Search Results (169)

The analytical investigations of 3-miktoarm star (3-arm $\mu$-star) copolymers of type $A_{2}B$ and $A{B}_2$ are performed in the framework of mean-field approximation and Flory–Huggins theory. The total entropy of mixing and the Helmholtz free energy of interaction are calculated for the number $N_A$ monomers of type A and number $N_B$ monomers of type B, respectively. The results confirm that the Helmholtz free energy of miktoarm star copolymers differs from that of polymer blends. The temperature dependence of the Helmholtz free energy allowed us to construct a phase diagram of the solution of miktoarm star copolymers, showing regions of stability, instability, and metastability. The analytical results confirm that a miktoarm star copolymer is not merely a mixture of different homo-arm star polymers and are consistent with a previous investigation performed by liquid chromatography under the critical conditions. Moreover, we performed molecular dynamics simulations of a dilute solution of 3-miktoarm star copolymer of type $A_{2}B$ with a certain number of beads (300 + 300 + 200 + 1) and star copolymer of type $A{B}_2$ with number of beads (300 + 200 + 200 + 1), accordingly. The calculations of the radius of gyration and monomer density profiles of the 3-miktoarm star copolymers of type $A_{2}B$ and $A{B}_2$ in confined geometry of two repulsive surfaces (Dirichlet–Dirichlet boundary conditions) and one repulsive and other one attractive surface (Dirichlet–Neumann boundary conditions) by molecular dynamics simulations are performed. The obtained analytical and numerical results indicate that a dilute solution of miktoarm star copolymers can be used in biotechnology and medicine for drug and gene transmission as well as for the production of new functional materials. Full article

The corrosion behavior and time-dependent mechanism of 22MnB5 steel featuring a thinned Al-Si coating (60 g/m²) were systematically investigated in a chloride ion wet–dry cyclic environment, motivated by the demand for thinning and toughening development of aluminum-silicon coatings. A periodic immersion accelerated corrosion test using 3.5% NaCl solution was conducted, together with macro/microscopic morphology observation (SEM/EDS), phase analysis (XRD, FTIR), and electrochemical measurements (polarization curves, EIS). The Al-Si coated steel was studied over corrosion periods of 1, 8, 10, and 20 days to elucidate its corrosion behavior, interfacial evolution, and failure mechanism. The results indicated that the corrosion process exhibited a three-stage evolution: stable protection, rapid failure, and dynamic equilibrium. At the initial stage (1 day), a dense Al₂O₃ passive film formed on the coating surface, providing excellent substrate protection, with a corrosion current density of only 1.77 µA/cm² and a maximum charge-transfer resistance (R₂) of 652 Ω·cm². In the middle stage (8 days), Cl⁻ permeated through the cracked film, triggering selective dissolution of Al, while Si was enriched in situ to form a porous residual layer; the corrosion current density (I_corr) sharply increased to 13.25 µA/cm², and R₂ dropped to its minimum of 156.6 Ω·cm². Corrosion products at this stage were mainly Al₂O₃ and SiO₂, accompanied by small amounts of iron oxyhydroxides and hydroxides, and local coating failure began to appear. During the later stage (10–20 days), the corrosion products evolved into γ-FeOOH, α-FeOOH, and Fe₂O₃, which, together with an amorphous SiO₂ gel network enriched at the interface, formed a dual-layer composite rust layer. R2 consequently recovered from 156.6 Ω·cm² at 8 days to 424 Ω·cm² at 20 days, indicating a reduced corrosion rate and entry into a stable inhibition stage. The critical failure mechanism is that Cl⁻ preferentially penetrates the surface of the Al₂O₃ passive film, disrupting the metastable state of the coating and thereby creating pathways for corrosive media intrusion. The findings of this study can provide technical support for the safe application of such as-received coatings in non-load-bearing components with heat and corrosion resistance requirements. Full article

