Ghost Surface Research Articles

Ghost surface magnon-plasmon polariton in antiferromagnets covered with graphene monolayer

Ghost surface magnon-plasmon polariton in antiferromagnets covered with graphene monolayer

Unique ghost surface phonon polaritons in biaxially hyperbolic materials.

We predicted peculiar ghost surface phonon polaritons in biaxially hyperbolic materials, where the two hyperbolic principal axes lie in the plane of propagation. We took the biaxially-hyperbolic α-MoO3 as one example of the materials to numerically simulate the ghost surface phonon polaritons. We found three unique ghost surface polaritons to appear in three enclosed wavenumber-frequency regions, respectively. These ghost surface phonon polaritons have different features from the surface phonon polaritons found previously, i.e., they are some hybrid-polarization surface waves composed of two coherent evanescent branch-waves in the α-MoO3 crystal. The interference of branch-waves leads to that their Poynting vector and electromagnetic fields both exhibit the oscillation-attenuation behavior along the surface normal, or a series of rapidly attenuated fringes. We found that the in-plane hyperbolic anisotropy and low-symmetric geometry of surface are the two necessary conditions for the existence of these ghost surface polaritons.

Ghost surface polaritons at oblique antiferromagnetic surface

We investigated hybrid-polarization surface magnon polaritons at the oblique surface of antiferromagnet (AF) in an external magnetic field pointed along the AF easy axis, where the easy axis does not lie in the AF surface. According to the direction of surface-polariton propagation, there are two specific geometries. In geometry-I, where the direction of propagation is vertical to the easy axis, we found two hybrid-polarization surface polaritons (HSPs), which are highly nonreciprocal. They are one ordinary hybrid-polarization surface polariton (called a HSP still) and one ghost surface polariton (GSP-I). GSP-I can exist not only inside but also outside the AF reststrahlen frequency bands and originates from the external magnetic field. In Geometry-II with the easy axis in the propagation plane, we predicted another ghost surface polariton (GSP-II). GSP-II is a TE surface wave and is reciprocal. Another difference between the two GSPs is that the Poynting vector of GSP-I is of oscillation-attenuation but that of GSP-II monotonously decays with the distance from the surface and GSP-II exists only in the reststrahlen band without external magnetic field. This study further enlarges the family of surface polariton and widens the window of polariton application.

Ghost surface polaritons in naturally uniaxial hyperbolic materials

We investigated ghost surface phonon polaritons localized in a naturally uniaxial hyperbolic material, where the longitudinal axis (optical axis) is at any angle with respect to the surface plane. Two ghost surface phonon polaritons (GSPs) were found in the two Reststrahlen frequency bands, respectively. They are two TM surface waves, and their electromagnetic fields not only attenuate but also oscillate with the distance away from the surface. Unlike conventional surface phonon polaritons, GSPs are virtual surface phonon-polariton modes without electrostatic limit. The numerical simulations of the GSP dispersion and polarization properties were based on the hexagonal boron nitride, and the numerical simulation of the attenuated total reflection (ATR) experiment demonstrates the existence of the GSPs and prove their excitability and observability.

Spin angular momentum and nonreciprocity of ghost surface polariton in antiferromagnets.

We investigated the spin angular momentum (SAM) and nonreciprocity of ghost surface polariton (GSP) at the surface of an antiferromagnet (AF) in the normal geometry, where the AF easy axis and external field (H0) both are normal to the AF surface. We found that the dispersion equation is invariant when the inversions of wavevector and external magnetic field, k→-k and H0→-H0, are taken. However, its polarization and SAM are nonreciprocal. The SAM is vertical to the propagation direction of GSP, and consists of two components. We analytically found that the in-plane component is locked to H0, or it is changed in sign due to the inversion of H0. The out-plane one is locked to k since it is changed in sign as the inversion of k is taken. Either component contains an electric part and a magnetic part. Above the AF surface, the two electric parts form the left-handed triplet with the wavevector k, but the two magnetic parts form the right-handed triplet with k. In the AF, the chirality of the SAM changes with the distance from the surface. The SAM is very large on or near the surface and it may be very interesting for the manipulation of micron and nano particles on the AF surface. These are obviously different from the relevant features of conventional surface polaritons. The SAM also is field-tunable.

