Search Results (216)

The phase equilibria of the Si-C-Cu ternary system at 700 °C and 810 °C were experimentally investigated for the first time. Fifteen key alloys were prepared via powder metallurgy and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Isothermal sections were constructed based on the identified equilibrium phases. At 700 °C, eight single-phase regions and six three-phase regions—(C)+(Cu)+hcp, (C)+hcp+γ-Cu₃₃Si₇, (C)+γ-Cu₃₃Si₇+SiC, γ-Cu₃₃Si₇+SiC+ε-Cu₁₅Si₄, SiC+ε-Cu₁₅Si₄+η-Cu₃Si(ht), and SiC+(Si)+η-Cu₃Si(ht)—were determined. At 810 °C, nine single-phase regions and seven three-phase regions were identified. The solubility of C and Si/Cu in the various phases was quantified and found to be significantly higher at 810 °C compared to 700 °C. Key differences include the presence of the bcc (β) and liquid phases at 810 °C. The results demonstrate that higher temperatures promote increased mutual solubility and reaction tendencies among Cu, C, and Si. Motivated by these findings, the influence of vacuum hot pressing parameters on SiC-fiber-reinforced Cu composites (SiC_f/Cu) was investigated. The optimal processing condition (1050 °C, 60 MPa, 90 min) yielded a high bending strength of 998.61 MPa, attributed to enhanced diffusion and interfacial bonding facilitated by the high-temperature phase equilibria. This work provides essential fundamental data for understanding interactions and guiding processing in SiC-reinforced Cu composites. Full article

Cyclic voltammetry (CV) is an accessible, readily available, non-expensive technique that can be used to search for the interaction of compounds with DNA and detect the strongest DNA-binding from a set of compounds, therefore allowing for the optimization of the number of cytotoxicity assays. Focusing on this electrochemical approach, the study of twenty-seven camphorimine silver complexes of six different families was performed aiming at detecting interactions with calf thymus DNA (CT-DNA). All of the complexes display at least two cathodic waves attributed respectively to the Ag(I)→Ag(0) (higher potential) and ligand based (lower potential) reductions. In the presence of CT-DNA, a negative shift in the potential of the Ag(I)→Ag(0) reduction was observed in all cases. Additional changes in the potential of the waves, attributed to the ligand-based reduction, were also observed. The formation of a light grey product adherent to the Pt electrode in the case of {Ag(OH)} and {Ag₂(µ-O)} complexes further corroborates the interaction of the complexes with CT-DNA detected by CV. The morphologic analysis of the light grey material was made by scanning electronic microscopy (SEM). The magnitude of the shift in the potential of the Ag(I)→Ag(0) reduction in the presence of CT-DNA differs among the families of the complexes. The complexes based on {Ag(NO₃)} exhibit higher potential shifts than those based on {Ag(OH)}, while the characteristics of the ligand (^AL-Y, ^BL-Y, ^CL-Z) and the imine substituents (Y,Z) fine-tune the potential shifts. The energy values calculated by docking corroborate the tendency in the magnitude of the interaction between the complexes and CT-DNA established by the reaction coefficient ratios (Q_[Ag-DNA]/Q_[Ag]). The molecular docking study extended the information regarding the type of interaction beyond the usual intercalation, groove binding, or electrostatic modes that are typically reported, allowing a finer understanding of the non-covalent interactions involved. The rationalization of the CV and cytotoxicity data for the Ag(I) camphorimine complexes support a direct relationship between the shifts in the potential and the cytotoxic activities of the complexes, aiding the decision on whether the cytotoxicity of a complex from a family is worthy of evaluation. Full article