To accelerate the transition to sustainable energy, efficient methods for CO₂-free hydrogen production and carbon utilization are needed. This study presents a new, sustainable approach for the simultaneous production of hydrogen, valuable hydrocarbons, and functional carbon materials by converting methane in low-pressure microwave plasma. Compared to traditional methane reforming methods (such as steam reforming), our plasma-based process operates at low temperatures, eliminates direct CO₂ emissions, and enables the conversion of methane into three valuable products: (1) environmentally friendly hydrogen for fuel cells and energy storage systems, (2) a range of valuable organic products (C₂H₂, C₂H₄, C₂H₆), and (3) functional carbon films with self-improving catalytic properties. Optical emission spectroscopy (OES) and the Langmuir double probe method were used for plasma diagnostics, revealing an increase in the concentration of active species (CH, Hα, C₂) and electron temperature upon argon addition. The structure, morphology, and impurity composition of the deposited films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Gas-phase byproducts were analyzed using gas chromatography–mass spectrometry (GC-MS). Argon addition at an Ar/CH₄ ratio of 1 leads to the formation of carbon films with a more ordered structure, as confirmed by XRD data, and improved surface morphology. It was established that argon, by effectively participating in the excitation and dissociation processes of methane molecules through energy transfer from metastable states and increased electron temperature, optimizes plasma–chemical reactions, promoting the deposition of higher-quality carbon coatings. Full article

Biochar (BC)-activated peracetic acid (PAA)-based advanced oxidation processes (AOPs) were increasingly considered as cost-efficient and eco-friendly water treatment technologies for the removal of organic pollutants. However, the specific role of intrinsic carbon, nitrogen species and structure properties played in activation mechanism is still vague. In this study, the waste tea residues-based biochar (WTBC) was prepared by thermal carbonization and applied to activate PAA for the degradation of bisphenol A (BPA). The product carbonized at 800 °C (WTBC800) possessed larger specific surface area (342.57 m²/g), more abundant porous structure and massive defects state (I_D/I_G = 3.53), and exhibited a superior activation performance with 83.7% BPA removal within 120 min. Adsorption and non-radical oxidation pathways [e.g., the mediated electron transfer process (ETP) and singlet oxygen (¹O₂) generation] were evidenced to play the dominant roles in the BPA degradation through the formation of metastable complex WTBC-PAA*. The graphitic carbon, functional nitrogen species, defects structure and persistent free radicals (PFRs) in WTBC were proposed to contribute to the activation of PAA. Overall, relatively higher dosages of WTBC (0–0.5 g/L) and PAA (0–1.5 mM) facilitated the BPA degradation. The solution pH and water matrix (e.g., Cl⁻, NO₃⁻, HCO₃⁻ and SO₄²⁻) presented a negligible effect on the BPA degradation in WTBC/PAA system. This study not only proposes a sustainable approach for organic pollutants removal in wastewater, but also promotes the resource re-utilization of agricultural waste. Full article

Electrocatalytic H₂O₂ production via the two-electron oxygen reduction reaction (ORR) is a highly sustainable alternative to industrial methods. To further optimize non-noble catalysts, we report an interfacial engineering strategy to stabilize the metastable P6₃/mmc-La₂O₃ phase on SrTiO₃. This symmetry evolution from the low-symmetry $\mathrm{P}\stackrel{\mathrm{-}}{3}\mathrm{m}1$ (trigonal) to the high-symmetry P6₃/mmc (hexagonal) space group yields a composite with >95% H₂O₂ selectivity. Mechanistic studies demonstrate that the symmetry-regulated interface optimizes *OOH conversion and suppresses O–O bond cleavage. This work offers a robust design principle for high-performance, noble-metal-free H₂O₂ electrosynthesis. Full article

Food safety sampling inspections are critical for risk prevention in complex supply chains, yet the extremely low frequency of high-risk samples poses substantial challenges for accurate risk prediction. To address the limitations of conventional machine learning models under severe class imbalance, this study proposes a unified Bagging–Stacking framework that integrates stacking ensembles, bagging, and SMOTE–Tomek hybrid resampling to enhance minority-class detection in food safety risk prediction. The stacking ensemble serves as the core of the framework, combining five tree-based base learners with Logistic Regression as the meta-learner to enhance classification robustness. Balanced bootstrap subsets generated through bagging and SMOTE–Tomek hybrid resampling further improve minority-class representation, while a probability-based threshold optimization mechanism is incorporated to refine high-risk classification. Experiments on real-world inspection data show that the proposed framework substantially improves high-risk recall while simultaneously increasing precision, yielding the highest F1 among all compared models. It also maintains a stable overall performance across varying test set proportions, demonstrating strong robustness and consistent generalization under varying evaluation conditions. SHAP analysis identifies storage conditions, production month, shelf life, package, and food category as key contributors to risk prediction, aligning with established mechanisms of food safety risk formation. Overall, the proposed framework provides accurate, robust, and interpretable support for food safety risk prediction, offering practical value for proactive risk prevention and more efficient regulatory resource allocation. Full article

