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101.
The character and OTU stability of classifications based on UPGMA clustering and maximum parsimony (MP) trees were compared
for 5 datasets (families of angiosperms, families of orthopteroid insects, species of the fish genusIctalurus, genera of the salamander family Salamandridae, and genera of the frog family Myobatrachidae). Stability was investigated
by taking different sized random subsamples of OTUs or characters, computing UPGMA clusters and an MP tree, and then comparing
the resulting trees with those based on the entire dataset. Agreement was measured by two consensus indices, that of Colless,
computed from strict consensus trees, and Stinebrickner's 0.5-consensus index.
Tests of character stability generally showed a monotone decrease in agreement with the standard as smaller sets of characters
are considered. The relative success of the two methods depended upon the dataset. Tests of OTU stability showed a monotone
decrease in agreement for UPGMA as smaller sets of OTUs are considered. But for MP, agreement decreased and then increased
again on the same scale. The apparent superiority of UPGMA relative to MP with respect to OTU stability depended upon the
dataset. Considerations other than stability, such as computer efficiency or accuracy, will also determine the method of choice
for classifications. 相似文献
102.
Sang-GeunKim 《潍坊学院学报》2004,4(4):5-8
This paper surveys important aspects of Web Intelligence (WI). WI explores the fundamental roles as well as practical impacts of Artificial Intelligence (AI) and advanced Information Technology (IT) on the next generation of Web - related products, systens, and activities. As a direction for scientific research and devlopment,WI can be extremely beneficial for the field of Artificial Intelligence in Education (AIED). This paper covers these issues only very briefly. It focuses more on other issues in WI, such as intelligent Web services, and semantic web, and proposes how to use them as basis for tackling new and challenging research problems in AIED. 相似文献
103.
Jong-Soon Kim 《北京联合大学学报(自然科学版)》2002,16(Z1):42-52
本文回顾了1997年经济危机后韩国政府采取的改革方案,并做出结论:与普遍的看法相反,韩国政府的大部分改革方案并不是基于新公共管理系统(NPM)的.NPM倡导的打破常规的概念是要把官僚主义者从政府内部的束缚中解放出来,然而韩国政府的改革目标却指向加强官僚政治的内部控制.另一个结论是:以NPM为导向的改革方案不适合韩国政府,因为韩国缺少成功实施NPM方案所应具备的先决条件,如基于规则的政府和充满活力的市场.本文强调了加强官僚政治外部控制机制的重要性.体制僵化、腐败、生产力低下这样的问题长期困扰韩国政府,这些问题不能通过采用NPM所建议的市场原则来解决.因此,本文的结论是:新统治理论是根除这些问题的更为行之有效的方法. 相似文献
104.
K. Oomagari H. Uchimura T. Matsumoto H. Yokoo M. Hirano J. S. Kim T. Nakahara 《Cellular and molecular life sciences : CMLS》1984,40(11):1288-1290
Summary Serotonin and 5-hydroxyindoleacetic acid (5-HIAA) were measured in individual nuclei of rat hypothalamus and other brain areas using HPLC with electrochemical detection. 5-HIAA levels were first demonstrated in hypothalamic and some discrete brain areas. The 5-HIAA/5-HT ratio was highest in the n. caudatus putamen, high in the n. ventromedialis and lowest in the n. suprachiasmaticus. 相似文献
105.
106.
J. L. Fauchère Kim Quang Do P. Y. C. Jow C. Hansch 《Cellular and molecular life sciences : CMLS》1980,36(10):1203-1204
Summary Lipophilic, steric, electronic, and enzyme resistance characteristics of carboranylalanine, adamantylalanine, neopentylglycine and tert-butylglycine are described. The first 2 amino-acids display lipophilicities 2 orders of magnitude higher than tryptophan.This work was supported by research grants to Prof. R. Schwyzer from the Swiss National Science Foundation. 相似文献
107.
108.
Jeon YH Heo YS Kim CM Hyun YL Lee TG Ro S Cho JM 《Cellular and molecular life sciences : CMLS》2005,62(11):1198-1220
Phosphodiesterases (PDEs) are essential regulators of cyclic nucleotide signaling with diverse physiological functions. Because of their great market potential and therapeutic importance, PDE inhibitors became recognized as important therapeutic agents in the treatment of various diseases. Currently, there are seven PDE inhibitors on the market, and the pharmacological and safety evaluations of many drug candidates are in progress. Three-dimensional (3D) structures of catalytic domains of PDE 1, -3, -4, -5 and -9 in the presence of their inhibitors are now available, and can be utilized for rational drug design. Recent advances in molecular pharmacology of PDE isoenzymes resulted in identification of new potential applications of PDE inhibitors in various therapeutic areas, including dementia, depression and schizophrenia. This review will describe the latest advances in PDE research on 3D structural studies, the potential of therapeutic applications and the development of drug candidates.Received 30 November 2004; received after revision 24 January 2005; accepted 5 February 2005 相似文献
109.
110.
During cell division, mitotic spindles are assembled by microtubule-based motor proteins. The bipolar organization of spindles is essential for proper segregation of chromosomes, and requires plus-end-directed homotetrameric motor proteins of the widely conserved kinesin-5 (BimC) family. Hypotheses for bipolar spindle formation include the 'push-pull mitotic muscle' model, in which kinesin-5 and opposing motor proteins act between overlapping microtubules. However, the precise roles of kinesin-5 during this process are unknown. Here we show that the vertebrate kinesin-5 Eg5 drives the sliding of microtubules depending on their relative orientation. We found in controlled in vitro assays that Eg5 has the remarkable capability of simultaneously moving at approximately 20 nm s(-1) towards the plus-ends of each of the two microtubules it crosslinks. For anti-parallel microtubules, this results in relative sliding at approximately 40 nm s(-1), comparable to spindle pole separation rates in vivo. Furthermore, we found that Eg5 can tether microtubule plus-ends, suggesting an additional microtubule-binding mode for Eg5. Our results demonstrate how members of the kinesin-5 family are likely to function in mitosis, pushing apart interpolar microtubules as well as recruiting microtubules into bundles that are subsequently polarized by relative sliding. 相似文献