A band-pass frequency selective surface with polarization rotation

A band-pass frequency selective surface(FSS) with polarization rotation property is proposed. The proposed polarization rotating FSS(PR-FSS) is a two-dimensional periodic structure, its unit cell is an antenna-filter-antenna(AFA) module,and the polarization directions of the upper and lower antennas in each AFA module are orthogonal to each other, so the PR-FSS can achieve frequency selection and 90 degrees polarization rotation at the same time. The numerical simulation demonstrate that the anticipated frequency selection and polarization rotation are realized by the PR-FSS in the frequency band from 8.84 GHz to 10.30 GHz with a relative bandwidth of 15.26%, and the maximum insertion loss in the pass band is only 0.17 d B. Finally, one effective experiment validation is carried out, a reasonable agreement is observed between the experimental and simulated results except for a slight deviation caused by fabrication error and measurement tolerance.

An ultra-wideband 2-bit coding metasurface using Pancharatnam–Berry phase for radar cross-section reduction

An ultra-wideband 2-bit coding metasurface is designed for radar cross-section(RCS) reduction. The design process is presented in detail, in which a polarization conversion metasurface(PCM) is first proposed. The proposed PCM can realize ultra-wideband circular polarization(CP) maintaining reflection. Moreover, Pancharatnam–Berry(PB) phase will be generated in the co-polarized reflection coefficient by rotating the metallic patches in its unit cells. Thus, based on the PCM, the four coding elements of a 2-bit coding metasurface are constructed using PB phase, and an ultra-wideband PB 2-bit coding metasurface is proposed according to an appropriate coding sequence. The simulated and experimental results show that the coding metasurface has obvious advantages of wideband and polarization-insensitivity. Compared to a metallic plate of the same size, it can achieve more than 10 dB RCS reduction in the frequency band from 9.8 GHz to 42.6 GHz with a relative bandwidth of 125.2% under normal incidence with arbitrary polarizations.

Ultra-wideband linear-to-circular polarization conversion metasurface

An ultra-wideband and high-efficiency reflective linear-to-circular polarization conversion metasurface is proposed. The proposed metasurface is composed of a square array of a corner-truncated square patch printed on grounded dielectric substrate and covered with a dielectric layer, which is an orthotropic anisotropic structure with a pair of mutually perpendicular symmetric axes u and v along the directions with the tilt angles of ±45° with respect to the vertical y axis. When the u- and v-polarized waves are incident on the proposed metasurface, the phase difference between the two reflection coefficients is close to –90° in an ultra-wide frequency band, so it can realize high-efficiency and ultra-wideband LTC polarization conversion under both x- and y-polarized incidences in this band. The proposed polarization conversion metasurface is simulated and measured. Both the simulated and measured results show that the axial ratio (AR) of the reflected wave is kept below 3 dB in the ultra-wide frequency band of 5.87 GHz–21.13 GHz, which is corresponding to a relative bandwidth of 113%;moreover, the polarization conversion rate (PCR) can be kept larger than 99% in a frequency range of 8.08 GHz–20.92 GHz.

Midgut immune responses induced by bacterial infection in the silkworm, Bombyx mori

Insect gut epithelial cells produce reactive oxygen species （ROS） and antimicrobial peptides （AMPs） to protect hosts from pathogenic microorganisms. In this study, we evaluate the pathogenicity of Pseudomonas aeruginosa and Bacillus bombysepticus in the silkworm, Bombyx mori. Survival curves show that B. bombysepticus is deadly when larval silkworms are infected orally. Bacterial infection caused intestinal hydrogen peroxide （H202） and nitric oxide （NO） levels to increase significantly by 8 and 16 h post-infection （hpi）, respectively. Real-time quantitative polymerase chain reaction （qPCR） analysis shows that the transcription levels of dual oxidase （Duox） and catalase （CAT） are highly up-regulated by P. aeruginosa infection at 8 hpi. P. aeruginosa infection induced nitric oxide synthase 2 （NOS2） expression at 16 hpi, which contributes to the generation of NO. mRNA levels of AMP genes, specifically Glovorin 2 and Glovorin 3, which obviously increase during the eady infection stage. These results indicate that invading bacteria ele.vate intestinal ROS and NO levels and induce AMP gene transcription, which contributes to intestinal immune defense.