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101.
Late Cenozoic terrestrial fossil records of North America are biased by a predominance of mid-latitude deposits, mostly in the western half of the continent. Consequently, the biological history of eastern North America, including the eastern deciduous forest, remains largely hidden. Unfortunately, vertebrate fossil sites from this vast region are rare, and few pertain to the critically important late Tertiary period, during which intensified global climatic changes took place. Moreover, strong phylogenetic affinities between the flora of eastern North America and eastern Asia clearly demonstrate formerly contiguous connections, but disparity among shared genera (eastern Asia-eastern North America disjunction) implies significant periods of separation since at least the Miocene epoch. Lacustrine sediments deposited within a former sinkhole in the southern Appalachian Mountains provide a rare example of a late Miocene to early Pliocene terrestrial biota from a forested ecosystem. Here we show that the vertebrate remains contained within this deposit represent a unique combination of North American and Eurasian taxa. A new genus and species of the red (lesser) panda (Pristinailurus bristoli), the earliest and most primitive so far known, was recovered. Also among the fauna are a new species of Eurasian badger (Arctomeles dimolodontus) and the largest concentration of fossil tapirs ever recorded. Cladistical analyses of the two new carnivores strongly suggest immigration events that were earlier than and distinct from previous records, and that the close faunal affinities between eastern North America and eastern Asia in the late Tertiary period are consistent with the contemporaneous botanical record. 相似文献
102.
TNF-RII and c-IAP1 mediate ubiquitination and degradation of TRAF2 总被引:18,自引:0,他引:18
Tumour necrosis factor-alpha (TNF-alpha) is a proinflammatory mediator that exerts its biological functions by binding two TNF receptors (TNF-RI and TNF-RII), which initiate biological responses by interacting with adaptor and signalling proteins. Among the signalling components that associate with TNF receptors are members of the TNF-R-associated factor (TRAF) family. TRAF2 is required for TNF-alpha-mediated activation of c-Jun N-terminal kinase (JNK), contributes to activation of NF-kappaB, and mediates anti-apoptotic signals,. TNF-RI and TNF-RII signalling complexes also contain the anti-apoptotic ('inhibitor of apoptosis') molecules c-IAP1 and c-IAP2 (refs 5, 6), which also have RING domain-dependent ubiquitin protein ligase (E3) activity. The function of IAPs in TNF-R signalling is unknown. Here we show that binding of TNF-alpha to TNF-RII induces ubiquitination and proteasomal degradation of TRAF2. Although c-IAP1 bound TRAF2 and TRAF1 in vitro, it ubiquitinated only TRAF2. Expression of wild-type c-IAP1, but not an E3-defective mutant, resulted in TRAF2 ubiquitination and degradation. Moreover, E3-defective c-IAP1 prevented TNF-alpha-induced TRAF2 degradation and inhibited apoptosis. These findings identify a physiologic role for c-IAP1 and define a mechanism by which TNF-RII-regulated ubiquitin protein ligase activity can potentiate TNF-induced apoptosis. 相似文献
103.
HUANG Xiaochun ZHANG Jiepeng & CHEN Xiaoming . School of Chemistry Chemical Engineering Sun Yat-Sen Uiniversity Guangzhou China . Department of Chemistry Shantou University Shantou China Correspondence should be addressed to Chen Xiaoming 《科学通报(英文版)》2003,48(15):1531-1534
Considerable efforts have been focused on the crystal engineering of the supramolecular architectures with desired properties such as zeolitic, magnetic and electric conducting materials[1—3]. But crystal engineering is still a great challenge to the chemists since lack of control over the coordination modes of metal centers and ligands during assembly of extended structures[4]. Some successful synthetic strategies based on topologic control of building blocks have been developed especially i… 相似文献
104.
Thermodynamic evolution of lithosphere of the North China craton: Records from lower crust and upper mantle xenoliths from Hannuoba 总被引:1,自引:0,他引:1
LIU Yongsheng * GAO Shan LIU Xiaoming CHEN Xiaoming ZHANG Wenlan & WANG Xuance . Faculty of Earth Sciences China University of Geosciences Wuhan China . The State Key Lab for Mineral Deposits Research Department of Earth Sciences Nanjing University Nanjing China . Key Laboratory of Continental Dynamics Department of Geology Northwest University Xi抋n China Correspondence should be addressed to Liu Yongsheng 《科学通报(英文版)》2003,48(21):2371-2377
Lithospheric thinning in East China attracts much attention of geologists. In many cases where a lithospheric thinning is inferred, the trigger for instability is a preced-ing episode of crustal thickening by the continental colli-sion[1]. Lithospheric processes (e.g. lithospheric thinning) could be recorded by the thermal history of the lower crustal and upper mantle xenoliths. Xu et al.[2] suggested that the cooling (from >1200 to 850℃) recorded by spinel harzburgite from Northeast China … 相似文献
105.
孤独症儿童治疗方法概况 总被引:3,自引:0,他引:3
刘晓明 《北京教育学院学报(自然科学版)》2007,2(2):15-18
自1943年以来,经过半个多世纪的时间,关于孤独症的理论与治疗技术日趋成熟。本文对一些主要治疗方法与技术进行了简要回顾,着重介绍了近年来在美国有广泛应用的RDI疗法。针对我国孤独症教育治疗不足的现状对治疗过程中的问题进行了一定归纳。 相似文献
106.
内配煤团块直接还原法制备铁粒技术研究 总被引:6,自引:0,他引:6
根据我国现阶段直接还原状况及国内能源的结构特点,提出利用舍碳团块直接还原制备铁颗粒的技术思想;通过调整团矿的内配碳比、温度、碱度及添加剂配入量来优化渣铁的分离和提高铁粒质量,找到最佳的配比方案。铁的收得率达到90%以上,铁粒中wFe〉96%,ws=0.02%~0.05%,wc〈4.0%;分离出的铁粒可直接作为电炉炼钢的优质原料。 相似文献
107.
支持向量机在电力变压器故障诊断中的应用 总被引:6,自引:1,他引:6
利用支持向量机的学习方法,构建了电力变压器故障诊断模型.该模型将变压器故障分为放电性和过热性两大类,通过统计分析寻求特征量区分类间的故障类型,采用支持向量机识别类内的故障类型,利用基于交叉验证的网格搜索法来确定支持向量机的参数.考虑到变压器油中溶解气体特征空间的紧致性原理,利用模糊C均值聚类算法对所获取的样本进行预选取,有效地解决了确定模型参数时耗时巨大的问题,并一定程度提高了模型的推广能力.实例验证表明,该模型在有限样本情况下,能达到较高的变压器故障判断率,放电性故障样本正确判断率为90.5%,过热性故障样本正确判断率为85.9%,说明该模型具有很好的分类效果和推广能力. 相似文献
108.
对目前带钢横向温度分布的研究方法和结论进行了分析;对1800热连轧机精轧出口带钢的横向温度进行测量,针对典型的分布规律,提出了描述参数,并用该参数就其分布规律以及分布与带钢宽度、纵向温度的关系进行了讨论,为建立热连轧带钢横向温度控制模型提供了依据. 相似文献
109.
110.