This paper provides a synthetic review of researches on Meishan Section D, the Global Stratotype Section and Point of the Permian-Triassic Boundary （PTB）. The history of research, geographic and geological setting o...This paper provides a synthetic review of researches on Meishan Section D, the Global Stratotype Section and Point of the Permian-Triassic Boundary （PTB）. The history of research, geographic and geological setting of the section are briefly introduced. Changhsingian to ＂Griesbachian＂ conodont and ammonoid zonations, the most perfect Permo-Triassic zonations over the world, are presented, with a short discussion on the age of Otoceras, The Changhsingian to ＂Griesbachian＂ strata are subdivided into three 3rd order sequences, and the sedimentary structure of each sequence is indicated. The paper presents a correlation of the Changhsingian to ＂Griesbachian＂ magneetostratigraphy of the Meishan section with the general scale, and informed the negation of a short magnetic reversal at the PTB suggested by Zhu and Liu （1999）. Recent developments of chemostratigraphy of δ^13C and δ^34S are introduced, especially the discovery of more than one negative δ^13C excursions across the PTB. Two important molecular researches reveal the profound changes at the base of eco-system, the microbial catastrophy, and the euxinic conditions in the photic zone during the Permian-Triassic superanoxic event. The paper reports the changes in dating the age of PTB since 2001. According to recent achievements, the age of volcanogenic claybed 25, 14 cm below the PTB, is now set at 252.4±0.3 Ma. A discussion on the eventostratigraphy concludes that, although there is a major event episode at beds 25-26, the events across the PTB at Meishan are multi-episodic and commenced prior to the Event Beds 25-26, thus the possibility that the mass extinction was mainly induced by an exterrestrial impact is largely excluded.展开更多
This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point （GSSP） and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, ...This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point （GSSP） and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, northwestern Hunan is ratified as the boundary stratotype for the base of the global Guzhangian Stage, which is the upmost stage of an unnamed series termed provisionally as Cambrian Series 3. The GSSP position lies 121.3 m above the base of the Huaqiao Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Lejopyge leavigata.The Duibian B section at Duibian village, Jiangshan, western Zhejiang, is proposed as the boundary stratotype for the base of the proposed global Jiangshanian Stage that is the second stage of the Furongian Series. The proposed GSSP position lies 108.12 m above the base of the Huayansi Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalius. This horizon is also with the first appearance of the cosmopolitan polymerid trilobite lrvingella angustilimbata.展开更多
After the establishment of the global stratotype section and point (GSSP) of the Permian Triassic boundary (PTB), the definition of the accessory section and point (ASP) of the terrestrial Permian Triassic boundary ...After the establishment of the global stratotype section and point (GSSP) of the Permian Triassic boundary (PTB), the definition of the accessory section and point (ASP) of the terrestrial Permian Triassic boundary (TPTB) is now on the agenda. However, all good TPTB sections so far known have the following shortcomings: (1) the exact TPTB horizon is difficult to define paleontologically with high resolution, and (2) accurate correlation between marine and terrestrial PTBs is hard to attain. In order to enhance the understanding of the nature of the global life crisis in both the marine and terrestrial environments across the Paleozoic Mesozoic transition, these shortcomings need to be addressed. In western Guizhou and eastern Yunnan, Southwest China, some fossiliferous PTB sections which include marine, paralic and terrestrial are well developed, allowing bed to bed correlation of the PTB sequences. Fortunately, the marine PTB sequence in this area is almost the same as found at the Meishan Section, where the GSSP of the PTB is located, which may provide a reliable auxiliary marker for high resolution demarcation of the TPTB. These features found in western Guizhou and eastern Yunnan make this area a good place to study the ASP of the TPTB, so we propose to study the ASP of the TPTB in this area.展开更多
Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there ...Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there are many disagreements among existing boundary definition proposals,each of which has disadvantages. Declinognathodus donetzianus is easily recognized but somewhat limited in its paleogeographic distribution. Idiognathoides postsulcatus is slightly more widespread, but it is less easily identified and its occurrences may be diachronous from region to region. Diplognathodus ellesmerensis is easily recognized and even more widespread, but it is usually rare and its ancestry is not adequately known. The Naqing Section of South Guizhou, South China contains diverse conodont evolutionary lineages among different taxa, including Idiognathoides, Idiognathodus, Diplognathodus,Neognathodus, Gondolella and Mesogondolella. There are numerous transitional forms in almost every lineage of the Naqing section, which shows that the prospects for South China to play a critical role in determining the basal Moscovian Stage definition are good.展开更多
The concept of finitely continuous topological space is introduced and the basic properties of the space are given. Several continuous selection theorems and fixed point theorems for Ф-maps are established, and as ap...The concept of finitely continuous topological space is introduced and the basic properties of the space are given. Several continuous selection theorems and fixed point theorems for Ф-maps are established, and as applications of the above fixed point theorems, some section problems are discussed. The results generalize and improve many corresponding conclusions.展开更多
目的系统评价剖宫产术中不同时机行血管介入阻断对凶险性前置胎盘患者及胎儿的影响。方法采用计算机检索PubMed、Embase、Medline、Web of Science、维普、万方数据库、中国知网、中国生物医学文献数据库等中不同时机行血管介入阻断对...目的系统评价剖宫产术中不同时机行血管介入阻断对凶险性前置胎盘患者及胎儿的影响。方法采用计算机检索PubMed、Embase、Medline、Web of Science、维普、万方数据库、中国知网、中国生物医学文献数据库等中不同时机行血管介入阻断对凶险性前置胎盘的相关研究。检索时限为建库至2024年3月1日,由两名研究员独立筛选随机对照或回顾性文献、提取数据,选用Review Manager 5.4.1软件分析,参照Cochrane协作网提供的偏倚风险评估工具对文献质量进行评估。结果共纳入12篇目标文献,1030例凶险性前置胎盘患者。Meta分析结果显示,胎儿娩出前阻断可降低术后子宫切除率(OR=0.54,95%CI:0.33~0.89)和术后入住ICU病房率(OR=0.34,95%CI:0.19~0.63),但不能降低序贯子宫动脉栓塞率(OR=0.61,95%CI:0.28~1.32)。此外,对胎儿1 min Apgar评分(MD=0.11,95%CI:-0.23~0.46)、5 min Apgar评分(MD=0.10,95%CI:-0.04~0.24)、1 min Apgar评分≤7分(OR=0.81,95%CI:0.36~1.85)、5 min Apgar评分≤7分(OR=0.93,95%CI:0.33~2.63)无明显影响。结论胎儿娩出前介入阻断的临床价值更高,且不会增加胎儿不良结局。展开更多
基金The work was supported by the National Natural Science Foundation of China(project no.40232025).
文摘This paper provides a synthetic review of researches on Meishan Section D, the Global Stratotype Section and Point of the Permian-Triassic Boundary （PTB）. The history of research, geographic and geological setting of the section are briefly introduced. Changhsingian to ＂Griesbachian＂ conodont and ammonoid zonations, the most perfect Permo-Triassic zonations over the world, are presented, with a short discussion on the age of Otoceras, The Changhsingian to ＂Griesbachian＂ strata are subdivided into three 3rd order sequences, and the sedimentary structure of each sequence is indicated. The paper presents a correlation of the Changhsingian to ＂Griesbachian＂ magneetostratigraphy of the Meishan section with the general scale, and informed the negation of a short magnetic reversal at the PTB suggested by Zhu and Liu （1999）. Recent developments of chemostratigraphy of δ^13C and δ^34S are introduced, especially the discovery of more than one negative δ^13C excursions across the PTB. Two important molecular researches reveal the profound changes at the base of eco-system, the microbial catastrophy, and the euxinic conditions in the photic zone during the Permian-Triassic superanoxic event. The paper reports the changes in dating the age of PTB since 2001. According to recent achievements, the age of volcanogenic claybed 25, 14 cm below the PTB, is now set at 252.4±0.3 Ma. A discussion on the eventostratigraphy concludes that, although there is a major event episode at beds 25-26, the events across the PTB at Meishan are multi-episodic and commenced prior to the Event Beds 25-26, thus the possibility that the mass extinction was mainly induced by an exterrestrial impact is largely excluded.
