Search Results (718)

The ongoing global climate change has led to an increase in the frequency and complexity of drought events. Pinus yunnanensis, a native tree species in southwest China that possesses significant ecological and economic value, exhibits a high sensitivity to drought stress, particularly in its seedlings. This study investigates the response mechanisms of non-structural carbohydrates (NSCs, defined as the sum of soluble sugars and starch) and the stoichiometric characteristics of carbon (C), nitrogen (N), and phosphorus (P) to repeated drought conditions in Pinus yunnanensis seedlings. We established three treatment groups in a potting water control experiment involving 2-year-old Pinus yunnanensis seedlings: normal water supply (CK), a single drought (D1), and three drought–rewatering cycles (D3). The findings indicated that the frequency of drought occurrences, organ responses, and their interactions significantly influenced the non-structural carbohydrate (NSC) content and its fractions, as well as the C/N/P content and its stoichiometric ratios. Under D3 treatment, stem NSC content increased by 24.97% and 29.08% compared to CK and D1 groups (p < 0.05), respectively, while root NSC content increased by 41.35% and 49.46% versus CK and D1 (p < 0.05). The pronounced accumulation of soluble sugars and starch in stems and roots under D3 suggests a potential stress memory effect. Additionally, NSC content in the stems increased significantly by 77.88%, while the roots enhanced their resource acquisition by dynamically regulating the C/P ratio, which increased by 23.26% (p < 0.05). Needle leaf C content decreased (18.77%) but P uptake increased (8%) to maintain basal metabolism (p < 0.05). Seedling growth was N-limited (needle N/P < 14) and the degree of N limitation was exacerbated by repeated droughts. Phenotypic plasticity indices and principal component analysis revealed that needle nitrogen and phosphorus, soluble sugars in needles, stem C/N ratio (0.61), root C/N ratio (0.53), and stem C/P ratio were crucial for drought adaptation. This study elucidates the physiological mechanisms underlying the resilience of Pinus yunnanensis seedlings to recurrent droughts, as evidenced by their organ-specific strategies for allocating carbon, nitrogen, and phosphorus, alongside the dynamic regulation of nitrogen storage compounds (NSCs). These findings provide a robust theoretical foundation for implementing drought-resistant afforestation and ecological restoration initiatives targeting Pinus yunnanensis in southwestern China. Full article

Carbon (C) sequestration and nitrogen (N) and phosphorus (P) accumulation in urban forest green spaces are significant for global climate regulation and alleviating nutrient pollution. However, the effects of management and conservation practices across different urban forest vegetation types on soil C, N, and P contents and stoichiometric ratios remain largely unexplored. We selected forest soils from Guangzhou, a major Metropolis in China, as our study area. Soil samples were collected from two urban secondary forests that naturally regenerated after disturbance (108 samples) and six urban forest parks primarily composed of artificially planted woody plant communities (72 samples). We employed mixed linear models and variance partitioning to analyze and compare soil C, N, and P contents and their stoichiometry and its main driving factors beneath suburban forests and urban park vegetation. These results exhibited that soil pH and bulk density in urban parks were higher than those in suburban forests, whereas soil water content, maximum storage capacity, and capillary porosity were higher in urban forests than in urban parks. Soil C, N, and P contents and their stoichiometry (except for N:P ratio) were significantly higher in suburban forests than in urban parks. Multiple analyzes showed that soil pH had the most pronounced negative influence on soil C, N, C:N, C:P, and N:P, but the strongest positive influence on soil P in urban parks. Soil water content had the strongest positive effect on soil C, N, P, C:N, and C:P, while soil N:P was primarily influenced by the positive effect of soil non-capillary porosity in suburban forests. Overall, our study emphasizes that suburban forests outperform urban parks in terms of carbon and nutrient accumulation, and urban green space management should focus particularly on the impact of soil pH and moisture content on soil C, N, and P contents and their stoichiometry. Full article

