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Recently, a class of about 22 nucleotides (nt) small RNA has been discovered in many eukaryotes, termed microRNAs (miRNAs), which have a variety of functions. Many recent findings have demonstrated that viruses can also encode their own miRNAs. Meanwhile, other findings reveal a relationship between host miRNA and viral infection. These findings suggest a tight relationship between host and viral infection via miRNA pathway. This article introduces the miRNAs encoded by viruses and reviews the advances of the interaction of the mammalian host miRNAs and viral infection.

We theoretically investigate the electromagnetic properties of the multilayer graphene-dielectric composite materials based on the effective medium theory. It is found that the structure exhibits hyperbolic isofrequency wavevector dispersions at THz and far-infrared frequencies, hence thereby realizing the effective graphene-based hyperbolic metamaterials (HMM). The frequncy band of the hyperbolic dispersion can be tuned by changing the Fermi energy of graphene sheet, the thickness of the dielectric layer and the layer number of graphene sheets. Because of the hyperbolic dispersion, graphene-based HMM possesses a negative energy refraction and positive phase refraction for oblique incidence at far below the critical frequency. The highly confined bulk polariton modes are also supported. Based on the attenuated total reflection configuration, the excitation of the bulk polariton mode is studied, in addition, such properties used in the tunable optical reflection modulation are also explored.

We investigate theoretically the electromagnetic propagation properties of graphene plasmons in a comb-like dielectric-graphene-dielectric (DGD) waveguide. The effective index of surface plasmon mode supported by the waveguide is analysed numerically, and it is found that the effective refractive index increases with the refractive index of the dielectric and decreases with Fermi energy of the graphene sheet. For a comb-like DGD waveguide with a finite branch length, a subwavelength plasmon filter can be formed by Fabry-Perot resonance caused by the reflection of the guided mode at the branch. The central frequencies of the gaps can be changed by varying the length of the branch, Fermi energy, the refractive index of the dielectric and the layer number of graphene sheets. The analytic and simulated result reveals that a novel nanometric plasmonic filter in such a comb-shaped waveguide can be realized with ultracompact size in a length of a few hundred nanometers in the mid-infrared range. We find that the frequencies of the stopband increase with Fermi energy and the layer number of graphene sheets, while will they decrease nonlinearly with the length of the branch and the refractive index of the dielectric. In addition, the width of the gap can be increased with the number of comb branches. Such electromagnetic properties could be utilized to develop ultracompact photonic filters for high integration.

The resonance properties of surface plasmon in the AMM/dielectric/AMM waveguide are theoretically studied by using the finite-difference time-domain technique, where the claddings are anisotropic metamaterial (AMM) . From the dispersion relation, it is found that the AMM/dielectric/AMM waveguide supports TE polarized surface plasmon if AMM is always-cutoff with negative permeability. The wavelength of the surface plasmon becomes shorter when both the thickness of the dielectric core and the magnetic plasma frequency of AMM decrease. For an AMM/dielectric/AMM waveguide with a finite length, a subwavelength plasmon microcavity can be formed by Fabry-Perot resonance caused by the reflection of the guided mode at the entrance and the exit surfaces. At the resonant frequency, the electric field is maximized in the center, the magnetic field is maximized at the dielectric core entrance and exit, and the electromagnetic energy is strongly concentrated around the dielectric core. Such electromagnetic properties will have potential applications in the tunable subwavelength microcavity with strongly localized field and in the cavity quantum electrodynamics.

The electromagnetic tunneling properties of the sandwich structure with single negative material/positive index material (single negative material)/ single negative material are experimentally investigated based on the theoretical analysis. The tunneling properties come from the resonance coupling between the incident plane wave and the surface and bulk polaritons. First, the surface or bulk polariton dispersion relations under zero incident condition are discussed and calculated. It is found that the positive index material sandwiched by single negative material possesses bulk polaritons, the resonance frequency of polariton decreases with the thickness of the central layer increasing. The sandwhic structures composed of different single negative materials possess double surface polaritons, and the two surface polaritons degenerate with the thickness of the central single negative material layer. Subsequently, the tunneling properties of the sandwich structures are measured, which are consistent well with the simulation and theoretical analyses. The two structures both possess tunable tunneling modes, their properties have potential applications in designing tunable single or multiple-channeled filters.