Search Results (5,342)

Chemical and biological approaches are widely applied to assess petroleum hydrocarbon contamination in soils; however, their results are often difficult to compare due to the use of fundamentally different extraction media. Chemical analytical methods typically rely on non-polar organic solvents, whereas biological toxicity assessments are based on aqueous soil extracts, reflecting water-soluble fractions of contaminants. This methodological discrepancy complicates the integrated evaluation of soil contamination and the assessment of remediation effectiveness. This study proposes an FTIR-based approach for assessing petroleum hydrocarbon contamination in sandy podzolic soil based on extraction with aqueous dimethyl sulfoxide (DMSO). The proposed method aims to reduce the methodological gap between classical chemical monitoring and aqueous-based biological assessment frameworks. The extraction performance of distilled water and aqueous DMSO solutions with different concentrations was evaluated using model soil samples artificially contaminated with crude oil. Crude oil was used as a multicomponent contaminant, whereas “petroleum hydrocarbons” refers to the operationally defined hydrocarbon fraction extracted from the soil–oil system and detected by FTIR in the C–H stretching region. Hydrocarbon extraction efficiency was assessed based on characteristic C–H stretching absorption bands in the 2800–3100 cm⁻¹ infrared region. Distilled water exhibited limited extraction capacity and rapidly reached saturation, resulting in weak and concentration-independent absorption responses. In contrast, aqueous DMSO increased the apparent solubility of hydrocarbons and yielded reproducible, concentration-dependent spectral responses. A 75% (v/v) aqueous DMSO solution was selected as a practical compromise extraction medium, increasing analytical sensitivity while remaining more compatible with aqueous conditions than conventional non-polar organic solvents. The proposed method provides a lower-hazard and methodologically coherent extraction approach for FTIR-based chemical monitoring of petroleum-contaminated soils and may facilitate improved comparability between chemical measurements and aqueous-based biological assessment approaches in integrated soil contamination and remediation studies. Full article

Microplastics (MP) are transported through rivers, acting as major conduits to oceans, yet standard transport models often fail to capture polymer-specific dynamics like settling and removal. This study proposes two novel analytical frameworks to address this: a modified Advection–Dispersion Equation (ADE) incorporating first-order sinking and removal, and a multi-phase model accounting for hydrodynamic–particle coupling. We derived exact closed-form solutions for a finite pulse input and validated the baseline model against established results. Our results demonstrate that the conventional ADE significantly overestimates peak MP concentrations, while the modified ADE reveals a “stretching” effect that extends the duration of ecosystem exposure. Our analysis indicates that sinking is the primary driver of mass loss to sediments, with higher sinking rates reducing aqueous concentrations by approximately 50% compared to non-settling scenarios. However, removal employs negligible influence during the initial pulse phase but shows cumulative impact over long transport distances. The study highlights the critical need to incorporate sediment accumulation terms into risk assessments, as ignoring sinking leads to underestimating benthic pollution and overestimating marine flux. Additionally, the multi-phase formulation provides a theoretical basis for modeling dense plastic spills where particles alter flow momentum. Full article

Elastomer-based nanocomposites combining polymer flexibility with conductive nanofillers provide lightweight, stretchable systems with tunable electromechanical properties for wearable electronics, soft robotics, and self-powered sensors. However, predicting their nonlinear response remains challenging because the observed piezoelectric-like response arises from strain-dependent interfacial polarization and evolving piezoresistive conduction pathways within heterogeneous microstructures. We introduce a continuum electro-hyperelastic framework combining the Mooney–Rivlin model for large-strain elasticity with a Helmholtz free-energy approach for electrostatic coupling. Analytical expressions for stress, electric displacement, and apparent piezoelectric coefficients are derived and implemented in finite element simulations. The model accurately reproduces the experimental mechanical, dielectric, and electromechanical behaviour of polydimethylsiloxane (PDMS) nanocomposites with 0.1–1 wt% graphene. These show increased stiffness, relative permittivity (from 3.4 to 4.0, ≈18%), and quasi-static d₃₃ coefficients (from −5.6 to −10.0 pC N⁻¹, ≈80% enhancement). Analytical and finite element method (FEM) results show consistent trends across the full deformation range, with Maxwell stress agreement within 10% at lower deformation levels, while deviations of 33–40% for coupled electromechanical quantities at an axial displacement u_z = ~−1 mm (~16.7% compressive strain) are attributable to three-dimensional shear effects absent from the uniaxial analytical assumption. Simulations reveal that graphene boosts Maxwell stress, yielding a four-fold increase at lower stretch ratios. This reframes PDMS–graphene composites as electro-hyperelastic materials, offering a predictive, extensible framework. It highlights apparent piezoelectricity as an emergent, tunable effect from charge redistribution in a compliant hyperelastic matrix—guiding the design of next-generation flexible devices leveraging field-induced coupling over intrinsic polarization. Full article

