Search Results (263)

This study investigates the effects and mechanisms of three mineral admixtures—fly ash (FA), silica fume (SF), and metakaolin (MK)—on the fresh, mechanical, and microstructural properties of Yellow River sediment (YRS)-based shotcrete. A comprehensive experimental program was conducted, including setting time determination, workability assessment, and mechanical strength evaluation, complemented by microstructural characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results indicate that the incorporation of FA prolonged initial and final setting times and improved pumpability but reduced build-up thickness and compressive strength; splitting tensile strength at later ages remained comparable to the control. SF shortened the final setting time and reduced flowability but enhanced shootability, layer build-up, and medium- to later-age compressive and tensile strengths, with an optimal dosage of 5%. MK accelerated the final setting time, slightly reduced early-age compressive strength, but improved early-age splitting tensile strength and achieved 28-day compressive strength comparable to the control. Microstructural analyses revealed that FA participates in pozzolanic reactions forming C–(A)–S–H gel, while SF and MK promote the formation of dense C–S–H and carboalumination phases, enhancing matrix densification. Based on performance evaluation, the recommended dosages are FA ≤ 20%, SF ≤ 15%, and MK ≤ 15%. These results establish clear links between macroscopic performance and microstructural evolution, providing experimental guidance for the sustainable development of YRS-based shotcrete. Full article

This study extends beyond traditional single-binder assessments by developing a mechanistic framework for interpreting the behavior of multi-component geopolymer systems. It systematically examines the roles of industrial by-products (granulated blast-furnace slag), agricultural residues (barley straw ash), and construction-derived materials (recycled granite powder) when integrated into a metakaolin-based matrix, with particular emphasis on their influence on gel formation pathways, microstructural refinement, and macroscopic performance. A sustainable geopolymer concrete (SGC) system was formulated using multi-binder combinations at replacement levels ranging from 5% to 30%. Comprehensive evaluations were conducted, including fresh properties, mechanical performance, durability characteristics, thermal resistance, and microstructural features. The results demonstrate that the 70Mk–30GBFS composition facilitates the development of a dense hybrid C–(A)–S–H/N–A–S–H gel network, resulting in a 26.8% enhancement in compressive strength and a 32.0% decrease in chloride ion penetration. Rather than depending on empirical relationships, the study establishes a mechanistically grounded link between precursor chemistry, interfacial transition zone (ITZ) refinement, and performance limits. These findings contribute to a deeper understanding of multi-component geopolymer design and support the development of high-performance, sustainable concrete materials for structural applications. Full article

Background: Osteoporosis is a major skeletal disorder, particularly affecting postmenopausal women. Young ovariectomized rat models are commonly used to investigate estrogen deficiency-related skeletal changes, although they do not fully reproduce osteoporosis in a mature postmenopausal skeleton. Established pharmacological therapies remain the cornerstone of osteoporosis management, while nutritional factors continue to be investigated for their potential supportive role in bone metabolism. Menaquinone-7 (MK-7), a form of vitamin K2, has been investigated for potential skeletal effects through vitamin k-dependent mechanisms, particularly osteocalcin carboxylation. The aim of this study was to evaluate the dose-dependent effects of MK-7 on bone turnover markers, femoral mechanical resistance, qualitative histological findings, and hepatic safety in a young ovariectomized rat model. Methods: Forty female Wistar rats that were 8 weeks old, and thus still undergoing skeletal maturation, were assigned to four groups: sham-operated controls, ovariectomized controls, ovariectomized rats treated with low-dose MK-7, and ovariectomized rats treated with high-dose MK-7. Treatment was administered every 48 h for 12 weeks. At study completion, 35 rats survived; standardized analysis included eight animals per group. Plasma bone turnover markers (BTMs) and alanine aminotransferase were measured, femoral strength was assessed by the three-point bending test, and bone and liver histology was analyzed. Results: Biomechanical testing showed that high-dose MK-7 was associated with greater femoral mechanical resistance compared with untreated ovariectomized rats, while qualitative histology suggested differences in cortical architecture among groups. Biochemically, MK-7 treatment reduced undercarboxylated osteocalcin, suggesting vitamin K-dependent target engagement, whereas conventional turnover markers showed discordant findings. Overall, hepatic architecture was preserved, although mild hepatocellular apoptosis was observed. Conclusions: In this young OVX rat model, high-dose MK-7 was associated with improved femoral mechanical resistance compared with untreated OVX controls. However, because ovariectomy was performed during skeletal maturation, these findings should be interpreted as preliminary and cannot be directly extrapolated to established postmenopausal osteoporosis in a mature skeleton, and further studies are needed to clarify its activity pathways and safety profile. Full article

