ABSTRACT
In order to solve the problems of present quartz crystal microbalance ( QCM ) measuring instruments, such as high demand for crystal cutting technology and uncomprehensive measurements for crystal parameters, a modified quadrature demodulation-based method was proposed with broadband adaptive response capacity and high frequency resolution. Moreover, it is also capable of measuring both resonant frequencies and dissipation factor D synchronously and continuously. Experimental results at room temperature indicated that the adaptive frequency range was 1-9 MHz while the frequency resolution was less than 1 Hz, measured resonance frequency shifts of crystals in the range scale linearly with the equal thickness increments of poly acrylic acid ( PAA) membrane on the working electrode, and with the volatilization of different solvent factor D is measured continuously and effectively along the time axis. To sum up, compared with traditional ones, this new method has lower material cost and more obtained parameters.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effects of composite grinding dusts on rat respiratory system.</p><p><b>METHODS</b>Rats were administrated with grinding dusts by intratracheal injection. After 2 weeks, the total numbers of cells, the percentage of differential cell, the survival rate of cell, and the activity of lactate dehydrogenase(LDH) and alkaline phosphatase(ALP) in bronchoalveolar lavage fluid were analyzed.</p><p><b>RESULTS</b>Along with increasing concentration of grinding dusts, the total number of cells in lavage also increased, and was more than that in quartz group. Compared with control group, the percentage of neutrophil in lavage of rats treated with grinding dust and quartz significantly increased and meanwhile that of macrophage significantly decreased[PMN: quartz group (33.83 +/- 4.54)%; grinding dusts group (26.50 +/- 3.99)%, (36.00 +/- 3.58)%, (38.00 +/- 2.10)% at 10, 25, 50 mg/ml respectively. Macrophages: quartz group (62.17 +/- 4.54)%; grinding dusts group (70.83 +/- 3.66)%, (60.83 +/- 2.14)%, (58.17 +/- 2.48)%] while those in control group were (2.83 +/- 0.75)%, (95.67 +/- 1.21)% respectively. The cell survival rate in lavage in control group was 80%, but that in grinding dust and TiO2 group significantly decreased(P < 0.01). The activity of LDH and ALP in all rats treated with dusts obviously increased, and there was significant difference compared with control group(P < 0.01 or P < 0.05). Furthermore, there was significant difference between grinding dust group and quartz group, and between grinding dust group and TiO2 group respectively.</p><p><b>CONCLUSION</b>Metal grinding dust is very harmful to rat's lung cells and may cause fibrogenesis in the lungs.</p>