Radical Concentration Research Articles

One-step functionalization and polymer grafting potential of green silica derived from rice husk ash

Green silica has been synthesized from rice husk ash which exempts the landfilling of agricultural waste and the requirement of higher temperature for digestion, unlike the conventional mode of silica synthesis making the process of precipitation and functionalization sustainable. An energy-efficient method of functionalization has been optimized for the synthesis of functionalized silica from rice husk ash via co-condensation. The potential for providing better reinforcement leads silica to be used as filler in composite manufacturing. To obtain a better silica-polymer interaction, nitroxide functionalized silica has been synthesized over three different types of silica samples using different processes. The nitroxide functionalities were introduced by thiol-ene reaction between 4-acryloyloxy(2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and mercaptopropyl functionalized silica particles. The mercaptopropyl functionalized silica was synthesized by post-modification as well as co-condensation over commercial precipitated silica, commercial rice husk ash silica, and silica synthesized in the lab from sodium silicate obtained from rice husk ash. By comparing mercaptopropyl and nitroxide grafting density, it has been observed that the nitroxide loading highly depends on the method of functionalization and the co-condensed samples show higher nitroxide loading compared to the post-modified samples. The nitroxide functionalized samples were further subjected to polystyrene grafting, and the efficiency of surface nitroxide radicals in capturing the polymer radicals with respect to nitroxide loading was determined. The grafting density was observed to increase with the increase in conversion and the increase in the initiator-to-monomer ratio. However, the grafting density was observed to be saturated at some point despite having a higher surface area and surface nitroxide radicals. The study can be used to tune the surface nitroxide radical concentration and surface area for optimum polymer grafting for engineering applications.

On the Chemical Effect of Steam Addition to Premixed Hydrogen Flames with Respect to NOx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {NO}_\ ext {x}$$\\end{document} Emissions and Flame Speed

The present work analyses the effect of water vapour addition on NOx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {NO}_\ ext {x}}$$\\end{document} emissions of premixed hydrogen flames. In doing so, the adiabatic flame temperature is maintained by increasing the equivalence ratio, or alternatively increasing the unburned gas temperature, for increasing levels of water loading. Thus, it is possible to elucidate the changes in NOx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {NO}_\ ext {x}}$$\\end{document} production at constant-temperature conditions when the mixture is diluted with water. A consistent reduction of NOx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {NO}_\ ext {x}}$$\\end{document} emissions for increasing water dilution can be observed from 1-D premixed freely propagating flame simulations. Regarding the chemical kinetics effect of water vapour, the relative importance of different third-body reactions is examined by modifying the corresponding water collision efficiencies individually. For the chemical mechanism adopted, three reactions directly affect the nitrogen chemistry and the remaining relevant reactions are important for the flame structure and radicals concentration. The analysis stresses the importance of indirect effects like the formation and consumption of O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {O}$$\\end{document} and H\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {H}$$\\end{document} radicals in the pre-heat zone, which enhance the subsequent formation of NOx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {NO}_\ ext {x}}$$\\end{document} within the flame. The presence of steam can lead to a reduction of approximately 50%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$50\\%$$\\end{document} in NOx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext {NO}_\ ext {x}}$$\\end{document} emissions under conditions close to stoichiometry and high water loading (10%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10\\%$$\\end{document} by mass), compared to scenarios without water addition. Furthermore, the efficiency of water in third-body reactions significantly contributes to an emission reduction, and half of NO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {NO}$$\\end{document} emissions under the same water loading conditions at high equivalence ratio are observed when the third-body reaction efficiency is activated with respect to the case with zero efficiency. This reduction is primarily attributed to effects on radical concentrations. Finally, the chemical effect via the third-body efficiency of water is examined with respect to flame speed. It turns out that the adiabatic flame temperature plays a key role for the relative influence of the chemical kinetics effect of water dilution. A cross-over temperature is found, below which the chemical effect of water reduces the flame speed, whereas the flame speed is increased above it.

