Organic peroxides (OPs) have caused many momentous explosions and runaway reactions, resulting from thermal instability, chemical
pollutants, and even mechanical shock. In Taiwan, dicumyl peroxide (DCPO), due to its unstable reactive nature, has caused
two thermal explosions and runaway reaction incidents in the manufacturing process. To evaluate thermal hazards of DCPO in
a batch reactor, we studied thermokinetic parameters, such as heat of decomposition (†Hd), exothermic onset temperature (T0), maximum temperature rise ((dT/dt)max), maximum pressure rise ((dP/dt)max), self-heating rate (dT/dt), etc., via differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2).
Authors:C. Liao, S. Wu, T. Su, M. Shyu, and C. Shu
is an important commodity chemical that is globally applied in various polymerization
processes. The aim of this study was to obtain integrated thermokinetics and
safety parameters for polymerization of styrene. We mainly used differential
scanning calorimetry (DSC), thermal activity monitor (TAM), and simulative
methods to investigate thermal polymerization of styrene and styrene containing
various levels of 4-tertiary-butylcatechol
(TBC). The results obtained included the rate constant (k),
reaction order (n), apparent activation
energy (Ea), frequency
factor (A), and so on, from various DSC
curves and simulative methods. From DSC curves, the exothermic onset temperature
(T0) was about 105
and 132C for styrene and styrene containing 10 ppm TBC. On the other
hand, the test results from TAM indicated that styrene polymerization displays
an autocatalytic phenomenon from 50–85C. By means of this study,
the intrinsic safety of a system for styrene during transportation and storage
could be established.
An internal standard method has been applied for the determination of lanthanum, antimony, scandium, chromium, iron and cobalt
in commercial cigarettes by neutron activation analysis using gold as an internal standard element. These trace elements were
separated from irradiated samples by APDC (ammonium pyrrolidine dithiocarbamate)/Zeph (tetradecyl dimethyl benzyl ammonium
chloride) coprecipitation, followed by direct gamma-counting of the separated precipitate using a Ge(Li) detector. Standard
reference tobacco 1R1 prepared by the University of Kentucky was also analyzed by this procedure for the above 6 elements,
the results of which were compared with literature values. Good results were obtained by the present method.
Authors:S. Lin, J. Tseng, M. Lee, T. Wu, and C. Shu
Styrene is an important chemical in the petrochemical industry. In recent years, there have been sporadic releases, runaway
reactions, fires, and thermal explosion accidents incurred by styrene and its derivatives worldwide. The purpose of this study
was to estimate the impact of styrene and its derivatives of α-methylstyrene (AMS) and trans-β-methylstyrene (TBMS) contacting with benzaldehyde. Experiments were carried out to evaluate the thermokinetic parameters
estimated by differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III). TAM III was used to determine
the fundamental thermokinetics under various isothermal temperatures, 80, 90 and 100°C. This autocatalytic reaction was demonstrated
in thermal curves. After styrene was contacted with benzaldehyde, the exothermic onset temperature (T0) and the total heat of reaction (Qtotal) were altered by DSC tests. When benzaldehyde is mixed with AMS and TBMS, the reaction time will be shorter but the enthalpy
reduced, as revealed by TAM III tests.
As AMS and TBMS, respectively, were contacted with benzaldehyde, both exothermic phenomena were changed during the reaction
excursion. According to the results of this research, an operator should dictate the oxygen concentration in order to avoid
any potential hazards during handling and transportation.
Authors:J. Li, W. Dai, G. Xiao, H. Wang, Z. Zhang, and T. Wu
99Tc is an important radionuclides related to repository safety assessment. The mobility pertechnetate (TcO4−) can be reduced to immobility technetium(IV) hydrous oxides (TcO2·nH2O) by Fe(II)-bearing minerals. In China, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material
for the HLW repository, which is contained some FeO. The diffusion behavior of 99Tc was investigated in GMZ bentonite by through- and out-diffusion methods. The effective diffusion coefficient (De), the accessible porosity (εacc), apparent diffusion coefficient (Da) and distribution coefficient (Kd) were decreased with the increasing of dry density. The De values were (2.8 ± 0.2) × 10−11 m2/s and (3.5 ± 0.2) × 10−12 m2/s at dry density of 1,600 and 1,800 kg/m3, respectively. It was indicated that the dominating species was TcO4− during the diffusion processing. While, out-diffusion results showed that part of TcO4− may be reduced by Fe(II). The relationship of De and εacc could be described by Archie’s law with exponent n = 2.4 for 99Tc diffusion in GMZ bentonite. Furthermore, the relationship between Da and dry density (ρ) was exponential.
