Ciência e Natura

Mathematical modeling of monodisperse nanoparticle concentration in aerosols subject to electric field using the Poisson–Nernst–Planck equation

Fran Sérgio Lobato — 2025-03-14

In recent decades, the study of particulate materials has gained significant attention from the scientific community. This is due to applications that can be developed, among which we can cite the risks to human health and the environment. As a consequence of this concern, classifying nanoparticles is a topic of considerable interest. One of the most used devices to classify nanoparticles in aerosols is the Differential Mobility Analyzer. From a mathematical point of view, particle concentration profiles have been obtained, preferably, considering constitutive relationships. In this contribution, the Poisson–Nernst–Planck equation is used to determine the concentration of monodisperse nanoparticles in aerosols subjected to an electric field. For this purpose, an inverse problem is proposed and solved considering real data and the Differential Evolution algorithm as an optimization tool. The results demonstrate that the proposed methodology was able to obtain good estimates considering the phenomenological model in relation to experimental points, as well as accurate estimates for intermediate profiles considering the Kriging approach. Finally, it is important to mention that the novelty of this contribution lies in predicting the concentration of monodisperse nanoparticles in aerosols subjected to an electric field using the Poisson–Nernst–Planck equation.

Geometry of a navigation problem: the $\lambda-$Funk Finsler Metrics

Newton Mayer Solórzano Chávez — 2025-03-14

We investigate the travel time in a navigation problem from a geometric perspective, with respect to a new class of Finsler metrics. We present the λ−Funk Finsler Metrics. The setting involves an open disk centered at the origin, representing a circular lake perturbed by a symmetric wind flow proportional to the distance from the origin with proportionality factor λ. The Randers metric, which is an important Finsler metric, derived from this physical problem, generalizes the well-known Euclidean metric (λ = 0) on the Cartesian plane and the Funk metric on the unit disk (λ = 1). We obtain the formula for distance, or travel
time, from point to point, and the circumference equations. In addition, we obtain the distance formulas from point to line and vice versa.

Forecast of total flows for medium-term horizon via data-driven modeling

Rute Santos Porto Lima — 2025-03-31

This study presents the application of artificial neural networks (ANN), k-nearest neighbors algorithm (KNN), and support vector regression (SVR) for modeling the prediction of inflows to the Sobradinho reservoir in Bahia, Brazil. Using the Weka software, six formulations were tested for 3-month forecasts, with data divided into cross-validation and calibration-validation schemes. Efficiency was evaluated using the Nash-Sutcliffe coefficient, highlighting the superiority of SVR. The inclusion of attributes such as average flow and precipitation improved efficiencies. The model using KNN with 13 neighbors was incorporated into an enhanced implicit stochastic optimization strategy for the operation of the reservoir. This model was compared to other operational methods, showing superiority in vulnerability index.

Pick's Theorem in two-dimensional lattices

Eleonesio Strey — 2025-03-14

In this article, a generalization of Pick's Theorem is presented, which establishes an expression for the area of simple polygons whose vertices are points of an arbitrary two-dimensional lattice, in terms of the determinant and the number of lattice points inside the polygon and on its boundary.

Analysis of the complexity of Homomorphic Encryption algorithms

Aline De Lurdes Zuliani Lunkes — 2025-04-11

Partially Homomorphic Cryptography plays a crucial role in preserving privacy during the processing of sensitive information. This work presents partially homomorphic encryption schemes applied to integers, which support only one homomorphic operation, either additive or multiplicative. We analyze the computational time complexities associated with encryption, decryption, homomorphic computation, and potential attacks on each scheme. Additionally, we compare the studied schemes, detailing their algorithms and highlighting their key efficiency and security characteristics.