Study on the inhibition mechanism of ammonium dihydrogen phosphate on the pyrolysis gas flame of red pine wood

Ammonium phosphate-based fire extinguishers are widely used in forest fires due to their low cost and effectiveness against solid combustibles. However, the mechanism by which ammonium phosphate interacts with pyrolysis gas flames is not well understood, and there is a lack of precise experimental validation and correction of the chemical kinetics models regarding the suppression mechanism. Therefore, this study utilized NH4H2PO4 powder as a fire extinguishing agent and constructed a PLIF experimental system suitable for NH4H2PO4/red pine pyrolysis gas/air interactions. Through experiments, the changes in the concentration of OH radicals with different amounts of extinguishing agent at various equivalence ratios were measured. By employing Chemkin software, the study comprehensively analyzed the kinetic regulation mechanism of NH4H2PO4 on red pine pyrolysis gas flames from aspects such as chemical inhibition, sensitivity of elementary reactions, chemical reaction pathways, and chemical thermodynamics. The study revealed the characteristics and mechanisms of NH4H2PO4 powder inhibition, identifying R1092, R1098, R1116, and R1120 as the primary elementary reactions suppressing flame combustion. The mutual inhibition cycles formed among these reactions were found to be the main reasons for the suppression of H and OH radicals in the flame. Moreover, PO2 was identified as the primary phosphorus-containing fire extinguishing agent responsible for extinguishing the flame.

Comprehensive studies on the biological activities of human metastatic (MDA-MB-231) and non-metastatic (MCF-7) breast cancer cell lines, directly or combinedly treated using non-thermal plasma-based approaches

Progressive incidence and a pessimistic survival rate of breast cancer in women worldwide remains one of the most concerning topics. Progressing research indicates a potentially high effectiveness of use cold atmospheric plasma (CAP) systems. The undoubted advantage seems its simplicity in combination with other anti-cancer modalities. Following observed trend of studies, one inventory CAP system was applied to directly treat human breast cancer cell lines and culturing in two different Plasma Activated Media (PAM) for combined utilization. Proposed CAP treatments on MCF-10 A, MCF-7, and MDA-MB-231 cell lines were studied in terms of impact on cell viability by MTT assay. Disturbances in cell motility following direct and combined CAP application were assessed by scratch test. Finally, the induction of apoptosis and necrosis was verified with annexin V and propidium iodide staining. Reactive species generated during CAP treatment were determined based on optical emission spectrometry analysis along with colorimetric methods to qualitatively assess the NO2−, NO3−, H2O2, and total ROS with free radicals concentration. The most effective approach for CAP utilization was combined treatment, leading to significant disruption in cell viability, motility and mostly apoptosis induction in breast cancer cell lines. Determined CAP dose allows for mild outcome, showing insignificant harm for the non-cancerous MCF-10 A cell line, while the highly aggressive MDA-MB-231 cell line shows the highest sensitivity on proposed CAP treatment. Direct CAP treatment seems to drive the cells into the sensitive state in which the effectiveness of PAM is boosted. Observed anti-cancer response of CAP treatment was mostly triggered by RNS (mostly NO2− ions) and ROS along with free radicals (such as H2O2, OH•, O2-•, 1O2, HO2•). The combined application of one CAP source represent a promising alternative in the development of new and effective modalities for breast cancer treatment.

Dipolar Order Induced Electron Spin Hyperpolarization.

The structure of coupled electron spin systems is of fundamental interest to many applications, including dynamic nuclear polarization (DNP), enhanced nuclear magnetic resonance (NMR), the generation of electron spin qubits for quantum information science (QIS), and quantitative studies of paramagnetic systems by electron paramagnetic resonance (EPR). However, the characterization of electron spin coupling networks is nontrivial, especially at high magnetic fields. This study focuses on a system containing high concentrations of trityl radicals that give rise to a DNP enhancement profile of 1H NMR characteristic of the presence of electron spin clusters. When this system is subject to selective microwave saturation through pump-probe ELectron DOuble Resonance (ELDOR) experiments, electron spin hyperpolarization is observed. We show that the generation of an out-of-equilibrium longitudinal dipolar order is responsible for the transient hyperpolarization of electron spins. Notably, the coupled electron spin system needs to form an AX-like system (where the difference in the Zeeman interactions of two spins is larger than their coupling interaction) such that selective microwave irradiation can generate signatures of electron spin hyperpolarization. We show that the extent of dipolar order, as manifested in the extent of electron spin hyperpolarization generated, can be altered by tuning the pump or probe pulse length, or the interpulse delay in ELDOR experiments that change the efficiency to generate or readout longitudinal dipolar order. Pump-probe ELDOR with selective saturation is an effective means for characterizing coupled electron spins forming AX-type spin systems that are foundational for DNP and quantum sensing.

