5,366 research outputs found
Real hypersurfaces with isometric Reeb flow in complex quadrics
We classify real hypersurfaces with isometric Reeb flow in the complex
quadrics Q^m for m > 2. We show that m is even, say m = 2k, and any such
hypersurface is an open part of a tube around a k-dimensional complex
projective space CP^k which is embedded canonically in Q^{2k} as a totally
geodesic complex submanifold. As a consequence we get the non-existence of real
hypersurfaces with isometric Reeb flow in odd-dimensional complex quadrics.Comment: 14 page
Does Logarithm Transformation of Microarray Data Affect Ranking Order of Differentially Expressed Genes?
A common practice in microarray analysis is to transform the microarray raw
data (light intensity) by a logarithmic transformation, and the justification
for this transformation is to make the distribution more symmetric and
Gaussian-like. Since this transformation is not universally practiced in all
microarray analysis, we examined whether the discrepancy of this treatment of
raw data affect the "high level" analysis result. In particular, whether the
differentially expressed genes as obtained by -test, regularized t-test, or
logistic regression have altered rank orders due to presence or absence of the
transformation. We show that as much as 20%--40% of significant genes are
"discordant" (significant only in one form of the data and not in both),
depending on the test being used and the threshold value for claiming
significance. The t-test is more likely to be affected by logarithmic
transformation than logistic regression, and regularized -test more affected
than t-test. On the other hand, the very top ranking genes (e.g. up to top
20--50 genes, depending on the test) are not affected by the logarithmic
transformation.Comment: submitted to IEEE/EMBS Conference'0
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