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Dicalcogenetos de metais de transição em poucas camadas: o papel das espécies de calcogênio e suas propriedades não convencionais
(Universidade Federal de São Carlos, 2024-06-10) Bracht, Jean Michel; Lima, Matheus Paes; https://lattes.cnpq.br/1835846543912999; https://lattes.cnpq.br/0545565137193585
Two-dimensional (2D) Transition Metal Dichalcogenides (TMDs) constitute the most studied class of 2D materials after graphene, as they have a variety of applications already demonstrated in the laboratory, including sensors, nanoelectronics and catalysis. In this context, simulations based on Density Functional Theory (DFT) allow exploring different compositions and crystalline phases, searching for the most promising ones for specific applications. This doctoral thesis presents a systematic investigation of few-layer 2D TMDs with compositions MQ2, where M belongs to the groups 8 and 10 of the periodic table and Q=S, Se or Te. We investigate systems that vary between one and six in the number of layers. Our study focuses on elucidating the structural, energetic and electronic properties of these materials through DFT-based numerical simulations. The structures are optimized with the GGA-PBE semi-local exchange-correlation functional, where we included the D3 van de Waals correction on the forces and total energy. Furthermore, we incorporate corrections for the self-interaction error inherent in PBE through the HSE06 hybrid functional and spin-orbit coupling. Our investigation reveals significant variations in lattice parameters and exfoliation energies with changes in the number of layers, mostly influenced by chalcogen species. Compositions with transition metals within the same column of the periodic table exhibit similar lattice parameters for the same choice of chalcogens, making them suitable for constructing commensurable heterostructures. Furthermore, the decreasing electronegativity trend from S to Te results in stronger exfoliation energies due to lower surface charges, thus governing the structural and electronic characteristics of these materials. We delved deeper into the electronic properties, and found unusual features in other materials, such as (i) increases in band gap generated by spin-orbit coupling for certain compositions, (ii) emergence of polarization electric fields due to the breaking of point inversion symmetry, and (iii) semiconductor-to-metal transitions with the addition of just one or two sheets to the monolayer. The presence of sulfur on the surface results in greater variations in the work function (in relation to the Se and Te terminations) when the number of layers varies, allowing precise adjustment of the work function and electronic affinity with the number of layers and with the choice of transition metal species. These findings highlight the unique and versatile nature of TMDs from groups 8 and 10, motivating diverse applications in nanoelectronics and catalysis, where tuning properties with the number of layers can be leveraged for technological advances.
Desigualdade educacional e cultura digital no ensino remoto durante o isolamento social: percepções de discentes do ensino médio da região do Bico do Papagaio-TO (2020-2021)
(Universidade Federal de São Carlos, 2024-06-10) Rosa, Cristiane de Oliveira; Mill, Daniel Ribeiro Silva; https://lattes.cnpq.br/1515286597269486; https://orcid.org/0000-0002-8336-3645; https://lattes.cnpq.br/5823180213462937; https://orcid.org/0000-0001-6426-7685
The general objective of the work is to identify and analyze the perceptions of public high school students about the consequences of remote teaching during the Covid-19 pandemic in the Bico do Papagaio region, Tocantins, focusing on educational and social inequalities. The specific objectives are: to verify the relationship between remote teaching and students' living conditions; raise public educational policies adopted during the pandemic; and analyze changes in performance indicators (Ideb and Enem) in Tocantinópolis, Palmeiras do Tocantins and Nazaré, with an emphasis on students' perceptions of educational inequality and integration of digital culture during the period of social isolation. The research, supported by the Coordination for the Improvement of Higher Education Personnel (Capes), uses a qualitative-quantitative methodology to explore the experiences and perceptions of students from selected schools, addressing nuances related to access to education and technology in a context of health emergency global. The dissertation contextualizes the educational scenario in the North region, marked by socioeconomic disparities and limited access to digital resources, revealing how the pandemic exacerbated pre-existing inequalities. The study analyzes the historical and social context of the Bico do Papagaio region, considering the educational policies of the state of Tocantins and the implementation of remote teaching. Using questionnaires as a data collection instrument, the research seeks to capture students' perceptions of the inequalities generated or intensified by remote teaching, including issues of access to technology, quality of internet connection and adequacy of pedagogical content to the new educational reality. The conclusions of the dissertation highlight the urgency of more effective public policies, capable of addressing both educational inequalities and the challenge of promoting an inclusive integration of digital culture in teaching. The research investigates the impact of remote teaching in high school in vulnerable areas, aiming to improve pedagogical practices to promote equity and digital inclusion. The findings suggest the need for future research on the long-term impact of remote learning, access and use of technology in education, educators' perceptions, public policy analyses, and educational infrastructure, emphasizing the importance of investigating these aspects to improve education during crises.
Agrobiodiversidade e soberania alimentar na Floresta Nacional do Rio Purus, Amazônia: contribuições do Santo Daime e de práticas agroecológicas
(Universidade Federal de São Carlos, 2024-06-10) Paula, Juliana Carla Silva; Nunes, Nina Lys de Abreu; https://lattes.cnpq.br/1407947268657576; Norder, Luiz Antonio Cabello; https://lattes.cnpq.br/008035370998007; https://lattes.cnpq.br/9607193278579474
For millennia, Amazonian people have managed forest resources. This relationship between culture and nature is important for the maintenance of Amazonian agroecosystems. The landscapes of this region are characterized by diversity and long coexistence with human beings. In the Amazon today, people live with total or partial dependence on forest resources for their well-being and with in-depth local knowledge. Among the variety of cultural practices that exist within the forest, Santo Daime emerges, a religious movement that emerged in the Amazon in 1930, resulting from the experience of Raimundo Irineu Serra, a migrant from Maranhão who works in the rubber cycle in the State of Acre. The objective of this research is to investigate how religious identity influences the lifestyle of these people, having similarities with the principle of Agroecology and a high maintenance of Agrobiodiversity that results in the strengthening of Food Sovereignty. We used oral history, participant observation and MESMIS (Marco para la Evaluación de Sistemas de Manejo de Recursos Naturales) as methodology, incorporating Sustainability Indicators). The study area was in the Purus River National Forest (FLONA Purus) and region, located in the State of Amazonas, municipality of Pauini, in four different communities. All of them culturally linked by the religion of Santo Daime, a religion that uses the drink ayahuasca during its rituals, which is prepared from two Amazonian plants. The results are presented through four main axes, namely: 1) the interconnection between the Santo Daime culture and its link with agroecology; 2) the survey of Agrobiodiversity in practice, 3) the trajectory followed by Cooperar; the Agroecology and Food Sovereignty nucleus of Mapiá and middle Purus; and 4) the analysis of sustainability indicators. We observed the familiarity between the practices of Santo Daime followers and agroecological principles, we inferred a high maintenance of Agrobiodiversity, supporting the maintenance of Food Sovereignty. With a survey of 118 agrobiodiversity spec ies, for food, nutritional or medicinal purposes. The results obtained through sustainability indicators reveal a mixed situation regarding the sustainability of the agroecosystems studied. With regard to environmental indicators, it is observed that a significant part of the parameters are classified as good, in the economic sphere, the results less than 50% are good, with regard to social indicators, the results indicate important challenges, with less 50% of the parameters being good and 33% being a bad parameter. In this way, we can conclude that religious identity is driving a motivation to seek food sovereignty and maintains a high level of agrobiodiversity, however, according to sustainability indicators, challenges will have to be achieved to remain this way.