Multiphysics Modeling of Thorium-Based Fuel Performance With Cr-Coated SiC/SiC Composite Under Normal and Accident Conditions

Using the finite element multiphysics modeling method, the performance of the thorium-based fuel with Cr-coated SiC/SiC composite cladding under both normal operating and accident conditions was investigated in this work. First, the material properties of SiC/SiC composite and chromium were reviewed. Then, the implemented model was simulated, and the results were compared with those of the FRAPTRAN code to verify the correctness of the model used in this work. Finally, the fuel performance of the Th0.923U0.077O2 fuel, Th0.923Pu0.077O2 fuel, and UO2 fuel combined with the Cr-coated SiC/SiC composite cladding and Zircaloy cladding, respectively, was investigated and compared under both normal operating and accident conditions. Compared with the UO2 fuel, the Th0.923U0.077O2 and Th0.923Pu0.077O2 fuels were found to increase the fuel centerline temperature under both normal operating and reactivity-initiated accident (RIA) conditions, but decrease the fuel centerline temperature under loss-of-coolant accident (LOCA) condition. Moreover, compared to the UO2 fuel with the Zircaloy cladding, thorium-based fuels with Cr-coated SiC/SiC composite cladding were found to show better mechanical performance such as delaying the failure time by about 3 s of the Cr-coated SiC/SiC composite cladding under LOCA condition, and reducing the plenum pressure by about 0.4 MPa at the peak value in the fuel rod and the hoop strain of the cladding by about 16% under RIA condition

Assessing the structure and diversity of fungal community in plant soil under different climatic and vegetation conditions

IntroductionUnderstanding microbial communities in diverse ecosystems is crucial for unraveling the intricate relationships among microorganisms, their environment, and ecosystem processes. In this study, we investigated differences in the fungal community structure and diversity in soils from two contrasting climatic and vegetation conditions: the Xinjiang western China plateau and the Fujian southeastern coastal province.MethodsA total of 36 soil samples collected from two climatic regions were subjected to high-throughput ITS gene sequencing for fungal community analysis. In conjunction soil physicochemical properties were assessed and compared. Analyses included an examination of the relationship of fungal community structure to environmental factors and functional profiling of the community structure was using the FUNGuild pipeline.ResultsOur data revealed rich fungal diversity, with a total of 11 fungal phyla, 31 classes, 86 orders, 200 families, 388 genera, and 515 species identified in the soil samples. Distinct variations in the physicochemical properties of the soil and fungal community structure were seen in relation to climate and surface vegetation. Notably, despite a colder climate, the rhizosphere soil of Xinjiang exhibited higher fungal (α-)diversity compared to the rhizosphere soil of Fujian. β-diversity analyses indicated that soil heterogeneity and differences in fungal community structure were primarily influenced by spatial distance limitations and vegetation type. Furthermore, we identified dominant fungal phyla with significant roles in energy cycling and organic matter degradation, including members of the Sordariomycetes, Leotiomycetes, Archaeosporomycetes, and Agaricomycetes. Functional analyses of soil fungal communities highlighted distinct microbial ecological functions in Xinjiang and Fujian soils. Xinjiang soil was characterized by a focus on wood and plant saprotrophy, and endophytes, whereas in Fujian soil the fungal community was mainly associated with ectomycorrhizal interactions, fungal parasitism, and wood saprotrophy.DiscussionOur findings suggest fungal communities in different climatic conditions adapt along distinct patterns with, plants to cope with environmental stress and contribute significantly to energy metabolism and material cycling within soil-plant systems. This study provides valuable insights into the ecological diversity of fungal communities driven by geological and environmental factors

Seasonal Variations and Influencing Factors of Gross Nitrification Rate in Desert Steppe Soil

Nitrification plays an important role in nitrogen (N) turnover and N cycling. To date, there have been many studies on the net N turnover in grassland. However, few studies have specifically focused on the gross N turnover, which is mainly due to methodological limitations. Here, we set up an enclosed plot in a desert steppe and determined the gross nitrification (GN) rate of the soil by using the barometric process separation method. We found the seasonal dynamics of the GN in the desert steppe soil, such that the GN in the summer (117.65 ± 24.86 μg N kg−1 h−1) was significantly greater than in the spring and autumn (65.17 ± 7.33 μg N kg−1 h−1), and it peaked in July (213.75 ± 44.66 μg N kg−1 h−1). Additionally, the GN was lowest in the spring, with a means of 50.52 ± 3.95 μg N kg−1 h−1. The seasonal variation in the GN was different than the seasonal variation in the net nitrification rate, and the GN was generally much higher than the net nitrification rate. We further demonstrated that the soil moisture, temperature, bulk density and NH4+-N were the main factors that influenced the seasonal variations in the GN, and that the soil moisture had the greatest impact on the GN among all the factors measured

