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  • Author or Editor: Fan Lan x
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Authors: Fan Lan, Xiang Wang, Xianglan Xu, Rongbin Zhang and Ning Zhang

Abstract

SnO2 catalysts were prepared with the precipitation method by varying the pH and SnCl4 concentration. For comparison, another two SnO2 samples were also synthesized with sol–gel and combustion methods. All of the catalysts were characterized by N2-BET, XRD and H2-TPR. It was found that the CO oxidation activity of the precipitation samples increases with an increase in pH, while the CH4 oxidation activity seems unchanged. The change of the SnCl4 concentration has little influence on the activity for both CO and CH4 oxidation. The sol–gel sample has relatively higher CO but similar CH4 oxidation activity, due to its higher surface area and finer particle sizes. On the contrary, the combustion sample displays the lowest activity for both reactions, due to its extra low surface area and inert oxygen species.

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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

The working memory (WM) ability of internet addicts and the topology underlying the WM processing in internet addiction (IA) are poorly understood. In this study, we employed a graph theoretical framework to characterize the topological properties of the IA brain network in the source cortical space during WM task.

Methods

A sample of 24 subjects with IA and 23 matched healthy controls (HCs) performed visual 2-back task. Exact Low Resolution Electromagnetic Tomography was adopted to project the pre-processed EEG signals into source space. Subsequently, Lagged phase synchronization was calculated between all pairs of Brodmann areas, the graph theoretical approaches were then employed to estimate the brain topological properties of all participants during the WM task.

Results

We found better WM behavioral performance in IA subjects compared with the HCs. Moreover, compared to the HC group, more integrated and hierarchical brain network was revealed in the IA subjects in alpha band. And altered regional centrality was mainly resided in frontal and limbic lobes. In addition, significant relationships between the IA severity and the significant altered graph indices were found.

Conclusions

In conclusion, these findings provide evidence to support the notion that altered topological configuration may underline changed WM function observed in IA.

Open access