Reflection phase modification by metamaterial interface: an understanding of design criteria for ultrathin multispectral absorber.

We introduce a metasurface to modify the reflection phase for multispectral microwave absorbers. General quantitive design criteria are proposed by carrying out field analysis, so that design of multispectral microwave absorber can be effectively realized. Optimal design process is discussed to develop an understanding of the absorbing mechanism. Experiment results show that the absorber having only 0.015 times the wavelength at the center frequency can simultaneously achieve high absorption in the microwave, visible light and near-infrared light bands. Multispectral absorption comes with added features of flexibility, ultrathin thickness and a light weight that make it a powerful candidate in advanced stealth application.

Ultracompact Implantable Design With Integrated Wireless Power Transfer and RF Transmission Capabilities.

This paper presents an ultracompact design of biomedical implantable devices with integrated wireless power transfer (WPT) and RF transmission capabilities for implantable medical applications. By reusing the spiral coil in an implantable device, both RF transmission and WPT are realized without the performance degradation of both functions in ultracompact size. The complete theory of WPT based on magnetic resonant coupling is discussed and the design methodology of an integrated structure is presented in detail, which can guide the design effectively. A system with an external power transmitter and implantable structure is fabricated to validate the proposed approach. The experimental results show that the implantable structure can receive power wirelessly at 39.86 MHz with power transfer efficiency of 47.2% and can also simultaneously radiate at 2.45 GHz with an impedance bandwidth of 10.8% and a gain of -15.71 dBi in the desired direction. Furthermore, sensitivity analyses are carried out with the help of experiment and simulation. The results reveal that the system has strong tolerance to the nonideal conditions. Additionally, the specific absorption rate distribution is evaluated in the light of strict IEEE standards. The results reveal that the implantable structure can receive up to 115 mW power from an external transmitter and radiate 6.4 dB·m of power safely.

Theoretical Analysis and Design of Ultrathin Broadband Optically Transparent Microwave Metamaterial Absorbers.

Optically Transparent Microwave Metamaterial Absorber (OTMMA) is of significant use in both civil and military field. In this paper, equivalent circuit model is adopted as springboard to navigate the design of OTMMA. The physical model and absorption mechanisms of ideal lightweight ultrathin OTMMA are comprehensively researched. Both the theoretical value of equivalent resistance and the quantitative relation between the equivalent inductance and equivalent capacitance are derived for design. Frequency-dependent characteristics of theoretical equivalent resistance are also investigated. Based on these theoretical works, an effective and controllable design approach is proposed. To validate the approach, a wideband OTMMA is designed, fabricated, analyzed and tested. The results reveal that high absorption more than 90% can be achieved in the whole 6~18 GHz band. The fabricated OTMMA also has an optical transparency up to 78% at 600 nm and is much thinner and lighter than its counterparts.

Entecavir therapy in a hepatitis B-related decompensated cirrhotic patient.

A 58-year-old Arab-American male with HBeAg-negative chronic hepatitis B (HBV), presented with decompensated cirrhosis and a high HBV DNA level. He responded to entecavir with a significant reduction in serum HBV DNA level after 15 weeks of therapy with entecavir. However, he developed a progressive rise in prothrombin time/international normalized ratio (PT/INR) and bilirubin and underwent liver transplantation after receiving 22 weeks of entecavir therapy. Furthermore, with the continued use of combination entecavir and hepatitis B immunoglobulins (HBIG), he showed improvement in his clinical status with a nondetectable serum HBV DNA level 12 weeks after transplantation. He continued to maintain nondetectable serum HBV DNA 2 years following transplantation. To the best of our knowledge, this is the first reported case of a patient with decompensated chronic HBV who responded to entecavir both before and after transplantation without showing any evidence of recurrent HBV. Larger clinical trials are recommended to compare both short-term and long-term efficacy using entecavir among nucleoside-naïve decompensated chronic HBV patients before and after liver transplantation.