Search Results (583)

The synthesis of “green ammonia” from “green hydrogen” represents a critical pathway for renewable energy integration and industrial decarbonization. This study investigates the green ammonia synthesis process using an axial–radial fixed-bed reactor equipped with three catalyst layers. A simplified two-dimensional physical model was developed, and a multiscale simulation approach combining computational fluid dynamics (CFD) with physics-informed neural networks (PINNs) employed. The simulation results demonstrate that the majority of fluid flows axially through the catalyst beds, leading to significantly higher temperatures in the upper bed regions. The reactor exhibits excellent heat exchange performance, ensuring effective preheating of the feed gas. High-pressure zones are concentrated near the top and bottom gas outlets, while the ammonia mole fraction approaches 100% near the bottom outlet, confirming superior conversion efficiency. By integrating PINNs, the prediction accuracy was substantially improved, with flow field errors in the catalyst beds below 4.5% and ammonia concentration prediction accuracy above 97.2%. Key reaction kinetic parameters (pre-exponential factor k₀ and activation energy Ea) were successfully inverted with errors within 7%, while computational efficiency increased by 200 times compared to traditional CFD. The proposed CFD–PINN integrated framework provides a high-fidelity and computationally efficient simulation tool for green ammonia reactor design, particularly suitable for scenarios with fluctuating hydrogen supply. The reactor design reduces energy per unit ammonia and improves conversion efficiency. Its radial flow configuration enhances operational stability by damping feed fluctuations, thereby accelerating green hydrogen adoption. By reducing fossil fuel dependence, it promotes industrial decarbonization. Full article

The anodic behavior of zinc electrodes is important for energy storage, corrosion protection, electrochemical processing, and other practical applications. This study investigates the anodic galvanostatic polarization of zinc foil and bulk electrodes in aqueous oxalic acid solutions, revealing significant differences in their electrochemical behavior, particularly in induction period durations. The induction period’s duration depended on electrolyte concentration, current density, and temperature. Notably, the temperature dependence of the kinetics exhibited contrasting trends: the induction period for foil electrodes increased with temperature, while that of bulk electrodes decreased. Chemical analysis and polishing treatment comparisons showed no significant differences between the foil and bulk electrodes. However, Scanning Electron Microscopy (SEM) observations of samples anodized at different temperatures, combined with Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP-OES) analysis of dissolved electrode material, provided insights into the distinct anodic behaviors. X-ray Diffraction (XRD) studies further confirmed these findings, revealing a crystallographic orientation dependence of the anodic behavior. These results provide detailed information about the electrochemical properties of zinc electrodes, with implications for optimizing their performance in various applications. Full article

Gypsum (CaSO₄·2H₂O) crystallization underpins numerous industrial processes, yet its response to chemical admixtures remains incompletely understood. This study investigates diffusion-controlled crystal growth in a coaxial test tube system to evaluate how three Sika^® ViscoCrete^® superplasticizers—430P, 111P, and 120P—affect nucleation, growth kinetics, morphology, and thermal behavior. The superplasticizers, selected for their surface-active properties, were hypothesized to influence crystallization via interfacial interactions. Ion diffusion was maintained quasi-steadily for 12 weeks, with crystal evolution tracked weekly by macro-photography; scanning electron microscopy and thermogravimetric/differential scanning were performed at the final stage. All admixtures delayed nucleation in a concentration-dependent manner. Lower dosages (0.5–1.0 wt%) yielded platy-to-prismatic morphologies and higher dehydration enthalpies, indicating more ordered lattice formation. In contrast, higher dosages (1.5–2.0 wt%) produced denser, irregular crystals and shifted dehydration to lower temperatures, suggesting structural defects or increased hydration. Among the additives, 120P showed the strongest inhibitory effect, while 111P at 0.5 wt% resulted in the most uniform crystals. These results demonstrate that ViscoCrete^® superplasticizers can modulate gypsum crystallization and thermal properties. Full article

