Surface Layer Research Articles

Reconstructing the Surface of K2SiF6:Mn4+ Phosphors toward Enhanced Moisture Resistance for White LED Applications.

The K2SiF6:Mn4+ (KSFM) phosphor featuring efficient ultranarrow red emissions is an outstanding candidate for white light-emitting diode (WLED) applications. However, poor moisture resistance seriously affects its application performance. In this study, a two-step surface reconstruction strategy is proposed to dramatically enhance the moisture resistance of commercially available KSFM phosphors, involving treatment with H2NbF7 and subsequent hydrothermal treatment. The modified KSFM phosphor exhibits a high internal quantum efficiency (IQE) of 98.9% after the two-step surface treatment. Meanwhile, nearly 100% of the initial emission intensity is retained for the modified KSFM phosphor even after aging in high temperature (85 °C) and high relative humidity (85% RH) environments for 6 days, in sharp contrast to only 18.6% retention for the original KSFM phosphor. The relative emission intensity of the modified KSFM remains at 98.9% even after being immersed in water for 6 h. Additionally, the phosphor-converted LED fabricated with the modified KSFM phosphor demonstrated excellent long-term stability, retaining up to 97.9% of initial luminous efficacy after aging under 85 °C and 85% RH conditions for 500 h. The moisture-resistance mechanism is elucidated on the basis of spectroscopic analysis as well as structural and compositional characterization of the phosphor surface layer, which can be attributed to the formation of a robust Mn4+-rare shell with high crystalline quality following this two-step surface treatment. The findings contribute to the performance improvements of KSFM phosphors for industrial applications.

Spatial Differentiation Characteristics of Soil Organic Carbon and Its Influencing Factors in Cultivated Land in Major Grain-producing Areas： A Case Study of Hebei Province

Assessing the spatial differentiation characteristics of soil organic carbon （SOC） in cultivated land in major grain-producing areas is important for regional cultivated land quality management and national food security. We investigated 519 soil profiles of cultivated land in Hebei Province （0-120 cm equally divided into six layers）, and obtained 2961 samples. We used geostatistical methods and spatial exploratory analysis to reveal the spatial distribution pattern of SOC in cultivated land in Hebei Province and the impacts of climate, topography, geomorphology, soil properties, and anthropogenic use on the spatial distribution of SOC in cultivated land soils. The results showed that： ① The SOC content of cultivated land in Hebei Province showed a decreasing trend with the increase in soil depth, with the highest mean value of ω（SOC） of 9.57 g·kg-1 in A1 （0-20 cm） and the lowest mean value of 4.17 g·kg-1 in A6 （100-120 cm）, and the coefficient of variation showed an increasing trend with the increase in soil depth. ② The SOC at different depths of cultivated land in Hebei Province had similar horizontal spatial distribution characteristics, and in general, showed a trend of being high in the northwest and low in the southeast. ③ Soil texture and topography were the main influencing factors for the spatial variation of SOC in cultivated land in Hebei Province, showing that the more clay-rich the soil texture, the greater the SOC content, and the higher the elevation, the greater the SOC content. Soil pH also influenced the SOC content of the profile. The SOC content of the surface layer is mainly affected by anthropogenic use, whereas the bottom layer is affected by the cumulative temperature.

Investigating Hot corrosion, CMAS, and Thermal Shock Behaviour of Double-layer YSZ/La2Ce2O7 + YSZ Thermal Barrier Coatings

