Search Results (194)

To reveal the influence mechanisms of seasonal climatic factors (wind speed, wind direction, temperature) and leakage direction on hydrogen dispersion and explosion behavior from single-source leaks at typical risk locations (hydrogen storage tanks, compressors, dispensers) in hydrogen refueling stations (HRSs), this work established a full-scale 1:1 three-dimensional numerical model using the FLACS v22.2 software based on the actual layout of an HRS in Xichang, Sichuan Province. Through systematic simulations of 72 leakage scenarios (3 equipment types × 4 seasons × 6 leakage directions), the coupled effects of climatic conditions, equipment layout, and leakage direction on hydrogen dispersion patterns and explosion risks were quantitatively analyzed. The key findings indicate the following: (1) Downward leaks (−Z direction) from storage tanks tend to form large-area ground-hugging hydrogen clouds, representing the highest explosion risk (overpressure peak: 0.25 barg; flame temperature: >2500 K). Leakage from compressors (±X/−Z directions) readily affects adjacent equipment. Dispenser leaks pose relatively lower risks, but specific directions (−Y direction) coupled with wind fields may drive significant hydrogen dispersion toward station buildings. (2) Southeast/south winds during spring/summer promote outward migration of hydrogen clouds, reducing overall station risk but causing localized accumulation near storage tanks. Conversely, north/northwest winds in autumn/winter intensify hydrogen concentrations in compressor and station building areas. (3) An empirical formula integrating climatic parameters, leakage conditions, and spatial coordinates was proposed to predict hydrogen concentration (error < 20%). This model provides theoretical and data support for optimizing sensor placement, dynamically adjusting ventilation strategies, and enhancing safety design in HRSs. Full article

To explore the integration efficiency of ecology, culture and tourism in China, this study uses a Super-Efficiency SBM model with undesirable outputs to measure integration efficiency, employs kernel density estimation (KDE) to analyze dynamic spatial distribution characteristics, applies the standard deviational ellipse (SDE) to examine the migration trend of the spatial agglomeration center of gravity, and uses Tobit regression to identify spatiotemporal influencing factors. The findings show that: the national integration efficiency presents a trend that first decreases and then increases, with North and South China having relatively high integration efficiency. The national integration efficiency has gone through three stages: narrowing differences, coexistence of slow efficiency, and gradient effects, and increasing efficiency with weakened multipolarization. The degree of spatial agglomeration has gradually increased, and the center of gravity has shifted eastward as a whole. The internal gaps in East and South China have expanded, while the internal balance in North China has improved; the internal differences in other regions have narrowed. The influencing factors of integration efficiency have shifted from traditional economy-led to innovation and institutional collaboration. Economic development level and market openness have a positive impact on the overall integration efficiency, while transportation conditions show a restraining effect. Full article

Return migration is frequently associated with failure, particularly in the context of women returnees from the global south. This research challenges this notion, focusing on women returnees from Italy to North Africa. It aims to analyze return migration by focusing on women who returned to Morocco and Tunisia in the last 15 years, and the aftermath of the Arab uprisings, emphasizing the transformative potential of migration experiences for themselves and the local community. Women returnees not only redefine their roles in society but also foster socio-economic development, community building, and political changes in the countries of return. The study employs thematic analysis to examine 25 semi-structured interviews conducted with returnees aged 25–60, where women shared insights into their migration, re-adaptation experiences, and challenges upon return. Returnees utilized skills gained abroad to achieve economic empowerment, often starting businesses or finding new jobs. However, they faced cultural challenges, particularly societal expectations of traditional gender roles. Nonetheless, migration empowered many returnees to question these policies and norms, and contribute to societal change. Full article

