The Federal University of Pará (Portuguese: Universidade Federal do Pará, UFPA) is one of the three public universities maintained by the Brazilian federal government in the state of Pará. It was ranked as the 15th largest Brazilian university in a 2011 academic ranking by the number of enrollments. The university has over 40,000 students enrolled in its courses, which are offered across its many campuses in the cities of Belém, Abaetetuba, Altamira, Ananindeua, Bragança, Castanhal, Cametá, Capanema, Breves, Tucuruí and Soure. Among UFPA research teams, there are many nationally recognized groups, particularly in the fields of genetics, parasitology, tropical diseases and geosciences. The Federal University of Pará is the largest university in the North region of Brazil by enrollment and is a reference in the areas of Biomedical Sciences and Biology research, this last one mainly because of the Amazon Rainforest.
Dust emissions during particulate material handling operations, such as ore transfer and storage, constitute a major challenge to public health, environmental quality, and industrial sustainability. This study investigates the relationship between moisture content and dust emission reduction, with emphasis on the transition from an emissive to a suppression-dominated regime. Experiments were conducted in a dust tower using twelve granular products with distinct particle-size distributions. Tests were performed in triplicate at each moisture condition to ensure reproducibility. Results showed that dust emission decreases systematically with increasing moisture, following a characteristic sigmoidal response. Based on this behavior, two characteristic moisture parameters were defined. Critical moisture ωcr corresponds to the point at which dust emission decreases sharply, marking the onset of effective suppression. Threshold moisture ωth was determined using a 10% relative-decay criterion and represents the condition beyond which additional wetting produces negligible emission reduction, defining the practical upper limit for moisture conditioning. Both characteristic moisture and moisture content increased linearly with the cumulative fraction of particles smaller than 10 μm, demonstrating the dominant influence of granulometry on the moisture demand for dust control. A strong correlation was also observed between ωcr and ωth, indicating that critical moisture can serve as a practical predictor of the threshold moisture. These findings demonstrate that routine particle-size data can support the estimation of operational moisture targets without extensive dust-emission testing. Therefore, ωcr and ωth are physically grounded and operationally useful parameters for optimizing water consumption and designing dust mitigation strategies in industrial bulk material handling systems.
The transient current of cyclic enzymatic amperometric biosensors results from the coupling of species diffusion, nonlinear Michaelis-Menten kinetics, and electrochemical product conversion at the electrode. Two previously established cyclic reaction mechanisms are compared here within a common dimensionless framework to determine how reaction topology controls product redistribution and electrode flux. The complete nonlinear systems are solved by the Generalized Integral Transform Technique (GITT) without kinetic linearization, with selected results additionally checked against a separately derived MOL/FDM spatial discretization and exact limiting-case solutions. The reference formulation assumes uniform enzyme activity, negligible external mass-transfer resistance, limiting electrochemical conversion at the electrode, equal effective diffusivities, and a common Michaelis constant. Reassessment of published homotopy perturbation method (HPM) expressions separates the effects of kinetic linearization, boundary representation, and series truncation. Within the investigated parameter range, the second enzymatic step produces the strongest differentiation between the mechanisms: at α = 10 and Da1 = 100, increasing Da2 from 1 to 300 raises the current by factors of 5.16 and 124.5 in Models 1 and 2, respectively. The central mechanistic result is that identical substrate depletion and total-product formation can coexist with markedly different product partitioning and electrode fluxes. Additional GITT calculations show that this structural identity does not require K1=K2 and remains valid when DP1 = DP2 ≠ DS, but is generally lost when DP1 ≠ DP2. The results therefore distinguish topology-controlled behavior from assumption-dependent predictions and provide nonlinear reference solutions for interpreting cyclic amperometric responses.
