Search Results (1,022)

This study investigates the hydrogen embrittlement susceptibility of laser melting deposition (LMD)-produced Ti-6Al-4V alloy with different build orientations (0°, 45°, 90°) through electrochemical hydrogen charging, slow strain rate testing, and microstructural characterization. Ti-6Al-4V alloys are widely used in marine and offshore engineering, where cathodic protection and corrosion reactions can generate hydrogen, leading to hydrogen ingress and potential embrittlement. Results show that prolonged hydrogen charging induces hydride formation, α-phase fragmentation, and β-phase dissolution, significantly degrading corrosion resistance and mechanical properties. Hydrogen embrittlement susceptibility exhibits notable anisotropy: elongation reductions for 0°, 45°, and 90° specimens are 40.1%, 40.8%, and 29.4%, respectively. The relatively superior resistance observed in the 90° orientation may be associated with its single-layer structure and more uniform dimple distribution. In contrast, the multilayer interfaces in other orientations are likely to serve as preferential sites for hydrogen accumulation, which may contribute to the increased embrittlement susceptibility. This research reveals the failure mechanism of LMD Ti-6Al-4V in hydrogen environments and supports its application in marine engineering. Full article

This paper investigates the low-cycle behaviour of Concrete-Filled steel Tubes (CFTs) subjected to cyclic pure bending, a loading condition representative of large bridge and building girders. A 3D finite element model is developed in Abaqus/Explicit, combining a ductile damage law for the steel tube and Concrete-Damaged Plasticity for the infilled concrete, and is calibrated against large-scale cyclic bending tests on circular and square CFT beams. An automated Python scripting framework is then used to perform a systematic parametric study on members made of standard code-based materials, varying diameter-to-thickness ratio and span length over a wide range of practical configurations. Constant-amplitude chord rotations are imposed, and the nonlinear response is tracked in the plastic range while material damage evolves. The hysteretic behaviour is quantified in terms of cumulative plastic strains, dissipated energy and the degradation of reaction force and bending moment after 25 cycles. The results show that geometric parameters strongly affect the cyclic response: within the investigated loading layer, configurations with D_e = 100 mm generally exhibit strength degradation values between about 10% and 60%, whereas for D_e = 400 mm the degradation typically ranges between 50% and 100%, with most cases falling in the moderate-to-severe degradation domain. At the same time, larger diameters and thicker tubes generally lead to an increase in dissipated energy, while longer members tend to show lower energy dissipation but also reduced degradation. The study therefore provides a reproducible computational framework and comparative performance trends for the assessment of low-cycle cyclic response in CFT beams under a prescribed loading protocol. Full article

The COVID-19 pandemic intensified communication challenges for community college leaders navigating prolonged uncertainty and organizational disruption. This qualitative study examines how community college administrators described and interpreted their communication practices during the pandemic. Guided by the Elaboration Likelihood Model (ELM), this study explores how leaders made sense of message design, audience responsiveness, and trust under conditions of information overload and emotional strain. Semi-structured interviews were conducted with twelve administrators from community colleges across the United States, including presidents, vice presidents, and senior-level directors. Data were analyzed using reflexive thematic analysis. Five themes emerged: communication breakdowns between employee groups; tailored messaging for specific constituencies; preferences for in-person and interactive communication; trust-building through transparency; and reliance on collaborative communication structures. Participants described communication as an ongoing relational and organizational practice rather than a one-time transmission of information. Administrators reported adapting strategies by combining repetition, audience-specific framing, interactive formats, and structural supports to manage uncertainty and sustain institutional trust. Findings are not intended to be generalizable but provide contextually grounded insight into leadership communication during an extended crisis. This study contributes to scholarship on higher education leadership and crisis communication by illustrating how persuasion, sensemaking, and relational cues intersected in administrators’ communication practices. Full article

