Thermal Behavior,Nonisothermal Decomposition Reaction Kinetics of Mixed Ester Double-base Gun Propellants

The thermal decomposition behavior and nonisothermal reaction kinetics of the double-base gun propellants containing the mixed ester of triethyleneglycol dinitrate（TEGDN） and nitroglycerin（NG） were investigated by thermogravimetry（TG） and differential thermogravimetry（DTG）, and differential scanning calorimetry（DSC） under the high-pressure dynamic ambience. The results show that the thermal decomposition processes of the mixed nitric ester gun propellants have two mass-loss stages. Nitric ester evaporates and decomposes in the first stage, and nitrocellulose and centralite II（C2） decompose in the second stage. The mass loss, the DTG peak points, and the terminated temperatures of the two stages are changeable with the difference of the mass ratio of TEGDN to NG. There is only one obvious exothermic peak in the DSC curves under the different pressures. With the increase in the furnace pressure, the peak temperature decreases, and the decomposition heat increases. With the increase in the content of TEGDN, the decomposition heat decreases at 0.1 MPa and rises at high pressure. The variety of mass ratio of TEGDN to NG makes few effect on the exothermic peak temperatures in the DSC curves at different pressures. The kinetic equation of the main exothermal decomposition reaction of the gun propellant TG0601 was determined as： dα/dt=1021.59（1-α）3e-2.60×104/T. The reaction mechanism of the process can be classified as chemical reaction. The critical temperatures of the thermal explosion（Tbe and Tbp） obtained from the onset temperature（Te） and the peak temperature（Tp） are 456.46 and 473.40 K, respectively. ΔS≠, ΔH≠, and ΔG≠ of the decomposition reaction are 163.57 J·mol^-1·K^-1, 209.54 kJ·mol^-1, and 133.55 kJ·mol^-1, respectively.

A comparative study on environmental surveillance of enterovirus:Using a two-phase separation method and a filtration method with a mixed cellulose ester(MCE)membrane

This study aimed to compare the sensitivity of two-phase separation and the filtration method using a mixed cellulose ester(MCE)membrane to detect enteroviruses in sewage samples.From December 2015 to July 2016,four domestic sewage samples(1 L/sample)were collected monthly from the Guangzhou Liede Sewage Treatment Plant,and each sewage sample was divided into two aliquots(500 mL).The sewage sample was concentrated using the two-phase separation and the filtration method using an MCE membrane,and the treated solutions were inoculated into cells for enterovirus isolation.Polymerase chain reaction amplification,VP1 sequencing,and enterovirus molecular typing were performed on the positive isolates.The detection rates of poliovirus(PV)and non-polio enterovirus(NPEV)obtained using the filtration method using an MCE membrane were higher than those using the two-phase separation method.McNemar's test showed that the detection rates of PV,NPEV,type 1 Sabin-like(SL1),type 2 Sabin-like(SL2),and type 3 Sabin-like(SL3)strain were not statistically significant(P>0.05).In Guangdong Province,China,the detection rates for PV and NPEV were 53.13%and 62.50%(20/32),respectively.Twenty-seven PVs were isolated,three highly variable strains of the type 1 vaccine,with seven nucleotide substitutions in the VP1 region,compared with the type 1 Sabin strains.Eighty-seven strains of NPEV were isolated and nine serotypes were identified,among which coxsackievirus B3(CVB3),echovirus 6(E6),and echovirus 11(E11)were the dominant strains.The filtration method using an MCE membrane is more sensitive than two-phase separation and can be used as a robust,sensitive,and cost-effective method to isolate enteroviruses from sewage.

Comparison of concentration methods for detection of hepatitis A virus in water samples

Hepatitis A virus is a pathogen associated with water pollution.Contaminated drinking water can cause hepatitis A outbreaks,lead to economic losses,and even threaten human lives.It is difficult to detect low levels of hepatitis A virus in water,so the virus must be concentrated in order to quantify it accurately.Here,we present a simple,rapid,efficient technique for the concentration and detection of hepatitis A virus in water.Our data showed that adding phosphate-buffered saline to the water,pre-filtering the water,and adding Trizol reagent directly to the filtration membrane can significantly improve concentration efficiency.Of three types of filtration membranes studied(mixed cellulose ester membrane,polyvinylidene fluoride membrane,and nylon membrane),the concentration efficiency using mixed cellulose ester membrane with a 0.1-μm pore size was the highest,reaching 92.62 ± 5.17%.This method was used to concentrate hepatitis A virus in water samples from Donghu Lake.Using SYBR Green real-time reverse transcription polymerase chain reaction analysis,the detection sensitivity of this method reached 10~1 copies/μL and its concentration efficiency reached 79.45 ± 9.88%.