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Complex Network Model of Global Financial Time Series Based on Different Distance Functions
No full textBy constructing a complex network model grounded in time series analysis, this study delves into the intricate relationships between the stock markets of 18 countries worldwide. Utilizing 31 distinct time series distance functions to formulate the network, we employ Hamming distance to quantify the resemblance between networks derived from different distance functions. By modulating the network density through distance percentiles (p=0.1, 0.3, 0.5), we demonstrate the similarity of various distance functions across multiple density levels. Our findings reveal that certain distance functions exhibit high degrees of similarity across varying network densities, suggesting their potential for mutual substitution in network construction. Furthermore, the centroid network identified via hierarchical cluster analysis highlights the similarities between the stock markets of different nations, mirroring the intricate interconnections within the global financial landscape. The insights gained from this study offer crucial perspectives for comprehending the intricate network structure of global financial time series data, paving the way for further analysis and prediction of global financial market dynamics
Effects of Vegetation Restoration Age on Soil C: N: P Stoichiometry in Yellow River Delta Coastal Wetland of China
No full textVegetation restoration can alter carbon (C), nitrogen (N), and phosphorus (P) cycles in coastal wetlands affecting C: N: P stoichiometry. However, the effects of restoration age on soil C: N: P stoichiometry are unclear. In this study, we examined the responses of soil C, N, and P contents and their stoichiometric ratios to vegetation restoration age, focusing on below-ground processes and their relationships to aboveground vegetation community characteristics. We conducted an analysis of temporal gradients based on the 'space for time' method to synthesize the effects of restoration age on soil C: N: P stoichiometry in the Yellow River Delta wetland of China. The findings suggest that the combined effects of restoration age and soil depth create complex patterns of shifting soil C: N: P stoichiometry. Specifically, restoration age significantly increased all topsoil C: N: P stoichiometries, except for soil total phosphorus (TP) and the C: N ratio, and slightly affected subsoil C: N: P stoichiometry. The effects of restoration age on the soil C: N ratio was well constrained owing to the coupled relationship between soil organic carbon (SOC) and total nitrogen (TN) contents, while soil TP content was closely related to changes in plant species diversity. Importantly, we found that the topsoil C: N: P stoichiometry was significantly affected by plant species diversity, whereas the subsoil C: N: P stoichiometry was more easily regulated by pH and electric conductivity (EC). Overall, this study shows that vegetation restoration age elevated SOC and N contents and alleviated N limitation, which is useful for further assessing soil C: N: P stoichiometry in coastal restoration wetlands
Unveiling microplastic's ' s role in nitrogen cycling: Metagenomic insights from estuarine sediment microcosms
No full textMarine microplastics (MPs) pollution, with rivers as a major source, leads to MPs accumulation in estuarine sediments, which are also nitrogen cycling hotspots. However, the impact of MPs on nitrogen cycling in estuarine sediments has rarely been documented. In this study, we conducted microcosm experiment to investigate the effects of commonly encountered polyethylene (PE) and polystyrene (PS) MPs, with two MPs concentrations (0.3% and 3% wet sediment weight) based on environmental concentration considerations and dose-response effects, on sediment dissolved oxygen (DO) diffusion capacity and microbial communities using microelectrode system and metagenomic analysis respectively. The results indicated that high concentrations of PE-MPs inhibited DO diffusion during the mid-phase of the experiment, an effect that dissipated in the later stages. Metagenomic analysis revealed that MP treatments reduced the relative abundance of dominant microbial colonies in the sediments. The PCoA results demonstrated that MPs altered the microbial community structure, particularly evident under high concentration PE-MPs treatments. Functional analysis related to the nitrogen cycle suggested that PS-MPs promoted the nitrification, denitrification, and DNRA processes, but inhibited the ANRA process, while PE-MPs had an inhibitory effect on the nitrate reduction process and the ANRA process. Additionally, the high concentration of PE-MPs treatment significantly stimulated the abundance of genus (Bacillus) by 34.1% and genes (lip, pnbA) by 100-187.5% associated with plastic degradation, respectively. Overall, in terms of microbial community structure and the abundance of nitrogen cycling functional genes, PEand PS- MPs exhibit both similarities and differences in their impact on nitrogen cycling. Our findings highlight the complexity of MP effects on nitrogen cycling in estuarine sediments and high concentrations of PE-MP stimulated plastic-degrading genus and genes
Seasonal precipitation distribution determines ecosystem CO<sub>2</sub> and H<sub>2</sub>O exchange by regulating spring soil water-salt dynamics in a brackish wetland
