Search Results (1,344)

Bronze materials are indispensable across numerous industries for enhancing the durability and performance of components, primarily due to their excellent tribological properties, corrosion resistance, and machinability. This study investigates the impact of different atmospheric conditions on the properties of WAAM (wire arc additive manufacturing) cladded bronze coatings on 09G2S steel substrate. Specifically, the research examines how varying atmospheres—including ambient air (N₂/O₂, no shielding gas), pure argon (Ar), carbon dioxide (CO₂), and 82% Ar + 18% CO₂ (Ar/CO₂) mixture—influence coating defectiveness (porosity, cracks, non-uniformity), wettability (manifested as uniform layer formation and strong adhesion), and the extent of intergranular penetration (IGP), leading to the formation of characteristic infiltrated cracks or “bronze whiskers”. Modern investigative techniques such as optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were employed for comprehensive material characterization. Microhardness testing was also carried out to evaluate and confirm the homogeneity of the coating structure. The findings revealed that the bronze coatings primarily consisted of a dominant, highly textured FCC α-Cu phase and a minor BCC α-Fe phase, with Rietveld refinement quantifying a α-Fe volume fraction of ~5%, lattice parameters of a = 0.3616 nm for α-Cu and a = 0.2869 nm for α-Fe, and a modest microstrain of 0.001. The bronze coating deposited under a pure Ar atmosphere exhibited superior performance, characterized by excellent wettability, a uniform, near-defect-free structure with minimal porosity and cracks, and significantly suppressed formation of bronze whiskers, both in quantity and size. Conversely, the coating deposited without a protective atmosphere demonstrated the highest degree of defectiveness, including agglomerated pores and cracks, leading to an uneven interface and extensive whisker growth of varied morphologies. Microhardness tests confirmed that while the Ar-atmosphere coating displayed the lowest hardness (~130 HV_0.1), it maintained consistent values across the entire analyzed area, indicating structural homogeneity. These results underscore the critical role of atmosphere selection in WAAM processing for achieving high-quality bronze coatings with enhanced interfacial integrity and functional performance. Full article

The Qitai silicified wood from Xinjiang, NW China, provides an exceptional archive for investigating the mechanisms of wood silicification. This study applies microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) to characterize the microstructural and mineralogical features of these fossils. The results show that the samples are primarily composed of microcrystalline–macrocrystalline α-quartz having anhedral–euhedral shapes, with minor occurrences of moganite. A well-preserved structure exhibits distinct anatomic details of cellular networks, such as growth rings and rays. Magnified observation revealed that the microcrystalline quartz within cell walls grew outward from the innermost layer of the wall, suggesting silica infiltration from lumina to walls. The opposite growth of elongated columnar quartz within adjacent cell walls terminated at the position of the middle lamellae. Cell lumen infilling exhibits greater variability on filling degree and phase type. The permeation silicification of cell walls and the oligoblastic to polyblastic structure inside cell frameworks contribute to high fidelity preservation. This interpretation helps us understand how the wood structure was perfectly preserved during the silicification, thus emphasizing its significance for wood identification through its preserved structure. Full article

The surface of the Fe40Al5Cr0.2TiB alloy, after oxidation in steam at 700 °C, showed a varied morphology dependent on oxidation time. Initially, a fine, acicular oxide layer formed, which over time transformed into a more compact, lumpy structure corresponding to the α-Al₂O₃ phase. EDS analysis confirmed the dominance of aluminum and oxygen in the oxidation products, and XRD studies revealed the presence of the α-alumina phase. Optical profilometry revealed a significant increase in roughness parameters (R_a and R_z) after long-term exposure (2000 h), which correlates with the thickening and sinterization of the oxide layer. The obtained results indicate that in a water vapor environment, a stable α-Al₂O₃ phase can already be formed at a temperature of 700 °C, and its development leads to increased roughness. Full article

