Search Results (753)

Alkaline water electrolysis is a widely researched method for hydrogen generation due to its low cost, scalability and its advantage of being able to produce hydrogen using only renewable energy. Enhancing the efficiency of electrolysis systems relies mainly on the development of high-performance ion-conductive membranes. The incorporation of ceramic fillers into polyvinyl alcohol (PVA) membranes as a composite material has shown considerable promise in enhancing the performance of electrolyzers. In this work, novel composite separator membranes for use in alkaline electrolyzers were developed from aqueous PVA solutions and physically crosslinked through a freeze–thawing process. To enhance the membrane properties, two types of ceramic fillers—titanium dioxide (TiO₂) and zirconium dioxide (ZrO₂)—were incorporated into the starting crosslinking solution. The thermal stability of these membranes was studied by a Differential Scanning Calorimetry (DSC) technique where we can conclude that addition of TiO₂ and ZrO₂ significantly influences the thermal properties of PVA membranes. These metal oxides enhance thermal stability, as shown by the shift in exothermic peaks toward higher temperatures and alterations in the degradation mechanism, evidenced by changes in the intensity and number of DSC peaks. The effect is concentration-dependent for TiO₂, where higher contents produce more pronounced yet increasingly complex thermal behavior. Compared with commercial membrane (Zirfon Perl), these types of membranes exhibit better electrochemical performance at ambient temperature and pressure; however, the process of preparation is simpler, reducing the cost of the hydrogen production process. The polarization curves (U-I curves) indicated a decrease in voltage with the addition of an ionic activator based on cobalt and molybdenum. Conductivity measurements performed using electrochemical impedance spectroscopy utilizing a two-probe method revealed that PVA membranes with TiO₂ exhibit ionic conductivity comparable to that of the commercial membrane. Compared to the commercial membrane, these types of membranes demonstrated similar mechanical properties and improved electrochemical performance at ambient temperature and pressure, along with a simplified production process and lower cost of hydrogen production. Full article

To enhance the purification of exhaust gas, a g-C₃N₄/CeO₂/Bi₂O₃ dual type-II heterojunction photocatalysis was designed and prepared to suppress the recombination of electron–hole pairs and improve light energy utilization. The dual type-II heterojunction structure effectively reduced the bandgap (Eg) from 2.5 eV to 2.04 eV, thereby extending the light absorption of photocatalysis into the visible region. Following the design of the heterojunction, a self-cleaning process was developed and applied to asphalt pavement rut plates to evaluate its efficiency in degrading vehicle exhaust under real-road conditions. The coating was systematically characterized in terms of exhaust degradation efficiency, hardness, adhesion, water resistance, freeze–thaw durability, and skid resistance. Under 60 min of natural light irradiation, the purification efficiencies for HC, CO, CO₂, and NO_x reached 22.60%, 19.27%, 14.83%, and 50.01%, respectively. After three-repetition tests, the efficiencies remained high at 21.75%, 19.04%, 14.66%, and 49.83%, demonstrating excellent photocatalytic stability. All other road-performance indicators met the relevant China national standards. The application of this self-cleaning coating in road infrastructure presents a viable strategy for environmental remediation in transportation systems. Full article

Cryopreservation is a key tool in assisted reproduction, but it often compromises post-thaw sperm quality due to cryodamage. Optimizing the initial cooling phase, specifically from room temperature to 5 °C, is a critical determinant of successful outcomes. This study aimed to evaluate the impact of different pre-freeze cooling rates on stallion sperm quality using a novel, precision cooling device. Semen samples from five healthy stallions were divided into three groups and cooled at distinct rates: Slow (0.3 °C/min), Moderate (1 °C/min), and Fast (approximately 30 °C/min). Sperm motility parameters were assessed using a Computer-Assisted Sperm Analyzer (CASA) before freezing and after thawing. Additionally, sperm integrity and physiological parameters, including viability, acrosomal integrity, Reactive Oxygen Species (ROS) expression, and mitochondrial membrane potential, were assessed by flow cytometry post-thaw. The analysis of post-thaw kinematics revealed a significant interaction between the cooling rate and processing stage (post-cooling vs. post-thaw). The Fast-cooling protocol resulted in higher post-thaw total motility (51.8%) compared to the Slow protocol (45.01%). Crucially, no significant differences were detected among cooling rates for the critical parameter of progressive motility or curvilinear velocity (VCL). Circle motility had higher values in the Fast-cooling group compared to the Slow group. Cell viability demonstrated a tendency (p = 0.08), where the Slow cooling group exhibited higher mean values (65.59%) compared to the Fast group (61.67%). Comprehensive flow cytometry assessments of other cellular integrity markers, including acrosomal integrity, mitochondrial function (MMP), and ROS expression, were statistically equivalent across all cooling rates (p > 0.05). The results confirm that this fast pre-freeze cooling rate, integrated within the highly controlled environment of Directional Freezing technology, successfully preserved essential sperm function and structure. Critically, the demonstrated functional equivalence in progressive motility validates the Fast protocol as an efficacious strategy to increase the efficiency and adaptability of equine semen cryopreservation protocols for commercial utilization. Full article

