Search Results (1,015)

The effect of reversible addition–fragmentation chain transfer (RAFT) polymerization on the structure, morphology, and thermal degradation behavior of polypropylene glycol maleate–acrylic acid copolymers (p-PGM:AA) was investigated using 2-cyano-2-propyl dodecyl trithiocarbonate (CPDT) as the RAFT agent. Copolymers synthesized at different CPDT concentrations were characterized by ¹H/¹³C NMR spectroscopy, gel permeation chromatography (GPC), transmission electron microscopy (TEM), thermogravimetric analysis coupled with mass spectrometry (TG–MS), isoconversional kinetic methods, and density functional theory (DFT) calculations. ¹H NMR spectroscopy revealed a progressive decrease in the relative intensity of vinyl proton signals with increasing CPDT concentration, indicating enhanced conversion of unsaturated fragments during copolymerization. Alkaline hydrolysis followed by ¹H NMR and GPC analysis of the degradation products confirmed cleavage of polyester segments and yielded low-molecular-weight fragments with M_n = 1370 g mol⁻¹ and narrow dispersity (Đ = 1.035), providing additional information on the architecture of the vinyl-polymerized segments. Increasing CPDT concentration resulted in lower molecular weights and narrower molecular weight distributions of the soluble copolymer fractions. TEM analysis demonstrated broader domain size distributions and increased morphological heterogeneity in RAFT-modified samples, accompanied by an increase in swelling degree. Thermogravimetric analysis showed that RAFT-modified systems undergo multi-stage thermal degradation with the appearance of an additional low-temperature stage associated with thermolabile fragments. TG–MS revealed earlier evolution of CO₂ and oxygen-containing species and changes in the distribution of volatile products. DFT calculations indicated a decrease in the HOMO–LUMO energy gap and suggested the participation of RAFT-derived fragments in the energetic characteristics of decarboxylation processes. Isoconversional and nonlinear kinetic analyses demonstrated increased kinetic heterogeneity for branched copolymer s synthesized at elevated CPDT concentrations, whereas cross-linked systems exhibited more uniform degradation behavior. The combined experimental and theoretical results demonstrate that RAFT polymerization provides an effective route for tuning the macromolecular architecture, morphology, and thermal degradation pathways of p-PGM:AA copolymers. Full article

Chlorinated benzoquinones such as 2,6-dichlorobenzoquinone (DCBQ) are toxic disinfection by-products that may persist in treated waters, requiring post-treatment strategies. In this study, the photo-Fenton process was evaluated for DCBQ degradation, with a focus on the influence of pH on kinetics, oxidation behavior, and water quality evolution. Experiments were conducted using 50.0 mg/L DCBQ, 1.0 mg/L Fe²⁺, and 2.0 mM H₂O₂ under UV irradiation (150 W) within a pH range of 3.0–12.0. Degradation followed apparent second-order kinetics, with maximum rates at acidic pH. At initial pH 3.0–5.0, rapid pollutant removal was accompanied by efficient aromaticity (UV₂₅₄) and color elimination, intense dissolved oxygen consumption, transient turbidity peaks due to intermediate formation, and increases in total dissolved solids, indicating extensive oxidation and a high degree of organic matter transformation, as inferred from indirect physicochemical indicators. At near-neutral pH, oxidation was slower, with delayed aromatic and chromophoric decay and moderate accumulation of intermediates. Mildly alkaline conditions exhibited limited radical activity, stable turbidity, and reduced mineralization. Under strongly alkaline conditions, oxidation was largely inhibited, with persistent aromaticity and negligible oxygen consumption. These findings highlight the importance of integrating advanced oxidation processes with adsorption-based systems for efficient and sustainable water treatment of emerging contaminants. Full article

Critical-sized bone defects lack spontaneous healing capacity. While mesenchymal stem cell-derived exosomes (sEVs) are promising osteoinductive agents, their rapid in vivo clearance limits their free-form efficacy. Here, we fabricated a nano-hydroxyapatite/chitosan (nHA/CTS) composite scaffold as a protective, sustained-delivery platform for human umbilical cord blood-derived mesenchymal stem cell exosomes (HUCB-MSCs-exos) to accelerate bone repair. The 3D porous CTS/10% nHA scaffold exhibited excellent cytocompatibility and a degradation rate commensurate with new bone ingrowth. Critically, it enabled a biphasic exosome release profile—an initial burst followed by a 14-day sustained release (89.73% cumulative release). In vitro, HUCB-MSCs-exos significantly promoted the proliferation, migration, and osteogenic differentiation of bone marrow-derived MSCs, as demonstrated by enhanced alkaline phosphatase activity and matrix mineralization. In a rabbit condylar defect model (5 mm diameter), the CTS/10% nHA-exo scaffold achieved a 57.44 ± 8.42% healing rate at two months, nearly two-fold greater than the scaffold-only group (29.33 ± 6.94%). Histological and immunohistochemical analyses at two months confirmed the formation of mature, well-vascularized trabecular bone, accompanied by robust expression of late-stage osteogenic markers (OCN and OPN). These findings demonstrate that the CTS/10% nHA scaffold synergistically integrates osteoconductive structural guidance with exosome-mediated osteoinductive paracrine signaling, providing a compelling and translatable strategy for critical-sized bone-defect management. Full article

