Search Results (20,669)

Monocrystalline silicon is an excellent semiconductor material for integrated circuits. Its surface quality has an enormous effect on its service life. The surfaces are formed by ultra-precision machining using nano-grinding, one of the technologies that can achieve surface roughness at the nano- or sub-nano-scale. Therefore, subsurface damage of monocrystalline silicon in nano-grinding was studied by establishing a molecular dynamics simulation model, and the impact of machining parameters on the force–thermal behavior was analyzed. The results reveal that the mechanism of subsurface damage is mainly structural phase transformation and amorphization. In nano-grinding of monocrystalline silicon, the tangential grinding force has a relatively major role in material removal. With increasing grinding depth and grinding speed, the grinding heat rises, and a certain degree of high temperature strengthens the toughness of the material, improving the subsurface quality of monocrystalline silicon. Therefore, subsurface damage in monocrystalline silicon can be controlled by reducing the grinding depth and increasing the grinding speed. Full article

Understanding the multi-crack coupling fracture behavior in brittle materials is particularly critical for aging dam infrastructure, where 78% of structural failures originate from crack network coalescence. In this study, we introduce the concepts of crack distance ratio (DR) and size ratio (SR) to describe the relationship between crack position and length and employ the discrete element method (DEM) for extensive numerical simulations. Specifically, a crack density function is introduced to assess microscale damage evolution, and the study systematically examines the macroscopic mechanical properties, failure modes, and microscale damage evolution of rock-like materials under varying DR and SR conditions. The results show that increasing the crack distance ratio and crack angle can inhibit the crack formation at the same tip of the prefabricated crack. The increase in the size ratio will promote the formation of prefabricated cracks on the same side. The increase in the distance ratio and size ratio significantly accelerate the rapid increase in crack density in the second stage. The crack angle provides the opposite effect. In the middle stage of loading, the growth rate of crack density decreases with the increase in crack angle. Overall, the size ratio has a greater influence on the evolution of microscopic damage. This research provides new insights into understanding and predicting the behavior of materials under complex stress conditions, thus contributing to the optimization of structural design and the improvement of engineering safety. Full article

This study fabricated fluorinated graphite (FG)-reinforced Ni/WC/CeO₂ cladding layers on 45 steel substrates using vacuum cladding technology. Their microstructure, phase composition, mechanical properties, and tribological behavior over a wide temperature range (25–800 °C) were systematically characterized. The results demonstrate that FG addition promotes the formation of a self-lubricating CeF₃ phase. The optimal CeF₃ phase formation efficiency occurred at a 1.5 wt% FG content (NWF15). The NWF15 cladding layer exhibited the smallest average grain size (15.88 nm) and the lowest porosity (0.1410%) among all samples. Mechanical testing revealed that this cladding layer possessed the highest microhardness (1062.7 ± 21.9 HV_0.2). Its H/E and H³/E² ratios, indicative of resistance to elastic strain and plastic deformation, reached 0.0489 and 0.0291, respectively. Tribological tests revealed pronounced temperature-dependent wear behavior: abrasive wear was predominant at 25 °C; adhesive wear dominated from 200 to 600 °C; and oxidative wear became the primary mechanism at 800 °C. Throughout this temperature range, the CeF₃ phase effectively reduced wear damage by suppressing groove propagation and providing effective lubrication, particularly under high-temperature conditions. Full article

Drought stress caused by continuous global warming poses a severe challenge to the growth and development of Nitraria tangutorum. Abscisic acid has an important regulatory function in the process of plants responding to drought stress. This study took the N. tangutorum seedlings of Zhangye provenance 2-17-16 genealogy as the research object to explore the physiological mechanism of how different concentrations of exogenous ABA alleviate drought damage in N. tangutorum. The results showed that exogenous ABA could promote the growth and increase the leaf relative water content of N. tangutorum seedlings under drought stress. It alleviates the photosynthetic inhibition phenomenon of N. tangutorum seedlings under drought stress by regulating the photoprotective mechanism and energy distribution efficiency of photosystem II. It also alleviates the drought damage of N. tangutorum by increasing the content of osmotic-adjustment substance contents such as soluble sugar, soluble protein, proline, and starch, as well as enhancing the activity of antioxidant enzymes such as POD, SOD, and CAT. The comprehensive analysis showed that 20 μM and 30 μM ABA have the best alleviating effects on the drought damage of N. tangutorum seedlings. This study provides a theoretical basis for the restoration, propagation, and protection of N. tangutorum, and it is of great significance for maintaining the balance and stability of desert ecosystems. Full article

