ABSTRACT
@#<b>Objective</b> To correct the counting loss of <sup>37</sup>Ar below the activity threshold during the measurement of the absolute activity of the inert radioactive gas <sup>37</sup>Ar using the proportional counter filled with gas. <b>Methods</b> Monte Carlo simulation with Geant4 was performed to establish a proportional counter model and output the energy deposition spectrum of <sup>37</sup>Ar, which were used to simulate and analyze the causes and correction of counting loss. <b>Results</b> The photon detection efficiency was only 38.7% at 60 kPa. The counting loss was mainly caused by the wall effect produced by the photons, which could be reduced by increasing the gas pressure and corrected by extrapolation. The influence of wall effect at 100 kPa was 4.4%, and the deviation between simulation and experiment was < 0.6%. <b>Conclusion</b> A factor could be calculated by Geant4 simulation for the correction of counting loss, thus achieving the accurate measurement of <sup>37</sup>Ar activity by proportional counter.
ABSTRACT
Objective@#To prove the validity and accuracy of the digitizer instead of the conventional electronics plug-in for radionuclide measurement.@*Methods@# Based on a large-area flow-gas multi-wire proportional counter for 2πα and 2πβ surface particle emission rate measurement, the DT5730 digital waveform sampler developed by CAEN was used for waveform signal acquisition, amplitude analysis, and data processing of the α-plane source 241Am and the β-plane source nuclides 14C, 36Cl, and 90Sr-90Y of different energies.@*Results@#The deviations between the α and β surface particle emission rate results obtained after dead time and background corrections and the measurements obtained based on the plug-in calibrator were all within 0.6%, within the uncertainty range, under consistent experimental conditions such as electronics threshold and high pressure.@*Conclusion@#The digitizer is an effective alternative to conventional electronics plug-ins for α and β signal acquisition and processing and the accurate measurement of α and β emission rates.
ABSTRACT
OBJECTIVE: To investigate the incidence and influencing factors of hypertension among civil aviation pilots. METHODS: A total of 1 169 civil aviation pilots in Northern China were selected into the study by the method of convenient sampling. Physical examination, laboratory test and questionnaire survey were conducted. RESULTS: The prevalence of hypertension in Northern China was 4.7%(55/1 169). Multivariate regression analysis showed that the relative risk factors ranking from high to low were, age over 30 years [odds ratio(OR)=6.81, 95% confidence interval(95%CI) 3.57-12.98)], total flight hours over 1 000 hours(OR=4.24, 95%CI 2.14-8.41), flight hours over 500 hours in the past year(OR=2.91, 95%CI 1.57-5.40), obesity(OR=2.50, 95%CI 1.08-5.81), fasting blood glucose(OR=2.24, 95%CI 1.21-4.13), and frequent long-distance flight(OR=2.38, 95%CI 1.24-4.58). These factors were the risk factors of hypertension in civil aviation pilots(P<0.05). CONCLUSION: Age, total flight hours, flight hours in the past year, obesity, fasting blood glucose, frequent long-distance flight are related to the prevalence of hypertension in civil aviation pilots.