AbstractIn this work, new double-layer YSZ/La2Ce2O7 (LC) + YSZ coatings were developed using air plasma spraying (APS). The surface of the prepared coatings was relatively smooth and consisted of melted and partially melted areas. Their resistance to hot corrosion, CaO-MgO-Al2O3-SiO2 (CMAS), and thermal shock were examined. YSZ was added to the upper layer to enhance the lanthanum cerate (La2Ce2O7, LC) properties. During the hot corrosion tests, the corrosion salt reacted with the upper layer, and the CeO2 phase and new corrosion products were identified. The main phase was LaVO4, and the secondary phases were CeVO4 and YVO4. SEM confirmed the formation of new, cuboidal-shaped corrosion products. The infiltration of CMAS led to the formation of additional new products: Ca4MgxAl4Si(6-x-γ)O14 and Ca2.8(LaxCe1-x).6(SiO4)O6-4x. SEM revealed CMAS infiltration through the upper layer in the form of islands. Following the thermal shock resistance tests, the upper layer gradually peeled off, and the coating survived 67 cycles. Possible failure mechanisms were identified, and failure was attributed to the spallation of the upper layer from the surface layer by layer. After all tests, the top layer showed partial spalling and delamination. This was mainly caused by the reaction of corrosive salt or CMAS with the top layer, which changed its composition, leading to the formation and propagation of cracks and, ultimately, the separation of part of the upper layer. Peeling of the upper layer through mainly horizontal cracks was observed after hot corrosion, CMAS and thermal shocks. The NiCrAlY bond coat and YSZ interlayer remained undamaged.

Surface Regulation via Carboxylate Polymer for Efficient and Stable CsPbI2Br Perovskite Solar Cells.

CsPbI2Br perovskite solar cell (PSC) is a promising candidate for high-efficiency single-junction and tandem solar cells. However, due to the numerous surface defects of the CsPbI2Br film and the mismatch of energy levels at the CsPbI2Br/charge transport layer interface, the power conversion efficiency (PCE) of CsPbI2Br PSC is still significantly lower than the theoretical limits. To alleviate those issues, in this work, a carboxylate-based p-type polymer, TTC-Cl, is employed to modify the surface of CsPbI2Br layer. TTC-Cl can interact with uncoordinated Pb2+, thereby mitigating surficial defects of CsPbI2Br film and reducing non-radiative recombination losses. Furthermore, TTC-Cl also improves the band properties of the CsPbI2Br thin film surface, rendering it more p-type, which facilitates hole transport. Consequently, the CsPbI2Br PSCs with TTC-Cl modification achieve a remarkable PCE of 17.81%, which is notably higher than that of counterpart without TTC-Cl (15.87%). Moreover, CsPbI2Br PSCs with TTC-Cl modification also exhibit better stability. This work highlights the importance of surface regulation via carboxylate polymer for further enhancing the performance of CsPbI2Br PSCs.

Effects of Stress and Strain on the Optic Nerve Head on the Progression of Glaucoma.

In primary open-angle glaucoma, the rate of retinal nerve fiber layer thickness decrease was negatively correlated with lamina cribrosa strain, which was associated with intraocular pressure and optic nerve head geometric factors. We hypothesized that the biomechanical deformation of the optic nerve head (ONH) contributes to the progression of primary open-angle glaucoma (POAG). This study investigated the biomechanical stress and strain on the ONH in patients with POAG using computer simulations based on finite element analysis (FEA) and analyzed its association with disease progression. We conducted a retrospective analysis that included patients diagnosed with early-to-moderate stage POAG. The strains and stresses on the retinal nerve fiber layer (RNFL) surface, prelaminar region, and lamina cribrosa (LC) were calculated using computer simulations based on FEA. The correlations between the rate of RNFL thickness decrease and biomechanical stress and strain were investigated in both the progression and non-progression groups. The study included 71 and 47 patients in the progression and non-progression groups, respectively. In the progression group, the factors exhibiting negative correlations with the RNFL thickness decrease rate included the maximum and mean strain on the LC. In multivariate analysis, the mean strain on the LC was associated with optic disc radius, optic cup deepening, axial length, and mean intraocular pressure (IOP), whereas the maximum strain was only associated with mean IOP. In early-to-moderate stage POAG, the rate of RNFL thickness decrease was influenced by both the mean and maximum strain on the LC. Strains on the LC were associated with mean IOP, optic disc radius, axial length, and optic cup deepening. These results suggest that not only IOP but also ONH geometric factors are important in the progression of glaucoma.