This study investigated how increased Cr and Ni contents affect the corrosion behavior and rust layer evolution of HRB500 rebar in chloride-containing environments. Corrosion of the Cr- and Ni-alloyed rebars was characterized by distinct stages: in the initial stage, before a stable rust layer formed, the corrosion rate increased; with continued immersion, corrosion products progressively covered the surface and became more compact, and the overall corrosion rate decreased. Higher Cr and Ni contents were found to mitigate overall corrosion damage, markedly suppress localized corrosion, and shift the corrosion morphology toward a more uniform attack. Electrochemical measurements showed a noble shift in corrosion potential, a reduction in corrosion current density, and significant increases in low-frequency impedance and charge transfer resistance, indicating enhanced barrier properties against charge transfer and ionic migration. With corrosion progression, rust layer phases evolved from an Fe₃O₄-dominated assemblage to enrichment in stable iron oxyhydroxides; the fraction of α-FeOOH increased, raising the α/γ* index and suggesting improved rust layer stability and protectiveness. Mechanistically, Cr and Ni enrichment was found to facilitate the conversion of metastable products to α-FeOOH and to promote the formation of compact spinel oxides FeCr₂O₄ and NiFe₂O₄, thereby hindering chloride ion ingress and interfacial corrosion reactions and markedly improving corrosion resistance. Overall, this work elucidated the Cr–Ni co-alloying mechanism for rust layer stabilization and pitting suppression. At 504 h, the high Cr–Ni rebar reduced the maximum pit depth by approximately 61.8% and lowered i_corr to approximately 43% of that of the low Cr–Ni rebar, thereby providing quantitative guidance for marine-grade rebar design. Full article

Antisolvent crystallization is a promising method for recovering rare earth elements (REEs). While it offers high theoretical yields of Y₂(SO₄)₃·nH₂O from aqueous leach solutions, the recovery is constrained by kinetic limitations. This study examined the crystallization of Y₂(SO₄)₃·nH₂O in a fluidized bed reactor (FBR) using ethanol, focusing on the effects of the organic-to-aqueous (O/A) ratio and flow rates on yield and crystal properties. O/A ratios of 0.9 and 1.1 were investigated with an initial Y³⁺ concentration of 0.87 g/L and a crystallization time of 3 h. The system exhibits multiple rate-limiting steps. At low O/A ratios (0.9), extended induction times indicate either nucleation rate-limitations despite high supersaturation or the possible formation of an initial metastable phase, requiring extended crystallization time for near-equilibrium yields. At high O/A (1.1), elevated supersaturation accelerates nucleation and achieves ~82% yield in 3 h; however, crystal growth exhibited a remaining rate limitation. Lower supersaturation and slower mixing at O/A = 0.9 favored growth, producing crystals with D50 > 34 µm. This work explores how operational parameters influence crystallization behavior while achieving practical yields and acceptable crystal characteristics within a reasonable timeframe. The FBR provided controlled operation, enabling consistent product formation and process flexibility. Full article

Background: Cefepime/enmetazobactam (FEP/META) is a novel fixed-dose β-lactam/β-lactamase inhibitor combination. The objective was to study the physicochemical stability of the approved daily dose in polypropylene syringes and elastomeric devices over a 24 or 72 h period to understand the feasibility of using FEP/META in prolonged infusions and its use for outpatient parenteral antibiotic therapy (OPAT). Methods: Solutions of FEP/META were prepared in 0.9% NaCl or 5% dextrose (D5W) and stored in syringes (6 g/1.5 g/48 mL) or silicone and polyisoprene elastomeric devices (EDs) at 6 g/1.5 g/120 mL and 6 g/1.5 g/240 mL: syringes were tested at 22–25 °C over a 24 h period, polyisoprene EDs at 2–8 °C over 72 h period, and silicone and polyisoprene EDs at 32 °C over a 24 h period. The solution was considered stable if it retained more than 90% of its initial concentration (Ci), no pH variation (±1 unit), no significant visual change, and with compliant subvisual examination. Liquid Chromatography–Electrospray Ionization–Quadrupole Time-of-Flight–Mass Spectrometry was utilized to identify intermediate degradation products. Results: At the daily dose, FEP/META retained >90% of its Ci up to 12 h in 0.9% NaCl and 24 h in D5W when stored in syringes. In silicone ED, stability was enhanced up to 24 h in D5W at all concentrations. The solution was chemically stable for 24 h when stored in polyisoprene ED in 0.9% NaCl at 2–8 °C. Conclusions: FEP/META combination showed prolonged stability with physicochemical integrity up to 12–24 h in all containers and conditions. It appears to be stable for prolonged infusions and for OPAT. Full article

