Search Results (405)

Fe-Al intermetallic coatings were fabricated on 0Cr21Al6Nb stainless steel by pack cementation to systematically investigate the effects of temperature (650–800 °C) and holding time (2–16 h) on the coating microstructure, phase constitution, and hardness. The coatings primarily consisted of Fe₂Al₅, with a minor amount of FeAl₃ confined to the outermost surface. The coating/substrate interface exhibited a characteristic serrated or tongue-like morphology, which became increasingly pronounced with increasing temperature and holding time, indicating enhanced interdiffusion across the interface. Both increasing temperature and prolonging holding time markedly promoted coating growth and increased the coating thickness, while simultaneously facilitating the enrichment of FeAl₃ in the near-surface region. Despite these microstructural variations, the coating hardness remained relatively stable at approximately 960 HV, which was substantially higher than that of the substrate; meanwhile, the substrate exhibited a slight reduction in hardness after aluminizing. Thermodynamic analysis revealed that Fe₂Al₅ was preferentially formed owing to its relatively lower Gibbs free energy, and its formation remained thermodynamically favored during subsequent coating growth, whereas FeAl₃ was restricted to the coating surface. Kinetic analysis demonstrated that coating growth followed a parabolic law, indicating a diffusion-controlled growth mechanism, with an apparent activation energy of 107.5 kJ·mol⁻¹ for Al diffusion. Furthermore, temperature exerted a more pronounced influence on coating growth than holding time, highlighting temperature as the dominant kinetic parameter governing the formation and thickening of the Fe-Al intermetallic coating. Full article

Pitting distress introduces discontinuous surface texture, thereby modifying the friction–adhesion coupling at the rubber–asphalt interface. This study systematically investigates the interfacial friction response of SBS-modified asphalt pavements with three pitting distribution patterns (sparse, medium, and dense) under varying sliding rates, temperatures, and cyclic loading using a custom-developed friction testing apparatus. The results reveal that adhesion-dominated friction is strongly dependent on both texture distribution and operating conditions. With increasing temperature, the dense pattern exhibits the most pronounced adhesion enhancement, with an average friction increase of 55.0%. The sparse pattern shows a continuous decreasing trend in the low-to-medium speed range, but exhibits a strengthening rebound at high speeds, demonstrating the most complex rate sensitivity. Under cyclic loading, among the three pitting patterns tested, the dense pattern exhibits the best friction retention, with an average friction reduction of only 6.2% after 30 cycles, compared to 9.5% for the sparse pattern and 10.8% for the medium pattern. Three-dimensional topography indicates that the medium pattern exhibits a continuous and relatively uniform wavy roughness, while the dense pattern transforms into a high-frequency serrated morphology. However, the wear in both patterns is dominated by homogenized micro-grooves, without the formation of local deep pits or sharp undulations, which favors the maintenance of stable skid resistance under the laboratory cyclic loading conditions tested in this study. Furthermore, a unified regression model with distribution dummy variables and interaction terms (R² = 0.826; cross-validated Q² = 0.646) quantifies the synergistic effect of pitting density and temperature, with the temperature sensitivity increasing six-fold from the sparse to the dense pattern (0.011 to 0.071 N/°C). Full article