The catalytic activity of monolayer and bilayer boron-doped edge black phosphorene nanoribbons (BPNRs) as electrocatalysts for the nitrogen reduction reaction (NRR) was investigated using first-principles calculations based on density functional theory (DFT). The results indicate that boron incorporation facilitates effective N₂ adsorption at specific BPNR edges, thereby achieving superior NRR electrocatalytic performance. Through NRR screening criteria, six candidate edges (B@ZZ₃-1, B@ZZ₄-1, B@AC₀-1, B@ZZ₀^AA-1, B@ZZ₁^AB-3, and B@ZZ₄^AA-3) were identified. Electronic property analysis revealed that boron doping significantly reduces the bandgap of BPNRs and enhances catalytic activity by promoting electron accumulation at boron sites. Free energy pathway calculations demonstrated that B@AC₀-1, B@ZZ₀^AA-1, and B@ZZ₁^AB-3 exhibit overpotentials of 0.19 V, 0.28 V, and 0.15 V, respectively, during the NRR process, outperforming other phosphorus-based catalysts in activity. Full article

This work investigated the optical characteristics of BaWO₄ nanoparticles that were produced through direct mechanochemical synthesis at varying speeds and times. This research expands upon our previous study. We demonstrated that the mechanochemical activation of the precursor of BaCO₃ and WO₃, at elevated milling speeds (850 rpm), facilitates the formation of tetragonal BaWO₄ in a reduced reaction time. The final products were characterized by scanning electron microscopy (SEM), as well as Raman, infrared (IR), UV-Vis diffuse reflectance, and photoluminescence spectroscopies. The crystallite sizes and particles shapes were determined by X-ray diffraction and SEM analysis. Round particles with a size below 50 nm formed under different milling conditions. The Raman spectra of the synthesized samples confirmed the presence of a scheelite-type structure with the typical six distinct vibrational peaks. The symmetry of the structural WO₄ groups was determined by IR spectroscopy. The absorption spectra of both samples exhibited intensive peaks at 210 nm, and the calculated optical band gaps of BaWO₄ were 5.10 eV (3 h/500 rpm) and 5.24 eV (1 h/850 rpm). A strong (400 nm) and weak (465 nm) emission were observed for the BaWO₄ that was obtained at a higher milling speed, while wider emission at 410 nm was visible for the BaWO₄ that was prepared at a lower milling speed. The CIE coordinates of the mechanochemically synthesized BaWO₄ were located within the blue area, exhibiting various positions. Full article

Zinc-halogen batteries are usually based on two-electron transfer reactions from X⁻ to X₂. However, the halogen is capable of being further oxidized to higher valence states, thereby achieving the higher capacity of zinc- halogen batteries. Here, a six-electron reaction based on I⁻/I⁺ and Br⁻/Br⁰ is activated successfully by introducing KI into the electrolyte. ZIF-8-derived porous carbon (ZPC), serving as the host of halogen, effectively suppresses polybromide/polyiodide shuttle owing to the chemisorption/physical adsorption. Additionally, the adsorption of I⁻ on the surface of the zinc anode effectively inhibits the growth of dendrites and the formation of by-products. Consequently, zinc-bromine batteries exhibit outstanding electrochemical performance, including a specific capacity of 345 mAh g⁻¹ at 1 A g⁻¹ and an excellent capacity retention of 80% after 3000 cycles at 2 A g⁻¹. This strategy provides a novel way for enhancing the electrochemical performance of zinc-halogen batteries. Full article

Background/Objectives: Bacterial biofilms on root surfaces outside the apical foramen are linked to refractory apical periodontitis, as microorganisms can survive in extraradicular areas and cause persistent infections. This study aimed to precisely evaluate the relationship between extraradicular biofilm and persistent periapical periodontitis through an overview of case reports. Methods: A systematic search of PubMed, Web of Science, Scopus, Embase and ScienceDirect databases was conducted up to June 2023. Keywords included “extraradicular infection”, “wet canal”, “wet canals”, “extraradicular mineralized biofilms”, and “calculus-like deposit”. Only case reports meeting the inclusion criteria were analyzed. Results: Fifteen cases of extraradicular infection were identified, involving eight women and six men aged between 18 and 60 years. These cases included nine failed treatments confirmed through complementary methods such as histobacteriologic analysis, scanning electron microscopy (SEM), or polymerase chain reaction (PCR). Among these, four patients (six teeth) exhibited calculus-like deposits. Conclusions: Extraradicular biofilm is strongly associated with failed endodontic treatments, leading to persistent infections. A structured decision-making approach is essential. Before considering apical surgery, clinicians should prioritize intraradicular infection control through thorough irrigation, antimicrobial medicaments, and adjunctive disinfection techniques. When extraradicular biofilms or mineralized calculus are present, and symptoms persist after optimal intracanal disinfection, apical surgery should be performed. Full article