Tropical aquaponic production of lemon balm, Melissa officinalis, using different Astyanax bimaculatus fingerling stocking densities

Bernardo Ramos Simões Corrêa — 2025-04-01

The relationship between the constituent organisms of aquaponics - fish, plants, and microorganisms - needs to be in biological harmony to favor the maximum performance of the species. Lemon balm (Melissa officinalis), a food and medicinal plant, as well as Astyanax bimaculatus, are species that can add value to the final products of aquaponics. The present experiment tested five treatments with different stocking densities of A. bimaculatus fingerlings (0.0, 0.1, 0.2, 0.3, and 0.4 fish L-1; T1, T2, T3, T4, and T5, respectively) in association with lemon balm at a density of 24 plants m-2 in media bed aquaponic systems installed in a greenhouse. The experimental design was completely randomized with three replications for each treatment, totaling 15 aquaponic systems analyzed. The results showed that for fish growth, T2 presented the best performance results, followed by T3 and T4, and finally T5; while for plants it was T3, followed by T4 and T5 which did not show differences between them, followed by T2, and finally T1. In all treatments, animal and plant growth were observed. The studied aquaponic systems demonstrated their viability for the production of the species, presenting satisfactory results, which can be interesting for further studies and producers.

Corn seed conditioning with ultraviolet light to mitigate salt stress

Raquel Stefanello — 2025-04-04

Seed priming with ultraviolet light is considered an effective seed treatment method that can promote synchronized germination and development, contributing to better performance in mitigating the negative effects caused by abiotic stress. The objective of this study was to analyze the effects of conditioning maize seeds with UV-C light under salinity-induced stress. Seeds were exposed to two doses of UV-C and sodium chloride. The seeds were sown on germitest paper, and the rolls were kept in a germination chamber (25 ±2 °C and 12 h photoperiod). Germination and seedling growth parameters were evaluated. The high salt concentration resulted in a lower percentage of germination and initial seedling growth. Pre-exposure of maize seeds to UV-C radiation proved to be effective in mitigating the deleterious effects of excess salt on both seed germination (3.42 kJ m^-2) and seedling growth (0.85 and 3.42 kJ m^-2). Therefore, it can be concluded that the application of UV-C light to condition maize seeds may be a promising strategy to mitigate the adverse effects of high salt concentrations.

Cultivation of Tagetes patula L. in copper contaminated soils

Leandra de Carvalho Lacerda — 2025-03-14

Leaf quality is one of the most valued commercial parameters in the cultivation of flowers and ornamental plants in vases, with soil or substrate conditions playing a fundamental role in its successful practice. Thus, the objective of this study was to evaluate the vegetative development of marigold (Tagetes patula L.) cultivated in soils contaminated by Cu, seeking to verify its soil phytoremediation potential for an agriculture with low environmental impact. The experiment took place in a greenhouse, using a completely randomized, 5x2 factorial design (added levels of Cu in the soil: 0 (no addition: control), 250, 500, 750 and 1,000 mg kg^-1 of copper sulfate and soil pH corrections: 5.5 and 6.0, according to soil analysis report), with five replications. This work evaluated phytotechnical parameters and translocation factors, bioaccumulation, bioconcentration and Cu extraction rate in plants. It was observed that the development of marigold plants was similar on both soil pH corrections according to the addition of Cu, affecting the aesthetic quality of the plants. In this context, it is concluded that the marigold species is tolerant to the cultivation in soils with excess Cu and is characterized as a Cu extracting plant, with low soil phytoremediation potential.

Clustering of spatio-temporal precipitation patterns in the Legal Amazon using deep convolutional autoencoder

Vander Augusto Oliveira da Silva — 2025-03-14

Identifying patterns in precipitation time series in a given region is fundamental for its socioeconomic development. Many studies on this topic have been carried out in Brazil, mainly in the Amazon region. This research aimed at the development of a computational method for analyzing time series of precipitation using machine learning techniques, aiming at a method capable of extracting complex characteristics from the data, obtaining a map of attributes in low dimensionality for pattern recognition and discovery of homogeneous regions with respect to precipitation in the Legal Amazon. The proposed model is trained to learn the main and most complex characteristics of the original data and present them in low dimensionality in latent space. After training, the observations of the reconstructed data showed good performance as evaluated by the RMSE and NRMSE metric with resulting values equal to 0.06610 and 0.3355 respectively. The result of the low-dimensional representation of the data was analyzed by a clustering structure using hierarchical clustering with Ward's method. This methodology carried out consistent groupings characterizing homogeneous regions in relation to precipitation data. In this way, demonstrating that the representation in low dimensionality carried the main characteristics of the time series of the studied data.