Chemical depilation presents a promising alternative to traditional shearing for Chinese Merino sheep, aiming to overcome issues of low efficiency and animal stress. Nonetheless, the safety of meat derived from sheep treated with this technology requires comprehensive scientific evaluation. Therefore, this study aimed to investigate the effects of CPA on wool quality, physiological and biochemical parameters, carcass traits, meat quality, fatty acids, and amino acids in sheep. Sheep were treated with different concentrations of CPA for 30 days, and slaughtering was performed at 3, 15, and 30 days post-administration. The CPA treatment (25–30 mg/kg) achieved complete defleecing and significantly increased staple and stretch lengths without affecting fiber length. At the 25 mg/kg dose, certain physiological and biochemical parameters, including mean corpuscular volume, mid-cell count, and lymphocyte percentage, recovered over time, with only short-term fluctuations observed. Moreover, treatment with 25 mg/kg CPA did not affect carcass characteristics, muscle amino acid composition, or meat quality parameters. In conclusion, this study verifies that complete wool shedding can be achieved with CPA at 25–30 mg/kg, while meat quality remains unaffected, providing a scientific basis for its adoption in dual-purpose sheep production. Full article

We have demonstrated a high-power, polarization-maintaining all-fiber amplifier operating at a repetition rate of 1 MHz. The seed laser is a Semiconductor Saturable Absorber Mirror (SESAM) mode-locked oscillator with an 18.1 nm full width in half-maximum (FWHM) spectrum. The pulse duration is stretched to 1.1 ns using temperature-controlled chirped fiber Bragg gratings (TCFBGs) and subsequently amplified in a 40 µm core Yb-doped fiber, achieving a maximum output power of 37 W. The amplified laser exhibits excellent beam quality with an M² factor of 1.04. The pulse duration is compressed to 207 fs in a single-grating compressor with 86% efficiency, yielding an average power of 32 W, a pulse energy of 32 µJ, and a peak power of 154.6 MW. This high-power all-fiber femtosecond laser is a promising source for scientific and industrial applications. Full article

This study systematically investigates a novel two-step approach to enhance the tribological performance of ultra-high molecular weight polyethylene (UHMWPE) by combining biaxial stretching with a subsequent hot pressing treatment. The significance of this work lies in developing a continuous, high-efficiency process that allows for decoupled control of bulk mechanical properties and surface tribological characteristics. The material’s evolution was comprehensively characterized using Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), tensile testing, and a Taber Abraser. Results show that biaxial stretching significantly enhanced the film’s bulk mechanical strength and thermal stability, creating a wider processing window for subsequent surface treatment. A subsequent hot pressing step was then applied to refine the surface characteristics, yielding an optimal wear rate of 0.002 g/1000 cycles and a kinetic coefficient of friction (µk) of 0.106. Achieving such a concurrent optimization of high wear resistance and low friction is crucial in materials processing. The study demonstrates that the synergistic effect of biaxial orientation and hot pressing-induced crystal perfection provides a powerful and previously unreported pathway to achieving a superior balance of low wear and low friction in UHMWPE. Full article