Formic acid has recently been considered one of the most promising liquid organic hydrogen carriers (LOHCs). Its decomposition to obtain H₂ has been fruitfully investigated during recent years using catalysts of a very diverse nature. Most of these catalysts lack stability, so finding stable materials under reaction conditions is highly desirable but challenging. In the present study, catalysts based on Pd nanoparticles supported on C₃N₄-modified activated carbon derived from biomass residues were developed, characterized, and assessed in the decomposition of formic acid in the liquid phase. These catalysts were prepared using a straightforward method that allowed different nitrogen contents to be achieved in the support and avoided the ex situ reduction in the Pd precursor. The results of the catalytic tests indicated the positive role of incorporating C₃N₄, leading to catalysts that displayed much better performance than the C₃N₄-free counterpart. The incorporation of C₃N₄ resulted in catalysts with small and well-distributed Pd nanoparticles, leaching resistance and modified electronic properties of the Pd species. As a result, promising catalytic activity was observed in the developed materials. Pd/AC_C₃N₄(19) attained an initial TOF of 2893 h⁻¹, and it preserved most of its catalytic activity for at least six consecutive reaction cycles, which is a remarkable characteristic of the developed catalytic system. Full article

Photooxidation imposes structural damage on proteins, and the amino acid tryptophan (Trp) is a key target for protein oxidation. The Trp radical cation (Trp^•⁺), as an oxidative product, can be reduced by plant phenols (φ-OH), a category of dietary phytochemicals essential for human health. This work is intended to investigate the efficacy of φ-OH regeneration of Trp from Trp^•⁺ as a function of φ-OH concentration and environmental pH. We have examined, by using laser flash photolysis, six different kinds of φ-OH in the aqueous system consisting of Trp and riboflavin as a photosensitizer. Taking syringic acid (Syr) as an example, upon systematically varying the pH from 2 to 10, the partition of Syr phenolate, Syr-O²⁻, increases from 0% to 70% and, accordingly, the rate of Trp regeneration increases from 4.8 × 10⁶ M⁻¹·s⁻¹ to 1.7 × 10⁸ M⁻¹·s⁻¹. It is found that the regeneration rate correlates with the driving force of the electron transfer (ET) reaction between φ-OH and Trp^•+, which can be well accounted for by Marcus’s ET theory (R² = 0.89). The λ = 0.43 ± 0.08 eV for the reorganization energy for ET from the plant phenols to the Trp^•⁺. The effects of φ-OH concentration, environmental pH, and ET driving force on the Trp regeneration reaction herein revealed are significant for enlightening further study of protein (anti)oxidation. Full article

The process of hydrogen peroxide decomposition, facilitated by copper oxide nanoparticles, produces reactive oxidants that possess the ability to oxidize multiple pollutants. CuO/Cu₂O hybrid nanoparticles were successfully synthesized through a thermal decomposition route and applied as a heterogeneous catalytic oxidant for a fluorescent dye, namely Basic Violet 10 (BV10) dye. The microstructure and morphology of the prepared catalyst were evaluated via X-ray diffraction (XRD) and a field-emission scanning electron microscope (FE-SEM), respectively. The produced nanoparticles (NPs) were induced through ultraviolet light as a green photodecomposition technology. The system parameters were investigated, and the optimal initial NP concentration, H₂O₂ concentration, and pH were assessed. The highest removal rate corresponding to 82% was achieved when 40 and 400 mg/L of NPs and H₂O₂ were introduced, respectively. The system could operate at various pH values, and the alkaline pH (8.0) was efficient in proceeding with the oxidation system that overcomes the limitation of the homogeneous acidic Fenton catalyst. The introduced catalyst demonstrated consistent sustainability, achieving a notable removal rate of 68% even after six consecutive cycles of use. This innovative technique’s accomplishment examines the feasibility of utilizing copper as a replacement for iron in the Fenton reaction, demonstrating efficacy over an extended pH range. Finally, the temperature effectiveness of the reaction showed that the reaction is exothermic in nature, working at a low energy barrier (20.4 kJ/mol) and following the pseudo-second-order kinetic model. Full article