To investigate the erosion and deposition evolution characteristics of the Xinqiman–Kelelik reach along the main stem of the Tarim River, this study analyzed river channel dynamics and planform morphological changes using Landsat satellite imagery (1993–2024) and hydrological data (water discharge and sediment load) from gauge stations. The results show that the thalweg line swings indefinitely in the river. The thalweg length increased by 29 km, while the mean channel width decreased by 0.28 km. The sinuosity index rose from 1.95 to 2.34, indicating a gradual intensification of channel curvature. The north bank is in a state of siltation, while the south bank is in a state of erosion. The riverbank exhibited an overall southward migration. The farmland area in the study area increased from 1510 hectares in 1993 to 5140 hectares in 2024. During this period, the thalweg near the water-diversion sluice continuously shifted toward the sluice side. To ensure flood protection safety for farmlands and villages on both banks, as well as ecological water diversion, river channel regulation and channel pattern control should be implemented. Full article

Phosphorus plays a key role in water eutrophication. The release of endogenous phosphorus from sediments maintains eutrophication in Dianchi Lake. This study aimed to summarize and analyze the research trends, occurrence characteristics, adsorption and release characteristics, influencing factors, and prospects of internal phosphorus pollution control in Dianchi Lake based on a literature search and data integration. The results revealed that sediment phosphorus in Dianchi Lake has been widely studied. From previous studies, the total phosphorus (TP) content and various forms of phosphorus in the Dianchi Lake sediments have decreased since 2010. The TP contents measured in Dianchi Lake in previous research were considerably different owing to the influence of sampling depth and dredging projects. The TP content in the sediments of Dianchi Lake was higher but its release risk was lower than those in other lakes in China. The risk of release was higher in Caohai and North Waihai than that in Central Waihai and South Waihai. In addition to environmental factors at the sediment–water interface, sediment characteristics, and ecosystem degradation are important factors that affect phosphorus migration and transformation. Over the past 30 years, sediment dredging has been the primary measure for reducing the internal pollution load in Dianchi Lake. However, more accurate sediment dredging and systematic vegetation–algae–sediment co-management measures are needed for water ecosystem restoration in Dianchi Lake. This study provides new insights into the study of internal phosphorus pollution. Full article

Amidst the backdrop of rural population decline and the inefficient expansion of construction land, traditional land management models are confronted with the dual challenges of supply–demand mismatch and low efficiency. This paper constructs a three-dimensional analytical framework based on decoupling types, development potential, and driving mechanisms. Initially, using Tapio’s decoupling theory, the study identifies the population–land decoupling types among 224 villages in Yanggao County, Shanxi Province, Northern China. It then evaluates the development potential of rural construction land using a comprehensive index system, and a linkage analysis between the two is conducted. Finally, the study employs the Logarithmic Mean Divisia Index (LMDI) method to conduct an in-depth analysis of the mechanisms driving changes in rural construction land. The results indicate the following: (1) Between 2010 and 2020, the study area exhibited a reverse evolution characterized by rural population loss and the expansion of construction land, with a significant “population–land decoupling” phenomenon. (2) The development potential for rural construction land shows a pattern of being high in the north and south, low in the middle, high in mountainous and hilly areas, low in plains, and high in peripheral areas but low in town centers. (3) Villages in Yanggao County are predominantly of the resource reserve type (49.11%), indicating relatively abundant land resource reserves. (4) In different population migration patterns, the reduction in land-use efficiency represents similar proportions (38% and 36%), with villages experiencing net population inflow performing better in improving land-use efficiency compared to those with net population outflow. Drawing on international governance experiences, the study proposes classification and phased implementation pathways. By revealing the dynamic patterns of rural population–land relationships—construction land potential and change mechanisms—the logic of regulatory path adaptation, the article provides a methodological paradigm for constructing a precise and differentiated land resource allocation system, promoting the transition of rural spatial governance from expansion in scale to an improvement in quality. Full article

Fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae), is a major pest in the U.S. and has spread globally, causing severe agricultural losses in different countries. Due to its high mobility and potential for long-distance dispersal, understanding FAW migration is a key tool for forecasting outbreaks and implementing timely management measures. Recent studies using stable hydrogen isotopes indicated reverse (southward) migration of Helicoverpa zea Boddie (Lepidoptera: Noctuidae). Here, we tested the reverse migration hypothesis for FAW in North America. Estimation of the hydrogen isotopic ratio on 324 samples collected in Florida, an intermixing zone at the edge of the continental U.S., indicated evidence of reverse migration in samples of FAW moths. They showed a high probability of origin from the U.S. Corn Belt, with a greater probability of origin in Nebraska, South Dakota, Minnesota, Kansas and Wisconsin. This southward movement provides new insights into the risk of spreading pesticide resistance alleles in this species to southern regions and contributes to the improvement of integrated pest management and insect resistance management programs. Full article

