Search Results (87)

As China’s regional development enters a critical stage of population redistribution and urban transformation, the impact of population mobility on regional demographic structures and urban functional restructuring has become increasingly prominent. Against this backdrop of accelerating Beijing–Tianjin–Hebei integration, cities of varying types have been confronted with growing complexity in demographic transitions and socioeconomic stratification during their processes of absorbing or exporting populations. This study employed microdata from the National Bureau of Statistics to construct migration flow matrices and utilized a decomposition quantification approach to explore the impact of internal migration on the population structure and quality in 13 cities within the Beijing–Tianjin–Hebei region. The findings indicated that, while Beijing has achieved some success in population control, it overall exhibits a “large inflow and large outflow” pattern. Langfang has attracted a large number of highly educated individuals and male migrants under the spillover effect from Beijing. Shijiazhuang’s population attractiveness has increased, yet the outflow of highly educated individuals remains unmitigated. Meanwhile, the internal migrant structures in industrial cities such as Tianjin and Tangshan have undergone significant changes following the industrial transformation. Cities in the passive outflow area and agricultural transformation area have experienced siphoning effects, but they face different potential risks due to their unique characteristics. This study further enriches the understanding of the impact mechanisms underlying domestic population mobility and provides differentiated policy references for cities to reconcile their development objectives with demographic realities. Full article

Butter clams (Saxidomus gigantea) are a staple in the subsistence diets of Alaskan Native communities and are also harvested recreationally. This filter–feeding species can accumulate saxitoxins (STXs), potent neurotoxins produced by late spring and summer blooms of the microalga Alexandrium catenella. The consumption of tainted clams can cause paralytic shellfish poisoning (PSP). Traditional beliefs and early reports on the efficacy of removing clam siphons have created the impression that cleaning butter clams by removing certain tissues makes them safe to eat. However, the toxin distribution within clams can vary over time, making the practice of cleaning butter clams unreliable. This study tested the effectiveness of the cleaning methods practiced by harvesters on Kodiak Island, Alaska. Specifically, butter clams were cleaned by removing different tissues to produce samples of “edible” tissues that were tested for STX content. The results were compared to historical data from a study conducted in Southeast Alaska from 1948 to 1949. Using these data, the risk for an average–sized man and woman consuming 200 g of edible tissue was calculated. The results showed that for clams containing >200 µg STX–equivalents 100 g edible tissue⁻¹, no cleaning method reduced the concentration of STXs in the remaining tissue below the regulatory limit. Meals containing >900 µg STX–equivalents 100 g edible tissue⁻¹ posed a substantial risk of moderate or severe symptoms. No cleaning method assured that untested butter clams are safe to eat. Full article

The digital economy has become an important engine for global economic development by promoting optimal resource allocation and advancing industrial restructuring. Based on the panel data from 279 prefecture-level cities in China from 2012 to 2021, this paper constructs the spatial association networks of urban digital economy using a modified gravity model and analyzes the complex network characteristics and driving factors of urban digital economy growth by the social network analysis methods and the Quadratic Assignment Procedure (QAP). This study finds that (1) the level of urban digital economy in China shows a rising trend year by year and displays an uneven spatial distribution. (2) Spatial association networks of urban digital economy are relatively well-connected, with increasing density and stability of spatial associations, yet some hierarchical structure remains, and overall connectivity still needs to be improved. (3) Most cities in the east region occupy the core positions within the complex network, significantly influencing the overall complex network through a “siphon effect”, while cities in the central region play more of a “bridge” role in the spatial association network. In contrast, cities in the northwest, northeast, and southwest regions are situated on the periphery of this spatial association network. (4) The economic development level, informatization level, technological innovation, urbanization level, industrial structure, and human capital contribute to the formation of the spatial association network of the digital economy. Based on these conclusions, specific policy implications for the future development of the spatial association network of the urban digital economy are proposed. Full article

