Search Results (5,461)

School bullying climate is a known risk factor for adolescent mobile phone dependence, yet the mechanisms linking these two constructs and the boundary conditions of protective factors remain underexplored. The present study aimed to examine the mediating role of emotional regulation difficulties in the relationship between school bullying climate and mobile phone dependence among left-behind children, as well as the moderating role of psychological resilience in this mediating pathway. The final analytical sample consisted of 300 left-behind children who completed two waves of surveys separated by a six-month interval. Participants completed the School Bullying Climate Scale, the Brief Difficulties in Emotion Regulation Scale, the Mobile Phone Dependence Scale, and the Psychological Resilience Scale. Data were analyzed using the PROCESS macro for SPSS (Model 4 for mediation and Model 58 for moderated mediation), controlling for age, gender, and baseline mobile phone dependence. School bullying climate was significantly positively correlated with mobile phone dependence among left-behind children six months later (r = 0.14, p < 0.05), and emotional regulation difficulties mediated this relationship (indirect effect = 0.03, 95% CI = [0.001, 0.077]). Psychological resilience significantly moderated the path from school bullying climate to emotional regulation difficulties (b = 0.19, p < 0.05). Specifically, for left-behind children with high psychological resilience, the relationship between school bullying climate and emotional regulation difficulties was significant (b = 0.29, p < 0.01); for those with low psychological resilience, this relationship was not significant (b = 0.02, p > 0.05). Notably, psychological resilience played a conditional moderating role: only under a low school bullying climate is high psychological resilience associated with lower emotional regulation difficulties in left-behind children. Full article

The rapid diffusion of generative AI is profoundly transforming knowledge-intensive work and reshaping how employees innovate. Although prior research has highlighted the positive role of generative AI in improving work efficiency and performance, the underlying mechanisms through which it promotes employee creative behavior remain insufficiently understood. Drawing on Social Cognitive Theory and Psychological Safety Theory, this study develops a moderated dual-path model to examine how generative AI use influences employee creative behavior through creative self-efficacy and psychological safety. Using a three-wave time-lagged survey design, data were collected from 297 employees in highly digitalized industries. The results indicate that generative AI use is positively associated with subsequent self-reported employee creative behavior. Both creative self-efficacy and psychological safety significantly mediate this relationship. Furthermore, digital leadership strengthens the positive effects of generative AI use on creative self-efficacy and psychological safety, thereby further enhancing its indirect effects on employee creative behavior. The findings not only extend the literature on generative AI and employee creative behavior but also deepen the theoretical understanding of AI empowerment mechanisms by identifying two critical pathways: a capability-enhancement pathway and a risk-reduction pathway. This study provides important theoretical insights and practical implications for organizations seeking to effectively leverage generative AI to foster employee creative behavior in the context of digital transformation. Full article

Accurate measurement of attenuation during acoustic wave propagation in viscoelastic solid media is of theoretical and practical significance. Conventional studies primarily rely on analogies to models of electromagnetic wave attenuation in non-ideal media. Many modern models of acoustic attenuation rely on continuum mechanics and complex material properties. Although there are similarities between acoustic and electromagnetic waves, conventional models overlook their fundamental physical differences and neglect the influence of particle-vibration damping in viscoelastic media. Additionally, in applications with a single-transmitter and dual-receiver configuration, the effects of specific characteristics on the measurement of the acoustic attenuation coefficient are eliminated in both the electric–acoustic conversion of the transmitting transducer and the acoustic–electric conversion of the receiving transducer. The discrepancies in geometric parameters (size and shape) between the two measurement modules lead to inconsistent frequency responses, thereby introducing measurement errors in acoustic attenuation. To address these issues, we investigate the coupling mechanism between particle vibration damping and wave propagation attenuation, derive an analytical expression for the acoustic attenuation coefficient that accounts for this coupling, and propose a new method for accurately measuring acoustic attenuation in viscoelastic solid media. The experimental results validate the theoretical predictions of acoustic attenuation. Full article