Economic and technological factors necessitate the use of alternative fuels during oil shale combustion, a process that generates substantial amounts of solid waste with varying ash compositions. This study evaluates the potential of two such waste materials: (i) fly ash derived from the combustion of oil shale (a fine particulate residue from burning crushed shale rock, sometimes combined with biomass), and (ii) short carbon fibres recovered from the pyrolysis (a process of decomposing materials at high temperatures in the absence of oxygen) of waste wind turbine blades. Oil shale ash from two different sources was investigated as a partial cement replacement, while recycled short carbon fibres (rCFs) were incorporated to enhance the functional properties of mortar composites. Results showed that carbonate-rich ash promoted the formation of higher amounts of monocarboaluminate (a crystalline hydration product in cement chemistry), leading to a refined pore structure and increased volumes of reaction products—primarily calcium silicate hydrates (C–S–H, critical compounds for cement strength). The findings indicate that the mineralogical composition of the modified binder (the mixture that holds solid particles together in mortar), rather than the fibre content, is the dominant factor in achieving a dense microstructure. This, in turn, enhances resistance to water ingress and improves mechanical performance under long-term hydration and freeze–thaw exposure. Life cycle assessment (LCA, a method to evaluate environmental impacts across a product’s lifespan) further demonstrated that combining complex binders with rCFs can significantly reduce the environmental impacts of cement production, particularly in terms of global warming potential (−4225 kg CO₂ eq), terrestrial ecotoxicity (−1651 kg 1,4-DCB), human non-carcinogenic toxicity (−2280 kg 1,4-DCB), and fossil resource scarcity (−422 kg oil eq). Overall, the integrative use of OSA and rCF presents a sustainable alternative to conventional cement, aligning with principles of waste recovery and reuse, while providing a foundation for the development of next-generation binder systems. Full article

Purpose: Fetal bovine serum (FBS) is widely used in cell culture due to its rich nutrient and growth factor content, but it poses ethical concerns, biosafety risks, and cost limitations. This study investigates plasma-depleted lyophilized (freeze-dried) porcine platelet lysate (pPL) as a potential alternative to FBS for use in cell-based research and biomanufacturing. Materials and Methods: Fresh porcine blood was processed to obtain plasma-depleted pPL using double centrifugation and repeated freeze–thaw cycles. The lysate was analyzed for growth factor content via ELISA, then freeze-dried and sterilized with gamma irradiation. Endotoxin levels and cytotoxicity were evaluated. The ability of plasma-depleted lyophilized pPL to promote cell proliferation was assessed using L929 fibroblast cultures and compared with FBS. Results: Plasma-depleted lyophilized pPL contained significantly higher levels of TGF-β1 than FBS. The freeze-dried product remained stable for at least three months at room temperature. Gamma irradiation effectively sterilized the lysate without degrading key growth factors. Plasma-depleted lyophilized pPL showed no cytotoxicity and promoted greater proliferation of L929 cells compared to FBS, indicating enhanced mitogenic activity. Conclusions: Plasma-depleted lyophilized pPL is a stable, safe, and growth factor-rich alternative to FBS. It supports fibroblast proliferation, retains bioactivity after sterilization and storage, and may provide a scalable, ethical option for cell culture in biomedical research, regenerative medicine, and therapeutic product development. Full article