Anion exchange membrane (AEM) water electrolysis is a potentially inexpensive and efficient source of hydrogen production as it uses effective low-cost catalysts. The catalytic activity and performance of nickel iron oxide (NiFeO_x) catalysts for hydrogen production in AEM water electrolyzers were investigated. The NiFeO_x catalysts were synthesized with various iron content weight percentages, and at the stoichiometric ratio for nickel ferrite (NiFe₂O₄). The catalytic activity of NiFeO_x catalyst was evaluated by linear sweep voltammetry (LSV) and chronoamperometry for the oxygen evolution reaction (OER). NiFe₂O₄ showed the highest activity for the OER in a three-electrode system, with 320 mA cm⁻² at 2 V in 1 M KOH solution. NiFe₂O₄ displayed strong stability over a 600 h period at 50 mA cm⁻² in a three-electrode setup, with a degradation rate of 15 μV/h. In single-cell electrolysis using a X-37 T membrane, at 2.2 V in 1 M KOH, the NiFe₂O₄ catalyst had the highest activity of 1100 mA cm⁻² at 45 °C, which increased with the temperature to 1503 mA cm⁻² at 55 °C. The performance of various membranes was examined, and the highest performance of the tested membranes was determined to be that of the Fumatech FAA-3-50 and FAS-50 membranes, implying that membrane performance is strongly correlated with membrane conductivity. The obtained Nyquist plots and equivalent circuit analysis were used to determine cell resistances. It was found that ohmic resistance decreases with an increase in temperature from 45 °C to 55 °C, implying the positive effect of temperature on AEM electrolysis. The FAA-3-50 and FAS-50 membranes were determined to have lower activation and ohmic resistances, indicative of higher conductivity and faster membrane charge transfer. NiFe₂O₄ in an AEM water electrolyzer displayed strong stability, with a voltage degradation rate of 0.833 mV/h over the 12 h durability test. Full article

Fischer–Tropsch synthesis (FTS) facilitates the conversion of syngas, derived from feedstocks such as biomass, coal, and natural gas, into valuable hydrocarbons (HCs). This investigation employed optimization methods, specifically Gibbs energy minimization, to perform a thermodynamic characterization of the low-temperature Fischer–Tropsch (LTFT) reaction for HC generation. The CONOPT3 solver within GAMS 23.2.1 software was utilized for solving the developed model. To represent the complex FTS product spectrum, twenty-three compounds, encompassing C₂–C₂₀ aliphatic hydrocarbons, were considered using a stoichiometric framework. The study explored the impact of operational parameters, including temperature (350–550 K), pressure (5–30 bar), and H₂/CO molar feed ratio (1.0–2.0/0.5–1.0), on hydrocarbon synthesis. Evaluation of the outcomes focused on HC yield and product characteristics. A significant sensitivity of the reaction to operating parameters was observed. Notably, lower temperatures, elevated pressures, and a H₂/CO ratio of 2.0/1.0 were identified as optimal for fostering the formation of longer-chain HCs. The developed model demonstrated robustness and efficiency, with rapid computation times across all simulations. Full article

Mercury is a highly toxic heavy metal that poses serious threats to human health and environmental safety, highlighting the critical importance of accurate Hg²⁺ detection. In this study, a novel fluorescent probe AP was synthesized by conjugating fluorescein, serving as the luminescent group, with pyridine-2-carboxaldehyde to enable selective Hg²⁺ detection. Hg²⁺ binds to AP in a 1:2 stoichiometric ratio, inducing the opening of the spiro-lactam ring and resulting in a significant fluorescence enhancement. The probe exhibited excellent selectivity and sensitivity toward Hg²⁺. A strong linear correlation was observed between its fluorescence intensity and Hg²⁺ concentration (R² = 0.99952), with a detection limit of as low as 9.75 × 10⁻⁸ mol/L. The average recoveries of Hg²⁺ across various water matrices ranged from 95.23% to 103.40%, with relative standard deviations (RSDs) below 3.07%. These results indicate that the probe performs effectively in real water-sample testing. Full article

Salbutamol sulfate is a selective β2-receptor agonist used to treat asthma and chronic obstructive pulmonary disease. The crystals of salbutamol sulfate usually appear as needles with a relatively large aspect ratio, showing poor powder properties. In this study, spherical particles of salbutamol sulfate were obtained via antisolvent crystallization. Four different antisolvents, including ethanol, n-propanol, n-butanol, and sec-butanol, were selected, and their effects on crystal form and morphology were compared. Notably, a new solvate of salbutamol sulfate with sec-butanol has been obtained. The novel crystal form was characterized by single-crystal X-ray diffraction, revealing a 1:1 stoichiometric ratio between solvent and salbutamol sulfate in the crystal lattice. In addition, the effects of crystallization temperature, solute concentration, ratio of antisolvent to solvent, feeding rate, and stirring rate on the morphology of spherical particles were investigated in different antisolvents. We have found that crystals grown from the n-butanol–water system at optimal conditions (25 °C, antisolvent/solvent ratio of 9:1, and drug concentration of 0.2 g·mL⁻¹) could be developed into compact and uniform spherulites. The morphological evolution process was also monitored, and the results indicated a spherulitic growth pattern, in which sheaves of plate-like crystals gradually branched into a fully developed spherulite. This work paves a feasible way to develop new crystal forms and prepare spherical particles of pharmaceuticals. Full article

