Search Results (161)

Tribocorrosion is one of the main degradation mechanisms affecting metallic components exposed simultaneously to mechanical wear and electrochemical corrosion. In this work, the influence of the Nb/Ti ratio on the tribocorrosion behavior of Fe–Cr–Mo–Nb–Ti multicomponent alloys produced by vacuum arc melting was investigated. The alloys were designed through systematic variations in the relative contents of niobium and titanium to assess their effect on electrochemical stability, wear resistance, and surface degradation. Electrochemical behavior was evaluated by potentiodynamic polarization in a 3.5 wt.% NaCl solution, while tribological and tribocorrosion tests were conducted using a ball-on-disk configuration under controlled conditions. Post-test surface analysis was performed using stereomicroscopy combined with digital image processing, enabling three-dimensional topographical reconstruction of the wear tracks and extraction of quantitative parameters including groove depth, pile-up height, wear track width, and surface roughness. The results demonstrate that the Nb/Ti ratio significantly influences both electrochemical and tribological responses. The alloy with the highest Nb/Ti ratio exhibited the best overall performance, showing the lowest corrosion current density (5.37 × 10⁻⁸ A/cm²) under static conditions and the lowest wear rate (1.32 mm³/mm²·year), together with the least severe surface degradation, characterized by a groove depth of approximately 7.8 µm and minimal pile-up formation. A progressive deterioration in performance was observed as the Nb/Ti ratio decreased, with the lowest-ratio compositions presenting higher wear severity and surface instability. The AISI 316L reference material exhibited intermediate performance across all evaluated parameters. Overall, increasing the Nb/Ti ratio enhances passive film stability, reduces plastic deformation, and mitigates material removal under tribocorrosion conditions. The incorporation of three-dimensional surface analysis provides a more robust evaluation of wear mechanisms, supporting the design of multicomponent alloys with improved resistance to combined mechanical and electrochemical degradation in aggressive environments. Full article

Synthetic polymers are widely used in stone conservation, yet their long-term biological stability remains insufficiently evaluated. This study investigates the microbial susceptibility of three commonly used acrylic consolidants, Paraloid B-72, B-66, and B-44, applied to deteriorated limestone. Bacteria, fungi, and actinomycetes were isolated from a deteriorated limestone false door and screened for acid production. From each microbial group, only the strong acid-producing isolates were selected for further investigation, including evaluation of their ability to utilize the three Paraloid resins as sole carbon sources and their deterioration potential on limestone cubes before and after consolidation. Deterioration was assessed by weight loss, compressive strength testing, stereomicroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). All selected strong acid-producing isolates demonstrated the ability to grow on the tested polymers, confirming their biodegradation potential. Mixed microbial cultures caused greater weight loss and compressive strength reduction than single isolates, attributed to synergistic metabolic interactions. Among the consolidants, Paraloid B-72 showed the highest susceptibility to microbial attack, while Paraloid B-66 exhibited comparatively greater resistance, attributed to the steric hindrance of its isobutyl side groups and higher surface hydrophobicity. FTIR and XRD analyses confirmed ester bond hydrolysis, progressive gypsum formation, and structural alteration of the limestone substrate. These findings demonstrate that acrylic consolidants commonly used in stone conservation are not biologically inert and may actively contribute to biodeterioration under microbial colonization, highlighting the need for developing bio-resistant conservation materials. Full article

This observational study evaluated changes in selected performance parameters of 15 new high-speed dental handpieces after eight months of routine clinical use in a routine educational undergraduate environment (two 4 h daily clinical shifts, five days per week, with repeated sterilization cycles). All handpieces underwent routine cleaning, lubrication, and autoclave sterilization as instructed. The turbine components from the handpieces were disassembled and examined by stereomicroscopy before and after use, while free-running speed and friction grip force were assessed at the same intervals. Two handpieces were no longer operational at follow-up due to ball bearing failure. Paired t-test was performed for free-running speed and friction grip force. Among the remaining handpieces, statistically significant reductions were observed in both free-running speed and friction grip force (p < 0.01). Microscopic examination of the rotors revealed surface alterations consistent with corrosion and wear. Within the limitations of this study, routine clinical use over an eight-month period was associated with measurable changes in key performance characteristics of high-speed dental handpieces in educational clinical settings. Full article

