Search Results (994)

The study of degradation processes is of fundamental and applied interest. To understand the degradation of cellulose nitrate and to develop sensitive diagnostic methods, combined experimental and theoretical investigations are essential. Sensitive, non-destructive, and contactless methods for diagnosing the state of cellulose nitrate include IR absorption and Raman spectroscopy. While significant experimental work exists, the theoretical modeling of degradation processes, including the prediction of potential products, remains underdeveloped. Therefore, in this work, the structures and vibrational properties of molecular clusters representing segments of the cellulose nitrate chain were modeled using density functional theory (DFT). This approach yielded simulated IR and Raman spectra, allowing for the identification of peaks corresponding to the nitrate group. The elimination of this group to form a ketone was shown to alter peak contours across a broad spectral range. The most significant changes in the Raman spectra were observed at 605 and 851 cm⁻¹. Correspondingly, the key changes in the IR absorption spectra occurred at 836, 1034, 1169, 1283, and 1767–1781 cm⁻¹. The frequency trends for these diagnostic peaks across different model structures were analyzed and compared with experimental spectra from the literature. The demonstrated correlation between specific peak-frequency changes and the modeled degradation products constitutes the principal novelty of this work. Full article

The spatial variation in acidity, organic matter, nitrate nitrogen, and mobile forms of phosphorus and potassium in the arable horizon (0–20 cm) of southern chernozems was studied in the Fedorovsky, Denisovsky, Altynsarin, and Karasu districts of the Kostanay region. The arable horizons were predominantly alkaline (pH (H₂O) 7.6–8.0) to strongly alkaline (pH (H₂O) above 8.0); organic matter content was low (2–4%); nitrate nitrogen (N-NO₃) and mobile P₂O₅ were very low (less than 10 mg/kg), and mobile K₂O was high (400–700 mg/kg). The spatial distributions of pH (H₂O), organic matter, and K₂O were normal, whereas those of N-NO₃ and P₂O₅ were lognormal. Hierarchical analysis of variance showed that variability within plots of 0.5 km² accounted for a significant proportion of the total variance of the soil properties. Variation between fields (1–3 km²) within farms (10–40 km²) was most pronounced for nitrate nitrogen and mobile phosphorus, whereas for pH (H₂O) and mobile potassium the differences between districts (1000–7500 km²) prevailed. Significant correlations between the soil properties and their dependence on the latitude and longitude of the sampling points were revealed in the moderately arid steppes of the Kostanay region. Full article

Coptotermes formosanus is an economically significant termite species with a highly organised caste system, in which division of labour underpins colony function. Although gut microbiota is widely recognised for its roles in host nutrition and adaptation, much less is known about how these microbial communities are structured across castes. To explore caste-related gut bacterial variation in C. formosanus, we analysed the community structure of both workers and soldiers using high-throughput amplicon sequencing targeting the bacterial 16S rRNA gene. Although both castes were dominated by Bacteroidota and Spirochaetota, which together accounted for 78.87% to 85.78% in workers and 63.31% to 84.38% in soldiers, significant caste-associated differences were evident. Workers showed significantly higher bacterial richness, as indicated by observed ASVs, Chao1 indices, and Faith’s PD. Further clear caste-associated bacterial community was revealed by beta-diversity analysis. Differential taxonomic analysis revealed distinct caste-associated enrichment patterns. In addition, co-occurrence network analysis indicated a caste-associated interaction structure, with soldier-biased taxa forming a dense, highly connected module while worker-biased taxa contributed to local structure and bridging positions. Furthermore, chemoheterotrophy and fermentation were predicted to be enriched in workers, whereas nitrate reduction, aerobic chemoheterotrophy, aromatic compound degradation, and phenotypes related to biofilm formation, stress tolerance, and mobile elements were predicted to be relatively enriched in soldiers. Moreover, qPCR analysis further showed caste-associated differences in dominant gut protists, with Pseudotrichonympha in workers significantly higher than in soldiers and positively correlated with Azobacteroides. These results provide clear evidence of caste-associated differentiation in gut microbial composition and offer a foundation for identifying novel microbial targets for termite pest management. Full article