The source region of the Yellow River on the Tibetan Plateau constitutes a critical ecological security barrier and a key water-conservation region, where permafrost dynamics exercise primary control over ecosystem stability and hydrological processes. Although observations document intensifying freeze–thaw processes under climate warming, the historical and future evolution of maximum freezing depth, abbreviated as MFD, in the source region of the Yellow River remains poorly constrained. Using ground-temperature and meteorological records from 15 stations for 1981–2014, we estimated MFD with a Stefan-type formulation, assessed trend significance using the Mann–Kendall test and Sen’s slope, and characterized changes through 2100 using CMIP6 projections under four shared socioeconomic pathways: SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. We found a strong inverse association between MFD and annual mean ground temperature, such that a 1 °C increase corresponds to an average decrease of approximately 13.2 cm. Historically, MFD has progressively shallowed and exhibits a clear meridional gradient—deeper in the north and shallower in the south; low-value zones declined from 0.75 to 0.50 m, whereas high-value zones decreased from 2.92 to 2.83 m. Across future scenarios, MFD continues to shallow; the strongest signal occurs under SSP5-8.5, yielding an additional decline of approximately 42 percent relative to the historical baseline, with degradation most pronounced at lower elevations. These findings provide actionable guidance for understanding ecohydrological processes and for water resource management in the source region of the Yellow River under climate warming. Full article

As a typical representative of soft capping, primary vegetation capping has both protective and destructive effects on earthen city walls. Addressing its detrimental aspects constitutes the central challenge of this project. Because the integration of MICP technology with plants offered advantages, including soil solidification, erosion resistance, and resilience to dry–wet cycles and freeze–thaw cycles, the application of MICP technology to root–soil composites was proposed as a potential solution. Employing a combined approach of RF-RFE-CV modeling and microscopic imaging on laboratory samples from the Western City Wall of the Jinyang Ancient City in Taiyuan, Shanxi Province, China, key factors and characteristics in the mineralization process of Sporosarcina pasteurii were quantified and observed systematically to define the optimal pathway for enhancing urease activity and calcite yield. The conclusions were as follows. The urease activity of Sporosarcina pasteurii was primarily regulated by three key parameters with bacterial concentration, pH value, and the intensity of urease activity, which required stage-specific dynamic control throughout the growth cycle. Bacterial concentration consistently emerged as a high-importance feature across multiple time points, with peak effectiveness observed at 24 h (1.127). pH value remained a highly influential parameter across several time points, exhibiting maximum impact at around 8 h (1.566). With the intensity of urease activity, pH exerted a pronounced influence during the early cultivation stage, whereas inoculation volume gained increasing importance after 12 h. To achieve maximum urease activity, the use of CASO AGAR Medium 220 and the following optimized culture conditions was recommended: an activation culture time of 27 h, an inoculation age of 16 h, an inoculation volume of 1%, a culture temperature of 32 °C, an initial pH of 8, and an oscillation speed of 170 r/min. Furthermore, to maximize the yield of CaCO₃ in output and the yield of calcite in CaCO₃, the following conditions and procedures were recommended: a ratio of urea concentration to Ca²⁺ concentration of 1 M:1.3 M, using the premix method of Sporosarcina pasteurii, quiescent reaction, undisturbed filtration, and drying at room-temperature in the shade environment. Full article

Existing freeze–thaw cycle tests are based on freeze–thaw cycles under fully constrained conditions, but under natural conditions, the vertical deformation of soil during freeze–thaw cycles is much greater than the lateral deformation. Therefore, to better simulate the freeze–thaw process of shallow soil under natural conditions, a method of preparing specimens is proposed. Specimens with five freeze–thaw cycle gradients, four water content gradients and three dry density gradients were prepared. This method realises the top-unconstrained role of the specimens during freeze–thaw cycles and provides space for vertical deformation. At the same time, it enables the observation of height and surface degradation. Triaxial tests of shallow Ili loess were carried out after indoor freeze–thaw cycles under fixed confining pressure (100 kPa). The results show that surface degradation and vertical deformation of Ili loess without top restraint increase gradually with the number of freeze–thaw cycles; strength decreases gradually and damage morphology changes from shear to bulging. Threshold conditions for the transition from softening to hardening in the strength curve of Ili shallow loess are proposed, as well as damage parameters related to freeze–thaw cycles, water content, and dry density. A coupled damage constitutive model applicable to shallow Ili loess has been established that takes these three factors into account. Full article

