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[Objective] In order to provide a theoretical basis for the transformation and development of resource-based cities, the contraction states of different types of resource-based cities are revealed and their contraction tracks are simulated. [Methods] Taking 116 prefecture-level resource-based cities in China as the research object, the multi-dimensional shrinkage identification method was used to measure the shrinkage intensity of different types of cities, fit the shrinkage process, and analyze the evolution characteristics. [Results] (1) From 2000 to 2020, 56 resource-based cities in China will experience population contraction (48.28%), 42 will experience economic contraction (36.21%), and 26 of them will experience double population and economic contraction (22.41%). (2) In terms of development stage, the proportion of shrinkage in declining, mature and growing cities is higher, 65.22%, 63.49% and 60.00%, respectively. From the perspective of resource type, the shrinkage ratio of forestry, oil and gas and comprehensive resource-based cities is higher, and the shrinkage of forestry cities is particularly significant, 80% of cities have double shrinkage of population and economy. (3) Resource-based shrinking cities are mainly distributed in the north of Dandong and Panzhihua Line, and clustered in the northeast and Shaanxi, Gansu, Shanxi, Mongolia, and other regions. (4) There is a certain regularity in the evolution trajectory of resource-based shrinking cities, which can be divided into two categories: smart contraction and typical contraction, and the typical contraction is further subdivided into contraction appearance, contraction advancement and contraction significance. The number of cities whose trajectory type is contraction propulsion is the largest, accounting for 33.33%. The trajectory types of contraction were mainly concentrated in two types of cities, namely regeneration type (63%) and decline type (47%). [Conclusion] The dual-dimension measurement of population and economy can identify the contraction of resource-based cities more comprehensively, and the simulation and classification of contraction trajectories of different types of resource-based cities can provide references for the transformation and development of resource-based cities.

IntroductionAccording to the reactivity hypothesis and the diathesis-stress model, repeated activation of the stress system has a negative effect on health, and this effect may differ because of individual characteristics. Thus, the present study explores the effect of chronic stress on fatigue and investigates its mechanism.MethodsA questionnaire survey of 288 participants selected from the northwest part of China was conducted (13.89% females; ages ranged from 18 to 34 years, with M ± SD = 23.14 ± 3.79 years) on chronic stress, fatigue, depression, anxiety, and negative emotion differentiation. SPSS 28.0 was used to process descriptive statistics and correlation analysis and the PROCESS macro was used to analyze the moderated chained multi-mediation.ResultsChronic stress was found to be positively correlated with fatigue, depression, and anxiety; depression and anxiety played a chained multi-mediating role between chronic stress and fatigue, and negative emotion differentiation played a moderating role in the chained multi-mediation model.DiscussionCompared with depression, anxiety plays a more important role in the influence of chronic stress on fatigue. Therefore, it is necessary to pay more attention to anxiety symptoms and take appropriate intervention measures. Negative emotion differentiation plays a moderating role. Improving negative emotion differentiation through mindfulness and adaptive emotion regulation is an effective way to reduce the influence of chronic stress on fatigue.

The maintenance cost of offshore wind farms accounts for a high proportion of the total cost of power generation. In order to reduce the operational and maintenance costs of offshore wind farms, based on a reliability threshold, a maintenance strategy is proposed in the paper that considers the fault-relatedness among subsystems and the subsystem fault risk levels of wind turbine units. This strategy includes fault risk levels, dual reliability thresholds, and a maintenance matrix. Firstly, a fault chain model is used to describe the fault relationships among subsystems of wind turbine units, and reliability models for each subsystem are established. Secondly, the concept of multi-level maintenance is introduced, and the optimization model of wind farm opportunity maintenance strategy considering the fault risk level is proposed. The risk factor of subsystem opportunity maintenance is optimized using particle swarm algorithm, and then the maintenance strategy of a single unit is determined. Thirdly, an offshore wind farm maintenance strategy optimization model based on the maintenance matrix is proposed by considering factors such as offshore accessibility and spare parts inventory. The model takes the minimum total maintenance cost per unit time as the objective function and dynamically adjusts the maintenance strategy according to the subsystem's spare parts inventory and failure risk level. Finally, a single wind turbine in an offshore wind farm is used as an example to analyse the impact of factors such as accessibility and multilevel maintenance on the wind farm opportunity maintenance strategy. The results show that the opportunity maintenance strategy considering the failure risk level can reduce the cost by 27.34% compared with the traditional opportunity maintenance strategy, which verifies the effectiveness of the proposed opportunity maintenance strategy in reducing maintenance costs.