Inventory of greenhouse gas (GHG) emissions from the modal system on the port cargo route of Santa Catarina

Gabriela Lamim — 2025-03-14

Climate change has intensified in recent decades due to the increase in the concentration of greenhouse gases (GHG) arising mainly from human activities. The transport sector is one of those responsible for the increase in these concentrations, due to the incomplete burning of fossil fuels in the use of different modals, such as road and railway. However, these modals are very important for the Brazilian production flow, product imports, as well as other human needs and development. Considering these facts, the present study inventoried the greenhouse gas emissions of the modal system on the port cargo route of Santa Catarina. With this purpose, movement data of Santa Catarina´s ports, road and railway modals data were used, referring to 2020 year. The data were analyzed using the Brazilian greenhouse gas protocol tool - GHG Protocol (Scope 1), 2022 version. In addition to the base data, five other scenarios were analyzed, considering different increments that encourage the railway use expansion as a strategy to reduce emissions. As a result, a reduction in carbon dioxide equivalent (CO₂e) emissions was observed when using the rail modal compared to the road modal, since, when comparing scenario 5 (50% rail + 50% road) with the current scenario (12.1% rail + 87.9% road), there is a 43% reduction in emissions from the road sector. Such findings make clear the importance of encouraging strategic planning and investments to promote intermodality and optimize logistical efficiency in Santa Catarina through the transport matrix diversification as a way of promoting sustainability.

Chitosan/smectite spheres for methylene blue removal: preparation and characterization

Mateus Veras Pereira — 2025-04-01

Effluent treatment and water body decontamination are pressing global challenges due to high water consumption and industrial effluent generation. This study focused on developing efficient, cost-effective adsorbents for the removal of methylene blue, a widely used dye known for its toxicity. Chitosan (CS) and smectite clay composites were prepared and characterized using FTIR, XRD, and pHpzc analyses. FTIR confirmed the preservation of the functional groups of both materials in the prepared composite, whereas the diffractograms indicated a superficial interaction, as evidenced by the absence of shifts in the diffractogram peaks. The point of zero charge pH on the surface of the CS/Clay-180 and CS/Clay-580 composites was evaluated as 8.5 and 8.4, respectively. Adsorption experiments covered a pH range of 3 - 11, exposure times of up to 600 min and dye concentrations from 5 - 350 mg L^-1. Kinetic data followed first and second-order models, while the Freundlich model best described the experimental isotherms. Our composites exhibited excellent adsorption capacities, with maximum values of 45.4 mg g^-1 for CS/Clay-180 and 42.7 mg g^-1 for CS/Clay-580, at pH 10 and a contact time of 300 min. Therefore, the prepared CS/clay spheres proved to be effective and environmentally friendly adsorbents for the removal of methylene blue, contributing to the development of sustainable solutions for water purification.

Enhanced antioxidant and antimicrobial properties of lyophilized vitamin c concentrates from Malpighia emarginata (acerola): a comparative study