Assessment of the Influence of Features of Crack Formation in Reinforced Concrete Products on their Fire Resistance

The paper considers possible scenarios of cracking during heating and their impact on fire resistance using the example of a bending reinforced concrete structure (beam). It is shown that if the calculated critical temperature of reinforcement is less than the critical temperature of concrete (this indicates a significant load on the structure), then cracks in the tensile zone of concrete are formed after reaching the second stage of the stress-strain state. The concrete of the protective layer does not have time to degrade, the depth of the crack remains constant, and the fire resistance limit is calculated taking into account that the thickness of the protective layer of concrete is reduced by the depth of the crack opening. If the calculated critical temperature of the reinforcement is greater than the critical temperature of the concrete (this indicates a slight load on the structure), then cracks are formed as a result of the degradation of the surface layer of concrete. Their depth should constantly increase with the progression of the concrete layer heating to the critical temperature. In this case, the calculation of the fire resistance limit can be performed without taking into account the formation of cracks. Based on the considered assumptions, a methodology for assessing the impact of cracks on the fire resistance limit of bending reinforced concrete structures is proposed, which consists in analyzing the possibility of open cracks (which is facilitated by heating) and estimating their depth. At the next stage, the heating time of the concrete layer to the crack opening depth τΔ1 and the temperature in the crack after this time are estimated. Next, the time until the critical temperature of the reinforcement τΔ2 is estimated when the concrete layer is heated from the bottom of the crack to the reinforcement. The fire resistance limit is defined as the sum of τΔ1 and τΔ2. The results of the calculations according to the proposed methodology showed that the presence of open cracks in bending reinforced concrete structures can almost halve the fire resistance limit.

Mechanisms of Chemically Promoted Material Removal Examined for Molybdenum and Copper CMP in Weakly Alkaline Citrate-Based Slurries

Chemical mechanical planarization (CMP) of metal components is an essential step in the fabrication of integrated circuits. Metal CMP is a complex process where strategically activated (electro)chemical reactions serve to structurally weaken the surface layers of the material being processed, and the resulting overburdens are removed under low-force abrasion. Understanding the tribo-electrochemical mechanisms of this process is crucial to successfully designing the consumable materials for advanced CMP slurries that are needed for the new technology nodes. Using a model CMP system involving copper (wiring material in interconnect structures) and molybdenum (a new diffusion barrier material for copper), the present work illustrates a tribo-electroanalytical scheme for studying various mechanistic details of metal CMP. Electroanalytical probes are employed both in the absence and in the presence of surface polishing to quantify the interplay between mechanical abrasion and chemical surface modification. Weakly alkaline slurry formulations are tested with variable concentrations of silica abrasives and a complexing agent, citric acid. The results serve to examine the link between material removal and tribo-corrosion and to identify the functions of the active slurry additives in governing the rates and selectivity of material removal for CMP.

Sustainable Diamond Burnishing of Chromium–Nickel Austenitic Stainless Steels: Effects on Surface Integrity and Fatigue Limit

This study aims to evaluate the influence of lubrication and cooling conditions in the diamond burnishing (DB) process on the surface integrity and fatigue limit of chromium–nickel austenitic stainless steels (CNASSs) and, on this basis, identify a cost-effective and sustainable DB process. Evidence was presented that DB of CNASS performed without lubricating cooling liquid satisfies the requirements for a sustainable process: the three key sustainability dimensions (environmental, economic, and social) are satisfied, and the cost/quality ratio is favorable. DB was implemented with the same values of the main governing factors; however, four different lubrication and cooling conditions were applied: (1) flood lubrication (process F); (2) dry without cooling (process D); (3) dry with air cooling at a temperature of −19 °C (process A); and (4) dry with nitrogen cooling at a temperature of −31 °C (process N). Conditions A and N were realized via a device based on the principle of vortex tubes. All four DB processes provide mirror-finished surfaces with Ra roughness parameter values from 0.041 to 0.049 μm, zones with residual compressive stresses deeper than 0.5 mm, and increases in the specimens’ fatigue limit (as determined by the accelerated Locati’s method) compared to turning and polishing. Processes F and D produce the highest microhardness on the surface and at depth. The process D introduces maximum compressive residual axial and hoop stresses in the surface layer. The dry DB processes (D, A, and N) form a submicrocrystalline structure with high atomic density, which is most strongly developed under process D. When high fatigue strength is required, DB with air cooling should be chosen, as it provides a more favorable cost/quality ratio, whereas dry DB without cooling is the most suitable choice for applications that require increased wear resistance.

