Purpose To evaluate the influence of a 25% alpha-tocopherol antioxidant gel (AT) and a 50% DL-α-lipoic acid antioxidant solution (AL) on coronal fracture resistance and the integrity of the adhesive interface between coronal dentin and a universal adhesive system (Ambar Universal APS), compared with a 10% sodium ascorbate gel (AS), after internal bleaching with 35% or 40% hydrogen peroxide. Materials and methods Two hundred bovine incisors were used: 80 teeth for fracture resistance and fracture pattern analyses, 80 crowns for resin tag evaluation, and 40 crowns for microtensile bond strength and failure mode analyses. Specimens were allocated according to hydrogen peroxide concentration (35% or 40%) and antioxidant protocol: control (CO), sodium ascorbate (AS), alpha-tocopherol (AT), and DL-α-lipoic acid (AL). Data were analyzed using appropriate statistical tests with a significance level of 5%. Results Sodium ascorbate and alpha-tocopherol exhibited the highest fracture resistance and microtensile bond strength values, whereas sodium ascorbate promoted the greatest resin tag formation. The control groups showed the lowest values for the evaluated mechanical and adhesive properties. DL-α-lipoic acid demonstrated intermediate performance. No significant differences were observed between the 35% and 40% hydrogen peroxide protocols. Conclusion The application of antioxidants after intracoronal bleaching resulted in higher fracture resistance and bond strength compared with the bleached control protocols. Under the experimental conditions evaluated, the sodium ascorbate and alpha-tocopherol protocols showed the most favorable overall performance.
The COVID-19 pandemic triggered an unprecedented economic shock, disrupting business operations and demand across sectors. This study examines the impact of the COVID-19 pandemic on the capital structure of small and medium-sized enterprises (SMEs) in the Portuguese hotel sector, a core segment of the hospitality industry and one of the most severely affected by the crisis. Using a panel dataset of private hotel firms in Portugal, we find a significant reduction in total debt during the pandemic. Decomposing debt by maturity reveals that firms reduced short-term borrowing while expanding long-term financing, indicating a recomposition of the debt structure during the pandemic. Furthermore, when firms are segmented by size, the reduction in total leverage was concentrated among smaller, financially constrained firms, while the expansion in long-term financing was observed among larger, financially unconstrained firms. A further decomposition of total liabilities into financial and operating components reveals that financial and operating liabilities responded in opposite directions during the pandemic: operating liabilities contracted, while financial liabilities, notably long-term financial debt, increased. This study contributes to the literature on capital structure, corporate finance, and crisis management by providing one of the first empirical assessments of COVID-19's effects on SME financing in a tourism-dependent, bank-reliant economy, a context that remains understudied. It also extends prior research by focusing on private rather than public firms. By examining a highly vulnerable sector, the findings offer insights into financial resilience during crises and provide policy implications for improving liquidity access and strengthening financial stability among tourism-dependent hotel SMEs.
The development and application of a lab-made screen-printed electrode (SPE) modified with electrodeposited gold nanoparticles (AuNPs), graphitic carbon nitride (g-C3N4) and cetyltrimethylammonium bromide (CTAB) for the electrochemical determination of uric acid (UA) is reported. The SPE/AuNPs/g-C3N4@CTAB platform was optimized to enhance its electroactive surface area, conductivity, and charge-transfer kinetics, as confirmed through scanning electronic microscopy, energy-dispersive x-ray spectroscopy, Raman spectroscopy, contact angle analysis, cyclic voltammetry, and electrochemical impedance spectroscopy. Differential pulse voltammetry measurements demonstrated a linear response for UA concentrations between 50 and 600 µmol L⁻¹, with a limit of detection of 1.95 µmol L⁻¹, fully covering clinically relevant ranges. The sensor exhibited high selectivity against common interferents, as well as excellent stability and optimal performance at physiological pH of 7.0, consistent with UA dissociation equilibria. The application of the SPE/AuNPs/g-C3N4@CTAB sensor for UA detection in human whole blood, serum, and plasma samples showed promising results comparable to those obtained from standard enzymatic colorimetric assays, confirming the analytical reliability of the device. The computational analysis by DFT calculations demonstrated that the Eads of UA to the complete modified sensor decreased at − 0.23 eV when compared to the SPE/AuNPs/g-C3N4. This reduction provides strong theoretical evidence supporting the influence of the CTAB modifier on the UA detection mechanism. Overall, the proposed modified SPE platform provides a simple, cost-effective, and portable alternative tool for UA monitoring in clinical samples.
Phosphorus is essential for plant growth, but its low availability and rapid immobilization in soil create challenges for agricultural production. A promising solution is the use of plant growth-promoting fungi, such as Trichoderma which can solubilize phosphate, produce phytohormones and enzymes, and protect plants from pathogens. This study aimed to investigate the phosphate-solubilizing and plant growth-promoting potential of Trichoderma isolates from the Brazilian Cerrado. Twenty-two Trichoderma strains were screened for their ability to solubilize inorganic phosphates and commercial fertilizers. The most efficient isolate was further evaluated for enzyme production (acid phosphatase, phytase), siderophores, indole-3-acetic acid, tolerance to abiotic stresses (pesticides, salinity, drought), and molecular identification. Its effects on maize growth were tested under greenhouse conditions using half the recommended rate of phosphorus fertilizer. Trichoderma G41 was the most efficient in solubilizing Ca3(PO4)2 (645.26 µg P mL− 1), AlPO4 (814.66 µg P mL− 1), FePO4 (132.76 µg P mL− 1), and commercial fertilizers.The strain was found to produce acid phosphatase (4.37 U mL− 1), phytase (1.51 U mL− 1), siderophores (74
The use of plant-derived nutraceuticals in aquaculture has increased, including in ornamental species. Guavira (Campomanesia guazumifolia) is a native Cerrado plant with reported antioxidant and anti-inflammatory properties. This study evaluated the toxicity and functional effects of C. guazumifolia leaf decoction as a feed additive for Geophagus pyrocephalus. Acute toxicity assays were conducted using Artemia salina (1.5–1000 µg mL⁻¹) and juvenile fish (0.1–500 µg mL⁻¹), alongside a 30-day feeding trial with dietary inclusion levels of 0, 250, 500, 1000, and 2000 mg kg⁻¹. The decoction exhibited high toxicity, with LD₅₀ values of 23.29 µg mL⁻¹ for A. salina and 50.03 µg mL⁻¹ for G. pyrocephalus. In fish, mortality increased markedly at concentrations ≥ 100 µg mL⁻¹, accompanied by elevated plasma glucose and severe gill lesions, including epithelial hyperplasia, lamellar fusion, and necrosis. Despite this toxicity, dietary supplementation at 250 mg kg⁻¹ significantly enhanced muscle antioxidant activity, with superoxide dismutase (SOD) levels increasing by approximately 2.5-fold compared to the control (p < 0.05), without affecting growth performance or survival. In contrast, higher inclusion levels (≥ 1000 mg kg⁻¹) were associated with reduced condition factor and increased hepatic alanine aminotransferase (ALT), indicating metabolic stress. In conclusion, C. guazumifolia leaf decoction presents a narrow safety margin, combining pronounced toxicity at relatively low concentrations with beneficial antioxidant effects at low dietary inclusion. The dose of 250 mg kg⁻¹ is suggested as a safe and functional level for G. pyrocephalus, highlighting the importance of dose optimization for its application in ornamental aquaculture.
