A new concept of the coding phase gradient metasurface (CPGM) is proposed, which is constructed using the phase gradient metasurface as the coding elements. Different from the previous coding metasurface (CM), both the coding sequences and gradient phases in the coding elements are designed to manipulate the electromagnetic (EM) wave for the CPGMs, and thus the manipulation will be more flexible. As an example, wide-band, wide-angle CPGMs with zero and non-zero phase gradient based on Pancharatnam-Berry (PB) phase are achieved using the co-polarization reflection unit cells under circularly polarized (CP) wave incidence. Both theoretically calculated and numerically simulated scattering patterns of the designed CPGMs demonstrate the expected manipulations. Additionally, two kinds of random CPGMs with different phase gradients are designed for radar cross section (RCS) reduction, and the measured RCS reveals a good accordance with the simulation.
The aim of this study was to investigate the effects of glutamine on the histomorphology of the liver, oxidative stress and nuclear factor-κB (NF-κB) expression in the development of nonalcoholic fatty liver disease (NAFLD). NAFLD was induced in rats by a high-fat diet, and rats in the treatment group were subjected to oral administration of glutamine (1 g/kg/day). Rats from the treatment, model and normal control groups were assessed after 8 and 12 weeks (n=6 per group at each time-point). The levels of glutathione (GSH), malondialdehyde (MDA) and tumor necrosis factor-α (TNF-α) in the liver, and the liver histopathology and NF-κB protein 65 (p65) expression in the liver were assessed. Compared with the control group under the same experimental period, the MDA and TNF-α levels in the liver, the hepatic steatosis and the hepatic expression of NF-κB p65 were significantly higher in the model and the treatment groups (P<0.05), while the GSH levels in the liver were significantly lower (P<0.05). These indices improved significantly in the treatment group compared with the model group (P<0.05). In conclusion, glutamine reduces the degree of oxidative stress in the liver, inhibits NF-κB p65 expression and improves hepatic steatosis. Glutamine has a certain protective effect in NAFLD.
A two-dimensional (2D) coding phase gradient metasurface (CPGM) is proposed for radar cross section (RCS) reduction in this work. The 2D phase gradient super cell is employed to serve as the coding element. The primary pattern of the coding element will be modulated by the designed 2D phase gradient. Thus, a more flexible method of scattering manipulation will be achieved by both the 2D phase gradient and coding sequences. The specific scattering patterns of the 2D CPGM under the modulation of phase gradient and coding sequence were analyzed. A controllable backward diffusion scattering coding phase gradient metasurface was realized based on Pancharatnam–Berry phase by modulating both the phase gradient and coding sequence. Both simulated and measured results demonstrate its excellent performance on RCS reduction.
An amplitude-adjustable metasurface has been proposed to suppress the side-lobe level over an extra-wide frequency band. A polarization-selective unit cell is designed to constitute the metasurface, which can manipulate the amplitudes of the co-polarization reflection coefficients and cross-polarization transmission coefficients, while the phases remain unchanged. The amplitude of the metasurfaces is discretely Taylor-distributed. For example, two metasurfaces were designed to achieve side-lobe level suppression (SLLS), of reflected and transmitted beams, respectively. The simulations demonstrated that two metasurfaces have good performance on SLLS of reflected/transmitted beams, with approximately −20 dB SLL in a wide frequency region. It is expected that the designed amplitude-adjusted metasurfaces may find potential application in antennas and stealth techniques.
Nowadays, the research of metasurfaces has been developed from singledimensional toward multi-dimensional manipulation of electromagnetic (EM) waves, which greatly boosts the practical application of metasurfaces in both microwave and optics regimes. Currently, the demand for new methods to implement effective manipulation of EM waves in multiple dimensions is ever being increased yet it is still a challenging task. Here, a metasurface-based paradigm is proposed for tailoring both amplitude and phase by isomeric manner in a dichroism level, which reveals a flexible capability of manipulating EM waves within all isotropic, anisotropic and chiral characteristics. Circular dichroism (CD) meta-atoms are implemented via loading lumped resistors into planar chiral resonators. The cross-polarization reflection amplitude of the circularly polarized wave is tailored precisely and continuously from 0 to 1 using the diastereomers of CD meta-atoms, while the phase is independently manipulated by the rotamer counterparts based on Pancharatnam-Berry (PB) phase. By controlling both amplitude and phase profiles of the metasurfaces with subwavelength spatial resolution, high-quality complex amplitude hologram and far-field beam forming are demonstrated. Encouragingly, this approach for achieving simultaneous control of amplitude and phase makes a milestone on multi-dimensional metasurfaces which may find applications in integrated planar EM functional systems.
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