Search Results (1,342)

The aim of this paper is to present the results of an experimental and numerical investigation into the degradation of reinforced concrete (RC) specimens subjected to an accelerated corrosion process using impressed current in the presence of chloride ions. The corrosion of the rebars was carried out using three current densities (50, 100, and 200 µA/cm²) and various exposure times. The experimental results characterised the internal degradation of the RC specimens through measurement of the corrosion product thicknesses at the steel–concrete interface; the widths, lengths and orientations of internal concrete cracks; and the external concrete crack widths. In addition, numerical modelling of the corroded RC specimens was conducted to describe the crack patterns. The comparison between the experimental and numerical results demonstrated a high degree of correlation, providing insights into the degradation process of RC specimens due to corrosion. Full article

A numerical method is proposed for evaluating the axial stress–strain relationship of FRP-confined concrete. In this method, empirical formulae for the compressive strength and strain at peak stress of confined concrete are obtained by fitting experimental data collected from the literature. It is then assumed that when FRP-confined concrete and actively confined concrete are subjected to the same lateral strain and confining pressure at a specific loading stage, their axial stress–strain relationships are identical at that stage. Based on this assumption, a numerical method for the axial stress–strain relationship of FRP-confined concrete is developed by combining the stress–strain model of actively confined concrete with the axial–lateral strain correlation. Finally, the validity of this numerical method is verified with experimental data with various geometric and material parameters, demonstrating a reasonable agreement between predicted stress–strain curves and measured ones. A parametric analysis is conducted to reveal that the stress–strain curve is independent of the specimen length for strong FRP confinement with small failure strains, while the specimen length exhibits a significant effect on the softening branch for weak FRP confinement. Therefore, for weakly FRP-confined concrete, it is recommended to consider the specimen length effect in evaluating the axial stress–strain relationship. Full article

The superb dynamic performance of steel-plate composite (SC) structures under unexpected impact loading depends on the good design of the connection between the SC wall and foundation. This study investigated the flexural behavior and dynamic responses of SC wall-to-foundation connections subjected to low-velocity impact. Impact tests were performed on three SC connection specimens to evaluate failure mode, impact force, deflection, and strain responses. The effects of concrete strength grade and impact energy were analyzed in detail. All specimens exhibited flexural failure, with three distinct stages observed during impact. The experimental results demonstrated that compared to the specimen with C30 concrete, the specimen with C50 concrete significantly reduced wall damage, decreased deflections, and enhanced deflection recovery ability. It can be concluded that increasing the concrete strength grade effectively improves the impact resistance of SC wall-to-foundation connections. In addition, peak impact force, global deflection response, residual strains, and interface crack length were highly sensitive to changes in impact energy, whereas deflection recovery exhibited lower sensitivity. Furthermore, a finite element model was developed and validated against experimental results. Parametric studies explored the influence of key parameters with expanded ranges on the impact responses of SC wall-to-foundation connections. Full article

Human exploitation has been a major driver of marine turtle population declines, particularly affecting naturally scarce species such as the pantropical hawksbill turtle. Although hawksbill sea turtles have been documented in the Gulf of California since the early 20th century, data on their historical demography during periods of high exploitation in this region are nonexistent. We investigated the size structure of hawksbill turtles from the Western Central Gulf of California by examining a unique sample of decorative taxidermies, corresponding to 31 specimens captured during fishing operations near Santa Rosalía, Baja California Sur, Mexico, between 1980 and 1990. An analysis of the curved carapace measures revealed a length range (nuchal notch to posterior of supracaudals) of 29.5–59.5 cm (mean = 38.75 ± 6.67 cm) and a width range of 25.0–51.5 cm (mean = 33.63 ± 5.66 cm), with 87% of specimens having lengths between 30 and 45 cm. Based on the carapace length measurements, we estimated the ages to be between 7 and 20 years, indicating that the population included juveniles. Our findings provide baseline data for an understudied period and region, suggesting that this area previously served as an important juvenile habitat. These results contribute essential historical demographic information for conservation planning. Full article

