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The establishment of prefecture-level cities is a major spatial achievement of the social structure transformation in the process of modernization in China. The optimization of the layout structure of such cities is an inherent requirement for deepening supply-side structural reform and is of great significance to the construction of a scientific and reasonable urbanization pattern. Using the district similarity coefficient and standard deviation ellipse model, this study discusses the spatial characteristics and existing problems of prefecture-level city setting. The results reveal the following: 1) In terms of spatial characteristics, since the reform and opening-up, the setting of prefecture-level cities in China has been greatly affected by policy factors, exhibiting a gradual trend of advancing from east to west and from coastal to inland. 2) After reform and opening-up, the addition of prefecture-level cities is an adjustment on the basis of the original regional system, including the establishment of a city, the merger of a city, promotion of a county or county-level city to a city, and so on. 3) With the development of economy and society, the "space" problem of the prefecture-level city setting has become increasingly prominent, which is closely related to the difference in the mode of city setting, resulting in the administrative centers above prefecture-level setting too close, "small horse and big cart" and other problems to varying degrees. 4) The spatial distribution of prefecture-level cities in China is generated in regional administrative districts against the background of industrialization and urbanization, developed in the strategic transformation of urban-rural differences and cross-border cooperation, and faced with the innovative challenge of regionalization adjustment in the process of regional restructuring and scale restructuring. 5) The "space" problem leads to the increase of the system cost of economic and social development to varying degrees. Therefore, the layout of productivity should be comprehensively considered in a wider scope, and the adjustment of prefecture-level administrative divisions can be carried out when necessary. The possible contribution of this study to the literature is reflected in the application of the similarity coefficient of administrative districts to reveal that "the prefecture-level city is highly similar to the original region." Moreover, the problems existing in the current setting are related to this, such as too close distance and call for great importance to the significance of the adjustment of administrative divisions of the prefecture-level city. The possible shortcomings are that the logic of such city administrative division adjustment needs to be further explored, and the analysis of the thinking path of this adjustment is insufficient. In the future, the research on relevant issues in prefecture-level cities should be strengthened. Additionally, it is necessary to change the thinking of the adjustment of the overall construction system and the internal adjustment of prefecture-level government districts, consider the layout of productive forces from a broader perspective, consider the level of administration, the scale of government districts and the spatial structure as a whole, and take comprehensive measures to meet the actual needs of national and local development.

The paper considers a bidimensional continuous-time risk model with subexponential claims and Brownian perturbations, in which the price processes of the investment portfolio of the two lines of business are two geometric Lévy processes and the two lines of business share a common claim-number process, which is a renewal counting process. The paper mainly considers the claims of each line of business having a dependence structure. When the claims have subexponential distributions, the asymptotics of the finite-time ruin probabilities ψ a n d (x 1 , x 2 ; T) and ψ s i m (x 1 , x 2 ; T) have been obtained. When the distributions of claims belong to the intersection of long-tailed and dominatedly varying-tailed distribution classes, the asymptotics of the finite-time ruin probability ψ o r (x 1 , x 2 ; T) is given. [ABSTRACT FROM AUTHOR]

The Yellow River Basin of China is a key region that contains myriad interactions between human activities and natural environment. Industrialization and urbanization promote social-economic development, but they also have generated a series of environmental and ecological issues in this basin. Previous researches have evaluated urban resilience at the national, regional, urban agglomeration, city, and prefecture levels, but not at the watershed level. To address this research gap and elevate the Yellow River Basin's urban resilience level, we constructed an urban resilience evaluation index system from five dimensions: industrial resilience, social resilience, environmental resilience, technological resilience, and organizational resilience. The entropy weight method was used to comprehensively evaluate urban resilience in the Yellow River Basin. The exploratory spatial data analysis method was employed to study the spatiotemporal differences in urban resilience in the Yellow River Basin in 2010, 2015, and 2020. Furthermore, the grey correlation analysis method was utilized to explore the influencing factors of these differences. The results of this study are as follows: (1) the overall level of urban resilience in the Yellow River Basin was relatively low but showed an increasing trend during 2010-2015, and significant spatial distribution differences were observed, with a higher resilience level in the eastern region and a low-medium resilience level in the western region; (2) the differences in urban resilience were noticeable, with industrial resilience and social resilience being relatively highly developed, whereas organizational resilience and environmental resilience were relatively weak; and (3) the correlation ranking of resilience influencing factors was as follows: science and technology level>administrative power>openness>market forces. This research can provide a basis for improving the resilience level of cities in the Yellow River Basin and contribute to the high-quality development of the region. [ABSTRACT FROM AUTHOR]

