【目的】全球变暖背景下,喀斯特地貌广布的西南地区可能面临石漠化加剧的风险,对该区域石漠化演变历史的重建具有重要意义。【方法】通过采自贵州省黔西县黑洞一支石笋(HD12)的29个230Th年龄和954个δ^(13)C数据,重建了该地区过去4 750...【目的】全球变暖背景下,喀斯特地貌广布的西南地区可能面临石漠化加剧的风险,对该区域石漠化演变历史的重建具有重要意义。【方法】通过采自贵州省黔西县黑洞一支石笋(HD12)的29个230Th年龄和954个δ^(13)C数据,重建了该地区过去4 750年的生态环境演变历史。【结果与结论】发现在4 322~3 526 a B.P.以及803~82 a B.P.时段存在两个显著的δ^(13)C正偏移,说明这两个时段洞穴上方的生态环境出现了恶化。HD12石笋δ^(13)C记录在约803 a B.P.的显著偏正持续了约290 a,其振幅达4.2‰,指示了该区域石漠化的扩张过程。这一时期西南地区多个洞穴石笋δ^(13)C值的一致偏正特征,可能指示了宋末靖康事件(823 a B.P.)后,人口的大量迁入和气候的干旱化导致了该区域石漠化的扩张。HD12石笋δ^(13)C值在4 322~3 526 a B.P.时期的偏正,振幅达4.9‰,其中4 322~3 977 a B.P.偏正过程对应于北半球4.2 ka事件,而3 777~3 526 a B.P.的偏正对应3.7 ka事件,两个时期的干旱事件在西南地区的多个石笋与湖泊记录中均有体现,说明在此期间,亚洲夏季风减弱,降水减少可能引起了该区域植被覆盖度大幅降低和土壤严重退化。展开更多
AIM: To evaluate the prognostic value of percentage of 13C-phenylalanine oxidation (13C-PheOx) obtained by 13C-phenylalanine breath test (13C-PheBT) on the survival of patients with chronic liver failure. METHODS: The...AIM: To evaluate the prognostic value of percentage of 13C-phenylalanine oxidation (13C-PheOx) obtained by 13C-phenylalanine breath test (13C-PheBT) on the survival of patients with chronic liver failure. METHODS: The hepatic function was determined by standard liver blood tests and the percentage of 13C-PheOx in 118 chronic liver failure patients. The follow-up period was of 64 mo. Survival analysis was performed by the Kaplan-Meier method and variables that were significant (P < 0.10) in univariate analysis and subsequently introduced in a multivariate analysis according to the hazard model proposed by Cox. RESULTS: Forty-one patients died due to progressive liver failure during the follow-up period. The probability of survival at 12, 24, 36, 48 and 64 mo was 0.88, 0.78, 0.66, 0.57 and 0.19, respectively. Multivariate analysis demonstrated that Child-Pugh classes, age, creatinine and the percentage of 13C-PheOx (HR 0.338, 95% CI: 0.150-0.762, P = 0.009) were independent predictors of survival. When Child-Pugh classes were replaced by all the parameters of the score, only albumin, bilirubin, creatinine, age and the percentage of 13C-PheOx (HR 0.449, 95% CI: 0.206-0.979, P = 0.034) were found to be independent predictors of survival.CONCLUSION: Percentage of 13C-PheOx obtained by 13C-PheBT is a strong predictor of survival in patients with chronic liver disease.展开更多
Tree radial growth can have significantly differ-ent responses to climate change depending on the environ-ment.To elucidate the effects of climate on radial growth and stable carbon isotope(δ^(13)C)fractionation of Q...Tree radial growth can have significantly differ-ent responses to climate change depending on the environ-ment.To elucidate the effects of climate on radial growth and stable carbon isotope(δ^(13)C)fractionation of Qing-hai spruce(Picea crassifolia),a widely distributed native conifer in northwestern China in different environments,we developed chronologies for tree-ring widths and δ^(13)C in trees on the southern and northern slopes of the Qilian Mountains,and analysed the relationship between these tree-ring variables and major climatic factors.Tree-ring widths were strongly influenced by climatic factors early in the growing season,and the radial growth in trees on the northern slopes was more sensitive to climate than in trees on the southern.Tree-ring δ^(13)C was more sensitive to climate than radial growth.δ^(13)C fractionation was mainly influenced by summer temperature and precipitation early in the growing season.Stomatal conductance more strongly limited stable carbon isotope fractionation in tree rings than photosynthetic rate did.The response between tree rings and climate in mountains gradually weakened as climate warmed.Changes in radial growth and stable carbon isotope fractionation of P.crassifolia in response to climate in the Qilian Mountains may be further complicated by continued climate change.展开更多
