Search Results (4,515)

In order to conduct a comprehensive investigation into the effects of ground granulated blast furnace slag (GGBFS) on the dynamic mechanical properties and mesoscopic damage mechanisms of recycled aggregate concrete (RAC), a combined approach integrating material testing, microscopic characterization techniques, and theoretical analysis was adopted in this study. Two GGBFS replacement rates (0% and 35%) were considered. Uniaxial compression tests were performed to obtain data at different curing ages (T = 7 d, 28 d, 56 d, and 150 d) and strain rates ($\dot{\epsilon }$ = 10⁻⁵/s, 10⁻⁴/s, 10⁻³/s, and 10⁻²/s). The obtained data were complemented by nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) analyses to characterize the evolution of the microstructure and pore characteristics of the specimens. The findings demonstrated that prolonging the curing period continuously densified the microstructure of the specimens, resulting in a commensurate improvement in their initial macro-mechanical behavior. At curing ages exceeding 28 d, the secondary hydration reaction of GGBFS was found to generate additional C-S-H gel, which filled the internal microvoids within the specimens, reduced porosity, and further improved the initial macroscopic mechanical properties. Concurrently, the microstructural characteristics observed at different curing ages, in conjunction with the crack propagation and the fracture toughness effects associated with strain rate, further influenced the initiation, propagation patterns and paths of microcracks during uniaxial compression, as well as the adjustment of the effective stress framework. Furthermore, characteristic parameters describing the evolution of mesoscopic fracturing and yielding damage exhibited regular variations with curing age and strain rate. For specimens cured for 56 d, compared to those with a GGBFS replacement rate of 0%, specimens containing 35% GGBFS exhibited a 4.13% increase in peak stress and a 0.29% decrease in peak strain at $\dot{\epsilon }$ = 10⁻⁵/s. At a replacement rate of 35%, as the strain rate increased from $\dot{\epsilon }$ = 10⁻⁵/s to $\dot{\epsilon }$ = 10⁻²/s, the peak stress rose from −50.37 MPa to −60.74 MPa, whereas the peak strain dropped from −23.87 × 10⁻⁴ to −22.15 × 10⁻⁴. This study provides significant scientific evidence and a theoretical framework for the engineering application of GGBFS-modified RAC under varying strain rate conditions. Full article

Carbon fiber-reinforced polymer (CFRP) composites are widely used in the aerospace industry. The residual stresses generated during the curing process significantly affect their mechanical properties. In this study, a multi-field coupled simulation of curing and subsequent uniaxial tension is performed on CFRP laminates with different curing parameters. First, the curing process is simulated to obtain the residual stress distribution in the composite. Then, the residual stresses are introduced as initial stresses for the subsequent loading step. The influence of curing parameters on the mechanical properties of composite laminates under uniaxial tension is analyzed. The results show that the temperature of the first holding stage has a significant effect on the residual stresses. When the temperature is set to 383 K, 403 K, or 413 K, the curing residual compressive stress exceeds the critical value of −50.424 MPa, and the ultimate tensile strength of the laminates decreases by approximately 20.7%. However, the large residual compressive strain also delays the initiation of matrix tensile damage, postponing the initial failure displacement from 1.025 mm to about 1.111 mm. When the holding time of the second stage varies between 80 min and 160 min, the residual stress after curing and the tensile strength of the laminates remain almost unchanged. This study provides a basis for selecting curing parameters of composite materials and offers new insights into improving their mechanical properties. Full article