Soil salinization adversely affects soil quality and ecosystem. Many researches have tried to ameliorate saline soils by soil conditioners. However, little is known about the differences in the responses of soil bacterial communities to natural and artificial conditioners applied to saline soils. Therefore, in this study, the effects of natural humic acid (IK), synthetic polymer (IP), and composite material (IF) (mixture of IK and IP (1:1)) on bacterial community structure and functional genes in saline soil were evaluated to clarify their differences. The results showed that the application of the three soil conditioners significantly reduced soil pH and Na+ content but increased soil alkaline phosphatase, urease, invertase and catalase activities, bacterial diversity, and nutrients, compared to the control (no conditioner). IK application increased bacterial relative abundance (e.g., Subgroup_6, RB41, MND1, and KD4‐96) and metabolic functions (e.g., Two‐component system and Biosynthesis of amino acids) by increasing soil nitrogen and maintaining K+ and Na+ balance. IP application increased soil alkaline phosphatase and urease activities as well as bacterial relative abundance (e.g., Subgroup_6, RB41, MND1, Gemmatimonadaceae, and KD4‐96) and metabolic functions (e.g., Quorum sensing and carbon metabolism) by increasing soil organic carbon/nitrogen content. IF application increased the bacterial relative abundance of Subgroup_6, RB41, and MND1 by increasing soil available nitrogen and regulated their metabolic pathways (e.g., ABC transporters and microbial metabolism). On the whole, IK, IP, and IF could regulate the structure and function of soil bacterial community in saline soils. This study clarifies difference in the effects of different soil conditioners on the amelioration of saline soils from the perspective of soil microbiology, and provides a reference for the amelioration of saline soils in arid areas. [ABSTRACT FROM AUTHOR]

Consider a renewal risk model with stochastic return and stochastic perturbation, where the price process of the investment portfolio is a geometric Lévy process. When the claim sizes have a dependence structure, we derive the asymptotics of the finite-time ruin probability for all subexponential claim sizes. Particularly, when the claim sizes come from a subclass of the subexponential distribution class, the finite-time ruin probability has been estimated for claim sizes with a general dependence structure. [ABSTRACT FROM AUTHOR]

Soil salinity mediates microorganisms and soil processes, like soil organic carbon (SOC) cycling. Yet, how soil salinity affects SOC mineralization via shaping bacterial community diversity and composition remains elusive. Therefore, soils were sampled along a salt gradient (salinity at 0.25 %, 0.58 %, 0.75 %, 1.00 %, and 2.64 %) and incubated for 90 d to investigate (i) SOC mineralization (i.e., soil priming effects induced by cottonseed meal, as substrate) and (ii) the responsible bacteria community by using high-throughput sequencing and natural abundance of 13 C isotopes (to partition cottonseed-meal-derived CO 2 and soil-derived CO 2). We observed a negative priming effect during the first 28 d of incubation that turned to a positive priming effect after day 56. Negative priming at the early stage might be due to the preferential utilization of cottonseed meal. The followed positive priming decreased with the increase in salinity, which might be caused by the decreased α diversity of microbial communities in soil with high salinity. Specifically, soil pH and electrical conductivity (EC) along the salinity gradient were the dominant variables modulating the structure of the microbial community and consequently SOC priming (estimated by distance-based multivariate analysis and path analysis). By adopting two-way orthogonal projections to latent structures (O2PLS), priming effects were linked with specific microbial taxa; e.g., Proteobacteria (Luteimonas, Hoeflea, and Stenotrophomonas) were the core microbial genera that were attributed to the substrate-induced priming effects. Here, we highlight that the increase in salinity reduced the diversity of the microbial community and shifted dominant microorganisms (Actinobacteria and Proteobacteria: Luteimonas, Hoeflea, and Stenotrophomonas) that determined SOC priming effects, which provides a theoretical basis for understanding SOC dynamics and microbial drivers under the salinity gradient. [ABSTRACT FROM AUTHOR]