Depth-averaged 2D models have shown considerable success at predicting the presence of tidal sand ridges in the nearshore environment while only requiring minimal efforts of parameter tuning. 3D models, on the other hand, fail to predict the growth of coarse-grain sand waves unless unrealistic assumptions on eddy viscosity are applied. When a vertically varying eddy viscosity profile is adopted in the model, sand waves will invariably be the fastest growing mode unless suspended load dominates, which contradicts observations. Through both numerical and analytical approaches, this paper will show that the residual circulation in the vertical plane due to mass continuity and vertical shear is a possible underlying mechanism that accounts for the dominant growth of sand waves. The strength of this residual circulation is proportional to the shear of the tidal velocity. A consequence is that sand ridges are more likely to develop in certain models with a small slip parameter in the bottom boundary condition (hence, less shear in tidal velocity), and such a parameter choice often, though not necessarily, leads to stronger mixing due to model configurations. Hence, sand waves are favoured in coastal seas due to the strong shear of the tidal current. The above findings suggest that there could be some unresolved processes that cause a transition in the bedform-building mechanism, which eventually inhibits the growth of sand waves and promotes the growth of sand ridges. Full article

Understanding the physical mechanisms of compound hot-drought events (CHDEs) over the Yangtze River Basin (YRB) is essential for improving climate predictability. Using high-resolution observations and ERA5 reanalysis, this study conducted a three-dimensional comparative diagnosis of two spatially distinct CHDEs (August 2022 and 2019), deconstructing their circulation dynamics and thermodynamic budgets. Specifically, the 2022 basin-wide event was highly associated with La Niña and a negative Indian Ocean Dipole (NIOD). Anomalous latent heating in the tropical eastern Indian Ocean favored an extensive meridional Hadley circulation and a deep high-pressure belt, blocking southwest moisture transport. Thermodynamically, intense downward vertical motions produced severe descending adiabatic warming, which offset longwave radiational cooling and sustained anomalous heat accumulation throughout the deep troposphere. Conversely, the 2019 localized event occurred under a weak Central Pacific El Niño and a positive IOD. The anomalous tropical cooling weakened systematic subsidence and provided a favorable background for a Rossby wave train, featuring an offshore cyclone over the Western North Pacific that severed moisture pathways. Characterized by shallower vertical subsidence, the lack of a penetrative adiabatic heat source merely maintained a lower-level thermodynamic balance, confining extreme heat to the central–eastern YRB. Although superficially similar at the surface, these CHDEs are sustained by two distinct ocean–atmosphere interaction paradigms. Clarifying these dual paradigms provides a critical physical basis for improving sub-seasonal prediction. Full article

This study pivots from the universally beneficial view of servant leadership and examines how leader gender shapes its effectiveness evaluations through followers’ warmth and competence perceptions. Combining role congruity theory and the stereotype content model, we propose a congruity trap model and suggest that servant leadership produces different effectiveness evaluations depending on leader gender. Specifically, we hypothesize that servant leadership interacts with leader gender to produce divergent warmth and competence perceptions, and these perceptions in turn lead to perceived leadership effectiveness. In a 2 × 2 between-subjects online experiment (Study 1; N = 298), we found that servant leadership and leader gender interacted to predict both warmth and competence perceptions as hypothesized. In a three-wave time-lagged field study with full-time employees in China (Study 2; N = 194), we obtained partial support that the servant leadership and leader gender interaction was significant for competence perceptions but not for warmth perceptions. Gender-contingent differences in perceived effectiveness were more clearly transmitted through the indirect pathway involving competence. Taken together, these findings suggest that the competence perceptions constitute the more consistent mechanism through which servant leadership behaviors produce divergent evaluation outcomes for female and male leaders. Overall, our model and findings reveal that the benefits of servant leadership are not equally available to all leaders, illuminating how gender stereotypes create divergent evaluation outcomes from identical leadership behaviors. Full article