Flavia Maria Comachio — 2024-11-01

Vitamin C (Vit C) plays beneficial roles in the human body and has been used as a natural preservative in foods. However, there are no technological prospecting studies aimed at producing Vit C concentrates from Malpighia emarginata (acerola) nor antioxidant and antimicrobial evaluations of these products. In this context, this study aimed to compare Vit C concentrates obtained from acerola through two different drying methods (spray drying and freeze-drying), evaluating these preparations’ antioxidant and antimicrobial activities. The concentration of Vit C and phytochemical analyses were performed using chromatographic (HPLC) and spectroscopic (ESI-IT-MSn) methods. The antimicrobial activity was evaluated by microdilution and diffusion in a solid medium. Chemical analyses revealed the presence of six compounds, including Vit C and anthocyanins, considered markers for this species. The Vit C content was higher for freeze-drying compared to spray drying (16.30% and 10.74%, respectively). In the Minimum Inhibitory Concentration (MIC) test, the freeze-dried product also showed better activity against Escherichia coli and Staphylococcus aureus compared to the spray-dried product (0.0078 and 0.0312 g/mL, respectively). In the solid medium, both concentrates were active. The concentrates also showed antioxidant effects by the DPPH method. The results of this study provide convincing evidence that freeze-drying M. emarginata results in a higher concentration of Vit C and has promising antioxidant and antimicrobial effects.

Sustainable petrochemical plataform from Elephant Grass

Regiani Crystina Barbazelli — 2025-03-14

The objective of this research is to demonstrate the potential of elephant grass (Pennisetum purpureum Schum) as biomass for obtaining other value-added byproducts, such as biofuels, lignocellulosic ethanol, adsorbents, among others. Through the pyrolysis process, biochar and bio-oil with average yields of 24.45% and 4.92% were produced, respectively The main components found in the bio-oil were carboxylic acids (64.47%), followed by esters (19.74%). The carbohydrate adsorption percentage observed in the biochar was lower than that found in commercial activated carbon, which is desirable in the food industry. Through scanning electron microscopy (SEM), it was possible to observe that the biochar consists of non-uniform particles with numerous pores, suggesting its potential use as an adsorbent material. The (BET and LANGMUIR) surface area values did not yield significant results; however, there was an increase in pore size after the pyrolysis process. The glucose content found in this study was 70.33%, and the reducing sugar content was 14.24 g.L^-1. Based on the theoretical yield calculations for 2G ethanol, it is possible to infer a potential production of 0.88 tons of 2G ethanol per hectare of elephant grass planted per year. The calculated theoretical yield for levulinic acid (LA) was 35.16%, and for formic acid (FA), it was 14.07%. It is worth noting that the use of such waste for the production of biochar and bio-oil represents a promising and cost-effective alternative, as elephant grass is currently highlighted among the most exploited crops for energy purposes.

Exploring ADMET properties and the anticancer potential mechanism of a new organoselenium compound using network pharmacology and in vitro study

Daniela Mathes — 2025-04-11

Complex genetic mutations and malignant transformations in cancers have plagued the world. Modified variants of nucleoside analogs have proven to be allies in the hope of promising new treatments in anticancer therapy. However, it sometimes faces difficulties related to its low bioavailability and resistance mechanisms. In this study, investigative and initial in silico and in vitro analyses were performed on a new organoselenium compound, 5-Se-(phenyl)-3-(ferulic-amido)-thymidine (AFAT-Se). Different in silico platforms were used to explore the ADMET properties and possible pharmacological and toxicological effects of AFAT-Se, and its anticancer potential was assessed by in vitro studies. AFAT-Se complied with Lipinski's rules, exhibiting favorable pharmacokinetic properties, interaction with common drug metabolic enzymes, toxicities that require further study, and cytotoxicity toward the HT-29 tumor cell line, as evidence of its potential as an antineoplastic agent. Therefore, critical molecular targets were identified in cancer-related pathways; thus, the organoselenium AFAT-Se is a promising candidate for further studies on this pathology.

Size effects in itabirite jigging under high frequency

Assamo Esmael Amad Valy — 2025-04-01

Concentration jigs have been used in ore dressing since the Middle Ages. Contrary to other sorting methods, gravity separation is a unit operation that implies low operational and environmental costs. This work describes the effect of particle size on separation efficiency using synthetic quartz and hematite mixes, simulating itabirite ores. The technological parameters of a Harz-Denver type jig were studied as a rougher stage at bench scale, employing previously sized samples. The experiments were carried out using 12 size classes, under a stroke amplitude of 7.0 mm and various pulse frequencies, including values above those historically practiced in the industry. Hematite content in prepared feeds was 40 %, 50 % and 60 %. It was observed that the jig has better performance with feed contents below 50 % hematite in the case of blends of middle and fine particles. The results were very promising. The concentrate average hematite grade was 89.35 %, from 40 % hematite feed, while the corresponding recovery was 97.62 % and a very high Gaudin’s selectivity index of 12.37. Nevertheless, the jig did not perform so well when it treated global samples (mix of all size classes), indicating the importance of the proper granulometric grading of the ore particles.