This study aims to investigate the mechanical behavior of cement mortar and concrete through a hybrid approach that integrates artificial intelligence (AI) techniques with finite element modeling (FEM). Support Vector Machine (SVM) models with Radial Basis Function (RBF) and polynomial kernels, along with Multilayer Perceptron (MLP) neural networks, were employed to predict the compressive strength (Fc) and flexural strength (Fs) of cement mortar incorporating nano-silica (NS) and micro-silica (MS). The dataset comprises 89 samples characterized by six input parameters: water-to-cement ratio (W/C), sand-to-cement ratio (S/C), nano-silica-to-cement ratio (NS/C), micro-silica-to-cement ratio (MS/C), and curing age. Simultaneously, the axial compressive behavior of C20-grade concrete was numerically simulated using the Concrete Damage Plasticity (CDP) model in ABAQUS, with stress–strain responses benchmarked against the analytical models proposed by Mander, Hognestad, and Kent–Park. Due to the inherent limitations of the finite element software, it was not possible to define material models incorporating NS and MS; therefore, the simulations were conducted using the mechanical properties of conventional concrete. The SVM-RBF model demonstrated the highest predictive accuracy with RMSE values of 0.163 (R² = 0.993) for Fs and 0.422 (R² = 0.999) for Fc, while the Mander model showed the best agreement with experimental results among the FEM approaches. The study demonstrates that both the SVM-RBF and CDP-based modeling approaches serve as robust and complementary tools for accurately predicting the mechanical performance of cementitious composites. Furthermore, this research addresses the limitations of conventional FEM in capturing the effects of NS and MS, as well as the existing gap in integrated AI-FEM frameworks for blended cement mortars. Full article

The impact of invasive alien species (IAS) is one of the direct factors causing global biodiversity decline and economic losses, and predicting the potential invasion risks of invasive species is crucial for developing prevention and control strategies. In recent years, an increasing number of studies have shown that invasive species undergo rapid shifts in climate niche in invaded areas. Accurately quantifying the dynamic shifts in the climate niche of invasive species in invaded areas is crucial for developing a more accurate framework for early warning of invasive species risks. Pomacea canaliculata is a freshwater snail found in South America and has become one of the most aggressive aquatic species in the world. Since its introduction to China in 1981, it has rapidly spread and caused multiple serious damages to agriculture, ecology, and public health. Therefore, based on multi-source distribution data of P. canaliculata, this study calculated the climate niche overlap by Schoener’ s D, quantified the niche shifts between the P. canaliculata in native and invaded areas (China) via the COUE scheme (a unified terminology representing niche centroid shift, overlap, unfilling, and expansion), and analyzed their changes on a time scale. The results revealed that there have been significant climate niche shifts (Schoener’s D < 0.2, niche similarity tests p > 0.01, niche equivalence tests p < 0.01) between the native and invaded areas (China) of P. canaliculata, which does not support the climate niche conservation hypothesis. The minimum temperature of the coldest month (Bio 6) and precipitation seasonality (Bio 15) were the key climate variables driving the climatic niche shift, and P. canaliculata can survive in colder and more arid regions than their native counterparts. The changes in the niche shifts in P. canaliculata on a time scale show significant temporal heterogeneity, and its invasion behavior in China presents a discontinuous and phased expansion pattern, with strong adaptability to new environments. The results are of great significance for the future development of more accurate ecological niche model (ENM), the formulation of more targeted prevention and control strategies, and the study of adaptive evolution mechanisms of invasive species. Full article

