1,721,475 research outputs found
THE PM221 INTERCONNECTION NETWORK
No full textThis work was supported in part by The Ohio State University Seed Grant 221630
DETECTION OF COMPOSITE SIGNALS .1. LOCALLY OPTIMUM DETECTOR TEST STATISTICS
No full textTest statistics of the locally optimum detection schemes for weak composite signals having both deterministic and stochastic signal components are derived for the purely-additive noise model. The locally optimum detectors are compared to those for deterministic-signal-only model and those for random-signal-only model. Structures of the locally optimum detectors are also described.Korea Science and Engineering Foundation (KOSEF) under Grant 893-0801-011-
PERFORMANCE ANALYSIS OF FHSS BFSK SYSTEMS WITH NONLINEAR DETECTORS IN SELECTIVE FADING IMPULSIVE NOISE ENVIRONMENT
No full textIn this paper, the noncoherent reception performance of frequency hopping spread spectrum communication systems operated in channels with impulsive noise and selective multipath fading characteristics is investigated. For the impulsive noise, the epsilon-contaminated mixture model is used. Binary frequency shift keying modulation and noncoherent demodulation are assumed and limiter-squarer detectors or squarers are used to detect signals. The bit error rates are obtained as functions of channel and system parameters, under the multihopping and multiuser synchronous multiple access case.Non-Directed Research Fund, Korea Research Foundation
C-60-mediated self-assembly of gold nanoparticles at the liquid/liquid interface
No full textC-60-mediated self-assembly of gold nanoparticles at the liquid/liquid interface in the form of a stable nanocomposite film is repoted. The metallic luster of the interfacial film results from the electronic coupling of Au nanoparticles, suggesting the formation of closely packed nanoparticle thin C films. The interfacial film of nanoparticles could be transferred to mica substrates and carbon-coated transmission electron microscopy (TEM) grids, and then studied by UV-vis, Raman spectroscopy and TEM. (c) 2005 Elsevier B.V. All rights reserved
Evaluation of the performance of clustering algorithms in kernel-induced feature space
No full textBy using a kernel function, data that are not easily separable in the original space can be clustered into homogeneous groups in the implicitly transformed high-dimensional feature space. Kernel k-means algorithms have recently been shown to perform better than conventional k-means algorithms in unsupervised classification. However. few reports have examined the benefits of using a kernel function and the relative merits of the various kernel clustering algorithms with regard to the data distribution. In this study, we reformulated four representative clustering algorithms based on a kernel function and evaluated their performances for various data sets. The results indicate that each kernel clustering algorithm gives markedly better performance than its conventional counterpart for almost all data sets. Of the kernel clustering algorithms studied in the present work, the kernel average linkage algorithm gives the most accurate clustering results. (C) 2004 Pattern Recognition Society. Published by Elsevier Ltd. All rights reserved.This work was supported by the Korean Systems Biology Research Grant (M1-0309-02-0002) from the Ministry of Science and Technology. We would like to thank Chung
Moon Soul Center for BioInformation and BioElectronics and the IBM SUR program for providing research and computing facilities
Degradation of pyridine by Nocardioides sp. strain OS4 isolated from the oxic zone of a spent shale column
No full textA pyridine-degrading bacterial strain was isolated from the oxic zone of a spent share column. The microorganism was an aerobic and pleomorphic coryneform bacterium with LL-diaminopimelic acid in the cell wall. On the basis of its phylogenetic and chemotaxonomic characteristics, the strain was identified as Nocardioides sp. strain OS4. The pyridine was completely degraded and the growth yield was 0.30 g cell/g pyridine. Strain OS4 metabolized pyridine in an inducible manner and released a pigment that has maximum absorbance at 400 nm during the pyridine degradation. This strain also degraded some compounds of the basic fraction of retort water and various other aromatic compounds
Characterization of an endoxylanase produced by an isolated strain of Bacillus sp
No full textMicroorganisms producing xylanase were screened for the enzymatic production of xylo-oligosaccharides from xylan. One of the bacteria isolated fi om compost produced an endoxylanase extracellularly. The bacterium was identified as Bacillus sp. according to its taxonomic characteristics examined. Xylanase production reached upto 5 U/ml after 22 h of culture in LB medium at 30 degrees C. The xylanase was purified by ammonium sulfate precipitation and gel filtration. The molecular weight of the xylanase was estimated to be 20,400 by SDS-PAGE. Optimal temperature and pH for the xylanase activity was 60 degrees C and 6.5, respectively. The enzyme was stable at temperatures upto 40 degrees C and pH values from 4 to 10. The xylanase was completely inhibited by the addition of 2 mM mercury ion. Apparent K-m and V-max values for oat spelt xylan were 9.2 mg/ml and 1954 U/mg protein, respectively. For birchwood xylan, the values were 6.3 mg/ml and 1009 U/mg protein, The predominant products of the xylan hydrolysis were xylobiose, xylotriose and xylotetraose, indicating that the enzyme is an endoxylanase. Upto 85% of the initially added enzyme (2 U/ml) was bound to 50 mg/ml of the insoluble fraction of oat spelt xylan after incubation at 30 degrees C for 30 min
Self-assembled silver nanoprisms monolayers at the liquid/liquid interface
No full textA crown ether derivative (4'-aminobenzo-15-crown-5 hydrotetrafluoroborate) can mediate the self-assembly of silver nanoprisms at the liquid/liquid interface in the form of a stable hybrid nanocomposite film. The metallic luster of the interfacial film results from the electronic coupling of Ag nanoprisms, suggesting the formation of closely packed nanoprism thin films. The interfacial film of nanoprisms could be transferred to solid substrates as a Langmuir-Blodgett film. The properties of films were studied by UV-vis spectroscopy and transmission electron microscopy. (c) 2005 Elsevier B.V. All rights reserved
Towards clustering of incomplete microarray data without the use of imputation
No full textMotivation: Clustering technique is used to find groups of genes that show similar expression patterns under multiple experimental conditions. Nonetheless, the results obtained by cluster analysis are influenced by the existence of missing values that commonly arise in microarray experiments. Because a clustering method requires a complete data matrix as an input, previous studies have estimated the missing values using an imputation method in the preprocessing step of clustering. However, a common limitation of these conventional approaches is that once the estimates of missing values are fixed in the preprocessing step, they are not changed during subsequent processes of clustering; badly estimated missing values obtained in data preprocessing are likely to deteriorate the quality and reliability of clustering results. Thus, a new clustering method is required for improving missing values during iterative clustering process. Results: We present a method for Clustering Incomplete data using Alternating Optimization (CIAO) in which a prior imputation method is not required. To reduce the influence of imputation in preprocessing, we take an alternative optimization approach to find better estimates during iterative clustering process. This method improves the estimates of missing values by exploiting the cluster information such as cluster centroids and all available non-missing values in each iteration. To test the performance of the CIAO, we applied the CIAO and conventional imputation-based clustering methods, e.g. k-means based on KNNimpute, for clustering two yeast incomplete data sets, and compared the clustering result of each method using the Saccharomyces Genome Database annotations. The clustering results of the CIAO method are more significantly relevant to the biological gene annotations than those of other methods, indicating its effectiveness and potential for clustering incomplete gene expression data
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