Effects of Warming and Precipitation on Soil CO2 Flux and Its Stable Carbon Isotope Composition in the Temperate Desert Steppe

The stable carbon (C) isotope of soil CO2 efflux (δ13CO2e) is closely associated with soil C dynamics, which have a complex feedback relationship with climate. Three levels of warming (T0: ambient temperature (15.7 °C); T1: T0 + 2 °C; T2: T0 + 4 °C) were combined with three levels of increased precipitation (W0: ambient precipitation (245.2 mm); W1: W0 + 25%; W2: W0 + 50%) in order to quantify soil CO2 flux and its δ13CO2e values under nine treatment conditions (T0W0, T0W1, T0W2, T1W0, T1W1, T1W2, T2W0, T2W1, and T2W2) in desert steppe in an experimental beginning in 2015. A non-steady state chamber system relying on Keeling plots was used to estimate δ13CO2e. The temperature (ST) and moisture (SM) of soil as well as soil organic carbon content (SOC) and δ13C values (δ13Csoil) were tested in order to interpret variations in soil CO2 efflux and δ13CO2e. Sampling was carried out during the growing season in 2018 and 2019. During the experiment, the ST and SM correspondingly increased due to warming and increased precipitation. CO2 flux ranged from 37 to 1103 mg m−2·h−1, and emissions peaked in early August in the desert steppe. Warming of 2 °C to 4 °C stimulated a 14% to 30.9% increase in soil CO2 efflux and a 0.4‰ to 1.8‰ enrichment in δ13CO2e, respectively. Increased precipitation raised soil CO2 efflux by 14% to 19.3%, and decreased δ13CO2e by 0.5‰ to 0.9‰. There was a positive correlation between soil CO2 efflux and ST and SOC indicating that ST affected soil CO2 efflux by changing SOC content. Although the δ13CO2e was positively correlated with ST, it was negatively correlated to SM. The decline of δ13CO2e with soil moisture was predominantly due to intensified and increased diffusive fractionation. The mean δ13CO2e value (−20.2‰) was higher than that of the soil carbon isotope signature at 0–20 cm (δ13Csoil = −22.7‰). The difference between δ13CO2e and δ13Csoil (Δe-s) could be used to evaluate the likelihood of substrate utilization. 13C enriched stable C pools were more likely to be utilized below 20 cm under warming of 2 °C in the desert steppe. Moreover, the interaction of T × W neither altered the CO2 emitted by soil nor the δ13CO2e or Δe-s, indicating that warming combined with precipitation may alleviate the SOC oxidation of soil enriched in 13C in the desert steppe

Effects of Warming and Precipitation on Soil CO₂ Flux and Its Stable Carbon Isotope Composition in the Temperate Desert Steppe