In COVID-19 (coronavirus disease 2019), multi-organ complications depend on the immune system’s activity. α1-Acid glycoprotein (AGP) is a highly glycosylated positive acute-phase protein having multifaceted immunomodulatory and protective effects. We were interested in changes in serum AGP concentrations, expression of its glycans, and oxidation-reduction potential (ORP) between severe COVID-19 patients, convalescents, and healthy controls, and whether any of the analyzed parameters could serve as an additional diagnostic biomarker of severe COVID-19 and/or help monitor recovery. We were also interested in associations between the examined parameters. AGP concentrations were measured using an immunoturbidimetric method. The profile and degree of AGP glycosylation were analyzed using lectin-ELISA with lectins: sialo-specific from Sambucus nigra (SNA) and Maackia amurensis (MAA), fucose-specific from Lotus tetragonolobus (LTA) and Aleuria aurantia (AAL). The static and capacitive ORP (sORP and cORP, respectively) were measured using MiOXSYS C+^® device (Caerus Biotechnologies, Vilnius, Lithuania). Statistica13.3PL software was used for statistical analysis. AGP concentrations increased in COVID-19 patients, showing high clinical usefulness in distinguishing them from convalescents and controls. AGP α2,6-sialylation (reactivity with SNA) was reduced in COVID-19 vs. other study groups, while α2,3-sialylation (reactivity with MAA) was reduced in convalescents vs. controls. The expression of LTA-reactive fucose (Lewis^x structures, Le^x) was reduced in COVID-19 patients compared to controls and convalescents, but AGP reactivity with AAL did not differ between the study groups. The sORP was reduced, and the cORP was increased in COVID-19. The observed negative correlations between sORP and AGP levels may suggest the antioxidant effect of AGP during severe COVID-19. Higher levels of serum AGP in severe COVID-19, together with low expression of sialic acid α2,6-linked and Le^x structures, accompanied by reduced sORP, constitute a characteristic pattern of biomarker expression during severe COVID-19. The increased expression of SNA-reactive sialic acid and Le^x structures may reflect the recovery process after SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection. The observed negative correlations between AGP and sORP levels may suggest that serum AGP in COVID-19 also plays a role as an antioxidative molecule. Full article

Ti-Zr alloys are widely used in medical implants owing to their excellent biocompatibility. However, conventional alloying strategies to improve their performance often increase costs or introduce toxic elements. In this study, oxygen (O), a lightweight, cost-effective, and non-toxic element, was employed to strengthen Ti-Zr alloys. A novel Ti-Zr-O alloy was fabricated via spark plasma sintering (SPS), where the oxygen content was precisely controlled by incorporating TiO₂ powder into the Ti-15Zr base powder. The sintered samples achieved a relative density above 99%, indicating nearly full densification under the optimized SPS conditions. Oxygen addition significantly refined the grain structure, while all O-containing samples maintained a uniform α-Ti phase with random crystal orientation. With increasing oxygen content, the compressive yield strength of the Ti-15Zr alloy increased from 619.24 MPa to 1634.18 MPa, accompanied by a decrease in compressive strain from 50.03% to 31.10%. These results demonstrate that the designed alloy combines superior yield strength with favorable ductility. Furthermore, quantitative analysis of the strengthening mechanisms revealed that oxygen atoms mainly occupy octahedral interstitial sites within the Ti-15Zr matrix, and solid-solution strengthening contributes more significantly than grain refinement. This work provides a promising route for the development of low-cost, high-performance Ti-Zr alloys for biomedical applications. Full article

The current study evaluates the characteristics of electrospun PVDF-based membranes doped with zeolite-A in terms of their structural, morphological, thermal, mechanical, hydrophobic, optoelectrical, and adsorption properties. The effects of the DMF–acetone ratio on solvent and zeolite-doping concentration have been evaluated using SEM-EDX, BET, Raman, XRD, DSC-TGA, UV-VIS spectroscopy, contact angle measurements, and mechanical testing. The membranes prepared with solvents low in acetone and increased zeolite content exhibited a higher crystallinity degree exceeding 50%. Zeolite-enriched membranes have a slightly higher content in the α crystalline phase of PVDF when compared to zeolite-free membranes. Electrospinning processing decreased the sample’s subcooling, improving its thermal stability. Zeolite-doping reduced the band gap energy to 1.3 eV from a maximum of 2.7 eV in PVDF membranes. Membranes doped with 3 or 4 wt.% zeolite exhibit improved load-elongation values at break, reaching up to 4.2 N and 47 mm, respectively, and increased flexibility due to their porous structures and the ratio of crystalline to amorphous phases. The membranes adsorbed an MB equilibrium quantity up to 18.5 mg/g and obeyed the pseudo-second-order (PSO) kinetic model within the first 24 h. Thus, the synergistic effect of zeolite content and solvent ratio can effectively adjust the sample’s structure, texture, and properties. Full article