China’s rapid urbanization has driven significant economic growth, but has also resulted in resource depletion, ecological degradation, and inefficient land use, collectively hindering sustainable development. In response, pilot policies for “low-carbon cities” and “carbon emissions trading” have been implemented to enhance urban land use efficiency. This study evaluates the green land use efficiency of 282 prefectural-level cities in China from 2006 to 2023, using the non-expected output super-efficiency SBM model. Some cities serve as pilot sites for both “low-carbon cities” and “carbon emissions trading.” A multi-period Difference-in-Differences model is employed to empirically assess the impact and mechanisms of this “dual-pilot” policy on green land use efficiency. The findings indicate the following: (1) The dual-pilot policy significantly improves green land use efficiency, with coordinated implementation yielding greater efficiency gains than single-policy approaches. (2) Mechanism analysis suggests that these policies enhance efficiency by promoting technological innovation and industrial agglomeration. (3) Heterogeneity analysis reveals that the policy’s impact is stronger in western regions, cities with high human capital, large urban centers, areas with stringent environmental regulations, and non-resource-dependent cities. (4) Spatial econometric analysis shows that while low-carbon policies improve local land use efficiency, they also create a siphoning effect on neighboring areas, with positive impacts observed within a 100–600 km range, diminishing and turning negative beyond 600 km. These insights provide a valuable framework for sustainable urban planning, emphasizing the importance of adaptive, context-sensitive policy design in addressing complex ecological and economic challenges. Full article

Amidst climate change and the energy crisis worldwide, the synergy between smart city and environmental policies has become a key path to improving the green resilience of cities. This study examines the spatial effects of carbon emission trading (CET) policy on urban energy performance under the context of artificial intelligence (AI)-empowered smart cities. Using the spatial Durbin model (SDM) and analyzing data from 262 Chinese cities covering the period 2013–2021, the results reveal that: (1) smart cities significantly benefit from the institutional support of the local CET policy, resulting in an 8.55% reduction in energy consumption in the pilot city; (2) AI advancement contributes directly to reducing energy consumption in surrounding areas by 21.84% through spatial effects, and compensates for the imbalance of regional renewable energy caused by the “siphon effect” of CET policy. This study provides empirical evidence for developing countries to build green and resilient cities. This paper proposes the need to build a national CET market, strengthen government supervision, and make reasonable use of AI technology, transforming the green and resilient model of smart cities from Chinese experience to global practice. Full article

Agricultural green development is an essential pathway to achieving comprehensive agricultural and rural modernization and holds significant importance for ensuring national food, resource, and ecological security. Based on panel data from 30 provinces in China during 2004–2022, this study employed the super-efficiency SBM-GML model, the modified gravity model, social network analysis (SNA), and the quadratic assignment procedure (QAP) regression model to systematically analyze the spatial association network characteristics and driving mechanisms of agricultural green development in China. The results showed that (1) the number of spatial linkages in interprovincial agricultural green development had been increasing, with the network exhibiting strong connectivity, stability, and accessibility. (2) Major grain-producing areas and economically developed regions along the eastern coast had become the driving sources of spatial spillovers in agricultural green development. Meanwhile, the central and western regions acted as “brokers” in facilitating the reception and transfer of resources within the overall network, while municipalities such as Tianjin and Shanghai exhibited siphon effects on other regions. (3) Geographical proximity, government fiscal support, rural labor force size, progress in green technologies, and the agricultural economic development level significantly enhanced the spatial spillover effects of agricultural green development. However, regional disparities in agricultural industrial structures served as a key obstacle to realizing these spillover effects. Full article

