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Hidroxipropilação de amido e fibras de resíduo de açaí para obtenção de biocompósitos
(Universidade Federal de São Carlos, 2025-03-26) Lopes, Henrique Solowej Medeiros; Komatsu, Daniel; https://lattes.cnpq.br/2620060426867863; Dufresne, Alain; http://lattes.cnpq.br/2836712749450886; Menezes, Aparecido Junior de; https://lattes.cnpq.br/0484426340349483; https://lattes.cnpq.br/5006391678583766; https://orcid.org/0000-0002-8222-0888
Within the context of materials engineering, starch stands out as a sustainable source for the production of biofilms, due to its biodegradability and its renewable source of high produc-tion in several different climates and regions. However, pure starch materials have insuffi-cient properties for their wide application in industry and commerce, and hydroxypropyla-tion is a sustainable way to reduce the hydrophilic and fragile character of the material. In this study, cassava starch and açaí residue were chemically modified by hydroxypropylation. The combination of parameters for sample preparation was performed by a design of exper-iments 2³ full factorial. The substrates were previously activated with KOH in water and ethanol solution, modified in different molar ratios (0.4, 0.6 and 0.8 OHPO/OHglucose), tem-peratures (115, 125 and 135 °C) and açaí residue proportions (0, 5 and 10 wt%). The effects of each defined parameter were evaluated by analysis of variance (ANOVA), revealing that the molar ratio and the higher amount of açaí residue significantly increased the mass gain, while the temperature had the opposite effect. The structural characterization by FTIR and solid-state NMR confirmed the chemical modification through the identification of methyl bond peaks, with quantification of the degree of substitution by elemental analysis and sol-id-state NMR, varying between 0.1 and 0.4, as the molar ratio increases and the temperature decreases. Notably, complete gelatinization of starch was observed during the reaction, evi-denced by the absence of crystalline structures in XRD and SEM. However, homopolymeri-zation of propylene oxide (PPO) has been observed, resulting in the intermolecular presence of PPO in the polymer chains, significantly increasing the plasticization of the material. This plasticization can be observed by TG and DSC, which indicate a reduction in thermal stability, in addition to accelerated retrogradation with the formation of short- and long-range crystalline structures via XRD and FTIR, especially in samples containing açaí resi-due. Due to the previous plasticization of starch, films were obtained via casting at room temperature with significant lower amount of glycerol (7.5% starch weigh basis), resulting in materials with 470% high elongation at break, although with lower maximum tensile strength stress, greater hydrophilicity and tendency to retrogradation. The results demon-strate the potential of chemical modification of starch to expand its applications in sustaina-ble packaging, due to the success in the low use of synthetic plasticizers achieved.
Cerâmicas bioinspiradas recobertas com óxidos perovskíticos para aplicação em catálise por plasma de micro-ondas
(Universidade Federal de São Carlos, 2025-03-26) Cardoso, André Lair Ferreira; Muche, Dereck Nills Ferreira; https://lattes.cnpq.br/6542991023278848; Gunnewiek, Rodolfo Foster Klein; https://lattes.cnpq.br/5185829124608696; https://lattes.cnpq.br/2136511592356799; https://orcid.org/0000-0002-0658-5818
Climate changes related to global warming are directly associated with greenhouse gases emissions, mostly originated from fossil fuels. To help mitigate these gases emissions, the viability of advanced catalytic techniques, such as microwave plasma catalysis, are evaluated. This thesis aims to produce a bioinspired ceramic by microwave sintering to be used as support for catalytic particles for microwave plasma catalysis. The support was produced by conventional and microwave sintering, achieving a 35% reduction in energy consumption when sintered by the microwave technique. The catalytic ceramics, BaTiO3, SrTiO3, Ba0,5Sr0,5TO3 and MgTiO3, were synthesized by the conventional or microwave assisted Pechini method, followed by analysis of the resulting powder using X-ray diffraction, scanning and transmission electron microscopy, and diffuse reflectance spectroscopy. The particle deposition over the bioinspired support was carried out, investigating their microwave plasma resistance. It was noted that the particles protected the support from plasma ablation and sputtering. The plasma resistance under Argon or Nitrogen microwave plasmas of the bulk titanate ceramics were also investigated, evaluating their microstructural stability, densification and modification of electrical and dielectric properties regarding the sintering technique and type of plasma treatment. The SrTiO3 composition presented the best plasma resistance, while others were also resistant to plasma ablation and sputtering. All compositions presented high values of dielectric constant, foreseeing a decent application as catalytic materials in microwave plasma catalysis.
