Background: Soil organic carbon(SOC) is a large reservoir of terrestrial carbon(C); it consists of different fractions of varying complexity and stability. Partitioning SOC into different pools of decomposability help...Background: Soil organic carbon(SOC) is a large reservoir of terrestrial carbon(C); it consists of different fractions of varying complexity and stability. Partitioning SOC into different pools of decomposability help better predict the trend of changes in SOC dynamics under climate change. Information on how physical fractions and chemical structures of SOC are related to climate and vegetation types is essential for spatial model ing of SOC processes and responses to global change factors.Method: Soil samples were col ected from multiple representative forest sites of three contrasting climatic zones(i.e. cool temperate, warm temperate, and subtropical) in eastern China. Measurements were made on SOC contents and physical fractions of the 0–20 cm soil layer, and the chemical composition of SOC of the 0–5 cm soil layer, along with measurements and compilation of the basic site and forest stand variables. The long-term effects of temperature, litter inputs, soil characteristics and vegetation type on the SOC contents and factions were examined by means of "space for time substitution" approach and statistical analysis.Result: Mean annual temperature(MAT) varied from 2.1 °C at the cool temperate sites to 20.8 °C at the subtropical sites. Total SOC of the 0–20 cm soil layer decreased with increasing MAT, ranging from 89.2 g·kg^(-1) in cool temperate forests to 57.7 g·kg^(-1) in subtropical forests, at an average rate of 1.87% reduction in SOC with a 1 °C increase in MAT.With increasing MAT, the proportions of aromatic C and phenolic C displayed a tendency of decreases, whereas the proportion of alkyl C and A/O-A value(the ratio of alkyl C to the sum of O-alkyl C and acetal C) displayed a tendency of increases. Overall, there were no significant changes with MAT and forest type in either the physical fractions or the chemical composition. Based on the relationship between the SOC content and MAT, we estimate that SOC in the top 20 soil layer of forests potentially contribute 6.58–26.3 Pg C globally to the atmosphere if global MAT increases by 1 °C–4 °C by the end of the twenty-first century, with nearly half of which(cf. 2.87–11.5 Pg C) occurring in the 0–5 cm mineral soils.Conclusion: Forest topsoil SOC content decreased and became chemical y more recalcitrant with increasing MAT,without apparent changes in the physical fractions of SOC.展开更多
In situ measurements of austenite grain growth were made at various temperatures in the range of 1273-1473 K with subsequent isothermal holding time of 3600 s for the Nb-Ti-bearing and Nb-Ti-free high carb on steel by...In situ measurements of austenite grain growth were made at various temperatures in the range of 1273-1473 K with subsequent isothermal holding time of 3600 s for the Nb-Ti-bearing and Nb-Ti-free high carb on steel by using a confocal laser scanning microscope.The solid solute behavior of Nb-Ti carbides during austenitizing process was analyzed.The experimental results indicate that the austenite grains of both steels grow up gradually with increasing the heating temperature and holding time;the size and growth rate of austenite grain of Nb-Ti-bearing high carbon steel are much lower than those of Nb-Ti-free high carbon steel.A large amount of(Nb,Ti)(C,N)nanoparticles are observed in Nb-Tibearing steel,which retain the strong pinning effect on austenite grain boundary.The kinetics model of austenite grain growth of Nb-Ti-bearing steel during isothermal heat treatment is obtained and the predicted values calculated by using the model meet the experimental values very well.展开更多
Four carbonate carbon isotope(δ^(13)C_(carb))excursions are recognized in the Ediacaran Doushantuo Formation in South China,the genesis of which remains disputed.Whereas three of these δ^(13)C_(carb) excursions poss...Four carbonate carbon isotope(δ^(13)C_(carb))excursions are recognized in the Ediacaran Doushantuo Formation in South China,the genesis of which remains disputed.Whereas three of these δ^(13)C_(carb) excursions possibly record secular biogeochemical variations,the other one,namely Weng'an negative carbonate carbon isotope excursion(WANCE)with an age of ca.620 Ma occurs mainly within the northern Yangtze Platform.In this study,a SIMS U-Pb age of ca.620 Ma was documented from continental rift volcanism within the adjacent South Qinling terrane.Its temporal overlap with WANCE suggests a possible causal link.Volcanism-induced seafloor uplift may have prompted DOC oxidation in surficial oxygenated oceans,inducing the occurrence of WANCE.展开更多
Low carbohydrate diet(LCD)and nutrition is a very popular topic in the nutritional scientific literature.Main reason is that it is an old established therapy in intractable epilepsy and there are plenty of positive pr...Low carbohydrate diet(LCD)and nutrition is a very popular topic in the nutritional scientific literature.Main reason is that it is an old established therapy in intractable epilepsy and there are plenty of positive preclinical and sporadic clinical results in other disorders,including certain cancers.The problem is that a)the metabolic background of this therapy is not elucidated enough,b)animal studies and human experiences are sometimes divergent,c)there are negative human results and d)the clinical studies are not comparable because of the wide variety of study design and conclusion regarding the indication,the composition of diet and duration of treatment can not be drawn.This publication reviews the current situation and gives some hints to the solution.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.31470623)the National Basic Research Program of China(Grant No.2011CB403205)