Mechanistic Model of Fatigue in Ultrasonic Assisted Machining.

Anti-fatigue design in the machining process of aviation material requires advanced processes to enhance the surface integrity and a holistic model which can optimize the process aiming at maximum fatigue life. In the present study, the axial ultrasonic assisted milling process was utilized to machine the Inconel 718 while the process executes the thermomechanical cutting and peening action simultaneously. To optimize the process factors, a hybrid model using a combination of regression analysis and an analytical model was developed to correlate the machining factors, i.e., vibration amplitude, cutting velocity and feed rate to fatigue life. Herein, the former was used to map the process inputs to surface integrity aspects (SIAs), viz. roughness, hardness and residual stress; then, the SIA was mapped to fatigue life through a stress-based approach. The obtained results revealed that there is close agreement between the measured and predicted values of fatigue life where the prediction error is less than two times the dispersion. On the other hand, applying ultrasonic vibration at the highest amplitude together with the maximum feed rate and cutting velocity yield significant improvement in fatigue life, i.e., three times the same condition without ultrasonic vibration in light of the enhancement of compressive residual stress and work hardening of the surface layers.

Bending properties and deformation micromechanisms of near-α titanium alloy sheets/foils considering initial texture characteristics and size effect

Clarifying the bending deformation behaviour of metal foils is essential for meeting the lightweighting requirements of metal honeycomb structures. This study selected Ti65 alloy specimens with various thicknesses and initial α-phase textures to conduct room-temperature three-point bending experiments. A detailed comparative analysis was performed on the bending deformation behaviour of Ti65 alloy sheets and foils. It reveals that in the foil specimens, the weakening effect of surface layer grains is significant. Under the influence of size effects, the springback angle of Ti65 alloy foils with coarse α-phase grains decreases markedly. Additionally, through various methods, including global Schmid factor analysis, lattice rotation analysis, and crystal plasticity finite element method simulations, the specific relationship between α-phase texture and the bending performance of Ti65 alloy foils was thoroughly investigated. The rolling process influences the bending performance of Ti65 alloy by determining the α-phase texture. Unidirectionally rolled Ti65 alloy products exhibit a transverse α-phase texture, which predisposes them to form transverse texture α-phase macrozones during bending. In contrast, cross-directionally rolled Ti65 alloy foils possess a basal α-phase texture biased toward the transverse direction. This not only helps avoid the formation of macrozones but also ensures coordinated deformation across the foil, resulting in superior bending performance.

Translocation and dissipation of seven indicator polychlorinated biphenyls from contrast soils cultivated with different root vegetables

The behavior of 7 polychlorinated biphenyls (PCBs) in agricultural Chernozem and Fluvisol soils from the Czech Republic planted with radishes, onions, and carrots was studied. Only the total biomass yield of carrots was significantly reduced (P < 0.05) when compared to the control biomass yield. All tested PCBs, especially congener PCB 28, were able to accumulate in slightly higher amounts in the radish surface than in the onion one. The highest PCB content was observed in the surface layer of carrots, which could be related to the agrochemical properties of soil, vegetation period, and more intensive contact of carrot roots with PCBs in a bulk soil. The translocation factors of PCBs were lower than 1, indicating a poor ability for PCB uptake from soil. The highest relative PCB removal from soil was observed in acidic Fluvisol, accounting for 27.2%, with a maximum of 2% plant contribution to soil PCB dissipation. The low relative removal of PCBs by plants indicates that in vegetable-planted soil, the removal of PCBs could be due to autochthonous soil microorganisms in the rhizosphere of vegetables. The bioaccumulation factors for PCBs derived from the cultivation of examined root vegetables in Chernozem and Fluvisol soils contaminated with PCBs at nearly 1500 µg/kg dry weight can be considered low and negligible.

