Search Results (3,551)

This study presents a generalized, high-precision measurement system based on Integrated Absorption Spectroscopy (IAS) for determining gas-phase absorption cross sections of low-volatility organic compounds (LVOCs), particularly semi-volatile organic compounds (SVOCs) in the atmosphere. Accurate cross sections and their temperature dependence are essential for modeling atmospheric and high-temperature processes. We coupled a temperature-controlled inlet and cell (473 K) with a nitrogen carrier gas to measure the cross sections of 2-nitrophenol (2-NP) and naphthalene from 250 to 400 nm. At 473 K, peak cross sections for 2-NP were 2.31 × 10⁻¹⁷ cm²/molecule at 260 nm and 1.16 × 10⁻¹⁷ cm²/molecule at 335 nm. For naphthalene, values between 258 and 280 nm decreased from 1.62 × 10⁻¹⁷ to 1.28 × 10⁻¹⁷ cm²/molecule. Thermally induced spectral broadening and reduced peak cross sections align with thermodynamic theory. These high-temperature data resolve discrepancies among low-temperature datasets. For example, our maximum cross section for 2-NP (300–400 nm) is 29% lower than that reported by Chen et al. (293 K), whereas the value from Sangwan and Zhu (295 K) is 86.8% lower than Chen’s, supporting the higher reliability of Chen’s data. The IAS method thus offers a robust approach for quantifying absorption cross sections under atmospherically relevant conditions. Full article

The growing demand for sustainable and efficient synthetic methodologies has brought nanocatalysis to the forefront of modern organic chemistry, particularly in the construction of heterocyclic compounds through multicomponent reactions (MCRs). Among various nanocatalysts, calcium oxide nanoparticles (CaO NPs) have gained significant attention because of their strong basicity, thermal stability, low toxicity, and cost-effectiveness. This review provides a comprehensive account of the recent strategies using CaO NPs as heterogeneous catalysts for the green synthesis of nitrogen- and oxygen-containing heterocycles through MCRs. Key reactions such as Biginelli, Hantzsch, and pyran annulations are discussed in detail, with emphasis on atom economy, reaction conditions, product yields, and catalyst reusability. In many instances, CaO NPs have enabled solvent-free or aqueous protocols with high efficiency and reduced reaction times, often under mild conditions. Mechanistic aspects are analyzed to highlight the catalytic role of surface basic sites in facilitating condensation and cyclization steps. The performance of CaO NPs is also compared with other oxide nanocatalysts, showcasing their benefits from green metrics evaluation like E-factor and turnover frequency. Despite significant progress, challenges remain in areas such as asymmetric catalysis, industrial scalability, and catalytic stability under continuous use. To address these gaps, future directions involving doped CaO nanomaterials, hybrid composites, and mechanochemical approaches are proposed. This review aims to provide a focused and critical perspective on CaO NP-catalyzed MCRs, offering insights that may guide further innovations in sustainable heterocyclic synthesis. Full article

This study evaluated the technical and economic feasibility of the biofloc technology (BFT) system during the fry rearing phase of Nile tilapia (Oreochromis niloticus), focusing on suspended solids management, stocking density, and economic performance at a pilot scale. Three trials were conducted. The first assessed the effects of four total suspended solids (TSS) ranges (0–200, 200–400, 400–600, and 600–800 mg·L⁻¹) on larval performance and water quality. TSS levels between 200 and 600 mg·L⁻¹ promoted improved water quality and zootechnical performance. The second trial tested five stocking densities (2, 4, 6, 8, and 10 larvae·L⁻¹), evaluating their impact on water quality, survival, and size uniformity. Higher densities negatively affected survival (R² = 0.84) and final weight (R² = 0.92), while also increasing solids and nitrogenous compounds, thus impairing performance (p < 0.05). The third trial monitored six production cycles at pilot scale, evaluating zootechnical parameters, sex reversal efficiency, and economic indicators. All cycles showed survival rates above 85%, sex reversal close to 100%, and positive net margins (18.5 to 41.9%), demonstrating the viability of BFT for commercial fry operations. The results emphasize the importance of controlling suspended solids and stocking density to maintain water quality and optimize larval performance. Furthermore, the system proved economically viable, with good feed conversion rates and profitability, even without water exchange. These findings support BFT as a sustainable and efficient alternative for tilapia fry production, offering significant water savings and promising economic returns when properly managed. Full article

