RESUMO
ObjectiveA general experiment platform of electrical impedance tomography(EIT) based on field programmable gate array(FPGA) was designed to meet the requirements of EIT digital measurement.A digital current source and the research on digital demodulation method was completed.MethodsFor construction of the experiment platform,DDS module,D/A and A/D interface module,digital demodulation module and RS-232 communication module were all integrated in one FPGA chip.ResultsThe source can provide multi-frequency excitation signals of 2 mA in the range of 6.1-390.6 kHz.The output impedance of the source was higher than 190 kΩ.Both the real and the virtual information of measured impedance could be extracted.ConclusionMeasurements based on bioimpedance-equivalent circuit model verified the validity of the platform.The research results of this paper provides a foundation for the construction of a practical EIT system.
RESUMO
This paper reported that the activation of oncogenes in human fetal esopha geal epithelium treated by alternariol (AOH). It was found that NIH/3T3 cells were transformed via transfeetion of DNA extracted from human fetal esophageal epithelium which was cultured and treated by 10?g/ml AOH in a short term in vitro. The efficiency of primary loci was 0.17 focus per ?g of DNA. In the secondary transfection, the efficiency was 0.58 focus per ?g of DNA (P