Search Results (2,419)

This study presents the synthesis and characterization of silver nanoparticles (AgNPs) using two Spirulina platensis extracts: one of them cultivated in a bioreactor in Bulgaria (near Varvara village), and the other one from the local market in Bulgaria (Dragon Superfoods). To assess their properties and stability, ATR-FTIR, TEM (Transmission Electron Microscopy) images, and zeta potential were used. Chemical content of the extracts and AgNPs obtained were assessed, as well as their antimicrobial and anti-inflammatory activities. We found that the extracts’ origin significantly influenced nanoparticle morphology, surface charge, and bioactivity. AgNPs were spherical and different in size from Bioreactor 4–8 nm, while Dragon obtained larger particles, about 20 nm. We found that synthesis altered the chemical content of the extracts, particularly in lipid, protein, and tocopherol content, suggesting active involvement of Spirulina-derived biomolecules in nanoparticle formation. Antimicrobial assays showed slightly higher activity for Dragon AgNPs against P. aeruginosa (21 mm) and S. enteritidis (23 mm), with similar effects against L. monocytogenes and S. aureus. At 2.5 mg/mL, both samples protected human albumin from thermal denaturation more effectively (23.36% and 20.07%) than prednisolone (16.99%). Based on the obtained results, AgNPs from Spirulina platensis can be attributed as multifunctional agents with anti-inflammatory and antimicrobial activity. Full article

In this study, we utilized Thermo-Calc software (2023a) to optimize the heat treatment process of martensitic stainless steel 90Cr18MoV through phase diagram calculations. The microhardness of 90Cr18MoV was characterized using a nanoindentation instrument. The microstructural morphology of the samples was analyzed using scanning electron microscopy (SEM). The composition of the samples was characterized through scanning electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). Additionally, laser confocal microscopy (FIB) and transmission electron microscopy (TEM) were employed to characterize the precipitate phase composition and size before and after heat treatment, while also observing the dislocation structure within the samples. The relationship between the quenching temperature and the percentage of residual austenite content in the material was established. The influence of the dislocation structure and precipitate size on the hardness of the samples was investigated. The research findings confirm that the observed secondary hardening phenomenon in tempered samples is attributed to the co-precipitation of two types of carbides, M₂₃C₆ and MC, within the matrix. The study investigated the effects of the tempering temperature and duration on the size of secondary precipitates, indicating that M₂₃C₆ and MC particles with sizes less than or equal to 20 nm contribute to enhancing the matrix, while particles larger than 30 nm lead to a reduction in hardness after tempering. Notably, during the tempering process, M₂₃C₆ precipitated from the matrix nucleates on MC. Full article

Background/Objectives: Cervical cancer remains a major health challenge, especially in low-resource regions with limited diagnostic and advanced treatment options. Nanotechnology-based strategies offer promising alternatives to conventional chemotherapy by reducing systemic toxicity and enabling site-specific delivery. Methods: In this study, halloysite (Hall) was functionalized with green-synthesized 2 wt% zinc oxide (GZn) and silver (GAg) nanoparticles (NPs) using Tribulus terrestris extract (25 mM) to enhance cisplatin (Cp) and carboplatin (Cbpt) delivery for targeted cervical cancer therapy. Results: Structural and morphological analyses confirmed the successful integration of GZn and GAg NPs into the Hall without compromising its tubular integrity. Cp or Cbpt adsorption studies with varying times (0.15–12 h), as well as drug/Hall ratios (10–50) and pH levels (5; 6.6; 7.4; 9.0; and 10.5), revealed greater Cp adsorption than Cbpt, attributed to its higher reactivity and affinity toward the Hall surface. pH-responsive release studies biphasic drug release for non-PEGYlated formulations, with Cp (14% with 2 h) and Cbpt (10% with 0.5 h), whereas PEGYlated systems exhibited sustained release under acidic tumor-like conditions, achieving 14% in 72 h for Cp and 4.5% in 72 h for Cbpt. Release kinetics followed either Fickian or non-Fickian diffusion depending on pH and drug type, with the Korsmeyer–Peppas model offering a strong fit (R² > 0.85). In vitro assays revealed that Cbpt/GZn-Hall/PEG, Cp/GZn-Hall/PEG, and Cbpt/GAg-Hall/PEG induced dose-dependent cytotoxicity against HeLa while sparing HFF-1 fibroblasts. Conclusions: These findings indicate that green-synthesized nanohybrids are promising carriers for targeted Cp and Cbpt delivery, warranting further in vivo evaluation for cervical cancer therapy. Full article