Streptomycin generates oxidative stress in melanin-producing cells: In vitro study with EPR spectroscopy evidence

Streptomycin (STR) is an aminoglycoside antibiotic with a broad-spectrum of activity and ototoxic potential. The mechanism of STR-induced inner ear damage has not been fully elucidated. It was previously found that STR binds to melanin, which may result in the accumulation of the drug in melanin-containing tissues. Melanin pigment is present in various parts of the inner ear, including the cochlea and vestibular organ.The present study aimed to assess if streptomycin generates oxidative stress and affects melanogenesis in normal human melanocytes. Moreover the variation of free radical concentration in STR-treated melanocytes was examined by electron paramagnetic resonance spectroscopy (EPR). We found that STR decreases cell metabolic activity and reduces melanin content. The observed changes in the activity of antioxidant enzymes activity in HEMn-DPs treated with streptomycin may suggest that the drug affects redox homeostasis in melanocytes. In this work EPR study expanded knowledge about free radicals in interactions of STR and melanin in melanocytes. The results may help elucidate the mechanisms of STR toxicity on pigment cells, including melanin-producing cells in the inner ear. This is important because understanding the mechanism of STR-induced ototoxicity would be helpful in developing new therapeutic strategies to protect patients' hearing.

Correction of Nitrosative Stress During Reparative Regeneration of the Nasal Cavity Mucosa in an Experimental

Introduction. Nitric oxide metabolites play an important role in prolongation of the inflammatory reaction, disorders of epithelial regeneration in diseases of the upper respiratory tract. One of the promising approaches to regulating the bioactivity of nitric oxide is the use of antioxidants.The objective of the study is to evaluate the effectiveness of antioxidant therapy for the correction of nitrosative stress during reparative regeneration of the nasal mucosa in an experiment.Methods. A preclinical randomized experimental study is conducted on 160 rats, divided into 4 groups. The control group (n = 40) consists of intact animals. Animals in experimental group 1 (n = 40) do not receive treatment aſter injury; in group 2 (n = 40) anti-inflammatory treatment is prescribed. The third group consists of laboratory rats (n = 40), which are additionally injected into the nasal cavity with an antioxidant — a 15 % solution of 1,1-dimethyl-3-oxobutylphosphonic acid dimethyl ester. On days 2, 5, 10, and 14 of observation, the concentration of nitrates and nitrites and C-reactive protein in the blood of animals are determined.Results. In group 3, aſter an increase in the level of nitric oxide metabolites on day 2 aſter injury on day 5, a significant (p < 0.05) decrease was noted in comparison with other groups, and by day 10— normalization of the indicator. An increase in the level of C-reactive protein in blood serum correlated with the concentration of nitric oxide metabolites.Discussion. The optimal therapeutic effect when taking antioxidants develops when administered in the first hours aſter injury to reduce the excessive formation of reactive nitrogen radicals. However, the duration of administration should not exceed 4–5 days to avoid a significant decrease in the level of nitric oxide metabolites and deterioration of mucosal regeneration.Conclusions. Assessment of nitric oxide metabolitesin the blood at different times aſter injury is an important marker of inflammatory activity. The use of antioxidants helps to reduce the concentration of active nitrogen radicals.

Physicochemical Properties and Antioxidant Activity of CRISPR/Cas9-Edited Tomato SGR1 Knockout (KO) Line.

Tomatoes contain many secondary metabolites such as β-carotene, lycopene, phenols, flavonoids, and vitamin C, which are responsible for antioxidant activity. SlSGR1 encodes a STAY-GREEN protein that plays a critical role in the regulation of chlorophyll degradation in tomato leaves and fruits. Therefore, the present study was conducted to evaluate the sgr1 null lines based on their physicochemical characteristics, the content of secondary metabolites, and the γ-Aminobutyric acid (GABA) content. The total soluble solids (TSS), titrated acidity (TA), and brix acid ratio (BAR) of the sgr1 null lines were higher than those of the wild type(WT). Additionally, the sgr1 null lines accumulated higher levels of flavor-inducing ascorbic acid and total carotenoids compared to WT. Also, the total phenolic content, total flavonoids, GABA content, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical content of the sgr1 null lines were higher than those of the WT. Therefore, these studies suggest that the knockout of the SGR1 gene by the CRISPR/Cas9 system can improve various functional compounds in tomato fruit, thereby satisfying the antioxidant properties required by consumers.