The objective of this study was to evaluate colour changes in cotton fibres within knitted fabric structures under different light exposure conditions and to assess the applicability of forensic analytical methods for this purpose. Fabrics of three distinct colours were exposed to two types of irradiation: natural sunlight and artificial light in a controlled climatic chamber. A multi-scale analytical approach was applied, including visual inspection and stereomicroscopy for macro-level evaluation, followed by bright-field microscopy, fluorescence microscopy, and UV–Vis microspectrophotometry for single-fibre characterisation. Visual assessment of fabrics revealed perceptible colour differences between exposed and unexposed samples, whereas stereomicroscopy did not consistently enhance the detection of these alterations. Bright-field and fluorescence microscopy showed no visually perceptible differences between fibres from exposed and unexposed fabrics of the same colour. Microspectrophotometric measurements did not reliably capture colour changes in single cotton fibres, particularly in samples exposed to natural sunlight. Furthermore, total colour difference (ΔE) values, ranging from 0.248 to 6.652, were found to be unreliable at the single-fibre level due to significant spatial variability across different measurement sites. The findings indicate that, while light exposure may induce perceptible colour alterations in cotton knitted fabrics, the forensic examination of single fibres does not necessarily reflect these macro-scale changes. From a forensic perspective, the stability of microscopic and microspectrophotometric characteristics supports reliable fibre comparison, even after post-event exposure to sunlight. Full article

This study investigates how processing parameters and powder characteristics influence the mechanical performance of thermal barrier coatings (TBCs) applied to a Ti-6Al-4V alloy. Two TBCs were deposited by Atmospheric Plasma Spray (APS) using different processing conditions, feedstock characteristics, and coating thicknesses (thin and thick configurations). TBC characterization included powder size analysis, scanning electron microscopy (SEM), surface roughness, X-ray diffraction, instrumented indentation, and scratch testing. Mechanical behavior was assessed using creep testing at 125 MPa and 500 °C for coated and uncoated samples. Fracture surfaces of crept samples were analyzed by SEM and stereomicroscopy. Thicker TBC exhibited higher elastic modulus but contained microcracks and higher porosity, resulting in a higher steady-state creep rate (0.0006 h⁻¹, approximately 167% above the uncoated substrate) and reduced rupture time. Conversely, thinner TBC remained initially crack-free, promoting stress redistribution and leading to a lower creep rate (0.0002 h⁻¹, about 67% below the substrate) and delayed failure. Fractographic analysis revealed ductile fracture of Ti-6Al-4V in all conditions, indicating that coatings influenced damage accumulation rather than fracture mode. These findings underscore the combined effect of processing parameters and coating architecture on TBC performance for aerospace applications. Full article

Aim: Fixed dental prostheses (FDPs) are increasingly fabricated from high-strength ceramic materials; however, their fracture behavior under flexurally dominated loading remains incompletely understood. This in vitro study aimed to compare the mechanical performance and fracture mechanisms of four FDP material systems under standardized bending conditions. Materials and Methods: Three-unit CAD/CAM-fabricated FDPs were produced from metal-ceramic (P1), zirconia-ceramic (P2), monolithic zirconia (P3), and monolithic lithium disilicate (P4) materials (n = 9 per group). Specimens were subjected to three-point bending until failure. Crack initiation load, maximum load, displacement, and stiffness were recorded, and fracture behavior was analyzed using stereomicroscopy, micro-computed tomography (μCT), and scanning electron microscopy (SEM). Results: Metal-ceramic FDPs (P1) exhibited the highest crack initiation load (0.89 kN) and maximum load (1.91 kN), with failure predominantly occurring through ceramic veneer delamination without complete framework fracture. Monolithic zirconia FDPs (P3) demonstrated the most brittle failure behavior, characterized by abrupt fracture and unstable crack propagation immediately after crack initiation. Zirconia-ceramic (P2) and lithium disilicate (P4) FDPs showed intermediate mechanical performance, with lithium disilicate exhibiting greater resistance to catastrophic failure (F_max = 0.94 kN) compared with zirconia–ceramic FDPs. Conclusions: These findings refine current assumptions regarding the mechanical reliability of monolithic zirconia FDPs under flexural loading and highlight the importance of fracture behavior, rather than peak strength alone, in material selection. Lithium disilicate and metal-ceramic systems exhibited more favorable damage-tolerant responses under static flexural loading. These findings should be interpreted within the limitations of this in vitro model and should not be directly extrapolated to long-term clinical performance. Full article

