Scattering of dislocated wavefronts by vertical vorticity and the Aharonov-Bohm effect II: Dispersive waves

Previous results on the scattering of surface waves by vertical vorticity on shallow water are generalized to the case of dispersive water waves. Dispersion effects are treated perturbatively around the shallow water limit, to first order in the ratio of depth to wavelength. The dislocation of the incident wavefront, analogous to the Aharonov-Bohm effect, is still observed. At short wavelengths the scattering is qualitatively similar to the nondispersive case. At moderate wavelengths, however, there are two markedly different scattering regimes according to wether the capillary length is smaller or larger than $\sqrt{3}$ times depth. The dislocation is characterized by a parameter that depends both on phase and group velocity. The validity range of the calculation is the same as in the shallow water case: wavelengths small compared to vortex radius, and low Mach number. The implications of these limitations are carefully considered.Comment: 30 pages, 11 figure

Integration of twisted Poisson structures

Poisson manifolds may be regarded as the infinitesimal form of symplectic groupoids. Twisted Poisson manifolds considered by Severa and Weinstein [math.SG/0107133] are a natural generalization of the former which also arises in string theory. In this note it is proved that twisted Poisson manifolds are in bijection with a (possibly singular) twisted version of symplectic groupoids.Comment: 12 pages; minor corrections (especially in terminology: "twisted symplectic" replaces "quasi-symplectic"), references updated; to appear in J. Geom. Phy

On the divine clockwork: the spectral gap for the correspondence limit of the Nelson diffusion generator for the atomic elliptic state

The correspondence limit of the atomic elliptic state in three dimensions is discussed in terms of Nelson's stochastic mechanics. In previous work we have shown that this approach leads to a limiting Nelson diffusion and here we discuss in detail the invariant measure for this process and show that it is concentrated on the Kepler ellipse in the plane z=0. We then show that the limiting Nelson diffusion generator has a spectral gap; thereby proving that in the infinite time limit the density for the limiting Nelson diffusion will converge to its invariant measure. We also include a summary of the Cheeger and Poincare inequalities both of which are used in our proof of the existence of the spectral gap.Comment: 30 pages, 5 figures, submitted to J. Math. Phy

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 $S$-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

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

Extended phase space for a spinning particle

Extended phase space of an elementary (relativistic) system is introduced in the spirit of the Souriau's definition of the `space of motions' for such system. Our formulation is generally applicable to any homogeneous space-time (e.g. de Sitter) and also to Poisson actions. Calculations concerning the Minkowski case for non-zero spin particles show an intriguing alternative: we should either accept two-dimensional trajectories or (Poisson) noncommuting space-time coordinates.Comment: 12 pages, late

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

Single Strand Annealing Plays a Major Role in RecA-Independent Recombination between Repeated Sequences in the Radioresistant Deinococcus radiodurans Bacterium

© 2015 Ithurbide et al. The bacterium Deinococcus radiodurans is one of the most radioresistant organisms known. It is able to reconstruct a functional genome from hundreds of radiation-induced chromosomal fragments. Our work aims to highlight the genes involved in recombination between 438 bp direct repeats separated by intervening sequences of various lengths ranging from 1,479 bp to 10,500 bp to restore a functional tetA gene in the presence or absence of radiation-induced DNA double strand breaks. The frequency of spontaneous deletion events between the chromosomal direct repeats were the same in recA+ and in ΔrecA, ΔrecF, and ΔrecO bacteria, whereas recombination between chromosomal and plasmid DNA was shown to be strictly dependent on the RecA and RecF proteins. The presence of mutations in one of the repeated sequence reduced, in a MutS-dependent manner, the frequency of the deletion events. The distance between the repeats did not influence the frequencies of deletion events in recA+as well in ΔrecA bacteria. The absence of the UvrD protein stimulated the recombination between the direct repeats whereas the absence of the DdrB protein, previously shown to be involved in DNA double strand break repair through a single strand annealing (SSA) pathway, strongly reduces the frequency of RecA- (and RecO-) independent deletions events. The absence of the DdrB protein also increased the lethal sectoring of cells devoid of RecA or RecO protein. γ-irradiation of recA+cells increased about 10-fold the frequencies of the deletion events, but at a lesser extend in cells devoid of the DdrB protein. Altogether, our results suggest a major role of single strand annealing in DNA repeat deletion events in bacteria devoid of the RecA protein, and also in recA+bacteria exposed to ionizing radiation

Variations de tolérance aux pesticides agricoles des diatomées périphytiques dans une rivière contaminée : une analyse de l'échelle des communautés à celle des populations

3rd International Conference on EnvironmentalManagement, Engineering, Planning and Economics (CEMEPE 2011) & SECOTOX Conference, Skiathos, GRC, 19-/06/2011 - 24/06/2011International audiencePeriphytic diatoms are an important phototrophic component of river biofilm and are used in situ for the bioindication of pollution as well as in laboratory ecotoxicological tests to assess the toxicity of contaminants. In spring 2009, phototrophic biofilm samples composed mostly of diatoms were collected in a small river and their sensitivity to the herbicide diuron was estimated via photosynthesis bioassays. A large difference in tolerance to diuron was demonstrated between two periphytic communities from an upstream unpolluted site and a downstream site subjected to high seasonal contamination by pesticides. The comparison of diatom community structure between sites revealed important variations of the relative abundance of some species which could explain this difference. Consequently, some of these species were isolated from the river in autumn when toxic pressure was low, and kept in culture for more than six months in uncontaminated water. Acute toxicity tests of diuron based on growth inhibition were then performed on each species. Surprisingly the sensitivities of the species as estimated by EC50 were almost the same. However two strains of another species that could be isolated from each site of the river showed significant differences in tolerance to diuron and copper, another contaminant of the river. These results suggest the importance of adaptation at the intraspecific level in the induction of periphytic community tolerance to toxicants and the probably low sensitivity of bioindication methods to assess river contaminations