Heterotrophic denitrification is increasingly used in land-based recirculating aquaculture systems (RASs) to remove nitrate and minimise new-water demand, but the carbon sources traditionally used—methanol and acetic acid—raise safety, corrosion, and cost concerns. This study evaluated glycerol as an alternative external carbon source in a commercial land-based Atlantic salmon RAS in Norway. Trials in two identical post-smolt systems with integrated denitrification bioreactors compared glycerol (80%) against acetic acid for denitrification performance, nitrite accumulation, pH stability, carbon-source consumption, cost, and hazard profile. Glycerol achieved similar or higher apparent total dissolved nitrogen (TDN) removal than acetic acid and, once the biofilm had acclimated, was completely consumed. It maintained a stable outlet pH (≥6.5), avoiding the enzyme inhibition seen when acetic acid depressed pH, and proved about 1.5 times more cost-effective (≈NOK 66 vs. 97 per kg TDN removed). A standardised hazard assessment ranked glycerol as the safest option for flammability, toxicity, and corrosiveness. TDN removal correlated strongly with dissolved nitrogen gas saturation at the bioreactor outlet (r² = 0.79–0.82), indicating that total gas pressure monitoring is a promising, low-cost proxy for performance. Nitrite accumulation per unit of nitrogen removed was, however, about three times higher under glycerol (≈1 mg NO₂-N per mg TDN) than under acetic acid (≈0.3 mg NO₂-N per mg TDN), and the nine-day glycerol phase was too short to establish whether this resolves or persists as the biofilm matures. Subject to routine nitrite monitoring in the fish tanks, glycerol is a cost-effective, low-hazard, and pH-stable alternative to acetic acid for nitrate removal in salmon RASs. Full article

Banana Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (FOC), poses a major threat to global banana production. Straw submergence combined with rice rotation (SFR) has emerged as a promising disease-management strategy, but its underlying mechanisms remain unclear. Here, we conducted a three-year field experiment to determine how SFR alters soil physicochemical properties, microbial communities, and soil metabolites. SFR sharply decreased soil redox potential (Eh) and shifted nitrogen transformation by increasing ammonium nitrogen (AN) and reducing nitrate nitrogen (NN). Eh and NN were positively correlated with culturable Fusarium spp. counts (r = 0.36, p < 0.01), whereas AN was negatively correlated. SFR also reshaped soil microbial communities, reduced the relative abundance of Fusarium, and enriched several putatively antagonistic microbial taxa. Metabolomic profiling showed that several Fusarium-associated metabolites were downregulated and that differential metabolites were enriched in key KEGG pathways. Network analysis further identified Luteimonas as a potential keystone bacterial genus negatively associated with Fusarium-associated metabolites. Partial least squares path modeling suggested that soil physicochemical changes were linked to Fusarium wilt suppression largely through indirect bacterial–fungal–metabolite pathways. These findings indicate that SFR suppresses banana Fusarium wilt, reducing disease incidence to 16.25% at the vigorous growth stage (versus 100% in SC), an 83.8% relative reduction compared with banana monoculture, through coordinated changes in soil Eh and nitrogen status, microbial community structure, and soil metabolic profiles. Full article