With the vigorous promotion of the modernization of China’s construction industry, the proportion of prefabricated buildings in new construction projects has increased steadily. Grouted sleeve connection is a mainstream joining method for prefabricated components, and the performance of grouting materials is crucial to connection reliability. In this study, a modified polyurethane composite (MPC) was developed as a novel sleeve grouting material, and seven grouted splice specimens with different steel bar strength grades and anchorage lengths were fabricated for uniaxial tensile tests. The mechanical properties of MPC and the connection performance of specimens were systematically investigated, and the effects of steel bar strength grade and anchorage length on ultimate load, average bond strength, and strain characteristics were quantitatively analyzed. The results show that MPC has excellent fluidity, and its mechanical strengths meet the specified requirements. Increasing steel bar strength grade and anchorage length significantly improves ultimate load: at a 6d anchorage length, the ultimate load of the S600 series (HRB600E) is 44.85% higher than that of the S400 series (HRB400E); extending the S400 series’ anchorage length from 4d to 8d increases ultimate load by 50.61%. Average bond strength decreases with increasing anchorage length (S400-MPC-8d is 24.70% lower than S400-MPC-4d) but increases with higher steel bar strength grade (S600-MPC-6d is 32.37% higher than S400-MPC-6d). The sleeve remains elastic during the test, ensuring safety. Prediction formulas for average bond strength under slip failure were established, with good agreement between predicted and experimental results. For both HRB400E and HTRB600E steel bars, considering safety and installation errors, a critical anchorage length of 8d is recommended for engineering design. Full article

The Third Plague Pandemic originated in 19th-century Yunnan, China, yet the confluence of factors that enabled the pandemic strain Yersinia pestis 1.ORI to emerge and spread globally remains unclear. Using a One Health framework, this study investigates how human-driven ecological and socioeconomic changes disrupted zoonotic barriers in Yunnan. We conduct an interdisciplinary historical analysis, triangulating evidence from Qing dynasty gazetteers, environmental reconstructions, and biological data on plague ecology, including host–vector dynamics, to model conditions for spillover and spread and to build a convergent, validated case. The analysis identifies a mid-19th-century convergence that created a high-risk interface: widespread deforestation from mining and agriculture, rapid population growth, increased synanthropic rat densities, and the turmoil of the Panthay Rebellion. Socioeconomic stressors—labour migration into mining valleys, currency devaluation undermining food security, and comorbidities such as malnutrition, heavy metal contamination, and opium use—may have further increased host susceptibility. This socio-ecological context catalysed spillover and establishment of the 1.ORI strain in commensal rat populations. The findings show the pandemic’s origin reflects spatiotemporal convergence rather than a single cause, while noting uncertainty in quantifying historical ecological and health parameters; the case offers a framework for assessing contemporary pandemic risks. It underscores how layered pressures operate across timescales. Full article

Shot-hole disease caused by Wilsonomyces carpophilus poses a significant threat to stone fruit species, including wild apricot (Prunus armeniaca L.). This study investigated pathogenic factors (cell wall-degrading enzymes and toxins) and metabolites produced by a highly pathogenic strain (CFCC 71544) and a weakly pathogenic strain (CFCC 71543) of W. carpophilus during infection of P. armeniaca (in planta conditions). Analysis using the 3,5-dinitrosalicylic acid colorimetric method revealed that polygalacturonase (CFCC 71544: 1367.02 U/g; CFCC 71543: 1264.00 U/g) and polymethylgalacturonase (CFCC 71544: 1898.71 U·g⁻¹; CFCC 71543: 1762.21 U·g⁻¹) were the most active cell wall-degrading enzymes, with higher activities observed in the highly pathogenic strain (CFCC 71544). Crude toxins from CFCC 71543 induced leaf lesions averaging 41.91 mm² and retained activity after exposure to 121 °C and UV treatment. Non-protein fractions of the toxins caused significantly larger lesions than protein fractions (15.93 mm² vs. 5.56 mm², respectively). Building on these in planta findings, we further characterized toxin properties under controlled laboratory conditions (in vitro). Optimal toxin production conditions were identified in Richard culture medium at pH 4, under a 12 h light/dark cycle, shaken for 12 days at 25 °C. Untargeted metabolomics identified 3244 compounds and 977 differential metabolites among mycelia, crude toxins, and the residual aqueous phase after organic solvent extraction; these metabolites were predominantly amino acids and derivatives and organic acids. These findings indicate that the main pathogenic factors of W. carpophilus are highly active polygalacturonase and heat/UV-stable, water-soluble, non-protein toxins, providing a theoretical basis for shot-hole disease prevention and control. Full article