Higher efficiency of vanadate iron in heterogeneous Fenton-like systems to pretreat sugarcane bagasse and its enzymatic saccharification.

Pretreatment is crucial for effective enzymatic saccharification of lignocellulose such as sugarcane bagasse (SCB). In the present study, SCB was pretreated with five kinds of heterogeneous Fenton-like systems (HFSs), respectively, in which α-FeOOH, α-Fe2O3, Fe3O4, and FeS2 worked as four traditional heterogeneous Fenton-like catalysts (HFCs), while FeVO4 worked as a novel HFC. The enzymatic reducing sugar conversion rate was then compared among SCB after different heterogeneous Fenton-like pretreatments (HFPs), and the optimal HFS and pretreatment conditions were determined. The mechanism underlying the difference in saccharification efficiency was elucidated by analyzing the composition and morphology of SCB. Moreover, the ion dissolution characteristics, variation of pH and Eh values, H2O2 and hydroxyl radical (·OH) concentration of FeVO4 and α-Fe2O3 HFSs were compared. The results revealed that the sugar conversion rate of SCB pretreated with FeVO4 HFS reached up to 58.25%, which was obviously higher than that under other HFPs. In addition, the surface morphology and composition of the pretreated SCB with FeVO4 HFS were more conducive to enzymatic saccharification. Compared with α-Fe2O3, FeVO4 could utilize H2O2 more efficiently, since the dissolved Fe3+ and V5+ can both react with H2O2 to produce more ·OH, resulting in a higher hemicellulose and lignin removal rate and a higher enzymatic sugar conversion rate. It can be concluded that FeVO4 HFP is a promising approach for lignocellulose pretreatment.

Studies of the diluent, temperature and pressure effect on the lower and upper flammability limits of ammonia in air

Ammonia safety and environmental protection research forms the basis for its role as a clean energy carrier. In this work, an experimental study was conducted in this work to analyze the effect of different inhibitors (nitrogen, argon and water vapor) on the flammability limits (FLs) of ammonia at elevated temperatures and pressures. In addition, the influence of diluents on the compositions and flame temperature changes was evaluated, and the temperature sensitivity coefficients of the elementary reactions and the ROP of free radicals and partial products at the FL concentrations were analyzed. The findings indicated that water vapor provided the strongest flame retardant effect on ammonia in three inhibitors. Within a certain temperature and pressure range, the FLs of ammonia in ammonia/diluent/air can be predicted using the extended Le Chatelier equation. The flame temperature decreased at the lower flammability limit (LFL) concentrations and increased at the upper flammability limit (UFL) concentrations of ammonia with increasing initial pressure. As the initial temperature increases, the flame temperature decreases during ammonia combustion. The influence of ammonia concentration on flame temperature is greater than that of diluents dilution. The elementary reactions H+O2<=>O+OH (R1) and NH2+NO<=>NNH+OH (R82) were the primary reactions that increased the flame temperature at the FL ammonia concentrations in ammonia/diluent/air. Conversely, NH2+NO<=>N2+H2O (R80) and H+O2(+M)<=>HO2(+M)(R15) were the main reactions that decreased the flame temperature. H, OH and NH2 radicals played a crucial role in the combustion reaction process at ammonia FL concentrations. At the LFL concentrations of ammonia, the molar fraction of the OH radical showed the greatest variation, while at the UFL concentrations of ammonia it was NH2 radical. The elementary reaction NH3+OH<=>NH2+H2O (R158) was the primary reaction that consumed OH radical and promoted the formation of NH2 radical. Free radical concentrations decreased with increasing pressure and temperature, while the change rate of free radical ROP accelerated with increasing pressure. In addition to nitrogen and water, the partial products were mainly nitric oxide at the LFL concentrations, while at the UFL concentrations were mainly hydrogen.

