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981.
El Moussaoui A Nijs M Paul C Wintjens R Vincentelli J Azarkan M Looze Y 《Cellular and molecular life sciences : CMLS》2001,58(4):556-570
In the tropical species Carica papaya, the articulated and anastomosing laticifers form a dense network of vessels displayed in all aerial parts of the plant. Damaging the papaya tree inevitably severs its laticifers, eliciting an abrupt release of latex. Besides the well-known cysteine proteinases, papain, chymopapain, caricain and glycyl endopeptidase, papaya latex is also a rich source of other enzymes. Together, these enzymes could provide an important contribution to plant defence mechanisms by sanitising and sealing the wounded areas on the tree. 相似文献
982.
K-modes Clustering 总被引:2,自引:0,他引:2
0 norm (defined as the limit of an Lp norm as p approaches zero).
In Monte Carlo simulations, both K-modes and the latent class procedures (e.g., Goodman 1974) performed with equal efficiency
in recovering a known underlying cluster structure. However, K-modes is an order of magnitude faster than the latent class
procedure in speed and suffers from fewer problems of local optima than do the latent class procedures. For data sets involving
a large number of categorical variables, latent class procedures become computationally extremly slow and hence infeasible.
We conjecture that, although in some cases latent class procedures might perform better than K-modes, it could out-perform
latent class procedures in other cases. Hence, we recommend that these two approaches be used as "complementary" procedures
in performing cluster analysis. We also present an empirical comparison of K-modes and latent class, where the former method
prevails. 相似文献
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Sequencing of a rice centromere uncovers active genes 总被引:24,自引:0,他引:24
Nagaki K Cheng Z Ouyang S Talbert PB Kim M Jones KM Henikoff S Buell CR Jiang J 《Nature genetics》2004,36(2):138-145
Centromeres are the last frontiers of complex eukaryotic genomes, consisting of highly repetitive sequences that resist mapping, cloning and sequencing. The centromere of rice Chromosome 8 (Cen8) has an unusually low abundance of highly repetitive satellite DNA, which allowed us to determine its sequence. A region of approximately 750 kb in Cen8 binds rice CENH3, the centromere-specific H3 histone. CENH3 binding is contained within a larger region that has abundant dimethylation of histone H3 at Lys9 (H3-Lys9), consistent with Cen8 being embedded in heterochromatin. Fourteen predicted and at least four active genes are interspersed in Cen8, along with CENH3 binding sites. The retrotransposons located in and outside of the CENH3 binding domain have similar ages and structural dynamics. These results suggest that Cen8 may represent an intermediate stage in the evolution of centromeres from genic regions, as in human neocentromeres, to fully mature centromeres that accumulate megabases of homogeneous satellite arrays. 相似文献
987.
Moreira MC Klur S Watanabe M Németh AH Le Ber I Moniz JC Tranchant C Aubourg P Tazir M Schöls L Pandolfo M Schulz JB Pouget J Calvas P Shizuka-Ikeda M Shoji M Tanaka M Izatt L Shaw CE M'Zahem A Dunne E Bomont P Benhassine T Bouslam N Stevanin G Brice A Guimarães J Mendonça P Barbot C Coutinho P Sequeiros J Dürr A Warter JM Koenig M 《Nature genetics》2004,36(3):225-227
Ataxia-ocular apraxia 2 (AOA2) was recently identified as a new autosomal recessive ataxia. We have now identified causative mutations in 15 families, which allows us to clinically define this entity by onset between 10 and 22 years, cerebellar atrophy, axonal sensorimotor neuropathy, oculomotor apraxia and elevated alpha-fetoprotein (AFP). Ten of the fifteen mutations cause premature termination of a large DEAxQ-box helicase, the human ortholog of yeast Sen1p, involved in RNA maturation and termination. 相似文献
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