The performance of cement adhesive in large-tonnage insulators is crucial for determining their structural stability and service life when subjected to long-term electromechanical loading and complex environmental interactions. This work addresses the issue of late-stage strength reduction in alumina cement by employing a rapid steam curing process. The influence of curing temperature on the phase composition and microstructure of the hydration products is investigated, along with the evolution over time of the mechanical properties, dry shrinkage rate and elastic modulus. These findings are further validated through thermal–mechanical performance testing of bonded insulators. The results demonstrate that: (1) The hydration products of the adhesive are significantly influenced by steam curing temperature: the metastable phase CAH₁₀ forms at 20 °C; it transforms into the metastable phase C₂AH₈ at 50–60 °C; it changes to the stable phase C₃AH₆ at 70 °C; and microcracks appear and porosity increases at 80–90 °C, although the stable phase C₃AH₆ remains the dominant phase. (2) Alumina cement adhesive prepared via 2 h steam curing at 70 °C exhibited superior properties, with flexural and compressive strengths reaching 14.2 MPa and 112.7 MPa, respectively. After 360 days, flexural strength remained above 12 MPa and compressive strength exceeded 110 MPa. Dry shrinkage was below 0.04%, with an elastic modulus of approximately 49.6 GPa. (3) Microstructural analysis revealed that the hydration products of the cured adhesive were predominantly C₃AH₆ and AH₃, exhibiting stable structures. After 90 days, porosity decreased to 3.56%, with the C₃AH₆ and AH₃ gels tightly enveloping the aggregates and forming a dense, three-dimensional network structure. (4) All bonded insulators successfully passed thermomechanical performance tests. Therefore, this work can provide a good way to prepare a high-performance cement adhesive for insulators. Full article

Additive manufacturing (AM) of titanium alloys enables the production of complex, high-performance components, but the steep thermal gradients and rapid solidification involved make it challenging to control crystallographic texture and phase evolution. This review synthesizes the current understanding of how these thermal conditions influence grain morphology, texture intensity, and solid-state transformations in key alloys such as Ti-6Al-4V (Ti64), Ti-6Al-2Sn-4Zr-2Mo (Ti6242), Ti-5Al-5Mo-5V-3Cr (Ti5553), and metastable β-Ti systems processed by powder bed fusion-based processes (PBF) such as laser powder bed fusion (LPBF) and electron beam powder bed fusion (EBPBF/EBM). Emphasis is placed on mechanisms governing epitaxial columnar β-grain growth, α′ martensite formation, and the development of heterogeneous α/β distributions. The impact of processing variables on texture development and transformation kinetics is critically examined, alongside phase fractions. Across studies, AM-induced textures are consistently linked to mechanical anisotropy, with performance strongly dependent on build direction and alloy chemistry. Post-processing strategies, including tailored heat treatments and hot isostatic pressing (HIP), show clear potential to modify grain structure, reduce texture intensity, and stabilize desirable phase balances in titanium alloys. These insights highlight the emerging ability to deliberately engineer microstructures for reliable, application-specific properties in powder-based AM titanium alloys. Full article

The use of recycled aggregate provides clear environmental advantages but may introduce chemical interactions that influence cement hydration, particularly when the material originates from mining by-products containing heavy metals. This study examines cementitious composites containing different volume fractions of recycled aggregate derived from Pb–Zn mine tailings and identifies the mechanisms responsible for the observed early-age hydration delay. The recycled aggregate was characterized using XRD, hydration was monitored through ultrasonic pulse velocity (UPV) and temperature evolution, mechanical performance was assessed at 1, 3, and 7 days, and phase evolution was interpreted using SEM-EDS and thermodynamic equilibrium modeling (GEMS/Cemdata18). The results show that heavy-metal-bearing phases (Zn-, Pb-, and Fe-sulfides/sulfates) promote the formation of metastable metal–silicate complexes, temporarily lowering the oxidation potential and delaying setting by up to 28 h in mixtures containing 100% recycled aggregate. Early-age strength was substantially reduced; however, by day 7, all mixtures except that with 100% recycled aggregate approached the strength of the reference mixtures with natural aggregate. Despite these effects, recycled aggregate can be safely incorporated at replacement levels up to 25 vol.%, which preserves acceptable fresh and hardened properties. Nevertheless, the presence of persistent sulfate-bearing phases (e.g., epsomite, anglesite) indicates a potential for long-term sulfate release and associated durability risks, warranting further investigation. Full article