Exploring the mechanisms by which green agricultural production reduces emissions and enhances carbon sequestration in soil can provide a scientific basis for greenhouse gas reduction and sustainable development in farmland. This study uses a combination of meta-analysis and field experiments to evaluate the impact of different agricultural management practices and climatic conditions on soil organic carbon (SOC) and the emissions of CO₂ and CH₄, as well as the role of microorganisms. The results indicate the following: (1) Meta-analysis reveals that the long-term application of organic fertilizers in green agriculture increases SOC at a rate four times higher than that of chemical fertilizers. No-till and straw return practices significantly reduce CO₂ emissions from alkaline soils by 30.7% (p < 0.05). Warm and humid climates in low-altitude regions are more conducive to soil carbon sequestration. (2) Structural equation modeling of plant–microbe–soil carbon interactions shows that plant species diversity (PSD) indirectly affects microbial biomass by influencing organic matter indicators, mineral properties, and physicochemical characteristics, thereby regulating soil carbon sequestration and greenhouse gas emissions. (3) Field experiments conducted in the typical green farming research area of Chenzhuang reveal that soils managed under natural farming absorb CH₄ at a rate three times higher than those under conventional farming, and the stoichiometric ratios of soil enzymes in the former are close to 1. The peak SOC (19.90 g/kg) in the surface soil of Chenzhuang is found near fields cultivated with natural farming measures. This study provides theoretical support and practical guidance for the sustainable development of green agriculture. Full article

Long-term irrational farming practices and low return of organic materials to the fields in the black soil area have led to reduced soil carbon and nitrogen stability and nutrient imbalance, which in turn affect soil fertility and crop yields. Straw return is an effective way to enhance soil organic matter and crop productivity, but the effects of long-term straw return under tilling practices on carbon and nitrogen sequestration and soil microbial stoichiometric equilibrium in black soil need to be further investigated. This study investigated the physical, chemical and biological properties of the 0–60 cm soil layer under deep tillage with straw return to the field (DTS), deep harrow with straw return to the field (DHS), rotary tillage with straw return to the field (RTS), no tillage with straw return to the field (NTS), and conventional tillage with straw removal (CT) on the basis of seven consecutive years of tillage pattern location trials in the black soil area of eastern Inner Mongolia. The results showed that DTS and NTS significantly increased the soil organic carbon (SOC), soil total nitrogen (TN), soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN) contents, and the SOC/TN ratio in the 0–40 cm soil layer, enhancing soil carbon and nitrogen sequestration capacity, while the concomitant increase in the average MBC/MBN ratio in the plow layer from 6.8 to 8.2. The soil microbial quotient increased by 29.0% and 26.2%, respectively, and the stoichiometric imbalance ratio decreased by 7.9% and 5.7%, respectively. Meanwhile, in terms of maize yield from 2018 to 2024, DTS showed the most stable and significant yield increase with 41.53%. Whereas NTS showed a higher yield increase potential with a 27.36% increase in yield as the number of years of straw return increased. Therefore, DTS and NTS are superior tillage methods to improve the quality of the black soil tillage layer, to promote soil microbial carbon and nitrogen balance, and to increase crop yields. Full article

Microstructural, mechanical and qualitative phase identification of durable mullite-based ceramics obtained by utilization of waste clay–diatomite has been studied. Mullite-based ceramics were fabricated using waste clay–diatomite from the Baroševac open-cast coal mine, Kolubara (Serbia). The raw material consists mainly of SiO₂ (70.5 wt%) and a moderately high content of Al₂O₃ (13.8 wt%). In order to achieve the stoichiometric mullite composition (3Al₂O₃-2SiO₂), the raw material was mixed with an appropriate amount of Al(NO₃)₃·9H₂O. After preparing the precursor powder, the green compacts were sintered at 1300, 1400 and 1500 °C for 2 h. During the process, rod-shaped mullite grains were formed, measuring approximately 5 µm in length and a diameter of 500 nm (aspect ratio 10:1). The microstructure of the sample sintered at 1500 °C resulted in a well-developed, porous, nest-like morphology. According to the X-ray diffraction analysis, the sample at 1400 °C consisted of mullite, cristobalite and corundum phases, while the sample sintered at 1500 °C contained mullite (63.24 wt%) and an amorphous phase that reached 36.7 wt%. Both samples exhibited exceptional compressive strength—up to 188 MPa at 1400 °C. However, the decrease in compressive strength to 136 MPa at 1500 °C is attributed to changes in the phase composition, the disappearance of the corundum phase and alterations in the microstructure. This occurred despite an increase in bulk density to 2.36 g/cm³ (approximately 82% of theoretical density) and a complete reduction in open porosity. The residual glassy phase (36.7 wt% at 1500 °C) is probably the key factor influencing the mechanical properties at room temperature in these ceramics produced from waste clay–diatomite. However, the excellent mechanical stability of the samples sintered at 1400 and 1500 °C, achieved without binders or additives and using mined diatomaceous earth, supports further research into mullite-based insulating materials. Mullite-based materials obtained from mining waste might be successfully used in the field of energy-efficient refractory materials and thermal insulators. for high-temperature applications Full article