Parenting research and policy increasingly emphasize visible practices, measurable outcomes, and parental effort as indicators of competence. Across welfare, education, and family intervention contexts, “good parenting” is often evaluated through intensive doing: monitoring, documenting, optimizing development, and managing risk. While these frameworks foreground parental responsibility, they frequently obscure the relational dimensions of care and intensify existing classed, gendered, and racialized inequalities. Building on feminist scholarship that has long conceptualized parenting as relational, ethical, and socially situated, this paper develops a theoretical framework for rethinking parenting by integrating family studies scholarship on intensive parenting, emotional labor, and inequality with Hannah Arendt’s distinctions among labor, work, and action. Parenting is commonly framed as labor, the daily work of sustaining children’s lives, or as work, the longer-term project of producing competent future adults. Drawing on Arendt’s concept of action, the paper reinterprets parenting as a relational practice grounded in presence, responsiveness, and mutual recognition. Using illustrative examples from diverse family contexts, including Indigenous and immigrant communities, the analysis shows how privatized and performance-oriented models of care place strain on families while rendering collective forms of support less visible. The paper concludes by outlining implications for family research and policy, including a shift from outcome-based evaluation toward relational engagement and from individualized responsibility toward strengthened social infrastructures of care, arguing for greater attention to relational care, shared responsibility, and the structural conditions that shape parenting practices and family well-being. Full article

Steel–concrete composite beams are widely used in building and bridge engineering; however, the impact response of Steel–Coarse Aggregate–Ultra-High Performance Concrete (Steel–CA–UHPC) composite beams remains insufficiently quantified, and no beam-specific dynamic capacity formula is available. To address this gap, companion static testing and drop-weight impact tests were performed on full-scale simply supported steel–CA–UHPC composite beams under single and repeated impacts, followed by development of a strain-rate-dependent dynamic increase factor (DIF) model and a capacity prediction framework. The companion static specimen reached 448 kN, whereas the 5 m impact cases produced peak forces of 930.0–940.4 kN, corresponding to 2.08–2.10 times the static level, with the initial peak forming within 1.0–1.1 ms. Dynamic failure was marked by rapid mid-span cracking of the CA–UHPC slab and brittle shear fracture of studs, while repeated impacts mainly accelerated cumulative damage before the final high-energy strike. Static–dynamic displacement comparison further revealed much more abrupt deformation concentration under impact loading. A revised static capacity formula reduced the prediction error from 4.46% for the code-based method and 1.00% for the literature model to 0.74%. Combined with the fitted DIF–strain-rate relation, the proposed framework reproduced the measured dynamic capacities with errors of −4.63% to 9.75%. The study provides member-level evidence and a practical DIF-based method for evaluating the impact resistance of steel–CA–UHPC composite beams. Full article

This study investigates the fracture initiation and propagation mechanisms of continuously reinforced concrete–asphalt (CRC+AC) composite pavements under the synergistic effects of diurnal temperature fluctuations and non-uniform tire loading. A three-dimensional (3D) thermo-mechanical coupled finite element (FE) model was developed, with its underlying mechanical framework validated through laboratory-scale model tests conducted at 20 °C. The experimental results, involving strain monitoring at varying depths, demonstrated a high degree of consistency with numerical predictions in terms of spatial strain distribution, thereby ensuring the model’s reliability in capturing interlayer load-transfer efficiency. Building upon this validated mechanical foundation, numerical simulations were extended to analyze the low-temperature fracture response. The numerical results indicate that the maximum longitudinal and transverse tensile stresses in the asphalt layer are concentrated at the pavement surface, whereas the maximum shear stress occurs at a depth of 2–3 cm near the leading and trailing edges of the wheel load. Under low-temperature gradients, the Mode I stress intensity factor (K_I) at the crack tip exhibits a distinct diurnal opening–closing–reopening pattern, peaking at approximately 220 kPa·m^1/2 during the early morning hours (05:00–06:00). Furthermore, numerical simulations reveal the significant sensitivity of shear-sliding to axle loads; specifically, the peak Mode II stress intensity factor (K_II) increases monotonically from 190 to 230 kPa·m^1/2 as the axle load rises from 10 t to 16 t. Under non-uniform contact pressure, longitudinal cracking is primarily characterized by a mixed Mode I and Mode II mechanism driven by coupled tensile and shear stresses, whereas transverse cracking is dominated by Mode II shear failure. These findings suggest that implementing targeted traffic restrictions for overloaded vehicles during identified high-risk time windows can significantly enhance the structural durability and service life of composite pavements in cold regions. Full article