Promoting green innovation is an important way to implement the dual carbon strategy and build an innovative country. Based on the panel data of 250 cities in China from 2011 to 2018, this paper constructs a two-way fixed-effect model, an intermediary effect model and a spatial Durbin model, and empirically studies the impact and mechanism of digital finance on urban green innovation. The results show that digital finance can improve the ability of urban green innovation, and its enabling effect mainly comes from improving the financial service model and improving the digital level. However, the role of digital finance in improving the efficiency of green innovation is not significant. Digital finance can promote urban green innovation by promoting the development of the Internet and alleviating the distortion of labor factors. A good environment for innovation will enhance the role of digital finance in promoting green innovation. Through further analysis, the spatial spillover effect of digital finance on green innovation at this stage is dominated by the siphon effect while the “trickle-down” effect is blocked. Full article

Global urbanization has caused enormous challenges that seriously threaten ecological security and the food system. Thus, there is a need for finding an optimal solution for the eco-efficiency of cultivated land use (ECLU) that can promote the development of new-type urbanization, while ensuring the sustainable utilization of limited cultivated-land resources. The quantitative system of multi-scale ECLU used in existing studies is inadequate; it is necessary to establish a measurement system from the perspective of geographical spatial relationship that uses evaluation as a key basis for management. In this study, we considered the Changchun Metropolitan Area and a representative urban–rural transition area as the target regions and customized new ECLU evaluation systems for different scales. The super slack-based measure and gravity and social network analyses methods were applied to evaluate the ECLU and explore the structural characteristics of its spatial association network. The average ECLU value for the Changchun Metropolitan Area was 0.974; the results indicated that most of the study area was eco-efficient. The value of ECLU for the urban–rural transition area varied from 0.022 to 1.323; thus, the highly efficient cultivated land was mainly distributed around the urban built-up area. The spatial association network of ECLU revealed that the overall spatial correlations were relatively weak, with a significant “bipolar” division of ECLU; furthermore, the network hierarchy and stability needed improvement. Moreover, we noted distant attraction capacity and siphoning effects outside regional boundaries. In the Changchun Metropolitan Area, it manifested as a monocentric radiation, with Changchun City as the center. In the urban–rural transition area, the cultivated land in proximity to the newly built urban area was more likely to experience spatial spillover. These findings have important implications for strengthening land-use management and advancing sustainable agricultural development for new-type urbanization. Our study can be used by policymakers and stakeholders to design sustainable urban cities, while improving land-use management and optimizing resource use. Full article

Nanoplastics are known to represent a threat to marine ecosystems. Their combination with other contaminants of emerging concerns (CECs) may amplify ecotoxic effects, with unknown impacts on marine biodiversity. This study investigates the effects, single and combined, of bisphenol A (BPA)—one of the most hazardous CECs—and polystyrene nanoparticles (PS NPs)—as a proxy for nanoplastics, being among the most commonly found asmarine debris—on cholinesterase (ChE) activities of the ascidian Ciona robusta. ChE activity was first measured in the siphons, tunic, and viscera of wild-caught adult specimens and exposed in vitro to BPA (0.01, 0.21, 0.69 mM) and PS NPs (0.0096–0.096 mM; 8.096 × 10⁹–10¹⁰ particles, respectively) alone and combined for 15 min of incubation. PS NPs’ behavior in milliQ water and in the ChE assay reaction buffer was characterized alone, combined with BPA, and analyzed through ζ-potential measurements via Dynamic Light Scattering. The results revealed that ChE activity was predominant in the viscera and siphons of C. robusta; PS NPs did not affect the ChE activity alone or combined, while BPA caused a concentration-dependent inhibition of ChE activity in the viscera. No changes in ζ-potential were observed for PS NPs alone or combined with BPA in the ChE buffer, suggesting no interaction. Further investigations are needed to understand the potential neurotoxic consequences for C. robusta and ecological risk scenarios due to exposure to BPA and nanoplastics in marine coastal waters. Full article

