560 research outputs found
Bredon cohomology and robot motion planning
In this paper we study the topological invariant reflecting
the complexity of algorithms for autonomous robot motion. Here, stands for
the configuration space of a system and is, roughly, the
minimal number of continuous rules which are needed to construct a motion
planning algorithm in . We focus on the case when the space is
aspherical; then the number depends only on the fundamental group
and we denote it . We prove that
can be characterised as the smallest integer such that the canonical
-equivariant map of classifying spaces can be equivariantly deformed into the
-dimensional skeleton of . The symbol
denotes the classifying space for free actions and
denotes the classifying space for actions with
isotropy in a certain family of subgroups of . Using
this result we show how one can estimate in terms of the
equivariant Bredon cohomology theory. We prove that where denotes the cohomological dimension of with
respect to the family of subgroups . We also introduce a Bredon
cohomology refinement of the canonical class and prove its universality.
Finally we show that for a large class of principal groups (which includes all
torsion free hyperbolic groups as well as all torsion free nilpotent groups)
the essential cohomology classes in the sense of Farber and Mescher are exactly
the classes having Bredon cohomology extensions with respect to the family
.Comment: This revision contains a few additional comments, among them is
Corollary 3.5.
Genetic and epigenetic regulation of abdominal aortic aneurysms
Abdominal aortic aneurysms (AAAs) are focal dilations of the aorta that develop from degenerative changes in the media and adventitia of the vessel. Ruptured AAAs have a mortality of up to 85%, thus it is important to identify patients with AAA at increased risk for rupture who would benefit from increased surveillance and/or surgical repair. Although the exact genetic and epigenetic mechanisms regulating AAA formation are not completely understood, Mendelian cases of AAA, which result from pathologic variants in a single gene, have helped provide a basic understanding of AAA pathophysiology. More recently, genome wide associated studies (GWAS) have identified additional variants, termed single nucleotide polymorphisms, in humans that may be associated with AAAs. While some variants may be associated with AAAs and play causal roles in aneurysm pathogenesis, it should be emphasized that the majority of SNPs do not actually cause disease. In addition to GWAS, other studies have uncovered epigenetic causes of disease that regulate expression of genes known to be important in AAA pathogenesis. This review describes many of these genetic and epigenetic contributors of AAAs, which altogether provide a deeper insight into AAA pathogenesis.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155527/1/cge13705.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155527/2/cge13705_am.pd
Bredon cohomology and robot motion planning
Acknowledgements Farber was partially supported by the EPSRC, by the IIAS and by the Marie Curie Actions, FP7, in the frame of the EURIAS Fellowship Programme. Lupton and Oprea were partially supported by grants from the Simons Foundation (# 209575 and # 244393). This research was supported through the programme Research in pairs by the Mathematisches Forschungsinstitut Oberwolfach in 2017.Peer reviewedPostprin
An upper bound for topological complexity
This work was partially supported by a grant from the Simons Foundation: (#244393 to John Oprea). The authors would like to thank the Mathematisches Forschungsinstitut Oberwolfach for its generosity in supporting a July 2017 Research in Pairs stay where this work was begun.Peer reviewedPostprin
Bone marrow transplantation alters the tremor phenotype in the murine model of globoid-cell leukodystrophy
Tremor is a prominent phenotype of the twitcher mouse, an authentic genetic model of Globoid-Cell Leukodystrophy (GLD, Krabbe’s disease). In the current study, the tremor was quantified using a force-plate actometer designed to accommodate low-weight mice. The actometer records the force oscillations caused by a mouse’s movements, and the rhythmic structure of the force variations can be revealed. Results showed that twitcher mice had significantly increased power across a broad band of higher frequencies compared to wildtype mice. Bone marrow transplantation (BMT), the only available therapy for GLD, worsened the tremor in the twitcher mice and induced a measureable alteration of movement phenotype in the wildtype mice. These data highlight the damaging effects of conditioning radiation and BMT in the neonatal period. The behavioral methodology used herein provides a quantitative approach for assessing the efficacy of potential therapeutic interventions for Krabbe’s disease
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