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Effects of silver-graphene oxide nanocomposites on soil microbial communities
Kim, Min-Ji,Ko, Daegeun,Ko, Kwanyoung,Kim, Dawon,Lee, Ji-Yeon,Woo, Sang Myeong,Kim, Woong,Chung, Haegeun Elsevier 2018 Journal of hazardous materials Vol.346 No.-
<P><B>Abstract</B></P> <P>Due to the application of silver-graphene oxide (Ag-GO) in diverse fields, it is important to investigate its potential impacts on the environment including soils. In this study, the response of microbial communities in soils treated with Ag-GO synthesized by glucose reduction was determined by analyzing enzyme activities, biomass, and inorganic N concentrations and by pyrosequencing. In soils treated with 0.1–1mg Ag-GO g<SUP>−1</SUP> soil, the activities of β-glucosidase, cellobiohydrolase, and xylosidase decreased up to 80% and NO<SUB>3</SUB> <SUP>−</SUP> concentration decreased up to 82% indicating inhibited nitrification. Within the bacterial community, the relative abundance of <I>Acidobacteria</I> and <I>Cyanobacteria</I> in soils treated with Ag-GO were lower than that in control soil. Meanwhile, the relative abundance of <I>AD3</I> and <I>Firmicutes</I> tended to increase under Ag-GO treatments. These changes in bacterial community composition reflected lowered activities associated with C and N cycling. On the other hand, microbial biomass showed no distinct change in response to Ag-GO treatment. Our study can serve as important basis in establishing guidelines for regulating the release of nanocomposites such as Ag-GO to the soil environment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The response of microbial communities in soils treated with 0.1–1mgg<SUP>−1</SUP> soil Ag-GO was determined. </LI> <LI> Ag-GO significantly lowered C-cycling enzyme activity and inhibited nitrification. </LI> <LI> Ag-GO decreased the relative abundance of <I>Acidobacteria</I> and <I>Cyanobacteria</I> while it increased that of <I>Firmicutes</I>. </LI> <LI> Ag-GO can negatively affect soil microbial activity associated with C and N cycling and alter bacterial community composition. </LI> </UL> </P>
Decomposing Twitter Network in Tourism Marketing
Kim, Wonsik,Kim, Daegeun The International Promotion Agency of Culture Tech 2021 International Journal of Advanced Culture Technolo Vol.9 No.2
This study is to analyze the structure of the networks of tourism marketing on Twitter, identifying the most prominent users, the flow of information about tourism marketing, and the interaction between the users posting tweets. This study employs NodeXL pro as a visualization software package for social network analysis. The number of vertices or nodes is 171, and the number of the unique edges or links is 128, but there are 101 edges with duplicates, so the total links are 229, which means that there are fewer Twitter accounts in the social network on tourism marketing, but they have a few close relationships by sharing information. The research can map the social network of communicators of tourism marketing using Twitter data. The network has a complicated pattern, including one independent network and some connected networks. Some mediators connect each network and can control the information flow of tourism marketing. More communicators are getting the information than the ones providing it, which means that there is likely to be the dependence of information among communicators that can cause an obstacle and distortion of the information flow system, especially in the independent network.