As a sustainable alternative to conventional fertilizers, rock dusting is an emerging agroecological strategy to improve soil health and nutrient availability. This study aimed to quantify the effects of basalt powder (BP) application on the chemical attributes of a Ferralsol and the morphological responses of young Ilex paraguariensis (yerba mate) plants. The experiment was conducted in a randomized block design with five BP doses (0, 3.8, 7.6, 15.2, and 30.4 Mg ha⁻¹), where resulting soil and plant parameters were statistically analyzed. Results demonstrated that BP significantly increased available calcium, magnesium, and silicon in the soil (p ≤ 0.05) without altering pH or potassium levels. This soil enrichment directly correlated with a significant increase in the number of leaves per plant (p ≤ 0.01), which was strongly associated with soil Mg²⁺ (r = 0.73) and Si (r = 0.40). However, no significant effects were observed on plant height or stem diameter. We conclude that basalt powder acts as an effective slow-release source of Ca, Mg, and Si, primarily stimulating leaf development rather than immediate plant structural growth. This finding is consistent with the gradual nutrient release from silicate rocks and suggests that BP is a viable tool for enhancing soil fertility in yerba mate systems, although long-term evaluation is essential to understand its full agronomic potential. Full article

As internal combustion engine (ICE) systems are increasingly exposed to severe thermal and oxidative environments, the oxidation resistance and structural integrity of exhaust valve materials have become critical for maintaining long-term engine reliability and efficiency. This study presents a comparative evaluation of the cyclic oxidation behavior of two candidate valve steels, 1.4718 (ferritic stainless steel) and 1.4871 (austenitic stainless steel), under service-temperature conditions. The specimens were exposed to repeated oxidation at 550 °C, 650 °C and 750 °C for 25 cycles in ambient air. The surface and cross-sectional morphologies of the oxide layers were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) to investigate oxide scale composition, thickness, and growth characteristics. The oxidation behavior of both alloys proceeded in two distinct stages: an initial phase marked by accelerated oxidation, followed by a slower, more stable growth period. The extent of oxidation intensified with increasing temperature. The 1.4718 alloy developed relatively porous but compositionally stable oxide layers consisting primarily of Fe- and Cr-based spinels such as FeCr₂O₄ and Cr₂SiO₄. In contrast, the 1.4871 alloy formed a dense, adherent, dual-layered oxide scale composed of an outer Mn₂O₃-rich layer and an inner Cr₂O₃-rich layer, attributable to its high Mn and Cr content. The results underscore the critical influence of elemental composition, particularly Cr, Mn and Si, on oxide scale stability and spallation resistance, demonstrating the superior cyclic oxidation resistance of the 1.4871 alloy and its potential suitability for exhaust valve applications in thermally aggressive environments. Full article

Engineering phase-selective gel composites presents a promising route to enhance both CO₂ adsorption and conversion efficiency in photocatalytic systems. In this work, Cu₉S₅/TiO₂ gel composites were synthesized via a hydrazine-hydrate-assisted hydrothermal method, using TiO₂ derived from a microwave-assisted sol–gel process. The resulting materials exhibit a porous gel-derived morphology with highly dispersed Cu₉S₅ nanocrystals, as confirmed by XRD, TEM, and XPS analyses. These structural features promote abundant surface-active sites and interfacial contact, enabling efficient CO₂ adsorption. Among all samples, the optimized 0.36Cu₉S₅/TiO₂ composite achieved a methane production rate of 34 μmol·g⁻¹·h⁻¹, with 64.76% CH₄ selectivity and 88.02% electron-based selectivity, significantly outperforming Cu₉S₈/TiO₂ synthesized without hydrazine hydrate. This enhancement is attributed to the dual role of hydrazine: facilitating phase transformation from Cu₉S₈ to Cu₉S₅ and modulating the interfacial electronic environment to favor CO₂ capture and activation. DFT calculations reveal that Cu₉S₅/TiO₂ effectively lowers the energy barriers of critical intermediates (*COOH, *CO, and *CHO), enhancing both CO₂ adsorption strength and subsequent conversion to methane. This work demonstrates a gel-derived composite strategy that couples efficient CO₂ adsorption with selective photocatalytic reduction, offering new design principles for adsorption–conversion hybrid materials. Full article