This study presents a sustainable strategy to address the inherent limitations of metakaolin (MK)-based geopolymers—specifically their water sensitivity, high permeability, efflorescence, and susceptibility to corrosion—arising from their calcium-deficient composition. To mitigate these issues, calcium hydroxide (Ca(OH)₂ or CH) was incorporated into MK mixtures at dosages ranging from 1% to 15%. The influence of CH on mechanical and durability performance was evaluated under both air and water curing conditions. The results show that although a higher CH content reduced flowability and accelerated setting, it markedly enhanced compressive strength, water resistance, and corrosion protection. CH addition also effectively suppressed efflorescence and refined the transport properties of the geopolymer matrix. These improvements are attributed to the formation of C-(A)-S-H gel, which densified the microstructure and strengthened the overall matrix. Electrochemical assessments further confirmed the enhanced corrosion resistance of embedded steel reinforcement. Collectively, the findings demonstrate that CH supplementation is an effective approach for improving the performance and long-term durability of MK-based geopolymers, broadening their potential for structural and environmental applications. Full article

To enhance the utilization of industrial coal gangue, response surface methodology was used to optimize the concrete mix proportions based on three key factors: the mass ratio of fly ash (FA) to metakaolin (MK) (A), the combined dosage of FA and MK (B), and the water-to-binder ratio (C). A quadratic regression model was established, and the optimal mixture was characterized using FT-IR, XRD, and SEM. The model exhibited high statistical significance (p < 0.001) and an excellent fit (R² > 0.95), confirming its predictive reliability. Single-factor analysis revealed that the order of influence on 28 d compressive strength was C > A > B, indicating that the water-to-binder ratio had the most significant effect on later-age strength. The optimal mix proportions were determined as follows: fly ash-to-MK ratio of 0.65, admixture dosage of 20% by mass of total binder, and C of 0.475. Under these conditions, the measured 28 d compressive strength reached 35.9 MPa, which was within 5% of the model-predicted value, thereby validating the model’s accuracy. Microstructural analysis demonstrated that the appropriate incorporation of FA and MK promoted the formation of C-S-H gel, refined the pore structure, and improved the quality of the interfacial transition zone, which collectively enhanced the mechanical performance. A systematic understanding of the strength and microstructural mechanisms of concrete incorporating coal gangue, fly ash, and metakaolin is currently lacking, which hinders the design of more robust and durable structures. This study addresses this gap by systematically clarifying the individual and combined effects of the key variables on the strength of coal gangue concrete. The findings reveal the underlying mechanisms, providing a scientific basis for the sustainable, large-scale application of coal gangue concrete in construction. Full article

The study aimed to develop a mucoadhesive thermosensitive buccal gel capable of forming an artificial clot after application in the extraction socket and providing prolonged release for metronidazole (MZ) and ibuprofen (IB). The critical quality attributes of the product were systematically evaluated using Ishikawa (cause–effect) diagrams as a risk assessment tool, considering the factors related to the formulation, process, and methodology. Subsequently, Failure Mode and Effects Analysis (FMEA) was used to identify the critical parameters of the formulation and process characterized by a high probability of occurrence and a significant impact on product performance. The influence of qualitative and quantitative formulation variables was further investigated using two experimental designs, applied for both screening and optimization purposes. The rheological, adhesion, and in vitro release properties of the drugs were studied, and the optimized formulation for these characteristics contains Poloxamer 407 20.99% and HPMC K100M:K4M 1:1, 0.74%. The release of MZ and IB was prolonged over 8 h and followed Peppas’s kinetics. The optimized formula had an appropriate pH and an acceptable ex vivo mucoadhesion time. Stability studies revealed the preservation of mechanical properties and a recovery coefficient for MZ and IB of over 90%, after 12 months of storage. The optimized formula may be a potential candidate for the prevention of alveolar osteitis. Full article

Amylase enzyme catalyzes the breakdown of starch by acting on the α-1,4 glycosidic bond. The use of amylases is common in areas such as baking and fruit juice production in the food industry, as well as in the detergent, textile, and paper industries. Due to their broad industrial applicability, the recombinant production of amylases has received increasing attention in recent years. In this study, the production of Aspergillus niger α-amylase enzyme was investigated for the first time in Pichia pastoris under the control of the ethanol-inducible synthetic ADH2 (SNT5) promoter. A codon-optimized A. niger α-amylase gene was expressed extracellularly in the P. pastoris MK115-PDI strain. Optimal production conditions were 24 °C and pH 6.0. In a 5 L bioreactor, total secreted protein reached 2.2 g/L and enzyme activity reached 44,062 U/mL. The recombinant enzyme was characterized and showed optimal activity at 60 °C and pH 7. In apple juice assays, the enzyme hydrolyzed starch and demonstrated suitability for juice clarification, although performance depended on enzyme concentration. Overall, these results indicate that the SNT5 synthetic promoter enables efficient recombinant α-amylase production in P. pastoris and represents a promising alternative to conventional promoter systems for industrial enzyme manufacturing. Full article