Temperature affects the morphology, physiology, and distribution of marine macroalgae, as supported by studies that used long-term data from herbaria. In the present study, sea surface temperature (SST), latitudinal distribution, and La Niña or El Niño years were correlated to the morphology of two macroalgal species of the Mexican Pacific: Ceratodictyon tenue and C. variabile. Twenty-four morphological characteristics were evaluated, and 95 samples from 1965 to 2013 in the Escuela Nacional de Ciencias Biológicas herbarium were reviewed. In 2017, 2023, and 2024, 12 specimens were sampled at three locations. Low positive correlations were found between thallus diameter and SST for C. tenue, while low positive correlations were detected for thallus length and medullary cell diameter vs. SST and medullary cell length vs. year for C. variabile. Significant relationships were found between the thallus length and cortical cell diameter of C. variabile with latitude and SST. It is concluded that SST contributes to changes in morphology, but is not the only factor that affects them. For the first time in a tropical area, the present study explores whether there is a relationship between SST, latitudinal distribution, and El Niño and La Niña years and the morphology of a genus of red algae. Full article

The arboreal rodent Oecomys catherinae, which has a wide geographic distribution across Brazilian biomes, provides a model for investigating environmental influences on morphological variation. We assessed craniodental differences between the Atlantic Forest and Cerrado biomes, as well as along latitudinal gradients, using 45 specimens from 18 localities. Linear morphometric analyses (21 measurements) revealed no significant sexual dimorphism, allowing for pooled analyses. Principal Component Discriminant Analysis (DAPC) confirmed significant morphological divergence between biomes (72% accuracy, p < 0.01). We identified bony palate length (BPL) as the most discriminating variable, with higher values in the Atlantic Forest, suggesting a possible dietary adaptation in response to ecological pressures. Latitudinal effects were modest (adjusted R² = 0.05) although significant (F_1,43 = 3.63; p = 0.03), with southern populations exhibiting larger cranial dimensions than northern ones. We conclude that biome type and latitude played important roles in shaping cranial morphology in O. catherinae populations. Full article

The accordion honeycomb has unique deformation characteristics in cellular materials. This study develops a three-dimensional equivalent Cauchy continuum model (3D-ECM) based on the variational asymptotic method (VAM) to efficiently predict the mechanical response of the accordion honeycomb. The accuracy of the 3D-ECM is validated via quasi-static compression experiments on 3D-printed specimens and detailed 3D finite element simulations (3D-FEM), showing a strong correlation between simulation and experimental data. Parametric analyses reveal that the re-entrant angle, ligament-to-strut length ratio, and thickness ratios significantly affect the equivalent elastic moduli, providing insights into geometric optimization strategies for targeted mechanical performance. Comparative experiments among honeycomb structures with positive, negative, and zero Poisson’s ratios show that the accordion honeycomb achieves superior dimensional stability and tunable stiffness but exhibits lower energy-absorption efficiency due to discontinuous buckling and recovery processes. Further comparison among different ZPR honeycombs confirms that the accordion design offers the highest equivalent modulus in the re-entrant direction. The findings underscore the accordion honeycomb’s promise in scenarios demanding structural reliability, tunable stiffness, and moderate energy absorption. Full article

Background: Sexual dimorphism in Asian elephants (Elephas maximus) is evident in external features, but skeletal differences remain underexplored. This study aimed to examine the skull, scapula, and pelvis using traditional morphometric methods to assess sex-related variation. Methods: Eleven skeletal specimens were analyzed, including nine skulls, eleven pelves, and eighteen scapulae. Linear measurements were obtained using measuring tape and calipers. Statistical analyses included Mann–Whitney U tests, Pearson’s correlation, and logistic regression for sex prediction. Results: No significant differences were found in skull measurements between sexes. However, the pelvis and scapula exhibited notable variation. Significant pelvic parameters included pelvic girdle length (p = 0.024), symphysis length (p = 0.012), and pubis shaft perimeter (p = 0.048). Scapular differences were observed in diagonal breadth, mediolateral width, and spine length. Logistic regression using pelvic measurements yielded 100% accuracy for female classification and 66.67% for males, with an overall prediction accuracy of 90.91%. Conclusions: The pelvis demonstrated the highest reliability for sex determination. These findings enhance the anatomical understanding of Asian elephants and support applications in conservation, forensic science, and population studies. Future research with larger sample sizes and advanced imaging may improve the precision of morphometric sex prediction models. Full article