文摘Background: Soil organic carbon(SOC) is a large reservoir of terrestrial carbon(C); it consists of different fractions of varying complexity and stability. Partitioning SOC into different pools of decomposability help better predict the trend of changes in SOC dynamics under climate change. Information on how physical fractions and chemical structures of SOC are related to climate and vegetation types is essential for spatial model ing of SOC processes and responses to global change factors.Method: Soil samples were col ected from multiple representative forest sites of three contrasting climatic zones(i.e. cool temperate, warm temperate, and subtropical) in eastern China. Measurements were made on SOC contents and physical fractions of the 0–20 cm soil layer, and the chemical composition of SOC of the 0–5 cm soil layer, along with measurements and compilation of the basic site and forest stand variables. The long-term effects of temperature, litter inputs, soil characteristics and vegetation type on the SOC contents and factions were examined by means of "space for time substitution" approach and statistical analysis.Result: Mean annual temperature(MAT) varied from 2.1 °C at the cool temperate sites to 20.8 °C at the subtropical sites. Total SOC of the 0–20 cm soil layer decreased with increasing MAT, ranging from 89.2 g·kg^(-1) in cool temperate forests to 57.7 g·kg^(-1) in subtropical forests, at an average rate of 1.87% reduction in SOC with a 1 °C increase in MAT.With increasing MAT, the proportions of aromatic C and phenolic C displayed a tendency of decreases, whereas the proportion of alkyl C and A/O-A value(the ratio of alkyl C to the sum of O-alkyl C and acetal C) displayed a tendency of increases. Overall, there were no significant changes with MAT and forest type in either the physical fractions or the chemical composition. Based on the relationship between the SOC content and MAT, we estimate that SOC in the top 20 soil layer of forests potentially contribute 6.58–26.3 Pg C globally to the atmosphere if global MAT increases by 1 °C–4 °C by the end of the twenty-first century, with nearly half of which(cf. 2.87–11.5 Pg C) occurring in the 0–5 cm mineral soils.Conclusion: Forest topsoil SOC content decreased and became chemical y more recalcitrant with increasing MAT,without apparent changes in the physical fractions of SOC.
文摘In situ measurements of austenite grain growth were made at various temperatures in the range of 1273-1473 K with subsequent isothermal holding time of 3600 s for the Nb-Ti-bearing and Nb-Ti-free high carb on steel by using a confocal laser scanning microscope.The solid solute behavior of Nb-Ti carbides during austenitizing process was analyzed.The experimental results indicate that the austenite grains of both steels grow up gradually with increasing the heating temperature and holding time;the size and growth rate of austenite grain of Nb-Ti-bearing high carbon steel are much lower than those of Nb-Ti-free high carbon steel.A large amount of(Nb,Ti)(C,N)nanoparticles are observed in Nb-Tibearing steel,which retain the strong pinning effect on austenite grain boundary.The kinetics model of austenite grain growth of Nb-Ti-bearing steel during isothermal heat treatment is obtained and the predicted values calculated by using the model meet the experimental values very well.
基金supported by the National Natural Science Foundation of China(No.41673016)the State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences(No.SKL-Z202001)+2 种基金the State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences(No.193112)the State Key Laboratory of Geological Processes and Mineral ResourcesChina University of Geosciences(No.GPMR201902)。
文摘Four carbonate carbon isotope(δ^(13)C_(carb))excursions are recognized in the Ediacaran Doushantuo Formation in South China,the genesis of which remains disputed.Whereas three of these δ^(13)C_(carb) excursions possibly record secular biogeochemical variations,the other one,namely Weng'an negative carbonate carbon isotope excursion(WANCE)with an age of ca.620 Ma occurs mainly within the northern Yangtze Platform.In this study,a SIMS U-Pb age of ca.620 Ma was documented from continental rift volcanism within the adjacent South Qinling terrane.Its temporal overlap with WANCE suggests a possible causal link.Volcanism-induced seafloor uplift may have prompted DOC oxidation in surficial oxygenated oceans,inducing the occurrence of WANCE.
文摘Low carbohydrate diet(LCD)and nutrition is a very popular topic in the nutritional scientific literature.Main reason is that it is an old established therapy in intractable epilepsy and there are plenty of positive preclinical and sporadic clinical results in other disorders,including certain cancers.The problem is that a)the metabolic background of this therapy is not elucidated enough,b)animal studies and human experiences are sometimes divergent,c)there are negative human results and d)the clinical studies are not comparable because of the wide variety of study design and conclusion regarding the indication,the composition of diet and duration of treatment can not be drawn.This publication reviews the current situation and gives some hints to the solution.
