检索结果-南通市图书馆

Developmental sequence of Cambrian embryo Markuelia

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2007年第7期52卷 929-935页

作者： dong xiping1,2.1 school of earth and space sciences, peking university, beijing 100871, china 2 Laboratory of Palaeobiology & Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of sciences, Nan-jing 210008, china (email: dongxp@***) school of earth and space sciences Peking University Beijing 100871 China

Based on more exquisitely preserved specimens of Markuelia hunanensis recently recovered from Middle and Upper Cambrian in western Hunan and in the light of Synchrotron radiation X-ray tomo-graphic microscopy, the developmental sequence from cleavage through organogenesis to the pre-hatching of Cambrian embryo Markuelia, especially the developmental sequence during the pre-hatching stage, i.e. from the earliest period when the scalids and tail spines only took shape to the latest period (just about hatching), is established. This developmental sequence provides a pattern of embryonic development during the pre-hatching stage, which has not been established in the living scalidophorans (priapulids, loriciferans and kinorhynchs). Thus, it not only enriches our knowledge on the embryonic development of the extant descendants of Markuelia, but also opens a new window to the evolution and development of the animal.

关键词：寒武纪蠕虫化石胚胎发育序列两侧对称动物胚胎

Affinities and functional morphology of the Middle Cambrian ornamented tubules from West Hunan,china

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2004年第10期14卷 67-71页

作者： ZHU Caifa 1,2 and dong xiping 1 (1.school of earth and space sciences,peking university,beijing100871,china 2.university of Petroleum,beijing102249,china) peking Univ Sch Earth & Space Sci Beijing 100871 Peoples R China Univ Petr Beijing 102249 Peoples R China

Problematic phosphatic tubular microfossils with ornamented sculptures are documented to exist in limestones of the up-per Middle Cambrian Huaqiao Formation at the Paibi section and the Wangcun section in West Hunan,*** morphological pat-terns,including Ornamented Tube Form I and Ornamented Tube Form II are *** on the analysis of the preservation,wall structure and composition of the fossils,it is deduced that these ornamented tubes may represent carapace spines of some Cambrian arthro-pods with phosphatic carapaces,such as bradoriid *** of functional morphology indicates that the sclerites may rather be considered of a defensive than grasping function on the original organism body.

关键词： Middle Cambrian ornamented tubes affinities functional morphology West Hunan

Two new species of Vestrogothia (Phosphatocopina, Crustacea) of Orsten-type preservation from the Upper Cambrian in western Hunan, South china

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china earth sciences 2009年第6期52卷 784-796页

作者： ZHANG HuaQiao1,2 & dong xiping1,2.1 school of earth and space sciences,peking university,beijing 100871,china 2 State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of sciences,Nanjing 210008,china school of earth and space sciences Peking University Beijing 100871 China State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing 210008 China

Although fossils of Orsten-type preservation represented by Skaracarida and Phosphatocopina were first reported from the Middle and Upper Cambrian in western Hunan, South china in 2005, diversified phosphatocopine species have never been appropriately described and elucidated in terms of their evolutionary relationships. Here, we described two new species of Phosphatocopina, Vestrogothia anterispinata sp. nov. and V. bispinata sp. nov. The evolutionary relationship among all the valid species of Phosphatocopina is discussed and the phylogeny of Phosphatocopina is reestablished using cladistic analysis. Accordingly, phosphatocopines primitively evolved along two lineages: one evolved towards the emergence of lobes; the other evolved towards the emergence of dorsal spines. Respectively, lobes originated independently three times, and dorsal spines originated only once. With regard to the dorsal rims, interdorsum originated first, whereas dorsal furrow originated independently twice on the basis of interdorsum. Probably Hesslandona may represent a polyphyletic group, whereas Vestrogothia a monophyletic group.

关键词： fossils of Orsten-type preservation Vestrogothia Phosphatocopina Crustacea evolution phylogeny Cambrian Hunan

The developmental trend of labrum and median eyes of Orsten-type preserved Phosphatocopina (Crustacea)

在线全文

学校读者我要写书评

暂无评论

Science china earth sciences 2010年第1期53卷 18-26页

作者： LIU Zheng 1,2 & dong xiping 1,2.1 school of earth and space sciences,peking university,beijing 100871,china 2 State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of sciences,Nanjing 210008,china 1. school of earth and space sciences Peking University Beijing 100871 China2. State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing 210008 China