The mean force between two highly like-charged macroions in the presence of monovalent counterions and added multivalent salt within solvents of varying dielectric constants was studied using Monte Carlo simulations. Without additional salt, the mean force is strongly repulsive at all macroion separations in solvents with a dielectric constant ${ϵ}_r$ ≥ 30. However, in solvents with ${ϵ}_r$≤ 30, macroions experience effective attraction, indicating that attractive interactions between highly charged macroions can occur even without multivalent salt in nonpolar solvents with low dielectric constants. The total multivalent counterion charge-to-total macroion charge ratio is defined as β which determines the amount of salt that is added to the system. At β = 0.075, the mean force becomes attractive at short separations in solvents with ${ϵ}_r$= 54 containing 1:3 salt, as well as in all solvents with 1:5 salt, while still exhibiting significant repulsion at longer separations. In contrast, for solvents with 1:3 salt and dielectric constants ${ϵ}_r$= 68 and ${ϵ}_r$= 78.4, the mean force turns attractive at a higher salt concentration, around β = 0.225. The shift in the mean force to an attractive state at short separations signifies charge inversion on the macroion surface when a sufficient amount of salt is present. At a stoichiometric ratio of multivalent counterions, long-range repulsion vanishes, and attraction becomes significant. However, with excess salt, the strength of the attractive mean force diminishes. Additionally, the attractive force at a given salt concentration increases as the dielectric constant decreases and is stronger in systems with 1:5 salt than in those with 1:3 salt. Full article

Increasing soil organic carbon (SOC) storage is essential for improving soil fertility and mitigating climate change. The priming effect, which is regulated by physical, chemical and microbial interactions, plays a pivotal role in SOC turnover. However, the fate of both native and newly added carbon under different tillage regimes remains unclear. To address this gap, a ¹³C-glucose labelling incubation experiment was conducted to assess SOC mineralization and priming effects under long-term tillage practices, including subsoiling with straw mulching (ST), no tillage with straw mulching (NT), and conventional tillage with straw removal (CT). The results demonstrated that conservation tillage (NT and ST) significantly reduced total SOC mineralization and glucose-derived CO₂ release compared to CT. Notably, the priming effect under CT was 19.5% and 24.7% higher than under NT and ST, respectively. In the early incubation stage, positive priming was primarily driven by microbial co-metabolism, while during days 1–31, microbial stoichiometric decomposition dominated the process. In addition, NT and ST treatments significantly increased the proportion of >250 μm aggregates and their associated carbon and nitrogen contents, thereby enhancing aggregate stability and physical protection of SOC. The priming effect observed under conservation tillage was strongly negatively related to aggregate stability and aggregate associated carbon content, whereas it was positively related to the β-glucosidase/Peroxidase ratio (BG/PER) and the subtraction value between carbon/nitrogen (R_C:N) and the carbon–nitrogen imbalance of the available resources (TER_C:N). Overall, our findings highlight that conservation tillage enhances SOC stability not only by improving soil physical structure but also by alleviating microbial stoichiometric constraints, offering a synergistic pathway for carbon retention and climate-resilient soil management. Full article