Doxorubicin (DOX) is widely used for the treatment of several tumors, but considerable dose-dependent side effects on many normal tissues, including bones, have been reported. The aim of the present study was to follow for the first time the kinetics of DOX accumulation/clearance in the non-vascularized intervertebral disc (IVD), as well as to assess the drug’s biological action in the annulus fibrosus (AF) and nucleus pulposus (NP) IVD cells and tissues. DOX was administered intravenously to rabbits before the isolation of IVDs, in which DOX quantification was performed using a highly sensitive LC-HRMS/MS analytical method. The effect of the drug on IVD cells’ physiology was assessed in vitro, while IVD tissue quality post-DOX administration was studied in vivo through histological analysis. DOX delivery was found significantly lower in the IVD compared to the highly vascularized skin, declining from the outer AF to the inner NP. The low DOX concentrations reaching the IVDs had marginal effects on cells’ viability, intracellular redox status, and p38 MAPK activation, while they did not evoke cellular senescence. Most importantly, the drug did not negatively affect ECM integrity, as collagen and proteoglycan content remained stable in vitro and in vivo. Full article

As a result of the catalytic decomposition of H₂O₂, hydroxyl radicals are produced. Hydroxyl radicals are strong oxidants and effectively inactivate bacteria, ensuring water disinfection without toxic chlorinated organic by-products. The kinetics of bacterial inactivation were studied in a laboratory-scale flow catalytic reactor. A granular cobalt ferrite catalyst was thoroughly characterized using XRD and XRF techniques, SEM with EDS, and Raman spectroscopy. At lower H₂O₂ concentrations, H₂O₂ decomposition follows first-order reaction kinetics. At higher H₂O₂ concentrations, the obtained kinetics lines suggest that the reaction order increases. The kinetics of bacterial inactivation in the developed flow reactor depends largely on the initial number of bacteria. The initial bacterial concentrations in laboratory tests were within the range typical of real river water. A regression model was developed that relates the degree of bacterial inactivation to the initial number of bacteria, the initial H₂O₂ concentration, and the contact time of water with the catalyst. Full article

Background: Antibiotics at sub-inhibitory concentrations can rewire bacterial regulatory networks, impacting virulence. Objective: The way that exposure to selected antibiotics (ciprofloxacin, amikacin, azithromycin, ceftazidime, and meropenem) below their minimum inhibitory concentration (sub-MIC) modulates the physiology of Pseudomonas aeruginosa is examined in this study using growth-phase-resolved analysis. Methods: Standard P. aeruginosa strain cultures were exposed to ¼ and ½ MIC to determine the growth kinetics under antibiotic stress. The study measured protease and pyocyanin production and the expression level of important quorum sensing and virulence genes (lasI/R, rhlI/R, pqsR/A, and phzA) at different growth phases. Results: Meropenem produced the most noticeable growth suppression at ½ MIC. Sub-MIC antibiotics did not completely stop growth, but caused distinct, dose-dependent changes. Azithromycin eliminated protease activity in all phases and had a biphasic effect on pyocyanin. Ciprofloxacin consistently inhibited both pyocyanin and protease in all phases. The effects of amikacin varied by phase and dose, while β-lactams markedly increased pyocyanin production during the log phase. In contrast to the plateau phase, when expression was often downregulated or unchanged, most quorum-sensing- and virulence-associated genes showed significant upregulation during the death phase under sub-MIC exposure. Conclusions: These findings indicate that sub-MIC antibiotics act as biochemical signal modulators, preserving stress-adapted sub-populations that, in late growth phases, activate quorum sensing and stress tolerance pathways. Full article

The concurrent dissolution and early hydration of tricalcium aluminate (C₃A) and tetracalcium aluminoferrite (C₄AF) critically govern early-stage reaction dynamics in Portland cement systems. However, their mutual kinetic interactions during reaction, particularly sulfate-dependent modulation mechanisms, remain poorly understood. Using in-situ digital holographic microscopy (DHM), this study resolved their interaction mechanisms during co-dissolution in aqueous and sulfate-bearing environments. Results reveal asymmetric modulation: while C₄AF’s dissolution exhibited limited sensitivity to C₃A’s presence, C₃A’s kinetics were profoundly altered by C₄AF through sulfate-concentration-dependent pathways, which originated from two competing C₄AF-mediated mechanisms: (1) suppression via common-ion effects, and (2) acceleration through competitive sulfate species adsorption. These mechanistic insights would provide a roadmap for optimizing cementitious materials through optimized reaction pathways. Full article