The stable carbon (C) isotope of soil CO2 efflux (δ13CO2e) is closely associated with soil C dynamics, which have a complex feedback relationship with climate. Three levels of warming (T0: ambient temperature (15.7 °C); T1: T0 + 2 °C; T2: T0 + 4 °C) were combined with three levels of increased precipitation (W0: ambient precipitation (245.2 mm); W1: W0 + 25%; W2: W0 + 50%) in order to quantify soil CO2 flux and its δ13CO2e values under nine treatment conditions (T0W0, T0W1, T0W2, T1W0, T1W1, T1W2, T2W0, T2W1, and T2W2) in desert steppe in an experimental beginning in 2015. A non-steady state chamber system relying on Keeling plots was used to estimate δ13CO2e. The temperature (ST) and moisture (SM) of soil as well as soil organic carbon content (SOC) and δ13C values (δ13Csoil) were tested in order to interpret variations in soil CO2 efflux and δ13CO2e. Sampling was carried out during the growing season in 2018 and 2019. During the experiment, the ST and SM correspondingly increased due to warming and increased precipitation. CO2 flux ranged from 37 to 1103 mg m−2·h−1, and emissions peaked in early August in the desert steppe. Warming of 2 °C to 4 °C stimulated a 14% to 30.9% increase in soil CO2 efflux and a 0.4‰ to 1.8‰ enrichment in δ13CO2e, respectively. Increased precipitation raised soil CO2 efflux by 14% to 19.3%, and decreased δ13CO2e by 0.5‰ to 0.9‰. There was a positive correlation between soil CO2 efflux and ST and SOC indicating that ST affected soil CO2 efflux by changing SOC content. Although the δ13CO2e was positively correlated with ST, it was negatively correlated to SM. The decline of δ13CO2e with soil moisture was predominantly due to intensified and increased diffusive fractionation. The mean δ13CO2e value (−20.2‰) was higher than that of the soil carbon isotope signature at 0–20 cm (δ13Csoil = −22.7‰). The difference between δ13CO2e and δ13Csoil (Δe-s) could be used to evaluate the likelihood of substrate utilization. 13C enriched stable C pools were more likely to be utilized below 20 cm under warming of 2 °C in the desert steppe. Moreover, the interaction of T × W neither altered the CO2 emitted by soil nor the δ13CO2e or Δe-s, indicating that warming combined with precipitation may alleviate the SOC oxidation of soil enriched in 13C in the desert steppe

Melatonin Rescued Reactive Oxygen Species-Impaired Osteogenesis of Human Bone Marrow Mesenchymal Stem Cells in the Presence of Tumor Necrosis Factor-Alpha

Accumulation of reactive oxygen species (ROS), which can be induced by inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), can significantly inhibit the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). This process can contribute to the imbalance of bone remodeling, which ultimately leads to osteoporosis. Therefore, reducing the ROS generation during osteogenesis of BMSCs may be an effective way to reverse the impairment of osteogenesis. Melatonin (MLT) has been reported to act as an antioxidant during cell proliferation and differentiation, but its antioxidant effect and mechanism of action during osteogenesis of MSCs in the inflammatory microenvironment, especially in the presence of TNF-α, remain unknown and need further study. In our study, we demonstrate that melatonin can counteract the generation of ROS and the inhibitory osteogenesis of BMSCs induced by TNF-α, by upregulating the expression of antioxidases and downregulating the expression of oxidases. Meanwhile, MLT can inhibit the phosphorylation of p65 protein and block the degradation of IκBα protein, thus decreasing the activity of the NF-κB pathway. This study confirmed that melatonin can inhibit the generation of ROS during osteogenic differentiation of BMSCs and reverse the inhibition of osteogenic differentiation of BMSCs in vitro, suggesting that melatonin can antagonize TNF-α-induced ROS generation and promote the great effect of osteogenic differentiation of BMSCs. Accordingly, these findings provide more evidence that melatonin can be used as a candidate drug for the treatment of osteoporosis

Effects of Warming and Increased Precipitation on Root Production and Turnover of <i>Stipa breviflora</i> Community in Desert Steppe

Organic carbon in grassland mainly exists in the soil, and root production and turnover play important roles in carbon input into the soil. However, the effects of climate change on plant root dynamics in desert steppe are unknown. We conducted an experiment in a desert steppe, which included ambient temperature (T0); temperature increased by 2 °C (T1); temperature increased by 4 °C (T2); natural precipitation (P0); precipitation increased by 25% (P1); precipitation increased by 50% (P2); and the interaction between warming and increased precipitation. Plant community aboveground characteristics; root production; and root turnover were measured. We found that the root length production of the T0P2; T1P1; T2P0; and T2P1 treatments were significantly higher than that of the T0P0 treatment, with an increment of 98.70%, 11.72%, 163.03%, and 85.14%, respectively. Three treatments with temperature increased by 2 °C (T1P0; T1P1; and T1P2) and significantly increased root turnover rate compared to the T0P0 treatment, with increases of 62.53%, 42.57%, and 35.55%, respectively. The interaction between warming and increased precipitation significantly affected the root production of the community (p < 0.01), but this interaction was non-additive. Future climate warming will benefit the accumulation of root-derived carbon in desert steppe communities

Melatonin Reverses the Loss of Stemness Induced by TNF-α in Human Bone Marrow Mesenchymal Stem Cells through Upregulation of YAP Expression