Ghost surface polariton in antiferromagnets

A surface polariton was predicted in antiferromagnets in a simple geometry. It exhibits interesting characteristics. Its electromagnetic fields and energy-flux density both oscillate and attenuate with the distance from the surface. It is a ghost surface polariton (GSP) and is a magnetic-field-tunable surface polariton. The branch-interference produces a series of rapidly attenuated fringes. It exists only in an external magnetic field along the easy axis. The attenuated total reflection spectra obtained in the Otto configuration accurately demonstrate this GSP and show its excitation or observation path.

Unique surface polaritons and their transitions in metamaterials.

We investigated surface polaritons in a metamaterial composed of polar-crystal layers and antiferromagnetic layers. In a specific geometry, two surface polaritons were predicted, which are a unique ghost surface polariton (GSP) and surface hybrid-polarization polariton (SHP). The two surface polaritons occupy different segments of one smooth dispersion curve and are magnetically tunable. An external magnetic field along the antiferromagnetic easy axis can bring about the switch or transition between the two surface polaritons and meanwhile performs the necessary condition for the existence of two surface polaritons. In the metamaterial, either surface polariton consists of two branch waves. The branch waves of the GSP are coherent and have the same amplitude and different phases, but those of the SHP are not coherent and have different amplitudes and phases. The main characteristic of the GSP is that its fields oscillate and attenuate with the distance away from the metamaterial surface and exhibit interferent fringes on the plane normal to the surface.

Salmonella enterica serovar Enteritidis ghosts displaying a surface FliC adjuvant elicit a robust immune response and effective protection against virulent challenge

Salmonella Enteritidis (SE) is one of the most common culprits of foodborne disease in humans due to its horizontal transmission from infected animals to humans. The development of a safe vaccine against Salmonella would be important for both farm animals and humans concerning disease containment. The SE ghosts carrying FliC were genetically constructed using a special ghost plasmid pJHL184 that co-expressed FliC and the phage lysis gene E. These SE ghosts were characterized by ghost generation efficacy by increasing the culture temperature to “42 °C” in the absence of L-arabinose. This temperature change led to an ghost generation with almost complete lysis of the SE host strain in 48 hs. The expression of FliC was confirmed by Western blot analysis. Also, indirect ELISA was used to prove FliC specific antibody generation in immunized mice. The parenteral adjuvant effect of the FliC antigen was demonstrated by immunizing mice with pJHL184::flC, pJHL184 alone, or PBS alone. The mice were intramuscularly immunized at six weeks of age (n = 8) and boosted after three weeks of primary inoculation. A total of 32 mice were equally divided into four groups. Each group was treated with pJHL-ghosts alone, ghost surface displaying FliC adjuvant, and compared to the PBS and naïve control groups. The immunized mice demonstrated greater IgG and IgA antibody responses than did the PBS control group. Furthermore, the addition of the ghosts to the FliC led to a significant increase in both the humoral and cell-mediated immune responses compared to those in the ghost alone group. Besides, the in vitro antigen uptake and presentation studies revealed efficient antigen presentation on the mouse macrophage cell surfaces. This finding further corroborated the potential efficacy of immune stimulation by SE ghosts. After the virulent challenge, we observed a significant reduction in the bacterial load in the spleen and liver tissues in SE ghosts surface, displaying FliC adjuvant. Our results demonstrate a safe and effective strategy to prevent salmonellosis. They also suggest that the surface expression of flagellin (FliC) significantly enhances antigen-specific humoral and cell-mediated immune responses. This FliC expression can also enhance the protective efficacy of the bacterial ghosts-based vaccine against virulent challenge.

Ghost surface phononic polaritons in ionic-crystal metamaterial

Ghost electromagnetic waves were recently predicted in anisotropic transparent materials by E. Narimanov. In this paper, three ghost surface phonon polaritons (GSPhPs) are predicted at the single oblique surface of layered ionic-crystal metamaterial (ICMM). They propagate along the surface, but their electromagnetic fields in the ICMM sinusoidally oscillate and exponentially attenuate with the distance from the surface. The three GSPhPs are mutually different in character. An additional unique GSPhP is found on the boundary between the effective metal and hyperbolic regions of the ICMM, and its characteristics are as follows: (1) its energy can only conduct outside the ICMM; (2) its wave vector and electric field possess the same direction transverse to the material optical axis. The conditions for the existence of the GSPhPs are discussed. The numerical results were obtained based on ZnS/SiO2 metamaterials.