Lithium plating (LP), as a specific degradation mechanism in lithium-ion batteries (LIBs), has been thoroughly investigated regarding formation conditions and potential safety hazards, but it is yet unknown how this effect influences the mechanical properties of batteries in the case of mechanical deformation. To address this issue, pouch cells used in EVs were artificially aged (AA) to a state of health of 80–82% in conditions that predominantly cause the formation of LP. These cells were subjected to a mechanical abuse load, and safety-relevant parameters, such as tolerated deformation level, failure force, and the process of thermal runaway (TR), were analyzed and compared with respective fresh (F) and aged cells of the same type. Complementary microscopy analyses were carried out to compare the found changed mechanical response with the different layer morphology caused by LP. The tests did exhibit a significantly different mechanical response of cells in the three states but also clearly altered short-circuiting behavior. The tolerated peak force at discharge state dropped by −28% and at charge state by −37% compared to fresh cells, while the deformation at failure slightly increased by +6% for the AA cells. A clear reduction in stiffness (−16%) of the LP cells was attributed to the formed layer, identified as mossy LP. The significantly stronger voltage drop at failure, seen for the LP cells, was associated with severe exothermal reactions of LP in contact with air and moisture during TR. This study revealed the strong influence of LP on the mechanical properties of LIBs. However, the transferability of the findings to other cell chemistries or formats is unclear, emphasizing the need for further investigations in this research field. Full article

Supercritical CO₂ (ScCO₂) injection has emerged as a promising method to enhance shale gas recovery while simultaneously achieving CO₂ sequestration. This research investigates how ScCO₂ interacts with water and shale rock, altering the pore structure characteristics of shale reservoirs. The study examines shale samples from three marine shale formations in southern China under varying thermal and pressure regimes simulating burial conditions at 1000 m (45 °C and 10 MPa) and 2000 m (80 °C and 20 MPa). The research employs multiple analytical techniques including XRD for mineral composition analysis, MICP, N₂GA, and CO₂GA for comprehensive pore characterization, FE–SEM for visual observation of mineral and pore changes, and multifractal theory to analyze pore structure heterogeneity and connectivity. Key findings indicate that ScCO₂–water–shale interactions lead to dissolution of minerals such as kaolinite, calcite, dolomite, and chlorite, and as the reaction proceeds, substantial secondary mineral precipitation occurs, with these changes being more pronounced under 2000 m simulation conditions. Mineral dissolution and precipitation cause changes in pore structure parameters of different pore sizes, with macropores showing increased PV and decreased SSA, mesopores showing decreased PV and SSA, and micropores showing insignificant changes. Moreover, mineral precipitation effects are stronger than dissolution effects. These changes in pore structure parameters lead to alterations in multifractal parameters, with mineral precipitation reducing pore connectivity and consequently enhancing pore heterogeneity. Correlation analysis further revealed that H and D₋₁₀–D₁₀ exhibit a significant negative correlation, confirming that reduced connectivity corresponds to stronger heterogeneity, while mineral composition strongly controls the multifractal responses of macropores and mesopores, with micropores mainly undergoing morphological changes. However, these changes in micropores are mainly manifested as modifications of internal space. Siliceous shale samples exhibit stronger structural stability compared to argillaceous shale, which is attributed to the mechanical strength of the quartz framework. By integrating multifractal theory with multi–scale pore characterization, this study achieves a unified quantification of shale pore heterogeneity and connectivity under ScCO₂–water interactions at reservoir–representative pressure–temperature conditions. This novelty not only advances the methodological framework but also provides critical support for understanding CO₂–enhanced shale gas recovery mechanisms and CO₂ geological sequestration in depleted shale gas reservoirs, highlighting the complex coupling between geochemical reactions and pore structure evolution. Full article