Tributaries to meandering rivers rarely join the river on the interior of bends. The limited drainage area on bend interiors explains why tributaries seldom form there, but not why existing tributaries are redirected as meanders develop. Other relevant factors include flow dynamics at junctions, runoff partitioning on inner vs. outer bends, and tributary deflection as the main channel migrates laterally. This study investigated whether the lack of confluences on bend interiors applies to lower coastal plain rivers in South and North Carolina, USA, where the factors above are not necessarily active, and if so how tributaries at sites of developing meanders are redirected. Of the 121 confluences examined using GIS data supplemented with field observations, none occurred on meander bend interiors. A total of 17 cases of potentially deflected tributaries were identified. Of these, 11 had sufficient evidence for a confident interpretation of how redirection occurred. In all 11 cases, pre-bend river paleochannels were involved in redirecting the tributaries away from the bend interior. This is explained by a model showing that the local slope gradient and mean depth advantages of the paleochannels provide velocity, stream power, and shear stress advantages over extension of the tributary channel into the bend interior. The results illustrate the importance of local hydraulic selection, and the influence of antecedent morphology on river hydrology and geomorphology. Full article

Species migration or extinction events may occur on a large scale with the intensification of climate change. Plant Species with Extremely Small Populations (PSESP) are more sensitive to climate change as compared to other plants. To date, the potential effect of climate change on Acer yangbiense and Cinnamomum chago, both of which belong to PSESP, remain unknown. In this study, we modeled the distribution dynamics of A. yangbiense and C. chago spanning from the Last Glacial Maximum (LGM) to the end of the 21st century based on the MaxEnt model, optimized using the Kuenm package. The results revealed that the parameter settings of the optimal models were RM (regularization multiplier) = 3.5, FC (feature combination) = QP, and RM = 2, FC = QPT. A. yangbiense and C. chago had AUCs of 0.982 and 0.993, respectively, indicating that the model predictions are highly accurate while effectively balancing complexity and avoiding overfitting. The distribution of A. yangbiense and C. chago was mostly influenced by the precipitation of the driest quarter (bio17) and the min temperature of the coldest month (bio6). From the LGM to the present, the total suitable areas of A. yangbiense and C. chago initially declined before showing a subsequent increase, but it is projected to experience significant reductions in the future, with decreases of 32.98%–64.99% and 63.48%–99.49%, respectively. The distribution centroids of A. yangbiense and C. chago showed a migration trend from south to north from the LGM to the present, and this trend is expected to continue. To enhance the resilience of A. yangbiense and C. chago to meet the challenges of climate change in the future, we proposed that the introduction and artificial cultivation of these species should be carried out in Baoshan, Dali, and Nujiang in the northwest of Yunnan Province, which were the areas with high heat values, so as to expand the populations gradually. Full article

The Ascomycete genus Cordyceps affects plant crops significantly, filling an important ecological niche. Cordyceps militaris (L.) Fr. presents many health benefits for humans, but its population history has not been reported. The objective of this research was to report the collection, population structure, demographic history, diversity, and cytosine deaminases of 43 wild strains of C. militaris in China through resequencing using an Illumina HiseqTM platform. All strains were assigned to the warm, subtropical, and middle temperate zone populations, confirmed by ADMIXTURE-1.3.0, PCA, and phylogenic analysis. Their population sizes declined historically, suggesting that this species suffered from bottlenecks in the wild. LD decays (r²) revealed a north-to-south migration pattern of wild C. militaris, consistent with the MSMC2-v2.1.4 analysis. The regions of high Pi were aggregating at the chromosomes CP023325.1 (51) and CP023323.1 (9), playing a key role in adaptation, especially for the sites on cytosine deaminase. Within the species, genetic differentiation was relatively high among the three populations (F_st = 0.083, 0.092, and even 0.109). According to the artificial intelligence-assisted (RoseTTAFold) predicted structures of the cytosine deaminases, they were classified into eight clades with unique, distinct, and structurally conserved domains, offering a potential suite of single- and double-stranded deaminases of great promise as tunable base editors for therapeutic and agricultural breeding applications. These provided new insights for mining novel proteins from macrofungi, structurally and functionally. Full article

