2,774 research outputs found
Phase transitions related to the pigeonhole principle
Since Paris introduced them in the late seventies (Paris1978), densities turned out to be useful for studying independence results. Motivated by their simplicity and surprising strength we investigate the combinatorial complexity of two such densities which are strongly related to the pigeonhole principle. The aim is to miniaturise Ramsey's Theorem for -tuples. The first principle uses an unlimited amount of colours, whereas the second has a fixed number of two colours. We show that these principles give rise to Ackermannian growth. After parameterising these statements with respect to a function f:N->N, we investigate for which functions f Ackermannian growth is still preserved
The microscopic nature of localization in the quantum Hall effect
The quantum Hall effect arises from the interplay between localized and
extended states that form when electrons, confined to two dimensions, are
subject to a perpendicular magnetic field. The effect involves exact
quantization of all the electronic transport properties due to particle
localization. In the conventional theory of the quantum Hall effect,
strong-field localization is associated with a single-particle drift motion of
electrons along contours of constant disorder potential. Transport experiments
that probe the extended states in the transition regions between quantum Hall
phases have been used to test both the theory and its implications for quantum
Hall phase transitions. Although several experiments on highly disordered
samples have affirmed the validity of the single-particle picture, other
experiments and some recent theories have found deviations from the predicted
universal behaviour. Here we use a scanning single-electron transistor to probe
the individual localized states, which we find to be strikingly different from
the predictions of single-particle theory. The states are mainly determined by
Coulomb interactions, and appear only when quantization of kinetic energy
limits the screening ability of electrons. We conclude that the quantum Hall
effect has a greater diversity of regimes and phase transitions than predicted
by the single-particle framework. Our experiments suggest a unified picture of
localization in which the single-particle model is valid only in the limit of
strong disorder
Epidemiological evidence for the association between red and processed meat intake and colorectal cancer
A perspective paper was synthesized during the workshop “How can we approach consensus on the healthiness of red meat?” held in Oslo, Norway, in November 2013 (Oostindjer et al., 2014). The resultant article contains some very interesting information and focuses on the role of red and processed meat in colorectal cancer development. However, not all comments from the co-authors were taken into account in the final manuscript, resulting in a scientifically incorrect statement in the abstract: “Epidemiological and mechanistic data on associations between red and processed meat intake and CRC are inconsistent…”. Because of the high visibility of this abstract through many websites and journals we have to strongly object to that statement
Hydrogeologische studie van de ondiepe waterwinning van Inex NV te Bavegem (Sint-Lievens-Houtem)
MarkerMiner 1.0: a new application for phylogenetic marker development using angiosperm transcriptomes
Premise of the study: Targeted sequencing using next-generation sequencing (NGS) platforms offers enormous potential for plant systematics by enabling economical acquisition of multilocus data sets that can resolve difficult phylogenetic problems. However, because discovery of single-copy nuclear (SCN) loci from NGS data requires both bioinformatics skills and access to high-performance computing resources, the application of NGS data has been limited.
Methods and Results: We developed MarkerMiner 1.0, a fully automated, open-access bioinformatic workflow and application for discovery of SCN loci in angiosperms. Our new tool identified as many as 1993 SCN loci from transcriptomic data sampled as part of four independent test cases representing marker development projects at different phylogenetic scales.
Conclusions: MarkerMiner is an easy-to-use and effective tool for discovery of putative SCN loci. It can be run locally or via the Web, and its tabular and alignment outputs facilitate efficient downstream assessments of phylogenetic utility, locus selection, intron-exon boundary prediction, and primer or probe development
WZW-like Action for Heterotic String Field Theory
We complete the construction of the Neveu-Schwarz sector of heterotic string
field theory begun in hep-th/0406212 by giving a closed-form expression for the
action and gauge transformations. Just as the Wess-Zumino-Witten (WZW) action
for open superstring field theory can be constructed from pure-gauge fields in
bosonic open string field theory, our heterotic string field theory action is
constructed from pure-gauge fields in bosonic closed string field theory. The
construction involves a simple alternative form of the WZW action which is
consistent with the algebraic structures of closed string field theory.Comment: 22 pages, no figures, LaTeX2
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