This study investigates the effect of metakaolin (MK) as a partial replacement of cement (CEM I) in high-workability mortars, with emphasis on fresh-state behaviour, mechanical properties, microstructural development, and carbon footprint implications. Mortars were produced with MK replacement levels ranging from 0 to 50% by mass of binder, under a constant water-to-binder ratio and fixed superplasticiser amount. Fresh-state results showed that increasing MK content reduced flowability due to its high fineness; however, high workability was maintained for replacement levels up to 20%. At 28 days, MK replacement up to 10% retains approximately 90–95% of the control compressive and flexural strength, whereas higher replacement levels lead to gradual strength reductions (to ~55–60% at 50% MK), despite comparable early-age strength gains across all mixes. Durability-related indicators demonstrated reduced water absorption and capillary uptake at moderate MK contents (approximately 20–30%), indicating refined pore structure and reduced pore connectivity. Microstructural analyses using SEM, TGA, and XRD confirmed effective portlandite consumption and the formation of dense C–A–S–H-type hydration products at moderate MK replacement levels, whereas excessive MK contents resulted in unreacted MK. A comparative carbon footprint assessment showed that MK incorporation leads to proportional reductions in embodied CO₂ emissions, with replacement levels of 10–20% providing the most favourable balance between mechanical performance, durability, and environmental benefit. Therefore, the results demonstrate that MK can be used as a supplementary cementitious material for producing low-carbon, high-workability mortars. Full article

This study investigated the biochemical composition and antioxidant potential of flours from pigment-deficient Chlorella vulgaris variants (honey and white) and wild-type (green) and the impact of lactic acid bacteria–yeast co-culture fermentation. The three variants were characterized for composition, total polyphenol (TPC) and flavonoid (TFC) contents, antioxidant capacity (DPPH, FRAP, and ORAC assays), and reactive oxygen species production in HT-29 intestinal cells. All extracts were noncytotoxic up to 100 µg/mL. Among all variants, the green showed the highest native TPC, TFC, and overall antioxidant activity. TPC and TFC were similar between honey and white, while FRAP was higher in honey and ORAC was higher in white. Biomasses were subsequently fermented for 24 h using Lactiplantibacillus plantarum CR L1 or Levilactobacillus brevis L204 with either Saccharomyces cerevisiae TRE Y100 or Kluyveromyces marxianus MK Y55. Fermentation resulted in significant pH reduction and increases in titratable acidity and lactic acid production, particularly in co-cultures involving K. marxianus. However, the effects on antioxidant properties were strongly matrix-dependent, with significant increases in TPC and antioxidant activity observed only in the white variant. Overall, pigmentation and microbial pairing emerged as key determinants of metabolic outcomes. These findings highlight the potential of co-culture fermentation to enhance the bioactive profile of pigment-deficient C. vulgaris, supporting their application in functional foods. Full article

Type 2 diabetes (T2D) features insulin resistance that promotes cerebrovascular injury, yet the immune signals linking metabolic stress to vascular dysfunction remain unclear. We tested the hypothesis that insulin resistance and soluble vascular cell adhesion molecule-1 (sVCAM1) act through complementary pathways in mast cells (MCs) to raise circulating histamine levels and impair cerebral vascular function. In a high-fat diet (HFD) plus low-dose streptozotocin (STZ) model, plasma histamine rose sharply after the onset of insulin resistance and remained elevated. Plasma sVCAM1 levels also increased after insulin resistance. In vitro, recombinant sVCAM1 upregulated histidine decarboxylase (HDC) in native MCs in a dose-dependent manner, indicating a shift toward histamine synthesis, but did not enhance degranulation. In contrast, pharmacological inhibition of Akt with MK2206 activated Glycogen Synthase Kinase 3 beta (GSK3β) and increased MC degranulation without affecting HDC expression. Diabetic endothelial cell monolayers exhibited a ~twofold reduction in transendothelial electrical resistance consistent with impaired blood–brain barrier (BBB) integrity. Diabetic cerebral arteries showed receptor remodeling that favored constriction with histamine H1 receptor (H1R) expression increasing in vascular smooth muscle, while endothelial H1R and histamine H2 receptor (H2R) decreased. Functionally, insulin treatment lowered HOMA2-IR in T2D mice but did not restore cerebral artery myogenic tone or improve stroke outcomes after distal middle cerebral artery occlusion (dMCAO). Neutralizing VCAM1 with a monoclonal antibody reduced circulating sVCAM1 and histamine levels, and, together with the GSK3β inhibitor Tideglusib, stabilized MCs, normalized cerebral artery tone, and reduced post-MCAO infarct size and edema. These findings identify two distinct yet complementary mast cell pathways in T2D, highlight an immune-vascular interface that drives cerebrovascular dysfunction, and propose sVCAM1 blockade plus GSK3β inhibition as rational strategies to protect cerebral vascular function in the diabetic brain. Full article

