Sediments are one of the main carbon sinks in subduction zones,with CaCO_(3)and SiO_(2)being the main components in sediments.Their chemical stability plays a significant role in the form of carbon in the Earth’s man...Sediments are one of the main carbon sinks in subduction zones,with CaCO_(3)and SiO_(2)being the main components in sediments.Their chemical stability plays a significant role in the form of carbon in the Earth’s mantle.Here we report the reactions of CaCO_(3)with SiO_(2)in hydrated sediments at 0.8-2.0 GPa,400-500℃and redox-buffered conditions relevant to shallow subduction zones.Our results show that the reaction CaCO_(3)+SiO_(2)=CaSiO_(3)+C+O_(2)(fluid)occurs under CoCoO and IW buffered conditions to generate wollastonite(CaSiO_(3))and carbonaceous material(CM).Moreover,wollastonite is formed by the dissolution-crystallization process,which may be significantly affected by oxygen fugacity,leading to distinct crystallization habits(Yui,1966,Schott et al.,2012).Anhydrous experiments indicate that the reaction proceeds only in the presence of H2O within the pressure and temperature(P-T)range of this study.The reaction occurs more rapidly with aragonite-structured than calcite-structured CaCO_(3).Further,the experiment buffered with natural olivine at 1.0 GPa and 400℃proves that the above reaction can occur during serpentinization processes in shallow subduction zones.More importantly,nanoscale CM may be generated under relatively reducing conditions,exhibiting Raman characteristics of kerogen.These results provide new insights into how deep carbon is distributed in the Earth’s interior.展开更多
Background Gestational diabetes mellitus （GDM） is a common complication during pregnancy,and gestational weight gain is one of the major and modifiable risk factors.This study aims to estimate the relationship betwe...Background Gestational diabetes mellitus （GDM） is a common complication during pregnancy,and gestational weight gain is one of the major and modifiable risk factors.This study aims to estimate the relationship between the rate of gestational weight gain before diagnosis of GDM and the subsequent risk of GDM.Methods A case-control study was conducted with 90 GDM cases and 165 women in the control group from May 2012 to August 2012 at Peking University First Affiliated Hospital.GDM was diagnosed according to the standards issued by the Ministry of Health of China in 2011.The plasma glucose levels,weights,and covariate data of the women were obtained based on medical records.Univariate analysis and unconditional Logistic regression model were used to estimate the associations.Results After adjusting for age at delivery,parity,and pre-pregnancy body mass index,the risk of GDM increased with increasing rates of gestational weight gain.Compared with the lower rate of gestational weight gain （less than 0.28 kg per week）,a rate of weight gain of 0.28 kg per week or more was associated with increased risk of GDM （odds ratio：2.03; 95％ confidence interval：1.15 to 3.59）.The association between the rate of gestational weight gain and GDM was primarily attributed to the increased weight gain in the first trimester.Conclusion High rates of gestational weight gain,particular during early pregnancy,may increase a woman＇s risk of GDM.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2023YFF0804100)the United Laboratory of High-Pressure Physics and Earthquake Science(Grant No.2022HPPES01)Some experiments are supported by the Synergic Extreme Condition User Facility(SECUF).
文摘Sediments are one of the main carbon sinks in subduction zones,with CaCO_(3)and SiO_(2)being the main components in sediments.Their chemical stability plays a significant role in the form of carbon in the Earth’s mantle.Here we report the reactions of CaCO_(3)with SiO_(2)in hydrated sediments at 0.8-2.0 GPa,400-500℃and redox-buffered conditions relevant to shallow subduction zones.Our results show that the reaction CaCO_(3)+SiO_(2)=CaSiO_(3)+C+O_(2)(fluid)occurs under CoCoO and IW buffered conditions to generate wollastonite(CaSiO_(3))and carbonaceous material(CM).Moreover,wollastonite is formed by the dissolution-crystallization process,which may be significantly affected by oxygen fugacity,leading to distinct crystallization habits(Yui,1966,Schott et al.,2012).Anhydrous experiments indicate that the reaction proceeds only in the presence of H2O within the pressure and temperature(P-T)range of this study.The reaction occurs more rapidly with aragonite-structured than calcite-structured CaCO_(3).Further,the experiment buffered with natural olivine at 1.0 GPa and 400℃proves that the above reaction can occur during serpentinization processes in shallow subduction zones.More importantly,nanoscale CM may be generated under relatively reducing conditions,exhibiting Raman characteristics of kerogen.These results provide new insights into how deep carbon is distributed in the Earth’s interior.
文摘Background Gestational diabetes mellitus （GDM） is a common complication during pregnancy,and gestational weight gain is one of the major and modifiable risk factors.This study aims to estimate the relationship between the rate of gestational weight gain before diagnosis of GDM and the subsequent risk of GDM.Methods A case-control study was conducted with 90 GDM cases and 165 women in the control group from May 2012 to August 2012 at Peking University First Affiliated Hospital.GDM was diagnosed according to the standards issued by the Ministry of Health of China in 2011.The plasma glucose levels,weights,and covariate data of the women were obtained based on medical records.Univariate analysis and unconditional Logistic regression model were used to estimate the associations.Results After adjusting for age at delivery,parity,and pre-pregnancy body mass index,the risk of GDM increased with increasing rates of gestational weight gain.Compared with the lower rate of gestational weight gain （less than 0.28 kg per week）,a rate of weight gain of 0.28 kg per week or more was associated with increased risk of GDM （odds ratio：2.03; 95％ confidence interval：1.15 to 3.59）.The association between the rate of gestational weight gain and GDM was primarily attributed to the increased weight gain in the first trimester.Conclusion High rates of gestational weight gain,particular during early pregnancy,may increase a woman＇s risk of GDM.