Molten Metal Jetting (MMJ) is an emerging metal additive manufacturing process that produces components via on-demand jetting of discrete droplets. This paper reports properties of T6 heat-treated AlSi7Mg alloy produced in different build orientations via MMJ. A Xerox ElemX machine was used to print AlSi7Mg coupons in horizontal, tilted, and vertical orientations. The aluminum feedstock was melted at 825 °C and was printed onto a 475 °C heated print bed using a jetting frequency of 400 Hz and a drop spacing of 500 μm. Coupons were heat treated to a T6 temper. The average yield strengths of heat-treated coupons in vertical and horizontal orientations were 240.4 ± 7.3 MPa and 244.6 ± 7.1 MPa respectively. This indicates that the vertical build orientation had minimal adverse effect on strength. However, average strain (11.5% ± 1.2% versus 14.6% ± 3.5%) values for the vertical and horizontal orientations, respectively, showed more pronounced effects. X-ray CT analysis of vertically oriented coupons revealed increases in porosity in material deposited above heights of ~90 mm. Above this build height, the measured surface temperature dropped below ~455 °C. External heating methods are therefore advised in order to maintain a surface temperature ≥ 455 ° and avoid excess porosity. Full article

The development of green building materials and high-performance concrete has promoted the use of manufactured sand (MS) in self-compacting concrete (SCC). To investigate the effect of MS lithology on concrete performance, this study prepared C40-SCC using basalt, limestone, and granite manufactured sand, as well as river sand. Workability and mechanical properties were measured via macro-scale tests. A meso-scale random aggregate model, including mortar, aggregate, and interfacial transition zone (ITZ), was established to simulate uniaxial compression. The macro-test results indicate that workability decreases in the order of river sand, granite, limestone, and basalt, while mechanical strength decreases in the order of granite, limestone, basalt, and river sand. The meso-scale simulation reveals that damage initiates at the ITZ and extends into mortar. The simulated stress–strain curves match the experimental data in the ascending branch, with peak stress errors between 1.1% and 6.9%. The failure modes also align with experimental observations. The consistency between the simulation and experimental results verifies the reliability of the meso-scale model. By combining macro-experiments and meso-simulation, this study compares concrete performance and explains the differences from the perspective of damage evolution. The results indicate that MS lithology affects interfacial properties and damage development, thereby determining macro-mechanical behavior. This research provides a theoretical basis for the appropriate selection of MS in SCC. Full article

Alkenylidenecyclopropanes (ACPs) have emerged as versatile and highly reactive building blocks in transition-metal-catalyzed transformations. Their strained cyclopropane framework, combined with an exocyclic alkene, enables diverse bond-activation pathways and promotes efficient cycloaddition reactions. In recent years, ACPs have been widely developed as three-carbon synthons in a variety of higher-order cycloadditions. This review provides a systematic overview of transition-metal-catalyzed ACP transformations, focusing on their applications in [3+2], [3+2+2], [3+2+1], [4+3], and [4+3+2] cycloaddition reactions with reaction partners such as alkenes, alkynes, carbonyl compounds, imines, dienes, and carbon monoxide. Particular attention is given to mechanistic aspects, including cyclopropane ring-opening processes and the formation of key metal–carbene and π-allyl intermediates that govern reactivity and selectivity. Factors influencing regioselectivity, stereoselectivity, and catalyst design are also discussed. The synthetic potential of ACP chemistry is illustrated through representative applications in the total synthesis of complex natural products, such as pyrovellerolactone and (+)-zizaene. Overall, this review highlights recent advances in ACP-based cycloaddition strategies and emphasizes their growing significance in modern synthetic chemistry. Full article