Li₃PO₄ is an ideal precursor for synthesizing high-performance LiFePO₄, as it simultaneously provides lithium and phosphorus sources. Extremely low solubility of Li₃PO₄ enables efficient lithium recovery from low-concentration Li-rich brine by reactive crystallization. A focused beam reflectance measurement (FBRM) system was employed to monitor the key optimization parameters for Li₃PO₄ crystallization, supersolubility, and metastable zone widths (MSZWs). The optimized process parameters were determined by systematically investigating the effects of operating conditions. Additionally, prediction of supersolubility and MSZWs was accomplished with theoretical models. Results demonstrate that both supersolubility and MSZWs exhibit a pronounced negative correlation with temperature. Supersolubility decreased sharply when LiCl concentration exceeded 5 mol·L⁻¹ or Na₃PO₄ concentration surpassed 0.8 mol·L⁻¹. Conversely, it increased exponentially with Na₃PO₄ feeding rate. The effect of impurity (NaCl/KCl) was non-monotonic, initially increasing and then decreasing supersolubility and MSZWs. Among these, Na₂B₄O₇ most significantly enhanced both parameters, followed by Na₂SO₄. The supersolubility data were well-fitted by an empirical equation (R² > 0.99). For MSZWs prediction, the self-consistent Nývlt-like model (R² > 0.9883) and the modified Sangwal’s model (R² > 0.994) achieved superior performance. Collectively, these findings establish a theoretical basis for optimizing lithium recovery via Li₃PO₄ crystallization, facilitating more efficient and sustainable production of high-purity lithium products. Full article

Background: Type 2 diabetes mellitus (T2DM) is increasingly recognized as affecting not only the retina but also the ocular surface. Chronic hyperglycemia can disrupt meibomian gland function, reduce tear secretion, and impair corneal sensitivity, leading to tear film instability and symptoms of dry eye disease. However, previous studies have reported variable findings, and the extent of these alterations remains uncertain. Methods: Following PRISMA guidelines, this systematic review and meta-analysis evaluated observational studies that compared tear film parameters between adults with T2DM and non-diabetic controls. Eligible studies assessed one or more of the following: invasive or non-invasive tear break-up time, Schirmer test, tear meniscus height, or Ocular Surface Disease Index (OSDI). Results: Twenty-four studies involving approximately 3500 eyes were included. Most reported significantly reduced tear stability and secretion in diabetic participants compared with controls. Tear break-up times were consistently shorter in T2DM, indicating a less stable tear film. Schirmer test results demonstrated lower tear production correlated with diabetes duration and poor glycemic control. Tear meniscus height was modestly reduced in T2DM, reflecting decreased tear reservoir volume. Subjective symptoms, as measured by OSDI, were generally higher among patients with T2DM, suggesting greater ocular surface discomfort. Conclusions: T2DM is strongly associated with tear film instability, reduced tear secretion, and increased dry eye symptoms. These findings suggest that diabetic care should include routine ocular surface assessment and highlight the need for standardized, longitudinal investigations. Full article

Grassland ecosystems play a key role in global carbon and nutrient cycling, yet their productivity is increasingly affected by changing climate, land use, and nutrient inputs. Recent studies have identified plant–microbe interactions as a crucial biological mechanism regulating these changes. However, comprehensive research across different biomes remains insufficient. This review focuses on the functional characteristics and physiological processes of microorganisms to explore how they influence grassland productivity and stability in the context of global change, and proposes quantifiable indicators to improve model predictions. By integrating evidence from alpine, temperate, and arid grasslands, we summarize how microbial carbon use efficiency(CUE), nutrient cycling enzyme activity, and symbiotic capabilities affect plant nutrient acquisition, carbon allocation, and stress resistance. Meta-analytical data indicate that microbial processes can explain a substantial proportion of productivity variation beyond climatic and edaphic factors. We further outline methodological progress in linking molecular mechanisms with ecosystem dynamics through multi-omics, stable isotope tracing, and structural equation modeling. This synthesis highlights that incorporating microbial mechanisms into grassland productivity frameworks enhances predictive accuracy and provides an empirical basis for sustainable management. Across global grasslands, microbial processes account for roughly 40–50% of the explained variance in productivity beyond abiotic drivers, underscoring their predictive value in ecosystem models. Thes study underscores the broader significance of recognizing soil microbes as active drivers of ecosystem function, offering a biological foundation for carbon sequestration and grassland restoration strategies under global environmental change. Full article