Impact toughness and dynamic constitutive model of geopolymer concrete after water saturation.

The dynamic compression test of geopolymer concrete (GC) before and after water saturation was carried out by the split Hopkinson pressure bar (SHPB). And the effects of water saturation and strain rate on impact toughness of GC were studied. Based on Weibull statistical damage distribution theory, the dynamic constitutive model of GC after water saturation was constructed. The results show that the dynamic peak strain and specific energy absorption of GC have strain rate strengthening effect before or after water saturation. The impact toughness of GC decreases after water saturation. The size distribution of GC fragments has fractal characteristics, and the fractal dimension of GC fragments after water saturation is smaller than that before water saturation. The dynamic constitutive model based on Weibull statistical damage distribution theory can accurately describe the impact mechanical behavior of GC after water saturation, and the model fitting curves are in good agreement with the experimental stress-strain curves.

Using the Haddon matrix to explore medical response strategies for terrorist subway bombings.

BACKGROUND: Since the 1970s, terrorist bombings in subways have been frequently occurring worldwide. To cope with this threat and to provide medical response countermeasures, we analyzed the characteristics of subway bombing terrorist attacks and used the Haddon matrix to explore medical response strategies. METHODS: First, we analyzed 111 subway bombings from 1970 to 2017 recorded in the Global Terrorism Database to provide a reference for the strategy exploration. Then, we convened an expert panel to use the Haddon matrix to explore the medical response strategies to subway bombings. RESULTS: In recent decades, at least one bombing attack occurs every 3 years. Summarized by the Haddon matrix, the influencing factors of medical responses to conventional subway bombings include the adequacy of first-aid kits and the medical evacuation equipment, the traffic conditions affecting the evacuation, the continuity and stability of communication, as well as the factors exclusively attributed to dirty bomb attacks in subways, such as ionizing radiation protection capabilities, the structure of the radiation sickness treatment network based on the subway lines, and the disposal of radioactive sewage. These factors form the basis of the strategy discussion. CONCLUSION: Since subway bombings are long-term threats, it is necessary to have proper medical response preparation. Based on the Haddon matrix, we explored the medical response strategies for terrorist subway bombings, especially dirty bomb attacks. Haddon matrix can help policymakers systematically find the most important factors, which makes the preparations of the response more efficient.

Epidemiological characteristics of pulmonary tuberculosis in mainland China from 2004 to 2015: a model-based analysis.

BACKGROUND: We used data released by the government to analyze the epidemiological distribution of pulmonary tuberculosis in mainland China from 2004 to 2015, in order to provide a deeper understanding of trends in the epidemiology of pulmonary tuberculosis in China and a theoretical basis to assess the effectiveness of government interventions and develop more targeted prevention and control strategies. METHODS: A discrete dynamic model was designed based on the epidemiological characteristics of pulmonary tuberculosis and fitted to data published by the government to estimate changes in indicators such as adequate contact rate, prevalence of non-treated pulmonary tuberculosis (abbreviated as prevalence), and infection rate. Finally, we performed sensitivity analyses of the effects of parameters on the population infection rate. RESULTS: The epidemiological features of pulmonary tuberculosis in China include a pattern of seasonal fluctuations, with the highest rates of infection in autumn and winter. The adequate contact rate has increased slightly from an average of 0.12/month in 2010 to an average of 0.21/month in 2015. The prevalence in the population has continued to decrease from 3.4% in early 2004 to 1.7% in late 2015. The Mycobacterium tuberculosis (M. tuberculosis) infection rate in the population decreased gradually from 42.3% at the beginning of 2004 to 36.7% at the end of 2015. The actual number of new infections gradually decreased from 1,300,000/year in 2010 to 1,100,000/year in 2015. The actual number of new patients each year has been relatively stable since 2010 and remains at approximately 2,600,000/year. CONCLUSIONS: The population prevalence and the M. tuberculosis infection rate have decreased year by year since 2004, indicating that the tuberculosis epidemic in China has been effectively controlled. However, pulmonary tuberculosis has become increasingly contagious since 2010. China should focus on the prevention and control of pulmonary tuberculosis during autumn and winter.

The temporal distribution of new H7N9 avian influenza infections based on laboratory-confirmed cases in Mainland China, 2013-2017.

In this study, estimates of the growth rate of new infections, based on the growth rate of new laboratory-confirmed cases, were used to provide a statistical basis for in-depth research into the epidemiological patterns of H7N9 epidemics. The incubation period, interval from onset to laboratory confirmation, and confirmation time for all laboratory-confirmed cases of H7N9 avian influenza in Mainland China, occurring between January 2013 and June 2017, were used as the statistical data. Stochastic processes theory and maximum likelihood were used to calculate the growth rate of new infections. Time-series analysis was then performed to assess correlations between the time series of new infections and new laboratory-confirmed cases. The rate of new infections showed significant seasonal fluctuation. Laboratory confirmation was delayed by a period of time longer than that of the infection (average delay, 13 days; standard deviation, 6.8 days). At the lags of -7.5 and -15 days, respectively, the time-series of new infections and new confirmed cases were significantly correlated; the cross correlation coefficients (CCFs) were 0.61 and 0.16, respectively. The temporal distribution characteristics of new infections and new laboratory-confirmed cases were similar and strongly correlated.