Accurately measuring the characteristics of spatial clusters and changes in urban land surface temperature (LST) provides essential data that assist in urban heat island effect mitigation and sustainable urban development. Previous studies on the thermal environment often focused on the identification and spatial distribution of land surface temperature values and the lack of quantitative research on the LST spatial cluster characteristics, making it difficult to determine where mitigation strategies can be best applied to reduce high-temperature cluster (HH) areas and increase urban low-temperature cluster (LL) areas. Based on remote sensing (RS) images and geographic information system (GIS) technology, the cluster classification and spatial cluster characteristics analysis methods were used in this research to quantitatively assess the LST spatial cluster characteristics in Huaiyin District, Jinan City in 2000, 2005, 2010, 2015, 2020, and 2024. The results show the following: (1) The LST exhibited significant spatial cluster characteristics, with a strong correlation between the LST spatial cluster areas and their spatial locations. The spatial distributions of the HH and LL areas showed contrasts from north to south and west to east. (2) Decreasing temperature transformations were mainly located in new areas covered by water bodies and vegetation, while increasing temperature transformations were mainly located within re-developed built-up areas in the old urban area and in the newly built urban growth areas. The HH areas were larger, simpler in patch shape, and had more aggregated spatial distributions than the LL areas. Additionally, the barycentre distribution and migration trajectory of the HH areas were closely related to urban development planning. These quantitative results provide a scientific basis for understanding the urban LST spatial cluster characteristics, thus quantifying the core problem areas of urban planning and thermal environment regulation policies. Full article

The Changling Depression, located in the southern part of the central depression zone of the Songliao Basin, is characterized by complex structures and has been shaped by multiple phases of tectonic activity. The strata in this region have undergone significant uplift and denudation, resulting in an incomplete understanding of the prototype basin and hindering progress in oil and gas exploration. To better understand the geological characteristics and exploration potential of the Changling Depression, this study begins with the reconstruction of denudation amounts. Using the stratigraphic trend extrapolation method, the denudation of strata during the faulting period of the Changling Depression is quantified. By combining the denudation thickness with the remaining strata thickness, the original strata thickness is restored. Employing MOVE 2018version and Petrel 2021version software, the paleogeomorphology of different geological periods is reconstructed. Through an analysis of the prototype basin’s structure, its evolution history, sedimentary filling patterns, and paleogeomorphological features, it is determined that the maximum depositional thickness and rate during the Huoshiling period occurred in the Shenzijing, Heidimiao, and Fulongquan areas, with strong central deposition that weakened toward the north and south. During the Shahezi period, depositional thickness and rates exhibited a pattern of weaker deposition in the south and stronger in the north. In the Yingcheng Formation–Denglouku Formation period, the basin entered a subsidence phase, with an expanded range of strata subsidence. During the Denglouku period, the Qianbei area experienced strong deposition, while the Heidimiao area saw even more pronounced deposition; in contrast, the Shenzijing area displayed very weak depositional activity. The study reveals a south-to-north migration of lateral subsidence centers over time, influenced by left-lateral tectonic forces, reflecting a shift in the dominant influence pattern. These findings clarify the morphology of the prototype basin and the distribution and migration of subsidence centers across different periods, providing valuable insights that will facilitate deeper oil and gas exploration efforts in the Changling Depression. Full article

