The black shale series that formed in the Edi- acaran-Cambrian transition are important stratigraphic records of the co-evolution of the paleo-ocean, -climate, and -biology. In this study, we measured Re-Os isotopic c...The black shale series that formed in the Edi- acaran-Cambrian transition are important stratigraphic records of the co-evolution of the paleo-ocean, -climate, and -biology. In this study, we measured Re-Os isotopic compositions of the black shale in the Niutitang Formation from the Gezhongwu section in Zhijin, Guizhou Province. The samples had high Re and Os contents, with Re ranging from 21.27 to 312.78 ng/g and Os ranging from 0.455 to 7.789 ng/g. The Re-Os isotope isochron age of 522.9 ± 8.6 Ma implies deposition of the Niutitang black shale predated the Chengjiang Fauna, providing an age constraint for the expansion of oceanic anoxia in the study area. The initial ^187Os/^188Os ratio of 0.826 ± 0.026 indi- cates that enhanced continental weathering might have triggered the expansion of the oceanic anoxia.展开更多
Noncontact optical thermometers have attracted widespread attention,but existing problems such as single-mode and low-sensitivity thermometers still urgently need to be solved.Herein,a novel multiple-mode thermometer ...Noncontact optical thermometers have attracted widespread attention,but existing problems such as single-mode and low-sensitivity thermometers still urgently need to be solved.Herein,a novel multiple-mode thermometer was designed for the polymorphism LaSc_(3)(BO_(3))_(4):Eu^(2+/3+),Li^(+).X-ray diffraction(XRD)patterns revealed a slight transition betweenα-andβ-phases with the concentrations of the dopants,which is further proved by structure refinements and first-principles calculations.The coexistence of Eu^(2+)and Eu^(3+)in the phosphors and their relative percentages were confirmed by X-ray absorption near-edge structure(XANES)spectra.Benefiting from appropriate emissions from Eu^(2+)and Eu^(3+)without obvious energy transfer and their opposite changing trends with temperatures under 307 nm excitation,a triple-mode optical thermometer is obtained for this material within the temperature range of 150–450 K.The highest sensitivities of 27.65,14.05,and 7.68%·K^(−1)are achieved based on two fluorescence intensity ratio(FIR)modes of Eu^(2+)and Eu^(3+)(5d–4f/^(5)D_(0)–^(7)F_(2,4))and the fluorescence lifetime(FL)mode of Eu^(2+),respectively.To the best of our knowledge,the former is almost the highest in Eu^(2+)and Eu^(3+)co-doped thermometers.These results indicate that this material may be used as an excellent multiple-mode optical thermometer.展开更多
Two-dimensional(2D)transition metal chalcogenides(TMCs)are known to be susceptible to the atmosphere,which greatly obscures the intrinsic physical and chemical properties.The quantitative origin of the instability on ...Two-dimensional(2D)transition metal chalcogenides(TMCs)are known to be susceptible to the atmosphere,which greatly obscures the intrinsic physical and chemical properties.The quantitative origin of the instability on the atomic scale has not been well investigated due to the lack of environmentally stable TMCs sample.Here,we find the stability of the grown TMCs is strongly relevant to their initial element ratios,and thus the stoichiometric bonded TMCs have favorable stability,benefitted from the TMCs with controllable chalcogenisation.In this study,the degree of structural degradation has been quantitatively defined by the reduced element ratio of chalcogen to metal through the time-dependent characterizations,and the non-stoichiometric ratios in TMCs reveal the atomic lattices with point defects like additive bonds or vacancies inside.This study not only provides a potential view to fabricate environmentally stable TMCs based devices,but also will bring an effective feasibility of stacking stable vertical heterostructures.展开更多
This article deals with some properties of Galton-Watson branching processes in varying environments. A necessary and suffcient condition for relative recurrent state is presented, and a series of ratio limit properti...This article deals with some properties of Galton-Watson branching processes in varying environments. A necessary and suffcient condition for relative recurrent state is presented, and a series of ratio limit properties of the transition probabilities are showed.展开更多
基金supported by the China Geological Survey (DD20160346)the National Natural Science Foundation of China (41472089)the Guizhou Geological Prospecting Fund (2016091)
文摘The black shale series that formed in the Edi- acaran-Cambrian transition are important stratigraphic records of the co-evolution of the paleo-ocean, -climate, and -biology. In this study, we measured Re-Os isotopic compositions of the black shale in the Niutitang Formation from the Gezhongwu section in Zhijin, Guizhou Province. The samples had high Re and Os contents, with Re ranging from 21.27 to 312.78 ng/g and Os ranging from 0.455 to 7.789 ng/g. The Re-Os isotope isochron age of 522.9 ± 8.6 Ma implies deposition of the Niutitang black shale predated the Chengjiang Fauna, providing an age constraint for the expansion of oceanic anoxia in the study area. The initial ^187Os/^188Os ratio of 0.826 ± 0.026 indi- cates that enhanced continental weathering might have triggered the expansion of the oceanic anoxia.