As mineral resource extraction progressively extends to greater depths, the complex deep underground environment poses severe corrosion-induced deterioration risks to anchoring structures such as rock bolts. Anchorage failure has thus become a critical safety concern constraining the stability of deep roadways. To address the failure mechanisms of anchoring systems under multi-physical field coupling effects, this study conducts numerical simulations of multi-field corrosion processes and ultrasonic nondestructive testing (NDT) based on a numerical modeling platform. The influence of temperature on corrosion rate and current density is systematically analyzed, and interface response characteristics are extracted and interpreted for defects of varying dimensions. A spatial complementary mechanism under different corrosion defect configurations is revealed, and a health diagnosis system incorporating multiple critical indicators is established. The results indicate that elevated temperature significantly accelerates bolt corrosion: the rise in temperature shifts the equilibrium potential negatively and exponentially increases the reaction rate constant, both of which synergistically promote anodic dissolution. In ultrasonic testing, monitoring points along the main axis are positioned within the transmission-focused zone, where defects induce acoustic wave diffraction and superposition such that even minor defects cause a multiplication of the dominant frequency. Lateral monitoring points lie in the reflection–interference zone, where small defects preferentially attenuate energy, while larger defects manifest as amplitude reduction and first-arrival wave lag; all characteristic indices increase monotonically with defect size. Based on the numerical simulation outcomes, a four-level grading diagnosis standard and a “bottom–lateral” detection scheme are proposed as simulation-based reference indicators. The model effectively reproduces both corrosion deterioration and acoustic wave propagation characteristics, thereby providing a quantitative basis for the assessment of anchoring structures in high-temperature deep underground environments. Full article

Vascular aging is a key determinant of cardiovascular risk and is characterized by endothelial dysfunction, oxidative stress, inflammation, arterial stiffness, and alterations of the endothelial glycocalyx. In recent years, increasing scientific interest has focused on whether selected nutritional supplements can modulate these mechanisms. The objective of this narrative review is to summarize and critically evaluate the current evidence regarding the effects of selected nutritional supplements on endothelial function and vascular health, with emphasis on their proposed mechanisms of action, available preclinical and clinical evidence, and current limitations. This review examines nutritional supplements targeting nitric oxide biology (L-arginine/L-citrulline and citrulline derived from watermelon), polyphenol-rich foods and extracts (cocoa flavan-3-ols and grape polyphenols), mitochondrial redox balance (coenzyme Q10 and the mitochondria-targeted antioxidant MitoQ), endothelial glycocalyx-supporting formulations, olive-derived bioactive compounds, curcumin, and S-allyl cysteine. Across studies, improvements have been reported primarily in surrogate vascular endpoints, including flow-mediated dilation, pulse wave velocity, and blood pressure, although effect sizes vary and substantial heterogeneity exists among studies. Overall, current evidence suggests that several nutritional supplements may improve surrogate markers of vascular function; however, evidence demonstrating reductions in major cardiovascular events or cardiovascular mortality remains limited. Future research should prioritize adequately powered randomized controlled trials with longer follow-up, standardized supplement formulations, and clinically meaningful cardiovascular outcomes to more clearly define the role of nutritional supplements in cardiovascular prevention. Full article

Cemented coal gangue backfill (CCGB) is an important material for the resource utilization of mining solid waste, and its long-term stability is strongly affected by aggregate gradation. In this study, aggregate mass fractal dimension was used to characterize the particle size distribution of coal gangue, and four gradation schemes with different fractal dimensions were designed. Uniaxial compressive strength (UCS) tests, stepwise accelerated creep tests, acoustic emission (AE) monitoring, and scanning electron microscopy (SEM) observations were conducted to investigate strength, creep behavior, crack evolution, and damage mechanisms. The results show that P-wave velocity and UCS exhibit generally non-monotonic variations with fractal dimension, with relatively high values in the intermediate fractal-dimension range. The empirical long-term strengths for $D=2.20$, 2.41, 2.59, and 2.79 are 6.62, 8.83, 7.34, and 7.07 MPa, respectively. AE results indicate that shear cracking first decreases and then increases with fractal dimension, reaching the lowest proportion of 41.8% at $D=2.41$. SEM observations show that an intermediate fractal dimension improves skeleton continuity and interfacial integrity, thereby suppressing shear-related damage and delaying creep instability. These findings demonstrate that aggregate mass fractal dimension is an effective structural parameter for linking gradation characteristics, creep resistance, and damage evolution of CCGB. Full article

