The present study explored the relationship between international students' Third Language Anxiety (TLA) and self-efficacy. The research data were collected through questionnaires involving 243 ...Chinese International students' L3 French Learning with L2 English and L3 French at one university in the U.K. Three of them were interviewed about their experience of anxiety and self-efficacy. Major findings include four underlying factors correlated with TLA and two underlying factors correlated with self-efficacy. Also, levels of these students' TLA were negatively correlated with the level of their self-efficacy, as shown in the correlational analysis. Then, two linear regression models were built to contribute to the prediction of their self-efficacy levels. Lastly, participants reported that grammatical and pronunciation similarities between English (L2) and French (L3) positively decreased their anxiety levels. All of these interviewees encountered communication apprehension. These findings can provide educational implications for L3 teaching and learning, inspiring teachers to consider international students' TLA and self-efficacy and thus propose some coping strategies.
The charge linearity of a photomultiplier reflects the difference between the number of photoelectrons in the anode output signal and the number of photoelectrons in the cathode. In this study, the ...nonlinearity of the photomultiplier tube output range from tens of photoelectrons to hundreds of photoelectrons was measured using a continuous Optical attenuator, and compared with the test scheme of alternating light emission of dual LED light sources. The results showed that the maxi-mum nonlinearity measured by the optical attenuation method increased from 102.62 to 104.55%, and the correctness of the optical attenuation method was verified through numerical methods.
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•Total and soluble Fe in PM2.5 decreased significantly in the COVID-19 lockdown in Hangzhou.•Fe solubility increased due to the enhanced oxidizing capacity in the COVID-19 ...lockdown.•Vehicular emission is a major source of aerosol Fe in Hangzhou under normal conditions.
Iron (Fe) in the atmosphere can affect atmospheric chemical processes and human health. When deposited into oceans, it can further influence phytoplankton growth. These roles of Fe fundamentally depend on its concentration and solubility. However, the sources of aerosol Fe and controlling factors of Fe solubility in megacities remain poorly understood. The outbreak of the COVID-19 pandemic causes large changes in human activities, which provides a unique opportunity to answer these key issues. Field observations were conducted before, during, and after the COVID-19 lockdown in Hangzhou, China. Our results show that in the COVID-19 lockdown stage, the concentrations of total Fe (FeT, 75.0 ng m−3) and soluble Fe (FeS, 5.1 ng m−3) in PM2.5 decreased by 78% and 62%, respectively, compared with those (FeT 344.7 ng m−3, FeS 13.5 ng m−3) in the pre-lockdown stage. The sharp reduction (81%) in on-road vehicles was most responsible for the aerosol Fe decrease. Surprisingly, the Fe solubility increased by a factor of 1.9, from 4.2% in the pre-lockdown stage to 7.8% in the COVID-19 lockdown stage. We found that the atmospheric oxidizing capacity was enhanced after lockdown restrictions were implemented, which promoted the formation of more acidic species and further enhanced the dissolution of aerosol Fe.
As one of the intense anthropogenic emission regions across the relatively
high-latitude (>40∘ N) areas on Earth, northeast
China faces the serious problem of regional haze during the heating period ...of
the year. Aerosols in polluted haze in northeast China are poorly
understood compared with the haze in other regions of China such as the North
China Plain. Here, we integrated bulk chemical measurements with single-particle analysis from transmission electron microscopy (TEM), nanoscale
secondary ion mass spectrometry (NanoSIMS), and atomic force microscopy
(AFM) to obtain morphology, size, composition, aging process, and sources of
aerosol particles collected during two contrasting regional haze events
(Haze-I and Haze-II) at an urban site and a mountain site in northeast
China and further investigated the causes of regional haze formation.
Haze-I evolved from moderate (average PM2.5: 76–108 µg m−3) to
heavy pollution (151–154 µg m−3), with the dominant PM2.5
component changing from organic matter (OM) (39–45 µg m−3) to
secondary inorganic ions (94–101 µg m−3). Similarly, TEM
observations showed that S-rich particles internally mixed with OM (named S-OM)
increased from 29 % to 60 % by number at an urban site and 64 %
to 74 % at a mountain site from the moderate Haze-I to heavy Haze-I events,
and 75 %–96 % of Haze-I particles included primary OM. We found that change
of wind direction caused Haze-I to rapidly turn into Haze-II (185–223 µg m−3) with predominantly OM (98–133 µg m−3) and
unexpectedly high K+ (3.8 µg m−3). TEM also showed that K-rich particles
internally mixed with OM (named K-OM) increased from 4 %–5 % by
number to 50 %–52 %. The results indicate that there were different sources
of aerosol particles causing the Haze-I and Haze-II formation: Haze-I was
mainly induced by accumulation of primary OM emitted from residential coal
burning and further deteriorated by secondary aerosol formation via
heterogeneous reactions; Haze-II was caused by long-range transport of
agricultural biomass burning emissions. Moreover, abundant primary OM
particles emitted from coal and biomass burning were considered to be one
typical brown carbon, i.e., tar balls. Our study highlights that large
numbers of light-absorbing tar balls significantly contribute to winter haze
formation in northeast China and they should be further considered in
climate models.