基金financially supported by the National Natural Science Foundation of China(Nos.51972347 and 21771195).
文摘Noncontact optical thermometers have attracted widespread attention,but existing problems such as single-mode and low-sensitivity thermometers still urgently need to be solved.Herein,a novel multiple-mode thermometer was designed for the polymorphism LaSc_(3)(BO_(3))_(4):Eu^(2+/3+),Li^(+).X-ray diffraction(XRD)patterns revealed a slight transition betweenα-andβ-phases with the concentrations of the dopants,which is further proved by structure refinements and first-principles calculations.The coexistence of Eu^(2+)and Eu^(3+)in the phosphors and their relative percentages were confirmed by X-ray absorption near-edge structure(XANES)spectra.Benefiting from appropriate emissions from Eu^(2+)and Eu^(3+)without obvious energy transfer and their opposite changing trends with temperatures under 307 nm excitation,a triple-mode optical thermometer is obtained for this material within the temperature range of 150–450 K.The highest sensitivities of 27.65,14.05,and 7.68%·K^(−1)are achieved based on two fluorescence intensity ratio(FIR)modes of Eu^(2+)and Eu^(3+)(5d–4f/^(5)D_(0)–^(7)F_(2,4))and the fluorescence lifetime(FL)mode of Eu^(2+),respectively.To the best of our knowledge,the former is almost the highest in Eu^(2+)and Eu^(3+)co-doped thermometers.These results indicate that this material may be used as an excellent multiple-mode optical thermometer.
基金the MoSe2 samples by MBE.This work was supported by the National Key R&D Program of China(No.2018YFA0305800)the Fundamental Research Funds for the Central Universities(Nos.020414380145 and 020414380153)+2 种基金the National Natural Science Foundation of China(Nos.11674154,11761131010,51972163,and 11904163)the Natural Science Foundation of Jiangsu Province(No.BK20190010)the Fok Ying-Tong Education Foundation of China(No.171038)。
文摘Two-dimensional(2D)transition metal chalcogenides(TMCs)are known to be susceptible to the atmosphere,which greatly obscures the intrinsic physical and chemical properties.The quantitative origin of the instability on the atomic scale has not been well investigated due to the lack of environmentally stable TMCs sample.Here,we find the stability of the grown TMCs is strongly relevant to their initial element ratios,and thus the stoichiometric bonded TMCs have favorable stability,benefitted from the TMCs with controllable chalcogenisation.In this study,the degree of structural degradation has been quantitatively defined by the reduced element ratio of chalcogen to metal through the time-dependent characterizations,and the non-stoichiometric ratios in TMCs reveal the atomic lattices with point defects like additive bonds or vacancies inside.This study not only provides a potential view to fabricate environmentally stable TMCs based devices,but also will bring an effective feasibility of stacking stable vertical heterostructures.
基金supported by NNSF of China(6053408070571079)Open Fundation of SKLSE of Wuhan University (2008-07-03)
文摘This article deals with some properties of Galton-Watson branching processes in varying environments. A necessary and suffcient condition for relative recurrent state is presented, and a series of ratio limit properties of the transition probabilities are showed.