Surface fatigue characterization and its enhancement by the engineered ultrasonic rolling process for 300 M ultrahigh strength steel

The fatigue life of surface layer (FSL) is innovatively characterized to accurately capture the effect of surface integrity on the fatigue behavior of the components. The sensitivity of FSL of 300 M ultrahigh strength steel to the surface integrity indexes induced by representative manufacturing processes was analyzed by analytical modeling and fatigue tests from the perspective of engineering fracture mechanics. The ultrasonic surface rolling process (USRP) was introduced to optimize the fatigue limit of 300 M steel, and the improvement in fatigue life was experimentally quantified. Besides, the fracture analysis was conducted to provide the reason why USRP can enhance the fatigue behavior of 300 M steel. The results show that FSL occupies a majority with percentage of over 95 % in the entire fatigue life and a strong relation with the machined surface defects, especially the surface machining marks. The excellent surface finishing effect and high compressive residual stresses induced by engineered USRP could transfer the crack source from surface machining marks into subsurface inclusions, which greatly prolongs the fatigue crack initiation life and thereby the entire fatigue life. To be specific, the fatigue life was elevated by more than 40 times and the fatigue strength was increased by 34.7 % after USRP for the tested 300 M steel.

A study on the multi layers of automotive interior trim parts to improve the acoustic performance with microfiber applied to the surface layer

As the world joins environmental regulations, there is an increasing demand for the production of eco-friendly cars. As a result, the driving method of the vehicle was changed from the engine to the electric motor, and the main noise source was changed. In case of existing internal combustion engines (ICE), the low-frequency sound range, which is the engine's main noise, is the main source of sound. As it is converted into an eco-friendly car, the noise that was hidden by the engine combustion sound and the high-frequency noise of the motor are being highlightened. PP meltblown generally has a lower denier than other fibers, so it is effective in improving sound absorption performance because the surfaces of the fibers are large compared to the same weight of another fibers. In conclusion, by applying this PP meltblown fibers to the structure of Dash Insulation, sound absorption performance is improved and resulting in lightweighten effect of Dash Insulation

Accounting of weathering enhancement by mafic mineral spreading for CO 2 storage

The reduction of atmospheric CO 2 is an urgent global issue in the mitigation of global warming. Carbonate acts as a carbon sink in Earth's surface layer, and the weathering of terrestrial silicates and the deposition of oceanic calcium carbonate and organic matter mainly determine atmospheric and oceanic carbon dynamics on geological time scales. Various CO 2 reduction approaches have been evaluated, and the weathering acceleration method is expected to be a low-cost approach. This study attempts to estimate carbonate precipitation potential and dissolution rate from alkali leaching rates using weathering tests on mafic rocks. Based on Japan's annual average rainfall, the in situ carbonate precipitation potential obtained by spreading an olivine mineral or basalt rock powder at 40 ton-powder/ha was on the order of 10 -3 ton/year/ton-rock. This weathering rate could not be greatly accelerated under natural temperature conditions and fine granulation of the minerals.