As a long lifeline system of buried structures, the utility tunnel (UT) is vulnerable to earthquake invasion. For utility tunnels with inverted siphon arrangements crossing rivers, the seismic response is more complex due to the basin effect of acceleration in the topography and the influence of fluctuating hydrodynamic pressure, but there is currently a gap in targeted seismic response analyses and references. Based on a UT project in Haikou, this paper studied seismic responses of a cast-in-place UT considering the coupled model of water–soil–tunnel structure on ABAQUS software. Herein, the dynamic fluctuation of hydrodynamic pressure is simulated using an acoustic–solid interaction model. A viscoelastic artificial boundary was used to simulate the soil boundary effect, and seismic loads were equivalent to nodal forces. Considering seismic invading direction and varying water elevation, this paper investigates the dynamic response characteristics and damage mechanisms of river-crossing utility tunnels. This study shows that the basin effect causes the soil acceleration around the UT to show variability in different sections, and the amplification factor of the peak acceleration at the central location is almost doubled. The damage and dynamic water pressure of the UT are intensified under bidirectional seismic excitation, and the damage location is concentrated at the junction of the horizontal section and the vertical section. Bending moments and axial forces are the main mechanical behaviors along the axial direction. Changes in river levels have a certain positive effect on the UT peak MISES, DAMAGEC, and SDEG, and it exhibits a certain degree of energy dissipation and seismic damping effect. For the aseismic design of cross-river cast-in-place utility tunnels, bidirectional seismic calculations should be performed, and the influence of river hydrodynamic pressure should not be neglected. Full article

Agricultural green development is crucial for achieving the United Nations 2030 Sustainable Development Goals, with the digital technology revolution acting as a catalyst for both China’s green agricultural transformation and global sustainable development efforts. This study utilizes panel data from 30 Chinese provinces (including autonomous regions and municipalities) from 2012 to 2022 to assess the digitalization level and agricultural green development through a combined entropy weight and TOPSIS method. It also investigates the spatial agglomeration of agricultural green development using Moran’s I index and empirically evaluates the impact of digitalization on agricultural green development through OLS and spatial Durbin models. The findings reveal that, while China’s agricultural green development has progressed slowly yet steadily during the study period, it demonstrates significant spatial agglomeration, driven primarily by agricultural production efficiency and resource recycling. Notably, a non-linear U-shaped relationship exists between digitalization and agricultural green development, suggesting that digitalization fosters agricultural green development only after surpassing a certain threshold. Additionally, digitalization has spatial spillover effects: advancements in neighboring provinces correlate with local agricultural green development in a U-shaped manner, with an initial “siphon effect” followed by a “trickle-down effect.” These insights inform policy recommendations aimed at optimizing the use of digital technology to facilitate green agricultural transformation, offering valuable guidance for policymakers. Full article

A resilient innovation ecosystem is an important guarantee for enhancing industrial competitiveness. Knowledge spillover is the key driving force to enhance system resilience. Firstly, we use the MEREC-CoCoSo method to calculate the resilience level of the integrated circuit (IC) innovation ecosystem and analyze the evolution trajectory of the resilience before and after the emergence of the “stuck-neck” problem. Secondly, based on the panel data of 30 provinces (autonomous regions and municipalities directly under the central government) in China from 2011 to 2021, this paper analyzes the mechanism of the impact of intra-regional knowledge spillovers on the resilience of IC innovation ecosystems using the fixed-effect model and analyzes the spatial effect of inter-regional knowledge spillovers on the resilience of innovation ecosystems using the spatial Durbin model under the human capital matrix. Finally, we analyze the regulating role of contractual and relational governance mechanisms and try to open the “black box” of governance. The result shows the following: (1) The polarization of innovative ecosystem resilience of integrated circuits is gradually increasing, with strong spatial agglomeration, high–high agglomeration, low–low agglomeration, and low–high dispersion, and there is an obvious “matthew effect” and “siphon effect”. (2) Both intra- and inter-regional knowledge spillovers contribute significantly to the resilience of IC innovation ecosystems. The contractual governance mechanism can effectively enhance the impact of knowledge spillovers on the resilience of innovation ecosystems in the region, and the relational governance mechanism has a positive impact on the resilience of innovation ecosystems in neighboring regions. (3) Heterogeneity results show that knowledge spillovers within the Pan-PRD region have a significant positive impact on innovation ecosystem resilience. Knowledge spillovers between regions with low innovation capacity have a double effect on innovation ecosystem resilience, and knowledge spillovers between regions with “talent highlands” have a facilitating effect on innovation ecosystem resilience. Accordingly, policy recommendations are put forward to open up channels for innovation knowledge spillover, realize effective allocation of innovation resources, and optimize the system of innovation talents. Full article

