Search Results (1,078)

Microplastics (MPs) and nanoplastics (NPs) have emerged as pervasive pollutants across different aquatic systems on a global basis, yet integrated assessments linking wastewater, riverine, and marine environments remain scarce. The present study provides the first comprehensive evaluation of MPs in three interconnected aquatic matrices of Northern Greece, namely surface seawater from the Thermaic Gulf, surface freshwater from the Axios River, and influent and effluent wastewaters from the Thessaloniki WWTP (Sindos). During two sampling periods spanning late 2023 and spring 2024, suspected MPs were isolated, morphologically classified by stereomicroscopy, and chemically characterized through pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). MPs were ubiquitously detected in all substrates, exhibiting distinct spatial and compositional patterns. Seawater samples displayed moderate concentrations (1.5–4.8 items m⁻³) dominated by fibers and fragments, while riverine samples contained slightly higher levels (0.5–2.5 items m⁻³), enriched in fibrous forms and polyolefins (PE, PP). Wastewater influents showed the highest MP abundance (78–200 items L⁻¹; 155.6–392.3 µg L⁻¹), decreasing significantly in effluents (11–44 items L⁻¹; 27.8–74.3 µg L⁻¹), corresponding to a removal efficiency of 81–87.5%, being the first indicative removal efficiencies in a Greek WWTP. Among the different polymers detected, polyethylene, polypropylene, and poly(ethylene terephthalate) were identified as the most prevalent polymers across all matrices. Interestingly, a shift toward smaller size classes (125–500 µm) in effluents indicated in-plant fragmentation processes, while increased concentrations during December coincided with increased rainfall, highlighting the influence of hydrological conditions on MP fluxes. The combined morphological and polymer-specific approach provides a holistic zunderstanding of MP transport from inland to marine systems, establishing essential baseline data for Mediterranean environments and reinforcing the need for integrated monitoring and mitigation strategies. Full article

Sward structure and post-grazing heights (SH) significantly influence plant growth and animal intake, crucial for dairy grazing systems. However, these interactions are dynamic and vary with season, resource heterogeneity, and defoliation patterns. Seasonal effects of control (TC), medium (TM), and lax (TL) post-grazing SH of grazed Lolium arundinaceum-based pasture on forage production and utilization, herbage mass, green cover, and chemical composition were tested during autumn-winter and spring seasons and among tall (TP), medium (MP), and short (SP) patches in spring. Thirty-six lactating Holstein cows were randomized evenly to TC, TM, and TL grazing treatments to achieve 6, 9, and 12 cm of post-grazing SH during autumn-winter, and 9, 12, and 15 cm in spring. Forage production was higher on TL than TM and TC, yet utilization was similar across all treatments. The TP relative to MP on SP increased for TL compared to TC and TM. The TP-TC presented higher leaf-density and leaf-proportion, than TP-TL, without modifying leaf canopy distribution of superior-medium horizons among treatments. Grazing management modulated forage production and structural heterogeneity across SH treatments. Critically, monitoring patch-level dynamics—rather than mean height —is essential for optimizing production and harvest efficiency in temperate systems by improving grazing horizon accessibility. Full article

The Strait of Messina (Central Mediterranean Sea) has always been known for the stranding of marine organisms, especially during the spring. We came across an extraordinary event of mass stranding in April 2025, with 453 specimens of Macroramphosus sp. found through a single night. A total of 571 post-larvae and juvenile individuals stranded between February and May 2025 were examined for this study. Clear morphological differences related to the size, especially in post-larvae, were highlighted. The relationship between Body Length (BL) and other morphometric measurements, such as Dorsal Spine Length (DSL), Snout Length (SNL), and Body Height (BH), were studied, with the aim of identifying without any doubt the species Macroramphosus gracilis. A slightly negative allometric relationship between length and weight shows that it grows faster in length and slower in weight. This study aims to improve the state of knowledge on slender snipefish M. gracilis, and particularly on the somatic features of different post-larval development stages, such as the presence of spinules in various parts of the body. All these morphological changes could give us a hint at the ecological adaptation to the habit shift, as relates to development. Full article

