13,650 research outputs found
Some Hopf Algebras of Trees
This paper generalizes the operadic construction of the Connes-Kreimer Hopf
algebra of rooted trees by Moerdijk. Examples of Hopf algebras obtained in this
way include the Loday-Ronco Hopf algebra of planar binary trees and the
Brouder-Frabetti pruning Hopf algebra. In some examples we obtain a natural
pre-Lie or dendriform algebra structure on the dual Hopf algebra. v2: Proof in
section 8 corrected. v3: more corrections.Comment: 24 pages, 3 figure
Commuting in multinodal urban systems: An empirical comparison of three alternative models
The paper analyses whether the basic monocentric model of urban structure and commuting explains actual commuting in Europe, i.e. the Netherlands. As in the United States much wasteful commuting is established. The basic model has a low degree of explanatory power. In order to get more in line with actual commuting, the paper elaborates two alternatives to the basic model. Besides a decon-centrated model, a cross-traffic model is developed. Particularly the latter is quite successful in explaining actual commuting. The paper pleads for endo-geni-zing employment and stresses heterogeneity in labour demand and supply.
Multiple tests of association with biological annotation metadata
We propose a general and formal statistical framework for multiple tests of
association between known fixed features of a genome and unknown parameters of
the distribution of variable features of this genome in a population of
interest. The known gene-annotation profiles, corresponding to the fixed
features of the genome, may concern Gene Ontology (GO) annotation, pathway
membership, regulation by particular transcription factors, nucleotide
sequences, or protein sequences. The unknown gene-parameter profiles,
corresponding to the variable features of the genome, may be, for example,
regression coefficients relating possibly censored biological and clinical
outcomes to genome-wide transcript levels, DNA copy numbers, and other
covariates. A generic question of great interest in current genomic research
regards the detection of associations between biological annotation metadata
and genome-wide expression measures. This biological question may be translated
as the test of multiple hypotheses concerning association measures between
gene-annotation profiles and gene-parameter profiles. A general and rigorous
formulation of the statistical inference question allows us to apply the
multiple hypothesis testing methodology developed in [Multiple Testing
Procedures with Applications to Genomics (2008) Springer, New York] and related
articles, to control a broad class of Type I error rates, defined as
generalized tail probabilities and expected values for arbitrary functions of
the numbers of Type I errors and rejected hypotheses. The resampling-based
single-step and stepwise multiple testing procedures of [Multiple Testing
Procedures with Applications to Genomics (2008) Springer, New York] take into
account the joint distribution of the test statistics and provide Type I error
control in testing problems involving general data generating distributions
(with arbitrary dependence structures among variables), null hypotheses, and
test statistics.Comment: Published in at http://dx.doi.org/10.1214/193940307000000446 the IMS
Collections (http://www.imstat.org/publications/imscollections.htm) by the
Institute of Mathematical Statistics (http://www.imstat.org
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