting the incipient velocity of the observed particle.The analysis of four aspects for the coefficients,dispersive pressure,different particle spacing,and projected area will facilitate the prediction of particle incipient velocity,especially on hemispherical beds.展开更多
The Tibetan Plateau(TP)exerts a profound influence on global climate over million-year timescales due to its past uplift.However,whether the ongoing climate changes over the TP,particularly the persistent reduction in...The Tibetan Plateau(TP)exerts a profound influence on global climate over million-year timescales due to its past uplift.However,whether the ongoing climate changes over the TP,particularly the persistent reduction in its local albedo(referred to as“TP surface darkening”),can exert global impacts remains elusive.In this study,a state-of-the-art coupled land–atmosphere global climate model has been employed to scrutinize the impact of TP darkening on polar climate changes.Results indicate that the projected TP darkening has the potential to generate a stationary Rossby wave train,thereby modulating the atmospheric circulation in the high-latitudes of the Northern Hemisphere and instigating a dipole-like surface air temperature anomaly pattern around the Arctic region.An additional experiment suggests that the projected Arctic warming may in return warm the TP,thus forming a bi-directional linkage between these two climate systems.Given their association with vast ice reservoirs,the elucidation of this mechanism in our study is crucial in advancing our comprehension of Earth system climate projections.展开更多
The surface topography of noble metal particles is a significant factor in tailoring surface-enhanced Raman scattering （SERS） properties. Here, we present a simple fabrication route to hexagonally arranged arrays of...The surface topography of noble metal particles is a significant factor in tailoring surface-enhanced Raman scattering （SERS） properties. Here, we present a simple fabrication route to hexagonally arranged arrays of surface-roughened urchin- like Ag hemispheres （Ag-HSs） decorated with Ag nanoparticles （Ag-NPs） for highly active and reproducible SERS substrates. The urchin-like Ag-HS arrays are achieved by sputtering Ag onto the top surface of a highly ordered porous anodic aluminum oxide （AAO） template to form ordered arrays of smooth Ag-HSs and then by electrodepositing Ag-NPs onto the surface of each Ag-HS. Owing to the ordered arrangement of the Ag-HSs and the improved surface roughness, the urchin-like hierarchical Ag-HS arrays can provide sufficient and uniform ＂hot spots＂ for reproducible and highly active SERS effects. Using the urchin-like Ag-HS arrays as SERS substrates, 10-7 M dibutyl phthalate （a member of plasticizers family） and 1.5 × 10-5 M PCB-77 （one congener of polychlorinated biphenyl, a notorious class of pollutants） are identified, showing promising potential for these substrates in the rapid recognition of organic pollutants.展开更多
Plague has caused the death of hundreds of millions of people throughout the human history.Today this disease is again re-emerging and hence is again becoming an increasing threat to human health in several parts of t...Plague has caused the death of hundreds of millions of people throughout the human history.Today this disease is again re-emerging and hence is again becoming an increasing threat to human health in several parts of the world.However,impacts of global climate variation(e.g.El Nino and Southern Oscillation[ENSO])and global warming on plagues are largely unknown.Using cross-spectral analysis and cross-wavelet analysis,we have analyzed the relationship between increase rate of human plague in China during 1871–2003 and the following climate factors(as measured by the Southern Oscillation Index[SOI],Sea Surface Temperature of east Pacific equator[SST]and air Temperature of the Northern Hemisphere[NHT]).We found in the frequency domain that increase rate of human plague was closely associated with SOI and SST.Cross-spectral analysis reveals that significant coherencies between increase rate of human plague and ENSO were found over short periods(2–3 years),medium periods(6–7 years)and long periods(11–12 years,30–40 years).Cross-wavelet analysis reveals that increase rate of human plague oscillates in phase with SOI,but in anti-phase with SST over periods of 2–4 years and approximately 8 years(6–10 years).These results indicate that ENSO-driven climate variation may be important for occurrences of human plague in China.However,there is a need for a further analysis of the underlying mechanism between human plague in China and ENSO.展开更多