Despite the rapid proliferation of unmanned aerial vehicles (UAVs) across industrial, agricultural, and scientific domains, their deployment remains constrained by limited endurance, aerodynamic inefficiency, and acoustic emissions, all mediated by a shared onboard energy budget. Existing biomimetic UAV reviews have generally treated aerodynamics, structures, sensing, control, and energy systems as parallel topics rather than as interacting components of a unified aerial architecture. Drawing primarily on literature published between 2015 and June 2026 and identified through searches of Web of Science, Scopus, and Google Scholar, this review addresses this gap by examining bio-inspired technologies across six principal domains: aeroacoustic and passive flow control, aerodynamic efficiency, multifunctional structural composites, neuromorphic sensing and control, ionic energy storage, and energy harvesting. Its principal contribution is a cross-domain synergy analysis identifying five performance couplings and one structural enabling architecture through which these domains interact physically and functionally. Representative examples include serration-based propeller geometries that can simultaneously reduce noise and power demand; morphing wing surfaces that serve as both aerodynamic structures and triboelectric harvesting substrates; and neuromorphic spiking neural networks that have been reported, in specific event-vision inference benchmarks, to reduce inference energy by three to four orders of magnitude relative to embedded graphics processing unit (GPU)-based implementations. Mechanical harvesting outputs nonetheless remain orders of magnitude below propulsion requirements and are thus positioned as supplementary. Four systemic barriers (unquantified mass–energy balance, undocumented durability, aeroelastic co-design gaps, and heterogeneous metrics) are evaluated, and the resulting synthesis indicates that advancing bio-inspired UAVs requires a transition from structural imitation to functional, system-level biomimetics. Full article

Background/Objectives: Chemerin is an adipokine implicated in metabolic regulation, inflammation and cancer biology, but its value as a circulating biomarker in colorectal neoplasia remains uncertain. We investigated serum chemerin concentrations in patients with colorectal cancer (CRC), patients with colorectal polyps and colonoscopy-negative controls, and explored chemerin immunoreactivity in available polyp and tumour tissue. Methods: This exploratory observational case–control study included 41 patients with CRC, 20 patients with colorectal polyps and 29 colonoscopy-negative controls. Serum chemerin was measured by ELISA. Tissue specimens underwent routine histopathology and qualitative immunohistochemical staining for chemerin. Between-group comparisons were performed using non-parametric tests; subgroup analyses were exploratory and unadjusted. Results: Serum chemerin concentrations did not differ significantly between CRC and controls (median 144.0 vs. 135.7 ng/mL; p = 0.41), CRC and polyp groups (144.0 vs. 97.4 ng/mL; p = 0.24), or polyp and control groups (97.4 vs. 135.7 ng/mL; p = 0.94). Chemerin immunostaining was absent in CRC tissue (0/41) and conventional adenomatous polyps (0/15), whereas all available hyperplastic/serrated lesions showed epithelial cytoplasmic and/or stromal immunoreactivity (5/5); in lesions containing dysplasia, dysplastic glands showed no detectable staining. In controls, higher chemerin concentrations were associated with hyperglycaemia, hypertension, body weight and bilirubin, but these exploratory findings were not adjusted for multiplicity or metabolic confounding. Conclusions: In this exploratory cohort, serum chemerin did not discriminate CRC or colorectal adenoma from colonoscopy-negative controls. Together with the absence of staining in CRC and conventional adenomas, the findings argue against chemerin as a standalone circulating or commonly expressed tissue biomarker for these lesions under the assay conditions used. Immunoreactivity in the non-dysplastic epithelial and/or stromal compartments of hyperplastic/serrated lesions remains preliminary and requires prospective confirmation with standardised pre-analytics, quantitative pathology scoring and adjustment for metabolic confounders. Full article

Temperature- and strain-rate-dependent serrated flow, localized plastic instability, and qualitative microcrack evolution in Mn13 Hadfield steel were investigated using stress–strain analysis and in situ tensile observation. Solution treatment at 1050 °C for 1–1.5 h followed by water quenching yielded homogeneous single-phase austenite. Type A and Type B serrations were dominant at room temperature at 1 × 10⁻³ s⁻¹ and at 100 °C at 1 × 10⁻² s⁻¹, whereas the room-temperature specimen tested at 1 × 10⁻² s⁻¹ showed delayed serration onset and pronounced Type B stress drops only at high strains. Type C serrations occurred mainly near fracture at 100 °C at 1 × 10⁻³ s⁻¹, 200 °C at 1 × 10⁻² s⁻¹ and 200 °C at 5 × 10⁻² s⁻¹. In situ observations further reveal that different serration types correspond to distinct localized deformation modes. During Type A serrations, the tracked feature exhibited unidirectional stepwise migration involving forward motion, arrest, and renewed advance. Type B serrations were associated with discontinuous pulse-like migration characterized by rapid forward motion, brief arrest, local backward motion, and renewed advance. No regular trajectory was observed during Type C stress drops; only local brightness changes and slight positional shifts occurred. These observations link macroscopic serrations to localized deformation in Mn13 steel and provide qualitative in situ evidence for grain-boundary microcrack initiation and evolution during deformation. Full article