Ceramic and vitreous materials can be functionalized to exhibit biocidal activity. This research evaluates the biocidal properties of silver-modified vitreous microspheres designed to be included in water endpoints and siphons to prevent nosocomial diseases produced in hospital environments. The microspheres obtained from a coating and heat treatment process at 650 °C have been chemically and microstructurally characterized using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Wavelength Dispersive X-ray Fluorescence (WD-XRF), Scanning Electron Microscopy (FEG-SEM) and Energy-dispersive X-ray Microanalysis (EDS) to determine how silver particles are distributed in the glassy matrix and to relate their bactericidal capacity by means of leaching tests. Microbiological tests have been performed against microorganisms such as Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida auris. The results revealed that these silver-coated microspheres had significant bactericidal activity, with a significant reduction in the population of E. coli, C. auris, and P. aeruginosa, with no cytotoxic effect of these microspheres. Full article

Big data is a pivotal factor in propelling the digital economy forward and emerges as a novel driver in realizing the goals of carbon peaking and carbon neutrality. This study focuses on a quasi-natural experiment, namely national big data comprehensive pilot zones (NBD-CPZs), and employs a multi-period difference-in-differences (DID) model to identify the influence of big data on carbon emissions. The findings of this study are as follows. Overall, big data significantly reduces carbon emissions within the pilot zones. Mechanism analysis shows that big data reduces urban carbon emissions by promoting green innovation, optimizing energy structure, mitigating capital mismatch and improving public awareness of environmental protection. Heterogeneity analysis shows that the carbon reduction effect of big data are more pronounced in cities with high levels of digital economy, non-resource-based cities, cities with strong intellectual property rights protection and the Guizhou Province. Spatial effect analysis indicates that within a radius of 400–500 km, the NBD-CPZ increases urban carbon emissions, signifying a significant siphoning effect; within a radius of 500–900 km, the NBD-CPZ reduces urban carbon emissions, signifying a significant spillover effect, and beyond a distance of 900 km, the spatial effect of the NBD-CPZ is not significant. Based on the above conclusions, this study puts forward several policy recommendations to effectively exert the carbon emission reduction effect of big data. Full article

Guizhou is a typical mountainous province and is also one of the lowland regions in China that has attracted a population influx. Here, using population density data from 2000 to 2020 as the basic dataset and the coefficient of variation method and standard deviation ellipse analysis, we investigated the spatial characteristics across different years. The results show: Firstly, Guizhou’s population has a distinct spatial distribution, characterized by a lower population density in the southeast and a higher density in the northwest as well as an increasing polarization of population concentration toward the centers of prefecture-level cities and provincial capitals. Fluctuations in population density resemble a central siphon effect, which is particularly pronounced in the provincial capital and show a significant gravitational pull. Secondly, the coefficient of variation in population density across Guizhou’s counties is spatially divided by Guiyang, showing higher values in the east and lower values in the west. Furthermore, the ellipse of the standard deviation of population density is gradually shrinking, indicating an increasingly concentrated population distribution. Thirdly, the explanatory power of the population and socio-economic systems on the population distribution in Guizhou is significantly greater than that of the natural systems. Population distribution and migration patterns have shifted from purely “economic driven” to coexisting with “economic and comfort-oriented” trends, and there is an urgent need to improve the comfort level of public services as a typical supply, in order to boost Guizhou’s population attraction. Full article