Both ammonia-oxidizing bacteria (AOB) and archaea (AOA) might be the key microorganisms in ammonia conversion in ecosystems. However, the depth-related change of AOA and AOB in sediment ecosystem is still not clear. The relative contribution of AOA and AOB to nitrification in wetland sediment remains also unclear. Moreover, information about ammonia-oxidizing microorganisms in high-altitude freshwater wetland is still lacking. The present study investigated the relative abundances and community structures of AOA and AOB in sediments of a high-altitude freshwater wetland in Yunnan Province (China). Variations of the relative abundances and community structures of AOA and AOB were found in the wetland sediments, dependent on both sampling site and sediment depth. The relative abundances of AOA and AOB (0.04-3.84 and 0.01-0.52 %) and the AOA/AOB ratio (0.12-4.65) showed different depth-related change patterns. AOB community size was usually larger than AOA community size. AOB diversity was usually higher than AOA diversity. AOA diversity decreased with the increase of sediment depth, while AOB diversity showed no obvious link with the sediment depth. Pearson's correlation analysis showed that AOA diversity had a positive significant correlation with available phosphorus. Nitrosospira-like sequences, with different compositions, predominated in the wetland sediment AOB communities. This work could provide some new insights toward nitrification in freshwater sediment ecosystems.
This paper proposes a novel implementation of a high frequency rectifier, which is realised using the simplified real frequency technique. The optimum impedances presented at the diode package plane are found from source-pull simulation over a broad frequency range. The implemented broadband rectifiers show good performance in terms of efficiency and bandwidth. Using a HSMS 2820 Schottky diode device, greater than 50 % efficiency has been measured from 1.25 GHz to 2.25 GHz. Furthermore, greater than 60 % efficiency with 14 dB (from 12 dBm to 26 dBm) input power dynamic range is achieved at 1.8 GHz. Peak efficiency of 77 % is obtained at the input power of 23 dBm. The high efficiency over such a large bandwidth is believed to be the best reported to data in open literature at these frequencies.
This paper proposes a novel configuration of the rectifier which is realised using a high impedance inductor. It removes the input matching network concerning the trade-off of the efficiency and bandwidth. The rectifier with better than 40 % efficiency is designed and measured across the frequency band from 40 MHz to 4740 MHz. The peak RF-DC conversion efficiency of 60.3 % is achieved at 1 GHz operating frequency with 23 dBm incident power. In addition, a minimum of 2 V output DC voltage and greater than 40 % efficiency with 5 dB input power dynamic range from 20 dBm to 25 dBm is obtained covering the entire band.