1,768 research outputs found
Representation Theory of Twisted Group Double
This text collects useful results concerning the quasi-Hopf algebra \D . We
give a review of issues related to its use in conformal theories and physical
mathematics. Existence of such algebras based on 3-cocycles with values in which mimic for finite groups Chern-Simons terms of gauge theories,
open wide perspectives in the so called "classification program". The
modularisation theorem proved for quasi-Hopf algebras by two authors some years
ago makes the computation of topological invariants possible. An updated,
although partial, bibliography of recent developments is provided.Comment: 15 pages, no figur
Generalised Fermat Hypermaps and Galois Orbits
We consider families of quasiplatonic Riemann surfaces characterised by the
fact that -- as in the case of Fermat curves of exponent -- their
underlying regular (Walsh) hypermap is the complete bipartite graph , where is an odd prime power. We will show that all these surfaces,
regarded as algebraic curves, are defined over abelian number fields. We will
determine the orbits under the action of the absolute Galois group, their
minimal fields of definition, and in some easier cases also their defining
equations. The paper relies on group-- and graph--theoretic results by G. A.
Jones, R. Nedela and M.\v{S}koviera about regular embeddings of the graphs
[JN\v{S}] and generalises the analogous question for maps treated in
[JStW], partly using different methods.Comment: 14 pages, new version with extended introduction, minor corrections
and updated reference
Red-Shifted Firefly Luciferase Optimized for Candida albicans In vivo Bioluminescence Imaging.
Candida albicans is a major fungal pathogen causing life-threatening diseases in immuno-compromised patients. The efficacy of current drugs to combat C. albicans infections is limited, as these infections have a 40-60% mortality rate. There is a real need for novel therapeutic approaches, but such advances require a detailed knowledge of C. albicans and its in vivo pathogenesis. Additionally, any novel antifungal drugs against C. albicans infections will need to be tested for their in vivo efficacy over time. Fungal pathogenesis and drug-mediated resolution studies can both be evaluated using non-invasive in vivo imaging technologies. In the work presented here, we used a codon-optimized firefly luciferase reporter system for detecting C. albicans in mice. We adapted the firefly luciferase in order to improve its maximum emission intensity in the red light range (600-700 nm) as well as to improve its thermostability in mice. All non-invasive in vivo imaging of experimental animals was performed with a multimodal imaging system able to detect luminescent reporters and capture both reflectance and X-ray images. The modified firefly luciferase expressed in C. albicans (Mut2) was found to significantly increase the sensitivity of bioluminescence imaging (BLI) in systemic infections as compared to unmodified luciferase (Mut0). The same modified bioluminescence reporter system was used in an oropharyngeal candidiasis model. In both animal models, fungal loads could be correlated to the intensity of emitted light. Antifungal treatment efficacies were also evaluated on the basis of BLI signal intensity. In conclusion, BLI with a red-shifted firefly luciferase was found to be a powerful tool for testing the fate of C. albicans in various mice infection models
Spatial Mixing and Non-local Markov chains
We consider spin systems with nearest-neighbor interactions on an -vertex
-dimensional cube of the integer lattice graph . We study the
effects that exponential decay with distance of spin correlations, specifically
the strong spatial mixing condition (SSM), has on the rate of convergence to
equilibrium distribution of non-local Markov chains. We prove that SSM implies
mixing of a block dynamics whose steps can be implemented
efficiently. We then develop a methodology, consisting of several new
comparison inequalities concerning various block dynamics, that allow us to
extend this result to other non-local dynamics. As a first application of our
method we prove that, if SSM holds, then the relaxation time (i.e., the inverse
spectral gap) of general block dynamics is , where is the number of
blocks. A second application of our technology concerns the Swendsen-Wang
dynamics for the ferromagnetic Ising and Potts models. We show that SSM implies
an bound for the relaxation time. As a by-product of this implication we
observe that the relaxation time of the Swendsen-Wang dynamics in square boxes
of is throughout the subcritical regime of the -state
Potts model, for all . We also prove that for monotone spin systems
SSM implies that the mixing time of systematic scan dynamics is . Systematic scan dynamics are widely employed in practice but have
proved hard to analyze. Our proofs use a variety of techniques for the analysis
of Markov chains including coupling, functional analysis and linear algebra
Resonant Magnetic Vortices
By using the complex angular momentum method, we provide a semiclassical
analysis of electron scattering by a magnetic vortex of Aharonov-Bohm-type.