No full text1. The intensification of the global hydrological cycle is anticipated to increase the variability of precipitation patterns. Brackish wetlands respond to changes in precipitation patterns by regulating the absorption and release of CO2 and H2O to maintain the stability of ecosystem functions. However, there is limited understanding of how the inter-seasonal precipitation distribution (SPD) affects ecosystem CO2 and H2O exchange compared with annual precipitation totals. 2. Here, we conducted four consecutive years of field experiments in a brackish wetland, manipulating the proportion of precipitation across different seasons while maintaining a constant annual precipitation total. We utilized five inter-SPD proportions (+73%, +56%, control (CK), -56%, -73%) to examine the effects of SPD on ecosystem CO2 and H2O exchange. 3. Our findings revealed that the annual ecosystem CO2 and H2O fluxes showed a trend of decreasing with the decrease in spring precipitation distribution. Among them, the annual net ecosystem CO2 exchange, evapotranspiration, carbon use efficiency and water use efficiency were shown to be more sensitive to decrease in spring precipitation distribution and increase in summer and autumn precipitation distribution. This negative asymmetric response pattern suggests that annual ecosystem CO2 and H2O exchange is primarily governed by seasonal precipitation variability, with spring soil water-salt dynamics identified as the key driver. Therefore, this association can be explained by the fact that drought of the early growth stage exacerbates soil salinization and inhibits vegetation colonization and growth, thereby greatly impairing the annual CO2-H2O exchange capacity of brackish wetlands. 4. Our results emphasized that the spring extreme precipitation-induced soil water-salt conditions will greatly influence CO2 and H2O exchange in brackish wetlands in the future. These findings are crucial for improving predictions of the carbon sequestration and water-holding capacity of brackish wetlands. Read the free Plain Language Summary for this article on the Journal blog
Moderate nitrogen enrichment increases CO2 sink strength in a coastal wetland
No full textAbstract
Coastal wetlands remarkably influence terrestrial carbon (C) stock by serving as natural reservoirs for ‘blue carbon’. Anthropogenic nitrogen (N) enrichment shapes the dynamics of soil and plant communities, consequently affecting the C balance and ecosystem functions. The impacts of various levels of N enrichment on CO2 sequestration in coastal wetlands, however, remain elusive. Here we conducted a long-term field study of N fertilization in a coastal wetland in the Yellow River Delta, China, to investigate N effects on soil properties, indicators of plant dynamics, and fluxes of ecosystem CO2. The results indicated that moderate N enrichment (5 g N m?2 y?1) stimulated C fluxes with increases in gross primary productivity (+26.4%), ecosystem respiration (+23.3%), and net ecosystem exchange (NEE, +31.5%) relative to the control. High (10 g N m?2 y?1) and extreme (20 g N m?2 y?1) amounts of N enrichment, however, had relatively minor impacts on these CO2 fluxes. Overall, we observed a decrease in soil electrical conductivity (?24.6%) and increases in soil organic C (+25.2%) and microbial biomass C (+369.3%) for N enrichment. N enrichment also altered the composition of plant species, with a higher proportion of a local dominant species (Phragmites australis), and affected root biomass distribution, with more biomass near the soil surface. Structural equation modeling explained 65.2% of the variance of NEE and supported the assumption that N enrichment could alter the dynamics of soil properties and plant conditions and accelerate ecosystem CO2 sequestration. These findings have important implications for forecasting the C cycle with increasing N deposition in coastal wetlands, contributing to the projections of the global C budget
Potentiometric/time resolved chronopotentiometric sensing for an all-solid-state ion-selective electrode based on MXene/MWCNTs as solid contact
No full textSolid-contact polymeric membrane ion-selective electrodes (ISEs) have been an attractive tool for potentiometric sensors. Sufficient transducing performance evaluation and multiple potentiometric analysis are critical to evaluate whether the solid contact transducer material used in ISE is promising. Herein, we describe sandwichlike MXene/MWCNTs-based polymeric membrane ISEs with three-readout strategies of potential response, chronopotentiometric response, and transition time response. The MXene/MWCNTs can be readily prepared by the electrostatic self-assembly strategy, which not only prevented the aggregation of MXene nanosheets and facilitated charge-transfer, but also significantly contributed to the large double-layer capacitance and waterlayer free from interference. With Ca2+ as a model, two kinds of Ca2+-ISEs based on thermodynamic response and dynamic response by modulating the polymeric membrane components with three readouts were explored. Moreover, the proposed Ca2+-ISEs under different background electrolytes exhibit the similar Nernstian responses in potentiometry, variable super-Nernstian ranges in chronopotentiometry, and the consistent transition time readout. This study offers a facile MXene/MWCNTs transducer to develop a highly reliable polymeric membrane ISE
Characterizing and decoding the key odor compounds of Spirulina platensis at different processing stages by sensomics
