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This paper evaluates a general, infinite family of clustering algorithms, called the Lance and Williams algorithms, with respect to the space-conserving criterion. An admissible clustering criterion is defined using the space conserving idea. Necessary and sufficient conditions for Lance and Williams clustering algorithms to satisfy space-conserving admissibility are provided. Space-dilating, space-contracting, and well-structured clustering algorithms are also discussed.The work of J. Van Ness was supported by NSF Grant #DMS 9201075. 相似文献
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Weedon MN Lettre G Freathy RM Lindgren CM Voight BF Perry JR Elliott KS Hackett R Guiducci C Shields B Zeggini E Lango H Lyssenko V Timpson NJ Burtt NP Rayner NW Saxena R Ardlie K Tobias JH Ness AR Ring SM Palmer CN Morris AD Peltonen L Salomaa V;Diabetes Genetics Initiative;Wellcome Trust Case Control Consortium Davey Smith G Groop LC Hattersley AT McCarthy MI Hirschhorn JN Frayling TM 《Nature genetics》2007,39(10):1245-1250
Human height is a classic, highly heritable quantitative trait. To begin to identify genetic variants influencing height, we examined genome-wide association data from 4,921 individuals. Common variants in the HMGA2 oncogene, exemplified by rs1042725, were associated with height (P = 4 x 10(-8)). HMGA2 is also a strong biological candidate for height, as rare, severe mutations in this gene alter body size in mice and humans, so we tested rs1042725 in additional samples. We confirmed the association in 19,064 adults from four further studies (P = 3 x 10(-11), overall P = 4 x 10(-16), including the genome-wide association data). We also observed the association in children (P = 1 x 10(-6), N = 6,827) and a tall/short case-control study (P = 4 x 10(-6), N = 3,207). We estimate that rs1042725 explains approximately 0.3% of population variation in height (approximately 0.4 cm increased adult height per C allele). There are few examples of common genetic variants reproducibly associated with human quantitativetraits; these results represent, to our knowledge, the first consistently replicated association with adult and childhood height. 相似文献
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A transition between the supersonic solar wind and the subsonic heliosheath was observed by Voyager 1, but the expected termination shock was not seen owing to a gap in the telemetry. Here we report observations of the magnetic field structure and dynamics of the termination shock, made by Voyager 2 on 31 August-1 September 2007 at a distance of 83.7 au from the Sun (1 au is the Earth-Sun distance). A single crossing of the shock was expected, with a boundary that was stable on a timescale of several days. But the data reveal a complex, rippled, quasi-perpendicular supercritical magnetohydrodynamic shock of moderate strength undergoing reformation on a scale of a few hours. The observed structure suggests the importance of ionized interstellar atoms ('pickup protons') at the shock. 相似文献
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