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  • Author or Editor: D. Dong x
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Abstract  

In activation analysis, the continuous neutron spectrum produced in a nuclear reactor can be both beneficial and detrimental. A continuous spectrum allows for activation of particular elements by using any number of neutron energies. However, upper threshold energies exist for most elements where reactions other than an (n, ) absorption will occur. In this situation, two different parent nuclides can be activated to the same product, which creates a problem in performing a quantitative analysis of one or the other nuclide. A methodology is presented where a system of equations is used to solve for the quantities of both nuclides by using different irradiation ports, and using specific neutron filters to "customize" the neutron flux.

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Abstract  

The glass formation and devitrification of GaF3-based glasses were studied by differential scanning calorimetry. A comparison of various simple quantitative methods to assess the level of stability of multicomponent fluoride glass systems is presented. Most of these methods are based on critical temperatures. In this paper a new parameter k b(T) is added to the stability criteria. The stability of several GaF3-based glasses were experimentally evaluated and correlated with the activation energies of crystallization via this new kinetic criterion and compared with those evaluated by other criteria.

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Abstract  

The sorption behavior of technetium on pyrrhotine was studied with batch experiments and diluted sulfuric acid (less than 2.88 mol/l) was used to dissolve the technetium adsorbed on pyrrhotine. A significant sorption of technetium on pyrrhotine was observed under aerobic and anaerobic conditions, and the sorption on the mineral was supposed to be due to the reduction of TcO4 - to insoluble TcO2 .nH2O. Sorbed technetium on the mineral could be desorbed by diluted sulfuric acid. The maximum desorption ratio under aerobic conditions was much higher than that of under anaerobic conditions, meanwhile, the desorption rates under anaerobic conditions were higher than that of under aerobic conditions in the initial stage of the experiments.

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Eight malting barley cultivars were used to investigate the cultivar and environmental effects on grain protein components and the relationships between protein fractions and β -amylase or β -glucanase activity. The results showed there was a great variation for three protein fraction (albumin, hordein and glutelin) contents over cultivars and locations, and a distinct difference in each protein fraction content between the locations for a given cultivars. Correlation analysis indicated that β -amylase activity was significantly correlated with three protein fraction contents and there was a negative correlation between glutelin content and β -amylase activity, but β -amylase activity positively correlated with albumin or hordein content. Furthermore, there was a significant positive correlation between total protein content and β -glucanase activity, and we found the hordein and glutelin content did not show correlated with β -glucanase activity but the albumin content was a significantly negative correlation with β -glucanase activity.

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Abstract

Background and aims

Due to the rapid spread of the novel coronavirus disease 2019 (COVID-19), policies based on the nature of “spatial distancing” have been implemented and have resulted in school suspensions and online learning among schoolchildren. In order to examine the impact of such policies on schoolchildren, the aims of the present study were to (i) assess changes in the level of engagement in three internet-related activities (smartphone use, social media use, and gaming) before and during the COVID-19 outbreak, including prolonged and problematic engagement in these activities; (ii) investigate the differences of psychological distress before and after COVID-19 outbreak; and (iii) to use structural equation modeling to investigate the mediating roles of problematic internet-related behaviors in the causal relationships of psychological distress and time spent on internet-related activities.

Methods

Self-report measures were used to assess internet-related activities and psychological distress. Time spent on internet-related activities, problematic use of internet-related activities, and psychological distress were collected from primary school students (N = 535; 265 boys; M age = 10.32 years [SD = 0.84]). The data were first collected before the COVID-19 outbreak (i.e., early November 2019) and then collected again during the school suspension due to COVID-19 outbreak (i.e., end of March 2020) for comparisons of changes.

Results

Schoolchildren spent significantly more time on the smartphone (increased 1.02 h daily; P < 0.001) and social media (increased 0.73 h daily; P < 0.001) but not gaming (increased 0.14 h daily; P = 0.07) during the school suspension compared to the baseline. Schoolchildren who increased by 15 or 30 min daily on internet-related activities showed an increased level of psychological distress. The association between problematic use of social media and psychological distress was stronger during the school suspension (β = 0.584) than at the baseline (β = 0.451; P < 0.001).

Conclusion

Increased problematic use of internet-related activities among schoolchildren was associated with greater psychological distress. Parents should therefore monitor internet-related activities and psychological distress of their children to support their mental health.

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