Physiographic study of the municipality of Nova Esperança do Sul/RS

Franciele Delevati Ben — 2025-04-08

This work aims to carry out a physiographic compartmentalization of the municipality of Nova Esperança do Sul, southern Brazil. Information derived from the integration of lithologies, soils, and terrain was used as a basis. Lithologies and soils were defined based on existing maps, with supervision and analysis through fieldwork. The relief units were defined through the processing of the Digital Elevation Model by analyzing altitudes and determining the declivity and amplitude of the slopes. The municipality features significant contacts between the volcanic rocks of the Serra Geral Formation and predominantly arenitic sedimentary rocks of the Botucatu, Guará, and Sanga do Cabral Formations, in a terrain characterized by the predominance of Hills and gently undulating Hills that transition into portions of Mounds and Buttes. The soils over the volcanic lithologies consist of the Association of Argisols and Litholic Neosols, over the sedimentary ones, Red Argisols, and along the Jaguari River, Gleysols. Automated mapping cross-referencing has determined 18 classes of physiographic units, with emphasis on the Nova Esperança class, which covers approximately 43.2 km² and is characterized by undulating hills with volcanic rocks in association with Argisols and Neosols. The cartographic database collected in the research can assist in environmental planning and management efforts to be developed in the municipality, correlating land uses with physiographic conditions.

The socio-environmental conflicts generated by uranium mining: experiences in the world in the last decade

Vívian Ariane de Oliveira Costa — 2025-04-01

In the context of the nature imposed by advanced capitalism, there has been an expansion in the exploitation of uranium ore, generating socio-environmental conflicts. The aim of this article is to introduce the reader to the scenario of socio-environmental conflicts caused by the uranium mining sector on a global scale over the last ten years (2013-2023). Based on a systematic literature review to identify and characterize conflicts as distributive, territorial, and/or spatial, a search was carried out in five databases: LILACS; PubMed; SciELO; Scopus and Web of Science. The articles analyzed showed conflicts in 18 different countries, in which the dispute between the different social actors and the violence suffered by the most vulnerable became evident. Against this, environmental justice was suggested as a way of broadening the debate and changing the vision towards building a fair future for all social groups and free from radioactive risks

Computer vision-based wood identification: an approach with LPQ and GLCM descriptors integrated with Ensemble classification

Anna Thaís Costa Lopes — 2025-04-01

Given the recognized relevance of botanical identification for forest management and biodiversity conservation, this paper proposes the identification of plant species wood anatomy using computer vision techniques. Microscopic images of 30 species were sourced from the Forest Species Database and captured using an Olympus CX40 microscope at 100x magnification, ensuring high detail. Pre-processing techniques, including normalization and feature extraction, were applied to enhance texture and color characteristics. Statistical, structural, and spectral descriptors such as LBP_{HF 24,3} and the combination of LPQ and GLCM (GHS) were utilized. These descriptors were analyzed with MATLAB and classified using robust methods, including Ensemble classifiers. Cross-validation ensured reliability, and results achieved assertiveness rates of 96.7% and 99.3% for LBPHF and LPQ-GLCM combinations, respectively. This study demonstrates the effectiveness of automated methods in enhancing botanical identification processes, offering precise and efficient tools for forest management and biodiversity conservation.

