Search Results (3,256)

Functioning as a critical ecotone between terrestrial and aquatic ecosystems, riparian zones exhibit soil enzyme activities that serve as key biomarkers of their nutrient cycling processes. However, despite considerable focus on riparian soil properties, the dynamics and underlying drivers of these enzymatic activities are not yet fully characterized. To this end, soils were systematically sampled across varying widths and depths from three representative riparian zones to quantify the driving forces of physicochemical properties on enzyme activity dynamics. The results showed that the soil enzyme activity was highest in the forest riparian zone and lowest in the farmland riparian zone, with average enzyme activities of 37.95 (μmol·g⁻¹·h⁻¹) and 26.85 (μmol·g⁻¹·h⁻¹), respectively. The width of the riparian zone changes the spatial distribution of soil enzyme activity. The soil enzyme activity is higher in the land edge area far from the river (profile-1) and lower in the water edge area near the river (profile-4), with average enzyme activities of 47.4384 (μmol·g⁻¹·h⁻¹) and 17.0017 (μmol·g⁻¹·h⁻¹), respectively. Moreover, soil water content (SWC) has a strong impact on enzyme activity changes. The increase in soil depth reduces soil enzyme activity, with enzyme activity in the 0–20 cm soil layer being 1.5 times higher than in the 20–50 cm soil layer. Meanwhile, the primary factors influencing changes in soil enzyme activity have gradually shifted from total nitrogen (TN), nitrate nitrogen (NO₃-N), and soil organic carbon (SOC) to the sole control of SOC. Research has shown that human influence strongly interferes with soil enzyme activity in riparian zones. The width of the riparian zone and soil depth serve as key drivers of the spatial distribution of soil enzyme activity by modulating soil environmental factors. The patterns revealed in this study indicate that maintaining appropriate riparian zone width and reducing anthropogenic disturbances can enhance nutrient cycling dynamics at the micro-scale by increasing soil enzyme activity. This process is crucial for strengthening the riparian zone’s macro-level ecosystem services, particularly by effectively enhancing its capacity to sequester and transform nutrients like nitrogen and phosphorus from agricultural nonpoint sources, thereby safeguarding downstream water quality. Consequently, soil enzyme activity serves as a key indicator, providing essential scientific basis for assessing riparian health and guiding ecological restoration efforts. Full article

As styrene–butadiene rubber (SBR) is widely used and tends to age, the performance improvement in aging resistance is greatly important to rubber industrial fields. To this end, this study considered using layered double hydroxides (LDHs) as inorganic fillers and subsequently modified them by silane coupling agent KH−580 to obtain organically functionalized LDHs (m−LDHs) for solving the compatibility and aging concerns. The modified fillers were incorporated into styrene–butadiene rubber (SBR) to prepare m−LDHs/SBR composites. To evaluate their aging resistance, both SBR and m−LDHs/SBR samples were subjected to ultraviolet (UV) accelerated aging tests. Comprehensive characterizations were carried out using Fourier−transform infrared spectroscopy (FT−IR), thermogravimetric analysis (TGA), and standard mechanical property testing. FT−IR confirmed the successful grafting of KH−580 onto LDHs surfaces, while TGA demonstrated a ~50 °C increase in decomposition temperature of the modified SBR compared to the pristine sample, indicating enhanced thermal stability. Mechanical performance, including tensile strength, elongation at break, and hardness, was better retained in m−LDHs/SBR after aging, revealing the role of m−LDHs as both UV shielding and interfacial reinforcing agents. These findings highlight the potential of surface−functionalized LDHs as multifunctional fillers to enhance the durability and service lifetime of rubber materials. Full article

The mechanical integrity of shipbuilding steel under demanding maritime service conditions is a pivotal factor for ensuring the structural safety and operational longevity of vessels. This research employs laser shock peening (LSP) to augment the surface performance of AH32 steel and carries out a comprehensive analysis of the influence and underlying mechanisms of LSP on both the microstructural evolution and mechanical properties of the material. The results indicate that the LSP treatment successfully introduced a high magnitude residual compressive stress (−162 MPa) at the surface of AH32 steel. Additionally, the surface hardness of LSP-1 and LSP-2 increased by 7.3% and 14.7%, respectively. The tensile test results indicate that Sample LSP-2 achieved a 25.8% improvement in elongation while exhibiting only a 5.9% reduction in ultimate tensile strength. Friction and wear tests demonstrated that the average coefficient of friction for the samples treated with LSP decreased by approximately 18%, while the wear rate reduced significantly by over 40%. Full article