Although surface-enhanced Raman spectroscopy(SERS)substrates have achieved high sensitivity,it is still difficult to apply these SERS protocols to the on-site detection of real samples due to the SERS substrate being ...Although surface-enhanced Raman spectroscopy(SERS)substrates have achieved high sensitivity,it is still difficult to apply these SERS protocols to the on-site detection of real samples due to the SERS substrate being fabrication-complexed,unstable,reproducible,or unable to be applied in batch production.Here,a large-scale ordered two-dimensional array of Au nano-hemispheres was developed through electron beam vaporization of Au onto the easy-available commercialized anodic aluminum oxide(AAO)template with two-layer nanostructures of different diameters.The uniform Au nano-hemisphere is reliable for SERS detection of malachite green(MG)due to the relative standard deviation(RSD)of the SERS intensities at different locations less than 10%.With the optimized excitation wavelength,solvent effect and pH environment,the linear range of MG detection spans from 10^(-10) to 10^(-6) mol/L with a limit of detection(LOD)of 4×10^(-10) mol/L.The enhancement factor can reach 1.2×10^(6).After extraction with acetonitrile and dichloromethane,MG in the spiked tilapia was detected with satisfactory recovery.The results indicate that the Au nano-hemisphere array can be expected to greatly facilitate SERS practical applications in detecting harmful food additives and chemicals due to the advantages of chemical inertness,physical robustness,simple fabrication,controllability,large-area uniformity,and large-batch production.展开更多
Endocasts are important materials used for the study of human brain evolution,and allow examination of the external features of brain anatomy from the inside the cranium.Studies examining brain asymmetries in fossil h...Endocasts are important materials used for the study of human brain evolution,and allow examination of the external features of brain anatomy from the inside the cranium.Studies examining brain asymmetries in fossil hominids are usually limited to scoring of differences in hemisphere protrusion rostrally and caudally,or to comparing the width of the hemispheres.In the present study,using 3D laser scanning,we examined asymmetries of the hemisphere volumes and surface areas in the Zhoukoudain (ZKD) Homo erectus,dated to 0.4-0.8 Ma.Compared with modern endocasts,we found that the absolute hemisphere volumes and surface areas exhibited no significant asymmetries in the ZKD or in modern specimens.However,the relative hemisphere volumes against surface areas differed between the two groups.When comparing the relative sizes between the left and right hemispheres,the ZKD specimens exhibited a greater variation than in the modern humans;there were no differences in the two hemispheres in the ZKD specimens,while in the modern endocasts the left hemisphere was significantly greater than the right hemisphere.These data suggest that brain asymmetries originated from relative brain sizes rather than absolute brain volumes during human evolution.These anatomical changes are likely related to the origin of human brain lateralization.展开更多
The assumption of M. Milankovich about the constancy of the Earth's albedo during the interglacial period was replaced with the alternative one. The model was developed where anomalies of the average annual temper...The assumption of M. Milankovich about the constancy of the Earth's albedo during the interglacial period was replaced with the alternative one. The model was developed where anomalies of the average annual temperature of the surface atmosphere were related with interannual changes in the planetary albedo and the thermal inertia of the hydrosphere. The surface temperature changes due to albedo actual and model changes were calculated. Possible external causes of albedo changes were considered.展开更多
基金supported jointlyby the National Key Technology R&D Program (GrantNo. 2007BAC29B02)the National Natural Science Foundation of China (NSFC, Grant No. 40675025)the Key Laboratory of Meteorological Disasters, Nanjing University of Information Science & Technology (NUIST,KLME060101)
文摘Air mass is inter-hemispherically redistributed, leading to an interesting phenomenon known as the Inter-Hemispheric Oscillation （IHO）. In the present article, the seasonality of the interannual IHO has been examined by employing monthly mean reanalyses from NCEP/NCAR, EAR40, and JRA25 for the period of 1958–2006. It is found that the IHO indices as calculated from different reanalyses are generally consistent with each other. A distinct seesaw structure in all four seasons between the northern and southern hemispheres is observed as the IHO signature in both the surface air pressure anomalies （SAPAs） and the leading EOF component of the anomalous zonal mean quantities. When the SAPAs are positive （negative） in the northern hemisphere, they are negative （positive） in the southern hemisphere. Large values of SAPAs are usually observed in mid- and high-latitude areas in all but the solstice seasons. In boreal summer and winter, relatively stronger perturbations of IHO-related SAPA are found in the Asian monsoon region, which shows a large difference from the status in boreal spring and fall. This suggests that seasonal mean monsoon activity is globally linked via air mass redistribution globally on interannual timescales, showing a very interesting linkage between monsoons and the IHO in the global domain. In all seasons, large values of SAPA always exist over the Antarctic and the surrounding regions, implying a close relation with Antarctic oscillations.