Raman spectroscopy is essential for the in situ identification of lunar minerals, yet weak signals and stringent payload constraints demand instruments with high throughput and mechanical robustness. Here a microscope-coupled spatial heterodyne Raman spectrometer (SHRS) is developed for stable, adjustment-free operation, with performance set by an explicit sampling analysis that links magnification, pixel pitch, and detector format to achievable spectral resolution and range. The interferometer geometry is fixed in service and is established using removable alignment blocks referenced to the Littrow condition during integration and then removed from the optical path, which mitigates backlash, creep, and dust sensitivity while preserving reinstallability for verification. Guided by the sampling analysis, the laboratory prototype meets a 100–3600 cm⁻¹ spectral range with an effective resolution better than 10 cm⁻¹, further corroborated by the narrow FWHM of the diamond Raman line. Representative minerals are recovered at the expected wavenumber, and a broad-scan of gypsum retrieves the sulfate fundamentals and the O–H stretching envelope near 3400 cm⁻¹, indicating maintained coverage and sensitivity into the high-wavenumber region relevant to bound water. A comparative study of sampling magnification confirms the sampling-limited predictions and shows that higher magnification improves effective SNR and peak visibility with only minor changes in width, providing practical guidance for compact SHRS design under low-signal conditions. The results support a compact, slit-free SHRS as a credible basis for future lunar and other planetary deployments. Full article

As a pivotal hub for the northward advancement of the Belt and Road Initiative and a strategic outpost for national security, the spatial patterns of towns in the border regions of northern Inner Mongolia exert a direct impact on the region’s sustainable development and long-term prosperity. This study focuses on 141 border towns situated along the Inner Mongolia stretch of China’s northern border. By leveraging analytical tools including kernel density analysis, standard deviation ellipse method, and nearest neighbor index analysis, it explores the distinctive characteristics of their spatial distribution. Furthermore, this study applies the Geodetector method to quantify the explanatory power of key influencing factors on the spatial differentiation of these border towns. The findings can be summarized as follows: (1) The border towns along the Inner Mongolia stretch of the northern border displayed a distinct heterogeneous distribution gradient characterized by prominent regional agglomeration and formed a three-tier spatial hierarchy. Specifically, the Bayannur–Hetao Plain Town Cluster served as the primary agglomeration core, supplemented by two secondary clusters, namely the Xing’an League–Southern Greater Khingan Range Town Cluster and the Hulunbuir–Border Port Town Cluster. In contrast, the Alxa League constituted a low-density peripheral belt with sparse town distribution. (2) Factor analysis via Geodetector revealed that the spatial distribution pattern of these border towns was primarily driven by the core mechanism of port-led urbanization. This core driver was synergistically reinforced by secondary factors such as mineral resource endowments, jointly shaping a complex spatial layout that partially transcended natural geographical constraints—a stark contrast to coastal ports, where development is dominated by innate natural geographic advantages. Full article

Residual stresses are inevitably introduced during plate manufacturing and pre-processing (e.g., quenching and pre-stretching). However, springback prediction in creep age forming (CAF) is still frequently carried out by assuming an initially stress-free blank, which may lead to biased deformation–stress histories and tool compensation errors, hindering high-accuracy forming. This study aimed to close this practical gap by quantifying how inherited residual stresses affected the CAF springback of AA2219 double-curvature thin-walled parts. In this study, a multi-step finite element (FE) process chain covering quenching, pre-stretching, and creep age forming (CAF) was developed to investigate the evolution of the initial residual stress field and its influence on CAF springback. Surface residual stresses after quenching and after pre-stretching were measured by X-ray diffraction (XRD) to validate the FE models. The results show that, after quenching, the through-thickness residual stress exhibits a characteristic ‘compressive at the surfaces and tensile in the core’ distribution, and pre-stretching markedly reduces the residual stress level. During CAF, although the initial residual stress difference is largely equilibrated during loading, it affects springback primarily through differences in accumulated creep deformation. Incorporating the initial residual stress field reduces the springback error bandwidth from 9.59 mm to 3.51 mm (a 63.4% reduction) under the original die configuration. Additional simulations under a modified die curvature (geometric deviation ≈ 6 mm) demonstrate that the springback reduction remains at the millimeter scale, indicating that the proposed FE framework maintains a consistent predictive improvement across different curvature conditions. This work provides a theoretical basis and practical guidance for high-precision creep age forming. Full article