Ion exchange resins are commonly utilized for treating liquid radioactive waste within nuclear power plants; however, the disposal of these waste resins presents a new challenge. In this study, magnesium silicate hydrate cement (MSHC) was used to immobilize the waste resin, and the immobilization effectiveness of the MSHC-solidified body were assessed by mechanical properties, durability, and leaching performance. Hydration heat, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electronic microscopy (SEM), and mercury intrusion porosimetry (MIP) were used to study the hydration process of the MSHC-solidified body containing Cs⁺, Sr²⁺, and Cs⁺/Sr²⁺ waste resins. The results demonstrated that the presence of waste resins slightly delayed the hydration reaction process of MSHC and reduced the polymerization degree of the M-S-H gel, and the composition of the hydration products were not changed. The immobilization mechanism for radionuclide ions in resin included both mechanical encapsulation and surface adsorption, and the leaching of Cs⁺ and Sr²⁺ from MSHC-solidified body followed the FRDIM. When the content of the waste resin was 25%, the MSHC-solidified body exhibited satisfactory compressive strength, freeze-thaw resistance, soaking resistance, and impact resistance. These results strongly indicated that MSHC possessed the ability to effectively immobilize ion exchange resins. Full article

In assessing the strength properties of stone materials, especially in historic structures, ultrasonic measurements are widely used as a non-destructive testing (NDT) method. Actual stone degradation in situ is estimated based on various laboratory tests which allow researchers to correlate the number of artificial ageing cycles of stone specimens with ultrasonic wave velocity measured on these specimens. This paper presents the results obtained for granite, marble, limestone, travertine and sandstone which underwent various cyclic ageing tests including freezing and thawing, high temperature and salt crystallization. Analysis of the obtained results shows that, independent of the stone type tested and independent of the ageing test applied, a rate of change in the stone elastic properties is described by an ordinary differential equation whose solution is an exponential law analogue to the Newton’s law of cooling. The degradation function model can be used for further research on expected residual strength and dynamics of the heritage materials degradation processes. Full article

From an agronomic perspective, the most important property of soil aggregates is their stability. The stability of the soil structure can vary greatly, even over a short time. In this context many authors draw attention to the influence that climatic factors have on the stability of aggregates. The process of freeze–thaw cycles (FTC) could result in changes in the aggregates’ stability. The research objective was to determine the effect of alternating freeze–thaw cycles on selected parameters of soil structure in Luvisol depending on the type and duration of action of organic supplementation. Cyclic freeze–thaw (FT) processes significantly modified most of the analysed properties of soil aggregates. This effect was usually not modified by organic supplementation, nor by its duration of action. FT cycles reduced the density of soil aggregates. FT cycles reduced the resistance of soil aggregates to dynamic and static water action. Despite the lower resistance to the destructive action of water, the decomposition of primary aggregates resulted in a more favourable size distribution of secondary aggregates in aggregates subjected to FT cycles. The research objective was to determine the effect of alternating freeze–thaw cycles on selected parameters of soil structure in Luvisol depending on the type and duration of action of organic supplementation. Full article

Global warming has intensified freeze–thaw activity in high-latitude and high-altitude regions; along the western sector of the farming–pastoral ecotone in northern China, pronounced seasonal freeze–thaw cycles now pose a severe threat to land resources. This study aims to quantitatively reveal the spatial differentiation patterns of freeze–thaw erosion in the western segment and its influencing factors. This study begins with the fundamental concepts of freeze–thaw erosion, grounded in soil mechanical fragmentation and gravitational migration. Critical slope is used as the identification criterion to delineate freeze–thaw erosion zones. Building upon this foundation, a Random Forest model is employed to calculate the weighting factors influencing freeze–thaw erosion in the western segment of the northern agro-pastoral transition zone, thereby constructing a graded evaluation model for freeze–thaw erosion intensity. Results indicate the following: (1) Freeze–thaw erosion exhibits no discernible distribution pattern in the western segment, appearing scattered, while non-freeze–thaw erosion is primarily concentrated in the northern region. (2) Freeze–thaw erosion intensity ranges from 1.48 to 4.58 in the western segment. The total area of the study region is 151,000 km², the affected area spans 122,400 km², accounting for 81.11% of the total regional area. (3) Regionally, the Hehuang Valley exhibits predominantly strong and severe erosion, while the northern Loess Plateau shows mostly slight erosion. The southern Loess Plateau features light and moderate erosion with scattered instances of severe erosion. (4) Vegetation coverage and soil moisture are the primary contributing factors to freeze–thaw erosion. This study proposes, for the first time, a method that couples annual freeze–thaw day cycles with a critical slope threshold to delineate freeze–thaw erosion zones, demonstrating broad applicability. It systematically uncovers the spatial heterogeneity of freeze–thaw erosion in the western sector, substantially advancing scientific understanding of the process and providing a theoretical basis for its targeted management. Full article