The development of innovative technologies aimed at increasing agricultural crop yields through the use of growth regulators that incorporate various biologically active chemical moieties is a key focus in modern global agroscience. In this context, novel water-soluble silicon-organic compounds derived from carbamate (I) and oxamate (II) have been synthesised by the introduction of an organo-silicone fragment into these biologically active molecules. The compounds are O-isopropyl-N-(2-trimethylsilyloxyethyl)carbamate (III) and O-isopropyl-N-(2-trimethylsilyloxyethyl)oxamate (IV). It has been found that the 1 × 10⁻⁵ M water solutions of the compounds I–IV exhibited growth-regulating activity on the seeds of spring common wheat (Triticum aestivum L.). Laboratory studies demonstrated that the new silicon-containing compounds III and IV had a positive influence on the following: the germination potential, the seed germination, the length of roots, and the growth and development of shoots. Field tests revealed that spring wheat treatment with the compounds III and IV yielded an augmentation in spike length, an elevated quantity of grains per spike, and a grain mass per spike in comparison to the control. The application of compounds I–IV resulted in a significant enhancement in spring wheat yield. Full article

A spring–dashpot model, consisting of a spring branch and two Maxwell (named long- and short-term) branches, was used to simulate stress drop during the relaxation stages of multi-relaxation (MR) tests. This work shows that the stress drop at relaxation in a deformation range around the peak stress could be closely simulated without changing the parameter values for the short-term branch. This possibility was confirmed using three ethylene/1-hexene copolymers and one ethylene homo-polymer, among which the main differences are mass density and short-chain branch (SCB) content. The work examined the influence of SCB content and mass density on the stiffness of the two Maxwell branches, and the results showed that, unlike the long-term branch counterpart, stiffness of the short-term branch is not a monotonic function of the SCB content or the mass density. This led to a discussion on the possible relationship between the stiffness of the two Maxwell branches and the deformation resistance of the amorphous phase at different locations of the microstructure, i.e., in the interlamellar region and as part of the network structure. The paper concludes that a combination of the MR test and the spring–dashpot model could provide information that is related to the stiffness in different parts of PE’s amorphous phase, though further work is needed to verify this conclusion. Full article

Background: There is a limited amount of evidence concerning the association between seasonal variation and the level of physical activity in individuals with chronic disease. This longitudinal observational study aimed to explore seasonal, monthly, and holiday variations in self-monitored step counts over two years among adults with prediabetes and type 2 diabetes in Sweden. Methods: Participants were recruited at primary care centers from 2013 to 2018 to take part in a physical activity intervention. Inclusion criteria included the following: an age of 40–80 years, having prediabetes or type 2 diabetes (≥1 year), and the ability to communicate in Swedish. Individuals with recent myocardial infarction, impaired renal function, diabetic ulcers, a limited capacity for physical activity, insulin onset (<6 months), recurrent or severe hypoglycemia, a high baseline for physical activity, or no internet access were excluded. In total, 120 participants wore step counters and recorded daily steps for two years. Linear mixed models adjusted for sex, age, and body mass index were applied. Results: Mean (95% CI) step counts were statistically significantly higher in summer (7825 [7762, 7889]) and spring (7805 [7757, 7853]) compared to winter (7098 [7052, 7145]) and fall (7422 [7349, 7490]). Highest step counts were registered in May (7993 [7904, 8071]), followed by June (7968 [7895, 8063]), and the lowest in January (6944 [6856, 7034]) and November (7208 [7113, 7289]). Step counts during holiday periods were statistically significantly lower than non-holiday periods across all seasons. Conclusion: Self-monitored daily steps varied over the seasons in this sample of individuals with prediabetes and type 2 diabetes. Declined physical activity levels in months with unfavorable weather conditions require attention in consultations and research. Full article