Phenology of Butia catarinensis in the Southern Coastal Region of Santa Catarina, Brazil

Iara Zaccaron Zanoni — 2025-04-01

This study evaluated the phenology of Butia catarinensis in shrubby Restinga and under the understory of eucalyptus monoculture (Eucalyptus saligna and Eucalyptus paniculata) along the southern coast of Santa Catarina, Brazil. Phenological data were collected monthly over a one-year period. Butia catarinensis exhibits an annual, asynchronous reproductive cycle, showing higher flowering and fruiting rates in spring and summer, with reduced reproductive activity during winter. Precipitation had minimal influence on its reproductive cycle; however, higher temperatures and increased solar radiation positively correlated with the development of green and ripe fruits year-round. The lack of significant differences between the two study environments indicated that the eucalyptus monoculture microclimate did not affect flowering and fruiting quantities of B. catarinensis, though it may have influenced phenophase timing, potentially accelerating, delaying, or extending these events.

The consumption of ora-pro-nobis and tamarillo improves which health indicators?

Renata de Souza Ferreira — 2025-04-04

Ora-pro-nobis and tamarillo are unconventional food plants (UFP) in Brazil rich in nutrients and fiber, which can exert positive effects on health. The objective was to analyze studies to verify the effectiveness and applicability of these UFPs in clinical practice. The Prisma protocol was used for data search. Four databases (PubMed, Cochrane, Embase, and Web of Science) were searched using compiled terms and Boolean operators “AND” / “OR.” Rayann was used to select the studies. The Joanna Briggs manual was adopted to assess the study's risk of bias. Thus, 17 studies were included in this review. Most studies (14/17) had a low, 2 moderate, and 1 high risk of bias. In conclusion, ora-pro-nobis and tamarillo exert beneficial effects on the lipid profile. Tamarillo improves antioxidant capacity, besides exerting positive effects on lipid and glycemic profiles, memory, and anticarcinogenic action, while ora-pro-nobis acted in gastrointestinal modulation, lipid profile, body weight reduction, satiety increase, and improving rheumatoid arthritis. To improve health indicators, we suggest daily consumption of 100 g of fresh leaves or 10 g of ora-pro-nobis flour; and/or 100 g of tamarillo.

Medicinal potential of tree vegetation for respiratory system treatment in southern Brazil

Vanilde Citadini-Zanette — 2025-04-01

The Southern coal region of Santa Catarina concentrates 10.5% of Brazil's mineral coal reserves, and the ore extraction process has greatly contributed to the environmental degradation of the Urussanga River Basin in this region. At a global level, areas contaminated by coal mining cause public health concerns, owing to illnesses that may be associated with this practice, for example, respiratory diseases. In this context, the present study aimed to identify tree species with medicinal potential to treat respiratory diseases, sampled along the tributaries of the Urussanga River. For this purpose, a bibliographical review was conducted for 119 tree species recorded in the study area through a previous floristic survey. We searched the Scopus, SciELO, Science Direct, and PubMed databases for ethnobotanical and phytochemical studies that addressed the medicinal potential of these species for the respiratory system. Of the 119 species, 12 (10.08%) showed medicinal potential for the respiratory system. Of these, five were recommended for coughs and unspecified diseases affecting the respiratory tract, four for asthma, three for bronchitis, two for pneumonia, and one for laryngitis and acute lung problems. This finding highlights the medicinal potential of tree species native to Brazil present in the Urussanga River Hydrographic Basin region. However, further scientific studies are necessary to evaluate the phytochemical profile and pharmacological activity of these tree species from the Atlantic Forest biome, whose floristic composition has already been notably modified.

Guilleminea densa (Amaranthaceae): a new record for the brazilian flora

Lucas Gonçalves da Cunha — 2025-04-04

This paper presents the first record of Guilleminea densa for Brazil. Until now, the genus Guilleminea was only represented in Brazil by G. fragilis Pedersen, found in Mato Grosso do Sul. Guilleminea densa is native to most of South America and part of North America and has been recorded as invasive in southern Africa. This species can be easily identified by its glabrous leaves on the adaxial face and densely woolly on the abaxial face, with a dense inflorescence of whitish and woolly flowers. The species was recognized during a floristic survey of ruderal species in the municipality of Santa Maria, in the central region of Rio Grande do Sul, Brazil, where it was found in an urbanized environment. The paper provides descriptions, illustrations, and information on habitat, distribution, and taxonomy.

