RESEARCH ON DOSE MONITORING IN BACKSCATTERING NEUTRON HALL IN CHINA SPALLATION NEUTRON SOURCE.

The back-n project in China Spallation Neutron Source (CSNS) was launched primarily for nuclear data measurements. In the backscattering neutron hall, the neutron and gamma monitors were used for dose monitoring. Because of the dead time problem of monitors, performance of the monitors in such pulsed radiation field needs to be analyzed. In this research, experiments with dose monitors and personal dosemeters were conducted, and simulation by Monte Carlo code FLUKA was performed. Results showed that the values by monitors are smaller, and the larger the dose, the larger the difference. The reasons in term of energy response and dead time have been analyzed, and corrections were discussed. After corrections, the measured value can agree with the simulation results in the range of about a factor 3. Totally speaking, the values recorded by neutron and gamma monitors can be a reference for radiation safety management in CSNS.

[Quality Assessment of Euglycemic Glucose Clamp Test].

OBJECTIVE: To explorethe quality of euglycemic glucose clamptest performed in the West China Hospital from 2014 to 2017 and to evaluate whether the quality control indexes are suitable for the quality assessment of the clamp test. METHODS: The data collected from 80 euglycemic glucose clamp tests performed between 2014 and2017 were divided into 4 groups according to the coefficient of variation of the blood glucose concentrations (CVBG): group A (CVBG≤4.5%), group B (4.5% < CVBG≤5.0%), group C (5.0% < CVBG≤5.5%) and group D(CVBG > 5.5%).The differences in percentage of glucose excursion from target range (GEFTR), the duration of GEFTR, the area under curve (AUC) of GEFTR, the mean value of excursion from target glucose (GEFT) and the AUC of GEFT were calculated and compared. RESULTS: In group A, the mean value of CVBG was 3.75%. In group B, the mean value of CVBG was 4.76%. In group C, the mean value of CVBG was 5.28%. The median value of CVBG in group D was 6.07%. The percentage of GEFTR, the duration of GEFTR, the AUC of GEFTR, the mean value of GEFT and the AUC of GEFT in group A were all less than those of other groups (P < 0.05).For the same indexes, there were no significant differences between group B and C, while they were higher in group D compared with the other three groups. CVBG was positively correlated with other quality control indexes (correlation coefficient r was 0.770-0.805). Based on the cut-off point 5% of CVBG, the cut-off points of the percentage of GEFTR, the duration of GEFTR, the AUC of GEFTR, the mean value of GEFT and the AUC of GEFT were 5.8%, 14.6 min, 22.82 mg/dL×min, 3.23 mg/dL, 216.25 mg/dL×min/h respectively, with the sensitivity range from 79.3% to 100% and the specificity range from 74.5% to 89.7%.Combined with these indexes, 8.11% of euglycemic clamps were found to havepoor quality in group A, while 66.67% of euglycemic clamps showed acceptable quality in group C. CONCLUSIONS: The investigators should provide an estimation of the quality of the clamps when reporting the results of the insulin analogues' PK/PD characteristics using euglycemic clamps. CVBG less than 4.5% indicates a good quality, and the above-mentioned quality control indexes especially the AUC of GEFT(cut-off point: 216.25 mg·/dL×min/h) should be evaluated when CVBG is more than 4.5%.False high quality and false low quality euglycemic clamps will be detected and a more precise estimation of quality assessment should be made by the combination of these indexes.

[Estimation of PM2.5 over eastern China from MODIS aerosol optical depth using the back propagation neural network].

With the fast economic development in China in recent years, air pollutions are becoming increasingly serious. It is, therefore, imperative to develop new technology to solve this issue. Due to the wide spatial coverage of satellite remote sensing, along with the relatively lower cost compared to ground-based in situ aerosol measurements, satellite retrieved aerosol optical depth (AOD) is widely recognized as a good surrogate of surface PM2.5 concentrations. In this study, two years (2007-2008) of AOD data from moderate resolution imaging spectroradiometer (MODIS) onboard Terra at five observational sites of China (Benxi, Zhengzhou, Lushan, Nanning, Guilin), combined with five meteorological factors such as wind speed, wind direction, temperature humidity and planetary boundary height, were used as important input to establish the Back Propagation (BP) neural networks model, which was applied to estimate PM2.5. Afterwards, the model estimated PM2.5 was validated by in situ PM2.5 measurements from the five sites. Specially, scatter analysis showed that the linear correlation coefficient (R) between ground PM2.5 observation and model estimated PM2.5 at Lushan was the highest (R = 0.6), whereas the R values at the four other sites were lower, ranging from 0.43 to 0.49. Time series validations were performed as well, indicating that the R value significantly varied from day to day. However, the R value could be significantly improved by fitting the five-day moving average ground observation values against the model estimated PM2.5 data. Also, the R value at Lushan was the highest (R = 0.83), suggesting that MODIS AOD can be used to monitor PM2.5 by the BP networks model developed in this study.