In developing countries, indoor air pollution in rural areas is often attributed to the use of solid biomass fuels for cooking. Such fuels generate particulate matter (PM), carbon monoxide (CO), carbon dioxide (CO₂), polyaromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs). PM created from biomass combustion is a pollutant particularly damaging to health. This rigorous study employed a personal sampling device and multi-stage cascade impactor to collect airborne PM (including PM_2.5) and deposited ash from 20 real-world kitchen microenvironments. A robust analysis of the PM was undertaken using a range of morphological, physical, and chemical techniques, the results of which were then compared to a controlled burn experiment. Results revealed that airborne PM was predominantly carbon (~85%), with the OC/EC ratio varying between 1.17 and 11.5. Particles were primarily spherical nanoparticles (50–100 nm) capable of deep penetration into the human respiratory tract (HRT). This is the first systematic characterisation of biomass cooking emissions in authentic rural kitchen settings, linking particle morphology, chemistry and toxicology at health-relevant scales. Toxic heavy metals like Cr, Pb, Cd, Zn, and Hg were detected in PM, while ash was dominated by crustal elements such as Ca, Mg and P. VOCs comprised benzene derivatives, esters, ethers, ketones, tetramethysilanes (TMS), and nitrogen-, phosphorus- and sulphur-containing compounds. This research showcases a unique collection technique that gathered particles indicative of their potential for penetration and deposition in the HRT. Impact stems from the close link between the physico-chemical properties of particle emissions and their environmental and epidemiological effects. By providing a critical evidence base for exposure modelling, risk assessment and clean cooking interventions, this study delivers internationally significant insights. Our methodological innovation, capturing respirable nanoparticles under real-world conditions, offers a transferable framework for indoor air quality research across low- and middle-income countries. The findings therefore advance both fundamental understanding of combustion-derived nanoparticle behaviour and practical knowledge to inform public health, environmental policy, and the UN Sustainable Development Goals. Full article

Background: Aortic stenosis (AS) is a prevalent acquired heart valve disease with increasing incidence, particularly among older adults. Gender-specific differences in AS presentation, comorbidities, and outcomes remain underexplored, necessitating further investigation to optimize personalized treatment strategies. Objective: To evaluate the clinical and demographic characteristics, comorbidities, and survival outcomes of patients with AS, stratified by gender and aortic valve morphology. Methods: A retrospective analysis of 145,454 echocardiographic examinations (2009–2018) at the Federal State Budgetary Institution “V.A. Almazov National Medical Research Centre” identified 84,851 patients meeting the inclusion criteria (Vmax ≥ 2.0 m/s, age ≥ 18 years). Patients were stratified by gender and valve morphology (bicuspid aortic valve [BAV] vs. tricuspid aortic valve [TAV]). Survival was assessed in 475 pts with AS over a 16-year period (2009–2025) using Kaplan–Meier analysis. Statistical comparisons utilized STATISTICA v. 10.0, with p-values derived from P-tests. Results: Of the cohort, 4998 men and 6322 women had AS. Men with AS were older (median 64 vs. 57 years, p < 0.0001) and had higher systolic blood pressure (140 vs. 130 mmHg, p < 0.0001) than men without AS. Women with AS were also older (median 70 vs. 58 years, p < 0.0001) with higher systolic (140 vs. 130 mmHg, p < 0.0001) and diastolic blood pressure (80 vs. 80 mmHg, p < 0.0001). Men with AS had higher rates of hyperlipidemia (HLP) (26.3% vs. 10.3%, p < 0.0001), while women with AS had increased coronary artery disease (CAD) (35.7% vs. 26.4%, p < 0.0001), diabetes mellitus (DM) (13.4% vs. 10.2%, p < 0.0001), and obesity (10.9% vs. 10.2%, p = 0.06). Chronic heart failure (CHF) was more frequently reported in patients with AS, regardless of gender, compared to patients without AS (in men 53.4% vs. 41.8%, p < 0.0001; in women 54.5% vs. 37.5%, p < 0.0001). BAV was associated with higher AS prevalence (54.5% in men, 66.4% in women). Survival analysis revealed higher mortality. Over the 16-year follow-up period, the mortality rate was 21.7%. Conclusions: Mortality in a representative AS cohort reached 21.7%, underscoring the progressive nature of the disease and its long-term impact. Survival was negatively affected by age over 68.5 years, as well as the presence of aortic regurgitation (AR), increased peak aortic jet velocity, and enlarged maximum aortic diameter. Aortic valve replacement demonstrates an insignificant effect on patient survival rates. Beta-blocker therapy in patients with varying degrees of aortic AS severity has not only demonstrated its safety but has also shown a positive effect on reducing mortality (improving survival). In contrast, the combination of angiotensin II receptor blockers (ARBs) with calcium channel blockers (CCBs) is quite dangerous for patients with AS and reduces their survival. Aortic valve replacement demonstrates an insignificant effect on patient survival rates. In contrast, the absence of fibrinolytic therapy and anticoagulant treatment is associated with an improved prognosis. Conversely, the administration of antiarrhythmic agents and statins is correlated with enhanced survival outcomes, potentially attributable to their influence on coexisting comorbidities. Further research is required to delineate their precise mechanisms and contributions. These results emphasize the importance of early identification, comprehensive risk assessment, and individualized management strategies in improving outcomes for patients with AS. Full article