The Amazonian açaí waste is promising for producing charcoal through pyrolysis and bioenergy through combustion, but the property losses from its poor disposal in the environment remain unknown. Therefore, this work aimed to analyze how different storage conditions of the açaí waste over time, which mimic the reality throughout the Amazon, modify its bioenergetic properties. The samples were stored in a covered greenhouse for nine months in the following conditions: immersed in water, on the soil, and in open plastic bags. The biomass was analyzed by Fourier-transformed near-infrared spectroscopy, physical properties, stereomicroscopy, proximate composition, and thermogravimetry. The degraded waste showed endocarp attack and fungi proliferation. The chemical groups of primary cell wall components were concentrated, unlike water-soluble materials, raising the fixed carbon from 22% to 25% after 30 days. Consequently, higher heating values were kept (≈19 MJ/kg). However, water immersion storage sharply decreased the waste basic density from 0.81 g/cm³ to 0.56 g/cm³, dropping the energy density from 12 GJ/m³ to 8 GJ/m³. Moreover, storage raised ash content from 1.1% up to 1.9%. The storage hindered the start of the main phases of combustion and pyrolysis, which were later intensified, especially for soil-stored waste. Therefore, more stable combustion and pyrolysis require fresh waste. Besides natural drying, plastic bag storage over time kept the waste quality closer to that of the fresh waste. Full article

Microplastics (MPs) are prevalent in coastal habitats, but their occurrence in highly vulnerable coastal zones and human exposure risk are poorly understood, especially in developing nations like Bangladesh. This inquiry focused on the prevalence and potential hazards of MPs in surface sediment and shallow groundwater samples collected from 12 sites in Cox’s Bazar, Bangladesh, from August to October 2023. Using stereomicroscopy and FTIR, MPs were quantified, with concentrations ranging from 60 to 813.33 MPs/kg in surficial sediment and 3.34 to 36.66 MPs/L in shallow groundwater, with mean values of 294.38 ± 26.61 MPs/kg and 18.91 ± 4.75 MPs/L. The dominant MPs were composed of transparent and white fibers, ranging in size from 0 to 0.5 mm, with HDPE (High-Density Polyethylene) and PP (Polypropylene) identified as the most commonly found polymers. To assess MP exposure in humans and the environment, this investigation used three indices: the polymer hazard index (PHI), the pollutant load index (PLI), and the estimated daily intake (EDI). The findings indicate that children exhibit greater exposure than adults, with observed low contamination levels, alongside a spectrum of toxicity from moderate to extreme. This study enhances understanding of MP contamination in the surficial sediments and shallow groundwater of Bangladesh, highlighting the need for further investigation into ecotoxicology, human health risks, legislation, and related issues. Full article

Graphene oxide (GO) is a promising nanocarrier for the delivery of oligonucleotides. It offers a high loading capacity, efficient cellular uptake, and surface functionalization. MicroRNA-21 (miR-21) is a well-characterized oncomiR commonly overexpressed in hepatocellular carcinoma (HCC). In HCC, miR-21 contributes to tumor progression, inflammation, and angiogenesis. In a previous in vitro study, we showed that GO alone induces the upregulation of pro-inflammatory and tumor-related genes in HepG2 cells. However, conjugation with an antisense miR-21 (GO-antisense miRNA 21) reverses this effect, suggesting a potential therapeutic application. This study aims to evaluate the antitumor and anti-angiogenic efficacy of the GO-antisense miR-21 nanosystem in ovo using the chick embryo chorioallantoic membrane (CAM) model. Fertilized chicken eggs (n = 4 per group) were randomized into untreated, GO-treated, and GO–antisense miR-21-treated cohorts. A dose of 200 μL (GO 10.0 µg/mL: antisense miR-21 5.0 pmol/mL) was administered intratumorally. Tumor size, volume, and vascularization were monitored through stereomicroscopy and histological analysis. The expression of inflammatory and tumor-associated genes (IL-8, MCP-1, TIMP-2, ICAM-1 and NF-kB) was assessed by quantitative PCR. Given its prominent response, IL-8 protein expression was further analyzed via immunofluorescence. To evaluate tumor-specific delivery, FITC-labeled GO was tracked by confocal microscopy. Our data revealed that treatment with unfunctionalized graphene oxide (GO) unexpectedly promoted tumor vascularization and led to a significant increase in tumor weight. This was accompanied by upregulation of inflammatory markers. In contrast, GO-antisense miR-21 significantly reduced the tumor volume and vessel density. It also successfully downregulated all target genes. Confocal imaging demonstrated preferential accumulation of the nanosystem within the tumor mass. Our results highlight the dual anti-inflammatory and anti-angiogenic effects of GO-antisense miRNA 21 in ovo and support its potential as a targeted nanoplatform for HCC treatment. Full article