基金supported by the Ministry of Science and Technology of China (2006FY120300)the State Key Laboratory of Palaeobiology and Stratigraphy (20091103)funded by the National Natural Science Foundation of China (40072003, 40023002, 40332018, 40672023, 40602002)
文摘This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point （GSSP） and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, northwestern Hunan is ratified as the boundary stratotype for the base of the global Guzhangian Stage, which is the upmost stage of an unnamed series termed provisionally as Cambrian Series 3. The GSSP position lies 121.3 m above the base of the Huaqiao Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Lejopyge leavigata.The Duibian B section at Duibian village, Jiangshan, western Zhejiang, is proposed as the boundary stratotype for the base of the proposed global Jiangshanian Stage that is the second stage of the Furongian Series. The proposed GSSP position lies 108.12 m above the base of the Huayansi Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalius. This horizon is also with the first appearance of the cosmopolitan polymerid trilobite lrvingella angustilimbata.
文摘After the establishment of the global stratotype section and point (GSSP) of the Permian Triassic boundary (PTB), the definition of the accessory section and point (ASP) of the terrestrial Permian Triassic boundary (TPTB) is now on the agenda. However, all good TPTB sections so far known have the following shortcomings: (1) the exact TPTB horizon is difficult to define paleontologically with high resolution, and (2) accurate correlation between marine and terrestrial PTBs is hard to attain. In order to enhance the understanding of the nature of the global life crisis in both the marine and terrestrial environments across the Paleozoic Mesozoic transition, these shortcomings need to be addressed. In western Guizhou and eastern Yunnan, Southwest China, some fossiliferous PTB sections which include marine, paralic and terrestrial are well developed, allowing bed to bed correlation of the PTB sequences. Fortunately, the marine PTB sequence in this area is almost the same as found at the Meishan Section, where the GSSP of the PTB is located, which may provide a reliable auxiliary marker for high resolution demarcation of the TPTB. These features found in western Guizhou and eastern Yunnan make this area a good place to study the ASP of the TPTB, so we propose to study the ASP of the TPTB in this area.
基金supported by the Ministry of Science and Technology of China (2006FY120300-8)the Chinese Academy of Sciences (KZCX2-YW-122, KZCX2-YW-Q050603)National Natural Science Foundation of China (NSFC), and the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there are many disagreements among existing boundary definition proposals,each of which has disadvantages. Declinognathodus donetzianus is easily recognized but somewhat limited in its paleogeographic distribution. Idiognathoides postsulcatus is slightly more widespread, but it is less easily identified and its occurrences may be diachronous from region to region. Diplognathodus ellesmerensis is easily recognized and even more widespread, but it is usually rare and its ancestry is not adequately known. The Naqing Section of South Guizhou, South China contains diverse conodont evolutionary lineages among different taxa, including Idiognathoides, Idiognathodus, Diplognathodus,Neognathodus, Gondolella and Mesogondolella. There are numerous transitional forms in almost every lineage of the Naqing section, which shows that the prospects for South China to play a critical role in determining the basal Moscovian Stage definition are good.
文摘The concept of finitely continuous topological space is introduced and the basic properties of the space are given. Several continuous selection theorems and fixed point theorems for Ф-maps are established, and as applications of the above fixed point theorems, some section problems are discussed. The results generalize and improve many corresponding conclusions.
文摘目的系统评价剖宫产术中不同时机行血管介入阻断对凶险性前置胎盘患者及胎儿的影响。方法采用计算机检索PubMed、Embase、Medline、Web of Science、维普、万方数据库、中国知网、中国生物医学文献数据库等中不同时机行血管介入阻断对凶险性前置胎盘的相关研究。检索时限为建库至2024年3月1日,由两名研究员独立筛选随机对照或回顾性文献、提取数据,选用Review Manager 5.4.1软件分析,参照Cochrane协作网提供的偏倚风险评估工具对文献质量进行评估。结果共纳入12篇目标文献,1030例凶险性前置胎盘患者。Meta分析结果显示,胎儿娩出前阻断可降低术后子宫切除率(OR=0.54,95%CI:0.33~0.89)和术后入住ICU病房率(OR=0.34,95%CI:0.19~0.63),但不能降低序贯子宫动脉栓塞率(OR=0.61,95%CI:0.28~1.32)。此外,对胎儿1 min Apgar评分(MD=0.11,95%CI:-0.23~0.46)、5 min Apgar评分(MD=0.10,95%CI:-0.04~0.24)、1 min Apgar评分≤7分(OR=0.81,95%CI:0.36~1.85)、5 min Apgar评分≤7分(OR=0.93,95%CI:0.33~2.63)无明显影响。结论胎儿娩出前介入阻断的临床价值更高,且不会增加胎儿不良结局。