基金Project(2007CB613802) supported by the National Basic Research Program of ChinaProject(50805121) supported by the National Natural Science Foundation of China
文摘During deep drawing process,the material parameters of blank have a significant effect on the quality of the drawn part and the determination of process parameters. Here,a 3D finite element model is developed for the deep drawing process of a thin-walled hemispheric surface part. Then the influences of material parameters including hardening exponent n,yield stress σs and elastic modulus E on the process are investigated by simulation. The results show that the effects of n and σs on punch force,thickness variation and equivalent strain are more notable. The maximum equivalent plastic strain occurs outside the die corner. However,when the value of n is 0.03 or σs is smaller than 120 MPa,higher equivalent plastic strain occurs at ball top.
基金financially supported by the National Key Research and Development Program of China(Grant No.2021YFB2601100)the National Natural Science Foundation of China(Grant No.51839002,51979014 and 52271257)+1 种基金the Natural Science Foundation of Hunan Province(Grant No.2022JJ10047)the Hunan Provincial Innovation Foundation for Postgraduate(Grant No.CX20220909).
文摘The sediment particles play a huge role in shaping the bed load transport.In this research,240 water-tunnel experiments are carried out to investigate the incipient velocity of the observation particles in two particle arrangements.To accurately predict the incipient velocity of the observation particles,the equation is conceived by the rolling instability mechanism.The incipient velocity equations and experimental data are used to analyze the trend of dispersive pressure and the effect of arrangement position on velocity.We find that it is appropriate to choose the coefficient of drag as 0.261 and the coefficient of lift as 0.198 for the incipient velocity equation of spherical particles on the hemispherical bed surface.Furthermore,the dispersive pressure is closely related to the flow state,particle size,and particle arrangement,which leads to the incipient velocity of the observation particle being at a minimum when the interference particle angle is 45°.Finally,the particle spacing and the projected area changed with the arrangements,directly affecting the incipient velocity of the observed particle.The analysis of four aspects for the coefficients,dispersive pressure,different particle spacing,and projected area will facilitate the prediction of particle incipient velocity,especially on hemispherical beds.
基金This work was supported by the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0208)the National Natural Science Foundation of China(41988101)the Xplorer Prize.
文摘The Tibetan Plateau(TP)exerts a profound influence on global climate over million-year timescales due to its past uplift.However,whether the ongoing climate changes over the TP,particularly the persistent reduction in its local albedo(referred to as“TP surface darkening”),can exert global impacts remains elusive.In this study,a state-of-the-art coupled land–atmosphere global climate model has been employed to scrutinize the impact of TP darkening on polar climate changes.Results indicate that the projected TP darkening has the potential to generate a stationary Rossby wave train,thereby modulating the atmospheric circulation in the high-latitudes of the Northern Hemisphere and instigating a dipole-like surface air temperature anomaly pattern around the Arctic region.An additional experiment suggests that the projected Arctic warming may in return warm the TP,thus forming a bi-directional linkage between these two climate systems.Given their association with vast ice reservoirs,the elucidation of this mechanism in our study is crucial in advancing our comprehension of Earth system climate projections.
基金This work was financially supported by the National Basic Research Program of China （No. 2013CB934304）, the CAS/SAFEA International Partnership Program for Creative Research Teams, the National NaturalScience Foundation of China （Nos. 21303211, 11274312 and 51472245）.
文摘The surface topography of noble metal particles is a significant factor in tailoring surface-enhanced Raman scattering （SERS） properties. Here, we present a simple fabrication route to hexagonally arranged arrays of surface-roughened urchin- like Ag hemispheres （Ag-HSs） decorated with Ag nanoparticles （Ag-NPs） for highly active and reproducible SERS substrates. The urchin-like Ag-HS arrays are achieved by sputtering Ag onto the top surface of a highly ordered porous anodic aluminum oxide （AAO） template to form ordered arrays of smooth Ag-HSs and then by electrodepositing Ag-NPs onto the surface of each Ag-HS. Owing to the ordered arrangement of the Ag-HSs and the improved surface roughness, the urchin-like hierarchical Ag-HS arrays can provide sufficient and uniform ＂hot spots＂ for reproducible and highly active SERS effects. Using the urchin-like Ag-HS arrays as SERS substrates, 10-7 M dibutyl phthalate （a member of plasticizers family） and 1.5 × 10-5 M PCB-77 （one congener of polychlorinated biphenyl, a notorious class of pollutants） are identified, showing promising potential for these substrates in the rapid recognition of organic pollutants.
基金an Albert Einstein Professorship to N.C.Stenseth,a cooperation grant(GJHZ0701-7)supported by the Chinese Academy of Sciences.