Integration of Facet‐Dependent, Adsorbate‐Driven Surface Reconstruction into Multiscale Models for the Design of Ni‐Based Bimetallic Catalysts for Hydrogen Oxidation

AbstractNi‐based bimetallic catalysts (NiM) show promise to replace expensive Pt‐based catalysts for hydrogen oxidation reaction (HOR). However, the effect of dopant and reaction conditions on the adsorbate‐driven surface reconstruction of NiM nanoparticles remains largely unexplored. Here, we use a multiscale modeling approach – integrating density functional theory, kubic harmonics interpolation, and microkinetic modeling – to investigate the interplay between dopant, reaction conditions, facet, adsorbate type, adsorbate coverage, in situ surface structure, and performance for NiM nanoparticles during HOR. Clear periodic trends appear in dopant effects on key adsorption energies, with dopants showing 7‐fold greater effects when located in the surface as compared to subsurface. Multi‐faceted nanoparticle models showed a non‐uniform correlation between O* coverage and surface reconstruction. HOR performance was facet‐dependent, with the highest performance occurring at reactive fronts formed between regions of high O* and OH* coverage. The nanoparticle averaged performance showed promotional effects for nearly all dopants compared to pure Ni, with the best‐performing dopants located preferentially in the surface layer (e. g. Au, Pd, Ag). Taken together, this work emphasizes the importance of understanding the interplay between reaction conditions, surface reconstruction, and HOR performance for NiM nanoparticles, enabling researchers to both predict and control the working nanoscale catalyst structure.

Periderm fate and independence of tooth formation are conserved across osteichthyans

BackgroundPrevious studies have reported that periderm (the outer ectodermal layer) in zebrafish partially expands into the mouth and pharyngeal pouches, but does not reach the medial endoderm, where the pharyngeal teeth develop. Instead, periderm-like cells, arising independently from the outer periderm, cover prospective tooth-forming epithelia and are crucial for tooth germ initiation. Here we test the hypothesis that restricted expansion of periderm is a teleost-specific character possibly related to the derived way of early embryonic development. To this end, we performed lineage tracing of the periderm in a non-teleost actinopterygian species possessing pharyngeal teeth, the sterlet sturgeon (Acipenser ruthenus), and a sarcopterygian species lacking pharyngeal teeth, the axolotl (Ambystoma mexicanum).ResultsIn sturgeon, a stratified ectoderm is firmly established at the end of gastrulation, with minimally a basal ectodermal layer and a surface layer that can be homologized to a periderm. Periderm expands to a limited extent into the mouth and remains restricted to the distal parts of the pouches. It does not reach the medial pharyngeal endoderm, where pharyngeal teeth are located. Thus, periderm in sturgeon covers prospective odontogenic epithelium in the jaw region (oral teeth) but not in the pharyngeal region. In axolotl, like in sturgeon, periderm expansion in the oropharynx is restricted to the distal parts of the opening pouches. Oral teeth in axolotl develop long before mouth opening and possible expansion of the periderm into the mouth cavity.ConclusionsRestricted periderm expansion into the oropharynx appears to be an ancestral feature for osteichthyans, as it is found in sturgeon, zebrafish and axolotl. Periderm behavior does not correlate with presence or absence of oral or pharyngeal teeth, whose induction may depend on ‘ectodermalized’ endoderm. It is proposed that periderm assists in lumenization of the pouches to create an open gill slit. Comparison of basal and advanced actinopterygians with sarcopterygians (axolotl) shows that different trajectories of embryonic development converge on similar dynamics of the periderm: a restricted expansion into the mouth and prospective gill slits.

Study of argon plasma modified Pd/AlGaN/GaN high electron mobility transistor for superior hydrogen gas detection

The surface and microstructure of the sensitive material play an important role in the gas adsorption and detection. However, few report of the surface modification affection on the work function-based gas sensor is carried out. Herein, facile Ar+ modification is proposed and utilized to modify the surface of the Pd sensitive layer, which acts as the gate of a AlGaN/GaN high electron mobility transistor (HEMT) based hydrogen (H2) gas sensor. Results show that the Pd surface is significantly changed to smoother microstructure by 5 s Ar+ modification. Compared with the device without Ar+ modification, the response values increase by ∼ twice at all operating temperatures. Interestingly, the response time is pronouncedly shortened from 10 to 2.3 s at 500 ppm, suggesting the significant effect of Ar+ modification in the enhancement of gas detection. At the optimized operating temperature of 120 °C, a high response of 739% and an ultrafast response time of 1.4 s are observed for the 500 ppm H2 gas. In addition, this sensor exhibits a low limit of detection ∼200 ppb, along with excellent repeatability, consistency, and selectivity. Our study indicates that the facile Ar+ modification of the gate surface is a highly effective technology in the enhancement of gas detection and may provide a novel approach for the design and development of all the work function type gas sensors.