The integration of photovoltaic (PV) generation with alkaline water electrolyzers (AWE) in DC microgrids offers a highly promising pathway for green hydrogen production. However, the inherent volatility of solar power often induces transient voltage ripples and power surges, degrading the electrolyzer stack and destabilizing the common DC bus. To overcome this, this study proposes a hierarchical multimodal coordinated control strategy tailored for a four-port (PV–Storage–Grid–Hydrogen) DC microgrid. The proposed framework leverages multi-port synergetic coordination among the PV array, battery storage, and grid-interfacing converters to actively buffer extreme power mismatches, thereby ensuring the constant regulation of the DC bus voltage. Through comprehensive time-domain simulations under worst-case step-change boundary conditions, the large-signal transient stability of the proposed strategy is quantitatively verified. Under extreme disturbances, the system successfully confines DC bus voltage deviations to within safe operational boundaries with a rapid settling time, effectively avoiding typical inverter overvoltage trip thresholds. Furthermore, the adaptive power regulation algorithm maintains precise steady-state power tracking. By utilizing a gradient-based flag variable, the system seamlessly transitions between maximum power point tracking (MPPT) and active power-limiting modes, ensuring continuous equipment protection, stable high-purity hydrogen yield, and uninterrupted microgrid stability. Full article

In Chile, Eucalyptus globulus stands out as a significant forest species, yielding around 2 million tonnes of bark; this by-product is a valuable source of phenolic compounds. This research evaluated the valorization of E. globulus bark using alkali-assisted extraction (AAE) and obtained extracts intended to protect the wood against fungal degradation and ultraviolet (UV) radiation. The chemical and thermal properties of the extracts were characterized using total phenolic content (TPC), antioxidant capacity, FTIR spectroscopy, LC-LTQ-Orbitrap-MS, and thermal analyses (TGA and DSC). Pine wood samples were impregnated using the Bethel process, and their absorption, retention, leaching, UV resistance, gloss, and antifungal efficacy were evaluated. The AAE showed an extraction yield of 8.79%, almost double that of aqueous extraction, with a phenolic content of 970 mg GAE/100 g dry bark and good antioxidant capacity. The MS/MS analysis tentatively identified low-molecular-weight organic acids, phenolic acids, a hydrolyzable tannin derivative, ellagic acid, methylated flavonol glycosides, and an iridoid non-phenolic metabolite. Thermal analysis indicated greater stability of the alkaline extracts, with a mass loss of less than 10% up to 200 °C, and significant degradation between 220 and 300 °C. Leaching tests showed a lower release of polyphenols from alkali-treated wood, indicating reduced mobility and/or greater retention of the extractives within the wood structure. Biological assays demonstrated effective inhibition of stain fungi and strong resistance to brown rot. Furthermore, UV aging tests showed less color change (Delta E*) and greater resistance to surface degradation. These results demonstrate the potential of alkaline extracts from E. globulus bark as sustainable additives for wood protection. Full article

This study evaluates the intrinsic osteogenic potential of β-tricalcium phosphate (β-TCP)-containing composite scaffolds (PLCL–TCP, PLGA–TCP, and ZnO–TCP) on chorion-derived mesenchymal stem cells (CMSCs) under non-osteogenic in vitro conditions. CMSCs were cultured on the three biomaterials for 35 days without osteogenic supplements to isolate the material-driven cellular response. Cell viability was assessed via MTT assay, while osteogenesis-associated markers (alkaline phosphatase, type I collagen, and osteocalcin) were quantified using ELISA. Scaffold surface morphology and elemental composition were characterized before and after cultivation utilizing SEM and EDX. All investigated scaffolds supported long-term CMSC viability and induced measurable osteogenic responses. PLCL–TCP demonstrated a consistently strong biological response, characterized by sustained metabolic activity, elevated ALP and COL I production, and increased osteocalcin levels at later stages of cultivation. ZnO–TCP also exhibited favorable osteogenesis-associated responses, particularly with respect to late-stage osteocalcin production, while maintaining high structural stability. In conclusion, β-TCP composites can intrinsically modulate CMSC behavior without biochemical supplements. Osteogenic outcomes depend on a complex interplay of surface chemistry, scaffold architecture, and degradation profiles, with PLCL–TCP demonstrating favorable overall performance among the investigated biomaterials. Full article