Brain functional connectivity evolves dynamically during brain development, aging, illness, and cognitive activities. Traditional methods rely on static network snapshots, which do not capture the dynamics of the brain. We propose two new indices: Dynamic Network Similarity (DNS) to measure both temporal and structural dynamic similarity and Dynamic Network Evolution Similarity (DNES) to specifically measure the temporal evolution of dynamic networks. Performance was tested using simulated dynamic networks controlled by four variables (Δφ, λ, α, and β) concerning evolution variations in phase, relative amplitude, noise power, and the span of connectivity strength, respectively. Furthermore, real-world fMRI data from 25 stroke patients pre/post transcranial direct current stimulation (tDCS) rehabilitation were used to test the indices. Patients were randomly sub-grouped into tDCS1 and tDCS2. DNS and DNES thus compared those who received the same therapy (ST: tDCS1 versus tDCS2) and those who received different therapies (DT: tDCS1 versus sham-tDCS). The results showed that DNS was sensitive to all dynamic features, and DNES was primarily sensitive to Δφ and λ. Both indices were able to detect overall difference and capture significantly higher similarity in the ST groups than in the DT groups. Briefly, DNS and DNES appear to be effective tools for studying dynamically evolving brain networks, and may serve as alternatives to traditional static methods. They are particularly useful for analyzing longitudinal neuroimaging data in contexts such as neurodevelopment, aging, and recovery from illness. Full article

In this study, Fe₂O₃–TiO₂ nanocomposites with different TiO₂ contents (1–50%) were synthesized via a solvothermal method using pre-formed α-Fe₂O₃ nanoparticles as cores. We systematically evaluated the influence of TiO₂ loading on the nanocomposites’ structural, morphological, optical, and photocatalytic properties. X-ray diffraction revealed the coexistence of hematite and anatase phases, with an increase in TiO₂ content inducing reduced crystallite size, enhanced dislocation density, and microstrain, indicating interfacial lattice distortion. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) showed a uniform elemental distribution at low TiO₂ contents, evolving into irregular agglomerates at higher loadings. Fourier-transform infrared (FTIR) spectra indicated the suppression of Fe–O vibrations and the appearance of hydroxyl-related bands with TiO₂ enrichment. Diffuse reflectance spectroscopy (DRS) analysis confirmed the simultaneous presence of hematite (~2.0 eV) and anatase (3.2–3.35 eV) absorption edges, with a slight blue shift in the TiO₂ band gap at higher concentrations. Photocatalytic activity, assessed using methylene blue degradation under xenon lamp irradiation, demonstrated a strong dependence on the TiO₂ fraction. The composite containing 33% TiO₂ achieved the best performance, with 98% dye removal and a pseudo-first-order rate constant of 0.045 min⁻¹, outperforming both pure hematite and commercial P25 TiO₂. These results highlight that intermediate TiO₂ content (~33%) provides an optimal balance between structural integrity and photocatalytic efficiency, making Fe₂O₃–TiO₂ heterostructures promising candidates for water purification under simulated solar irradiation. Full article

The labyrinth weir is an effective hydraulic structure, offering high discharge efficiency and economic advantages, making it a suitable option for dam construction or rehabilitation projects. Owing to its complex geometry, significant research efforts have been dedicated to enhancing its hydraulic performance. Since the beginning of this century, Computational Fluid Dynamics (CFD) has emerged as a vital approach, complementing traditional methods in the design of hydraulic structures. This study employs CFD ANSYS FLUENT to examine the discharge coefficient of a semicircular labyrinth weir, featuring a cyclic arrangement and a half-round crest profile. The numerical models and simulations address two-phase flow (air and water) under incompressible and free-surface conditions. The CFD ANSYS FLUENT approach used is multiphase flow modeling using the Volume of Fluid method to track the free water surface. For turbulence effects, it is complemented with the standard k-ε model and the Semi-Implicit Method for Pressure Linked Equations algorithm for pressure–velocity coupling. In addition, for boundary conditions, the flow velocity was defined as the inlet to the channel and atmospheric pressure as the outlet, and the walls of the channel and weir are considered solid, stationary, and non-sliding walls. The model was validated with experimental data reported in the literature. The results indicate that the semicircular labyrinth weir achieves greater discharge capacity when the headwater ratio H_T/P increases for H_T/P ≤ 0.25. A regression analysis mathematical model was also developed, using the H_T/P ratio, to predict the discharge coefficient for 0.05 ≤ H_T/P ≤ 1. Relative to other geometrical configurations, the semicircular labyrinth weir demonstrated a discharge capacity that was up to 88% higher than that of the trapezoidal labyrinth weir. Both weir and cycle efficiency were assessed, and maximum weir efficiency was observed when H_T/P ≤ 0.1, while cycle efficiency peaked at H_T/P ≤ 0.25. The geometric configuration under analysis demonstrated greater economic efficiency by providing a reduced total length and enhanced discharge capacity relative to trapezoidal designs, especially when the sidewall angle α is considered as α ≤ 12°. The study concludes by presenting a design sequence detailing the required concrete volume for construction, which is subsequently compared to the specifications of a trapezoidal labyrinth weir. Full article