Adiabatic demagnetization refrigeration (ADR) has attracted considerable attention as an effective approach to reach ultra-low temperatures required for fundamental physics and quantum technologies. Here we directly characterize the cryogenic magnetocaloric performance of the rare-earth-based double-perovskite oxide Gd₂CuTiO₆ (GCTO) through quasi-adiabatic demagnetization measurements. Magnetization measurements show no long-range magnetic transition above 1.8 K and indicate dominant antiferromagnetic (AFM) interactions, consistent with an AFM ordering temperature of $T_{\mathrm{N}}\approx 1.15$ K reported previously. Notably, the isothermal magnetization $M\left(H\right)$ at 1.8 K deviates from an ideal single-ion Brillouin response and is better described by a molecular-field correction for the Gd sublattice, suggesting correlated paramagnetism persisting above $T_{\mathrm{N}}$. In contrast to previous studies that inferred cooling performance from thermodynamic estimates, we directly validate the achievable sub-Kelvin cooling in GCTO through quasi-adiabatic measurements. In the quasi-ADR process starting from $T_0$∼2 K, demagnetization fields of 4, 6, and 9 T yield minimum temperatures of $T_{\min }=761.5$, 452.4, and 289.2 mK, respectively, well below $T_{\mathrm{N}}$. After complete removal of the magnetic field, the sample temperature remains highly stable for at least several tens of minutes, demonstrating a long hold time under quasi-adiabatic conditions. Moreover, the $T\left(H\right)$ curves reveal a characteristic field scale around $H_{\mathrm{c}}$∼1 T, implying a field-induced modification of the low-temperature magnetic-entropy landscape that is relevant to the cooling behavior during demagnetization. These results highlight GCTO as a promising magnetic refrigerant for sub-Kelvin ADR applications and underscore the role of correlated magnetism in optimizing cryogenic magnetocaloric performance. Full article

The rising environmental burden of Portland cement production has intensified the demand for eco-friendly binders that support sustainable construction. This study investigates the development and performance of eco-friendly self-compacting geopolymer concrete (SCGC) produced from industrial by-products, including fly ash (FA), ground granulated blast furnace slag (GGBFS), silica fume (SF), metakaolin (MK), and glass waste powder (GWP). Twenty-one binder formulations were evaluated for fresh-state workability, mechanical performance, durability, and microstructural characteristics under different curing regimes. Fresh properties were assessed using slump flow, V-funnel, L-box, and J-ring tests, while hardened-state evaluations included compressive and flexural strength, Young’s modulus, and water absorption. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were performed on selected mixes to examine microstructural features and crystalline phase development. Results highlight a strong dependency of SCGC performance on binder composition and curing conditions. Mixes rich in GGBFS and SF demonstrated superior mechanical and durability performance, achieving compressive strengths of up to 102.4 MPa under water curing and 107.6 MPa under heat curing, along with negligible water absorption, reflecting a dense and well-developed gel matrix. SEM micrographs confirmed homogeneous, compact microstructures in high-performing mixes, while XRD analysis revealed broad amorphous humps indicative of well-formed N-A-S-H and C-A-S-H gel phases with minimal crystalline residues. In contrast, FA-dominant mixes displayed delayed strength development, and MK-GWP-rich systems exhibited higher porosity and reduced strength. This study underscores the significance of precursor synergy, optimized curing strategies, and microstructural refinement in tailoring SCGC for high-performance, durable, and low-carbon applications in sustainable construction with values ranged from 38.64 GPa (Mix 21) to 25.04 GPa (Mix 19) at 28 days. Stiffer mixes corresponded to denser matrices containing GGBFS and silica fume, whereas lower values were linked to weaker bonding and higher porosity. Full article