The tomato is among the crops with the most extensive cultivated area and greatest consumption in our nation; nonetheless, secondary salinization of facility soil significantly hinders the sustainable growth of facility agriculture. Melatonin (MT), as an innovative plant growth regulator, is essential in stress responses. This research used a hydroponic setup to replicate saline stress conditions. Different endogenous levels of melatonin (MT) were established by foliar spraying of 100 μmol·L⁻¹ MT, the MT synthesis inhibitor p-CPA (100 μmol·L⁻¹), and a combination of p-CPA and MT, to investigate the mechanism by which MT mitigates the effects of salt stress on the photosynthetic efficiency of tomato seedlings. Results indicated that after six days of salt stress, the endogenous MT content in tomato seedlings drastically decreased, with declines in the net photosynthetic rate and photosystem performance indices (PI_total and PI_abs). The OJIP fluorescence curve exhibited distortion, characterized by anomalous K-band and L-band manifestations. Exogenous MT dramatically enhanced the gene (TrpDC, T5H, SNAcT, and AcSNMT) expression of critical enzymes in MT synthesis, therefore boosting the level of endogenous MT. The application of MT enhanced the photosynthetic parameters. MT treatment decreased the fluorescence intensities of the J-phase and I-phase in the OJIP curve under salt stress, attenuated the irregularities in the K-band and L-band performance, and concurrently enhanced quantum yield and energy partitioning ratios. It specifically elevated φP_o, φE_o, and ψ_o, while decreasing φD_o. The therapy enhanced parameters of both the membrane model (ABS/RC, DI_o/RC, ET_o/RC, and TR_o/RC) and leaf model (ABS/CS_m, TR_o/CS_m, ET_o/CS_m, and DI_o/CS_m). Conversely, the injection of exogenous p-CPA exacerbated salt stress-related damage to the photosystem of tomato seedlings and diminished the beneficial effects of MT. The findings suggest that exogenous MT mitigates salt stress-induced photoinhibition by (1) modulating endogenous MT concentrations, (2) augmenting PSII reaction center functionality, (3) safeguarding the oxygen-evolving complex (OEC), (4) reinstating PSI redox potential, (5) facilitating photosynthetic electron transport, and (6) optimizing energy absorption and dissipation. As a result, MT markedly enhanced photochemical performance and facilitated development and salt stress resilience in tomato seedlings. Full article

Better quality and odor of silage and normal microbial fermentation metabolism are mostly dependent on an appropriate moisture content. The purpose of this study was to determine the effects of different moisture content gradients (50, 60, 70, and 80%) on the bacterial community, odor, and quality of alfalfa silage at 60 days by using gas chromatography–mass spectrometry (GC–MS) and electronic nose, with six replicates per group. The results showed that there were significant differences in odor response intensity among all groups, among which the 80% group had the strongest reaction to terpenoids, sulfides, and nitrogen oxides. Similarly, the different volatile organic compounds (VOCs) were mainly terpenoids, alcohols, and ketones, such as pine, camphor, and menthol (e.g., carlin and levomenthol). The dominant bacterium was Enterococcus with higher fiber, pH, and ammonia nitrogen (NH₃-N) content but poorer quality and odor (p < 0.05). The differential VOCs in the 60% group were mainly heterocyclics, esters, and phenols with fruity, floral, and sweet odors such as 2-butylthiophene and acorone. Pediococcus and Lactiplantibacillus were the dominant bacteria, with higher crude protein (CP), water-soluble carbohydrates (WSC), and lactic acid (LA) contents, as well as better quality and odor (p < 0.05). The biosynthesis of terpenoids and steroids, biosynthesis of secondary metabolites, and biosynthesis of phenylpropanoids were the main metabolic pathways of differential VOCs. In conclusion, regulating moisture content can alter bacterial community and metabolites, which will encourage fermentation and enhance alfalfa silage quality and odor. Full article