Background: Colorectal neoplasia in adults younger than 50 years has attracted increasing clinical attention because of the rising incidence of early-onset colorectal cancer. However, the clinicopathological characteristics of colorectal lesions detected in younger adults remain incompletely described. This study aimed to characterize the clinical, anatomical, and histopathological features of colorectal neoplasia in adults younger than 50 years undergoing colonoscopy. Methods: This retrospective single-center study included adults aged 18–49 years who underwent complete colonoscopy between January 2018 and December 2023. After exclusion of individuals with normal colonoscopy findings, 152 patients with at least one colorectal lesion were included. Lesions were classified as benign, advanced, or malignant according to established histopathological criteria. Demographic, endoscopic, and pathological characteristics were analyzed and compared across lesion categories. Results: Among 152 patients, 83 (54.6%) had benign lesions, 64 (42.1%) had advanced neoplasia, and 5 (3.3%) had malignant lesions. Advanced lesions were observed predominantly in individuals aged 40–49 years. Most lesions were detected in symptomatic patients undergoing clinically indicated colonoscopy. Histopathological evaluation demonstrated a higher frequency of villous/tubulovillous adenomas, sessile serrated lesions, and high-grade dysplasia among advanced lesions. Larger lesion size was strongly associated with advanced pathological features (p < 0.001). In multivariable analysis, patients aged 30–39 years had significantly lower odds of advanced or malignant neoplasia than those aged 40–49 years, whereas no independent associations were observed for sex, smoking status, alcohol use, family history of colorectal cancer, or lesion location. Conclusions: In this selected cohort of adults younger than 50 years with detected colorectal lesions undergoing clinically indicated colonoscopy, advanced neoplasia represented a substantial proportion of cases. These findings should not be extrapolated to the general population of adults younger than 50 years or to screening cohorts. Full article

Two new millipede species of the genus Coxobolellus Pimvichai, Enghoff, Panha & Backeljau, 2020 (Diplopoda, Spirobolida: Pseudospirobolellidae) are described from southern Thailand based on morphological characters and mtDNA sequences (COI and 16S rRNA). The new species are: Coxobolellus kaengkrachanensis sp. nov. from Phetchaburi Province and Coxobolellus planiprocessus sp. nov. from Prachuap Khiri Khan Province. Both species are distinguished from all congeners by the posterior gonopod telopodite terminating apically in a coarsely serrate lamella. They differ from each other in the shape of the apical process of the posterior gonopod telopodite, being either a pointed spine in Coxobolellus kaengkrachanensis sp. nov. or a broad, flattened process in Coxobolellus planiprocessus sp. nov. The mean interspecific sequence divergence between the two new species is 0.08 for COI and 0.09 for 16S rRNA, while their mean interspecific sequence divergences with respect to other Coxobolellus species are 0.12 for COI and 0.15 for 16S rRNA. Phylogenetic analyses of COI and 16S rRNA firmly place the two new species as sister taxa within the Coxobolellus clade and reassign another pseudospirobolellid species, viz. Benoitolus siamensis (Attems, 1936), to the genus Pseudospirobolellus. Hence this latter species should be referred to as Pseudospirobolellus siamensis comb. nov. This conclusion is supported by a re-interpretation of the original description of the species’ gonopod morphology. In contrast, the phylogenetic analysis of COI sequences places Benoitolus birgitae (Hoffman, 1981) with strong support in the genus Litostrophus Chamberlin, 1921, within the family Pachybolidae, thus raising the question as to whether the genus Benoitolus can be maintained in the family Pseudospirobolellidae. Full article