The enzyme ABH2, one of nine human DNA dioxygenases of the AlkB family, belongs to the superfamily of Fe(II)/α-ketoglutarate-dependent dioxygenases and plays a crucial role in the direct reversal repair of nonbulky alkyl lesions in DNA nucleobases. ABH2 has broad substrate specificity, directly oxidizing DNA damages such as N¹-methyladenine, N³-methylcytosine, 1,N⁶-ethenoadenine, 3,N⁴-ethenocytosine, and a number of others. In our investigation, we sought to uncover the subtleties of the mechanisms governing substrate specificity in ABH2 by focusing on several critical amino acid residues situated in its active site. To gain insight into the function of this enzyme, we performed a functional mapping of its active site region, concentrating on pivotal residues, participating in forming a damaged binding pocket of the enzyme (Val99 and Ser125), as well as the residues directly involved in interactions with damaged bases, namely Arg110, Phe124, Arg172, and Glu175. To support our experimental data, we conducted a series of molecular dynamics simulations, exploring the interactions between the ABH2 mutant forms, bearing corresponding substitutions and DNA substrates, and harboring various types of methylated bases, specifically N¹-methyladenine or N³-methylcytosine. The comparative studies revealed compelling data indicating that alterations in most of the studied amino acid residues significantly influence both the binding affinity of the enzyme for DNA and its catalytic efficiency. Intriguingly, the findings suggest that the mutations impact the catalytic activity of ABH2 to a greater extent than its ability to associate with DNA strands. Collectively, these results show how changes to the active site affect molecular dynamics and reaction kinetics, improving our understanding of the substrate recognition process in this pivotal enzyme. Full article

CSNPs synthesized via the ionic gelation method have emerged as a promising nanoplatform in diverse fields such as pharmaceuticals, nanotechnology, and polymer science due to their biocompatibility, ease of fabrication, and tunable properties. This study focuses on the development and characterization of LL37-loaded CSNPs, designed to enhance antibacterial efficacy while maintaining biocompatibility. This study pioneers a systematic loading optimization approach by evaluating the encapsulation efficiency (%EE) of antimicrobial peptide LL37 across multiple concentrations (7.5, 15, and 30 µg/mL), thereby identifying the formulation that maximizes peptide incorporation while preserving controlled release characteristics. The multi-concentration analysis establishes a new methodological benchmark for peptide delivery system development. To achieve this, CSNPs were optimized for size and stability by adjusting parameters such as the chitosan concentration, pH, and stabilizer. LL37, a potent antimicrobial peptide, was successfully encapsulated into CSNPs at concentrations of 7.5, 15, and 30 µg/mL, yielding formulations with favorable physicochemical properties. Dynamic light scattering (DLS) and Zeta sizer analyses revealed that blank CSNPs exhibited an average particle size of 180.40 ± 2.16 nm, a zeta potential (ZP) of +40.57 ± 1.82 mV, and a polydispersity index (PDI) of 0.289. In contrast, 15-LL37-CSNPs demonstrated an increased size of 210.9 ± 2.59 nm with an enhanced zeta potential of +51.21 ± 0.93 mV, indicating an improved stability and interaction potential. Field emission scanning electron microscopy (FE-SEM) analyses exhibited the round shaped morphology of nanoparticles. The release profile of LL37 exhibited a concentration-dependent rate and showed the best fit with the first-order kinetic model. Cytocompatibility assessments using the XTT assay confirmed that both blank and LL37-loaded CSNPs did not exhibit cytotoxicity on keratinocyte cells across a range of concentrations (150 µg/mL to 0.29 µg/mL). Notably, LL37-loaded CSNPs demonstrated significant antibacterial activity against E. coli and S. aureus, with the 15-LL37-CSNP formulation exhibiting superior efficacy. Overall, these findings highlight the potential of LL37-CSNPs as a versatile antibacterial delivery system with applications in drug delivery, wound healing, and tissue engineering. Full article