Mesenchymal stem cells (MSCs) are promising candidates for tissue regeneration and disease treatment. However, long-term in vitro culture results in loss of MSC stemness. The inflammation that occurs at stem cell transplant sites (such as that resulting from TNF-α) is a contributing factor for stem cell treatment failure. Currently, there is little evidence regarding the protective role of melatonin with regard to the negative effects of TNF-α on the stemness of MSCs. In this study, we report a melatonin-based method to reduce the inflammatory effects on the stemness of bone marrow mesenchymal stem cells (BMMSCs). The results of colony formation assays, Alizarin red staining, western blotting, and reverse transcription-polymerase chain reactions suggest that melatonin can reverse the inflammatory damage caused by TNF-α treatment in the third, seventh, and tenth generations of primary BMMSCs (vs. control and the TNF-α-treated group). Meanwhile, a detailed analysis of the molecular mechanisms showed that the melatonin receptor and YAP signaling pathway are closely related to the role that melatonin plays in negative inflammatory effects against BMMSCs. In addition, in vivo experiments showed that melatonin could reverse the damage caused by TNF-α on bone regeneration by BMMSCs in nude mice. Overall, our results suggest that melatonin can reverse the loss of stemness caused by inflammatory factor TNF-α in BMMSCs. Our results also provide a practical strategy for the application of BMMSCs in tissue engineering and cell therapy

Spatial-Temporal Changes and Driving Factors of Land-Use Eco-Efficiency Incorporating Ecosystem Services in China

With rapid urbanization in China, the dramatic land-use changes are one of the most prominent features that have substantially affected the land ecosystems, thus seriously threatening sustainable development. However, current studies have focused more on evaluating the economic efficiency of land-use, while the loss and degradation of ecosystem services are barely considered. To address these issues, this study first proposed a land use-based input–output index system, incorporating the impact on ecosystem services value (ESV), and then by taking 30 provinces in China as a case study. We further employed the super-efficiency slacks-based model (Super-SBM) and the Stochastic Impacts by Regression on Population, Affluence and Technology (STIRPAT) model to explore the spatial–temporal changes and driving factors of the evaluated land-use eco-efficiency. We found that the evaluated ESV was 28.09 trillion yuan (at the price of 2000) in 2015, and that the total ESV experienced an inverted U-shaped trend during 2000–2015.The average land-use eco-efficiency exhibited a downward trend from 0.87 in 2000 to 0.68 in 2015 with distinct regional differences by taking into account the ESV. Our results revealed that northeastern region had the highest efficiency, followed by the eastern, western, and central region of China. Finally, we identified a U-shaped relationship between the eco-efficiency and land urbanization, and found that technological innovation made great contributions to the improvement of the eco-efficiency. These findings highlight the importance of the ESV in the evaluation of land-use eco-efficiency. Future land development and management should pay additional attention to the land ecosystems, especially the continuous supply of human well-being related ecosystem services

Spatial-Temporal Changes and Driving Factors of Land-Use Eco-Efficiency Incorporating Ecosystem Services in China

With rapid urbanization in China, the dramatic land-use changes are one of the most prominent features that have substantially affected the land ecosystems, thus seriously threatening sustainable development. However, current studies have focused more on evaluating the economic efficiency of land-use, while the loss and degradation of ecosystem services are barely considered. To address these issues, this study first proposed a land use-based input&ndash;output index system, incorporating the impact on ecosystem services value (ESV), and then by taking 30 provinces in China as a case study. We further employed the super-efficiency slacks-based model (Super-SBM) and the Stochastic Impacts by Regression on Population, Affluence and Technology (STIRPAT) model to explore the spatial&ndash;temporal changes and driving factors of the evaluated land-use eco-efficiency. We found that the evaluated ESV was 28.09 trillion yuan (at the price of 2000) in 2015, and that the total ESV experienced an inverted U-shaped trend during 2000&ndash;2015.The average land-use eco-efficiency exhibited a downward trend from 0.87 in 2000 to 0.68 in 2015 with distinct regional differences by taking into account the ESV. Our results revealed that northeastern region had the highest efficiency, followed by the eastern, western, and central region of China. Finally, we identified a U-shaped relationship between the eco-efficiency and land urbanization, and found that technological innovation made great contributions to the improvement of the eco-efficiency. These findings highlight the importance of the ESV in the evaluation of land-use eco-efficiency. Future land development and management should pay additional attention to the land ecosystems, especially the continuous supply of human well-being related ecosystem services