Phenolic compounds constitute the predominant group of recalcitrant organic contaminants in coal chemical wastewater. In this study, humic acid and urea were used as carbon and nitrogen sources to prepare nitrogen-doped carbon material (labeled as NC-800) through a two-step calcination process. Using this catalyst (NC-800) to activate PMS for phenol degradation achieved 100% phenol removal across a wide pH range (1–9). The removal rate remained at 99.62% even with high concentrations of inorganic anions or natural organic matter, breaking through the limitations of traditional Fenton-like reactions in terms of acid–base environment and anion influence. The quenching experiment and electron spin resonance (ESR) spectroscopy results indicated that the N-C/PMS system generated three active species hydroxyl radicals (•OH), superoxide radicals (O₂^•−), and singlet oxygen (¹O₂) through the active sites in electron-rich regions such as graphite nitrogen, pyrrole nitrogen, and C=O. An electrochemical test revealed that the system formed a metastable NC-800-PMS* complex during the reaction, indicating the existence of a non-radical pathway of electron transfer. The combination of free radicals (•OH, O₂^•−) and non-free radicals (¹O₂, electron transfer) facilitated the rapid degradation of phenol, providing a theoretical basis for phenol degradation. Full article

In 2023, studies were carried out on the aquatic environment of the forest lake Łętowskie. The studies covered the horizontal and vertical planes and seasonal dynamics. Lake Łętowskie is a lake with an area of 402 ha, which distinguishes it from other lakes in Pomerania due to its large area. In three quarters of the lake shore border forests, changes in surface and volume have been observed in the lakes over the last century, which has affected the chemistry of the water. The aims of this study were to determine the dependencies between the concentration of biogenic substances in the near-bottom layer and subsurface water and analyze the dependencies between chemical parameters in the water of the mid-forest lake Łętowskie. In the water samples obtained, including the surface layer (SW) and the near-bottom layer (NBL), the concentrations of N-NO₃, N-NO₂, N-NH₄, N-tot, N-org, P-PO₄, P-tot, P-org, and O₂, electrolytic conductivity, pH, Ca, and Mg were determined. Statistical analyses were carried out, including tests and multidimensional PCA and cluster analysis. A significant effect of forests on the chemical composition of lake water was observed. The conducted studies of Łętowskie Lake indicate that the NBL experiences seasonal dynamics, where phosphorus and nitrogen compounds are transformed, which causes trophic changes in the lake. Based on multidimensional cluster analysis, differences between the SW and the NBL were shown. In Łętowskie Lake, the level of biogenic substances in the water is significantly influenced by processes occurring inside the lake as a result of the exchange of matter between the NBL and bottom sediments. This exchange in shallower areas of the lake is influenced by winds, especially in exposed locations: this was observed for P-tot, P-PO₄, P-org, Ca, N-NO₃ and N-NH₄, N-tot, and N-org. The conducted studies are important for supporting the protection of the Landscape Area “Łętowskie Lake and the vicinity of Kępice” to preserve the existing values of the natural environment and maintain the ecological balance of natural systems. Current scientific publications on the hydrochemical data of Łętowskie Lake are currently lacking, and the available data needs to be updated. Full article