Predicting and Evaluating the Epidemic Trend of Ebola Virus Disease in the 2014-2015 Outbreak and the Effects of Intervention Measures.

We constructed dynamic Ebola virus disease (EVD) transmission models to predict epidemic trends and evaluate intervention measure efficacy following the 2014 EVD epidemic in West Africa. We estimated the effective vaccination rate for the population, with basic reproduction number (R0) as the intermediate variable. Periodic EVD fluctuation was analyzed by solving a Jacobian matrix of differential equations based on a SIR (susceptible, infective, and removed) model. A comprehensive compartment model was constructed to fit and predict EVD transmission patterns, and to evaluate the effects of control and prevention measures. Effective EVD vaccination rates were estimated to be 42% (31-50%), 45% (42-48%), and 51% (44-56%) among susceptible individuals in Guinea, Liberia and Sierra Leone, respectively. In the absence of control measures, there would be rapid mortality in these three countries, and an EVD epidemic would be likely recur in 2035, and then again 8~9 years later. Oscillation intervals would shorten and outbreak severity would decrease until the periodicity reached ~5.3 years. Measures that reduced the spread of EVD included: early diagnosis, treatment in isolation, isolating/monitoring close contacts, timely corpse removal, post-recovery condom use, and preventing or quarantining imported cases. EVD may re-emerge within two decades without control and prevention measures. Mass vaccination campaigns and control and prevention measures should be instituted to prevent future EVD epidemics.

Epidemiological survey of dyslipidemia in civil aviators in china from 2006 to 2011.

Aim. This study aimed to analyze blood lipid levels, temporal trend, and age distribution of dyslipidemia in civil aviators in China. Methods. The 305 Chinese aviators were selected randomly and followed up from 2006 to 2011. Their total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels were evaluated annually. Mean values for each parameter by year were compared using a linear mixed-effects model. The temporal trend of borderline high, high, and low status for each index and of overall borderline high, hyperlipidemia, and dyslipidemia by year was tested using a generalized linear mixed model. Results. The aviators' TC (F = 4.33, P < 0.01), HDL-C (F = 23.25, P < 0.01), and LDL-C (F = 6.13, P < 0.01) values differed across years. The prevalence of dyslipidemia (F = 5.53, P < 0.01), borderline high (F = 6.52, P < 0.01), and hyperlipidemia (F = 3.90, P < 0.01) also differed across years. The prevalence rates for hyperlipidemia and dyslipidemia were the highest in the 41-50-year-old and 31-40-year-old groups. Conclusions. Civil aviators in China were in high dyslipidemia and borderline high level and presented with dyslipidemia younger than other Chinese populations.

The impact of the vaccination program for hemorrhagic fever with renal syndrome in Hu County, China.

The incidence of hemorrhagic fever with renal syndrome (HFRS) in Hu County ranked third of all counties in China in 2010. Although this county has provided a HFRS vaccination program freely since 1994, the impact of HFRS remains quite substantial. In order to continue the vaccination program effectively and control HFRS, a detailed understanding of the effect of the vaccination program should be undertaken. The Cochran-Armitage trend test was employed to examine the temporal trends of HFRS incidences, mortality rate and vaccination compliance. Temporal cluster analysis was performed to detect time periods of high HFRS risk. Cross correlation analysis was conducted to detect the correlation between HFRS incidence and vaccination compliance. Wavelet analysis was employed to detect the shift of the periodicity of HFRS. Between 1971 and 2011, the HFRS incidence and mortality rate ranged from 9.53/100,000 to 300.57/100,000 and 0 to 24.91/100,000, respectively, with a fluctuating but distinctly declining trend (incidence: Z=-34.38, P<0.01; mortality rate: Z=-23.44, P<0.01). The vaccination compliance ranged from 4.55% to 83.67%, with a distinctly increasing trend (Z=1621.70, P<0.01). The most likely temporal cluster of the HFRS epidemic was between 1983 and 1988 (RR=3.44, P<0.01) or 1979-1988 (RR=3.18, P<0.01) with different maximum temporal cluster size. There was a negative correlation between HFRS incidence and vaccination compliance when the lagged year was 1 and 2 (cross correlation coefficient=-0.51 and -0.55). The periodicity of HFRS epidemic was prolonged from about 5 years during 1976-1988 to 15 years after 1988, especially after the start of HFRS vaccination in 1994. In conclusion, the increase in vaccination compliance may play an important role in HFRS control and prevention in Hu County, China.