This study quantifies shear and flexural stiffnesses and their changes over time to support structural health monitoring of in-service bridge superstructures across four girder types: reinforced concrete (RC) beams, prestressed concrete (PSC) girders, steel girders, and ultra-high-performance concrete (UHPC) sections, using field ambient vibration testing. A total of 20 bridges across Georgia and Iowa are assessed, involving over 100 hours of on-site data collection and traffic control strategies. Results show that field-measured natural frequencies differ from theoretical predictions by average of 30–35% for RC, and 20–25% for PSC, 15–25% for steel and 2% for UHPC, reflecting the complexity of in situ structural dynamics and challenges in estimating material properties. Site-placed RC beams showed stiffness reduction due to deterioration, whereas prefabricated PSC girders maintained consistent stiffness with predictable variations. UHPC sections exhibited the highest stiffness, reflecting superior performance. Steel girders matched theoretical values, but a span-level test revealed that deck damage can reduce frequencies undetected by localized measurements. Importantly, vibration-based measurements revealed reductions in structural stiffness that were not apparent through conventional visual inspection, particularly in RC beams. The research significance of this work lies in establishing a portfolio-based framework that enables cross-comparison of stiffness behavior across multiple girder types, providing a scalable and field-validated approach for system-level bridge health monitoring and serving as a quantitative metric to support bridge inspections and decision-making. Full article

Polyurethane (PU), owing to its superior physicochemical properties, is considered an ideal modifier for asphalt. To improve the mechanical performance and service durability of asphalt pavements, PU-modified asphalts with varying dosages were prepared and evaluated through laboratory experiments and molecular dynamics simulations. Rheological, thermodynamic, and mechanical tests, as well as asphalt–aggregate adhesion energy calculations, were conducted to elucidate the modification mechanism, aging resistance, and interfacial behavior. The results showed that PU incorporation significantly enhanced rutting resistance at high temperatures, flexibility at low temperatures, and overall load-bearing capacity. Under ultraviolet and long-term aging, PU-modified asphalts exhibited notably lower performance degradation than base asphalt. At the molecular level, PU absorbed light fractions and formed a cross-linked network, reducing the free volume fraction and strengthening resistance to deformation. Moreover, PU substantially improved asphalt–aggregate adhesion energy, thereby reinforcing interfacial bonding. These findings provide theoretical insights and practical guidance for the optimal design and engineering application of PU-modified asphalt. Full article

Human-driven land use change and intensification is a major threat to global biodiversity. High levels of land management intensity may reduce species diversity, change the composition and structure of plant and animal communities and disrupt ecological processes. However, there is still scarce information on the impacts of land management intensity on island pollinator communities and their interactions with plants. Here, we aim to assess how different land use types (natural vegetation, semi-natural pastures, and intensive pastures), representing a gradient of grazing intensification, influence pollinator diversity and plant–pollinator interactions on Terceira Island (Azores). We surveyed 30 sites (10 per land use) and recorded 1453 visits by 41 pollinator species. Alpha diversity did not differ among land uses, but grazing intensification reduced the abundance of several native species while favoring some exotics, such as the honeybee. Network analyses showed changes in structural properties and declines in interactions between native species with increasing grazing disturbance. Introduced species, particularly the honeybee, dominated interactions in intensively managed habitats, replacing native species from key ecological roles. Our findings highlight the vulnerability of island ecosystems to grazing intensification and emphasize the need for conservation measures in the Azores, namely the reduction in grazing intensity, restoration of habitat connectivity, and implementation of pollinator-friendly agri-environmental schemes to enhance native biodiversity and sustain ecosystem services. Full article

