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Abstract  

Many investigations and researches studied the reaction ability between high explosive RDX and RDX with other chemicals. However, accidents still occur and operating problems exist among the RDX manufacturing process. This study utilized inherent safety concepts and DSC thermal analysis to assess the incompatible reaction hazards of RDX during usage, handling, storage, transporting and manufacturing. This assessment includes thermal curve observations and kinetic evaluations. A decomposition mechanism of the incompatible reaction is proposed. Among all the contaminants evaluated in this study, the existence of ferrous chloride tetrahydrate, ferric chloride hexahydrate and nitric acid shifted the main endothermic and exothermic reactions of RDX. These contaminants further advanced the exothermic temperature onset average by about 53, 46 and 61C, respectively. The summarized results suggest that ferric oxide, ferrous chloride tetrahydrate, ferric chloride hexahydrate, acetone solution and nitric acid can influence the reaction and thermokinetic properties of RDX. These chemicals could induce potential hazards by causing temperature control instability, heating and cooling systems failure, and produce an unexpected secondary explosion. According to the conclusions of this study, potential incompatible RDX hazards during usage and manufacturing could be avoided.

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Journal of Thermal Analysis and Calorimetry
Authors:
Yunbo Zhai
,
Wenfeng Peng
,
Guangming Zeng
,
Zongming Fu
,
Yuanming Lan
,
Hongmei Chen
,
Chang Wang
, and
Xiaopeng Fan

Abstract

The pyrolysis characteristics and kinetics of sewage sludge for different sizes (d < 0.25 mm, 0.25 mm < d < 0.83 mm, and d > 0.83 mm) and heating rates (5, 20, and 35 °C/min) were investigated in this article. The STA 409 was utilized for the sewage sludge thermogravimetric analysis. FTIR analysis was employed to study the functional groups and intermediates during the process of pyrolysis. Meanwhile, a new method was developed to calculate pyrolysis kinetic parameters (activated energy E, the frequency factor A, and reaction order n) with surface fitting tool in software MATLAB. The results show that all the TG curves are divided into three stages: evaporation temperature range (180–220 °C), main decomposition temperature range (220–650 °C), and final decomposition temperature range (650–780 °C). The sewage sludge of d < 0.25 mm obtains the largest total mass loss, especially at the heating rate of 5 °C/min. By FTIR analysis, the functional groups including NH, C–H, C=C, etc., are all found in the sewage sludge. There is a comparison between the FTIR spectra of sludge heated to 350 °C (temperature associated to maximum devolatilization rate in the second stage) and the FTIR spectra of sludge heated to 730 °C (temperature associated to maximum devolatilization rate in the third stage). In the second stage, the alcohols, ammonia, and carboxylic acid in the sludge have been mostly decomposed into gases, and only a little bit of compounds containing CH and OH of COOH exist. The pyrolysis kinetic parameters of second stage are as follows: the reaction orders are in the range of 1.6–1.8 and the activation energy is about 45 kJ/mol. The frequency factor increases with the increase of heating rate and sewage sludge size.

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Abstract

Background and aims

Mobile phone addiction (MPA) is emerging among adolescents, especially during the COVID-19 pandemic. Nevertheless, there is a dearth of knowledge regarding the correlation between MPA and suicide behaviors and its mechanism. The objective of the current study is exploring the direct effect of MPA on suicide behaviors and the indirect effect through poor sleep quality.

Methods

A total of 18,900 Chinese adolescents aged 12 to 18 were recruited via a multi-stage cluster sampling method.

Results

The prevalence of MPA and poor sleep quality was 26.2 and 23.1%, respectively. During the past year, 24.4% participants were involved in suicide behaviors. Specifically, suicide ideators, suicide planners, and suicide attempters were 10.7, 8.4, and 5.3%, respectively. Particularly, rural females had the highest prevalence of suicide behaviors, MPA, and poor sleep quality. Logistic regression analysis showed that MPA was significantly associated with suicide ideators (OR = 1.22, 95% CI: 1.09–1.37, p < 0.001) and planners (OR = 1.18, 95% CI: 1.04–1.34, p < 0.05), but not for suicide attempters (p > 0.05). Structural equation modelling demonstrated that MPA had direct effect on suicide behaviors (β = 0.145, 95% CI = 0.127–0.160), and poor sleep quality partially mediated the relationship (the mediating ratio was 46.7%). The mediating ratio of poor sleep quality was the highest in urban males.

Conclusions

MPA has both direct and indirect effects on suicide behaviors. For suicide prevention, limited mobile phone use and improvement sleep quality may be practical for adolescents. Additionally, more efforts of intervention could give priority to rural girls.

Open access
Acta Veterinaria Hungarica
Authors:
Chang-Liang Yan
,
Qi-En Yang
,
Guang-Bin Zhou
,
Yun-Peng Hou
,
Xue-Ming Zhao
,
Zhi-Qiang Fan
,
Man-Qing Liu
,
Lin Liu
, and
Shi-En Zhu

The present study was designed to investigate the cryotolerance of in vitro fertilised (IVF) mouse embryos at various preimplantation developmental stages. IVF mouse embryos were vitrified by the open-pulled straw (OPS) method. After warming, embryos were morphologically evaluated and assessed by their development to blastocysts, hatched blastocysts or term. The results showed that a high proportion (93.3–100.0%) of vitrified embryos at all developmental stages were morphologically normal after recovery. The developmental rate of vitrified 1-cell embryos to blastocyst (40.0%) or hatched blastocyst (32.7%) or term (9.3%) was significantly lower than that from other stages (P < 0.05). Vitrified embryos from 2-cell to early blastocyst stage showed similar blastocyst (71.8–89.5%) and hatched blastocyst rates (61.1–69.6%) and could develop to term without a significant loss of survival compared with those of fresh embryos (P > 0.05). Vitrified 2-cell embryos showed the highest survival rate in vivo (50.6%, 88/174), compared with that from other stages (9.3–30.5%, P < 0.05). The data demonstrate that the OPS method is suitable for the cryopreservation of IVF mouse embryos from 2-cell stage to early blastocyst stage without a significant loss of survival. Embryos at the 2-cell stage had the best tolerance for cryopreservation in the present study.

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Abstract  

Cumene hydroperoxide (CHP) and its derivatives have caused many serious explosions and fires in Taiwan as a consequence of thermal instability, chemical contamination, and even mechanical shock. It has been employed in polymerization for producing phenol and dicumyl peroxide (DCPO). Differential scanning calorimetry (DSC) was used to analyze the thermal hazard of CHP in the presence of sodium hydroxide (NaOH), sulfuric acid (H2SO4), and sodium bisulfite (Na2SO3). Thermokinetic parameters for decomposition, such as exothermic onset temperature (T 0 ), maximum temperature (T max ), and enthalpy (ΔH), were obtained from the thermal curves. Isothermal microcalorimetry (thermal activity monitor, TAM) was employed to investigate the thermal hazards during CHP storage and CHP mixed with NaOH, H2SO4, and Na2SO3 under isothermal conditions in a reactor or container. Tests by TAM indicated that from 70 to 90 °C an autocatalytic reaction was apparent in the thermal curves. According to the results from the TAM test, high performance liquid chromatography (HPLC) was, in turn, adopted to analyze the result of concentration versus time. By the Arrhenius equation, the activation energy (E a ) and rate constant (k) were calculated. Depending on the process conditions, NaOH was one of the incompatible chemicals or catalysts for CHP. When CHP is mixed with NaOH, the T 0 is induced earlier and the reactions become more complex than for pure CHP, and the E a is lower than for pure CHP.

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