Versatile surface tension and adhesion for SPH fluids

Realistic handling of fluid-air and fluid-solid interfaces in SPH is a challenging problem. The main reason is that some important physical phenomena such as surface tension and adhesion emerge as a result of inter-molecular forces in a microscopic scale. This is different from scalar fields such as fluid pressure, which can be plausibly evaluated on a macroscopic scale using particles. Although there exist techniques to address this problem for some specific simulation scenarios, there does not yet exist a general approach to reproduce the variety of effects that emerge in reality from fluid-air and fluid-solid interactions. In order to address this problem, we present a new surface tension force and a new adhesion force. Different from the existing work, our surface tension force can handle large surface tensions in a realistic way. This property lets our approach handle challenging real scenarios, such as water crown formation, various types of fluid-solid interactions, and even droplet simulations. Furthermore, it prevents particle clustering at the free surface where inter-particle pressure forces are incorrect. Our adhesion force allows plausible two-way attraction of fluids and solids and can be used to model different wetting conditions. By using our forces, modeling surface tension and adhesion effects do not require involved techniques such as generating a ghost air phase or surface tracking. The forces are applied to the neighboring fluid-fluid and fluid-boundary particle pairs in a symmetric way, which satisfies momentum conservation. We demonstrate that combining both forces allows simulating a variety of interesting effects in a plausible way.

Generalized action-angle coordinates defined on island chains

Straight-field-line coordinates are very useful for representing magnetic fields in toroidally confined plasmas, but fundamental problems arise regarding their definition in 3D geometries because of the formation of islands and chaotic field regions, i.e. non-integrability. In Hamiltonian dynamical systems terminology these coordinates are similar to action-angle variables, but these are normally defined only for integrable systems. In order to describe 3D magnetic field systems, a generalization of this concept was proposed recently by the present authors that unified the concepts of ghost surfaces and quadratic-flux-minimizing (QFMin) surfaces. This was based on a simple canonical transformation generated by a change of variable θ = θ(Θ, ζ), where θ and ζ are poloidal and toroidal angles, respectively, with Θ a new poloidal angle chosen to give pseudo-orbits that are (a) straight when plotted in the ζ, Θ plane and (b) QFMin pseudo-orbits in the transformed coordinate. These two requirements ensure that the pseudo-orbits are also (c) ghost pseudo-orbits. In this paper, it is demonstrated that these requirements do not uniquely specify the transformation owing to a relabelling symmetry. A variational method of solution that removes this lack of uniqueness is proposed.

Are ghost surfaces quadratic-flux-minimizing?

Two candidates for “almost-invariant” toroidal surfaces passing through magnetic islands, namely quadratic-flux-minimizing (QFMin) surfaces and ghost surfaces, use families of periodic pseudo-orbits (i.e. paths for which the action is not exactly extremal). QFMin pseudo-orbits, which are coordinate-dependent, are field lines obtained from a modified magnetic field, and ghost-surface pseudo-orbits are obtained by displacing closed field lines in the direction of steepest descent of magnetic action, ∮ A ⋅ dl . A generalized Hamiltonian definition of ghost surfaces is given and specialized to the usual Lagrangian definition. A modified Hamilton's Principle is introduced that allows the use of Lagrangian integration for calculation of the QFMin pseudo-orbits. Numerical calculations show QFMin and Lagrangian ghost surfaces give very similar results for a chaotic magnetic field perturbed from an integrable case, and this is explained using a perturbative construction of an auxiliary poloidal angle for which QFMin and Lagrangian ghost surfaces are the same up to second order. While presented in the context of 3-dimensional magnetic field line systems, the concepts are applicable to defining almost-invariant tori in other 1 1 2 degree-of-freedom nonintegrable Lagrangian/Hamiltonian systems.

Temperature Contours and Ghost Surfaces for Chaotic Magnetic Fields

Steady state solutions for anisotropic heat transport in a chaotic magnetic field are determined numerically and compared to a set of "ghost surfaces"-surfaces constructed via an action-gradient flow between the minimax and minimizing periodic orbits. The ghost surfaces are in remarkable agreement with the temperature contours.

Almost-invariant surfaces for magnetic field-line flows

Two approaches to defining almost-invariant surfaces for magnetic fields with imperfect magnetic surfaces are compared. Both methods are based on treating magnetic field-line flow as a 1½-dimensional Hamiltonian (or Lagrangian) dynamical system. In thequadratic-flux minimizing surfaceapproach, the integral of the square of the action gradient over the toroidal and poloidal angles is minimized, while in theghost surfaceapproach a gradient flow between a minimax and an action-minimizing orbit is used. In both cases the almost-invariant surface is constructed as a family of periodic pseudo-orbits, and consequently it has a rational rotational transform. The construction of quadratic-flux minimizing surfaces is simple, and easily implemented using a new magnetic field-line tracing method. The construction of ghost surfaces requires the representation of a pseudo field line as an (in principle) infinite-dimensional vector and also is inherently slow for systems near integrability. As a test problem the magnetic field-line Hamiltonian is constructed analytically for a topologically toroidal, non-integrable ABC-flow model, and both types of almost-invariant surface are constructed numerically.