This study explores the influence of vibration timing on the performance of high early-strength cement-based composites used in bridge wet joints. A series of experimental techniques, including SEM, MIP, and RCM tests, were employed to evaluate microstructural evolution, mechanical properties, and durability. The results indicate that vibration applied between the initial and final setting phases has a critical impact, significantly reducing early-age compressive, flexural, and bond strengths. This deterioration is mainly attributed to micro-crack formation and enhanced pore connectivity, as confirmed by SEM and MIP analyses. Moreover, vibration markedly increases the chloride diffusion coefficient, particularly in mixtures with higher water-to-binder ratios, thereby raising long-term durability concerns. These findings underscore the necessity of optimizing mix proportions and strictly controlling vibration timing to ensure both the mechanical performance and service life of high early-strength cement composites in bridge construction. The study provides practical insights for the design and application of durable, resilient bridge wet joints. Full article

High-entropy boride (HEB) ceramics combine ultra-high melting points, superior hardness, and compositional tunability, enabling service in extreme environments; however, difficult densification and limited fracture toughness still constrain their aerospace applications. In this study, metallic Ta was introduced into high-entropy (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂ as both a sintering aid and a toughening phase. Bulk HEB-Ta composites were fabricated by spark plasma sintering to investigate the effect of Ta content on densification behavior, microstructure, mechanical properties, and high-temperature oxidation resistance. The results show that an appropriate amount of Ta markedly promotes densification; at 10 vol% Ta, the open porosity reaches a minimum of 0.15%. Hardness and fracture toughness exhibit an increase-then-decrease trend with Ta content, attaining maxima at 15 vol% Ta (20.79 ± 0.17 GPa and 4.31 ± 0.12 MPa·, respectively). During oxidation at 800–1400 °C, the extent of oxidation increases with temperature, yet the composite with 10 vol% Ta shows the best oxidation resistance. This improvement arises from the formation of a viscous, protective Ta₂O₅-B₂O₃ glassy layer that effectively suppresses oxygen diffusion and enhances high-temperature stability. Overall, incorporating metallic Ta is an effective route to improve the manufacturability and service durability of HEB ceramics, providing a composition guideline and a mechanistic basis for simultaneously enhancing densification, toughness, and oxidation resistance. Full article

In Africa, the folkloric practices involving plant-based remedies play a crucial role in livestock farming, often attributed to the limited access to modern veterinary services. The use of Acacia species (including those reclassified as Vachellia species) in ethnoveterinary medicine has garnered increasing interest due to their high protein content and medicinal (including anti-parasitic) properties, offering a sustainable source of fodder particularly in arid and semi-arid regions. However, scientific assessment of their efficacy and safety remains limited. This systematic review examines the ethnoveterinary uses, biological efficacy and safety of Acacia species across Africa. A literature search was conducted using PubMed, Google Scholar and Scopus, yielding 519 relevant studies published between 2001 and 2024. After applying the inclusion and exclusion criteria, 43 eligible studies were analyzed based on their relevance, geographical location and livestock disease applications. Plants of the World online database was used to validate the names of the species and authority. Ethiopia had the highest usage of Acacia species (25%), then Nigeria (20%) followed by both South Africa (15%) and Namibia (15%). Vachellia nilotica (Acacia nilotica) was the most frequently cited species (26.3%), followed by Vachellia karroo (Acacia karroo) (15.8%). Ethnobotanical records indicate that the different Acacia species have been traditionally used to treat conditions such as diarrhea, wound infections and complications such as retained placenta. Pharmacological studies corroborate the therapeutic benefits of Acacia species with evidence of their antimicrobial, anti-inflammatory, antioxidant and anthelmintic effects, though some toxicity concerns exist at high dosages. The systematic review revealed the efficacy and safety (to some extent) of Acacia species in livestock disease management, emphasizing their potential integration into veterinary medicine. However, the dearth of in vivo studies underscores the need for pre-clinical and clinical trials to establish safe and effective dosages for use in livestock. Full article