North Africa has a poorly and unevenly known hoverfly fauna. Xanthogramma Schiner, 1861 (Syrphinae, Syrphini) is represented in this territory by some scattered records of four species, Xanthogramma dives (Rondani, 1857), Xanthogramma evanescens Becker & Stein, 1913 (endemic to North Africa), Xanthogramma marginale (Loew, 1854), and Xanthogramma pedissequum (Harris, 1776). After examination of old Xanthogramma material collected in Tanger, Morocco, from the ‘Museo Nacional de Ciencias Naturales, Madrid, Spain (MNCN)’, specimens with distinctive morphology were spotted and found to be different from a syntype of X. evanescens collected in the same locality. Consequently, we revised all the available material of Xanthogramma from North Africa, characterised a new species, proposed a lectotype for X. evanescens, and provided an identification key to the North African species of this genus. The new species is also found in Tunisia and differs from X. evanescens in facial width, colour of the thoracic pleura, length of mesonotum hairs, wing pollinosity, and shape of the yellow maculae on tergum 2. Full article

The tensile strength of the umbilical cord (UC) is influenced by its composition—including collagen, elastin, and hyaluronan—contributing to its unique biomechanical properties. This experimental in vitro study aimed to evaluate the UC’s mechanical behavior under varying strain rates and to characterize its viscoelastic response. Twenty-nine UC specimens, each 40 mm in length, were subjected to uniaxial tensile testing and randomly assigned to three traction speed groups: Group A (n = 10) at 8 mm/min, Group B (n = 7) at 12 mm/min, and Group C (n = 12) at 16 mm/min. Four different parameters were analyzed: the ultimate tensile strength and its corresponding elongation, the elastic modulus defined as the slope of the linear initial portion of the stress–strain plot, and the elongation at the end of the test (at break). While elongation and elongation at break did not differ significantly between groups (one-way ANOVA), Group C showed a significantly higher ultimate tensile strength (p = 0.047). A linear relationship was observed between test speed and stiffness (elastic modulus), with the following regression equation: y = 0.3078e^4.425x. These findings confirm that the UC exhibits nonlinear viscoelastic properties and strain-rate-dependent stiffening, resembling non-Newtonian behavior. This novel insight may have clinical relevance during operative deliveries, where traction speed is often overlooked but may play a role in preserving cord integrity and improving neonatal outcomes. Full article

In this study the objective was to morphologically characterize fruits, seeds and seedlings of Cereus fernambucensis Lem., as well as evaluate the seed germination and phenological dynamics of these columnar cacti, native to Brazil, which occur in restinga ecosystems. Biometric and morphological determinations were performed using 100 fruits, describing seed morphology in external and internal aspects and considering five stages of development for the characterization of seedlings. In the study of seed germination, two light conditions (12 h photoperiod and complete darkness) were tested under 25 °C, in a completely randomized design with four replicates of 50 seeds each. In the estimation of reproductive phenology, information was collected from herbarium specimens on the SpeciesLink online platform, and the exsiccatae were analyzed for the notes on their labels to evaluate reproductive aspects. Fruits showed an average mass of 21.11 g, length of 44.76 mm, diameter of 28.77 mm and about 336 seeds per fruit. Seeds behave as positive photoblastic, with a high percentage of germination under controlled conditions (94%). Germination is epigeal and phanerocotylar, with slow growth and, at 30 days after sowing, the seedling measures approximately 2 cm, which makes it possible to visualize the appearance of the epicotyl and the first spines. The species blooms and bears fruit throughout the year, with peaks of flowering and fruiting in January and March, respectively. The various characteristics make C. fernambucensis a key species for maintaining the biodiversity of restingas. Full article