Six N^C^N cyclometalated Ni(II) complexes [Ni(N^C^N)Cl] or [Ni(N^C^N’)Br] with symmetric N^C^N or non-symmetric N^C^N’ ligands in which the peripheral N-groups were varied with pyridine (Py), 4-thiazole (4Tz), 2-thiazole (2Tz), and 2-benzothiazole (2Btz) complementing the previously reported complexes with di(2-pyridyl)phenide ligands [Ni(Py(Ph)Py)X] X = Cl or Br. The non-symmetric [Ni(N^C^N’)Br] complexes were synthesized from NiBr₂ and N^CH^N’ protoligands through base-assisted nickelation, while the symmetric [Ni(N^C^N)Cl] complexes were received from the N^C(Cl)^N protoligands and [Ni(COD)₂] (COD = 1,5-cyclooctadiene). Introduction of 4Tz on both sides shifted the electrochemical gap ΔE_exp = E_ox–E_red and the long wavelength UV-vis absorption maxima of the complexes to higher energies, while 2Tz leads to a shift to lower energies. When introducing only one 4Tz or 2Tz as peripheral groups, the remaining PhPy moiety dominates the electronic properties and electrochemistry and photophysics are very similar to the Py(Ph)Py derivatives. In contrast to this, introduction of 2Btz shifts both values to lower energies, regardless of one or two 2Btz groups and the 2Btz moiety dominates the character of the frontier molecular orbitals of the complexes, as DFT calculations show. Long-wavelength UV-vis absorptions vary from 416 to 443 nm, and their energies correlate well with the first reduction potentials. Negishi-type C–C cross-coupling reactions gave total yields ranging from 1 to 60% and cross-coupling yields from 1 to 44%. The reactivities correlate roughly with the first reduction potentials. Facilitated reduction (E around –2 or higher) goes generally along with improved performance, making the thiazole-containing complexes interesting candidates for such catalysis. Full article

The northeastern Hunan district in the Jiangnan Orogen (South China) holds significant gold resources, whose genesis remains perplexing, especially in terms of the gold source and mineralization process. Yanzhupo (2.50 t @ 2.52 g/t) is a newly discovered gold deposit in the northeastern Hunan district and is characterized by multiple generations of pyrite. Its alteration/mineralization can be divided into three stages: (I) quartz-ankerite-pyrite; (II) quartz-ankerite-chlorite-pyrite-gold; (III) quartz-ankerite-calcite-pyrite. Petrographic observations and back-scattered electron (BSE) imaging revealed six generations of pyrite: Cu-Au rich bright rims (Py1a) and porous cores (Py1b) in Stage I, Py2a with homogenous textures, Py2b with oscillatory zoning and Py2c with homogenous textures in Stage II and Py3 with homogenous textures in Stage III. Galena Pb isotopes, similar to the Wangu deposit, and pyrite chemical compositions show that the ore-forming materials of Yanzhupo came from deep magma, and some metal elements may be extracted from deep basement by fluid-mineral interactions during the upward migration of hydrothermal-magmatic fluid. The positive correlation between Cu and Au in pyrite reflects the oxidized ore-forming fluids. The enrichment of Cu and Au in Py1a reflects the precipitation of pyrite under high temperature fluid, forming the primary enrichment of Au. Porous Py1b is characterized by lower trace elements than Py1a, sharp reaction front and rich chalcopyrite and galena inclusions, indicating Py1b formed via coupled dissolution-reprecipitation (CDR) reactions of Py1a. The CDR reactions promoted by the oxidizing fluid itself re-release Au into the fluid. From Py2a to Py2c, the contents of As, Sb and Pb first increased and then decreased, which may reflect the increase of fluid pH caused by sulfidation of the wall rocks and the impoverishment of ore-forming fluids caused by the precipitation of a large number of elements. The sulfidation of the wall rocks in Stage II destroyed the stability of the Au(HS)₂⁻ and Au (HS)S₃⁻ complexes and led to the deposition of native gold. The barren ore-forming fluids precipitated homogenous Py3 in a stable environment. Therefore, we think that the Yanzhupo gold deposit may have been associated with magmatic-hydrothermal activity, and the mineralization mechanism may be CDR reactions and sulfidation of the wall rocks. Full article