Moss-dominated biological soil crusts are associated with carbon and nitrogen cycling in dryland and alpine sandy ecosystems, but functional differentiation among closely related moss species and their mixed assemblages remains unclear. We used shotgun metagenomic sequencing to compare below-crust soil associated with Didymodon constrictus (Mitt.) K. Saito (D. constrictus) crusts (mossC), ferrugineus (Schimp. ex Besch.) M.O. Hill (D. ferrugineus) crusts (mossF), and visually co-dominated mixed crusts (mossM) in the Gonghe Basin on the northeastern Qinghai–Tibet Plateau. Fifteen spatially separated quadrats per category were pooled into three composite biological replicates (effective n = 3). KEGG, CAZy, and targeted carbon- and nitrogen-cycling annotations showed category-associated differences in relative gene representation. MossC had greater mean representation of glycoside hydrolases and several complex-carbon-processing functions, mossF had greater representation of nitrogen-assimilation and acetate-related functions, and mossM had greater representation of selected carbon-degradation, nitrogen-mineralization, and dissimilatory-nitrate-reduction functions. The full RDA model explained 58.4% of functional variation (adjusted R² = 0.334; exact permutation p = 0.028340), with single-variable associations retained for total carbon and soil water content. Genus-level taxonomic dissimilarity correlated with KEGG, CAZy, carbon-cycling, and nitrogen-cycling dissimilarities after FDR correction. MossM showed both positive and negative descriptive deviations from the approximate unweighted midpoint of mossC and mossF, but no inferential test was applied to these deviations. The small number of composite replicates, visually estimated moss proportions, edaphic confounding, and absence of activity measurements limit causal and confirmatory interpretation. Full article

Background: Gestational tobacco exposure is a major modifiable risk factor for adverse pregnancy outcomes; how smoking-induced redox perturbations transmit across the placental barrier to the fetal compartment, and mediate neonatal outcomes, remains incompletely understood. Methods: In a prospective cohort of 66 maternal-neonatal dyads (24 smokers, 42 non-smokers) from Târgu-Mures, six redox biomarkers (nitrite, nitrate, malondialdehyde, reduced, oxidized glutathione (GSH, GSSG) and GSH/GSSG ratio) were quantified in paired maternal and cord blood and converted to SI units, and pathway-specific composite indices (oxidative and nitrosative stress index–OSI, NSI, global redox index–GRI) were derived via standardized Z-scores of natural-log-transformed concentrations. Associations with preterm birth (PTB) and low birth weight (LBW) were assessed via multivariable regression. Benjamini–Hochberg false discovery rate (FDR) correction was applied within predefined test families. Results: Tobacco exposure was associated with nominally significant depletion of the Neonatal NSI (mean difference = −0.842; 95% CI: −1.567 to −0.117; p = 0.024; FDR-adjusted p = 0.142), while maternal indices showed no significant group differences. Lower Maternal GRI and Neonatal NSI were independently associated with lower birth weight and higher odds of preterm birth (aOR = 0.35 and 0.52, respectively; both p < 0.05). Maternal and neonatal nitrite concentrations were positively correlated (FDR-adjusted p = 0.002) and oxidized glutathione showed an inverse maternal-neonatal correlation (FDR-adjusted p = 0.001), whereas the maternal and neonatal NSI was not significant after FDR-correction (FDR-adjusted p = 0.078) Conclusions: Gestational tobacco exposure was associated with depletion of the neonatal nitrosative stress index. Independently, lower maternal and neonatal composite redox indices were associated with lower birth weight and higher odds of preterm birth. Composite indices may offer an integrated assessment of perinatal redox status, but without external validation warrant confirmation in larger cohorts. Full article

Rhizosphere microorganisms play critical roles in biogeochemical processes including carbon cycling; however, their linkages to carbon-cycling functions under distinct mine restoration approaches remain unclear. In this study, we compared natural and artificial vegetation restoration via metagenomic sequencing to characterize rhizosphere microbial communities and carbon-cycling functional genes. Artificial restoration (AR) decreased soil electrical conductivity (EC) and salt content (SC) while increasing total phosphorus and available phosphorus by 12.33% and 16.44%, respectively. AR also elevated the relative abundances of genes responsible for degrading aromatic compounds, lignin and starch, along with genes participating in carbon-fixation pathways. Taxa of the Actinomycetia, Chloroflexi, and Solirubrobacterales served as the primary contributors to genes encoding 2-isopropylmalate synthase, α-glucosidase, malate synthase, and α-mannosidase, as well as carbon-fixation-related genes, including aconitate hydratase (ACO), methylmalonyl-CoA mutase subunit (E5.4.99.2A), pyruvate orthophosphate dikinase (ppdK), and phosphoenolpyruvate carboxylase (ppc). Moreover, the relative abundances of carbon-fixation genes exhibited significant positive correlations with EC, SC, nitrate nitrogen (NO₃⁻-N) and ammonium nitrogen (NH₄⁺-N). Overall, microorganisms in AR soils hold relatively high genetic potential for carbon sequestration and decomposition. Such rhizosphere carbon-cycling functions are jointly shaped by restoration strategies and vegetation community composition, and our findings offer key theoretical support for mine ecological restoration. Full article