Ti65 high-temperature titanium alloy, known for its exceptional high-temperature mechanical properties and oxidation resistance, demonstrates considerable potential for aerospace applications. Nevertheless, conventional manufacturing techniques are often inadequate for achieving high design freedom and fabricating complex geometries. This study presents a systematic investigation into the process optimization, microstructure characterization, and mechanical performance of Ti65 alloy produced by laser powder bed fusion (LPBF). Via meticulously designed single-track, multi-track, and bulk sample experiments, the influences of laser power (P), scanning speed (V), and hatch spacing (h) on molten pool behavior, defect formation, microstructural evolution, and surface roughness were thoroughly examined. The results indicate that under optimized parameters, the specimens attain ultra-high dimensional accuracy, with a near-full density (>99.99%) and reduced surface roughness (Ra = 3.9 ± 1.3 μm). Inadequate energy input (low P or high V) led to lack-of-fusion defects, whereas excessive energy (high P or low V) resulted in keyhole porosity. Microstructural analysis revealed that the rapid solidification inherent to LPBF promotes the formation of fine acicular α′-phase (0.236–0.274 μm), while elevated laser power or reduced scanning speed facilitated the development of coarse lamellar α′-martensite (0.525–0.645 μm). Tensile tests demonstrated that samples produced under the optimized parameters exhibit high ultimate tensile strength (1489 ± 7.5 MPa), yield strength (1278 ± 5.2 MPa), and satisfactory elongation (5.7 ± 0.15%), alongside elevated microhardness (446.7 ± 1.7 HV_0.2). The optimized microstructure thereby enables the simultaneous achievement of high density and superior mechanical properties. The fundamental mechanism is attributed to precise control over volumetric energy density, which governs melt pool mode, defect generation, and solidification kinetics, thereby tailoring the resultant microstructure. This study offers valuable insights into defect suppression, microstructure control, and process optimization for LPBF-fabricated Ti65 alloy, facilitating its application in high-temperature structural components. Full article

TA2 titanium was brazed with a Ti–37.5Zr–15Cu–10Ni filler metal at 860–890 °C for 20 min to investigate the influence of temperature on joint properties. Raising the brazing temperature reduced residual filler in the seam center and transformed the microstructure from heterogeneous phases to a uniform α-(Ti,Zr) solid-solution matrix, accompanied by significant widening of the diffusion layer. At brazing temperatures of 890 °C, the hardness decreased to below 300 HV_0.5 and became more uniform as brittle phases were suppressed. The shear strength reached a maximum of 302 MPa, and the fracture morphology exhibited characteristics of ductile fracture. Micro-electrochemical testing indicated that the joint brazed exhibited an almost uniform current distribution and significantly reduced localized corrosion. Although a small fraction of the Widmanstätten structure was observed at this temperature, it did not impair the overall mechanical performance. These findings demonstrate that a moderate increase in brazing temperature promotes elemental diffusion, alleviates brittle phase enrichment, and markedly enhances the mechanical properties and corrosion resistance of TA2 joints. Full article

Teotihuacan, one of the most significant urban and ceremonial centers of ancient Mesoamerica, was abruptly abandoned in the mid-1st millennium AD. The cause and timing of its collapse—commonly placed between 600 and 650 AD—remain major questions in Mesoamerican archaeology. In this study, we present a new archaeomagnetic investigation of six burned structures distributed along the Street of the Dead, including sites at the Square of the Moon, the Room of Columns, the Northwest Complex of the San Juan River, the Superimposed Buildings, and the West Plaza. Magnetic analyses revealed pseudo-single-domain magnetite as the main remanence carrier and produced well-grouped paleodirections (site-mean declinations ranging from 341.1° to 1.7°, α₉₅ ≤ 3.6°) and reliable absolute paleointensities (ranging from 39.4 ± 3.4 μT to 52.5 ± 5.4 μT), obtained using the Thellier-type double-heating method. Archaeomagnetic dating using both global geomagnetic models (SHAWQ.2k) and regional secular variation curves suggests that the last heating events at these sites occurred between ~400 and 500 AD—well before the traditionally cited Metepec phase (550–650 AD) and the so-called “Great Fire.” These findings challenge the prevailing chronological framework and provide compelling evidence that major episodes of destruction and depopulation may have begun earlier than previously recognized. Full article

