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After a major debt crisis occurs in a listed company, the stock prices of related enterprises may also fluctuate sharply, resulting in the spread of debt risk to more enterprises. Taking the stocks of listed companies as network nodes, we constructed a complex stock market network over three periods of time through the logarithmic return rate of stocks for the three periods of prophase, metaphase, and anaphase of the debt crisis. We studied the topological characteristics of the network and destructiveness over the three periods. Finally, the minimum spanning tree was used to construct a network and the community structure of the network. The empirical analysis took the debt crisis of the China Evergrande Company as an example to analyze the impact of its major debt crisis on the Chinese stock market. The research findings were as follows: First, the debt crisis increased the inter-industry connections within the network, that is, the correlations between enterprises in different industries was enhanced. Second, the closeness of the cross-industry connections increased the connectivity efficiency of the network, but compared with the other two periods, the debt crisis in the metaphase was less stable. Third, community research showed that in the metaphase of the debt crisis, the enterprises became the core nodes of the network. [ABSTRACT FROM AUTHOR]

Cement is a widely used construction material globally. Its manufacturing contributes to anthropogenic CO2 emissions significantly. However, its alkaline compounds can absorb CO2 from the surrounding environment and engage in a carbonation reaction, thereby functioning as a carbon sink. As a major cement producer and consumer, China has an important responsibility to rigorously investigate and accurately account for cement carbon uptake. This study presents a comprehensive analytical model of cement carbon uptake from China, revealing a substantial increase in carbon uptake from 1930 to 2021, peaking at 426.77 MtCO2 (95% Confidence Interval: 317.67–874.33 Mt CO2) in 2021. The uptake accounts for 8.10% to 45.40% of China's annual land sink and 2.51% to 4.54% of the global land sink. The cumulative carbon uptake by cement is approximately 7.06 Gt CO2 (95% CI: 5.22–9.44 Gt CO2) during this period, offsetting 50.7% of the total emissions (13.91 Gt CO2, 95% CI: 12.44–17.00 Gt CO2) from the cement industry. Notably, cement mortar contributed to most absorption (65.64%). From a life cycle perspective, the service stage of cement materials is the period where the largest CO2 sink is formed, accounting for 90.03% of the total. Therefore, the potential for carbon sequestration in cement materials and their waste is enormous. Additionally, the model improves the accuracy of cement carbon accounting, supporting both China and global carbon neutrality assessments. Thus, it is crucial for China to achieve its carbon neutrality goals sooner by prioritizing the environmental benefits of cement materials and wastes, and accelerating the development and commercialization of CO2 sequestration technologies for cement and its by-products. [ABSTRACT FROM AUTHOR]

The purpose of this study is to analyze the topological structure dynamics of the complex network of stocks before and after the outbreak of the COVID-19, so as to provide a basis for preventing financial risks. We calculate Pearson correlation coefficient between enterprises according to logarithmic rate of return and trading volume ratio of enterprises' stocks, and then constructed a complex network of stock market price and volume before and after the outbreak of the COVID-19. First, through thresholding and heat map imaging of the correlation matrix, the change characteristics of the correlation between various industries in 2019 and 2020 are studied. Second, the node degree, average weighted degree, graph density, clustering coefficient, and average clustering coefficient are used to study the topological structure change of the complex network of stock correlation. Third, the principle of node betweenness centrality is used to analyze the characteristics of a complex network after removing the core nodes. The research shows that, first, under the influence of the COVID-19 pandemic, the correlation among industries has the characteristics of industrial clusters, that is, the correlation in a industry is strengthened. In addition to banking, the correlation between industries has weakened, and the correlation between the banking industry and other industries has strengthened. Second, the node difference in betweenness centrality of core nodes in 2020 is higher than that in 2019, indicating that the network stability in 2019 is higher than that in 2020. These two points indicate that under the influence of the COVID-19 epidemic, the complex network topology of China's entire stock market has changed, and companies need to undertake countermeasures in the face of the crisis to effectively prevent and control systemic risks. [ABSTRACT FROM AUTHOR]