Background/Objectives: Perinatal oxidative and nitrosative stress may contribute to maternal–neonatal adaptation during delivery. This pilot study evaluated pathway-specific oxidative and nitrosative stress markers from blood samples in paired mother–newborn dyads and explored their associations with delivery-related variables, maternal smoking habits and neonatal clinical state. Methods: The study included 74 mother–newborn dyads, yielding 148 paired maternal and neonatal investigations. Biomarkers included plasma nitrite, nitrate, malondialdehyde, and reduced and oxidized glutathione. Composite pathway-specific indices were calculated: an Oxidative Stress Index (OSI) and a Nitrosative Stress Index (NSI). Results: Paired testing showed that OSI was significantly higher in the maternal compartment compared to the neonatal compartment (p < 0.001), while NSI showed no significant difference (p = 0.594). Maternal and neonatal indices showed positive monotonic correlations (OSI Spearman’s rho = 0.608, p < 0.001; NSI Spearman’s rho = 0.275, p = 0.018). Following false discovery-rate correction (FDR) across the exploratory inferential analysis, no raw or composite biomarkers showed statistically significant differences. Conclusions: This study indicates that while maternal and neonatal oxidative indices are monotonically correlated, their absolute concentrations shift significantly across compartments, highlighting the need to treat these indices as strictly exploratory, hypothesis-generating metrics. Full article

Reactive oxygen and nitrogen species (RONS) generated by medical gas plasmas are considered major mediators of plasma-induced biological effects. This includes the atmospheric pressure argon plasma jet kINPen routinely used in clinical applications. The jet’s biomedical action has been shown to be tailored by modifying its feed gas. However, a systematic comparison of how feed gas composition and humidity shape plasma chemistry remains lacking, which would shift application-specific plasma chemistries from guessing to designing. In this study, we systematically investigated, compared, and statistically related 65 individual feed gas conditions of the kINPen argon plasma jet by increasing O₂, N₂, and combined O₂ + N₂ admixtures under dry and humidified conditions. Plasma gas phases were assessed using optical emission spectroscopy and reactive species produced in liquid via hydrogen peroxide, nitrite, and nitrate quantification. O₂-containing admixtures generally reduced overall plasma emission and liquid-phase RONS accumulation, whereas N₂-containing admixtures preferentially enhanced nitrogen-associated emission features. Water vapor addition via the admixture gas stream acted as an important secondary tuning parameter, exerting the strongest effects under combined O₂ + N₂ conditions. Multivariate analyses confirmed clear separation of chemistry profiles according to feed gas composition and humidity, while correlation and regression analyses identified several condition-dependent relationships between gas-phase emissions and liquid-phase reaction products. These data provide a comprehensive characterization of kINPen plasma chemistry under controlled feed gas modification and establish a reference framework for tailoring plasma-derived reactive species profiles in future plasma biology and medicine studies. Full article