This study examines how manufacturer-specific additive formulations used to obtain nominally identical black PLA filaments influence the thermal, mechanical, and tribological performance of FDM-printed parts. Five commercial filaments were analyzed under identical processing conditions using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile testing, pin-on-disc measurements, and stereomicroscopy. The filaments exhibited substantial compositional variability, with total additive contents ranging from 2.08 wt.% to 27.82 wt.%. One filament (M5) contained a significant fraction of inorganic fillers, confirmed by SEM/EDX as Ca-, Na- and Mg-based oxides and silicates, identifying it as a PLA-based composite despite being marketed as standard PLA. These differences strongly affected thermal behavior (Tg, Tcc, Tm) and translated directly into the performance of the printed parts. Ultimate tensile strength varied by 88.91% across all filaments (19.38–36.61 MPa), but only by 13% among the four conventional PLA filaments (M1–M4). Tribological performance differed markedly: mean coefficients of friction ranged from 0.246 (M3) to 0.368 (M2), a spread of approximately 50%, with wear-track morphologies reflecting the frictional response. Overall, the results show that PLA filaments cannot be treated as interchangeable materials. Greater transparency and standardized reporting of filament composition are needed to ensure reproducibility and support informed material selection in FDM applications. Full article

Birmingham hip resurfacing (BHR) is an alternative to bone-sparing total hip arthroplasty; however, failures may be associated with the cementing technique. This study aimed to evaluate the characteristics of the cement layer and potential failure mechanisms. BHR explants were analyzed using radiographic evaluation, stereomicroscopy, scanning electron microscopy (SEM), and histopathology. The cement layer was nonuniform, with excessive thickness in the dome regions and insufficient lateral coverage. Increased cement penetration values exceeded recommended thresholds. SEM analysis revealed inhomogeneous cement with cracks, air inclusions, and loosening at the cement–prosthesis interface. BHR failure may be associated with a complex interplay between cementation parameters, cement mantle morphology, and the biological response at the bone–cement interface, as well as interactions at the cement–prosthesis interface. Microscopic evaluation may provide valuable insights into the mechanisms potentially contributing to BHR prosthesis failure. Full article

Electrospinning and electrospraying nanotechnologies were used to valorise agro-industrial residues into biohybrid controlled-release polyphenol (CRP) scaffolds. Four polyhydroxybutyrate ± polycaprolactone (PHB±PCL) architectures were fabricated that differed in polymer phase, Klason lignin from hazelnut shell (HS-KL) presence vs. absence, and co-location with grape-pomace polyphenols (GP-PPs), as well as in distribution between fibres and bead-like depots. Scaffolds were characterised using optical microscopy/stereomicroscopy/SEM, FTIR, UV–Vis spectroscopy, and dynamic water contact angle (absorption). GP-PP release was monitored for 14 days at ~25 °C and 37 °C, the latter representing shallow-soil hot-spell conditions in Mediterranean zones. All matrices exhibited multimodal release, with modest initial bursts and three phases (burst, mid, and late tail), analogous to controlled-release fertiliser profiles. At ~25 °C, the PHB/PCL matrix with HS-KL confined to PHB fibres and GP-PP in large PCL beads showed the highest total GP-PP release, whereas the architecture with HS-KL and GP-PP co-located in both PHB and PCL fibres and in PCL depots combined high total release with a smoother, well-metered late phase. At 37 °C, this HS-KL-GP-PP co-located scaffold was the most robust, retaining the highest total and late tail release. These results identify HS-KL-GP-PP co-located PHB/PCL architectures as promising carriers for temperature-resilient delivery of bioactive polyphenols in Mediterranean agrosystems. Full article

