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101.
QU Yuangao XIE Guwei & GONG Yiming . Faculty of Earth Sciences China University of Geosciences Wuhan China . Nanjing Institute of Geology Paleontology Chinese Academy of Sciences Nanjing China 《科学通报(英文版)》2004,49(21):2288-2295
Stromatolitesareusuallyinterpretedastheorgano-sedimentarystructurescausedbythegrowthandmetabo-lismofmicro-organisms,principallycyanobacteriaandprecipitatedmineralgrainstrappedtothestickylay-ers[1—5].Asthesunlightisstrongindaytime,thealgaefila-mentsshowstrongactivityinphotosynthesisandgrowtowardsunlight.Ontheotherhand,asthesunlightisweakatnight,thealgaefilamentsshowinactivityinphotosyn-thesisandgrowhorizontally.Duringthecourseofgrowth,thealgaewillproducesomeglutinoussecretionwhichcancatchsedim… 相似文献
102.
Despite a long history of research on the Early Cambrian in China most available data on small skeletal fossils concern fossil associations of the shallow carbonate platform. Information on skeletal fossils from marginal shelf environments of the Yangtze Platform is scanty, which may reflect the rarity of fossils in deeper sedimentary environments but is also due to limitation of carbonate distribution and outcrops, difficulties in fossil extraction, and a general research focus on the Precambrian-Cambrian boundary beds on the carbonate platform. Here we present a documentation of Meishucunian to Qiongzhusian small skeletal fossils from the lower Hetang Formation and the chert unit at its base from the Jiangshan region, Zhejiang Province, representing a relatively deep shelf environment compared to the inner shelf region. The earliest association (Meishucunian) from the chert unit underlying the Hetang Formation is mainly characterized by the occurrence of Protohertzina anabarica, P. unguliformis, Fengzuella zhejiangensis, and Kaiyangites novilis, which differs somewhat in composition from SSF-associations of typical inner shelf deposits. The enigmatic skeletal fossil Fengzuella zhejiangensis, which exhibits an unusual secretional growth mode previously unrecognized from the Early Cambrian, is described in detail. A younger (Qiongzhusian) fossil association contains numerous arthropod remains, such as disarticulated spines of arthropods (Jiangshanodus- and Kijacus-type), which have previously been considered as conodont-like fossils, and bradoriid valves. 相似文献
103.
西藏措勤地区典中组火山岩地球化学特征及构造背景 总被引:6,自引:0,他引:6
措勤盆地位于西藏冈底斯构造-岩浆岩带的西段北侧,该区古新世火山活动十分强烈,形成了一套厚度大于1 000 m的中酸性火山岩地层,火山岩K-Ar和Rb-Sr同位素年龄为63.9~61.0 Ma,区域上可与古近纪林子宗群下部层位相对比,归为古新统典中组.火山岩岩石化学、地球化学特征分析表明,该火山岩系属高钾钙碱性-钙碱性系列,轻稀土富集,负Eu异常明显.与原始地幔相比,微量元素Rb,Ba,K,Th,U富集;Ti,P,Sr,Ta(Nb)亏损.锶、氧同位素组成显示岩浆来源与陆壳物质关系密切,推测是来自于俯冲带的幔源基性岩浆与陆壳重熔酸性岩浆以不同比例混合所形成.综合研究认为,这套火山岩形成于陆缘弧构造环境,与喜马拉雅特提斯洋壳向北俯冲消减作用有关. 相似文献
104.
A.P. Farkas 《Surface science》2007,601(1):193-200
The adsorption, desorption and dissociation of ethanol have been investigated by work function, thermal desorption (TPD) and high resolution electron energy loss (HREELS) spectroscopic measurements on Mo2C/Mo(1 0 0). Adsorption of ethanol on this sample at 100 K led to a work function decrease suggesting that the adsorbed layer has a positive outward dipole moment By means of TPD we distinguished three adsorption states, condensed layer with a Tp = 162 K, chemisorbed ethanol with Tp = 346 K and irreversibly bonded species which decomposes to different compounds. These are hydrogen, acetaldehyde, methane, ethylene and CO. From the comparison of the Tp values with those obtained following their adsorption on Mo2C it was inferred that the desorption of methane and ethylene is reaction limited, while that of hydrogen is desorption limited process. HREEL spectra obtained at 100 K indicated that at lower exposure ethanol undergoes dissociation to give ethoxy species, whereas at high exposure molecularly adsorbed ethanol also exists on the surface. Analysis of the spectral changes in HREELS observed for annealed surface assisted to ascertain the reaction pathways of the decomposition of adsorbed ethanol. 相似文献
105.