Fused Filament Fabrication (FFF) enables the manufacturing of complex polymer components. However, surface finish and dimensional accuracy remain key limitations for their integration into functional assemblies. This study explores the potential of conventional turning as a post-processing strategy to improve the geometric and surface quality of PLA reinforced with carbon fiber (CF) parts produced by FFF. Machinability was evaluated through the analysis of cutting forces, thermal behavior, energy consumption, and surface integrity under varying cutting speeds, feed rates, and specimen slenderness. The results indicate that feed is the most influential parameter across all performance metrics, with lower values leading to improved dimensional accuracy and surface finish, achieving the most significant reductions of 63% in surface roughness (Sa) and 62% in cylindricity deviation. Nevertheless, the surface roughness is higher than that of metals, and deviations in geometry along the length of the specimen have been observed. A critical shear stress of 0.237 MPa has been identified as the limit for interlayer failure, defining the boundary conditions for viable cutting operation. The incorporation of CNC turning as a post-processing step reduced the total fabrication time by approximately 83% compared with high-resolution FFF, while maintaining dimensional accuracy and enhancing surface quality. These findings support the use of machining operations as a viable and efficient post-processing method for improving the functionality of polymer-based components produced by additive manufacturing. Full article

Perca schrenkii populations are experiencing significant declines, yet comprehensive morphological studies are still lacking. Understanding the relationship between morphological traits and body weight is crucial for conservation and breeding programs. We analyzed 13 morphological traits in 100 P. schrenkii specimens from Hamsigou Reservoir using correlation analysis, path analysis, and principal component analysis (PCA). Body weight exhibited the highest variability (CV = 39.76%). Strong correlations were observed between body weight and body length (R = 0.942), total length, and body width. A four-variable regression model explained 94.1% of body weight variation, with body length showing the strongest direct effect (path coefficient = 0.623). The first three principal components accounted for 76.687% of the total variance. Our findings demonstrate that BL, BW, BD, and ES can effectively predict body weight, providing valuable insights for the conservation and selective breeding of P. schrenkii. Full article

The Atlantic blue crab (Callinectes sapidus) has rapidly expanded across the Mediterranean, raising concerns over its ecological and economic impacts. This study examines the morphometric characteristics and environmental influences on C. sapidus populations in the Palud-Palù swamp (western Istrian coast) from 2022 to 2024. A total of 203 specimens were analyzed for carapace width, length, depth, and body mass, alongside monthly measurements of temperature, salinity, oxygen saturation, and pH. Statistical analyses (t-tests, ANOVA, PCA, and RDA) revealed pronounced sexual dimorphism, with males consistently larger than females. Interannual differences in size distribution showed larger individuals in 2022, followed by a decline in 2023 and 2024, likely due to environmental stressors (e.g., salinity, temperature, hypoxia) and increased anthropogenic pressures (e.g., trapping and illegal harvesting). RDA identified temperature, oxygen saturation, and pH as key abiotic drivers of morphometric variation. These findings suggest that while C. sapidus demonstrates physiological plasticity, enabling its persistence in estuarine environments, its growth and invasive potential may be constrained under extreme or suboptimal local conditions. This study highlights the importance of long-term monitoring and integrated management to mitigate ecological disruption in sensitive coastal ecosystems. Full article

Sexual dimorphism is prevalent among animals, influencing both functional morphological traits and behavioral performances. In this study, we investigated the sexual differences in the morphological parameters of Kaloula borealis (Anura, Microhylidae) during the breeding season using 48 specimens. Our results reveal that among the 16 external morphological traits, females had significantly larger snout-vent length and eye diameter than males. The former presumably contributes to enhancing fertility, while the latter is associated with larger body size. Males exhibited significantly greater head width and thigh width than females, which may be related to accessing a wider range of food sources and enhancing their locomotor ability, respectively. Among the 32 appendicular muscles, 10 displayed significant sexual dimorphism in dry mass, suggesting divergent reproductive strategies between the sexes. Among the eight internal organs analyzed, males possessed significantly heavier hearts and lungs than females, which is likely an adaptation to higher metabolic demands and calling behavior. Collectively, our findings demonstrate that sex-specific differences in external morphology, muscle mass, and internal organ mass reflect distinct ecological and reproductive adaptations between males and females and contribute to the phenotypic diversities in Anura. Full article