The Phosphatocopina (Crustacea,Arthropoda) is an important group of 'Orsten-type' preserved *** is resolved as the sister-group of *** we study the labrum,the median eyes,and the inner lamella of Phosphatocopina based on the selected specimens respectively from western Hunan,South china,and *** labrum characters of different species exhibit interspecific *** ratio of labrum length/shield length is significant to the reconstruction of the ontogeny of *** labrum characters should be introduced to the diagnosis of *** the earliest growth stage,the median eyes were inconspicuous,almost as flat as the other area of the ***,with the growth of the individuals they became *** were two obviously concave structures on the ventral side of the hypostome in later stages,which were the positions where the median eyes should have been *** addition,the two modes of preservation of the inner lamella,i.e.,that of shrinking and that of bulging up,are interpreted as the preservational artifact herein.

关键词： Phosphatocopina Crustacea Orsten-type preservation morphology ontogeny Cambrian South china Sweden

The internal structure of Early Cambrian fossil embryo Olivooides revealed in the light of Synchrotron X-ray Tomographic Microscopy

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2008年第24期53卷 3860-3865页

作者： CHEN Fang1,2 & dong xiping1,2.1 school of earth and space sciences,peking university,beijing 100871,china 2 Laboratory of Paleontology and Stratigraphy,Nanjing Institute of Geology and Paleontology,Chinese Academy of sciences,Nan-jing 210008,china school of earth and space sciences Peking University Beijing 100871 China Laboratory of Paleontology and Stratigraphy Nanjing Institute of Geology and Paleontology Chinese Academy of Sciences Nanjing 210008 China

Countless fossil embryo Olivooides and the hatched larvae,juveniles and adults(the latter two kinds are Punctatus) are recovered by means of acid maceration from the fine-crystalline to medium-crystalline phosphatic limestone and phosphatic micrite of Early Cambrian Kuanchuanpu Formation at the Shizhonggou section,near Kuanchuanpu Village,Ningqiang County,Shaanxi Province,*** the technique of Synchrotron X-ray Tomographic Microscopy,the 3D internal structure of Olivooides and Punctatus is *** morphological and statistic analyses are also given to the stellae structure of Olivooides and Punctatus,which indicates that this structure is a result of adaptive evolution to a lifestyle of fast-attaching after hatching,probably with the function of mucilage *** internal structure of Punctatus is described and *** ovum-like structure,a common internal feature of Punctatus,is considered as the taphonomic structure,rather than eggs or other biological *** structure is thought to be formed after the burial of the animal and before or during the *** original internal structure of Punctatus is assumed to be tabulae-filled,with soft body grown on them.

关键词：同步加速器 X射线显微镜寒武系化石动物区系内部结构

A continuous and long-term in-situ stress measuring method based on fiber optic. Part I: Theory of inverse differential strain analysis

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第2期21卷 1171-1189页

作者： Kun-Peng Zhang Mian Chen Chang-Jun Zhao Su Wang Yong-dong Fan State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing102249China MOE Key Laboratory of Petroleum Engineering in china university of Petroleum Beijing102249China beijing International Center for Gas Hydrate School of Earth and Space SciencesPeking UniversityBeijing100871China

A method for in-situ stress measurement via fiber optics was proposed. The method utilizes the relationship between rock mass elastic parameters and in-situ stress. The approach offers the advantage of long-term stress measurements with high spatial resolution and frequency, significantly enhancing the ability to measure in-situ stress. The sensing casing, spirally wrapped with fiber optic, is cemented into the formation to establish a formation sensing nerve. Injecting fluid into the casing generates strain disturbance, establishing the relationship between rock mass properties and treatment ***, an optimization algorithm is established to invert the elastic parameters of formation via fiber optic strains. In the first part of this paper series, we established the theoretical basis for the inverse differential strain analysis method for in-situ stress measurement, which was subsequently verified using an analytical model. This paper is the fundamental basis for the inverse differential strain analysis method.