No full textProcessing is an indispensable technology in the preparation of Spirulina platensis (S. platensis). The key odorants in liquids, muds, and powders from S. platensis (NM and GZ) were characterized. A total of 90 odorants were identified and 41 odorants were sniffed with the flavor dilution (FD) factors ranging from 1 to 729. Among them, nonanal, decanal, D-limonene, J3-cyclocitral, and J3-ionone with FD factors >= 1 were detected in S. platensis during the whole processing stages. In addition, heptanal, (E, E)-2,4-nonadienal, trans-4,5-epoxy-(E)-2-decenal, 1hepten-3-one, isophorone, 3-ethyl-2,5-dimethylpyrazine, and alpha-ionone exhibited higher odor activity values in powders; J3-myrcene, methional, and S-methyl methanethiosulphonate were key odorants in muds; while trans-3penten-2-ol was key odorant in liquids. Besides, the GZ-mud presented stronger earthy and fishy odor than NMmud. S. platensis powders have the stronger grassy odor, roasted odor, and marine odor than S. platensis muds. Overall, drying process promotes the formation of aldehydes, heterocyclic compounds, and terpenoids
Albifimbrins A and B, a pair of epimeric tetrahydrofuran-containing linear polyketide derivatives from the marine-derived fungus<i> Albifimbria</i> verrucaria CD1-4
No full textA pair of new epimeric polyketides, named albifimbrins A and B (1 and 2), were isolated from the cultures of the shellfish-derived fungus Albifimbria verrucaria CD1-4. Their structures were determined by extensive spectroscopic analysis including HR-MS, 1D and 2D NMR data, together with the CD exciton chirality method. Compounds 1 and 2 possess unusual tetrahydrofuran moiety in their linear molecule structures. The antimicroalgal assay indicated that compounds 1 and 2 shown moderate inhibitory activities against marine harmful micro-algae, Prorocentrum donghaiense, Amphidinium carterae and Heterocapsa circulariaquama
Pore connectivity and anisotropy affect carbon mineralization via extracellular enzymes in > 2 mm aggregates under conservation tillage of Mollisols
No full textSoil aggregates, which are the basic units of soil structure, play an important role in the carbon cycle of ecosystems. The pore characteristics of aggregates influence soil organic carbon sequestration. However, studies on SOC mechanisms in aggregates have been limited to Mollisols. This study was conducted as a long-term experiment established in 2004 with a corn-soybean rotation in Mollisols. There are three treatments, including rotary tillage without straw return (conventional tillage, CT), subsoiling without straw return (reduced tillage, RT), and no tillage with straw return (NT). The soil pore size distribution, shape parameters, extracellular enzymes activity, and carbon mineralization were measured. The results showed that 15-year no tillage and reduced tillage increased the total porosity and proportion of larger pores, but significantly decreased the proportion of smaller pores in situ soil columns. Conventional tillage exhibited the most complex pores because of the highest pore fractal dimension (2.75-2.90), anisotropy (0.366-0.516), and the lowest sphericity (5.1-28.7). As for the soil columns filled with > 2 mm aggregates, reduced tillage significantly increased the pore connectivity by 3.02-3.62 %, whereas no tillage had no effect. The structural equation modelling indicated that in soil columns filled with > 2 mm aggregates, pore shape parameters, particularly connectivity and anisotropy, positively influenced the activities of beta-glucosidase and beta-xylosidase directly, and positively affected soil carbon mineralization by influencing extracellular enzymes activity indirectly. The findings emphasize the importance of pore shape parameters effect on soil carbon sequestration, and will be helpful in comprehending the microscopic mechanisms of soil carbon sequestration in > 2 mm aggregates
Population Genetics Analysis and Sex GWAS of <i>Hemicentrotus pulcherrimus</i>
No full textHemicentrotus pulcherrimus is an important commercial aquatic species. However, wild stocks have dramatically decreased in recent decades, and the gonads of H.pulcherrimus of different sexes showed significant differences in gonad index, gonad color, and flavour. Understanding the population genetic structure and sex-differentiation/determination mechanism can provide vital information for genetic conservation and improvement. In the present study, the SuperGBS method was used to identify genome-wide SNPs from a collection of 80 individuals consisting of four geographical populations covering the natural habitats of H. pulcherrimus in China seas. A total of 5785 high-quality SNPs were detected by using SuperGBS technology. The genetic diversity index showed that all populations had similar patterns with high F-is and low N-e, suggesting that it is necessary to carry out the conservation of H. pulcherrimus in China. Low genetic differentiation among the four geographical populations was detected by pairwise F-st, PCA, and admixture analysis. In addition, three sex-related SNPs located on three scaffolds were identified, suggesting a ZW-ZZ sex determination system in H. pulcherrimus. However, no sex-specific marker was identified in this study. Therefore, larger sample sizes and marker numbers need to be implemented to investigate the sex-associated markers and genes of H. pulcherrimus. In general, this study provides a molecular basis for population genetic structure and sex-differentiation/determination mechanism of H. pulcherrimus