Accurate mapping of thermokarst lakes in the Qinghai–Tibet Engineering Corridor is important for understanding permafrost degradation and assessing environmental risks to major infrastructure. However, thermokarst lake extraction from medium-resolution satellite imagery remains challenging because these lakes are often small, fragmented, seasonally variable, and spectrally confused with wetlands, shadows, and other surface water bodies. In this study, Sentinel-2 imagery from the 2020 thaw season was used to map thermokarst lakes in the Qinghai–Tibet Engineering Corridor. A 16-feature dataset was constructed by integrating spectral bands, water indices, texture features, and topographic variables, and a convolutional neural network (CNN) was compared with five conventional machine learning classifiers. In the pixel-based validation, the CNN slightly outperformed the other evaluated models, achieving the overall accuracy of 98.04% and an F1-score of 97.18%. Independent polygon-based validation using the Jilin-1 visual interpretation reference showed that the final CNN-derived inventory achieved an IoU of 0.79, with omission and commission ratios of 0.15 and 0.09, respectively. The CNN more effectively suppressed salt-and-pepper noise, reduced fragmented and serrated lake boundaries, and improved the spatial continuity of mapped water bodies compared with traditional machine learning classifiers. SHAP-based attribution suggested that CNN predictions were more strongly associated with water indices and texture features, whereas Random Forest predictions were mainly associated with near-infrared and shortwave-infrared bands. Thermokarst lakes showed higher lake area proportions and densities in areas with relatively high ground ice content, gentle slopes, thicker active layers, warmer permafrost, and unstable permafrost conditions. These results demonstrate the potential of Sentinel-2 imagery and convolutional models for regional thermokarst lake mapping and permafrost degradation monitoring. Full article

Background/Objectives: Early-onset colorectal cancer (EO-CRC) incidence continues to rise globally, yet age-stratified risk data for adults under 45 remain limited. Methods: This retrospective, single-center, colonoscopy-based cohort study included 3959 examinees aged 18–44 at Peking University International Hospital (2023–2024) and used Joinpoint regression to identify age inflection points for polyp detection rates. Case–control analysis with Least Absolute Shrinkage and Selection Operator (LASSO)-penalized logistic regression assessed metabolic risk factors for adenoma and serrated polyps in the 40–44 stratum. Results: Detection rates for polyps, adenomas, and serrated lesions all rose with age (p < 0.001). From the youngest (18–29) to the oldest (40–44) group, the polyp detection rate increased 2.6-fold, the adenoma detection rate (ADR) 4.3-fold, and the serrated lesion detection rate 2.0-fold. Joinpoint regression revealed an ADR inflection at age 33 (annual percentage change (APC): +0.51% → +1.27%), a high-risk adenoma (HRA) inflection at age 39 (APC: +0.14% → +0.77%), and an advanced-neoplasia inflection also at age 39 (APC: +0.20% → +0.81%). Across age strata, adenoma and advanced-neoplasia detection rates were comparable between asymptomatic screening and symptomatic examinees from age 35 onward (40–44 ADR 20.5% vs. 21.6%), whereas symptomatic examinees had higher rates in the youngest strata. In exploratory cross-sectional analyses within the 40–44 group, total cholesterol (odds ratio, OR = 1.47) and body mass index (BMI) (OR = 1.05) showed associations with adenoma, without establishing causality, with BMI elevation conferring risk only in women (p for interaction = 0.018). Conclusions: Adenoma risk accelerates at 33 and high-risk lesions escalate at 39, providing age-stratified risk benchmarks for adults under 45 in a predominantly symptomatic Chinese cohort. These inflection points warrant prospective validation in asymptomatic screening populations. Full article

