Design, fabrication, and characterization of a single-polarization single-mode flexible hollow waveguide for low loss millimeter wave propagation.

A flexible metallic waveguide with elliptical core that achieves single-polarization single-mode (SPSM) propagation at millimeter wave was designed, fabricated, and characterized. In order to achieve SPSM propagation, optimization of the lengths of major/minor axes of elliptical core was conducted to cut off one of the two orthogonally polarized fundamental modes and all high-order modes. A one-meter long hollow elliptical waveguide (HEW) with major/minor axis length of 1.5/2.7 mm was fabricated. The substrate tube was a flexible elliptical polycarbonate (PC) tube, which was fabricated through glass-draw technique. Silver film was then coated on the inner surface of the tube. Simulation results show that the 1.5/2.7 mm HEW maintains SPSM propagation in the frequency band from 66.5 to 114 GHz. The SPSM operation was experimentally discussed in detail at 100 GHz. The measured loss of 2.58 dB/m and the output polarization ratio of 99.9% was obtained after propagating one meter. Furthermore, the waveguide was robust to bending and twisting. The additional loss was as small as 0.2 dB/m even when the waveguide was coiled into a circle. The potential application of HEWs as polarizers was demonstrated by using a 10 cm long waveguide for polarization detection and extinction ratio of 22.3 dB was achieved at 100 GHz.

Characterization of Gas Absorption Modules Based on Flexible Mid-Infrared Hollow Waveguides.

A new gas absorption module, the substrate-embedded hollow waveguide (eHWG) model, is proposed. It consists of a substrate with a curved channel and a hollow waveguide. The hollow waveguide is curved into the channel and works as a gas absorption cell as well as a transmission medium for mid-infrared light. Owing to the low loss property of the hollow waveguide, the signal-to-noise ratio (SNR) was improved for the sensing system. A polycarbonate (PC) base tube was used to obtain flexibility in the fabrication of the hollow waveguide. A silver (Ag) layer and a silver iodide (AgI) layer were inner-coated to ensure a low loss property at the fingerprint wavelength of methane gas. A sensing system was established using a Fourier transform infrared spectrometer (FTIR), an external detector, and an eHWG. Experimental investigations were carried on the sensing performance of eHWGs with various channel shapes. Comparison studies were made on eHWGs embedded with Ag-coated or Ag- and AgI-coated hollow waveguides. The Ag- and AgI-coated hollow waveguides with inner diameters of 0.7, 1.4, and 2.0 mm were used in the eHWGs. The large bore waveguide had low loss but high bending additional loss. The large bore waveguide had a low detection limit due to high coupling efficiency with the light source. A limit of detection (LOD) as low as 2.7 ppm was attained for the system using the eHWG with the long and large bore waveguide.

PD-1/PD-L1 interaction up-regulates MDR1/P-gp expression in breast cancer cells via PI3K/AKT and MAPK/ERK pathways.

Programmed cell death ligand 1 (PD-L1) is an immunosuppressive molecule expressed on tumor cells. By interacting with programmed cell death-1 (PD-1) on T cells, it inhibits immune responses. Because PD-L1 expression on cancer cells increases their chemoresistance, we investigated the correlation between PD-L1 and multidrug resistance 1/ P-glycoprotein (MDR1/P-gp) expression in breast cancer cells. Analysis of breast cancer tissues using tissue microarrays revealed a significant correlation between PD-L1 and MDR1/P-gp protein levels. Increased expression of PD-L1 was associated with lymph node metastasis and histological tumor grade. In addition, interaction of PD-L1 with PD-1 induced phosphorylation of AKT and ERK, resulting in the activation of PI3K/AKT and MAPK/ERK pathways and increased MDR1/P-gp expression in breast cancer cells. The PD-1/PD-L1 interaction also increased survival of breast cancer cells incubated with doxorubicin. These findings suggest that the PD-1/PD-L1 inhibition may increase chemotherapy efficacy by inhibiting the MDR1/P-gp expression in breast cancer cells.