Monocyte-mediated inflammatory responses play a key role in the progression of atherosclerosis. Anthocyanins are polyphenolic flavonoids that are abundant in various dark-colored vegetables, fruits and cereals, which possess a wide range of biological activities. Cyanidin-3-O-β-glucoside (Cy-3-g) is an important anthocyanin monomer. The current study aimed to explore the effects of black rice-derived Cy-3-g on lipopolysaccharide (LPS)-induced inflammatory responses in Tohoku hospital pediatrics-1 (THP-1) as well as its possible mechanism of action. Crude anthocyanins from black rice were obtained by extraction with ethanol-hydrochloric acid solution and macroporous resin adsorption and purified by medium-pressure liquid chromatography with UV detection. Cy-3-g with a purity greater than 96.5% was obtained. THP-1 monocytes were sequentially incubated with different concentrations (0, 0.1, 0.25 and 0.5 μg/mL) Cy-3-g for 4 h, and LPS (50 ng/mL) for additional 48 h. The levels of interleukin (IL)-1β, IL-6, IL-8, IL-10 and tumor necrosis factor (TNF)-α in the culture were determined by enzyme-linked immunosorbent assay (ELISA), and the mRNA expression levels of the genes encoding IL-1β, IL-6, IL-8, IL-10, TNF-α, Toll-like receptor 4 (TLR4) and nuclear factor kappa B (NF-κB) p65 were measured by quantitative polymerase chain reaction (PCR). Moreover, the protein expression levels of TLR4, NF-κB p65 and inhibitor of NF-κB (IκBα) were detected by Western blot. The LPS-induced increase in the relative mRNA expression levels and release levels of IL-1β, IL-6 and TNF-α in THP-1 cells was significantly inhibited by all concentrations of Cy-3-g tested (P 0.05). Cy-3-g at 0.25 and 0.50 μg/mL significantly inhibited the mRNA and protein expression of TLR4 and NF-κB p65 (P 0.05). Black rice-derived Cy-3-g exerts a protective effect on LPS-induced inflammatory injury of THP-1 monocytes possibly through down-regulating the TLR4/NF-κB signaling pathway.

Electromagnetic interference (EMI) shielding rubber nanocomposites were fabricated via a simple rubber roll milling technique based on the filler distribution behavior in the immiscible natural rubber (NR) and acrylonitrile-butadiene (NBR) (50/50) blends with varying amounts of multiwall carbon nano tubes and [Fe.sub.3][O.sub.4] nanoparticles. All nanocomposites showed a co-continuous phase structure, while the distribution behavior of filler was diverse correlated with the filler content and type. The mechanical properties, electrical conductivity, and EMI shielding effectiveness (SE) of rubber composites were characterized. The maximum EMI SE of 29.4 dB at 12.4 GHz was achieved in the rubber composites loaded with 15 phr MWCNTs and 15 phr [Fe.sub.3][O.sub.4] nanoparticles. The EMI shielding mechanisms of such materials were also discussed. The observation in this work provided a possible idea to the industrial manufacture electromagnetic interference shielding rubber nanocomposites, and contributed to expanding its application fields with higher mechanical property requirements and flexibility. KEYWORDS electromagnetic interference shielding, immiscible rubber blend, mechanical properties, polymer-matrix composites, 1 | INTRODUCTION With extensive applications of electronic and telecommunication devices in daily life, electromagnetic pollution has become one of the serious environmental problems because of its adverse effects on [...]