Filled joints significantly influence the dynamic response of rock masses, exhibiting coupled nonlinear compression-hardening and viscous deformation. However, the combined effects of these mechanisms on wave propagation remain unclear. This study develops a theoretical model based on a nonlinear viscoelastic formulation, in which a compression-hardening spring (governed by the Bandis–Barton model, with its initial compressive stiffness and maximum allowable closure) is connected in series with a viscous dashpot. Using the displacement discontinuity method and the method of characteristics, we analyze the transmission of compressive stress waves across a filled joint. The results show that the transmission coefficient increases with incident wave amplitude but decreases with frequency, whereas reflection exhibits the opposite trends. The initial compressive stiffness has a minimal impact on transmission but induces a nonlinear decrease in reflection. Increasing the maximum allowable closure slightly reduces transmission but sharply increases reflection, whereas higher viscous stiffness enhances transmission and slightly suppresses reflection. Energy attenuation grows rapidly with amplitude before stabilizing. The initial compressive stiffness is most influential at low amplitudes, the maximum allowable closure is most significant at moderate amplitudes, and viscous effects remain consistent across all amplitudes. Increases in frequency lead to a nonlinear decrease in attenuation, with the initial compressive stiffness and maximum allowable closure dominating at high frequencies, and viscous effects prevailing at low frequencies. This work systematically reveals the coupled roles of nonlinear compression-hardening and viscosity in wave propagation across filled joints, providing theoretical support for dynamic hazard mitigation and geophysical exploration. Full article

Using MODIS-Aqua satellite observations, this study analyzes the spatiotemporal distribution characteristics of particulate organic carbon (POC) in China’s marginal seas from 2003 to 2024. The statistical relationships between various marine environmental variables, including sea surface temperature (SST), nutrients, and primary production (PP), and POC concentrations are explored using partial least squares path modeling (PLS-PM). Finally, a box model approach is conducted to assess the POC budget in the study area. The results indicate that the POC concentration in the marginal seas of China generally exhibits a characteristic of being high in spring and low in summer. The highest concentration of POC is observed in the Bohai Sea, followed by the Yellow Sea, and the lowest in the East China Sea, with coastal waters exhibiting higher POC concentrations compared to the central areas. The spatial distribution and seasonal changes in POC are jointly influenced by PP, water mass exchange, resuspended sediments, and terrestrial inputs. Large-scale climate modes show statistical associations with POC concentration in the open waters of China’s marginal seas. PP and respiratory consumption are identified as the predominant input and output fluxes, respectively, in China’s marginal seas. This study enriches the understanding of carbon cycling processes and carbon sink mechanisms in marginal seas. Full article

Water-soluble inorganic ions (WSIIs) are major components of PM_2.5 and play a prominent role in atmospheric acidification. Previous studies have mainly focused on urban areas, whereas research pertaining to county-level cities remains comparatively limited. To fill this gap, PM_2.5 samples were collected from March 2018 to February 2019 in Botou, a county-level city in the Jing–Jin–Ji region. Seasonal variation of WSII were studied, and their sources was apportioned by Positive Matrix Factorization (PMF) model. Annual PM_2.5 concentrations were 79.15 ± 48.44 mg/m³, which is 2.26 times of the Level II standard limit specified the National Ambient Air Quality Standard. Nitrate (NO₃⁻) was the most abundant ion, followed by ammonium (NH₄⁺) and sulfate (SO₄²⁻). The secondary inorganic aerosols (SIA, i.e., SO₄²⁻, NO₃⁻, and NH₄⁺) constituted 35.1± 4.7% of PM_2.5 mass. PM_2.5 mass, SO₄²⁻, NO₃⁻, NH₄⁺, K⁺, and Cl⁻ showed highest concentrations in winter. Ammonium salts were existed as ammonium sulfate ((NH₄)₂SO₄) and ammonium nitrate (NH₄NO₃) in spring, summer, and autumn, while it also can be existed as ammonium chloride (NH₄Cl) in winter. PMF analysis shows that the sources of WSIIs dominated by secondary source and followed by biomass burning. These results highlight the need for improved controls on gaseous precursors (NH₃, NO₂ and SO₂) and biomass burning to effectively reduce PM_2.5. Full article