Candida albicans (C. albicans) is a commensal of the vaginal mucosa and the main etiological agent of acute and recurrent vulvovaginal candidiasis (VVC/RVVC). Disease severity is thought to depend on a dysregulated host inflammatory response to Candida, not necessarily associated with increased fungal burden and/or morphogenesis. The role of strain-specific differences leading to epithelial immune response or tolerance remains undefined. In this study, we compared the virulence profile of vaginal C. albicans isolates from women with acute VVC/RVVC (VVC/RVVC), asymptomatic colonizer (Colonizing), and VVC/RVVC associated with microbial co-infections (Co-infections). Isolates were evaluated for growth and biofilm formation under standard culture conditions and tested in an in vitro vaginal epithelial cell (VEC) infection model to assess fungal shedding, epithelial damage, and cytokine production. Corresponding vaginal samples were analyzed for C. albicans morphology, polymorphonuclear neutrophil presence, microbiota composition, cytokines levels, and anti-C. albicans IgA production. No significant differences in growth or biofilm formation were observed among isolates under culture conditions. However, VEC infection revealed strain-dependent differences: acute VVC/RVVC and Co-infections isolates induced greater fungal shedding, while VVC/RVVC isolates caused increased epithelial damage and showed a trend toward higher cytokine production. Vaginal samples from symptomatic groups displayed increased neutrophils, hyphal morphology, elevated IL-1α, IL-1β, and anti-Candida IgA, but not IL-1Ra, without differences in lactobacilli abundance or Community-State-Type (CST) distribution. These findings suggest that C. albicans pathogenicity in VVC depends on strain-specific interactions with VEC driving differential host responses. Full article

To reduce carbon emissions from cement-treated aggregate base layers and examine the nonlinear service behavior of semi-rigid materials, supersulfated cement (SSC) was used to replace ordinary Portland cement (OPC). A dynamic triaxial loading protocol was adopted to separate the effects of bulk stress and shear stress on the dynamic resilient modulus of supersulfated cement-treated aggregate (SSC-CTA). A fatigue damage equation was developed based on the strain energy balance during cracking, and Paris’ law damage parameters were introduced to compare the damage growth rates of SSC-CTA and ordinary Portland cement-treated aggregate (OPC-CTA). Finite element analysis and partial differential equations were further used to link the stress-dependent resilient modulus with structural fatigue life. The results show that SSC-CTA had a lower dynamic resilient modulus than OPC-CTA under the same stress state. The average resilient modulus of SSC-CTA was 978 MPa, which was 15.47% lower than that of OPC-CTA. For both materials, the modulus increased with bulk stress and decreased with octahedral shear stress, and the NCHRP 28A model accurately predicted this nonlinear behavior. Although SSC-CTA had a lower modulus, its indirect tensile strength reached 864.3 kPa, representing a 52.65% increase compared with OPC-CTA. The Paris’ law parameters further indicated that SSC reduced the damage growth rate during crack propagation. The finite element results showed that the predicted structural fatigue life of SSC-CTA increased by 4.49–35.90% under different load levels. Full article

Staggered-floor steel-reinforced concrete beam–column joints are extensively applied in turbine buildings of nuclear power plants to meet the requirements of spatial layout and pipeline arrangement. Such joints feature distinct geometric discontinuity and suffer additional torsion effects as well as asymmetric stress distribution when the middle column is lost, which greatly impairs the structural progressive collapse resistance. In this study, three 1/5-scale joint specimens, consisting of two staggered-floor steel-reinforced concrete joints and one reinforced concrete joint, were tested under vertical monotonic static loading. The failure pattern, deformation property, torsional performance, strain development and load-bearing mechanism were comprehensively analyzed. Finite element models considering the coupling effect of torsion, bending and shear were established and validated via ABAQUS. The test results show that the peak load-bearing capacities of the SRC-1, SRC-2, and RC specimens were 148.2 kN, 149.7 kN, and 69.3 kN, respectively. Compared with the RC specimen, the peak load-bearing capacity of the SRC specimens more than doubled, indicating that the embedded H-section steel can significantly improve the load-bearing capacity of staggered beam–column joints. However, when the staggered height distance was increased from 140 mm to 280 mm, the ultimate collapse displacement of the specimens decreased from 340 mm to 310 mm, indicating a reduction in deformation capacity. The finite element model reasonably reproduced the specimens’ primary load–displacement response and damage characteristics, with a peak load error of 8.93% for SRC-1. Finally, corresponding design recommendations are put forward for staggered-floor steel-reinforced concrete joints in nuclear power plant structures. Full article

