Design of a Novel Medical Acoustic Sensor Based on MEMS Bionic Fish Ear Structure.

High-performance medical acoustic sensors are essential in medical equipment and diagnosis. Commercially available medical acoustic sensors are capacitive and piezoelectric types. When they are used to detect heart sound signals, there is attenuation and distortion due to the sound transmission between different media. This paper proposes a new bionic acoustic sensor based on the fish ear structure. Through theoretical analysis and finite element simulation, the optimal parameters of the sensitive structure are determined. The sensor is fabricated using microelectromechanical systems (MEMS) technology, and is encapsulated in castor oil, which has an acoustic impedance close to the human body. An electroacoustic test platform is built to test the performance of the sensor. The results showed that the MEMS bionic sensor operated with a bandwidth of 20-2k Hz. Its linearity and frequency responses were better than the electret microphone. In addition, the sensor was tested for heart sound collection application to verify its effectiveness. The proposed sensor can be effectively used in clinical auscultation and has a high SNR.

Responses of heavy metals mobility and resistant bacteria to adding time of activated carbon during chicken manure composting.

With the wide application of compost in agriculture, heavy metals (HMs) continue to accumulate in the soil environment, which poses a great threat to the health of the soil environment. Therefore, it is critical for effectively reduce the mobility of HMs. In this study, the influence of activated carbon (AC) addition time on mobility of HMs (Cu, Zn and Pb) and HMs resistant bacteria structure were evaluated during chicken manure composting. The result showed that the addition of AC in the thermophilic period could effectively reduce the mobility of HMs. Subsequently, high-throughput sequencing results showed that the dominant phyla were Proteobacteria, Firmicutes, Actinbacteria, Deinococcus-Thermus, Chloroflexi, Gemmatimonadetes and Bacteroidetes within the sample, which were ubiquitous and abundant in composting. The Redundancy analysis (RDA) results indicated that the mobility of HMs (Cu, Zn and Pb) by superior bacteria fate varied in AC amendment composting. Ultimately, a regulation method is proposed to influence the mobility of HMs by regulating the bacteria community in the AC compost. Our current studies suggest that the addition of AC during compost preparation (thermophilic period) is an effective strategy in regulating the mobility (bioavailability) of HMs, thereby significantly reducing environmental pollution problems.