Excessive stress disrupts cardiac homeostasis via complex and multifactorial mechanisms, resulting in cardiac dysfunction, cardiovascular disease, or even sudden cardiac death, yet the underlying molecular mechanisms remain poorly understood. Accordingly, we aimed to elucidate how stress induces calcium dysregulation and contributes to cardiac dysfunction and injury through the nuclear receptor subfamily 3 group c member 1 (NR3C1)/Glomulin (GLMN)/FK506-binding protein 12.6 (FKBP12.6) signaling pathway. Using mouse models of acute and chronic restraint stress, we observed that stress-exposed mice exhibited reduced left ventricular ejection fraction, ventricular wall thickening, elevated serum and myocardial cTnI levels, along with pathological features of myocardial ischemia and hypoxia, through morphological, functional, and hormonal assessments. Using transmission electron microscopy and Western blotting, we found that stress disrupted mitochondrial quality control in cardiomyocytes, evidenced by progressive mitochondrial swelling, cristae rupture, decreased expression of fusion proteins (MFN1/OPA1) and biogenesis regulator PGC-1α, along with aberrant accumulation of fission protein (FIS1) and autophagy marker LC3. At the cellular level, ChIP-qPCR and siRNA knockdown confirmed that stress activates the glucocorticoid receptor NR3C1 to repress its downstream target GLMN, thereby preventing FKBP12.6 ubiquitination and degradation, resulting in calcium leakage and overload, which ultimately impairs mitochondrial quality control and damages cardiomyocytes. In conclusion, our findings reveal that stress induces myocardial damage through NR3C1/GLMN-mediated FKBP12.6 ubiquitination, disrupting calcium homeostasis and mitochondrial quality control, and lay a theoretical foundation for dissecting the intricate molecular network of stress-induced cardiomyopathy. Full article

Equine semen preservation is fundamental to modern equine reproduction, supporting breeding programs, genetic conservation, and industry sustainability. However, significant challenges persist, including temperature sensitivity, oxidative stress, bacterial contamination, individual variability, and lack of standardized preservation protocols. These factors contribute to reduced sperm viability and fertility following cryopreservation. This review examines critical obstacles in equine semen preservation, focusing on cryopreservation sensitivity, molecular damage mechanisms, economic constraints, and seasonal quality variations. We analyze the molecular and structural alterations (e.g., oxidative stress, membrane damage, and DNA fragmentation) and their impact on cryopreservation success. The review evaluates evidence-based enhancement strategies, including nutritional supplementation and genetic approaches, for improving semen quality. Nutritional interventions that utilize antioxidants, polyunsaturated fatty acids (PUFAs), and nutraceuticals have demonstrated promising results in enhancing sperm motility, preserving membrane integrity, and improving overall semen quality. Additionally, we discuss key candidate genes associated with equine semen-quality traits, including sperm motility, viability, and cryotolerance. The integration of nutritional supplementation and genetic selection strategies presents viable pathways for optimizing equine semen preservation techniques. These combined approaches offer potential solutions for overcoming current limitations, ultimately supporting sustainable breeding programs and advancing genetic conservation efforts in the equine industry. Full article

To ensure the safe and reliable operation of hydrogen-blended natural gas (HBNG) pipelines in urban utility tunnels, this study conducted a comprehensive CFD simulation of the leakage and diffusion characteristics of HBNG in confined underground environments. Utilizing ANSYS CFD software (2024R1), a three-dimensional physical model of a utility tunnel was developed to investigate the influence of key parameters, such as leak sizes (4 mm, 6 mm, and 8 mm)—selected based on common small-orifice defects in utility tunnel pipelines (e.g., corrosion-induced pinholes and minor mechanical damage) and hydrogen blending ratios (HBR) ranging from 0% to 20%—a range aligned with current global HBNG demonstration projects (e.g., China’s “Medium-Term and Long-Term Plan for Hydrogen Energy Industry Development”) and ISO standards prioritizing 20% as a technically feasible upper limit for existing infrastructure, on HBNG diffusion behavior. The study also evaluated the adequacy of current accident ventilation standards. The findings show that as leak orifice size increases, the diffusion range of HBNG expands significantly, with a 31.5% increase in diffusion distance and an 18.5% reduction in alarm time as the orifice diameter grows from 4 mm to 8 mm. Furthermore, hydrogen blending accelerates gas diffusion, with each 5% increase in HBR shortening the alarm time by approximately 1.6 s and increasing equilibrium concentrations by 0.4% vol. The current ventilation standard (12 h⁻¹) was found to be insufficient to suppress concentrations below the 1% safety threshold when the HBR exceeds 5% or the orifice diameter exceeds 4 mm—thresholds derived from simulations showing that, under 12 h⁻¹ ventilation, equilibrium concentrations exceed the 1% safety threshold under these conditions. To address these gaps, this study proposes an adaptive ventilation strategy that uses variable-frequency drives to adjust ventilation rates in real time based on sensor feedback of gas concentrations, ensuring alignment with leakage conditions, thereby ensuring enhanced safety. These results provide crucial theoretical insights for the safe design of HBNG pipelines and ventilation optimization in utility tunnels. Full article

