On the internal modes in sine-Gordon chain

We address the issue of internal modes of a kink of a discrete sine-Gordon equation. The main point of the present study is to elucidate how the antisymmetric internal mode frequency dependence enters the quasicontinuum spectrum of nonlocalized waves. We analyze the internal frequency dependencies as functions of both the number of cites and discreteness parameter and explain the origin of spectrum peculiarity which arises after the frequency dependence of antisymmetric mode returns back to the continuous spectrum at some nonzero value of the intersite coupling.Comment: 5 pages, 3 figure

Numerical model of the spatio-temporal dynamics in a water strider group

The water strider group demonstrates a very complex dynamics consisting of competition for the food items, territoriality and aggression to the conspecific individuals, escaping from the predators, etc. The situation is even more complex due to the presence of different instars, which in most water strider species live in the same habitat and occupy the same niche. The presented swarm model of water striders demonstrates the realistic population dynamics. For the swarm formation in the model, attraction and repulsion forces were used. Animal motion in the model takes into account inertia and kinetic energy dissipation effects. The model includes three different rates related to the growth of individuals: food appearance rate, food assimilation rate, and stored energy loss rate. The results of our modeling show that the size distribution of individuals seems to be an adequate measure for population status, and it has a characteristic shape for different model parameter combinations. Distribution of the distances between nearest neighbors is other important measure of the population density and its dynamics. Parameters of the model can be tuned in such a way, that the shape of both distributions in a steady phase coincides with that shape observed in a natural population, which helps to understand the factors leading to particular momentary distribution of both parameters (size and distance) in the population. From this point of view, the model can predict how both distributions can further develop from certain state depending on particular combination of factors

Root Hair Adhesion in Posidonia oceanica (L.) Delile Seedlings: A Numerical Modelling Approach

Animals and plants use adhesion to move, to anchor to a substrate, or to disperse seeds and fruits. Some plants developed a root pad as a common strategy to adhere to consolidated substrates. In the marine environment, the seagrass Posidonia oceanica attaches fi rmly to consolidated substrates via adhesive root hairs, forming a pad structure. We used novel morphological and ultrastructural data to develop a numerical model to study the dynamics of root hair adhesion during contact formation on rough consolidated substrates for this species. Morphological analysis, conducted using Scanning Electron Microscope, highlighted the role of root hair branching in pad formation. Transmission Electron Microscope microscopy allowed us to identify a glue-like substance at the pad/ substrate interface. The numerical model highlighted the role played by the cell wall ’ s elasticity in pad formation and its importance in guaranteeing a fi rm adhesion. Furthermore, the effectiveness of these mechanisms was assessed at different simulated roughness levels. Increasing knowledge on the adhesion mechanism of seagrass to consolidated substrates could be pivotal in developing advanced seedling-based restoration protocols. The fi ndings of this study could contribute to restoration activities planned to contrast seagrass regression. Transplanting initiatives using seedlings can now better address the search for suitable and low-impact ways to fi x germinated plants to the substrate

The Relation between Radio Polarization and Gamma-ray Emission in AGN Jets

We have compared the parsec-scale jet linear polarization properties of the Fermi LAT-detected and non-detected sources in the complete flux-density-limited (MOJAVE-1) sample of highly beamed AGN. Of the 123 MOJAVE sources, 30 were detected by the LAT during its first three months of operation. We find that during the era since the launch of Fermi, the unresolved core components of the LAT-detected jets have significantly higher median fractional polarization at 15 GHz. This complements our previous findings that these LAT sources have higher apparent jet speeds, brightness temperatures and Doppler factors, and are preferentially found in higher activity states.Comment: 6 pages, 3 figures, to appear in the proceedings of "High Energy Phenomena In Relativistic Outflows II" (Buenos Aires, Argentina, October 26-30, 2009) International Journal of Modern Physics

Lattice-Induced Double-Valley Degeneracy Lifting in Magnetic Field in Graphene

We show that the recently discovered double-valley splitting of the low-lying Landau level(s) in the Quantum Hall Effect in graphene can be explained as perturbative orbital interaction of intra- and inter-valley microscopic orbital currents with a magnetic field. This effect is provided by the translational-non-invariant terms corresponding to graphene's crystallographic honeycomb symmetry but do not exist in the relativistic theory of massless Dirac Fermions in Quantum Electrodynamics. We discuss recent data in view of these results

Soliton propagation through a disordered system:statistics of the transmission delay