Colloidal crystals permeated by mobile ions exhibit a coupling between electrostatic and elastic degrees of freedom that renormalizes the effective screening length and induces wave-vector-dependent elastic softening. Building on our recently proposed continuum model, we perform a rigorous Gaussian fluctuation analysis to elucidate the stability limits of the homogeneous phase. By integrating out the electrostatic fluctuations, we derive the effective elastic modulus $\Gamma \left(q\right)$ as a function of wave vector q. We show that the modulus in the long-wavelength limit ($q\to 0$) remains identically equal to a bare modulus protected by perfect ionic screening. In contrast, the modulus in the short-wavelength limit ($q\to \infty$) softens as the electrostatic-elastic coupling strength $\xi$ increases, vanishing at a critical value $\xi =1$. For $\xi >1$, the fluctuation spectrum exhibits a negative eigenvalue for all wave vectors q larger than a critical (effective screening) wave vector $q_c$, signaling an ultraviolet instability of the uniform phase. In a real colloidal crystal, this divergence is regulated by the discrete lattice cutoff $q_{\max }\sim \pi /a$, confining the physical instability to a finite band $q_c<q<q_{\max }$. The macroscopic limit $q\to 0$ remains unconditionally stable for all $\xi$. The transition at $\xi =1$ thus marks the onset of short-wavelength mechanical failure, while macroscopic elastic stiffness remains intact. Our analysis clarifies the proper physical interpretation of the minimal coupling model and provides a consistent picture of how non-DLVO interactions can drive local structural collapse in charged colloidal crystals. Full article

Acquired myasthenia gravis (MG) is an autoimmune disorder of the neuromuscular junction caused by antibodies against the acetylcholine receptor, leading to generalized muscle weakness and, in severe cases, respiratory muscle paralysis. While MG is well described in dogs, it is rarely reported in cats, and fulminant cases with rapid progression have a poor prognosis. An 11-year-old neutered female Persian cat presented with acute hindlimb weakness, which progressed to tetraplegia within 4 days. The clinical course initially resembled acute polyradiculoneuritis, and electromyography revealed positive sharp waves and fibrillation potentials. Diagnostic imaging identified a cystic cranial mediastinal mass without megaesophagus. Worsening respiratory muscle paralysis prompted surgical excision of the mass via left intercostal thoracotomy. Postoperatively, the cat developed persistent respiratory failure requiring re-intubation, mechanical ventilation, and temporary tracheostomy. Histopathological and immunohistochemical examination confirmed a thymoma, and serum acetylcholine receptor antibody levels were markedly elevated, establishing the diagnosis of thymoma-associated fulminant MG. Despite tumor excision and medical therapy with pyridostigmine and prednisolone, the cat remained ventilator-dependent and was euthanized on postoperative day 3. This case emphasizes early recognition of respiratory compromise, prompt diagnostic confirmation, intensive ventilatory support, and consideration of adjunctive immunomodulatory therapies. Full article

During load rejection in pumped-storage power stations, the rotational speed of the pump-turbine increases abruptly. The consequent structural deterioration of the internal flow induces high-amplitude hydraulic excitations, posing a serious threat to the operational stability of the unit. This study investigates a Francis pump-turbine to elucidate its flow evolution and instability mechanisms during load rejection. The fluid is modeled as weakly compressible water to capture finite pressure wave propagation. Dynamic mesh simulates guide vane closure, while vortex identification and short-time Fourier transform analyze transient pressure pulsations. The results indicate that the transient process can be sequentially divided into four typical stages—turbine mode, turbine-braking mode, reverse-pump mode, and return-to-turbine mode—to account for the most critical periods during the load rejection transient. The unit exhibits the poorest stability near the maximum rotational speed (443.34 r/min), where flow reversal and the full development of vortex structures significantly amplify fluctuations in hydraulic thrust. The vaneless space is identified as the primary source of pressure pulsations, whose characteristics are dominated by rotor–stator interaction mechanisms, and such disturbances decay rapidly in the downstream direction. Under turbine-braking and reverse-pump conditions, vortex rings, backflow, and asymmetric vortex structures generated within the spiral casing collectively contribute to the severe deterioration of the internal flow field quality. Full article