Seismic data reveal that the shelf edge of the Pearl River Mouth Basin in the northern South China Sea is characterized by slope channels that have consistently migrated in a north-easterly direction over millions of years. Previous research suggests that the channel migration is driven by the interplay between along-slope bottom currents and downslope turbidity currents. Here, we propose an alternative interpretation, suggesting the migrating channels are actually a series of channel–levee systems and the migration is driven by their own evolution of erosion–deposition under the influence of the Coriolis force. A detailed interpretation of high-resolution seismic data reveals seven types of architectural elements, characteristic of channel–levee systems, which are erosional bases, outer levees, inner levees, channel-axis fills, marginal slumps, drapes, and lobes. An analysis of the sequence stratigraphy and stacking pattern of channels suggests that channel migration from the middle Miocene to the present is discontinuous with at least three regional discontinuities within the channel migration sequence marked by regional drapes. Down-dipping reflections along the margin of channels, previously interpreted as bottom-currents deposits, are here reinterpreted as mass-transport processes along steep channel walls. The migration is most prominent in the middle reach, where erosion and deposition coexist and dominate alternately in two different phases. During the long-term canyon-filling turbidity currents prevailing phase, deposition dominates, leading to the development of a prominent asymmetric right-hand (west) inner levee due to the Coriolis force. In contrast, during the canyon-flushing turbidity currents prevailing phase, erosion dominates and the preferred right-hand (west) inner levee enforces the flow to erode eastward, then drives the channel migrating eastward. The alternating effects of erosion and deposition ultimately result in unidirectional channel migration. Full article

Quinoa (Chenopodium quinoa, Amaranthaceae) is a pseudocereal native to the Andes of South America that contains high protein content and adequate nutrient levels. Peru possesses an abundant morphological diversity of quinoas and is among the top producers and exporters worldwide of this precious crop. However, knowledge about the genetic and population components of quinoa from the Peruvian Andes is still limited. Here, we used 13 microsatellite markers to determine the genetic diversity and population structure of 105 landraces of quinoa cultivated in 11 provinces of Ayacucho, the southern Peruvian Andes. A total of 285 bands were manually scored, generating a 105 × 285 presence/absence data set. Principal coordinate analysis, similar to a dendrogram using the UPGMA clustering algorithm, showed that quinoa from Ayacucho is grouped into three clusters without a clear geographic component. Estimation of the genetic diversity indices was conducted considering the three populations (C1: south 1, C2: south 2, C3: north) determined by STRUCTURE analysis, showing mean expected heterozygosity was 0.08, which may be attributed to high rates of inbreeding and genetic drift, as Ayacucho suffered decades of sociopolitical violence, promoting the migration of farmers. The highest population divergence (F_ST) was exhibited for C2 and C3 (0.03), whereas the lowest was for C1 and C3 (0.02). Analysis of molecular variance revealed the greatest variation within populations (80.07%) and indicated that variability between populations is 19.93%. Microsatellite markers were effective; however, more studies of the genetic components of quinoa from other Peruvian Andean localities are still needed. We expect that this work will help pave the way towards the development of modern breeding programs of quinoa in Peru, with accurate strategies for the conservation of this nutritious crop. Full article

The alpine steppe has an important place in alpine ecosystems, and its distribution pattern is strongly influenced by climate change. In this study, we used “biomod2” and “FragStats 4.2” to calculate the migration trends and the habitat fragmentation of three S. purpurea alpine steppes on the western Tibetan Plateau. The results of this study show that the Stipa purpurea-Ceratoides compacta alpine steppe, the Stipa purpurea-Carex moorcroftii alpine steppe, and the Stipa purpurea-Carex montis-everestii alpine steppe are strongly influenced by climate, while other variables have less impact. Their main influence factors are annual precipitation (Bio12), precipitation of the warmest quarter (Bio18), and precipitation of the coldest quarter (Bio19), respectively. The effects of carbon emissions on the suitable habitats of all three S. purpurea alpine steppes are significant in future scenarios. Continued increases in carbon emissions will lead to a continuous reduction in their suitable habitat areas. These communities are bounded by 33° N. South of the boundary, steppe communities are influenced by mountain ranges and show a tendency to migrate to higher elevations in a southward direction. North of the boundary, steppe communities show a tendency to migrate to higher elevations in a northward direction. Climate change reduces community aggregation, leading to gradual habitat fragmentation. The findings of this study provide a scientific basis for the migration and conservation of three S. purpurea alpine steppes on the western Tibetan Plateau, thereby contributing to the improvement of ecosystem stability and species diversity. Full article