Dunxi Yu Minghou Xu Hong Yao Jiancai Sui Xiaowei Liu Yun Yu Qian Cao 《Proceedings of the Combustion Institute》2007,31(2):1921-1928
The chemical composition of particles generated during pulverized coal combustion is the consequence of their formation processes. This work aims to use the size resolved elemental composition of coal-derived particles to identify their formation modes. A size-classified bituminous coal is burnt in a laboratory drop tube furnace at 1150, 1250, and 1350 °C, respectively. The elemental composition of the size-segregated particles from coal combustion is analyzed and the total mass fraction size distributions of Si and Al are obtained. Three particle formation modes are observed in these distribution profiles. The coarse mode has the highest value of the total mass fraction of Si and Al while the ultrafine mode has the lowest one. The total mass fraction of Si and Al in these two modes is nearly independent of particle size. It is believed that the coarse mode is formed by the mineral coalescence mechanism and the ultrafine mode by the vaporization–condensation mechanism. The difference in the total mass fraction of Si and Al between the central mode and the other two indicates that the central mode is formed by different mechanisms. Based on the observation that the total mass fraction of Si and Al in this mode increases with increasing particle size, heterogeneous condensation of vaporized species on existing fine residual ash particles is proposed to account for the formation of these particles. The study of the elemental composition of the three modes represented in five categories verifies the proposed formation mechanisms for them to some extent. 相似文献
106.
New fossil elaterid (Coleoptera: Polyphaga: Elateridae) from Yixian Formation of western Liaoning, China 总被引:4,自引:0,他引:4
A new species of the elaterid genus Cryptocoelus Dolin and Nel, 2002 from the Late Jurassic to Early Cretaceous Yixian Formation in the western Liaoning, China is described. Diagnosis of the genus is revised, and the systematic position of the genus is briefly discussed. Because the elaterids originated in the Early to Mid-Jurassic, this new material from the Late Jurassic-Early Cretaceous will enhance our understanding of the transition between ancient elaterids and extant ones, bridge the gap of cryptic relationships between the Mesozoic cupedids and elaterids, and expand our knowledge of their evolutionary history. 相似文献
107.
中和沉淀法Fe_3O_4的生成过程研究 总被引:4,自引:0,他引:4
本文利用XRD等技术对中和沉淀法Fe3O4的生成条件进行了研究,得到了Fe3O4的生成条件图。并以此对中和沉淀法Fe3O4的生成过程进行了讨论,发现Fe3O4的生成过程和空气氧化法Fe3O4的生成过程截然不同。中和沉淀法Fe3O4的生成过程随R及反应PH的不同而不同。反应温度的提高有利于Fe3O4生成量的增加并使Fe3O4的生成条件区域扩大。 相似文献
108.
109.
Heinz Falk Helmut Marko Norbert Müller Wolfgang Schmitzberger Hugo Stumpe 《Monatshefte für Chemie / Chemical Monthly》1990,121(11):893-901
Summary Apomyoglobin was reconstituted with bile pigments of the verdinoid, 2,3-dihydroverdinoid, pterobilinoid, and violinoid type. Absorption and circular dichroism data as well as formation constants of the complexes were measured. From these results it was concluded that chromophore binding and induced chirality of these pigments are mainly governed by a lipophilic region opposite to the propionic side chain(s) and the asymmetric position of the hydrogen bonding acceptors of the propionic acid side chain(s) at the entrance of the protein pocket.Dedicated to Prof. Dr. A. Eschenmoser on occasion of his 65th birthday 相似文献
110.
Chao Wang Yongchao Lu Hongguang Huang Fengcun Xing Lei Chen Xuebin Du Zhanhong Liu Wenjun Zhang 《地球科学学刊》2015,(3)
The large reef complexes of the Upper Permian Changxing Formation, with a significant breakthrough for petroleum exploration, are an important target for petroleum exploration in the Yu-anba area of th... 相似文献