Tuning Nanochannel Microenvironments of a Thermoresponsive MXene Membrane for Mixed Molecule Gradient Separation.

Drawing inspiration from dynamic biological ion channels, researchers have developed various artificial membranes featuring responsive nanochannels. Typically, these membranes modify mass transport behaviors by manipulating the responsive layer on the inner surfaces of the intrinsic layer. In this study, we build two-dimensional lamellar membranes composed of titanium carbide MXene and poly(N-isopropylacrylamide), endowed with dual-level regulatable nanochannels, achieved through adjustments of nanochannel microenvironments. The size of these two-dimensional nanochannels can be altered by both the thermoresponsive polymer layer and the intrinsic MXene layer that could undergo spontaneous oxidation. The multilevel regulation strategy substantially enhances the molecular selectivity of MXene separation membranes, which is further applied for precise gradient separation toward multiple molecules. This advancement showcases the versatility and transformative capabilities of responsive nanochannel technology, setting the stage for innovative developments in diverse fields.

Effects of straws on greenhouse gas emissions in the ectopic fermentation system

Straws are commonly used padding materials in the ectopic fermentation system, but their effects on greenhouse gas emissions are not well understood. This study compared the effects of rape, rice and corn straws on the fermentation performance of the ectopic fermentation system. Compared with corn straw, the treatment groups with rape straw and rice straw significantly increased the alpha diversity of the fermentation system, and simultaneously mitigated the cumulative emissions of CO2 and N2O by up to 32.4% and 93.9%, respectively. The CO2 and N2O peak emission in the treatment group with corn straw reached 1.4 × 106 and 36.2 mg/m2/d, respectively. CH4 peak emission was one order of magnitude lower than that of N2O in the ectopic fermentation system. Redundancy analysis showed that Pseudoxanthomonas sp000510725 was the key specie that positively affect the fermentation temperature, CO2 and N2O emissions in the fermentation system. Nitrogen metabolism genes, such as nosZ, nirK, and nirS were more abundant in the surface layer of the fermentation system, indicating more active nitrogen metabolism in this region, and the core zone could be the primary source of N2O emissions. Those findings indicated that rape and rice straw can be potential padding materials for mitigating greenhouse gas emissions in large-scale ectopic fermentation system.

Changes in freezing parameters and temperature distribution of beef induced by AC electric field: Alleviation on freezing damage and myowater loss

In this study, a specialized experimental device integrating infrared thermal imaging, real-visual photography, and a time-temperature data collector was designed to investigate the effects of alternating electric field (AEF) assisted freezing on the temperature histories and freezing parameters in different layers of beef as well as the freezing damage and myowater loss. The findings revealed distinct differences in the freezing curves (e.g., slope) and parameters (e.g., Tnuc, TF, tptand Fmiz) between the surface, middle, and inner layers of beef cubes under both AEF and traditional freezing conditions. AEF treatment regulated the freezing curves and key parameters of middle and surface layers, influencing ice crystallization. The equivalent ice areas for the surface, middle, and inner samples under AEF treatment were 8.16, 14.40, and 20.56%, respectively, significantly lower than those in traditional freezing (15.87, 24.60, and 28.8%). Compared to traditional freezing, AEF-assisted freezing decreased myofibrillar fragmentation index (MFI) of beef muscle, preserving its texture integrity. AEF treatment inhibited water migration and reduced water-holding capacity (WHC) loss. In conclusion, AEF-assisted freezing changed ice formation characteristics and alleviated freezing damage by regulating the freezing curve traits and parameters.