Avaliação da eficácia do óleo essencial de Melaleuca encapsulado em pectina cítrica no controle in vitro de Leucoagaricus gongylophorus
(Universidade Federal de São Carlos, 2025-03-26) Moreira, Bruno Ricardo; Forim, Moacir Rossi; https://lattes.cnpq.br/1234565160573730; https://lattes.cnpq.br/5084844653825682
Leaf-cutting ants of the genera Atta and Acromyrmex are widely found in Brazil. These social insects collect plant material to use as a substrate for the symbiotic cultivation of the fungus Leucoagaricus gongylophorus, with which they maintain a mutualistic relationship. However, this foraging activity causes damage to human activities related to forestry, grazing, and agriculture. The control of these ants is generally carried out using chemical agents, which may have harmful effects on the environment and human health. An alternative approach involves the use of plant secondary metabolites to control these populations. However, such compounds are often unstable and difficult to control in terms of release. To address these issues, an encapsulation process using biopolymers has been explored. The main objective of this study was to develop a formulation aimed at controlling leaf-cutting ants. The approach was based on the use of essential oil from Melaleuca alternifolia, also known as tea tree. This essential oil is widely used in hygiene products and as a herbal remedy for skin conditions, among other uses, and has proven effectiveness in microbial control. The first part of the study consisted of biological assays to evaluate the activity of the essential oil on the growth of the symbiotic fungus at various concentrations. Complete inhibition was observed at concentrations above 15 microliters. Based on a literature review on biopolymers, citrus pectin was selected as the encapsulating agent. To develop the formulation method, several experiments were conducted with variations in process parameters, aiming to maximize encapsulation yield. This yield was quantified using gas chromatography coupled with mass spectrometry, employing the headspace technique. A formulation with approximately 84% yield was obtained. Using this formulation, a biological assay was carried out to evaluate its effect on the growth of L. gongylophorus, resulting in 80% fungal growth inhibition. These results indicate that the developed formulation may serve as an ecological and effective alternative to conventional compounds for the control of leaf-cutting ants.
A influência do ambiente escolar e do letramento em cultura africana na crença de autoeficácia docente para o ensino dos objetos de conhecimento de matriz africana nas aulas de educação física
(Universidade Federal de São Carlos, 2025-03-26) Alvares, Luis Eduardo; Godoi Jacomassi, Daniela; https://lattes.cnpq.br/7699007812483790; https://lattes.cnpq.br/2715455816295604
Despite the mandatory teaching of African culture according to Law 10.639/03, its presence in Brazilian schools is still limited and faces several challenges, such as prejudice and stereotypes, isolated practices on specific dates to meet protocols, and teachers' insufficient undergraduate education on this topic. In this context, it becomes relevant to investigate teachers' self-efficacy beliefs regarding the teaching of these contents. Teacher self-efficacy is defined as the judgment that teachers make about their ability to establish teaching strategies, create effective learning environments, and engage students even in the face of difficulties. Thus, teachers' confidence in their ability to teach African culture can directly influence their practices with this content in the school routine. This study aimed to investigate the relationship between teachers' perceptions of the influence of the school environment, their literacy in African culture, and their self-efficacy beliefs to teach this content in physical education classes. The study was exploratory and used a quali-quantitative approach. A questionnaire with a 0-10 scale was applied to assess teachers' perceptions of the influence of the school environment, literacy in African culture, and self-efficacy beliefs. For the study, the essential knowledge required for teaching African culture in physical education classes was defined, taking into account the legal framework, curriculum guidelines, and official documents in Brazilian education. Based on this knowledge, the specific domains for teaching African culture were identified, analyzing the diversity of content and knowledge dimensions (conceptual, procedural, and attitudinal). The results indicated that, although teachers reported a high perception of self-efficacy in topics such as combating racism and African-based games and play, this perception did not extend to topics such as African history and culture, African martial arts, and dances. Additionally, the findings showed that the higher the perception of literacy, the more favorable the school environment was perceived to be for teaching African culture, and the greater the self-efficacy in teaching this content. It was also found that internal factors related to personal moral agency tend to be more effective motivators than external regulators such as laws, curriculum guidelines, and official documents. Based on the results, the study highlights the need for racial and cultural literacy in teacher education to promote a more meaningful approach to this theme within the school curriculum, thereby enhancing self-efficacy beliefs for teaching this content in physical education classes.