6,161 research outputs found
Tightness is preserved by Legendrian surgery
This paper describes a characterization of tightness of closed contact
3-manifolds in terms of supporting open book decompositions. The main result is
that tightness of a closed contact 3-manifold is preserved under Legendrian
surgery.Comment: version accepted by Annals of Mathematic
Mapping class group relations, Stein fillings, and planar open book decompositions
The aim of this paper is to use mapping class group relations to approach the
`geography' problem for Stein fillings of a contact 3-manifold. In particular,
we adapt a formula of Endo and Nagami so as to calculate the signature of such
fillings as a sum of the signatures of basic relations in the monodromy of a
related open book decomposition. We combine this with a theorem of Wendl to
show that for any Stein filling of a contact structure supported by a planar
open book decomposition, the sum of the signature and Euler characteristic
depends only on the contact manifold. This gives a simple obstruction to
planarity, which we interpret in terms of existence of certain configurations
of curves in a factorization of the monodromy. We use these techniques to
demonstrate examples of non-planar structures which cannot be shown non-planar
by previously existing methods.Comment: Final version, includes minor stylistic revisions suggested by
referee. Accepted for publication by the Journal of Topolog
Ontology-driven conceptual modeling: A'systematic literature mapping and review
All rights reserved. Ontology-driven conceptual modeling (ODCM) is still a relatively new research domain in the field of information systems and there is still much discussion on how the research in ODCM should be performed and what the focus of this research should be. Therefore, this article aims to critically survey the existing literature in order to assess the kind of research that has been performed over the years, analyze the nature of the research contributions and establish its current state of the art by positioning, evaluating and interpreting relevant research to date that is related to ODCM. To understand and identify any gaps and research opportunities, our literature study is composed of both a systematic mapping study and a systematic review study. The mapping study aims at structuring and classifying the area that is being investigated in order to give a general overview of the research that has been performed in the field. A review study on the other hand is a more thorough and rigorous inquiry and provides recommendations based on the strength of the found evidence. Our results indicate that there are several research gaps that should be addressed and we further composed several research opportunities that are possible areas for future research
The Inverse G-Wishart Distribution and Variational Message Passing
Message passing on a factor graph is a powerful paradigm for the coding of
approximate inference algorithms for arbitrarily graphical large models. The
notion of a factor graph fragment allows for compartmentalization of algebra
and computer code. We show that the Inverse G-Wishart family of distributions
enables fundamental variational message passing factor graph fragments to be
expressed elegantly and succinctly. Such fragments arise in models for which
approximate inference concerning covariance matrix or variance parameters is
made, and are ubiquitous in contemporary statistics and machine learning
Partial alignment and measurement of residual dipolar couplings of proteins under high hydrostatic pressure
High-pressure NMR spectroscopy has emerged as a complementary approach for investigating
various structural and thermodynamic properties of macromolecules. Noticeably absent from the
array of experimental restraints that have been employed to characterize protein structures at high
hydrostatic pressure is the residual dipolar coupling, which requires the partial alignment of the
macromolecule of interest. Here we examine five alignment media that are commonly used at
ambient pressure for this purpose. We find that the spontaneous alignment of Pf1 phage, d(GpG)
and a C12E5/n-hexnanol mixture in a magnetic field is preserved under high hydrostatic pressure.
However, DMPC/ DHPC bicelles and collagen gel are found to be unsuitable. Evidence is
presented to demonstrate that pressure-induced structural changes can be identified using the
residual dipolar coupling
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