Background/Objectives: Hydrochloric acid (HCl)/ethanol-induced gastric mucosal injury is closely associated with oxidative stress and inflammatory responses. Probiotics are promising therapeutic agents for gastrointestinal disorders. Therefore, this study evaluated the preventive effects of Cheonggukjang-derived Bacillus strains on HCl/ethanol-induced gastric mucosal injury in a rat model (n = 5 per group), with emphasis on inflammatory mechanisms. Methods: Eight-week-old male Sprague–Dawley rats were orally administered Bacillus amyloliquefaciens C393 1.0 × 10⁹ CFU (B393), Bacillus subtilis C439 1.0 × 10⁹ CFU (B439), or B. subtilis C512 1.0 × 10⁹ CFU (C512). Gastric injury was induced by oral administration of HCl/ethanol (150 mM HCl in 60% ethanol). Results: HCl/ethanol exposure significantly increased symptom scores, gastric mucosal lesion area, and histopathological damage. Pretreatment with B393 and B439 significantly attenuated these alterations. Moreover, HCl/ethanol administration increased gastric secretion volume and decreased gastric pH, both of which were significantly normalized by B393 and B439. Serum levels of pro-inflammatory cytokines, including tumor necrosis factor-α and interleukin-6, were significantly elevated following HCl/ethanol exposure but were markedly reduced by B393 and B439. Immunohistochemical analysis demonstrated that nuclear factor-kappa B activation in gastric tissues was significantly suppressed in these groups. Conclusions: These findings indicate that Cheonggukjang-derived Bacillus strains exert strain-specific gastroprotective effects possibly by suppressing NF-κB-mediated inflammatory signaling. Full article

Accurately predicting the mechanical response and failure of composite–metal hybrid bolted joints under thermo-mechanical coupled loads remains a critical challenge in aerospace engineering. This paper develops a temperature-dependent multi-scale progressive failure analysis model based on micromechanical failure theory. A hexagonal representative volume element (RVE) incorporating fibers, matrix and interphase is constructed, with a stress amplification factor enabling macro–meso stress–strain transformation. Dimensionless temperature corrections are applied to resin and interphase mechanical properties, and temperature-influenced mesoscopic failure criteria with corresponding stiffness degradation schemes are proposed. The nonlinear progressive damage simulation is implemented via the ABAQUS/UMAT subroutine. Static tensile tests on AC531/CCF800H composite-7075 aluminum alloy three-bolt double-shear joints are conducted at −70 °C, 20 °C and 120 °C. The results show excellent agreement between the simulations and experiments, with ultimate load errors < 5%. Low temperature increases load capacity by 3.91% via resin hardening and enhanced interfacial bonding, while high temperature reduces it by 9.07% due to resin softening. Failure modes shift from end-hole tensile fracture (−70 °C, 20 °C) to full-hole bearing failure (120 °C), governed by altered bolt load distribution and damage evolution paths. The proposed model provides reliable support for thermo-mechanical design and strength verification of aerospace composite structures. Full article

Multidrug-resistant Salmonella Paratyphi poses a severe threat to public health. As conventional antibiotics lose efficacy against emerging resistant strains, the need to develop alternative antimicrobial agents has become increasingly urgent. In this study, we isolated and characterized a novel lytic bacteriophage, designated SEP1, from poultry sewage using the S. Paratyphi C strain QH as the host and systematically evaluated its therapeutic potential in a murine infection model Genomic analysis confirmed that SEP1 belongs to the genus Felixounavirus, with an 85,703-bp genome devoid of lysogeny-associated or virulence genes. SEP1 exhibits robust environmental stability, maintaining infectivity at 10–50 °C and pH 4–9; it has a 30 min latent period and a burst size of 133 PFU per infected cell. In vivo, SEP1 treatment conferred 100% survival in infected mice, reduced organ bacterial loads, alleviated tissue damage, and normalized inflammatory cytokine profiles. Collectively, these results demonstrate that SEP1 is a promising candidate for phage therapy targeting S. Paratyphi C infections. Full article

White-nose syndrome (WNS), caused by the psychrophilic fungus Pseudogymnoascus destructans, poses a severe threat to wild bat populations. Caves serve as unique microecosystems. Exploring antagonistic microorganisms and their volatile antifungal compounds within these native environments has emerged as a promising ecological control strategy. In this study, we isolated four antagonistic bacterial strains from bat cave soil that completely inhibit P. destructans. Additionally, we identified benzaldehyde (BzH) and 2,5-dimethylpyrazine (2,5-DMP) as their primary antifungal volatile organic compounds (VOCs). Combined physiological, biochemical, and multi-omics analyses revealed that these two VOCs disrupt the structural integrity of the fungal cell wall and membrane. This disruption triggers abnormal energy metabolism and compensatory ATP accumulation, leading to a significant intracellular burst of reactive oxygen species and the impairment of primary antioxidant defenses. This sustained oxidative stress causes irreversible DNA damage, endoplasmic reticulum stress, and basal metabolic dysfunction. Consequently, this cascade induces apoptosis and significantly downregulates the expression of essential virulence genes. In conclusion, this study systematically elucidates the molecular network through which VOCs released by cave soil microorganisms antagonize P. destructans. These findings provide a theoretical foundation and candidate intervention molecules for the contactless biocontrol of WNS. Full article