Thermal overload in internal combustion engines may progressively destabilize lubricant-film integrity and promote severe tribological deterioration within highly stressed contact interfaces. This study investigates the thermo-tribological degradation sequence of a high-mileage gasoline engine subjected to prolonged idle operation under impaired cooling conditions, ultimately resulting in engine seizure. The investigated engine had accumulated 356,724 km, while the lubricant had remained in service for approximately 26,724 km prior to the experiment. The post-failure investigation combined teardown inspection, geometrical camshaft assessment, reverse gravimetric reconstruction, hydraulic tappet surface profiling, XRF surface characterization, laboratory oil analysis, and SEM/EDS evaluation of wear debris. The results demonstrated strongly localized degradation concentrated primarily within the cam–tappet interfaces. Severe non-uniform camshaft wear was accompanied by pronounced hydraulic tappet surface damage and evidence of unstable boundary-lubrication conditions. Laboratory oil analysis revealed elevated wear-metal concentrations, depletion of the alkaline reserve, increased oxidation indicators, and a final Class D oil condition assessment. SEM/EDS characterization identified Fe-bearing wear debris associated with sustained material removal and debris recirculation during the final degradation stage. The combined evidence supports a coupled thermo-tribological degradation mechanism involving lubricant deterioration, boundary-lubrication instability, adhesive wear acceleration, oxidative surface degradation, and debris-assisted surface damage preceding final engine seizure. The present case study provides experimentally documented evidence of lubrication collapse under real-engine thermal runaway conditions and highlights the critical role of lubricant condition in maintaining tribological stability under severe thermal loading. Full article

This research examines the hydrothermal corrosion behaviour of ceramic matrix composites (CMCs) under highly alkaline conditions (pH > 11.5) in the framework of a deep geological repository for high-level radioactive waste (HLW). The study focuses on the degradation of alumina powder and fibres, key constituents of an oxide/oxide CMC material. Accelerated ageing experiments were conducted in a highly alkaline aqueous environment (pH > 11.5, T = 70 °C for 220 days and T = 150 °C for 30 days). The research used a cross-disciplinary approach integrating thermodynamic calculations and physicochemical analyses to determine the degradation mechanisms of alumina powder and fibres induced by contact with the aqueous ageing solution. Characterisation of the aged alumina powders and fibres revealed the presence of unaltered alumina, hydrated alumina, amorphous phases, and calcium carbonate precipitates from the aqueous solution. Thermodynamic calculations indicate (1) the hydrolysis of alumina to diaspore and (2) the formation of an aluminosilicate phase and calcium carbonate. However, experimental results reveal kinetic limitations, such as the preferential formation of boehmite over diaspore, and morphology-dependent degradation pathways (protective-layer formation on fibres and partial dissolution of powders). Full article

Glass fiber reinforced epoxy laminates (GFRP) are increasingly used in structural applications where combined mechanical and environmental loading is unavoidable, such as in the aerospace, naval, automotive, and petrochemical industries. This study investigates the influence of aggressive environments on the impact response and damage mechanisms of GFRP laminates. Specimens were immersed in acidic (hydrochloric and sulphuric) and alkaline solutions (sodium hydroxide), oil (automotive engine and automotive brake fluid), and cementitious solutions (cement and metakaolin mortars) for a determined period to simulate severe service conditions. Low-velocity impact tests were subsequently performed to evaluate the residual impact performance in terms of absorbed energy, maximum force, and damage extent. The results demonstrate that environmental exposure significantly alters impact behavior, mainly through matrix plasticization, fiber-matrix interface degradation, and microcrack development. For shorter immersion times (12–30 days), the solutions are not highly aggressive, as the decrease in elastic energy remains below 15%, with cementitious solutions showing the lowest reductions even for longer exposure periods. In contrast, longer immersion times in alkaline solution, DOT4 oil, and metakaolin mortar lead to more severe deterioration, with elastic energy reductions between 30% and 40%, the most aggressive condition being immersion in NaOH for 36 days, which caused a 37.4% decrease. Alkaline and automotive brake fluid oil environments induced the most severe degradation, leading to reduced impact resistance and increased damage propagation. Full article