文摘Plague has caused the death of hundreds of millions of people throughout the human history.Today this disease is again re-emerging and hence is again becoming an increasing threat to human health in several parts of the world.However,impacts of global climate variation(e.g.El Nino and Southern Oscillation[ENSO])and global warming on plagues are largely unknown.Using cross-spectral analysis and cross-wavelet analysis,we have analyzed the relationship between increase rate of human plague in China during 1871–2003 and the following climate factors(as measured by the Southern Oscillation Index[SOI],Sea Surface Temperature of east Pacific equator[SST]and air Temperature of the Northern Hemisphere[NHT]).We found in the frequency domain that increase rate of human plague was closely associated with SOI and SST.Cross-spectral analysis reveals that significant coherencies between increase rate of human plague and ENSO were found over short periods(2–3 years),medium periods(6–7 years)and long periods(11–12 years,30–40 years).Cross-wavelet analysis reveals that increase rate of human plague oscillates in phase with SOI,but in anti-phase with SST over periods of 2–4 years and approximately 8 years(6–10 years).These results indicate that ENSO-driven climate variation may be important for occurrences of human plague in China.However,there is a need for a further analysis of the underlying mechanism between human plague in China and ENSO.
基金the National Natural Science Foundation of China(32272417)the National Key Research and Development Program of China(2018YFC1602802)+1 种基金the Natural Science Foundation of Fujian Province,China(2020J01681)the Open Project of PCOSS,Xiamen University,China(201926).
文摘Although surface-enhanced Raman spectroscopy(SERS)substrates have achieved high sensitivity,it is still difficult to apply these SERS protocols to the on-site detection of real samples due to the SERS substrate being fabrication-complexed,unstable,reproducible,or unable to be applied in batch production.Here,a large-scale ordered two-dimensional array of Au nano-hemispheres was developed through electron beam vaporization of Au onto the easy-available commercialized anodic aluminum oxide(AAO)template with two-layer nanostructures of different diameters.The uniform Au nano-hemisphere is reliable for SERS detection of malachite green(MG)due to the relative standard deviation(RSD)of the SERS intensities at different locations less than 10%.With the optimized excitation wavelength,solvent effect and pH environment,the linear range of MG detection spans from 10^(-10) to 10^(-6) mol/L with a limit of detection(LOD)of 4×10^(-10) mol/L.The enhancement factor can reach 1.2×10^(6).After extraction with acetonitrile and dichloromethane,MG in the spiked tilapia was detected with satisfactory recovery.The results indicate that the Au nano-hemisphere array can be expected to greatly facilitate SERS practical applications in detecting harmful food additives and chemicals due to the advantages of chemical inertness,physical robustness,simple fabrication,controllability,large-area uniformity,and large-batch production.
基金supported by the National Natural Science Foundation of China (40972017)the Knowledge Innovative Program of the Chinese Academy of Sciences (KZCX2-YW-159 and XDA05130100)the International Cooperation Program of MST of China (2009DFB20580)
文摘Endocasts are important materials used for the study of human brain evolution,and allow examination of the external features of brain anatomy from the inside the cranium.Studies examining brain asymmetries in fossil hominids are usually limited to scoring of differences in hemisphere protrusion rostrally and caudally,or to comparing the width of the hemispheres.In the present study,using 3D laser scanning,we examined asymmetries of the hemisphere volumes and surface areas in the Zhoukoudain (ZKD) Homo erectus,dated to 0.4-0.8 Ma.Compared with modern endocasts,we found that the absolute hemisphere volumes and surface areas exhibited no significant asymmetries in the ZKD or in modern specimens.However,the relative hemisphere volumes against surface areas differed between the two groups.When comparing the relative sizes between the left and right hemispheres,the ZKD specimens exhibited a greater variation than in the modern humans;there were no differences in the two hemispheres in the ZKD specimens,while in the modern endocasts the left hemisphere was significantly greater than the right hemisphere.These data suggest that brain asymmetries originated from relative brain sizes rather than absolute brain volumes during human evolution.These anatomical changes are likely related to the origin of human brain lateralization.
文摘The assumption of M. Milankovich about the constancy of the Earth's albedo during the interglacial period was replaced with the alternative one. The model was developed where anomalies of the average annual temperature of the surface atmosphere were related with interannual changes in the planetary albedo and the thermal inertia of the hydrosphere. The surface temperature changes due to albedo actual and model changes were calculated. Possible external causes of albedo changes were considered.