Transmission tower guy wires are critical flexible tension members ensuring the stability and safe operation of overhead power transmission networks. However, these components are vulnerable to external impacts from falling rocks, ice masses, and other natural hazards, which can cause excessive deformation, anchorage loosening, and catastrophic failure. Current design standards primarily consider static loads, lacking comprehensive models for predicting dynamic impact responses. This study presents a theoretical model for predicting the peak impact response of guy wires by modeling the impact process as a point mass impacting a nonlinear spring system. Using an energy-based elastic potential method combined with cable theory, analytical solutions for axial force, displacement, and peak impact force are derived. Newton–Cotes numerical integration solves the implicit function to obtain closed-form solutions for efficient prediction. Validated through finite element simulations, deviations of peak displacement, peak impact force, and peak axial force between theoretical and numerical results are within ±4%, ±18%, and ±4%, respectively. Using the validated model, parametric studies show that increasing the inclination angle from 15° to 55° slightly reduces peak displacement by 2–4%, impact force by 1–13%, and axial force by 1–10%. Higher prestress (100–300 MPa) decreases displacement and impact force but increases axial force. Longer lengths (15–55 m) cause linear displacement growth and nonlinear force reduction. Impacts near anchorage points help control displacement risks, and impact velocity generally has a more significant influence on response characteristics than impactor mass. This model provides a scientific basis for impact-resistant design of power grid infrastructure and guidance for optimizing de-icing strategies, enhancing transmission system safety and reliability. Full article

Guided by principles of symmetry to achieve a proper balance among model consistency, accuracy, and complexity, this paper proposes a new approach for identifying the unknown parameters of nonlinear one-degree-of-freedom mechanical systems using nonlinear regression methods. To this end, the steps followed in this study can be summarized as follows. Firstly, given a proper set of input time histories and a virtual model with all parameters known, the dynamic response of the mechanical system of interest, used as output data, is evaluated using a numerical integration scheme, such as the classical explicit fixed-step fourth-order Runge–Kutta method. Secondly, the numerical values of the unknown parameters are estimated using the Levenberg–Marquardt nonlinear regression algorithm based on these inputs and outputs. To demonstrate the effectiveness of the proposed approach through numerical experiments, two benchmark problems are considered, namely a mass-spring-damper system and a simple pendulum-damper system. In both mechanical systems, viscous damping is included at the kinematic joints, whereas dry friction between the bodies and the ground is accounted for and modeled using the Coulomb friction force model. While the source of nonlinearity is the frictional interaction alone in the first benchmark problem, the finite rotation of the pendulum introduces geometric nonlinearity, in addition to the frictional interaction, in the second benchmark problem. To ensure symmetry in explaining model behavior and the interpretability of numerical results, the analysis presented in this paper utilizes five different input functions to validate the proposed method, representing the initial phase of ongoing research aimed at applying this identification procedure to more complex mechanical systems, such as multibody and robotic systems. The numerical results from this research demonstrate that the proposed approach effectively identifies the unknown parameters in both benchmark problems, even in the presence of nonlinear, time-varying external input actions. Full article

Southwestern China serves as a critical region for carbon sources and sinks, influenced by both natural ecosystems and anthropogenic activities. The Shangri-La atmospheric background station (28.01° N, 99.73° E), the only regional station in southwestern China, provides essential data for understanding CO₂ dynamics. This study analyzes hourly CO₂ mole fractions from 2019 to 2022. Background signals were extracted using the Robust Extraction of Baseline Signal (REBS) algorithm, and air-mass trajectories were analyzed using HYSPLIT model and Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) methods. The REBS-derived background CO₂ concentration increased from ~409 ppm in 2019 to ~417 ppm in 2022, yielding a growth rate of 1.9 ± 0.1 ppm yr⁻¹, slightly lower than the 2010–2014 rate reported previously and consistent with the recent global slowdown associated with ENSO-driven carbon–climate variability. A coherent seasonal cycle, with spring maxima and late-summer minima, reflects the combined influence of biospheric uptake and monsoonal inflow. Comparison with the global marine boundary layer and Waliguan records shows similar phase and amplitude, confirming the representativeness of Shangri-La as a regional background site, albeit with a one-month phase lag to Waliguan station due to regional climatic and phenological differences. Trajectory and wind analyses identify southern Indo-Myanmar and Sichuan–Yunnan regions as major transport corridors influencing high-CO₂ events. Overall, the results highlight that regional transport rather than local emissions dominates CO₂ variability at Shangri-La. The derived background and transport signals thus provide an updated and internally consistent characterization of carbon-cycle variability over the southeastern Tibetan Plateau, offering critical observational support for future regional carbon budget assessments. Full article