The synthesis of the new energetic material 4-amino-3-hydrazino-5-methyl-1,2,4-triazole, which shows excellent performance and reliable safety, has drawn attention recently. To fully characterize ...this material, a comprehensive analysis was performed using various techniques, including differential scanning calorimetry (DSC), infrared spectroscopy (IR), elemental analysis, and 1H and 13C NMR spectroscopy. Additionally, three compounds, 3, 5 and 9, were further characterized using single X-ray diffraction. The X-ray data suggested that extensive hydrogen bonds affect molecular structure by means of intermolecular interactions. In order to evaluate the explosive properties of these synthesized compounds, detonation pressures and velocities were calculated using EXPLO5 (V6.01). These calculations were carried out utilizing experimental data, including density and heat of formation. Among the explosives tested, compounds 7 and 8 exhibited zero oxygen balance and demonstrated exceptional detonation properties. Compound 7 achieved the highest recorded detonation pressure, at 34.2 GPa, while compound 8 displayed the highest detonation velocity, at 8887 m s−1.
4,4′-azobis(1,2,4-triazole) (Atrz) is an excellent thermally stable explosive that is widely used to synthesize high-energy nitrogen-rich compounds. However, current methods for synthesizing this ...compound are low-yield and exothermic. In order to overcome these limitations, in this study, a continuous method based on the use of continuous stirred tank reactor (CSTR) was used to prepare Atrz for the first time, and the optimal experimental conditions were obtained by single factor experimental method and orthogonal experimental method. The yield of Atrz increased from 20%-30% to 71.84%, and the purity reached 98.54%. The use of CSTR enables materials to be mixed efficiently, making the reaction process efficient and environmentally friendly. At the same time, this method has the advantages of simple reaction process, easy large-scale continuous production, and high yield.
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All-nitrogen materials, as a unique branch of energetic materials, have gained huge attentions, of which
cyclo-N
5
−
derivatives are the representative synthetically reported materials. However, the ...energetic performance of
cyclo-N
5
−
compounds has certain limitations and cannot go beyond that of CL-20. In order to reach the higher energy, in this work, we presented two kinds of polynitrogen species, N
4
and N
8
. Two isomers of N
4
and four isomers of N
8
were fully calculated by using density functional theory (DFT). Theoretical results show that all these polynitrogen materials exhibit excellent heats of formation (7.92–16.60 kJ g
−1
), desirable detonation performance (D: 9766–11620 m s
−1
;
p
: 36.8–61.1 GPa), as well as the remarkable specific impulses (330.1–436.2 s), which are much superior to CL-20. Among them,
N
4
-2
(tetraazahedrane) (D: 10037 m s
−1
;
p
: 40.1 GPa; I
sp
: 409.7 s) and cube
N
8
-4
(D: 11620 m s
−1
;
p
: 61.1 GPa; I
sp
: 436.2 s) have the highest energetic properties, which are expected to become promising high-energy-density-materials. Moreover, electrostatic surface potentials, Frontier molecular orbitals, infrared spectra, natural bond orbital charges, and weak interactions were also investigated to further understand their relationship between structure and performance.
The nonisothermal thermal decomposition kinetics of 4,4′-azobis-1,2,4-triazole (ATRZ) at different heating rates (5, 10, 15, and 20 °C·min–1) were investigated by thermogravimetry (TG) and ...differential scanning calorimetry (DSC) studies. The thermal decomposition kinetic parameters such as apparent activation energy (E) and pre-exponential factor (A) were calculated by the Kissinger, Ozawa, and Šatava-Šestak methods. The E and A values calculated by the above three methods are very close, which are 391.1 kJ·mol–1/1034.92 s–1, 381.1 kJ·mol–1/1034.30 s–1, and 393.4 kJ·mol–1/1035.76 s–1, respectively. Then, the decomposition mechanism function of ATRZ is analyzed by the calculated results. The results show that the decomposition temperature of ATRZ is about 300 °C and the exothermic decomposition speed is fast. The decomposition pathway of ATRZ was analyzed by pyrolysis-gas chromatography–mass spectrometry (PY-GC-MS). The thermal decomposition kinetic equation of the ATRZ was deduced.
Polynitrogen compounds contain a large amount of NN and N=N, and their decomposition products are mainly nitrogen, with the advantages of high density, high heat, high energy and pollution-free ...products. Such compounds have potential application prospects and are candidates for a new generation of energetic materials. The pentazolate anion, or cyclo-N5−, which is the first polynitrogen anion of azoles, has an impressive stable aromatic structure and has become a hot topic. In this review, we summary the research progress of pentazole synthesis in recent years, including the precursors, synthesis, properties and derivatives, which involves the following topics: (1) the preparation of cyclo-N5−; (2) synthesis of pentazole complexes; (3) properties and derivatives of cyclo-N5−. This review is intended to improve the understanding of pentazole for their further development and applications.
The research progress of cyclo-N5− synthesis in recent years, including the studies of the precursors, synthesis, properties and derivatives, were reviewed and summarized. Display omitted
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