The contamination of aquatic systems by industrial dyes, particularly methylene blue (MB), presents a significant environmental challenge due to their chemical stability and toxicity. In this study, the development and application of a novel magnetic nanohybrid comprising multiwall carbon nanotubes (MWCNTs) functionalized with maghemite (γ-Fe₂O₃) nanoparticles biosynthesized using Eucalyptus globulus extract (denoted MWNT-NPE) is reported. The material was thoroughly characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Vibrating Sample Magnetometer (VSM), and Fourier-Transform Infrared (FTIR) techniques, revealing high crystallinity, mesoporosity, and superparamagnetic behavior. The MWNT-NPE exhibited exceptional MB adsorption performance under optimized conditions (pH 6, 0.8 g L⁻¹ dose, 40 min equilibrium), achieving a maximum adsorption capacity of 92.9 mg g⁻¹. Kinetic analysis indicated chemisorption and physisorption regimes depending on MB concentration, with the pseudo-second-order and Freundlich isotherm models providing the best fits of experimental data. FTIR spectroscopy demonstrated that the removal mechanism involves π–π stacking, hydrogen bonding, and electrostatic interactions between MB molecules and the composite’s surface functional groups. Notably, the magnetic nanohybrid retained over 98% removal efficiency across five regeneration cycles and successfully removed MB from synthetic effluents with efficiencies exceeding 91%. These findings highlight the synergistic adsorption and magnetic recovery capabilities of the bio-functionalized hybrid system, presenting a sustainable, reusable, and scalable solution for industrial dye remediation. Full article

Oxytetracycline (OTC) has served as an antibiotic to treat various bacterial infections in fish raised in aquaculture. Nonetheless, administering OTC in overly high doses can lead to adverse side effects in fish and also negatively impact on their surroundings. The objective of this work was to evaluate the expression levels of immune markers such as TLR-1, TLR-2, IκB-α, MyD88, NF-κB, IFN-γ, and IL-6 in intestinal cell primary culture (foregut, midgut, and hindgut) using qRT-PCR, and in addition, to assess the in vivo response to different doses of OTC in coho salmon at different times. The expression levels of all genes increased significantly after 1 h on day 1 with high doses of OTC compared with control conditions in all tissues under both approaches (in vivo and in vitro). However, the transcriptional responses decreased to 3, 6, and 12 h in vitro and day 3 in vivo. In conclusion, the transcriptional responses were differentially modulated by OTC in the three intestinal portions under both experimental conditions. These results demonstrate for the first time in primary cell culture fish that the expression of immune biomarkers in all tissues induces a differential response of these genes, depending on the concentration of OTC and the kinetics of time. This study offers valuable insights that can be applied to enhance aquaculture, determine optimal drug doses, and improve fish health. Full article

This study investigates the dynamic operation of a pilot-scale precipitation reactor designed to produce oxygenated phosphocalcium apatites with controlled composition and low crystallinity, closely mimicking the mineral phase of bone. Our approach is based on integrating kinetic monitoring and dynamic reactor control to direct the formation of apatites with tailored structural and chemical properties. Three synthesis routes were explored using CaCO₃, Ca(NO₃)₂, and CaCl₂ as calcium precursors, under optimized Ca/P molar ratios. The evolution of ionic concentrations (Ca²⁺, PO₄³⁻), peroxide and molecular oxygen incorporation, and carbonate content was monitored over a reaction time range of 2 min to 4 h. Characterization by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and chemical analysis revealed a time-dependent transformation of amorphous phases into poorly crystalline apatites with specific textures. After 60 min, the Ca/P atomic ratio stabilized at approximately 1.575, and the resulting apatites exhibited structural features comparable to those of human bone. This study highlights the influence of reactor operation time on precipitation kinetics and the properties of bioactive apatites in a scalable system. The results offer promising prospects for the large-scale production of bone-mimetic materials. However, the lack of biological validation remains a limitation. Future studies will assess the cytocompatibility and bioactivity of these materials to confirm their potential for biomedical applications. Full article