This study offers a quantitative performance assessment of integrated seismic retrofit designs applied to an in-service 1960s reinforced concrete school structure in Central Italy. The research combines in-depth experimental material characterization with complex numerical simulations in order to estimate both the independent and interaction effects of external steel exoskeletons in conjunction with localized CAM (Cucitura Attiva dei Materiali) strengthening. The experimental investigation includes extensive material characterization through core drilling and non-destructive pacometric inspections to accurately define the existing concrete properties. The numerical analysis is performed with Finite Element modeling to estimate four different structural conditions: the original state, the condition with static strengthening, the condition with additional steel exoskeletons, and the condition with both exoskeletons and localized CAM reinforcements. The results quantitatively estimate the specific performance gains from the individual retrofit strategies. The steel exoskeletons show effective reduction in inter-story drifts but negligible effect on strength-oriented failure mechanisms. Localized CAM strengthening therefore stands out as necessary in reaching adequate safety levels in all the failure mechanisms. Economic analysis reveals that while steel exoskeletons provide the major cost component, the integrated approach with localized strengthening is essential for achieving comprehensive seismic safety enhancement. Full article

Current understanding of the load-transfer mechanism in the skeletal contact state of asphalt mixtures and its influence on macroscopic mechanical properties remains insufficient. This knowledge gap leads to difficulties in accurately predicting the performance of designed mixtures, thereby restricting the service life of asphalt pavements and the sustainable development of road engineering. This study investigated the skeletal contact characteristics, coarse aggregate movement, and crack propagation of three asphalt mixture types—Stone Mastic Asphalt (SMA), Asphalt Concrete (AC), and Open-Graded Friction Course (OGFC)—under loading. The methodology incorporated Computed Tomography (CT) technology, a Voronoi diagram-based skeletal contact evaluation method, and discrete element numerical simulation. The research aimed to elucidate the influence mechanisms of different skeletal structures on macroscopic performance and to validate the efficacy of the skeletal contact evaluation method. The findings revealed that under splitting load, the tensile stress contact force chains within the asphalt mixture’s skeleton were predominantly distributed along both sides of the specimen’s central axis. For all three gradations, compressive stress contact force chains (points) accounted for over 65% of the total, indicating that the asphalt mixture skeleton primarily bore and transmitted compressive stresses. The interlocking structure formed by coarse aggregates significantly enhanced the stability of the asphalt mixture skeleton, reduced its displacement under load, and improved the mixture’s resistance to cracking. In the three gradations, shear stress-induced cracks outnumbered those caused by tensile stress, with shear stress cracks accounting for over 55% of the total cracks. This suggests that under splitting load, cracks resulting from shear failure were more prevalent than those from tensile failure. SMA-20 demonstrated the best crack resistance, followed by AC-20, while OGFC-20 performed the poorest. These conclusions are consistent with the results of the Voronoi diagram-based skeletal contact evaluation, confirming the correlation between the contact conditions of the asphalt mixture skeleton and its mechanical performance. Specifically, inadequate skeletal contact leads to a significant deterioration in mechanical properties. The research results elucidate the influence of skeletal contact characteristics with different gradations on both mesoscopic features and macroscopic mechanical behavior, providing a crucial basis for optimizing asphalt mixture design. Full article

Forests play a crucial role in climate regulation through atmospheric CO₂ sequestration. However, disturbances like wildfires can severely compromise this function. This study assesses the ecological and economic consequences of a 2018 wildfire in The Roaches Nature Reserve, UK, focusing on post-fire carbon dynamics. A mixed woodland dominated by Pinus sylvestris L. and Larix decidua Mill. was evaluated via satellite imagery (remote sensing indices), dendrochronological analysis (wood cores sampling), and soil properties analyses. Remote sensing revealed areas of high fire severity and progressive vegetation decline. Tree-ring data indicated near-total mortality of L. decidua, while P. sylvestris showed greater post-fire resilience. Soil properties (e.g., soil organic carbon, biomass and microbial indices, etc.) assessed at a depth of 0–5 cm showed no significant changes. The analysis of CO₂ sequestration trends revealed a marked decline in burned areas, with post-fire sequestration reduced by approximately 70% in P. sylvestris and nearly 100% in L. decidua, in contrast to the stable patterns observed in the control stands during the same period. To estimate this important ecosystem service, we developed a novel CO₂ Sequestration Loss (CSL) index, which quantified the reduction in forest carbon uptake and underscored the impaired sequestration capacity of burned area. The decrease in CO₂ sequestration also resulted in a loss of regulating ecosystem service value, with burned areas showing a marked reduction compared to pre-fire conditions. Finally, a carbon loss of ~208 Mg ha⁻¹ was estimated in the burnt area compared to the control, mainly due to tree mortality rather than shallow soil carbon stock. Overall, our findings demonstrate that wildfire can substantially compromise the climate mitigation potential of temperate forests, highlighting the urgency of proactive management and restoration strategies. Full article