Small unmanned aerial vehicles (UAVs) are widely used in civil and military fields, and their noise problem has always been the industry’s focus. Compared with a traditional propeller fan, a ducted fan offers higher aerodynamic efficiency, lower aerodynamic noise, and greater safety. It has become the key power component of small UAVs. However, due to the rigid restriction on tip clearance, the traditional integral ducted fan is prone to generating a tip leakage vortex, which produces high-intensity aerodynamic noise and significantly reduces propulsion efficiency. To address the above key problem restricting the quiet flight of small UAVs, this paper designs a segmented ducted fan (SDF). It preliminarily explores the influence of the segmented clearance on the fan’s flow field structure and acoustic radiation characteristics. Specifically, the k-ω SST (shear stress transport) turbulence model and the broadband noise source model were used to establish a computational fluid dynamics model, and the effects of fan speed (20,000–40,000 rpm) and duct spacing (0–20 mm) on its aeroacoustic characteristics were systematically studied. The results showed that the SDF’s acoustic power level maximum (APL_max) was significantly higher than that of the traditional integral structure, especially at high speed. At 40,000 rpm, increasing the duct spacing to 20 mm resulted in a sudden increase in APL_max to 194.5 dB, 61.3 dB higher than that of the integral type. Its essence was derived from the three-stage chain amplification mechanism: (1) strong tip leakage vortex induced by geometric clearance; (2) broadband noise caused by vortex impacting the duct wall; (3) resonant coupling of leakage vortex harmonic frequency and duct cavity standing wave. Based on this, a collaborative noise reduction path was proposed: compressing the spacing to ≤10 mm to suppress the intensity of leakage vortex, designing the periodicity of failure vortex combined with the serrated blade tip/inner wall rubber strip, and blocking the acoustic cavity resonance with non-uniform wall stiffness or 8–10 kHz Helmholtz resonator, providing a solution for the low-noise design of UAV propulsion system. Unfortunately, our study cannot currently resolve transient characteristics; only time-averaged velocity/pressure flow-field contours and total acoustic power distribution are obtained for qualitative analysis of macroscopic noise variation laws and flow-sound correlation. Full article

Plate–fin heat exchangers (PFHEs) are widely used in petrochemical, energy and electric power, aerospace, and other industries with large heat transfer requirements. The development of performance prediction and optimization methods for PFHEs has become increasingly important in the design and operation of such heat exchangers (HEs). This paper establishes a database of flow and heat transfer characteristics for four types of PFHEs with different structural parameters. Based on this database, the back-propagation artificial neural network (BP-ANN) model was optimized using the particle swarm optimization (PSO) algorithm to form the PSO-BP-ANN model for the performance prediction of these four types of PFHEs. This combination has been found to improve the prediction accuracy and generalization ability of the BP-ANN model. Additionally, the non-dominated sorting genetic algorithm II (NSGA-II) method was used to characterize the relationship between four structural parameters to be optimized (the length, height, spacing, and thickness of the HE fin) and the two objective functions (j and f) of the serrated PFHE in laminar flow. This enables the Pareto optimal solution to be obtained. The results show that, under laminar flow conditions (Re = 800), the serrated fin HE achieves the best heat transfer performance when the fin height, spacing, thickness, and length are 9.29, 1.22, 0.16, and 3.06, respectively. Full article

Background/Objectives: Colorectal serrated lesions are highly heterogeneous at the micromorphological level. Their morphology can range from seemingly harmless, as in the case of hyperplastic polyps with little to no neoplastic potential, to lesions that can undergo malignant transformation within a short period of time. The serrated morphology of these lesions is primarily a consequence of morphological changes resulting from the enlargement and budding of the adenoma, as well as the migration of its epithelium at the crypt level. This creates elevations that resemble saw teeth. In this study, the serrated morphology was highlighted immunohistochemically using the MUC2 marker. Results: MUC5AC immunohistochemical expression exhibited greater variability in positivity and intensity compared to MUC2 expression. Pancryptic MUC5AC positivity was present in 75% of TSA cases and in 75% of malignantly transformed serrated lesions. This correlates with advanced histologic lesions and dysplasia development within the serrated pathway of carcinogenesis. MUC5AC is a useful marker for detecting polyps undergoing malignant transformation but not for distinguishing between sessile serrated lesions and hyperplastic polyps. Analysis of Ki-67 proliferative activity in serrated lesions in this study showed that a shift in the proliferative zone along the entire crypt was statistically significant only in TSA (p < 0.01). p53 expression increases from low-grade to high-grade dysplasia and malignant transformation of serrated lesions. This study confirmed that p53 expression in the upper half of the crypt was present in 11% of sessile serrated lesions without dysplasia and in 18% with dysplasia. In malignantly transformed serrated lesions, pancryptic positivity was present in 25% of cases. Conclusions: A marker panel consisting of mucin glycoproteins, Ki-67, and p53 could be useful in assessing the risk level of malignant transformation in serrated lesions. Full article