(1) Background: The diversity and compositional structure of a soil’s microbial community play important roles in the function of the whole soil environment, making them important indicators of soil quality. Poplars grow rapidly, have broad adaptability, strong resistance, and significant ecological benefits, making them the primary timber species in northern China. This study aims to explore the differences and similarities among soil microbial communities of different poplar varieties by investigating the effects of soil factors on various poplar species, as well as the composition and diversity of their soil microbiomes, which holds practical significance. (2) Methods: In this experiment, soil samples from four different poplar varieties (YA: Populus × euramericana ‘102’; YB: Populus × euramericana ‘Guariento’; YC: Populus cathayana × canadensis ‘Xinlin 1’; YD: Populus × liaoningensis) were selected for the determination of their microbial communities, soil chemical properties and enzyme activities. (3) Results: Significant differences (p < 0.05) were observed among the four poplar varieties in ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), total nitrogen (TN), total carbon (TC), total phosphorus (TP), available phosphorus (AP), invertase (INV), amylase (AMY), urease (URE), neutral phosphatase (NEP) and N-acetyl-β-D-glucosaminidase (NAG). Additionally, strong correlations were observed between soil factors and microorganisms, particularly with TP, AP, NEP and URE. (4) Conclusions: Soil chemical properties and enzyme activities significantly affect both poplar growth and microbial community structure, though the impacts vary. There are both similarities and differences in the composition and diversity of soil microbial communities across different poplar varieties. Full article

The groundwater resources are increasingly stressed in the Islamabad–Rawalpindi metropolitan area of Pakistan due to unplanned urbanization, growth of industries, and inadequate waste management. In this study, the aquifer vulnerability was evaluated in the productive alluvial zone of Islamabad Watershed using a Geographic Information System (GIS)-based DRASTIC model and critically comparing it with independent measured contamination of groundwater, which is a common weakness in many machine-learning-based DRASTIC studies considering the vulnerability index as the model input. The data from 21 boreholes supplied by the Capital Development Authority (CDA) were used to map seven hydrogeological parameters in ArcGIS Pro at a 30 m resolution. The DRASTIC Index values ranged from 69 to 188, with 12.9% of the mapped watershed (209.3 km²) being rated as Very High vulnerability, mainly in the shallow western urban alluvium where water tables are below 5 m. Single-parameter sensitivity analysis showed that the most influential factors of the index were impact of the vadose zone (S_i = 1.14) and depth to water table (S_i = 1.09). A Random Forest model was trained on independently measured nitrate instead of the DRASTIC Index, but had a poor predictive skill (cross-validated R² = 0.08), and the SHapley Additive exPlanations (SHAP) analysis suggested that increased vulnerability (shallow water table and high recharge) was correlated with lower nitrate concentrations. The inverse relationship between groundwater intrinsic vulnerability and measured nitrate was statistically significant when compared to 233 groundwater samples collected at the same locations during two different campaigns (2018 and 2024) (pooled Pearson r = −0.27, p < 0.001; Spearman ρ = −0.19, p = 0.007; Kruskal–Wallis H = 14.10, p = 0.003). Levels of nitrate in both Low and Moderate vulnerability zones (6.0 and 7.7 mg/L, respectively) were higher than in Very High zones (3.4 mg/L). The inverse direction was consistent across both campaigns and robustly significant in the 2024 dataset (ρ = −0.33, p < 0.001), which covered a wider contamination gradient; in the 2018 dataset, only the parametric test was significant. Nitrate showed no significant difference between land-use classes (H = 7.23, p = 0.065) and was found as a few individual high concentrations, suggesting that these were not diffuse loading issues or intrinsic susceptibility, but were likely influenced by point sources. These results show that intrinsic DRASTIC vulnerability is useful to identify areas vulnerable to potential future contamination, but does not explain the current distribution of contamination in this aquifer, which is influenced by point-source loading and residence-time effects. To provide effective groundwater protection, intrinsic vulnerability assessment must be complemented with specific monitoring of point sources. Full article