Sulforaphane (SFN) is an anti-cancer isothiocyanate occurring in Brassicaceae. SFN is decomposed by heat, oxygen, and alkaline conditions. Microencapsulation is a way to improve its stability. This work presents the development of SFN microcapsules using an oil-in-water emulsion with gum arabic (GA) as the wall material for incorporation into yogurt. The process for obtaining SFN microcapsules was optimized using response surface methodology. The optimal microencapsulation conditions were 7 min of stirring, an SFN/GA mass ratio of 0.7, and a surfactant concentration of 7%, resulting in an entrapment efficiency of 90.0 ± 3.0%, the highest reported. The microcapsules had a regular spherical shape with 0.5–5.5 µm diameter and no cracks. Freezing temperature (−4 °C) preserved 100% of SFN in the microcapsule for 90 days. Yogurt added with SFN microcapsules maintained physical and microbiological quality. SFN retention in yogurt after 30 days was 57% when microencapsulated, showing a 14-fold reduction in the kinetic degradation constant compared with free SFN, confirming the efficacy of this method. Full article

Allicin, the most critical bioactive compound of garlic (Allium sativum L.), is of significant industrial importance when extracted at high purity while preserving its structural integrity. In this study, the combined use of supercritical-CO₂ (SC-CO₂) extraction and molecular distillation (MD) techniques was investigated to obtain garlic extracts with high allicin content from Gaziantep (Araban) garlic. The SC-CO₂ extraction process was optimized using Response Surface Methodology (RSM) within a range of 150–300 bar pressure, 50–80% co-solvent concentration and 0.5–3.0 mL/min solvent flow rate. The obtained extracts were characterized by LC-ESI-DAD-MS/MS, and their biological activities were evaluated using a comprehensive in vitro digestion model. Allicin in vitro digestion was performed using models simulating gastrointestinal conditions of young adults (<65 years) and older adults (>65 years), and its bioactive properties were comparatively evaluated. In the antimicrobial analysis, for SC-CO₂, a strong activity was demonstrated against Staphylococcus aureus and Escherichia coli in the oral phase of the in vitro digestion model, with inhibition zones of 36.33 mm and 26.50 mm in young samples and 34.67 mm and 25.83 mm in older samples, respectively. Owing to the immediate nucleophilic attack triggered by the subsequent alkaline pH shift and pancreatic enzymatic stress, free allicin underwent total structural degradation, falling below detectable limits within the intestinal chyme. In terms of purification performance, allicin content increased from 45.77% after SC-CO₂ extraction to 67.10% after molecular distillation. Crucially, due to the immediate nucleophilic attack driven by the subsequent alkaline pH shift and pancreatic enzymatic stress, free allicin underwent complete structural degradation and was rendered strictly undetectable within the intestinal chyme. This approach provides a sustainable and environmentally friendly purification strategy that effectively limits the thermal degradation of allicin. The results present a practical framework for the scalable production of allicin-rich nutraceutical intermediates and functional food ingredients. Full article

Petroleum hydrocarbons contamination in soil is difficult to remediate due to strong adsorption and limited bioavailability. This study investigated the coupled remediation of diesel contamination in an alkaline kaolin-based model substrate using a silica gel-loaded, iron-catalyzed sodium percarbonate composite (SPC^SF) and Bacillus subtilis. The alkaline model substrate was used as a simplified representation of difficult-to-reclaim hydrocarbon- and reagent-impacted matrices that may occur at oil drilling or production sites. In this study, a combined remediation strategy integrating a silica gel-loaded, iron-catalyzed sodium percarbonate composite (SPC^SF) with Bacillus subtilis ATCC 11774 was developed for diesel-contaminated soil. The remediation performance of chemical oxidation, microbial remediation, and their combined application was systematically evaluated. The simultaneous SPC^SF–microbial treatment achieved the highest removal efficiency, reaching 65.1% after 31 d, which was markedly higher than that of chemical oxidation (22.5%) or microbial remediation alone (31.1%). Within the mineral model substrate used in this study, SPC^SF effectively regulated pH and oxidation–reduction potential, creating conditions more favorable for microbial activity. Spectroscopic analyses (three-dimensional fluorescence spectrum, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy) indicated that SPC^SF promoted the transformation of diesel hydrocarbons into bioavailable intermediates, which were further converted by microorganisms into carboxyl-rich organic matter. Bacillus subtilis was associated with a higher Fe(II) proportion in the coupled system, which may have favored maintenance of Fe redox activity and sustained Fenton-like reactivity. However, direct measurements of reactive oxygen species and Fe(II)/Fe(III) dynamics were not performed; therefore, this interpretation should be regarded as a plausible hypothesis based on indirect evidence. The specific microbial contribution to Fe redox transformation was inferred from indirect evidence and may also have been influenced by medium-derived components or microbial metabolites. This study presents a coupled supported sodium percarbonate and microbial remediation strategy providing mechanistic evidence for the compatibility of supported chemical oxidation and microbial degradation in diesel-contaminated soil. Full article