Problematic smartphone use in adolescence has been linked cross-sectionally to poorer academic and emotional functioning, but the longitudinal mechanisms remain unclear. Using three waves of the Panel Study on Korean Children (W14–W16; ages 14–16), this study tested whether problematic smartphone use at age 14 predicts four developmental outcomes at age 16—school adjustment, self-regulated learning, ego resilience, and subjective happiness—through four age-15 mediators: gaming, video-watching, self-study hours, and academic stress. Hierarchical regressions with autoregressive controls, bootstrap a-paths, and 16 indirect effects tested with 20,000-draw Monte Carlo confidence intervals were estimated. Problematic smartphone use predicted three outcomes but not subjective happiness, for which the association was indirect only. Seven indirect effects were significant, and six survived Benjamini–Hochberg false discovery rate correction. The findings indicated two pathways: a time-displacement pathway (gaming and reduced self-study) specific to self-regulated learning and an academic-stress pathway linked to school adjustment, ego resilience, and happiness. Crucially, in baseline-controlled sensitivity analyses, the time-use pathways remained significant, whereas the stress pathway was fully attenuated, indicating a concurrent rather than a prospective association. Results were robust across path-model SEM, full-information maximum likelihood, and inverse-probability weighting, supporting a dual-pathway account of adolescent digital development. Full article

Vertical cracks in concrete present a major challenge for many conventional nondestructive testing methods (NDT) and structural health monitoring (SHM) methods. Elastic wave-based approaches offer strong interaction with crack faces and depth sensitivity; however, their effectiveness is often limited by the lack of repeatable and tunable excitation sources. Repeatability is critical because scattered and attenuated signals require stacking to achieve adequate signal-to-noise ratios, while tunability is essential because key crack attributes are frequency-dependent and must be probed at appropriate wavelengths. In this study, we develop an active sensing system utilizing a linear impact actuator as a repeatable and tunable mechanical source for elastic-based NDT and apply it to a 0.24 m thick concrete slab containing three surface-breaking vertical cracks with depths of 6, 12, and 18 cm, respectively. The actuator is tuned by adjusting impact conditions to generate $A_0$-dominated Lamb wave responses. For each crack, two linear arrays are deployed, one parallel and one perpendicular to the crack trace, to investigate directional anisotropy. Phase-velocity anisotropy is quantified using the $A_0$ Lamb wave dispersion curves, while the effective quality factor is used as a complementary indicator of direction-dependent attenuation. Our results show that phase velocities are consistently higher for crack-parallel propagation than for crack-perpendicular propagation, and that the degree of anisotropy increases with crack depth. The quality factor decreases with increasing crack depth and exhibits anisotropic behavior, with systematically lower values for crack-perpendicular measurements compared to crack-parallel measurements. Overall, the results demonstrate that controllable and repeatable impact excitation establishes a reliable framework for elastic-wave-based characterization of idealized vertical cracks in concrete. Full article

Against the backdrop of population aging, the well-being of older adults with disabilities in daily life and its underlying mechanisms has increasingly become an important research topic. Using data from the 2020 wave of the China Health and Retirement Longitudinal Study (CHARLS), this study focuses on 509 individuals aged 60 and above with disabilities. It incorporates informal social support, depression risk, and life satisfaction into a unified analytical framework, and employs ordered Logit models, binary Logit models, and the KHB decomposition method to examine their interrelationships and underlying mechanisms. The results show that: (1) informal social support is positively associated with the life satisfaction of older adults with disabilities; (2) informal social support is negatively associated with depression risk; and (3) depression risk is negatively associated with life satisfaction and plays a significant mediating role in the relationship between informal social support and life satisfaction, accounting for 23.25% of the total effect. From a daily life perspective, this study reveals that the well-being of older adults with disabilities is not solely derived from institutional resource provision, but is generated and sustained through ongoing social interactions and relational networks. The study therefore deepens our understanding of the everyday and relational dimensions of subjective well-being in later life. Full article