Mitigating global warming necessitates transitioning from fossil fuels to alternative energy carriers like hydrogen. Efficient hydrogen production via electrocatalysis requires high-performance, stable anode materials for the oxygen evolution reaction (OER) to support the hydrogen evolution reaction (HER) at the cathode. Developing noble metal-free electrocatalysts is therefore crucial, particularly for acidic electrolytes, to avoid reliance on scarce and expensive metals such as Ir and Ru. This study investigates a low-cost, solvent-free solid-state synthesis of CoSb₂O₆, focusing on the influence of calcination time and temperature. Six samples were prepared and characterized using powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) analysis, field-emission scanning electron microscopy (FESEM), and electrochemical techniques. A non-pure CoSb₂O₆ phase was observed across all samples. Electrochemical testing revealed good short-term stability; however, all samples exhibited Tafel slopes exceeding 200 mV dec⁻¹ and overpotentials greater than 1 V. The sample calcined at 600 °C for 6 h showed the best performance, with the lowest Tafel slope and overpotential, attributed to its high CoSb₂O₆ content and maximized {110} facet exposure. This work highlights the role of calcination protocols in developing Co-based OER catalysts and offers insights for enhancing their electrocatalytic properties. Full article

Zwitterionic polymers have garnered significant attention for their distinctive properties, such as biocompatibility, antifouling capabilities, and resistance to protein adsorption, making them promising candidates for a wide range of applications, including drug delivery, oil production inhibitors, and water purification membranes. This study reports the synthesis and characterization of zwitterionic monomers and polymers through the modification of linear, vinyl, and aromatic heterocyclic functional groups via reaction with 1,3-propanesultone. Four zwitterionic polymers with varying molecular structures—ranging from linear to five and six membered ring systems—were synthesized: poly(sulfobetaine methacrylamide) (pSBMAm), poly(sulfobetaine-1-vinylimidazole) (pSB1VI), poly(sulfobetaine-2-vinylpyridine) (pSB2VP), and poly(sulfobetaine-4-vinylpyridine) (pSB4VP). Their molecular weights, thermal behavior, and self-assembly properties were analyzed using gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and zeta potential measurements. The glass transition temperatures (Tg) ranged from 276.52 °C for pSBMAm to 313.69 °C for pSB4VP, while decomposition temperatures exhibited a similar trend, with pSBMAm degrading at 301.03 °C and pSB4VP at 387.14 °C. The polymers’ self-assembly behavior was strongly dependent on pH and their surface charge, particularly under varying pH conditions: spherical micelles were observed at neutral pH, while fractal aggregates formed at basic pH. These results demonstrate that precise modifications of the chemical structure, specifically in the linear, imidazole, and pyridine moieties, enable fine control over the thermal properties and self-assembly behavior of polyzwitterions. Such insights are essential for tailoring polymer properties for targeted applications in filtration membranes, drug delivery systems, and solid polymer electrolytes, where thermal stability and self-assembly play crucial roles. Full article