Effect of anionic polymers on fusion of Sendai virus with human erythrocyte ghosts

The effect of anionic polymers (dextran sulfate, heparin and chondroitin sulfate) on fusion of Sendai virus with erythrocyte ghosts was studied. The effect of pH on the activity of these anionic polymers was also investigated. In order to examine the interaction of such polymers with the Sendai virion and erythrocyte ghost surfaces, the binding of virions to erythrocyte ghosts and the aggregation of virions and/or erythrocyte ghosts were also measured with respect to the same parameters. It was found that the anionic polymers suppressed the fusion of Sendai virus with erythrocyte ghosts. The order of effectiveness of the polymers in suppression was dextran sulfate > heparin > chondroitin sulfate, for the application of a same quantity (weight/ml) of the polymers. The lower the pH of the suspending medium, the more effective were the polymers in suppressing virion-erythrocyte ghost aggregation and fusion. The suppression of fusion was dependent on the concentration of the polymers applied: the higher the concentration of the polymer applied, the more the suppression was observed. Evidence from binding studies, turbidity measurements and electrophoretic mobility measurements indicates that the anionic polymers interact preferentially with the virion surface.

The effect of EDTA, cations, and various buffers on the morphology of erythrocyte membranes: an electron-microscopic study

Membranes of human erythrocytes were prepared by stepwise osmotic hemolysis in Ca2+-free solutions. Examination with the electron microscope after negative staining showed some short, conelike protuberances on the surface of about 20 percent of the ghosts, while 80 percent were round, intact spheres. After Ca2+ treatment, all membranes were round and intact. After exposure to ethylenediaminetetraacetic acid (EDTA) (1.0 mM, pH 7.4), the entire ghost surface was covered with long, thin extrusions called stromalytic forms (about 460 per cell). Their sizes, shapes, and fine structure are described. Exposure to ionic calcium (1.4 times 10-minus 4M) abolished the EDTA-induced stromalytic forms. A second exposure to EDTA reversed this Ca2+ effect. ATP, like EDTA, produced stromalytic forms. EDTA- induced stromalytic forms were also abolished by Zn2+, La3+, and Nd3+ at concentrations of 1–5 times 10-minus 4 M. Mg2+ at 10-minus 2 M was ineffective. Ghosts were prepared by graded lysis in various buffers. Those prepared in phosphate were the most stable and provided consistent EDTA effects and Ca2+ reversal. Ghosts in Tris-HCl showed breakdown unless salt was added. Moderately satisfactory ghosts were also obtained in Hepes-NaOH buffer and salt.

The Effect of EDTA, Cations, and Various Buffers on the Morphology of Erythrocyte Membranes: An Electron-microscopic Study

Membranes of human erythrocytes were prepared by stepwise osmotic hemolysis in Ca2+-free solutions. Examination with the electron microscope after negative staining showed some short, conelike protuberances on the surface of about 20 percent of the ghosts, while 80 percent were round, intact spheres. After Ca2+ treatment, all membranes were round and intact. After exposure to ethylenediaminetetraacetic acid (EDTA) (1.0 mM, pH 7.4), the entire ghost surface was covered with long, thin extrusions called stromalytic forms (about 460 per cell). Their sizes, shapes, and fine structure are described. Exposure to ionic calcium (1.4 times 10-minus 4M) abolished the EDTA-induced stromalytic forms. A second exposure to EDTA reversed this Ca2+ effect. ATP, like EDTA, produced stromalytic forms. EDTA-induced stromalytic forms were also abolished by Zn2+, La3+, and Nd3+ at concentrations of 1-5 times 10-minus 4 M. Mg2+ at 10-minus 2 M was ineffective. Ghosts were prepared by graded lysis in various buffers. Those prepared in phosphate were the most stable and provided consistent EDTA effects and Ca2+ reversal. Ghosts in Tris-HCl showed breakdown unless salt was added. Moderately satisfactory ghosts were also obtained in Hepes-NaOH buffer and salt.