Experimental confirmation of the formation of collective modes of the magnetization motion of paramagnetic particles in dilute solutions due to spin exchange

Experimental confirmation of the manifestations of new spin exchange paradigm in EPR spectra of 14N nitroxide radical solutions is presented. It was shown that in the region of relatively low concentrations of radicals, the two side components of the spectrum have a mixed shape (the sum of the absorptive line and dispersive line). The dispersion contributions in these two lines have opposite signs. As the concentration of radicals increases, the contribution of dispersion passes through an extremum and in the region of maximum contribution of dispersion, the contribution of absorption to these two lines changes sign. In the region of high concentrations of radicals, when one homogeneously broadened line is practically observed, it turns out that these side components have resonant frequencies that do not coincide with the frequency of the center of gravity of the spectrum.

Study on ignition mechanism of turbulent jet pre-chamber of H2/CO mixture

Jet flow pre-chamber ignition is used to increase the thermal efficiency of lean-burn engines, but the ignition mechanism in the main chamber remains unclear. Therefore, the ignition mechanism of the jet pre-chamber was investigated experimentally and numerically. The results show that the flame in the pre-chamber can indeed propagate to the main chamber through a 2-mm-diameter nozzle without extinguishing. This occurs because at the very start the flame is located in the center of the nozzle and maintains a certain distance from the wall, preserving both temperature and free radicals. Next the flame in the nozzle will be extinguished due to fuel depletion, leading to a significant reduction in the concentration of free radicals. The free radicals pass through the nozzle, and compared with only the hot ignition, the ignition in the main chamber is one preparation period earlier, indicating a more concentrated heat release and higher thermal conversion ability in real engines.

UPBEAT1-ROS-POD-PAL System under Different Xylogenesis Scenarios in Karelian Birch (Betula pendula Roth var. carelica (Mercl.) Hämet-Ahti).

We studied UPBEAT1 (UPB1) which regulated superoxide radical / hydrogen peroxide ratio together with peroxidase (POD) activity and PAL genes expression under different ways of apical meristem development during the xylem structural elements' formation in unique woody plants B. pendula var. pendula with straight-grained wood and B. pendula var. carelica with figured wood. The differentiation process predominanced in straight-grained wood (B. pendula var. pendula) or proliferation - in the figured wood. The investigation was conducted in the radial row (cambial zone - differentiating xylem - mature xylem) during the active cambial growth period. The study aimed to study the xylogenesis processes occurring in the 16-year-old straight-grained silver birch (Betula pendula Roth) and Karelian birch (Betula pendula Roth var. carelica (Mercl.) Hämet-Ahti) with figured wood. Hydrogen peroxide and superoxide radical contents and peroxidase activity were determined spectrophotometrically. Gene expression for PAL family genes and the UPBEAT1 gene was assessed using qRT-PCR. Principal component analysis has confirmed trees with straight-grained and figured wood to be different according to UPBEAT1-ROS-POD-PAL system functioning. The higher superoxide radical/hydrogen peroxide ratio in figured Karelian birch, along with UPBEAT1 transcription factor and PAL genes upregulation, distinguished it from straight-grained silver birch. This metabolic picture confirmed the shift of Karelian birch xylogenesis towards proliferation processes, accompanied by ROS and phenolic compounds' flow and POD activity.

Free radical production induced by visible light in live fruit flies

Visible light triggers free radical production in alive and intact Drosophila melanogaster. We exposed fruit flies to red (613–631 nm), green (515–535 nm), and blue (455–475 nm) light while we monitored changes in unpaired electron content with an electron spin resonance spectrometer (ESR/EPR). The immediate response to light is a rapid increase in spin content lasting approximately 10 s followed by a slower, linear increase for approximately 170 s. When the light is turned off, the spin population promptly decays with a similar time course, though never fully returning to baseline. The magnitude and time course of the spin production depends on the wavelength of the light. Initially, we surmised that eumelanin might be responsible for the spin change because of its documented ability for visible light absorption and its highly stable free radical content. To explore this, we utilized different fruit fly strains with varying eumelanin content and clarified the relation of melanin types with the spin response. Our findings revealed that flies with darker cuticle have at least three-fold more unpaired electrons than flies with yellow cuticle. However, to our surprise, the increase in unpaired electron population by light was not drastically different amongst the genotypes. This suggests that light-induced free radical production may not exclusively rely on the presence of black melanin, but may instead be dependent on light effects on quinone-based cuticular polymers.