We fabricated TiO₂ thin films using the sol–gel method, incorporating TiO₂ nanoparticle sizes of 25 nm on the fluorine-doped tin oxide (FTO) substrates by spin coating and annelation at 600 °C. The influence of incorporating TiO₂ particles on the surface morphology, optical properties, and photovoltaic performance of TiO₂ thin-film dye-sensitized solar cells (DSSC) was examined. Structural characterization was analyzed using X-ray diffraction (XRD), while the morphologies were analyzed using scanning electron microscopy (SEM). The transmittance and absorbance of films were measured using an ultraviolet (UV)–visible (VIS)–near-infrared (NIR) spectrophotometer. The current–voltage (I-V) property was evaluated under simulated solar irradiation. The results demonstrated that the incorporation of TiO₂ particles enhanced the efficiency of DSSCs. The photovoltaic performance of DSSCs was improved with TiO₂ nanoparticle incorporation. The optimized DSSC incorporated TiO₂ films (TIFNA). TIFNA achieved a Jsc of 14.49 mA/cm², Voc of 0.69 V, fill factor of 60.5%, and efficiency of 6.05%, compared to 4.23% for the DSSC with unincorporated TiO₂ thin film. The improved performance was attributed to increased dye adsorption, better crystallinity, and enhanced electron transport. Full article

This work presents the synthesis and application of magnetic Fe₃O₄ nanoparticles supported on baobab seed-derived biochar (Fe₃O₄/BSB) for removing Congo red (CR) dye from aqueous solutions through an oxidative process. The biochar support offered a porous structure with a surface area of 85.6 m²/g, facilitating uniform dispersion of Fe₃O₄ nanoparticles and efficient oxidative activity. Fourier-transform infrared (FT–IR) spectroscopy analysis confirmed surface fictionalization after Fe₃O₄ incorporation, while scanning electron microscopy (SEM) images revealed a rough, porous morphology with well-dispersed nanoparticles. Thermogravimetric analysis (TGA) demonstrated enhanced thermal stability, with Fe₃O₄/BSB retaining ~40% of its mass at 600 °C compared to ~15–20% for raw baobab seeds. Batch experiments indicated that operational factors such as pH, nanoparticles dosage, and initial dye concentration significantly affected removal efficiency. Optimal CR removal (94.2%) was achieved at pH 4, attributed to stronger electrostatic interactions, whereas efficiency declined from 94.1% to 82.8% as the initial dye concentration increased from 10 to 80 mg/L. Kinetic studies showed that the pseudo-second-order model accurately described the oxidative degradation process. Reusability tests confirmed good stability, with removal efficiency decreasing only from 92.6% to 80.7% after four consecutive cycles. Overall, Fe₃O₄/BSB proves to be a thermally stable, magnetically recoverable, and sustainable catalyst system for treating dye-contaminated wastewater. Full article