Bacterial cellulose (BC) is highly valued for biomedical and industrial applications due to its exceptional biocompatibility, strength, and biodegradability. Polyvinyl alcohol (PVA) exhibits favorable characteristics, making it an ideal candidate for hydrogel formulation. In this study, BC–PVA composite hydrogels were synthesized by dissolving 1% w/w BC in ZnCl₂ 3H₂O and 10% w/w PVA in ZnCl₂nH₂O, n = 6, 9, 12, and 15. These solutions were combined at BC:PVA weight ratios of 3:1, 1:1, and 1:3, then crosslinking using a glutaraldehyde–acetone solution before immersion in deionized water. The resulting hydrogels exhibited a dense, tightly packed structure with mild to moderate porosity. FTIR analysis confirmed molecular interactions via a broad, reduced O–H stretching band and the appearance of C-H bending vibrations. The water content and swelling ratio ranged from 88.13% to 94.67% and 437.93% to 997.22%, respectively. At a compressive strain of 30%, the compressive strength ranged from 62.28 kPa to 93.16 kPa. This work introduces a novel and efficient method for preparing BC-PVA hydrogels using ZnCl₂ hydrate solvents. Both the ZnCl₂ hydration level and the BC:PVA ratio significantly influenced the structural, water content, swelling, and mechanical properties, offering tunable materials for biomedical or industrial applications. Full article

Nicotine exposure from e-cigarette use remains a growing public health concern, necessitating reliable biomarkers and analytical approaches for long-term exposure assessment. This study aimed to investigate the feasibility of detecting and classifying cotinine, the primary metabolite of nicotine, in fingernails of e-cigarette users using Fourier transform infrared (FTIR) spectroscopy coupled with chemometric analysis. Fingernail samples were collected and extracted from 30 e-cigarette users and 30 non-smokers. Infrared spectra were acquired in attenuated total reflectance mode and analysed using principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) for classification and prediction. Distinct spectral features associated with cotinine were observed in smoker samples, particularly an absorption band near 1277 cm⁻¹ corresponding to C–N stretching vibrations. Quantitative analysis revealed significantly higher cotinine concentrations in smokers compared with non-smokers (p < 0.05, Mann–Whitney U test). Chemometric modelling achieved complete discrimination between groups, with the PLS-DA model demonstrating excellent predictive performance and an area under the receiver operating characteristic (ROC) curve of 1.0. These findings indicate that FTIR spectroscopy combined with chemometric tools provides a rapid and effective approach for cotinine detection in fingernails, supporting its potential application in nicotine exposure assessment. Full article

A multitemporal floristic study was conducted on the aquatic and riparian plant communities of the lower stretch of the Tiber River (central Italy) to identify any floristic changes in response to possible environmental pressures that have occurred locally over time. This investigation was carried out by comparing α- and temporal β-diversity, as well as biological, chorological, and ecological traits of plant assemblages present in permanent plots (n = 24) and sampled at two different time points (2005, 2025). Although both aquatic and riparian plant communities showed an increase in α-diversity over time (+94.1% and +56.5%, respectively), they generally exhibited different temporal patterns. The aquatic community showed a more stable floristic structure compared to the riparian one, with a persistent dominance of eutrophic and pollution-tolerant species, although local disappearance/rarefaction of some species was recorded. On the contrary, the riparian community showed greater species turnover, mainly due to an increase in generalist, ruderal and alien species, which over time have partially replaced those typically associated with riparian habitats. Ecological trait-based analyses indicated an increase over time in the percentage of thermophilous, heliophilous and nitrophilous species in both plant communities; the riparian community also showed an increase in xerophilous ones. Overall, the results indicate that aquatic and riparian communities exhibit distinct temporal dynamics within the same river system and highlight how long-term, permanent plot-based floristic monitoring is a useful tool in environmental studies. Full article