Gas nitriding was implemented in the current work at a constant nitrogen potential (K_N) of 2.0 for 8 h to enhance the fatigue properties of SCM 440 steel, and the results were compared with those of the substrate tempered at the nitriding temperature (475 °C). Fine particle peening (FPP) prior to nitriding imposed a refined structure and induced compressive residual stress (CRS) in the near-surface peened zone. The fine-grained structure provided numerous paths to enhance nitrogen diffusion inwards during nitriding. The compound layer formed on the nitrided SCM 440 steel primarily comprised a mixture of Fe₃N and Fe₄N; however, the pre-peened and nitrided (SPN) specimens exhibited a higher proportion of Fe₃N and a thicker compound layer than the non-peened and nitrided (NPN) counterparts. In addition, FPP prior to nitriding increased both the case depth and the magnitude of the CRS field compared with nitriding alone. The fatigue limits of the substrate (SB), NPN, and SPN samples were approximately 750, 1050, and 1400 MPa, respectively. Gas-nitriding at 475 °C significantly improved the fatigue performance of SCM 440 steel. Moreover, pre-peening prior to nitriding further enhanced fatigue strength and life of the treated SCM 440 steel by introducing a deeper case depth and higher CRS field. Multiple cracks initiation at the outer surface of the SB sample accounted for its lowest fatigue limit among the tested samples. Surface microcracks and pits on the surface of the NPN specimen would be crack initiation sites and harmful to its fatigue resistance. These surface dents were considered to be responsible for fatigue crack initiation in the SPN specimens. Therefore, polishing after nitriding to reduce surface roughness and/or microcracks was expected to further increase the fatigue resistance and the reliability of nitrided SCM 440 steel. Full article

Aromatic ring systems appear ubiquitously in active pharmaceutical substances, such as FDA-approved histone deacetylase inhibitors. However, these rings reduce the water solubility of the molecules, which is a disadvantage during application. To address this problem, azaborine rings may be substituted for conventional aromatic ring systems. These are obtained by replacing two adjacent carbon atoms with boron and nitrogen. Incorporating B–N analogs in place of aromatic rings not only enhances structural diversity but also provides a strategy to navigate around patent-protected scaffolds. We synthesized azaborines, which are isosteric to naphthalene and indole, and utilized them as capping units for HDAC inhibitors. These molecules were attached to various aliphatic and aromatic linkers with different zinc-binding units, used in established active compounds. Nearly half of the twenty-four molecules tested exhibited inhibitory activity against at least one of the enzymes HDAC1, HDAC4, or HDAC8, with three compounds displaying IC₅₀ values in the nanomolar range. We have therefore demonstrated that azaborine building blocks can be successfully incorporated into HDACis, resulting in a highly active profile. Consequently, it should be feasible to develop active substances containing azaborine rings against other targets. Full article

The reaction of 4′–bromo-fenamic acid, a bromo-derivative of fenamic acid (the scaffold of the fenamate non-steroidal anti-inflammatory drugs), with Co(II) in the absence or presence of various nitrogen-donor ligands yielded nine novel, neutral mononuclear Co(II) complexes. These complexes were characterized by physicochemical and spectroscopic techniques and single-crystal X-ray crystallography. The biological evaluation of the compounds focused on their antioxidant and antimicrobial efficacy, as well as their interaction with calf-thymus DNA, pBR322 plasmid DNA (in the absence or presence of diverse irradiations) and serum albumins. The complexes have shown significant antioxidant activity since they can scavenge 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radicals (up to 96.48 ± 0.07%) and reduce H₂O₂ (up to 96.93 ± 0.53%). Antimicrobial testing revealed that the complexes were more active than free 4′-bromo-fenamic acid with four of them classified as bactericidal agents against selected bacterial strains. The compounds can interact with calf-thymus DNA via intercalation, and the calculated DNA-binding constants are on the 10⁶ M⁻¹ order. The plasmid DNA-cleavage ability of the compounds is strongly enhanced under UVA irradiation (photocleavage > 90%). In addition, the compounds can bind tightly and reversibly to serum albumins with binding constants in the 10⁵ M⁻¹ range. Full article