Arthritis is a chronic inflammatory disease characterized by progressive joint damage, in which oxidative stress and exacerbated immune responses play a critical role. Synbiotics, defined as a combination of probiotics and prebiotics, may enhance these beneficial effects; however, their efficacy depends on maintaining microbial viability throughout gastrointestinal transit. In this study, we evaluated the anti-inflammatory and antioxidant effects of Levilactobacillus brevis LBH1070. Lacticaseibacillus paracasei ATCC 334 and phenylbutazone (PBZ) were used as probiotic and allopathic drug controls, respectively. Both probiotic strains significantly reduced paw edema by 46%, comparable to PBZ (45%), and decreased lipid oxidation (33–36%) and protein oxidation (40–45%), thereby preserving the integrity of the popliteal lymph node, the lymph node closest to the edema site. Furthermore, L. paracasei ATCC 334 and L. brevis LBH1070 reduced total T helper CD4+ lymphocyte infiltration in the popliteal lymph node by 44–54% and decreased IL-1β-producing T helper lymphocytes by 77–78%, surpassing the effect of PBZ (49%). TNF-α-producing T lymphocytes were also reduced by 60–62%, compared to PBZ (53%). These findings highlight the potential of L. brevis LBH1070, its synbiotic formulation, and L. paracasei ATCC 334 as complementary treatments to modulate immune responses and oxidative stress during arthritis. Full article

Sandstone–marble waste powder concrete composite structures serve as common load-bearing systems in tunnels, underground caverns, and similar engineering projects, where the interface roughness characteristics directly govern their overall stability and service safety. To investigate the influence of interface roughness on the failure behavior of the composite, four groups of sandstone–concrete composite specimens made with marble waste powder concrete were prefabricated with different joint roughness coefficients (JRC = 0, 7.84, 17.99, 20.79). The concrete matrix was prepared with marble waste powder incorporated at 25 wt% of the total binder, corresponding to 20.45 wt% of the total mixture, and the water-to-binder ratio was 0.20. Uniaxial compression tests were conducted with synchronous acoustic emission (AE) and digital image correlation (DIC) monitoring to examine the roughness-dependent mechanical response, energy evolution, damage activity, and strain localization of the composites. The results show that the peak stress and elastic modulus of the composite increase continuously with increasing JRC. When JRC increases from 0 to 20.79, the peak stress increases by 170.3% and the elastic modulus increases by 201.1%. The energy evolution mechanism transitions from progressive damage with gradual energy dissipation at low roughness to a three-stage mode at high roughness, characterized by initial frictional energy dissipation, intermediate energy storage, and rapid elastic energy release and dissipated energy increase near failure. DIC results further reveal that increasing interface roughness suppresses interfacial shear slip and promotes tensile-dominated strain localization, whereas excessive roughness may induce local stress concentration around asperities and increase the tendency toward abrupt post-peak instability, the failure mode changes from mixed tensile–shear failure with obvious interfacial slip to tensile-dominated failure. Full article

Filament–wound carbon fiber composites are widely used in lightweight structural applications, where their mechanical performance is strongly affected by manufacturing-induced heterogeneities. In this study, the tensile behavior of carbon fiber composite specimens produced by filament winding was investigated using Digital Image Correlation (DIC) to obtain full-field strain measurements. Uniaxial tensile tests were performed while monitoring the spatial distribution of strain over the specimen surface. Beyond conventional global stress–strain characterization, DIC enabled the identification of significant strain heterogeneity both within individual specimens and among different specimens manufactured under the same nominal conditions. Localized strain concentrations were observed to develop in specific regions, revealing non-uniform deformation patterns that were not captured by global measurements alone. The results demonstrate that, despite similar global mechanical responses, substantial variability exists at the local scale. This intra and inter-specimen heterogeneity highlights the influence of filament winding architecture and local variability on tensile performance. The study underscores the limitations of relying solely on global measurements and emphasizes the capability of DIC to provide deeper insight into strain distribution and damage initiation mechanisms. These findings support the use of full-field optical techniques as a powerful tool for the mechanical characterization and quality assessment of filament–wound composite structures. Full article