Calcium aluminate cement (CAC) offers rapid strength development, chemical durability in harsh environments, and high-temperature resistance, but its long-term performance may be compromised by the conversion of metastable hexagonal hydrates into stable cubic phases. Concurrently, recycling spent fluorescent lamp glass (SFLG) is limited because of its residual mercury content. This study investigates the use of manually (MAN) and mechanically (MEC) processed SFLG as partial CAC replacements (up to 50 wt.%). Both SFLG types had irregular morphologies with mean particle sizes of ~20 µm and mercury concentrations of 3140 ± 61 ppb (MAN) and 2133 ± 119 ppb (MEC). Moreover, the addition of SFLG reduced the initial and final setting times, whilst MEC waste notably extended the plastic state duration from 20 min (reference) to 69 min (50 wt.% MEC). Furthermore, strength development was accelerated, with SFLG/CAC mortars reaching peak strengths at 7–10 days versus 28 days as in the CAC reference. CAC and 15 wt.% SFLG mortars showed strength loss over time by reason of their phase conversion, whereas mortars with 25–50 wt.% SFLG experienced significant long-term strength gains, reaching ~60 MPa (25 wt.%) and ~45 MPa (35 wt.%), respectively, after 365 days, with strength activity indexes (SAI) near 90% and 70%, respectively. These improvements are attributed to the formation of strätlingite (C₂ASH₈), which stabilized hexagonal CAH₁₀ and mitigated conversion to cubic katoite (C₃AH₆). Mercury leaching remained below 0.01 mg/kg dry matter for all mixes and curing ages, classifying the mortars as non-hazardous and inert under Spanish Royal Decree 646/2020. The results suggest that SFLG can be safely reused as a sustainable admixture in CAC systems, enhancing long-term mechanical performance while minimizing environmental impact. Full article

Oxide dispersion-strengthened (ODS) alloys are regarded as one of the most promising materials for Generation IV nuclear fission systems, owing to their exceptional attributes such as high strength, corrosion resistance, and irradiation tolerance. The traditional methods for fabricating oxide dispersion-strengthened (ODS) alloys are both time-consuming and costly. In contrast, additive manufacturing (AM) technologies enable precise control over material composition and geometric structure at the nanoscale, thereby enhancing the mechanical properties of components while reducing their weight. This novel approach offers significant advantages over conventional techniques, including reduced production costs, improved manufacturing efficiency, and more uniform distribution of oxide nanoparticles. This review begins by summarizing the state of the art in Fe-based and Ni-based ODS alloys fabricated via traditional routes. Subsequently, it examines recent progress in the AM of ODS alloys, including Fe-based, Ni-based, high-entropy alloys, and medium-entropy alloys, using powder bed fusion (PBF), directed energy deposition (DED), and wire arc additive manufacturing (WAAM). The microstructural characteristics, including oxide particle distribution, grain morphology, and alloy properties, are discussed in the context of different AM processes. Finally, critical challenges and future research directions for laser-based AM of ODS alloys are highlighted. Full article

This study presents a comprehensive investigation of a novel graphene oxide/zinc oxide/lignin (GO/ZnO/lignin) nanocomposite for the photocatalytic degradation of methylene blue (MB) and gentian violet (also known as crystal violet, CV) dyes in aqueous solutions. The nanocomposite was synthesized through a hydrothermal method and thoroughly characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). FTIR spectra confirmed the successful incorporation of functional groups from all components, while XRD patterns revealed a well-crystallized structure with characteristic peaks. SEM micrographs showed a uniform, hierarchical morphology and EDX analysis verified the elemental composition and distribution. Under ultraviolet (UV) irradiation, the nanocomposite exhibited remarkable photocatalytic degradation efficiency (~97%) for both MB and CV. Key operational parameters were systematically evaluated, including pH (2–10), catalyst dosage (0.005–0.04 g/20 mL), and initial dye concentration (10–20 ppm). Optimal performance was achieved at pH 10, with a catalyst dosage of 0.03–0.04 g/20 mL and lower dye concentrations. The enhanced photocatalytic activity can be attributed to the synergistic effects coming from GO’s electron transport capabilities, ZnO’s strong photocatalytic activity and lignin’s additional degradation sites. Furthermore, the nanocomposite demonstrated excellent reusability, retaining nearly 60% of its degradation capacity after four cycles, outperforming its individual components. These results highlight the potential of this composite material for sustainable wastewater treatment applications. Full article