The dynamic strain aging (DSA) behavior of an extruded Mg–3Gd–1Zn (wt.%) alloy was investigated under compressive deformation at intermediate temperatures (150–250 °C) and strain rates ranging from 5 × 10⁻⁵ to 10⁻³ s⁻¹. The as-extruded alloy exhibited equiaxed grains (~20 µm), with all alloying elements retained in solid solution and a weak basal texture. Serrated flow was observed under different temperature and strain-rate conditions. The critical strain, which denotes the onset of serrations, decreased with increasing temperature and increased with strain rate. Notably, the temperature dependence of the critical strain exhibited anomalous non-linear behavior, with a sharp increase at 250 °C, attributed to the formation of low-mobility Gd–Zn clusters/precipitates that depleted mobile solutes from the matrix. In situ synchrotron radiation diffraction revealed the activation of {10.2}⟨10.1⟩ tensile twinning as the dominant deformation mechanism, with periodic plateaus in twin intensity coinciding with macroscopic stress serrations. HAADF-STEM analysis confirmed Gd and/or Zn segregation at twin boundaries and dislocations, leading to the formation of nanoscale clusters during deformation. The overall mechanical response is rationalized by a temperature-dependent competition between solute diffusion and solute clustering at elevated temperatures. Full article

The abnormal effect of hot isostatic pressing (HIP) on the fatigue properties of DD6 single crystal superalloy was investigated. The results showed that HIP combined with standard heat treatment (SHT) reduced the fatigue life under 880 °C and 800 MPa. HIP treatment eliminated inner shrinkage porosity effectively; however, the amount of micropores increased in the subsequent SHT. Moreover, HIP treatment enlarged the size of γ′ precipitates gradually and altered the morphology of carbides greatly. Small MC carbides decomposed into M₂₃C₆ carbides, and a serrated structure formed on the surface of large-size MC carbides, which led to the positive and negative effects on fatigue properties, respectively, depending on the morphology and size of carbides. Recrystallized microstructures were observed after HIP treatment, accompanied by fine, continuous precipitates along recrystallized grain boundaries. This led to a sharp decline in the elevated-temperature fatigue properties of DD6 superalloy fabricated at a drawing velocity of 150 μm/s. The abnormal decrease in fatigue life of DD6 single crystal superalloy was attributed to micropore formation, coarsening of γ′ precipitates and recrystallization. Thus, it is essential to optimize the HIP treatments in the future development of single crystal superalloy blades. Full article

Background and Objectives: Sessile serrated lesions (SSLs) are increasingly recognized as relevant precursors in alternative pathways of colorectal carcinogenesis, yet their endoscopic recognition remains challenging. Materials and Methods: We conducted a systematic review of studies reporting endoscopic and patient-related features associated with SSLs. PubMed/MEDLINE was searched for studies published between 2003 and November 2025. Eleven studies including 13,453 participants were identified. Results: Frequently reported endoscopic hallmarks included proximal colon location, larger lesion size, flat or slightly elevated morphology, indistinct borders, mucous cap, cloud-like surface, and pit-pattern features consistent with Kudo/Fujii types III–IV. Considerable heterogeneity in definitions and analytical reporting was observed. Conclusions: Although several features may raise suspicion for SSLs, standardized evidence remains limited, supporting a cautious and comprehensive approach to polyp assessment. Full article