This paper investigates the seismic performance of precast concrete shear-wall subassemblies connected by post-cast ultra-high performance concrete (UHPC) zones and short lap-spliced reinforcement with a lap length of $10d$, where d denotes the diameter of the reinforcement bar. Seven quasi-static cyclic tests were conducted, including one cast-in-place control specimen, five specimens with horizontal UHPC back-cast joints at the wall base, and one exploratory specimen with both horizontal and vertical UHPC back-cast joints. The variables considered were the joint arrangement and the axial compression ratio. The specimens with horizontal joints generally exhibited compression-flexure-dominated damage, and the crushing zone shifted from the wall-footing interface to the ordinary concrete immediately above the UHPC back-cast zone. The specimen with the vertical joint (TW6) exhibited bending-shear damage, accompanied by limited in-plane lateral slip at the beam–wall joint and shear damage of several vertical bars. Specimen TW2, with an axial compression ratio of 0.30, was identified as a construction-quality-sensitive case because an insufficient local UHPC cover caused splitting damage and reduced hysteretic stability. The strain measurements indicate that, within the limits of the present instrumentation, the 10d lap in the UHPC zone provided effective stress transfer in the tested specimens; however, direct interface-slip and bond-slip tests are still required for generalized design verification. Under an axial compression ratio of 0.20, TW1 and TW6 showed comparable seismic indices to the cast-in-place specimen, but the conclusions are limited to the tested configurations. All specimens reached ultimate drift ratios greater than 1/100, and their seismic performance is discussed together with failure mode, stiffness degradation, energy dissipation, and connection reliability. Full article

With the advancement of marine engineering, coral concrete—comprising coral coarse aggregate, coral sand, and seawater—has garnered increasing research interest. To further investigate its compressive mechanical behavior under axial and lateral biaxial stress states, a total of 9 prismatic specimens under axial loading and 45 cubic specimens under biaxial loading were prepared, encompassing three strength grades (C20, C30, and C40) and five lateral stress ratios (0, 0.25, 0.5, 0.75, and 0.9). The failure modes and corresponding axial and biaxial stress–strain curves were meticulously recorded. The axial mechanical response was systematically analyzed, leading to the establishment of a compressive damage constitutive model based on the Weibull distribution. Additionally, the influence of the lateral stress ratio on both peak stress and peak strain was examined, and multiple biaxial failure criteria were formulated. Experimental results reveal that the failure modes of coral concrete specimens are analogous to those of natural coarse aggregate concrete and are significantly affected by the lateral stress ratio. Specifically, an increase in the lateral stress ratio results in higher peak stress, while the absolute value of peak strain exhibits a linear variation. Finally, the proposed axial damage constitutive model and the biaxial failure criteria are rigorously validated against the experimental data. Full article

Aerospace load-bearing components require materials that exhibit high specific strength, excellent fatigue resistance, and superior environmental adaptability. Titanium alloys are indispensable for aerospace applications because of their exceptional mechanical properties, particularly their outstanding high specific strength, and their peak mechanical strength is typically achieved through solution heat treatment followed by artificial aging. This review systematically summarizes recent advances in the compositional design, microstructural evolution, and critical microstructure–property relationships of aerospace titanium alloys. It further highlights intrinsic effects of alloying elements on phase stability, dislocation behavior, and phase transformation pathways, and analyzes how lamellar, equiaxed, and bimodal microstructures regulate dislocation transfer, local strain partitioning, and damage evolution. The interactions and competition among deformation and phase-transformation mechanisms, including slip anisotropy, deformation twinning, stress-induced phase transformations, and ω-related processes, are critically assessed. However, unresolved challenges remain in quantitatively characterizing multi-mechanism coupling and local heterogeneity. To address these challenges, this review elucidates the transition rules of dominant mechanisms across different microstructures and proposes a high-precision digital composition–microstructure–property mapping framework to facilitate predictive and service-oriented alloy design. Full article