With the growing clinical use of ion-releasing resin composites, their repairability has become an important consideration in minimally invasive restorative dentistry. Therefore, this study investigated the repair bond strength of a universal composite restorative to commercially available and experimental ion-releasing resin composite materials. Specimens (n = 8 per group) were produced from three commercially available ion-releasing composite materials (ACTIVA BioACTIVE-RESTORATIVE, Cention Forte, Beautifil II), one experimental ion-releasing resin composite containing 20 wt% bioactive glass fillers, and two conventional resin composites (3M Filtek Supreme XTE, Ceram.x Spectra ST), and aged by thermal cycling in artificial saliva (5000 cycles, 5–55 °C). Substrate surfaces were sandblasted (Al₂O₃, 50 µm), silanized (Monobond Plus), and repaired using adhesive (OptiBond FL) and universal resin composite (Ceram.x Spectra ST). After further thermal cycling, micro-tensile repair bond strength was assessed and analyzed using one-way ANOVA followed by Tukey’s post hoc test. Failure modes were determined by stereomicroscopy (25× magnification) and statistically compared among the groups. Highest mean repair bond strength values were obtained for ACTIVA BioACTIVE-RESTORATIVE, Beautifil II, and 3M Filtek Supreme XTE (53.8, 46.2, and 43.0 MPa, respectively), which did not differ significantly among each other. ACTIVA BioACTIVE-RESTORATIVE attained significantly higher bond strength than the experimental composite, Ceram.x Spectra ST, and Cention Forte, and showed the highest incidence of cohesive failures (40%). No significant bond strength differences were detected among Beautifil II, 3M Filtek Supreme XTE, experimental composite, Ceram.x Spectra ST, and Cention Forte (36.2–46.2 MPa). In conclusion, ion-releasing resin composites can be repaired with conventional universal composite and show repair bond strength values at least as high as those of conventional composite materials. Full article

Disposable plastic production may be an understudied source of indoor microplastics (MPs) with implications for occupational exposure. These studies provide a preliminary baseline characterization of MP contamination and potential exposure within a disposable plasticware production administrative environment from Morbi district, Gujarat, India. As the dataset is derived from a single composite dust sample collected over a seven-day period, the results should be interpreted as indicative of site-specific conditions rather than broadly generalizable estimates. Sample processed using a contamination-controlled workflow (H₂O₂ digestion, ZnCl₂ density separation, stereomicroscopy) and micro-Raman confirmation. The dust contained 2112 MPs/g, was overwhelmingly fragment-dominated (98.5%), and enriched in the 100–200 µm size class (42.4%); color profiling showed predominance of white (60.6%) and red (32.4%) particles. Polymer identification indicated a polystyrene (PS)-dominated signature (55%) with PET as a secondary contributor (25%). Ingestion is the primary pathway (~77% of intake). Results demonstrate that non-production indoor spaces adjacent to plastic manufacturing can act as MP hotspots, carrying polymer-specific fingerprints and measurable exposure burdens for administrative staff. Findings support targeted mitigation (source containment, enhanced filtration, cleaning) and recommend broader, multi-site airborne plus settled sampling to refine exposure and health-risk assessments. Full article

The smut fungus Thecaphora frezzii causes severe yield losses in peanuts (Arachis hypogaea) in Argentina. Previous work established its fully intracellular biotrophic progression through subterranean organs and its exclusive sporulation within the seed coat, yet the ontogeny of teliospore formation in planta remained unresolved. Here, we applied a pragmatic correlative multiscale microscopy approach based on serial paraffin sections examined by stereomicroscopy, light microscopy, confocal laser scanning microscopy, and scanning electron microscopy, enabling spatial correlation of fungal structures within their tissue context. Using this integrative framework, we characterized the organization and progression of sporogenic structures associated with teliosporogenesis. Teliosporogenesis proved to be tightly synchronized with host tissue context and seed developmental stage, and was consistently preceded by a marked reorganization of sporogenous hyphae into three-dimensional coiled hyphal aggregates embedded in a mucilaginous matrix. These precursors undergo hyphal fragmentation followed by central–peripheral differentiation, whereby a small number of central units enlarge and individualize into teliospore initials while peripheral elements collapse, yielding stable teliospore balls as the final sporogenic product. This developmental sequence defines a distinct ontogenetic pattern not captured by current schemes of sporogenesis, here designated the Teliospore-ball type. Our results clarify the developmental pathways of T. frezzii sporulation in planta and demonstrate how accessible multiscale microscopy can be used to integrate structural information across spatial scales in complex plant–fungus interactions. Full article