Two-dimensional film materials with unique atomic structures and electronic operation modes have demonstrated amazing application potential and value in the field of high technology. Among the various methods for preparing 2D film materials, PLD technology has become the preferred technology for rapid and green preparation of high-quality, complex structured 2D film materials due to its features such as maintaining the excellent stoichiometric ratio of the target, strong process flexibility, and non-polluting environment. Therefore, this paper discusses the exciting topic of PLD technology in the preparation and application of 2D film materials. Based on a systematic exposition of its basic principles and influencing factors, it provides a detailed overview of the current application status of PLD technology in the preparation of various 2D film materials such as carbides, sulfides, oxides, nitrides, and perovskites. Meanwhile, the advantages and disadvantages of PLD technology in the preparation of 2D film materials were also positively summarized, and the challenges and emerging strategies it faces in the future preparation of 2D film materials were cautiously discussed. This provides practical suggestions and reflections for the sustainable development of PLD technology in the fields of basic research, performance regulation, device development, and application of 2D film materials preparation. Full article

In order to elucidate the factors regulating nutrient dynamics in plant–soil interactions across various latitudes within the karst climax community, this study focused on the karst forest climax community in Guizhou Province, Southwest China. We analyzed and compared the differences in carbon, nitrogen, and phosphorus content, as well as stoichiometry, in plant leaves and soils under various growing conditions. Additionally, redundancy analyses were conducted to investigate the stoichiometric correlations between plants and soil. The research findings indicate the following: (1) Leaf carbon content (LCC) and the carbon-to-nitrogen ratio (LCN) exhibit significant differences across various latitudes, with the lowest values observed in high-latitude regions. (2) Soil organic carbon (SOC) and the carbon-to-nitrogen ratio (SCN) also show significant variations across latitudes, with the lowest concentrations found in high-latitude regions and the highest in low-latitude regions. (3) The variability in leaf nutrient element ratios among karst region climax communities is greatest in low-latitude areas. This study found that the carbon content (LCC), nitrogen content (LNC), and carbon-to-nitrogen ratio (LCN) of leaves in karst climax community plants decrease as latitude increases. This suggests that plants regulate the nutrient utilization efficiency of carbon content (LCC), nitrogen content (LNC), and phosphorus content (LPC) in their leaves to maintain the nutrients necessary for their growth and development along the latitudinal gradient. The sensitivity of soil organic carbon (SOC), carbon-to-nitrogen (SCN), and carbon-to-phosphorus (SCP) ratios to latitudinal changes were particularly pronounced in the karst climax community. Additionally, plant leaf stoichiometry was significantly influenced by soil phosphorus content (SPC) in mid- and high-latitude regions, while factors other than soil nitrogen content (SNC) had a more substantial impact on plant leaf stoichiometry in low-latitude areas. The findings of this study are highly significant for guiding nutrient management in karst forest ecosystems and for the restoration of degraded karst forest vegetation. Full article

Illitic clays are one of the most important materials used in the ceramic industry. Carbonates support the densification and the sintering of ceramics. Five mixtures of illitic clay with calcite were prepared aiming for the crystallization of anorthite ceramics. The stoichiometric ratio of anorthite crystallization was determined at 21.6 wt.% of calcite content. To reveal the effect of calcite on the crystallization processes, two more mixtures were prepared below the stoichiometric composition (17.6 wt.% and 19.6 wt.%) and two more mixtures above the ideal composition (23.6 wt.% and 25.6 wt.%). X-ray diffraction revealed that gehlenite and Ca-feldspar were formed, which are the intermediate phases in anorthite crystallization. However, due to the low purity of illitic clay and the low firing temperature, no anorthite formation was observed. The influence of calcite content on Young’s modulus was negligible. However, a clear effect on the open porosity was revealed. Full article

Silicon oxynitride (SiO_xN_y, hereafter denoted as SiON) thin films represent an intermediate phase between silicon dioxide (SiO₂) and silicon nitride (Si₃N₄). Through systematic compositional ratio adjustments, the refractive index can be precisely tuned across a wide range from 1.45 to 2.3. However, the underlying mechanism governing the influence of elemental composition on film structural quality remains insufficiently understood. To address this knowledge gap, we systematically investigate the effects of key industrial plasma-enhanced chemical vapor deposition (PECVD) parameters—including precursor gas selection and flow rate ratios—on SiON film properties. Our experimental measurements reveal that stoichiometric SiO_xN_y (x = y) achieves a minimum surface roughness of 0.18 nm. As oxygen content decreases and nitrogen content increases, progressive replacement of Si-O bonds by Si-N bonds correlates with increased structural defect density within the film matrix. Capacitance–voltage (C-V) characterization demonstrates a corresponding enhancement in device capacitance following these compositional modifications. Recent studies confirm that controlled modulation of film stoichiometry enables precise tailoring of dielectric properties and capacitive behavior, as demonstrated in SiON-based power electronics, thereby advancing applications in related fields. Full article