Soil depth and habitat degradation can reshape fungal communities in salt-affected wetlands, but their effects on fungal ecological processes remain insufficiently understood. This study examined soil fungi in the Halahai Provincial Nature Reserve and adjacent converted farmland in the western Songnen Plain, Northeast China, where salt-affected meadow soils correspond mainly to Solonetz. Four habitat types—reed wetland, meadow steppe, degraded Suaeda saline patch, and converted farmland—were sampled at 0–20 cm and 20–40 cm soil depths. Soil properties, fungal diversity, taxonomic composition, environmental associations, niche breadth, assembly processes, and FUNGuild-based trophic modes were analyzed using ITS sequencing. Degraded Suaeda soils showed the strongest salinity–alkalinity stress, with pH values of 10.34–10.30 and electrical conductivity of 1.70–1.75 dS·m⁻¹. Fungal richness was highest in surface-converted farmland, with a Sobs value of 423.33, and lowest in deeper degraded Suaeda soil, with a Sobs value of 86.00. Ascomycota dominated most groups, especially degraded Suaeda soils, where its relative abundance reached 75.29–76.80%. ANOSIM confirmed significant community dissimilarity among habitat-depth groups (R = 0.56878, p = 0.001). Specialists accounted for 68.07% of fungal taxa, and stochastic processes, especially drift and dispersal limitation, contributed substantially to assembly. These results indicate that soil depth, salinity–alkalinity, and habitat conversion jointly regulate fungal community structure and ecological processes in degraded soda saline–alkali wetlands. Full article

Microbial degradation of organic matter is a key driver of iodine enrichment in groundwater. Using stable carbon isotopes (δ¹³C-DIC and δ¹³C-DOC), this study investigates the role of microbial processes and organic matter biodegradation in the formation of high-iodine groundwater downstream of the Kuitun River, China. The groundwater is weakly alkaline and reducing, with Cl⁻ and Na⁺ as the dominant ions, and is mainly slightly saline. I⁻ concentrations range from 51.66 to 552.79 µg/L (mean 177.68 µg/L), with 61.54% of samples classified as high-iodine water. Dissolved inorganic carbon (DIC, 22.97–100.85 mg/L, dominated by HCO₃⁻) originates primarily from microbial degradation of organic matter and silicate weathering. Dissolved organic carbon (DOC, 2.01–4.22 mg/L) is mainly derived from C3 plants. In this reducing, organic-rich aquifer, microbial decomposition of organic matter and reductive dissolution of iron minerals are the primary hydrobiogeochemical processes that release solid-phase iodine into groundwater. The high-iodine groundwater in the study area follows a burial–dissolution genesis model. Full article

Northeast China’s black soil region serves as a critical cornerstone of national food security, yet accelerating soil degradation, characterized by declining soil organic matter (SOM) and rising bulk density (BD), threatens the productive capacity of its farmland. Understanding how soil physicochemical properties regulate crop yields in this ecologically heterogeneous landscape is essential for sustainable agricultural development. Here, 2916 soil samples from 201 counties across six ecological zones were analyzed in conjunction with county-level rice and maize yield records. Our findings revealed that crop yield determinants are fundamentally governed by regional resource endowment characteristics rather than uniform factors. In areas characterized by sandy soil texture, low precipitation (<400 mm yr⁻¹), and inherently low fertility, elevated bulk density (BD, >1.34 g cm⁻³) and alkaline soil conditions (pH > 7.0) constitute the primary constraints to productivity through restricting root development. Conversely, in regions with fertile mollisols and high baseline soil organic matter (SOM > 40 g kg⁻¹), nutrient dynamics emerge as the dominant yield-regulating factors. For volcanic soil landscapes with strong phosphorus fixation capacity, available phosphorus deficiency represents the critical bottleneck for maize production. Path analysis further demonstrates that BD and pH operate predominantly through indirect mechanisms, modulating SOM accumulation and nutrient cycling rather than directly constraining yield. Threshold analysis identified that BD exceeding 1.34 g cm⁻³ and SOM below 26 g kg⁻¹ markedly reduce productivity, while SOM levels above 40 g kg⁻¹ yield diminishing marginal returns. These findings advance our mechanistic understanding and provide scientific foundations for spatially differentiated soil conservation and precision nutrient management strategies essential for sustaining grain production capacity in northeast China’s black soil region. Full article