The occurrence of forest pests and diseases is synergistically driven by stand factors (canopy closure, stand density, DBH, etc.) and site factors (elevation, soil type, slope aspect, etc.). To evaluate the effect grade of site factors on the degree of occurrence of specific forest pests and diseases after their interaction with stand factors, and to further determine the infestation severity of specific pests and diseases in stands established on suitable forestlands post-afforestation, a novel forest pest–disease base index model is defined based on the fundamental principles governing the occurrence of forest pests and diseases in specific pure forest stands. The model mandates the selection of pure forest ecosystems and the establishment of standard plots, within which a comprehensive survey of all site factors, stand factors, and target pest and disease incidence is conducted. Through methods such as stepwise regression analysis, key stand factors that influence forest pest and disease occurrence are identified, and a functional relationship between these factors and the forest pest–disease index is established. The optimal model, known as the principal curve, is obtained by relating the key stand factors to the pest–disease index. By proportionally stretching this principal curve, a series of forest pest–disease base index curves, namely the forest pest–disease base index model, is generated. These curves represent different pest–disease base index levels from bottom to top, corresponding to different grades of site effects on forest pest and disease occurrence. Furthermore, a model linking the pest–disease base index and site factors is established to evaluate the potential occurrence of pests and diseases in suitable forestlands. Applied to pure Pinus densiflora stands in Kunyu Mountain, this model quantitatively assesses the grade of site effects on the degree of occurrence of P. densiflora blight and Cephalcia kunyushanica, thereby verifying feasibility and practical applicability. It not only provides theoretical and technical support for pest and disease prediction prior to artificial forest establishment and the determination of infestation severity in post-afforestation stands but also improves ecological regulation methods for forest harmful organisms. Full article

The pantograph–catenary system is a critical component of the traction power supply network. Due to hard points on the overhead contact line and vibrations of the pantograph, pantograph–catenary separation may occur, leading to offline DC arc events. To investigate the characteristics of DC arcs generated during pantograph–catenary separation in metro systems, this study constructs a laboratory platform that simulates the offline process and analyzes the electrical characteristics, optical intensity, and arc-burn duration under different electrode separation conditions. First, a DC pantograph–catenary offline arc simulation platform is developed using a contact wire, a carbon-strip pantograph slider, and a linear motor, enabling slider movement in both horizontal and vertical directions. Second, offline discharge experiments are conducted to compare the discharge process and electrical arc characteristics with and without horizontal slider motion. Finally, arc luminosity and burn duration are measured under various electrode separation configurations, and the influence of voltage level, current level, and electrode material is examined. Experimental results reveal a significant polarity effect, where the arc burn duration is notably longer when the contact wire serves as the cathode than when the carbon slider serves as the cathode. At the instant of separation, the high electric field intensity within the micro-gap triggers pronounced “peak phenomena” in both arc resistance and power, accompanied by abrupt voltage surges and transient current dips. Furthermore, the introduction of horizontal motion modulates the arcing process, causing the stable arcing voltage to follow a distinctive trend of a slow increase followed by a gradual decrease, which differs from static separation characteristics. Finally, this study demonstrates that voltage levels exert a more dominant influence on arc luminosity and duration than current levels, while the maintenance voltage of the arc channel remains significantly lower than the air breakdown voltage. Full article

Let $(M_1,F_1)$ and $(M_2,F_2)$ be two Finsler manifolds. A Minkowskian product Finsler manifold is defined to be the product manifold $M_1\times M_2$, which is endowed with a Finsler metric F. This metric F is constructed by taking the square root of a product function f, which itself operates on the squares of the original metrics $F_1$ and $F_2$. This paper focuses on new classes of stretch Minkowskian product Finsler manifolds. We prove that the Minkowskian product Finsler manifold $(M,F)$ is a $\tilde{\mathbf{B}}$-manifold (resp. $\tilde{\mathbf{B}}$-stretch manifold, $\mathbf{H}$-stretch manifold) if and only if $(M_1,F_1)$ and $(M_2,F_2)$ are both $\tilde{\mathbf{B}}$-manifold (resp. $\tilde{\mathbf{B}}$-stretch manifold, $\mathbf{H}$-stretch manifold). Thus an effective method for constructing special Finsler manifolds mentioned above is given. Full article