Dynamics of nonlinear excitations of helically confined charges

We explore the long-time dynamics of a system of identical charged particles trapped on a closed helix. This system has recently been found to exhibit an unconventional deformation of the linear spectrum when tuning the helix radius. Here we show that the same geometrical parameter can affect significantly also the dynamical behaviour of an initially broad excitation for long times. In particular, for small values of the radius, the excitation disperses into the whole crystal whereas within a specific narrow regime of larger radii the excitation self-focuses, assuming finally a localized form. Beyond this regime, the excitation defocuses and the dispersion gradually increases again. We analyze this geometrically controlled nonlinear behaviour using an effective discrete nonlinear Schr\"{o}dinger model, which allows us among others to identify a number of breather-like excitations.Comment: 11 pages, 7 figure

Protection of pigs against challenge with virulent <i>Streptococcus suis</i> serotype 2 strains by a muramidase-released protein and extracellular factor vaccine

The efficacy of a muramidase-released protein (MRP) and extracellular factor (EF) vaccine in preventing infection and disease in pigs challenged either with a homologous or a heterologous Streptococcus suis serotype 2 strain (MRP EF ) was compared with the efficacy of a vaccine containing formalin-killed bacterin of S suis serotype 2 (MRP EF ). The enhancement of the immune response by different adjuvants (a water-in-oil emulsion [wo] and an aluminium hydroxide-based adjuvant [AH]) and their side effects were also studied. The MRP and EF were purified by affinity chromatography. Pigs were vaccinated twice at three weeks and six weeks of age and challenged intravenously with virulent S suis serotype 2 strains (MRP EF ) at eight weeks of age. At challenge, the pigs vaccinated with MRP EF/WO had high anti-MRP and anti-EF titres and were protected as effectively as pigs vaccinated with wo-formulated vaccines with bacterin. Eight of the nine pigs survived the challenge and almost no clinical signs of disease were observed. The titres obtained with the MRP EF/AH vaccine were low and only two of the five pigs were protected. Pigs vaccinated with either MRP or EF were less well protected; three of the four pigs died after challenge but the clinical signs of disease were significantly less severe than those observed in the placebo-vaccinated pigs. The protective capacity of the bacterin/AH vaccine was very low, and the mortality among these pigs was as high as in the placebo-vaccinated pigs (80 per cent). Postmortem histological examination revealed meningitis, polyserositis and arthritis in the clinically affected pigs. The results demonstrate that a subunit vaccine containing both MRP and EF, formulated with the wo adjuvant, protected pigs against challenge with virulent S suis type 2 strains

Classical scattering of charged particles confined on an inhomogeneous helix

We explore the effects arising due to the coupling of the center of mass and relative motion of two charged particles confined on an inhomogeneous helix with a locally modified radius. It is first proven that a separation of the center of mass and the relative motion is provided if and only if the confining manifold represents a homogeneous helix. In this case bound states of repulsively Coulomb interacting particles occur. For an inhomogeneous helix, the coupling of the center of mass and relative motion induces an energy transfer between the collective and relative motion, leading to dissociation of initially bound states in a scattering process. Due to the time reversal symmetry, a binding of the particles out of the scattering continuum is thus equally possible. We identify the regimes of dissociation for different initial conditions and provide an analysis of the underlying phase space via Poincar\'e surfaces of section. Bound states inside the inhomogeneity as well as resonant states are identified.Comment: 15 pages, 18 figure

Vortex-Bright Soliton Dipoles: Bifurcations, Symmetry Breaking and Soliton Tunneling in a Vortex-Induced Double Well

The emergence of vortex-bright soliton dipoles in two-component Bose-Einstein condensates through bifurcations from suitable eigenstates of the underlying linear system is examined. These dipoles can have their bright solitary structures be in phase (symmetric) or out of phase (anti-symmetric). The dynamical robustness of each of these two possibilities is considered and the out-of-phase case is found to exhibit an intriguing symmetry-breaking instability that can in turn lead to tunneling of the bright wavefunction between the two vortex "wells". We interpret this phenomenon by virtue of a vortex-induced double well system, whose spontaneous symmetry breaking leads to asymmetric vortex-bright dipoles, in addition to the symmetric and anti-symmetric ones. The theoretical prediction of these states is corroborated by detailed numerical computations.Comment: 14 pages, 8 figure