Modeling of water gas shift reaction using neural network trained on detailed kinetic mechanisms

For the optimization of a chemical reactor or its control, computational fluid dynamics (CFD) that considers accurate reaction models is effective. Although detailed kinetic mechanisms can accurately predict gas-phase reactions, integrating them with CFD is too computationally expensive. In contrast, global reactions have lower computational costs but significantly reduced accuracy outside of tuned conditions. This study proposes a method for constructing a model using a neural network to predict the reaction rate of water gas shift reaction based on detailed kinetic mechanisms. It includes techniques to avoid unrealistic solutions inherent to detailed kinetic mechanisms and methods to minimize biases in training data. The neural network input was log-transformed concentrations and inverse temperatures, and the output was the logarithm of the absolute value of the reaction rate and direction, enabling the prediction of bidirectional reactions over a wide temperature range. The quality of the dataset significantly impacted the accuracy of the neural network. Using a dataset with less bias in chemical species concentrations, the model achieved accuracy similar to detailed models while facilitating an over 400 times faster computation. The study also discussed the impact of temperature change rate, showing that at about 72 K/min, the detailed kinetic mechanism's solution can be accurately replicated. Still, at 720 K/min, the radical concentration deviates from the quasi-steady state, leading to discrepancies. This study opens up new possibilities for computational methods in the prediction and optimization of chemical reactions.

Chemical reaction process and dynamic characteristics of urea pyrolysis products in inhibiting gas explosion

During the coal mining process, gas explosions pose significant hazards, causing casualties and property losses. In order to develop new types of inhibitors for gas explosions, this paper explores the reaction mechanisms of urea pyrolysis products NH3 and HNCO inhibiting gas explosions based on density functional theory (DFT), transition state theory, and grand canonical ensemble Monte Carlo method (GCMC). It analyzes the reaction processes and kinetic characteristics of urea pyrolysis products with key radicals and gas molecules involved in explosions from a microscopic dynamic perspective. The results show that urea pyrolysis products exhibit good inhibition effects on active radicals involved in explosion reactions·NH3 and HNCO show stronger van der Waals forces in electrostatic attraction towards O2 and *H, respectively, and faster rate advantages in reaction rate constants. The lower Gibbs free energy barrier indicates higher reaction activity of pyrolysis products, thereby diluting the concentration of key radicals involved in explosion reactions and effectively inhibiting explosion key elementary reactions (R32, R38, R53, R57, R156, and R170). This study provides new insights into the microscopic inhibition mechanism of urea pyrolysis products on gas explosions, offering a new approach for designing more targeted modified inhibitors, which helps reduce the hazards of gas explosions during coal mining and provides scientific support and technical guidance for safe coal mining production.

Antioxidant activity of polyphenol compounds extracted from Nypa fruticans Wurmb. (Nipa palm) fruit husk with different ethanol concentration

Oxidative stress is a condition characterized by a higher content of free radicals than the potential antioxidants in the body. Exogenous antioxidants are needed to resolve this condition. The Nypa fruticans (Nipa palm) fruit husk is a source of polyphenol potential and can be used as a natural antioxidant agent. Therefore, this study aimed to determine the effect of ethanol concentration on polyphenol and tannin contents and their antioxidant activities. The polyphenol substances were extracted using several ethanol concentrations, whereas the antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl method. The results show that the ethanol concentration has no effect on the yield of extraction. However, it affects the total polyphenol and tannin contents with high levels in the 50% and 70% ethanol concentrations. Fifty percent ethanol exhibits more effective antioxidant activity when compared to other ethanol concentrations. Therefore, a 50% ethanol concentration is a suitable solvent to extract polyphenol and tannin substances from nipa palm fruit husk and can be used as an alternative natural antioxidant.