Microplastic pollution has become pervasive across freshwater ecosystems worldwide, including the Amazon Basin, where increasing levels of plastic contamination have been reported. Despite growing evidence of microplastic (MP) ingestion in aquatic organisms, studies focusing on threatened species remain extremely scarce, particularly for estuarine elasmobranchs. Rays present high extinction risk among vertebrates and in majority are apex predators, which enhance direct interaction with MPs. The present study investigated, for the first time, MPs ingestion by threatened stingray species from the Amazon Estuary, assessing particles' occurrence and characteristics. Twelve individuals belonging to four elasmobranch species, incidentally caught by artisanal fisheries in Marajó Bay, were examined. Microplastics were detected in all specimens, totaling 181 particles. Fibers predominated (97%), followed by fragments (3%), with black (30.9%) and blue (30.4%) being the most frequent colors. Raman spectroscopy identified Polyester and Polyamide (Nylon) as the dominant polymers (25% each), followed by Polyethylene, Polypropylene, and Polyurethane (16.7% each), a polymer composition consistent with the major anthropogenic plastic previously reported in the Amazon Basin. Although ingestion levels varied considerably among individuals and species, contamination was ubiquitous. This study provides the first record of microplastic occurrence for the stingray species investigated, expanding current knowledge of plastic exposure in threatened Amazonian elasmobranchs. By establishing a baseline for future monitoring, our findings support the incorporation of plastic pollution into conservation assessments of threatened freshwater and estuarine rays.
Anesthesia is essential for minimizing stress and preserving fish welfare during routine handling, yet few natural agents have been evaluated through integrated behavioral, physiological, and mechanistic approaches. Although Laurus nobilis essential oil exhibits several bioactive properties, its effects on anesthetic behavior, cardiac electrophysiology, opercular activity, and potential molecular targets in fish remain poorly understood. This study investigated the anesthetic potential of eucalyptol-rich L. nobilis essential oil in juvenile Oreochromis niloticus by combining phytochemical, behavioral, electrophysiological, and computational analyses. Chemical composition was determined by GC-MS, and 144 fish were allocated to independent behavioral, electrocardiographic, and opercular cohorts and exposed by immersion to the corresponding control, vehicle, or essential-oil treatments. Induction and recovery times, heart rate, electrocardiographic intervals, ECG amplitude and power, opercular frequency, and opercular signal power were assessed. Eucalyptol (38.34%) and terpinyl acetate (14.46%) were the major constituents. The oil reduced the latency to loss of the postural reflex in a concentration-dependent manner, but higher concentrations prolonged recovery and intensified sinus bradycardia, electrocardiographic interval prolongation, and opercular depression, without detectable arrhythmias. Among the concentrations tested, 389.2 mg L-1 yielded the most balanced profile of induction, recovery, and physiological effects. Molecular docking, 100-ns molecular dynamics simulations, and MM-GBSA calculations supported structurally plausible interactions of the major constituents with GABAA and Na(v)1.5, with terpinyl acetate showing the most consistent computational performance. Overall, these findings support L. nobilis essential oil as a promising natural anesthetic for short-duration procedures in fish.
This study converts an industrial kaolin-mining waste into a zeolite-based adsorbent suitable for batch and continuous fixed-bed operation. Zeolite 4A was synthesized at semi-pilot scale in an 18 L stainless-steel reactor via a hydrothermal route and shaped into mechanically manageable pellets using a clay binder and charcoal as a pore-forming (porogenic) agent. The pellet formulation code denotes the dry-mix recipe: Z, B, and +C represent the zeolitic material, clay binder, and charcoal, respectively. At an adsorbent dosage of 5 g L-1, Z60B40+C10 exhibited a higher Cu(II) removal efficiency than Z70B30+C5, reaching 39.0 % and 26.5 %, respectively, after 300 min of contact. These results indicate that Cu(II) uptake at the pellet scale was dependent on pellet formulation under the investigated conditions. Equilibrium isotherm data obtained at 300 min were comparably described by the Langmuir, Sips, and Redlich-Peterson models, while the Langmuir equation estimated a maximum equilibrium capacity of 23.43 mg g-1. In the fixed-bed experiment conducted at an influent concentration of 75 mg L-1, a flow rate of 5 mL min- 1, and a bed height of 5.5 cm, the Z60B40+C10 pellets exhibited an empty-bed contact time of 7.26 min and a dynamic adsorption capacity of 2.261 mg g- 1. Among the models evaluated, the Yan model provided the best description of the experimental breakthrough behavior. The results support kaolin-waste-derived zeolite pellets as a promising structured adsorbent for Cu(II) removal, while further fixed-bed experiments under varied operating conditions are required to assess the performance and operating range of the system.