Multi-centennial C budgets in forested watersheds require information on forest growth, detritus turnover, and disturbances, as well as the transfer to and fate of terrestrial C in aquatics systems. Here, a sediment gravity core was collected from a drinking water reservoir in Canada, and analyzed for temporal changes in charcoal, magnetic susceptibility, carbon, and nitrogen. These indicators were used to assess disturbance history and terrestrial C sequestration in sediments. During the reservoir development period from 1910 to 2012, charcoal flux and magnetic susceptibility increased ca. 10 years after nearby fire and forest-clearing events associated with reservoir expansion. Total C and δ¹³C gradually declined during the development period, likely due to increased inputs of mineral soil from human activity. Concurrently, total terrestrial C sequestered in sediments, estimated using three or eight marker compounds, ranged between 3557 and 5145 Mg C/100 yrs, accounting for 11%–17% of DOC exports to the reservoir (30,640 Mg C/100 yrs), as estimated from a previously developed terrestrial carbon budget model. In comparison, mixed-severity fires burned around the reservoir during the pre-development period (pre-1910), as evidenced by stand ages and/or increases in charcoal flux. In general, decreased terrestrial C flux was associated with higher-severity fires that burned between 1870 and 1890 and perhaps around 1790. Further, comparisons show that soil erosion was up to 3× greater in the development versus the pre-development period. Overall, this investigation revealed the impact of land use change and fire on watershed carbon budgets and advanced a previously developed pyGC-MS methodology that demonstrated the amount of terrestrial and aquatic C being buried in sediment. It also identified the fraction of terrestrial C that was exported from the forest to the reservoir and sequestered in the sediment, uncommon data that could inform current and future landscape C budget modelling studies in this region. Full article

This study aimed to evaluate the effects of sequential supplementation with different crude protein levels and periods on performance, nutritional and metabolic characteristics, and efficiency of nitrogenous compounds use in grazing male Nellore calves at pre-weaning. Fifty male Nellore calves during pre-weaning were distributed in a completely randomized design in a 2 × 2 factorial arrangement. The strategies were as follows: Supplementation period in the initial pre-weaning was 1–78th experimental day and in the final pre-weaning was 79–156th experimental day. The Low and high protein levels in the supplement were 150 g CP/kg) and 300 g CP/kg, respectively. All animals received 6 g/kg BW of supplement. Protein levels in the supplement did not affect intake of forage DM, and neutral detergent fiber in the animals. However, a higher CP intake and the CP to DOM ratio (p-value < 0.05) was evidence for the high calves compared with low calves. Supplementation strategies did not affect the blood concentrations of IGF-1, glucose, and total protein. Likewise, protein levels in the supplement did not affect the ADG and number and diameter of muscle fibers. In conclusion, the decrease in protein levels in the supplement from 300 to 150 g CP/kg DM does not detrimentally affect performance and nutritional and metabolic characteristics in male beef calves under a grazing system at pre-weaning. Full article

A new copper(II) complex was synthesized using chromone-2-carboxylic acid as the main ligand, and coordinated pyridine molecules. The complex was successfully crystallized and structurally characterized by single crystal X-ray diffraction. This revealed a mononuclear structure with a distorted square pyramidal geometry around the central Cu(II) ion. The coordination sphere comprises oxygen atoms from the chromone moiety and nitrogen atoms from pyridine, resulting in a five-coordinate complex. A comprehensive physicochemical characterization was performed using Fourier transform infrared spectroscopy (FT-IR), UV–Vis spectroscopy, elemental (C, H, N), electrochemical (CV) and thermal analysis (TGA/DSC) to confirm the coordination environment and thermal stability of the compound. The complex exhibits distinct spectroscopic features indicative of ligand–metal charge transfer and d–d transitions typical of Cu(II) species. In addition, the synthesized complex was subjected to antimicrobial screening against Gram-positive and Gram-negative bacteria. The compound showed promising antibacterial activity, particularly against Escherichia coli, indicating its potential as a bioactive coordination compound. These results contribute to the growing body of research on metal-based chromone derivatives and emphasize the importance of copper complexes for the development of new antibacterial agents with defined crystal structures. Full article

Schisandra chinensis (Turcz.) Baill. (S. chinensis) is a widely used medicinal plant whose therapeutic efficacy is closely linked to its lignan content. While previous studies have focused on soil fertility and cultivar variation, the interplay among soil nutrients, rhizosphere microbiota, and lignan accumulation remains poorly understood. This study investigated S. chinensis grown across 20 cultivation sites to elucidate the relationships among soil nutrient profiles, fruit lignan composition, and rhizosphere microbial communities. Six major lignans were quantified using HPLC, soil nutrients were analyzed via standard chemical assays, and rhizosphere bacterial communities were profiled using 16S rRNA sequencing. Multivariate analyses revealed significant variation in soil properties and lignan content across sites. Notably, available phosphorus, organic matter, and total nitrogen showed strong correlations with specific lignan compounds. From the top 50 taxa ranked by relative abundance at the genus level, 18 bacterial genera associated with lignan components were identified. Among them, Mycobacterium, Arthrobacter, Haliangium, Bacillus, Sphingomonas, Rhodanobacter, Ellin6067, Bradyrhizobium, Pseudolabrys, Chujaibacter, Gemmatimonas, Bryobacter, MND1, Candidatus Sollbacter, Gaiella, Paenibacillus, RB41, and Candidatus_Udaeobacter were significantly associated with lignan levels, suggesting potential microbial involvement in lignan biosynthesis. These findings provide insights into the ecological factors shaping the medicinal quality of S. chinensis and offer a foundation for targeted cultivation and breeding strategies. Full article