[Using log-binomial model for estimating the prevalence ratio].

To estimate the prevalence ratios, using a log-binomial model with or without continuous covariates. Prevalence ratios for individuals' attitude towards smoking-ban legislation associated with smoking status, estimated by using a log-binomial model were compared with odds ratios estimated by logistic regression model. In the log-binomial modeling, maximum likelihood method was used when there were no continuous covariates and COPY approach was used if the model did not converge, for example due to the existence of continuous covariates. We examined the association between individuals' attitude towards smoking-ban legislation and smoking status in men and women. Prevalence ratio and odds ratio estimation provided similar results for the association in women since smoking was not common. In men however, the odds ratio estimates were markedly larger than the prevalence ratios due to a higher prevalence of outcome. The log-binomial model did not converge when age was included as a continuous covariate and COPY method was used to deal with the situation. All analysis was performed by SAS. Prevalence ratio seemed to better measure the association than odds ratio when prevalence is high. SAS programs were provided to calculate the prevalence ratios with or without continuous covariates in the log-binomial regression analysis.

[Birth weight distribution among premature infants and related social factors].

OBJECTIVE: To understand the distribution of birth weight among premature infants and the associated social factors. METHODS: The study population consisted of 97 537 women who delivered singleton live birth of 20 to 41 gestational weeks in 4 counties/cities, Jiangsu and Zhejiang provinces, China from 1995 to 2000. Chi-square test was employed to test the difference of proportions between respective groups. One- way ANOVA was used to test the differences regarding the mean of gestational weeks at the first prenatal visit and the mean of prenatal visits between the two groups. Multivariate logistic regression was conducted to examine the factors associated with premature birth. RESULTS: Women aged 35 years had higher (8.8%) premature incidence than those aged less than 24 years (5.6%), 25 - 29 years (4.6%), or 30 - 34 years (4.5%, P < 0.001). Women with height less than 149 cm had higher (6.8%) premature incidence than those with height taller than 150 cm (5.0%). Women whose BMI were at least 28 and 24 - 28 had higher (5.5%, 5.5%) premature incidences than those whose BMI were 18.5 - 24.0 (5.0%), < 18.5 (4.6%, P < 0.001). The incidence of premature birth was 6.0% among women without previous pregnancy, higher than that among those women with 4 times of pregnancies (5.7%), 2 times of pregnancies (4.3%), and 3 times of pregnancies (4.0%). Parous women with at least two deliveries had higher (9.3%) premature incidence than the primiparous women (5.2%) and whose women with only one delivery (4.5%, P < 0.001). Women who received early prenatal care had lower 4.7% premature incidence than those who did not receive the service (6.1%). The mean times of prenatal visits among women with premature births was 8.53, less than that of those with full term delivery (10.97). Women with less than four times of prenatal visit had higher (18.9%) premature incidence than those with at least five prenatal visits (4.9%). Multivariate logistic regression showed that premature delivery risk was associated with age, height, BMI, gravidity, parity, early prenatal care, the mean of gestational weeks at first prenatal visit and the mean number of prenatal visits etc. CONCLUSION: Premature delivery risk was associated with factors as age, height, BMI, gravidity, parity, early prenatal care, the mean of gestational weeks at first prenatal visit, the mean number of prenatal visits etc.

[The extent and relative changes of equities in utilization of prenatal care among women in some areas of China].

OBJECTIVE: To assess the extent and relative changes of the equities in prenatal care utilization among women with different educational attainment in some areas of China. METHODS: Data were collected in 13 counties/cities covered by Perinatal Health Care Surveillance System established by Institute of Reproductive and Child Health, Peking University. The study population consisted of 103 704 women who delivered single live births in 1994 and 2000. Chi-square and multiple logistic regression were employed to compare the systematic management rates and relative risks. Concentration index was used to assess the relative changes of equities in prenatal care utilization. SPSS 11.5 and Microsoft Excel 2003 were used for analysis. RESULTS: The total systematic management rate was 22.1% in 1994 and 57.4% in 2000. The concentration index was -0.046 in 1994 and 0.066 in 2000. In northern areas, the concentration index increased from 0.015 in 1994 to 0.295 in 2000, while it increased from -0.015 in 1994 to 0.062 in 2000 in southern areas. In rural areas, the concentration index increased from 0.002 in 1994 to 0.026 in 2000, while it decreased from 0.042 in 1994 to 0.019 in 2000 in urban areas. CONCLUSION: Inequities in prenatal care utilization in 2000 become more obvious than in 1994, especially in northern areas. More attention should be paid to solve the inequities.