Galectin-3 (Gal-3) is a histologic marker of pancreatic cancer and a potential therapeutic target. This study aimed to characterize a novel sulfated agarose-derived oligosaccharide (DP9) from marine algae, Gracilaria lemaneiformis, evaluate its Gal-3 inhibitory activity, and investigate its anti-pancreatic cancer mechanisms. Through controlled acid hydrolysis, a series of odd-numbered oligosaccharides (DP3-11) were obtained, in which DP9 showed the strongest Gal-3 inhibition in hemagglutination assays. Structural analysis confirmed DP9’s unique composition including an alternating β (1→4)-D-galactose and α (1→3)-3,6-anhydro-L-galactose backbone, featuring partial 6-O-methylation on β-D-galactose and 6-O-sulfation on 3,6-anhydro-α-L-galactose residues. Molecular docking revealed DP9’s binding to Gal-3’s carbohydrate recognition domain through key hydrogen bonds (His158, Arg162, Lys176, Asn179 and Arg186) and hydrophobic interactions (Pro117, Asn119, Trp181 and Gly235), with the sulfate group enhancing binding affinity. In vitro studies demonstrated DP9’s selective anti-pancreatic cancer activity against BxPC-3 cells, including inhibition of cell proliferation; S-phase cell cycle arrest; induction of apoptosis; and suppression of migration and invasion. Mechanistically, DP9 attenuated the Gal-3/EGFR/AKT/FOXO3 signaling pathway while showing minimal cytotoxicity to normal cells. This study first demonstrated that agarose-derived odd-numbered oligosaccharides (DP9) can serve as effective Gal-3 inhibitors, which proved its potential as a marine oligosaccharide-based therapeutic agent for pancreatic cancer. Full article

As well as having corrosion resistance and mechanical properties, medical metallic biomaterials used in metal implants must allow imaging by MRI for prognostic diagnosis. Alloys based on Ti, Fe, Co, etc., have the disadvantage that those constituent elements have higher magnetic susceptibility than the tissue surrounding the metallic implant, and this condition results in defects and distortions (“artifacts”) in MR images during MRI imaging. In consideration of this issue, MRI-compatible low-magnetic-susceptibility materials are currently being researched and developed. In this study, microstructural control of Zr-based alloys by alloy design and heat treatment was investigated. The problem with pure Zr is its low corrosion resistance due to the α-phase of its hexagonal-close-packed (HCP) structure. However, alloys that were alloyed and solution heat-treated to a β-phase (body-centered cubic (BCC) structure) showed high corrosion resistance. In particular, when Zr-15Nb-5Ti-3Cr, which has relatively high corrosion resistance, was subjected to aging heat treatment at 673 K for 1.8 ks, precipitation of fine ω-phase in the β-phase was confirmed. The metallographic structure in which the ω-phase precipitated in the β-phase provided high corrosion resistance [≧1000 mV (vs. SHE)] derived from the β-phase, as well as low magnetic susceptibility (approximately 1.2 × 10⁻⁶ cm³/g), due to the effect of the ω-phase. This study provides guidelines for microstructural control to achieve both low magnetic susceptibility and high corrosion resistance in Zr-based metallic biomaterials for medical use. Full article

Ti–6Al–4V (TC4) dual-phase titanium alloy is widely used in aerospace components owing to its excellent strength-to-weight ratio and high-temperature stability. However, conventional machining often generates a wide heat-affected zone (HAZ) and oxide or recast layers, which deteriorate the microstructure and reduce long-term reliability. In this study, the water-jet-guided laser (WJGL) process was applied to investigate how coupled laser–water interactions influence the groove morphology, elemental distribution, and crystallographic evolution of TC4 alloy. Under optimized parameters, the WJGL process reduced the HAZ width to less than 1 $\mathsf{\mu }$m, effectively removed the resolidified layer, and suppressed surface oxidation. SEM, EDS, and EBSD analyses confirmed that the $\alpha$ + $\beta$ dual-phase structure remained stable, with no significant phase transformation or grain coarsening. Compared with conventional laser cutting, WJGL achieved smoother surfaces, improved interfacial integrity, and reduced thermal damage. These findings highlight the potential of WJGL for precision machining of high-performance titanium alloys and provide theoretical and experimental support for enhancing the microstructural control and service reliability of aerospace TC4 components. Full article