We theoretically and experimentally proposed a new structure of ultra-wideband and thin perfect metamaterial absorber loaded with lumped resistances. The thin absorber was composed of four dielectric layers, the metallic double split ring resonators (MDSRR) microstructures and a set of lumped resistors. The mechanism of the ultra-wideband absorption was analyzed and parametric study was also carried out to achieve ultra-wideband operation. The features of ultra-wideband, polarization-insensitivity, and angle-immune absorption were systematically characterized by the angular absorption spectrum, the near electric-field, the surface current distributions and dielectric and ohmic losses. Numerical results show that the proposed metamaterial absorber achieved perfect absorption with absorptivity larger than 80% at the normal incidences within 4.52~25.42 GHz (an absolute bandwidth of 20.9GHz), corresponding to a fractional bandwidth of 139.6%. For verification, a thin metamaterial absorber was implemented using the common printed circuit board method and then measured in a microwave anechoic chamber. Numerical and experimental results agreed well with each other and verified the desired polarization-insensitive ultra-wideband perfect absorption.

We proposed an ultra-broadband reflective metamaterial with controlling the scattering electromagnetic fields based on a polarization convertor. The unit cell of the polarization convertor was composed of a three layers substrate with double metallic split-rings structure and a metal ground plane. The proposed polarization convertor and that with rotation angle of 90 deg had been employed as the “0” and “1” elements to design the digital reflective metamaterial. The numbers of the “0” and “1” elements were chosen based on the information entropy theory. Then, the optimized combinational format was selected by genetic optimization algorithm. The scattering electromagnetic fields had been manipulated due to destructive interference, which was attributed to the control of phase and amplitude by the proposed polarization convertor. Simulated and experimental results indicated that the reflective metamaterial exhibited significantly RCS reduction in an ultra-broad frequency band for both normal and oblique incidences.

In this study, gold-nanoparticle-crosslinked Pluronic micelles were synthesized and used as a carrier for paclitaxel (PTX). The resultant PTX-loaded gold-nanoparticle-crosslinked Pluronic micelles were about 69 nm in diameter. Physical stability and in vivo pharmacokinetic studies revealed that these micelles were more stable as compared to the non-cross-linked controls. Fluorescence microscopy and flow cytometry analyses showed that PTX-loaded cross-linked micelles had excellent cellular uptake ability by human glioma U87 cells. The cleavage of disulfide bridge linkages under glutathione stimulus resulted in destruction of micelles and induced rapid drug release. In vitro cytotoxicity studies revealed that these cross-linked micelles exhibited high anti-cancer activity against glutathione monoester pretreated U87 cells compared to non-pretreated cells. Cytoarchitecture studies demonstrated a similar cytoskeleton pattern before and after cross-linked micelles loaded into bone marrow derived macrophages. In vivo fresh frozen sections showed that cross-linked micelles were preferably accumulated in spleen and liver. These results indicated that gold-nanoparticle-crosslinked Pluronic micelles can be used as potential anti-cancer drug carriers for intelligent drug delivery.

No abstract