Reactive Molecular Dynamics Simulations of the Thermal Decomposition Mechanism of 1,3,3-Trinitroazetidine.

1,3,3-Trinitroazetidine (TNAZ) has a molecular formula of C3 H4 N4 O6 and the characteristics of low melting point, low impact sensitivity and good thermal stability. It is suitable for melt casting and pressed charges, and it has broad prospects for applications in low-sensitivity ammunition. In this study, the thermal decomposition of TNAZ crystals at high temperature was calculated by molecular dynamics simulation with the ReaxFF/lg reactive force field. The change in the potential energy of TNAZ, the formation of small-molecule products and clusters, and the initial reaction path of TNAZ were analysed. The kinetic parameters of different reaction stages in TNAZ thermal decomposition were obtained. The primary thermal decomposition reaction of TNAZ was found to be as follows: N-NO2 and C-NO2 bonds broke; a H atom on the quaternary ring was transferred to the nitro group; and the C-HNO2 and N-HNO2 bonds broke. The main decomposition products of TNAZ were thus NO2 , NO, N2 , H2 O, CO2 and HNO2 , as well as macromolecular clusters. The size of the cluster structure was related to the reaction temperature, and the higher the temperature was, the smaller the cluster size was.

Comparison of the diagnostic value of four tests for superior labrum anterior and posterior lesions of the shoulder / 中华骨科杂志

Objective To compare the diagnostic value of four signs for superior labrum anterior and posterior (SLAP) lesions of the shoulder. Methods The physical examination was performed randomly on 81 cases with abnormalities of the shoulder. There were four tests, including Kibler anterior sliding test, Liu crank test, O'Brien active compression test and Kim biceps load test Ⅱ. The arthroscopic examination were also performed. The result of the arthroscopic examination was considered as a golden standard, so that we could estimate the diagnosis value of the four tests according to the method of evaluation of diagnosis test on clinical epidemiology, their sensitivity, specificity, positive and negative predictive value, accuracy. Results There were 21 cases diagnosed as SLAP lesions by arthroscopy. The diagnosis value of Kim biceps load test Ⅱ was the highest among the four tests, in which 19 of true positive, 59 of true negative, 1 of false positive, only 2 of false negative case; while the sensitivity was 90.48%, specificity was 98.33%, positive predictive value was 95.00%, negative predictive value was 96.72%, and accuracy was 96.30%. However the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of Kibler anterior sliding test were 76.19%, 96.67%, 88.89%, 92.06%, 91.33%; and those of Liu crank test were 85.71%, 93.33%, 81.82%, 94.92%, 91.35%; those of O'Brien active compression test were 80.95%, 91.66%, 77.27%, 93.22%, 88.89%. Conclusion Kim Biceps load test Ⅱ may be the best for clinical diagnosis of SLAP lesions of the shoulder.