In order to explore new wall panel materials and structural systems suitable for prefabricated buildings, this study proposes a polypropylene fiber-reinforced concrete sandwich wall panel (PFRC sandwich wall panel) and a polypropylene fiber-reinforced concrete sandwich wall panel with glass fiber grid (G-PFRC sandwich wall panel). A comparative investigation was conducted using finite element analysis to numerically simulate the mechanical response of these composite wall panels under impact loads. The simulation results were compared with those of an unreinforced concrete sandwich wall panel with glass fiber grid (G-UC sandwich wall panel). Key findings include: (1) Compared with the G-UC sandwich wall panel, the G-PFRC sandwich wall panel exhibited 19.3% lower peak deformation and 23.7% reduced residual deformation; (2) Relative to the standard PFRC sandwich wall panel, the G-PFRC sandwich wall panel demonstrated 16.5% smaller peak deformation and 27.9% less residual deformation under impact loads; (3) Damage analysis revealed that the G-PFRC sandwich wall panel developed fewer cracks with lower damage severity compared to both the PFRC and G-UC sandwich wall panels. Parametric studies further indicated that the G-PFRC sandwich wall panel maintains superior deformation resistance and impact performance across varying impact heights and impact masses. The synergistic combination of polypropylene fiber with a glass fiber grid significantly enhances the impact resistance of composite sandwich panels, providing valuable theoretical insights for engineering applications of these novel wall systems in prefabricated construction. Full article

Background: Freeze tolerance is an uncommon but highly effective strategy that allows certain vertebrates to survive prolonged exposure to subzero temperatures in a frozen, ischemic state. While past studies have characterized the metabolic and biochemical adaptations involved, including cryoprotectant accumulation and metabolic rate suppression, the contribution of post-transcriptional gene regulation by microRNAs (miRNAs) remains largely unexplored. This study investigated freeze-responsive miRNAs in cardiac tissue of the gray tree frog, Dryophytes versicolor, to better understand the molecular mechanisms that support ischemic survival and tissue preservation. Methods: Adult frogs were subjected to controlled freezing at −2.5 °C, and cardiac tissue was collected from frozen and control animals. Total RNA was extracted and analyzed via small RNA sequencing to identify differentially expressed miRNAs, followed by target gene prediction and KEGG pathway enrichment analysis. Results: A total of 3 miRNAs were differentially expressed during freezing, with significant upregulation of miR-93-5p and let-7b-5p and downregulation of miR-4485-3p. Predicted targets of upregulated miRNAs included genes involved in immune signaling pathways (e.g., cytokine–cytokine receptor interaction), steroid hormone biosynthesis, and neuroactive ligand–receptor interaction, suggesting suppression of energetically costly signaling processes. Downregulation of miRNAs targeting cell cycle, insulin signaling, and WNT pathways indicates possible selective preservation of cytoprotective and repair functions. Conclusion: Overall, these results suggest that D. versicolor employs miRNA-mediated regulatory networks to support metabolic suppression, maintain essential signaling, and prevent damage during prolonged cardiac arrest. This work expands our understanding of freeze tolerance at the molecular level and may offer insights into biomedical strategies for cryopreservation and ischemia–reperfusion injury. Full article