Effects of erythromycin on biofilm formation and resistance mutation of Escherichia coli on pristine and UV-aged polystyrene microplastics

Microplastics (MPs) and antibiotics co-occur widely in the environment and pose combined risk to microbial communities. The present study investigated the effects of erythromycin on biofilm formation and resistance mutation of a model bacterium, E. coli, on the surface of pristine and UV-aged polystyrene (PS) MPs sized 1–2 mm. The properties of UV-aged PS were significantly altered compared to pristine PS, with notable increases in specific surface area, carbonyl index, hydrophilicity, and hydroxyl radical content. Importantly, the adsorption capacity of UV-aged PS towards erythromycin was approximately 8-fold higher than that of pristine PS. Biofilms colonizing on UV-aged PS had a greater cell count (5.6 × 108 CFU mg−1) and a higher frequency of resistance mutation (1.0 × 10−7) than those on pristine PS (1.4 × 108 CFU mg−1 and 1.4 × 10−8, respectively). Moreover, erythromycin at 0.1 and 1.0 mg L−1 significantly (p < 0.05) promoted the formation and resistance mutation of biofilm on both pristine and UV-aged PS. DNA sequencing results confirmed that the biofilm resistance was attributed to point mutations in rpoB segment of the bacterial genome. qPCR results demonstrated that both UV aging and erythromycin repressed the expression levels of a global regulator rpoS in biofilm bacteria, as well as two DNA mismatch repair genes mutS and uvrD, which was likely to contribute to increased resistance mutation frequency.

INFLUENCE OF DINITROSALICYLIC ACID ON THE PROTECTIVE SYSTEM OF COTTON SEEDLINGS (Gossypium hirsutum L.)

Cotton growing, being an important agro-industrial object, is being improved through the introduction of new mechanisms to increase resistance to various external stress factors. Taking into account the previously studied phytohormones, the purpose of our study was to identify the effect of the salicylic acid derivative, dinitrosalicylic acid (DNSA), on the biochemical processes in the common cotton AP-317 genotype. It was established that low concentrations of DNSA-0.01 mM decreased production of NO radical, catalase and PPO activity, as well as absorption of phosphorus-anions from the nutrient medium, while higher doses of them has led to the stimulation of NO radical production, increased peroxidase activity, stabilized absorption of phosphorus anions. It was also found that at low concentrations of DNSA took place slightly activation of SOD activity, but not at relatively high concentration of DNSA. Electron paramagnetic resonance analysis of the root and leaf tissue of the plant showed an increase in the concentration of magnesium and iron ions when exposed to DNSA. It was also found that DNSA increased the concentration of lipid peroxide radicals at 0.1 mM in both tissues.

Degradation mechanisms of antibiotics in UV222/H2O2 and UV222/persulfate systems: Dual roles of inorganic anions

Advanced oxidation processes based on KrCl* excimer lamps (UV222-AOPs) have recently received widespread attention in water treatment due to their high radical yields. In this investigation, the degradation of two typical antibiotics, florfenicol (FLO) and ciprofloxacin (CIP), by UV222 and its combination with hydrogen peroxide (H2O2) or persulfate (PDS) were studied, respectively. The dual effects of inorganic anions on the degradation performance of UV222/UV222-AOPs were determined. It was found that NO3– significantly enhanced the photolysis of CIP, and the degradation rate constants increased from 1.03 × 10-4 mJ−1 cm2 (without NO3–) to 2.56 × 10-4 mJ−1 cm2 (with 1 mM NO3–). However, NO3– markedly inhibited the photolysis of FLO, leading to a decrease in the degradation rate constants from 1.18 × 10-3 mJ−1 cm2 (without NO3–) to 5.27 × 10-4 mJ−1 cm2 (with 1 mM NO3–). HCO3– was found to have a certain promoting effect on the photolysis of FLO and CIP, and SO42- has a negligible effect on the photolysis of both antibiotics. The above three inorganic ions decelerated the degradation of CIP and FLO in UV222-AOP, where NO3– exerted the most inhibition. Through LC-MS analysis and ECOSAR model, the main transformation products were individually determined and evaluated for toxicity. In addition, the performance of UV222-AOPs and UV254-AOPs in reclaimed wastewater (RWW) treatment were compared, and the steady-state concentration of radicals was measured. This study provided novel insight into the application of UV222-AOPs in RWW treatment.