This study evaluates the spatiotemporal variations in surface water quality in An Giang province, a key upstream region of the Vietnamese Mekong Delta (VMD), under the influence of hydrological alterations and climate change impacts. Water quality data from 2010 to 2023 were collected from 10 monitoring stations along the Tien and Hau Rivers, focusing on key parameters including pH, temperature, Dissolved Oxygen (DO), Total Suspended Solids (TSS), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Ammonium (N-NH₄⁺), Nitrate (NO₃⁻), orthophosphate (P-PO₄³⁻), and Coliforms. The Mann–Kendall test and Sen’s slope estimator were employed to detect long-term trends and quantify the magnitude of changes. The findings indicated that the Hau River exhibits significant organic pollution, evidenced by elevated levels of BOD and COD, alongside diminished levels of DO. The Tien River exhibits elevated concentrations of NH₄⁺ and total suspended solids (TSS). The MK test indicated that BOD, COD, and NH₄⁺ levels were increasing at most locations in a statistically significant manner. This indicates that the water quality deteriorated over time. The study revealed that the majority of pollutants exhibited statistically significant increasing trends (p ≤ 0.05). The Tien River’s COD is increasing by 1.6 mg/L annually, whereas the Hau River’s COD is escalating by 1.7 mg/L per year. The biochemical oxygen demand on both rivers is increasing by 0.5 mg/L each year. The diminishing quantities of dissolved oxygen indicated a decline in water quality. Pollutant concentrations demonstrated significant positive associations with maximum temperature (r = 0.47–0.64) and hours of sunshine (r ≈ 0.50–0.64). A significant negative correlation with river discharge was observed, particularly during the dry season (r = −0.79 to −0.88), when diminished flows resulted in elevated pollution concentrations. The findings offer measurable evidence that increasing temperatures and decreasing river flows significantly affect water quality, underscoring the necessity of adapting water resource management in the Mekong Delta. Full article

A novel bacterial strain, designated as 4-30^T, was isolated from a soil sample collected from the Kubuqi Desert in Inner Mongolia, northern China. The isolate was a Gram-stain-positive, aerobic, motile, and coccus-shaped bacterium, and its colonies were circular, opaque, convex, smooth, and orange-pigmented on Luria–Bertani agar. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain 4-30^T belonged to the genus Planococcus. Growth occurred at 4–38 °C (optimum, 25–28 °C), pH 6.0–11.0 (optimum, pH 9.0), and in 0–10% (w/v) NaCl (optimum, 1%). Strain 4-30^T contained iso-C_14:0, anteiso-C_15:0, C_16:1 ω7c alcohol, and iso-C_16:0 as major cellular fatty acids (>10%) and MK-7 and MK-8 as predominant menaquinones. Its polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and two unidentified polar lipids. The genomic DNA G+C content was 45.9%. The average nucleotide identity (ANI) values between strain 4-30^T and the closely related species were relatively low (ANIm < 85.6%, ANIb < 82.9% and OrthoANIu < 83.3%), and the digital DNA–DNA hybridization (dDDH) between strain 4-30^T and type strains of the genus Planococcus were 20.0–26.7%. Based on phylogenetic, genotypic, chemotaxonomic, and phenotypic analyses, strain 4-30^T is considered to represent a novel species of the genus Planococcus, for which the name Planococcus circulans sp. nov. is proposed. The type strain is 4-30^T (=CDMCC 1.2409^T = KCTC 43405^T). Full article

This study focuses on the development of sustainable construction materials via geopolymers synthesized from metakaolin and slag, aiming to identify environmentally friendly alternatives for construction material systems. A metakaolin–slag geopolymer mortar (MK–slag) was prepared using metakaolin and slag as fully solid waste raw materials, with sodium silicate solution and sodium hydroxide acting as composite activators. Initially, single-factor experiments were conducted to determine the optimal ranges for metakaolin–slag content, water/binder ratio, and water glass modulus. Subsequently, response surface methodology was employed to develop regression equations that analyze the main and interaction effects of these variables on the 7-day and 28-day compressive strength and water absorption of the mortar. The optimal mix ratio was then identified. The microstructure and formation mechanisms of MK–slag mortar were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP). The results indicate that all factors follow quadratic polynomial relationships with the response variables, showing a regression coefficient (R²) greater than 0.98, indicating an excellent model fit and prediction accuracy. According to model predictions, the optimal mix parameters under multi-objective optimization were found to be a metakaolin-to-slag ratio of 45%: 55%, a water/binder ratio of 0.45, and a water glass modulus of 1.3. After 28 days of curing, the primary hydration products were gel-like substances such as N-A-S-H and C-A-S-H. These gels interweave and overlap to form a high-density, structurally robust binary solid waste geopolymer mortar. This approach expands the application of solid waste materials, such as metakaolin and slag, while enhancing the recycling and utilization efficiency of these waste products. Full article