We have studied the soliton propagation through a segment containing random pointlike scatterers. In the limit of small concentration of scatterers when the mean distance between the scatterers is larger than the soliton width, a method has been developed for obtaining the statistical characteristics of the soliton transmission through the segment. The method is applicable for any classical particle traversing through a disordered segment with the given velocity transformation after each act of scattering. In the case of weak scattering and relatively short disordered segment the transmission time delay of a fast soliton is mostly determined by the shifts of the soliton center after each act of scattering. For sufficiently long segments the main contribution to the delay is due to the shifts of the amplitude and velocity of a fast soliton after each scatterer. Corresponding crossover lengths for both cases of light and heavy solitons have been obtained. We have also calculated the exact probability density function of the soliton transmission time delay for a sufficiently long segment. In the case of weak identical scatterers the latter is a universal function which depends on a sole parameter—the mean number of scatterers in a segment

High conservation combined with high plasticity: genomics and evolution of Borrelia bavariensis

BackgroundBorrelia bavariensis is one of the agents of Lyme Borreliosis (or Lyme disease) in Eurasia. The genome of the Borrelia burgdorferi sensu lato species complex, that includes B. bavariensis, is known to be very complex and fragmented making the assembly of whole genomes with next-generation sequencing data a challenge.ResultsWe present a genome reconstruction for 33 B. bavariensis isolates from Eurasia based on long-read (Pacific Bioscience, for three isolates) and short-read (Illumina) data. We show that the combination of both sequencing techniques allows proper genome reconstruction of all plasmids in most cases but use of a very close reference is necessary when only short-read sequencing data is available. B. bavariensis genomes combine a high degree of genetic conservation with high plasticity: all isolates share the main chromosome and five plasmids, but the repertoire of other plasmids is highly variable. In addition to plasmid losses and gains through horizontal transfer, we also observe several fusions between plasmids. Although European isolates of B. bavariensis have little diversity in genome content, there is some geographic structure to this variation. In contrast, each Asian isolate has a unique plasmid repertoire and we observe no geographically based differences between Japanese and Russian isolates. Comparing the genomes of Asian and European populations of B. bavariensis suggests that some genes which are markedly different between the two populations may be good candidates for adaptation to the tick vector, (Ixodes ricinus in Europe and I. persulcatus in Asia).ConclusionsWe present the characterization of genomes of a large sample of B. bavariensis isolates and show that their plasmid content is highly variable. This study opens the way for genomic studies seeking to understand host and vector adaptation as well as human pathogenicity in Eurasian Lyme Borreliosis agents.Peer reviewe

Instabilities and Bifurcations of Nonlinear Impurity Modes

We study the structure and stability of nonlinear impurity modes in the discrete nonlinear Schr{\"o}dinger equation with a single on-site nonlinear impurity emphasizing the effects of interplay between discreteness, nonlinearity and disorder. We show how the interaction of a nonlinear localized mode (a discrete soliton or discrete breather) with a repulsive impurity generates a family of stationary states near the impurity site, as well as examine both theoretical and numerical criteria for the transition between different localized states via a cascade of bifurcations.Comment: 8 pages, 8 figures, Phys. Rev. E in pres

An analytical hierarchical model explaining the robustness and flaw-tolerance of the interlocking barb-barbule structure of bird feathers

This work is partially supported by the National Natural Science Foundation of China (NSFC) (No. 31300780, 11272091, 11422222, 31470043), the Fundamental Research Funds for the Central Universities (No. 2242016R30014), and ARC (FT140101152). NMP is supported by the European Research Council (ERC StG Ideas 2011 BIHSNAM no. 279985, ERC PoC 2015 SILKENE No. 693670) and by the European Commission under the Graphene Flagship (WP14 "Polymer Composites", No. 696656)

Localizing Sagittarius A* and M87 on Microarcsecond Scales with Millimeter VLBI

With the advent of the Event Horizon Telescope (EHT), a millimeter/sub-millimeter very-long baseline interferometer (VLBI), it has become possible to image a handful of black holes with sub-horizon resolutions. However, these images do not translate into microarcsecond absolute positions due to the lack of absolute phase information when an external phase reference is not used. Due to the short atmospheric coherence time at these wavelengths, nodding between the source and phase reference is impractical. However, here we suggest an alternative scheme which makes use of the fact that many of the VLBI stations within the EHT are arrays in their own right. With this we show that it should be possible to absolutely position the supermassive black holes at the centers of the Milky Way (Sgr A*) and M87 relative to nearby objects with precisions of roughly 1 microarcsecond. This is sufficient to detect the perturbations to Sgr A*'s position resulting from interactions with the stars and stellar-mass black holes in the Galactic cusp on year timescales, and severely constrain the astrophysically relevant parameter space for an orbiting intermediate mass black hole, implicated in some mechanisms for producing the young massive stars in the Galactic center. For M87, it allows the registering of millimeter images, in which the black hole may be identified by its silhouette against nearby emission, and existing larger scale radio images, eliminating present ambiguities in the nature of the radio core and inclination, opening angle, and source of the radio jet.Comment: 18 pages, 4 figures, Accepted for publication in Ap