Preeclampsia (PE) is not merely a pregnancy complication but a clinical manifestation of underlying vascular dysfunction with long-term health implications. It is diagnosed after 20 weeks of gestation as new-onset hypertension with proteinuria or organ involvement. The condition arises from impaired placental development, particularly defective spiral artery remodeling, which leads to placental ischemia and the release of antiangiogenic factors such as soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng). These circulating factors contribute to systemic endothelial dysfunction, resulting in hypertension, inflammation, and multiorgan stress. Histopathological findings, including acute atherosis and abnormal vascular remodeling, further reflect the cardiovascular damage underlying PE. This review synthesizes emerging evidence on the vascular and histological mechanisms of PE, highlighting novel biomarkers such as microRNAs and neprilysin, and the potential of advanced diagnostic tools, including machine learning. Importantly, PE is now recognized not only as an obstetric disorder but also as an early marker of future cardiovascular disease. This paradigm shift emphasizes the need for personalized prevention strategies, close surveillance of high-risk women, and long-term cardiovascular follow-up. Pregnancy thus represents a critical window for early detection and intervention in women’s cardiovascular health. Full article

Soybean (Glycine max L.) is one of the world’s most important sources of plant-based protein, with a protein content exceeding 35–40% (dry basis), along with other essential nutritional benefits. Ideally, soybeans are field-dried to approximately 13% moisture content (wet basis, wb); however, adverse weather conditions can necessitate harvesting at elevated moisture levels sometimes exceeding 20% (wb). In such cases, mechanized drying systems, particularly in northern U.S. regions, become essential for safe storage and quality preservation. This study investigated the effects of drying temperature, airflow rate, and initial moisture content on drying kinetics and kernel integrity using mathematical modeling. Drying behavior was modeled using fractional calculus and compared to the empirical Page model, while kernel cracking and breakage were analyzed using logistic regression. Both fractional and Page models exhibited strong agreement with experimental data (R² = 0.903–0.993). The fractional model achieved superior predictive accuracy, improving RMSE and MAE by 83.7% and 81.2%, respectively, compared to the Page model. Cracking and breakage were more strongly influenced by drying temperature than by initial moisture content, with the greatest quality degradation occurring at high temperatures. Optimal drying conditions were identified as temperatures below 27 °C and initial moisture contents between 19 and 20% (wb), which best preserved kernel quality. Logistic models more accurately predicted breakage than cracking, confirming their effectiveness in assessing mechanical damage during drying. The results affirm the suitability of fractional order models for accurately capturing drying kinetics, while logistic models offer robust performance for evaluating physical quality degradation. These modeling approaches provide a framework for efficient and quality-preserving soybean drying strategies in regions reliant on off-field drying systems. Full article

Fatigue damage failure is a process where the mechanical properties of different materials continuously degrade under the action of cyclic loads. The cumulative analysis of fatigue damage has a significant impact on the service structure of major equipment. This paper starts from the mechanism of fatigue damage evolution, comprehensively considers the influence of the order of high-low cycle load mixed cyclic loading on the fatigue life performance, and based on the Manson-Halford nonlinear fatigue damage accumulation theory and the mechanism of relative cumulative damage, a new nonlinear damage accumulation fatigue life model is established, and a fatigue damage accumulation influencing factor D_cr is introduced to improve the prediction accuracy of the model. The new model proposed in this paper is verified through multi-level fatigue load data. By comparing the prediction results with other models under the same experimental conditions, the fatigue life prediction error precision of the new model is the best in similar cases, generally with an error precision between 10% and 20%, which proves the effectiveness and accuracy of the nonlinear damage accumulation model proposed in this paper. At the same time, the improved method in this paper has better stability while ensuring prediction accuracy. Full article

Primary Sjögren’s syndrome (pSS) is a chronic, autoimmune rheumatic disease characterized by progressive lymphocytic infiltration of the exocrine glands, leading to inflammation and subsequent tissue damage. As a multifactorial disease, its etiology is complex, making it difficult to predict disease progression. Among the environmental factors implicated in pSS, the involvement of microorganisms has gained increasing attention. Since the launch of the Human Microbiome Project, growing evidence has highlighted the role of dysbiosis in the pathogenesis of various autoimmune diseases, including pSS. Shifts in the abundance of specific bacterial phyla can lead to corresponding changes in the levels of key microbial metabolites involved in tissue homeostasis and immune regulation—such as short-chain fatty acids (SCFAs), choline, taurine, serine, lactate, and tryptophan and their metabolites. Understanding the mechanisms by which these metabolites influence immune processes may provide deeper insights into the progression of the disease. Therefore, this review aims to explore the mechanisms through which microbiota-derived metabolites contribute to the pathophysiology of primary Sjögren’s syndrome. Full article