Prediction of corn genetic bases grain productivity by phenological and meteorological variables

Murilo Vieira Loro — 2025-03-14

The objective of this study was to determine if it is possible to predict the grain yield of maize genotypes using phenological and meteorological variables. An experiment was conducted with maize genotypes at five sowing dates. On the first sowing date (September 21, 2021) 71 genotypes were sown (46 single hybrids, 14 triple hybrids, 3 double hybrids and 8 varieties). In the other four sowing dates (October 20, 2021, November 20, 2021, December 20, 2021 and January 30, 2022) 78 genotypes were sown (47 single hybrids, 15 triple hybrids, 8 double hybrids and 8 varieties). For each genotype and sowing date, the phenological variables, grain yield, accumulated global solar radiation and the thermal sum in the vegetative and reproductive stages were obtained. For each maize genetic base, principal component analysis was applied and the parameters of the regression tree algorithm for predicting grain yield as a function of phenological and meteorological variables were estimated. The global solar radiation accumulated in the vegetative and reproductive stages is the main variable that determines the grain yield of triple and double hybrids; and simple hybrids and maize varieties, respectively.

Making chocolate sweets and the statistical analysis of experimental data

Joyce Laura da Silva Gonçalves — 2024-04-26

This is a didactic proposal for the introduction of data processing concepts using typical Brazilian chocolate sweets, called brigadeiros. The methodology consisted of distributing a packaging of brigadeiro to each of the groups: blue, orange and green. The groups had to make the brigadeiros in the dimensions they wanted, proceeding with their quantification and weighing. Statistical analysis was based on hypothesis tests (p<0.05) in which the average mass of sweets obtained by the groups was compared in relation to the reference value and the performance of the groups among themselves. It was observed that 29, 20 and 16 sweets were made with average masses of 16.4±2.2; 24.6±4.5 and 28.5±8.7g for the blue, orange and green groups, respectively. The groups' precision and accuracy were blue>orange>green. The unpaired t-test, confidence interval for the mean and ANOVA suggested a significant difference between all groups. However, Tukey's test identified only the brigadeiros in the blue group as different from the other groups. In addition to the insertion of statistical concepts, carrying out this didactic proposal can stimulate teaching practice, involving the student and promoting meaningful learning. This experiment is fast, practical and inexpensive, and can be applied at any level and/or area of knowledge.

Genetic diversity of Trifolium polymorphum Poir. (Fabaceae) in natural populations of Rio Grande do Sul, Brazil

Letícia Cezar Kraetzig — 2025-04-01

The genus Trifolium (Fabaceae) is composed of herbaceous plants of forage interest that contribute to the maintenance of the productive capacity of soils, enabling the fixation of atmospheric nitrogen. Genetic diversity is an important factor for the response of populations to environmental changes. The present work aimed at analyzing the genetic diversity and population structure of Trifolium polymorphum Poir., a native species of the Pampa biome, using ISSR (Inter Simple Sequence Repeat) molecular markers. Leaves and stolons from five populations were collected in São Borja, São Gabriel, Tupanciretã, Eldorado do Sul, and São Pedro do Sul and stored in silica gel until DNA extraction. The DNA was extracted and quantified in 1% agarose gel. Regions were amplified via ISSR-PCR with four primers: (GA)8 YC, (AG)8 T, (GACAC)3, and (AG)8 TA. The data were analyzed using statistical software GenAlEx 6.5, Structure, and Structure Harvester. The results showed greater genetic variation within populations (56%) than between populations (44%). Cluster analysis and the scatter plot from the main coordinate analysis separated the accessions according to geographical origin. However, the mean genetic diversity (H=0.113) for all primers was low when compared to other studies with the same genus and marker. This diversity information can be used to adopt measures that favor the best forms of conservation and management for the sustainable use of the biodiversity of native species.