Regge poles of the -matrix are associated with surface waves orbiting around
the vortex and supported by a magnetic field discontinuity. Rapid variations of
sharp characteristic shapes can be observed on scattering cross sections. They
correspond to quasibound states which are Breit-Wigner-type resonances
associated with surface waves and which can be considered as quantum analogues
of acoustic whispering-gallery modes. Such a resonant magnetic vortex could
provide a new kind of artificial atom while the semiclassical approach
developed here could be profitably extended in various areas of the physics of
vortices.Comment: 6 pages, 7 figure
How Yeast Antifungal Resistance Gene Analysis Is Essential to Validate Antifungal Susceptibility Testing Systems.
The antifungal susceptibility testing (AFST) of yeast pathogen alerts clinicians about the potential emergence of resistance. In this study, we compared two commercial microdilution AFST methods: Sensititre YeastOne read visually (YO) and MICRONAUT-AM read visually (MN) or spectrophotometrically (MNV), interpreted with Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing criteria, respectively.
Overall, 97 strains from 19 yeast species were measured for nine antifungal drugs including a total of 873 observations. First, the minimal inhibitory concentration (MIC) was compared between YO and MNV, and between MNV and MN, either directly or by assigning them to five susceptibility categories. Those categories were based on the number of MIC dilutions around the breakpoint or epidemiological cut-off reference values (ECOFFs or ECVs). Second, YO and MNV methods were evaluated for their ability to detect the elevation of MICs due to mutation in antifungal resistance genes, thanks to pairs or triplets of isogenic strains isolated from a single patient along a treatment previously analyzed for antifungal resistance gene mutations. Reproducibility measurement was evaluated, thanks to three quality control (QC) strains.
YO and MNV direct MIC comparisons obtained a global agreement of 67%. Performing susceptibility category comparisons, only 22% and 49% of the MICs could be assigned to categories using breakpoints and ECOFFs/ECVs, respectively, and 40% could not be assigned due to the lack of criteria in both consortia. The YO and MN susceptibility categories gave accuracies as low as 50%, revealing the difficulty to implement this method of comparison. In contrast, using the antifungal resistance gene sequences as a gold standard, we demonstrated that both methods (YO and MN) were equally able to detect the acquisition of resistance in the Candida strains, even if MN showed a global lower MIC elevation than YO. Finally, no major differences in reproducibility were observed between the three AFST methods.
This study demonstrates the valuable use of both commercial microdilution AFST methods to detect antifungal resistance due to point mutations in antifungal resistance genes. We highlighted the difficulty to conduct conclusive analyses without antifungal gene sequence data as a gold standard. Indeed, MIC comparisons taking into account the consortia criteria of interpretation remain difficult even after the effort of harmonization
Heat Kernel Bounds for the Laplacian on Metric Graphs of Polygonal Tilings
We obtain an upper heat kernel bound for the Laplacian on metric graphs
arising as one skeletons of certain polygonal tilings of the plane, which
reflects the one dimensional as well as the two dimensional nature of these
graphs.Comment: 8 page
Adiabatic times for Markov chains and applications
We state and prove a generalized adiabatic theorem for Markov chains and
provide examples and applications related to Glauber dynamics of Ising model
over Z^d/nZ^d. The theorems derived in this paper describe a type of adiabatic
dynamics for l^1(R_+^n) norm preserving, time inhomogeneous Markov
transformations, while quantum adiabatic theorems deal with l^2(C^n) norm
preserving ones, i.e. gradually changing unitary dynamics in C^n
- …