The growing potassium (K) demand and supply–demand imbalance in intensive agriculture require the development of multi-nutrient K fertilizers. Polyhalite (POLY), a multi-nutrient natural mineral rich in K, calcium, magnesium, and sulfur, can enhance soil nutrient diversity and fertility. However, research on its synergistic application with nitrogen (N) fertilizer remains limited. Therefore, this study was designed to apply three different fertilizer composites at four N concentration gradients through field plot experiments to evaluate crop productivity and nutrient use efficiency. Results revealed that the application of both compound fertilizers with N fertilizer increased maize yield, ranging from 1.03% to 11.53%, compared with the PK control. Moreover, 25-7-8 (MOP)(POLY26%) achieved a maximum yield of 9499.88 kg/ha at the N1 (170 kg/ha) level. This represents a significant increase of 11.53% compared with the PK control. Moreover, the application of compound fertilizer containing POLY could significantly increase the N fertilizer utilization rate; improve the quality of maize; and exert a significant effect on soil pH, EC, and nutrient content. This study paves the way for broader application of POLY by establishing its novel role as a sustainable nutrient source. It provides critical strategic guidance for advancing global resource-efficient agriculture. Full article

In this study, the use of spent coffee waste as a green precursor of polyphenolic compounds, which are subsequently employed as reducing agents for the synthesis of zero-valent iron nanoparticles (nZVI) aimed at the efficient removal of dyes from aqueous systems, has been investigated. The nanoparticles, generated in situ in the presence of controlled amounts of hydrogen peroxide, were applied in the removal of organic dyes—including methylene blue, methyl orange, and orange G—through a heterogeneous Fenton-like catalytic process. The synthesized nZVI were thoroughly characterized by nitrogen adsorption at 77 K, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and powder X-ray diffraction (XRD). A statistical design of experiments and response surface methodology were employed to evaluate the effect of polyphenol, Fe(III), and H₂O₂ concentrations on dye removal efficiency. Results showed that under optimized conditions, a 100% removal efficiency could be achieved. This work highlights the potential of nZVI synthesized from agro-industrial waste through sustainable routes as an effective solution for water remediation, contributing to circular economy strategies and environmental protection. Full article

The seafood industry is increasingly adopting intelligent packaging to preserve product quality and improve freshness transparency. This study developed and evaluated a pH-sensitive freshness indicator (FI) for skate sashimi (Zearaja chilensis). This product is consumed at varying stages of fermentation. The FI incorporated bromothymol blue (BTB) and bromocresol purple (BCP) in a polymer matrix. It targeted volatile basic nitrogen (VBN) compounds, with trimethylamine (TMA) as the primary marker. As freshness declined, VBN compounds accumulated in the package headspace and caused a gradual FI color change from yellow to blue through pH variation. ΔE increased from 7.72 on day 2 to 23.52 on day 3. This marked the onset of visible color change and the FI reached full blue by day 7. Headspace solid-phase microextraction (HS-SPME) and gas chromatography–flame ionization detection (GC-FID) quantified monomethylamine (MMA), dimethylamine (DMA) and TMA throughout storage. ΔE correlated strongly with total bacterial count (TBC, r = 0.978), pH (r = 0.901) and TMA (r = 0.888). These results indicate that microbial growth, alkalinity increase and amine production were closely associated with color transitions. The FI reliably tracked freshness loss in skate sashimi. It has potential to enhance consumer transparency and strengthen quality control in the seafood supply chain. Full article