Valve-Actuator-Integrated Reference Electrode for an Ultra-Long-Life Rumen pH Sensor.

We demonstrated a newly developed Ag/AgCl reference electrode- with a valve-actuator for two years or longer rumen pH monitoring. Previous studies on pH sensors reported that the short lifetime of Ag/AgCl reference electrodes is caused by an outflow of internal electrolyte. We introduced a valve-actuator into a liquid junction to reduce the outflow by intermittent measurement. The results indicated that the potential change when switching the liquid junction was less than 0.5 mV and its response time was less than 0.083 s. In the 24-h potential measurement with the valve-actuator-integrated reference electrode (VAIRE), the valve was actuated once every hour, and the standard deviation of the potential was 0.29 mV. The lifetime of the VAIRE was estimated at 2.0 years calculating from an electrolyte outflow, which is significantly longer than that of conventional reference electrodes. A pH sensor using the VAIRE was estimated to operate for 2.0 years with the pH error ≤0.1, which meets the requirement of cows' rumen pH monitoring.

Silver-film subwavelength gratings for polarizers in the terahertz and mid-infrared regions.

Silver is proposed as a useful metal for thin metal-film subwavelength-grating polarizers in both the terahertz and mid-infrared regions. A triangular Ag-film grating for a terahertz-region polarizer fabricated on a resin substrate showed measured TE-wave losses of higher than 45 dB in the frequency range of 0.5-2.2 THz, while TM-wave losses were lower than 0.75 dB in the range of 0.5-3THz. A triangular double Ag-film grating structure on a thin silicon substrate with an anti-reflection layer on its reverse side was fabricated for the polarizer in the mid-infrared region. Measured TE-wave losses were higher than 27 dB in the wavelength range of 16-21 µm, while the minimum TM-wave loss was 3.5 dB at around the wavelength of 19 µm. Silver films are confirmed to be promising candidates for fabricating high-performance polarizers in the terahertz and mid-infrared regions.