To investigate the variations in the strength of cement-improved soft clay under artificial freeze–thaw action, laboratory freeze–thaw and unconfined compressive strength tests were conducted on specimens with different cement dosages, initial moisture contents, and curing ages. The strength changes and damage patterns of the soil were quantitatively analyzed before and after the freeze–thaw process. The results indicated that while a higher cement content and longer curing ages enhanced strength, they also promoted a more brittle failure mode. Conversely, freeze–thaw action was found to weaken this brittleness, enhance ductility, and lead to significant strength deterioration. The strength was also observed to decrease with increasing moisture content. A strength growth rate (η) was introduced to quantify these changes, revealing that freeze–thaw cycles consistently suppressed the strength growth capacity. Based on the above-mentioned influencing factors, a strength prediction model for cement-improved soft clay that undergoes freeze–thaw cycles was developed. In water-rich areas, the research results can provide a reference for the changes in the strength of cement-improved soft clay under artificial freeze–thaw cycles. Full article

In situ physical coal fracturing is one of the key technologies for deep coal resource extraction, among which the liquid nitrogen cyclic freeze–thaw (LNCFT) technique demonstrates remarkable fracturing effects and promising application potential in physical coal breaking. To determine economically viable mining and coalbed methane (CBM) extraction cycles, this study builds on previous research and conducts a series of experiments to investigate the effects of different cold condition temperatures and freeze–thaw cycles on the mesoscopic surface structure and macroscopic mechanical properties of deep, water-rich coal-rock samples. A statistical damage constitutive model for saturated coal-rock under coupled freeze–thaw and loading, incorporating a damage threshold, was established to more accurately describe the damage patterns and mechanisms. The results indicate that lower cold condition temperatures lead to greater mesoscopic crack propagation, lower uniaxial compressive strength, and significantly reduced freeze–thaw failure cycles. Under −45 °C, saturated coal-rock samples experienced macroscopic failure after only 23 freeze–thaw cycles, which is 9 and 15 cycles fewer than those under −30 °C and −15 °C, respectively. Furthermore, measurements of wave velocities in three directions before and after testing revealed that freeze–thaw cycles caused particularly pronounced damage in the direction perpendicular to the bedding planes. Additionally, the established coupled statistical damage constitutive model provides a more accurate and intuitive analysis of the entire process from damage to failure under different cold conditions, showing that as the temperature decreases and freeze–thaw cycles increase, the coal-rock’s brittleness diminishes while plastic deformation and ductile failure characteristics are enhanced. In summary, for coal and CBM extraction using the LNCFT technique, it is recommended to extract gas once after approximately 35 cycles of liquid nitrogen injection. This study provides a theoretical basis for the application of liquid nitrogen cyclic freeze–thaw technology in deep coal fracturing. Full article

Sperm cryopreservation is a key technique in assisted reproductive technologies (ART), livestock breeding, fertility preservation, and wildlife conservation. However, the freeze–thaw process induces significant oxidative stress through the production of reactive oxygen species (ROS) by mitochondria, which can lead to impaired sperm motility, membrane damage, DNA fragmentation, and reduced fertilization potential. MitoQ is a mitochondria-targeted antioxidant consisting of a ubiquinone moiety conjugated to triphenylphosphonium (TPP⁺). MitoQ selectively accumulates in the mitochondrial matrix, where it efficiently scavenges reactive oxygen species (ROS) at their point of origin. This targeted action helps preserve mitochondrial function, sustain ATP production, and inhibit apoptotic signaling. Extensive experimental evidence across diverse species, including bulls, rams, boars, humans, dogs, and goats, shows that MitoQ supplementation during cryopreservation enhances post-thaw sperm viability, motility, membrane integrity, and DNA stability. Optimal dosing between 50 and 150 nM achieves these benefits without cytotoxicity, although higher doses may paradoxically increase oxidative damage. Compared to conventional antioxidants, MitoQ offers superior mitochondrial protection and enhanced preservation of sperm bioenergetics. Future directions involve exploring synergistic combinations with other cryoprotectants, advanced delivery systems such as nanoparticles and hydrogels, and detailed mechanistic studies on long-term effects. Overall, MitoQ represents a promising adjunct for improving sperm cryopreservation outcomes across clinical, agricultural, and conservation settings. Full article