Authors:T. Wu, W. Dai, G. Xiao, F. Shu, J. Yao, and J. Li
With the low permeability and high swelling property, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling
material for a potential repository. The diffusion behaviors of HTO in GMZ bentonite were studied to obtain effective diffusion
coefficient (De) and accessible porosity (ε) by through- and out-diffusion experiments. A computer code named Fitting for diffusion coefficient
(FDP) was used for the experimental data processing and theoretical modeling. The De and ε values were (5.2–11.2) × 10−11 m2/s and 0.35–0.50 at dry density from 1,800 to 2,000 kg/m3, respectively. The De values at 1,800 kg/m3 was a little higher than that of at 2,000 kg/m3, whereas the De value at 1,600 kg/m3 was significantly higher (approximately twice) than that of at 1,800 and 2,000 kg/m3. It may be explained that the diffusion of HTO mainly occurred in the interlayer space for the highly compacted clay (dry
density exceeding 1,300 kg/m3). 1,800 and 2,000 kg/m3 probably had similar interlayer space, whereas 1,600 kg/m3 had more. Both De and ε values decreased with increasing dry density. For compacted bentonite, the relationship of De and ε could be described by Archie’s law with exponent n = 4.5 ± 1.0.
The present study was performed to investigate the effect of β-aminobutyric acid (BABA) treatment on defence activation in grape berries and to analyse its cellular mechanism. The results implied that BABA treatment at an effective concentration of 20 mM significantly inhibited gray mould rot caused by Botrytis cinerea in grape berries by inducing resistance. Accordingly, 20 mM BABA triggered a priming defence in grape suspension cells, since only the BABA-treated cells exhibited an accelerated ability for augmenting defence responses upon the pathogen inoculation. The primed cellular reactions were related to an early H2O2 burst, prompt accumulation of stilbene phytoalexins and activation of PR genes. Thus, we assume that 20 mM BABA can induce resistance to B. cinerea infection in intact grape berries perhaps via intercellular priming defence. Moreover, the BABA-induced priming defence is verified, because no negative effects on cell growth, anthocyanin synthesis, and quality impairment in either grape cells or intact berries were observed under low pathogenic pressure.
In the fourth part of this series of papers the authors investigate the way how the Khitan Small Script rendered the dental stops in initial position. They conclude that the main opposition was between the postaspirated and not postaspirated dental stops.
Authors:Anise M. S. Wu, Juliet Honglei Chen, Kwok-Kit Tong, Shu Yu, and Joseph T. F. Lau
Background and aims
Internet gaming disorder (IGD) has been mainly studied among adolescents, and no research to date has examined its prevalence in general Chinese adult populations. This study estimated the prevalence of probable IGD in community-dwelling adults in Macao, China. Associations between IGD and psychological distress (i.e., depression and anxiety) as well as IGD and character strength (i.e., psychological resilience and purpose in life) were also tested.
A random, representative sample of 1,000 Chinese residents (44% males; mean age = 40.0) was surveyed using a telephone poll design from October to November 2016.
The estimated prevalence of probable IGD was 2.0% of the overall sample and 4.3% among the recent gamers (n = 473), with no statistically significant sex and age effects observed (p > .05). The two most prevalent IGD symptoms were mood modification and continued engagement, despite negative consequences. Probable IGD respondents were more vulnerable to psychological distress (25.0% and 45.0% for moderate or above levels of depression and anxiety, respectively) than their non-IGD counterparts. They also reported a lower level of psychological resilience than non-IGD respondents. No significant buffering effect of the two character strength variables on the distress–IGD relationship was found.
Discussion and conclusions
These results provide empirical evidence that IGD is a mental health threat not only to adolescents but also to adults. IGD was significantly associated with psychological distress, which should be addressed in conjunction with IGD symptoms in interventions. Inclusion of gamers of both sexes and different age groups in future prevention programs is also recommended.