High-resolution in situ field measurements capturing seasonal 3D mixing dynamics at river confluences are scarce, yet this understanding is essential for effective water-quality management and pollutant-transport prediction in river–lake systems. To address this gap, this study investigates the confluence of the North and South Han Rivers in the Paldang Reservoir. We introduce and apply a novel mixing proximity index (MPI) to quantify the degree of mixing and water-mass origin based on 3D electrical conductivity and temperature data. Seasonal field campaigns, conducted with an acoustic Doppler current profiler and multi-parameter sensors, revealed distinct hydrodynamic behaviors: strong summer stratification suppressed vertical mixing; winter momentum asymmetry induced persistent flow separation despite minimal temperature differences; and spring conditions fostered rapid mixing, barring some residual unmixed deep layers. The MPI effectively delineated shear layers and identified unmixed water zones, providing an enhanced understanding of mixing dynamics beyond the capabilities of traditional tracer- or statistics-based metrics. These findings highlight the combined influence of density differences, tributary momentum, and dam operations on confluence mixing, offering practical insights for water-resource management and improving 3D hydrodynamic model validation. Full article

Aflatoxin M1 (AFM1), a hydroxylated metabolite of aflatoxin B1, is a persistent food safety hazard in the dairy production chain. This study investigated AFM1 occurrence in fermented dairy products collected from the Croatian market in spring 2025 and assessed associated dietary exposure risks. A total of 81 samples were analyzed using ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) following immunoaffinity column clean-up. AFM1 was detected in 48.1% of samples, with a mean concentration of 0.015 µg/kg. Products with thermophilic and probiotic bacterial cultures showed the lowest incidence rates, at 33.3% and 40.0%, respectively. Significantly higher AFM1 occurrence was found in Croatian samples than in imported ones (p < 0.05). Exposure assessment, based on estimated daily intake (EDI), hazard index (HI), and margin of exposure (MOE), identified toddlers and children as the most at-risk groups, with EDI ranging from 0.21 to 0.93 ng/kg bw/day, depending on AFM1 concentration. HI exceeded 1 even at mean AFM1 levels, while MOE fell below the safety threshold of 10,000 in worst-case scenarios, indicating potential health concerns. These findings underscore the need for continuous monitoring and targeted risk mitigation strategies for vulnerable populations, and support expanding regulatory limits to include processed dairy products. Full article

The central Bohai Sea (CBS) is the distribution center and wintering grounds for economically important species of fish, shrimp, and crabs migrating from the Yellow Sea and the BS. However, the frequency of hypoxia in the CBS has gradually increased, posing a threat to its ecology. Therefore, we analyzed data from an on-site investigation of the cold-water mass coverage area in the southern part of the BS in the spring, summer, and autumn of 2022. We investigated the characteristics of seasonal variation in water quality parameter, the main characteristics and leading factors affecting the distribution of bottom hypoxia using stratification data and the Nutritional Status Quality Index. The “boot-shaped” distribution of hypoxia in summer was primarily the result of the intrusion of cold and highly saline water from the northern part in the study area, as well as the intrusion of high-temperature and low-salinity water from the Yellow River estuary (YRE) and the high-salinity water in the northeast corner of the study area, which had altered the stratification effect of the region. This is also the main reason that affects the accuracy of the prediction for occurrence of hypoxia stations in summer. The results show that the cold-water mass in the northern part of the Bohai Sea invades the cold-water mass in the southern part in summer 2022. Thus, this study provides novel insights into the formation and distribution of hypoxia in the CBS. Full article