Water quality analysis plays an essential role in maintaining the health and sustainability of river ecosystems, especially in semi-arid regions like the Arroyo Colorado Watershed in South Texas. Since the river is a vital source of water supply for local communities, agriculture, and wildlife, it faces significant challenges and pollution from land use changes, climate variation, and agricultural runoff. Continuous monitoring and assessment of water quality parameters and their temporal variability are essential to ensure the drinking water supply and aquatic ecosystem health. However, comprehensive laboratory-based water quality investigations are often constrained by higher costs, logistical complexity, and limited manpower. As a result, monitoring datasets are often not available for all water quality parameters, or the datasets may be incomplete. To address such challenges, the objective of this study was to evaluate the potential of water quality index (WQI)-based assessment supported by machine learning algorithms as an alternative decision-support tool for water quality evaluation. The analysis compared four monitoring stations in the Austin and Arroyo Colorado Watersheds, with particular emphasis on one gauging station at Port Harlingen. Datasets were collected from the Texas Commission of Environmental Quality (TCEQ). A complete exploratory data analysis (EDA) was performed to understand the TCEQ water quality datasets containing sixteen parameters, and seven water quality parameters were selected based on multicollinearity checks. It was observed that seven independent water quality parameters (dissolved oxygen, ammonia, nitrate, phosphorus, temperature, fecal coliform, and residual non-filterable material concentrations) were identified as sufficient to define the WQI of the Austin monitoring stations. Moreover, U.S. Environmental Protection Agency (EPA)-based guidelines were utilized to scale individual parameters to a range of 0–100 to remove their magnitude and correlation-based bias. These parameters were further analyzed using machine learning techniques, i.e., principal component analysis, K-means, and one-class support vector machine, to compute the relative importance based on their fluctuation within the temporal dataset. Finally, the mean WQI model was developed for Port Harlingen and achieved a strong agreement with the National Sanitation Foundation (NSF) WQI (R² = 0.91). These findings demonstrate the applicability of the proposed data-driven WQI framework for regional water quality assessment and comparative analysis across watersheds. Full article

This study evaluated oxidative damage, antioxidant-related, and nitric oxide (NO)-related chemical markers in commercial bee pollen using two extraction systems. For this purpose, a total of 30 bee pollen samples from different brands and/or manufacturers were examined; each sample was subjected to aqueous extraction and ethanol/water (80:20, v/v). The levels of reduced glutathione (GSH), malondialdehyde (MDA), and NO metabolites, comprising nitrite and nitrate and expressed as total NOx, were determined in pollen extracts using spectrophotometric methods. The data were analyzed using descriptive statistics, group comparisons, and Spearman correlation analysis. The findings showed that ethanol/water (80:20, v/v) extraction provided significantly higher measured GSH equivalents and total NOx levels than aqueous extraction. Mean GSH equivalents were 79.12 ± 25.54 µmol/g in the aqueous extracts and 189.77 ± 45.09 µmol/g in the ethanol/water extracts, and the difference was found to be statistically significant (p < 0.001). NO metabolite levels were determined as 5.97 ± 8.34 and 366.70 ± 85.10 µmol/g, respectively, and the difference between the extraction methods was found to be statistically significant (p < 0.001). In contrast, MDA levels did not show a significant difference between the two extraction systems (p = 0.391). A significant positive correlation was observed between GSH and NO metabolites in the combined dataset (r = 0.660, p < 0.001). The findings suggest that 80% ethanolic bee pollen extract may represent a promising source of NO metabolites for future investigation as a natural alternative to synthetic sodium nitrite in processed meat products. However, this hypothesis requires validation through microbiological, technological, sensory, and shelf-life studies. Full article

Electrodeposition of bismuth from an acidic nitrate solution on copper electrodes by use of the potentiostatic mode of electrodeposition has been investigated with the aim to define conditions for obtaining dendritic forms. Morphology and structure of Bi deposits produced at the different cathodic potentials were featured by techniques of scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS) and X-ray diffraction (XRD), and correlated with the polarization features. The Bi dendrites were formed starting from the plateau of the limiting diffusion current density, while granules were formed at the cathodic potential which preceded the plateau. The shape of dendrites changed from very compact, formed at the plateau, to highly branched, formed at cathodic potentials beyond the plateau of the limiting diffusion current density, where the current density continuously grew with the increase in the cathodic potential. Both granules and dendrites showed the forceful preferred orientation in the basal (003) crystal plane with the lowest surface energy. The performed morphological and structural analysis classified Bi into a group of so-called normal metals, characterized by high values of both the exchange current density and overpotential for hydrogen evolution reaction and by low melting points. Full article