Violin bridge mobility analysis under in-plane excitation.

The vibration of a violin bridge is a dynamic contact vibration with two interfaces: strings-bridge, and bridge feet-top plate. In this paper, the mobility of an isolated bridge under in-plane excitation is explored using finite element modeling based on the contact vibration model. Numerical results show that the dynamic contact stiffness in the two contact interfaces has a great impact on the bridge mobility. A main resonance peak is observed in the frequency range of 2-3 kHz in the frequency response of the isolated bridge when the contact stiffness is smaller than a critical threshold. The main resonance peak frequency is affected by the contact stiffness as well. In order to verify the numerical findings, a novel experimental system is then designed on the basis of a piezoelectric dynamometer for bridge mobility analysis. Experimental results confirm the impact of the dynamic contact stiffness on the bridge mobility.

High-purity DNA extraction from animal tissue using picking in the TRIzol-based method.

TRIzol is used for the extraction of RNA, DNA and proteins from tissues or cells. Here, we present a simple picking method to extract DNA from tissues using TRIzol. Spectrophotometric analysis showed that the 260/280 and 260/230 nm optical density ratio of the picking method's DNA is ideal and better than that obtained by the classic TRIzol method. Gel electrophoresis showed that there was no RNA contamination, and the DNA had not degraded. DNA extracted by the picking method had the same performance in restriction enzyme digestion and quantitative PCR as that obtained by the traditional method. Viral DNA in the infected tissue was also obtained. This modified method facilitates various molecular biology assays.