关键词： In-situ stress Fiber optic Orthotropic elastic Differential evolution ABAQUS

Ten key issues for ecological restoration of territorial space

在线全文

学校读者我要写书评

暂无评论

National Science Review 2024年第7期11卷 75-79页

作者： Jian Peng dongmei Xu Zihan Xu Hui Tang Hong Jiang Jianquan dong Yanxu Liu Technology Innovation Center for Integrated Ecosystem Restoration and Sustainable Utilization Ministry of Natural Resources College of Urban and Environmental Sciences Peking University school of Soil and Water Conservation Beijing Forestry University Key Laboratory for Environmental and Urban sciences School of Urban Planning and DesignShenzhen Graduate School Peking University school of Landscape Architecture Beijing Forestry University State Key Laboratory of earth Surface Processes and Resource Ecology Faculty of Geographical Science Beijing Normal University

Ecological restoration is an effective measure to protect biodiversity, sustain ecosystem services and enhance socialecological resilience. It is defined as the process of assisting the recovery of an ecosystem that h... 详细信息

关键词： PRIORITY AREAS

Simultaneous detection of flare-associated kink oscillations and extreme-ultraviolet waves

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china(Technological sciences) 2024年第5期67卷 1592-1601页

作者： LI dong HOU ZhenYong BAI XianYong LI Chuan FANG Matthew ZHAO HaiSheng WANG JinCheng NING ZongJun Key Laboratory of Dark Matter and space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing210023China Yunnan Key Laboratory of the Solar Physics and space Science Kunming650216China school of earth and space sciences Peking UniversityBeijing100871China National Astronomical Observatories Chinese Academy of SciencesBeijing100101China school of Astronomy and space Science University of Chinese Academy of SciencesBeijing100049China school of Astronomy and space Science Nanjing UniversityNanjing210023China Key Laboratory of Modern Astronomy and Astrophysics Ministry of EducationNanjing UniversityNanjing210023China Columbus Academy GahannaOhio43230USA Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing100049China Yunnan Observatories Chinese Academy of SciencesKunming650216China

Kink oscillations,which are frequently observed in coronal loops and prominences,are often accompanied by extreme-ultraviolet(EUV)***,much more needs to be explored regarding the causal relationships between kink oscillations and EUV *** this article,we report the simultaneous detection of kink oscillations and EUV waves that are both associated with an X2.1 flare on 2023 March 03(SOL2023-03-03T17:39).The kink oscillations,which are almost perpendicular to the axes of loop-like structures,are observed in three coronal loops and one *** short loop shows in-phase oscillation within the same period of 5.2 min at three *** oscillation could be triggered by the pushing of an expanding loop and interpreted as the standing kink *** lags are found between the kink oscillations of the short loop and two long loops,suggesting that the kink wave travels in different *** kink oscillations of one long loop and the prominence are possibly driven by the disturbance of the coronal mass ejection(CME),and that of another long loop might be attributed to the interaction of the EUV *** onset time of the kink oscillation of the short loop is nearly same as the beginning of an EUV *** fact demonstrates that they are almost *** EUV wave is most likely excited by the expanding loop structure and shows two *** leading component is a fast coronal wave,and the trailing one could be due to the stretching magnetic field lines.

关键词： coronal loops solar flares solar prominence solar oscillations extreme-ultraviolet wave magnetohydrodynamic

Implementation of a particle-in-cell method for the energy solver in 3D spherical geodynamic modeling

在线全文

学校读者我要写书评

暂无评论

earth and Planetary Physics 2024年第3期8卷 549-563页

作者： Hao dong ZeBin Cao LiJun Liu YanChong Li SanZhong Li LiMing Dai XinYu Li Frontiers Science Center for Deep Ocean Multispheres and earth System Key Laboratory of Submarine Geosciences and Prospecting TechniquesMinistry of Education and College of Marine GeosciencesOcean University of ChinaQingdao 266100China State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Laboratory for Marine Geology Laoshan LaboratoryQingdao 266237China Department of earth Science&Environmental Change University of Illinois at Urbana-ChampaignUrbanaIL 61801USA Laboratory of Seismology and Physics of earth’s Interior School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China

The thermal evolution of the earth’s interior and its dynamic effects are the focus of earth ***,the commonly adopted grid-based temperature solver is usually prone to numerical oscillations,especially in the presence of sharp thermal gradients,such as when modeling subducting slabs and rising *** phenomenon prohibits the correct representation of thermal evolution and may cause incorrect implications of geodynamic *** examining several approaches for removing these numerical oscillations,we show that the Lagrangian method provides an ideal way to solve this *** this study,we propose a particle-in-cell method as a strategy for improving the solution to the energy equation and demonstrate its effectiveness in both one-dimensional and three-dimensional thermal problems,as well as in a global spherical simulation with data *** have implemented this method in the open-source finite-element code CitcomS,which features a spherical coordinate system,distributed memory parallel computing,and data assimilation algorithms.

关键词： numerical oscillation overshooting and undershooting particle-in-cell method three-dimensional spherical geodynamic modeling energy solver finite element method