Sustainable xanthan gum (XG) production is increasingly prioritized as global demand rises, and conventional processes face economic and environmental constraints. Traditional manufacturing depends heavily on refined sugars, intensive fermentation control, and solvent-based purification, which elevate production costs and ecological impact. This review highlights recent advancements designed to improve sustainability across the XG value chain, focusing on alternative substrates, optimized fermentation, and greener extraction methods. Agricultural residues, food-processing waste, lignocellulosic biomass, and industrial effluents have emerged as promising low-cost substrates that reduce reliance on refined sugar sources while supporting waste valorization. Pretreatment strategies, such as acid hydrolysis, enzymatic processing, and integrated biological–chemical methods, significantly enhance the accessibility of complex biomass for microbial fermentation. Concurrently, improvements in strain selection, metabolic engineering, and process control have increased XG yield, molecular weight, and rheological performance. Environmentally friendly extraction technologies, including ultrasound-assisted extraction, pulsed electric fields, membrane filtration, and electro-dewatering, further reduce solvent consumption and energy demand in downstream processing. However, challenges persist, including substrate variability, formation of inhibitory compounds, strain instability, and regulatory considerations for waste-derived substrates or genetically modified strains. Future progress will rely on integrating bioprocess intensification, genetic engineering, and techno-economic assessment to build scalable, low-impact, and circular XG production systems. Full article

Background/Objectives: Healthcare professionals operate in complex and demanding environments characterized by high workloads, emotional strain, and organizational pressures that can undermine well-being. According to Self-Determination Theory, the fulfillment of core psychological needs (autonomy, competence, and relatedness) leads to increased job satisfaction, a key indicator of occupational well-being. Additionally, leadership plays a central role in shaping needs-fulfilling environments. Drawing on Leader–Member Exchange Theory (LMX), which emphasizes that high-quality leader-follower relationships foster greater discretion, provide learning opportunities, and build constructive team interactions, this study aimed to examine whether supportive leadership is associated with job satisfaction through the mediation of autonomy, team task cohesion, and perceived training opportunities. Methods: Data were collected from a local health authority in Northern Italy through an anonymous online survey, completed by 697 healthcare professionals, including 546 non-medical healthcare staff (primarily nurses) and 151 physicians. Structural equation modeling with a robust maximum likelihood estimator was employed to test the mediation model, including professional role as a covariate. Results: Higher LMX was positively and directly associated with job satisfaction, through the partial mediation of autonomy, team cohesion, and training opportunities, all positively associated with satisfaction. Team task cohesion showed the strongest associations with both LMX and satisfaction. Physicians reported slightly higher levels of autonomy, training opportunities, and job satisfaction than non-medical professionals. Conclusions: The findings suggest that supportive leadership contributes to healthcare professionals’ job satisfaction both directly and indirectly by contributing to core needs fulfillment. Interventions that strengthen relational quality, promote team cohesion, and enhance professional development may help sustain well-being and adaptive functioning in high-demand healthcare environments. Full article

Squeezed branch piles, originally developed for building and bridge foundations, have been downsized and deployed at larger pile spacing for reinforcing embankments over soft soils. However, the working mechanism of squeezed branch pile-supported embankments remains unclear. In this study, a three-dimensional numerical model of this embankment was established based on field tests. The analyses consider different pile types (squeezed branch piles and straight piles) and pile-head structures (beam-type cap and plate-type cap). These concrete components were modeled utilizing an advanced concrete model, which captures the strain-softening/hardening and yielding behavior. Simulation results show that squeezed branch piles provide better settlement control in the subsoil beneath the embankment than straight piles for the studied cases. The beam-type cap with squeezed branch piles behaves as a pile-beam foundation that reduces maximum settlement by around 38% compared to that of the plate-type cap, while the plate-type cap system functions as a composite foundation that enhances surcharge capacity by about 35–40%. The instability of the embankment is driven by tensile failure in concrete: The beam-type cap leads to a localized failure along the ground beam, and the plate-type cap system induces a progressive failure centered on the squeezed branch piles. Within the plate-type cap, the dimensions of the pile-head plate significantly influence settlement control and the stability of the embankment in soft soil. Full article