This study investigates the efficient and enantioselective hydrolysis of ester bonds through a series of biotransformations employing various photobiocatalysts. A racemic mixture of 1-phenylethyl acetate served as the model substrate. The described research identified three strains exhibiting the highest biocatalytic activity: Nostoc cf-muscorum (CCALA 129), Leptolyngbya foveolarum (CCALA 76), and Synechococcus bigranulatus (CCALA 187). Their application led to the complete hydrolysis of the starting reagent, yielding both the unreacted ester and its corresponding alcohol in an enantioselective manner. Notably, the selectivity, expressed as S, reached an impressive value of 283 in certain outcomes. The photobiotransformations were conducted under varying conditions, with particular focus on two essential parameters: the duration of the process, crucial for kinetically controlled reactions, and light exposure, critical for light-dependent organisms. The representative results highlight the efficacy of these biocatalysts. For instance, using Leptolyngbya foveolarum (CCALA 76), Nostoc cf-muscorum (CCALA 129), and Synechococcus bigranulatus (CCALA 187) facilitated the production of 1-(R)-phenylethanol with enantiomeric excesses (ee) of 89%, 88%, and 86%, respectively, at a conversion degree of approximately 50%. These processes also yielded an optically enriched mixture of the unreacted substrate, 1-(S)-phenylethyl acetate. Specifically, in the case of Leptolyngbya foveolarum (CCALA 76), the ee of the unreacted ester reached up to 98%. Light exposure emerged as a key factor influencing selectivity factor (S). Adjusting this parameter allowed us to achieve an E value of up to 283 for the formation of 1-(R)-phenylethanol with an ee > 99% when utilizing the Nostoc cf-muscorum (CCALA 129) strain. Furthermore, light intensity proved crucial for scaling up these processes. Significant results were obtained with Synechococcus bigranulatus, particularly at substrate concentrations ranging from 1 to 10 mM under limited exposure. Here, the conversion degree was 55%, the ee of the (R)-alcohol was 86%, and the selectivity factor (S) value was 21. Full article

Ammonia fuel is regarded as a promising zero-carbon alternative to diesel in next-generation marine engines. However, the high-temperature ammonia-rich environment poses significant corrosion challenges to hot-end components such as valves. This study investigates the corrosion behavior of Ni80A alloy marine valves under the coupled effects of a high temperature and ammonia atmosphere. Using computational fluid dynamics (CFD), the service temperature of the valve and the ammonia concentration distribution inside the engine cylinder were identified. High-temperature corrosion experiments were conducted with a custom-designed setup. Results show that corrosion kinetics accelerated markedly with temperature: the initial corrosion rate at 800 °C was four times that at 500 °C, and the maximum corrosion layer thickness reached 37 μm—double that at lower temperatures. Microstructural analysis revealed a transition from a dense, defect-free corrosion layer at 500 °C to a non-uniform layer with coarse CrN particles and aggregated nitrides at 800 °C. Notably, surface hardness increased at both temperatures, peaking at 590 HV at 500 °C, while matrix hardness at 800 °C declined due to γ′ phase coarsening and grain growth. This work provides detailed insight into the temperature-dependent ammonia corrosion mechanisms of marine Ni-based alloy valves, offering essential data for material design and durability assessment in ammonia-fueled marine engines. Full article

Lactic acid bacteria are well known for hydrolyzing milk proteins, but their application to plant proteins remains limited. This study evaluated the ability of the cell-wall-anchored PrtS protease from two Streptococcus thermophilus strains to hydrolyze rapeseed albumins (RAs), aiming to generate bioactive peptides with potential food functionality. The specific activity of PrtS was first determined using a chromogenic substrate. RAs were then hydrolyzed using 10X- and 100X-concentrated cell pellets of each strain to assess the hydrolysis kinetics and the enzymatic mechanism. The results showed concentration-dependent hydrolysis, with protein conversion and the degree of hydrolysis increasing threefold at 100X for both strains. Despite the increased hydrolysis, the peptides produced had similar average sizes, averaging at five amino acids, indicating a consistent “one-by-one” cleavage mechanism. The in vitro testing of the RA hydrolysates produced with 100X PrtS from S. thermophilus LMD-9 revealed dose-dependent antioxidant activity comparable to native RAs. Importantly, unlike native RAs, these hydrolysates did not induce increased secretion of the pro-inflammatory mediator IL-8 in inflamed HT-29 cells, suggesting a reduced pro-inflammatory potential. These findings demonstrate that PrtS protease from S. thermophilus can effectively hydrolyze rapeseed proteins to produce functional hydrolysates with improved bioactivity profiles. Such hydrolysates have promising applications as functional ingredients in plant-based food products, contributing both to health benefits and potential food preservation through antioxidant activity. Full article