In recent years, there has been a global increase in environmental awareness, which has driven the application of natural materials or the synthesis of novel, environmentally compatible materials. Composite materials hold a prominent position among modern materials and are typically developed to achieve resistance to various damage mechanisms, thereby extending the service life of structures. This study presents the synthesis and characterisation of high-density metal–glass composite materials. The commercially available 316L stainless steel powder was used as the matrix material, while andesite basalt powder was used as the reinforcement phase. Andesite basalt aggregate, ground into powder, is a cost-effective, widely available, and environmentally friendly natural raw material. Powder metallurgy was employed to produce the composite materials. Sintering was performed at 1250 °C for 30 min in a vacuum. The density of the sintered composite samples was analysed as a function of andesite basalt content, with sintering conducted in the presence of a liquid phase. Composite materials were characterised using optical and scanning electron microscopy, X-ray structural analysis, and hardness testing. This study confirmed that the optimal combination of properties was achieved in the composite with 20 wt.% andesite basalt, present as a glass phase within the 316L steel matrix. Full article

Urban expansion alters environmental conditions, influencing tree physiology and performance. Urban trees provide cooling, sequester carbon, support biodiversity, filter contaminants, and enhance human health. This study examines how two common urban trees—Norway Maple (Acer platanoides L.) and Little-leaved Linden (Tilia cordata Mill.)—respond to urban site conditions by assessing leaf morphology, stomatal, and gas exchange traits across street and urban park sites in Chicago, IL. Street trees exhibited structural trait adjustments, including smaller leaf area, reduced specific leaf area, and increased stomatal density, potentially reflecting acclimation to more compact and impervious conditions. Norway Maple showed stable photosynthetic assimilation (A), stomatal conductance (g_s), and transpiration (E) across sites, alongside higher intrinsic water-use efficiency (_iWUE), indicating a conservative water-use strategy. In contrast, Little-leaved Linden maintained A and g_s but showed elevated E and _iWUE at street sites, suggesting adaptive shifts in water-use dynamics under street microenvironments. These findings highlight how species-specific physiological strategies and local site conditions interact to shape tree function in cities and underscore the importance of incorporating functional traits into urban forestry planning to improve ecosystem services and climate resilience. Full article

A key direction of the development of modern power systems is the application of a continuously increasing number of grid-forming power converters to provide various system services. One of the possible strategies for the implementation of grid-forming control is a control algorithm based on a virtual synchronous generator (VSG). However, at present, the problem of VSG operation under abnormal conditions associated with an increase in output current remains unsolved. Existing current saturation algorithms (CSAs) lead to the degradation of grid-forming properties during overcurrent limiting or reduce the possible range of current output. In this regard, this paper proposes to use the structure of modified current-controlled VSG (CC-VSG) instead of traditional voltage-controlled VSG. A current vector amplitude limiter is used to limit the output current in the CC-VSG structure. At the same time, the angle of the current reference vector continues to be regulated based on the emerging operating conditions due to the voltage feedback in the used VSG equations. The presented simulation results have shown that it was possible to achieve a wide operating range for the current phase from 0° to 180° in comparison with a traditional VSG algorithm. At the same time, the properties of the grid-forming inverter, such as power synchronization without phase-locked loop controller, voltage, and frequency control, are preserved. In addition, in order to avoid saturation of the voltage controller, it is proposed to use a simple algorithm of blocking and switching the reference signal from the setpoint to the current voltage level. Due to this structure, it was possible to prevent saturation of integrators in the control loops and to provide a guaranteed exit from the limiting mode. The results of adding this structure showed a five-second reduction in the overvoltage that occurs when it is absent. A comparison with conditional integration also showed that it prevented lock-up in the limiting mode. The results of experimental verification of the developed prototype of the inverter with CC-VSG control and CSA are also given, including a comparison with the serial model of the hybrid inverter. The results obtained showed that the developed algorithm excludes both the dead time and the load current loss when the external grid is disconnected. In addition, there is no tripping during overload, unlike a hybrid inverter. Full article