文摘【目的】全球变暖背景下,喀斯特地貌广布的西南地区可能面临石漠化加剧的风险,对该区域石漠化演变历史的重建具有重要意义。【方法】通过采自贵州省黔西县黑洞一支石笋(HD12)的29个230Th年龄和954个δ^(13)C数据,重建了该地区过去4 750年的生态环境演变历史。【结果与结论】发现在4 322~3 526 a B.P.以及803~82 a B.P.时段存在两个显著的δ^(13)C正偏移,说明这两个时段洞穴上方的生态环境出现了恶化。HD12石笋δ^(13)C记录在约803 a B.P.的显著偏正持续了约290 a,其振幅达4.2‰,指示了该区域石漠化的扩张过程。这一时期西南地区多个洞穴石笋δ^(13)C值的一致偏正特征,可能指示了宋末靖康事件(823 a B.P.)后,人口的大量迁入和气候的干旱化导致了该区域石漠化的扩张。HD12石笋δ^(13)C值在4 322~3 526 a B.P.时期的偏正,振幅达4.9‰,其中4 322~3 977 a B.P.偏正过程对应于北半球4.2 ka事件,而3 777~3 526 a B.P.的偏正对应3.7 ka事件,两个时期的干旱事件在西南地区的多个石笋与湖泊记录中均有体现,说明在此期间,亚洲夏季风减弱,降水减少可能引起了该区域植被覆盖度大幅降低和土壤严重退化。
文摘AIM: To evaluate the prognostic value of percentage of 13C-phenylalanine oxidation (13C-PheOx) obtained by 13C-phenylalanine breath test (13C-PheBT) on the survival of patients with chronic liver failure. METHODS: The hepatic function was determined by standard liver blood tests and the percentage of 13C-PheOx in 118 chronic liver failure patients. The follow-up period was of 64 mo. Survival analysis was performed by the Kaplan-Meier method and variables that were significant (P < 0.10) in univariate analysis and subsequently introduced in a multivariate analysis according to the hazard model proposed by Cox. RESULTS: Forty-one patients died due to progressive liver failure during the follow-up period. The probability of survival at 12, 24, 36, 48 and 64 mo was 0.88, 0.78, 0.66, 0.57 and 0.19, respectively. Multivariate analysis demonstrated that Child-Pugh classes, age, creatinine and the percentage of 13C-PheOx (HR 0.338, 95% CI: 0.150-0.762, P = 0.009) were independent predictors of survival. When Child-Pugh classes were replaced by all the parameters of the score, only albumin, bilirubin, creatinine, age and the percentage of 13C-PheOx (HR 0.449, 95% CI: 0.206-0.979, P = 0.034) were found to be independent predictors of survival.CONCLUSION: Percentage of 13C-PheOx obtained by 13C-PheBT is a strong predictor of survival in patients with chronic liver disease.
基金supported by Basic Research Operating Expenses of the Central level Non-profit Research Institutes (IDM2022003)National Natural Science Foundation of China (42375054)+2 种基金Regional collaborative innovation project of Xinjiang (2021E01022,2022E01045)Young Meteorological Talent Program of China Meteorological Administration,Tianshan Talent Program of Xinjiang (2022TSYCCX0003)Youth Innovation Team of China Meteorological Administration (CMA2023QN08).
文摘Tree radial growth can have significantly differ-ent responses to climate change depending on the environ-ment.To elucidate the effects of climate on radial growth and stable carbon isotope(δ^(13)C)fractionation of Qing-hai spruce(Picea crassifolia),a widely distributed native conifer in northwestern China in different environments,we developed chronologies for tree-ring widths and δ^(13)C in trees on the southern and northern slopes of the Qilian Mountains,and analysed the relationship between these tree-ring variables and major climatic factors.Tree-ring widths were strongly influenced by climatic factors early in the growing season,and the radial growth in trees on the northern slopes was more sensitive to climate than in trees on the southern.Tree-ring δ^(13)C was more sensitive to climate than radial growth.δ^(13)C fractionation was mainly influenced by summer temperature and precipitation early in the growing season.Stomatal conductance more strongly limited stable carbon isotope fractionation in tree rings than photosynthetic rate did.The response between tree rings and climate in mountains gradually weakened as climate warmed.Changes in radial growth and stable carbon isotope fractionation of P.crassifolia in response to climate in the Qilian Mountains may be further complicated by continued climate change.
