Principais Coleções do Repositório
Submissões Recentes
Fibrocimento com resíduos lignocelulósicos encapsulado com copolímero etileno acetato de vinila (EVA)
(Universidade Federal de Lavras, 2025-09-12) Nunes, Glauco Fernandes de Oliveira; Mendes, Lourival Marin; Guimarães Junior, José Benedito; Mendes, Lourival Marin; Guimarães Junior, José Benedito; Batista, Felipe Gomes
The study investigated the development of fiber,reinforced cement composites produced by extrusion, reinforced with lignocellulosic residues from the species Erythrina poeppigiana (cellulose particles and nanofibrils) and incorporating pulping residues (dregs), with subsequent encapsulation by ethylene,vinyl acetate copolymer (EVA). The objective was to evaluate the physical, mechanical, and microstructural performance of these composites, aiming to increase their durability against weathering and the alkalinity of the cementitious matrix. Properties such as bulk density, porosity, water absorption, modulus of rupture, modulus of elasticity, proportional limit, toughness, and microstructure were analyzed using scanning electron microscopy. The results showed that encapsulation with EVA reduced water absorption by up to 36%, maintained porosity below 28%, and favored the cohesion of the matrix,reinforcement interface. The composite containing nanofibrils and dregs stood out, presenting a modulus of rupture of 8.7 MPa, a modulus of elasticity greater than 4.9 GPa, and an average toughness of 1.08 kJ/m². It is concluded that the use of lignocellulosic waste from Erythrina poeppigiana, associated with encapsulation with EVA, represents a promising strategy for the production of sustainable cementitious materials, contributing to the valorization of residual biomass and to the principles of the circular economy.
Efeito da conversão de campos nativos por pastagens exóticas e o uso de ivermectina na relação entre ácaros Macrochelidae (Acari: Mesostigmata) e Dichotomius bos (Coleoptera: Scarabaeidae)
(Universidade Federal de Lavras, 2024-09-27) Lyra, Raphael Rodrigues; Louzada, Júlio Neil Cassa; Passamani, Marcelo; Correa, César Murilo de Albuquerque
The Cerrado biome harbors high biodiversity and plays a fundamental role in maintaining ecological processes and providing ecosystem services. However, the conversion of natural areas into agro-pastoral systems and the adoption of intensive management practices have promoted significant changes in the structure and functioning of these environments, particularly affecting edaphic biota and soil-associated ecological interactions. Among the organisms potentially impacted by these changes are dung beetles of the subfamily Scarabaeinae and phoretic mites of the family Macrochelidae, functionally interdependent groups that are important for the dynamics of bovine dung. This dissertation aimed to evaluate the effects of the conversion of native pastures into exotic pastures and the use of ivermectin in livestock management on population metrics and phoretic relationships between the dung beetle Dichotomius bos (Coleoptera: Scarabaeidae) and associated Macrochelidae mites in cattle ranching areas in the region of Carrancas, Minas Gerais, Brazil. To this end, beetles were collected in areas with different pasture types and histories of ivermectin use, followed by the quantification and identification of phoretic mites associated with the sampled individuals. A total of 8,776 mites associated with 288 individuals of Dichotomius bos were collected, belonging to eight Macrochelidae species. The results indicated that ivermectin use was associated with a reduction in the abundance of the phoretic mite community, whereas the conversion of native pastures into exotic pastures did not result in significant differences in the evaluated metrics. Species richness remained constant among the different management types, possibly due to the approach focusing on a single host species. Overall, the results demonstrate that livestock management practices can influence the structure of edaphic communities and the ecological interactions associated with bovine dung. Thus, this study contributes to a better understanding of the effects of anthropization on Cerrado edaphic biodiversity and reinforces the importance of considering interspecific interactions in ecological assessments of pastoral systems.
Bacillus amyloliquefaciens CN 307 e sua formulação comercial na quimiotaxia de Meloidogyne incognita
(Universidade Federal de Lavras, 2025-12-12) Caetano, Pâmella de Sá; Terra, Willian César; Cavalcanti, Vytória Piscitelli; Alves, Eduardo; Siqueira, Carolina da Silva; Teixeira, Lívia Pimenta
The root-knot nematode, Meloidogyne incognita, causes significant damage to agriculture worldwide. Experiments were conducted in a greenhouse and at the Nematology Laboratory of the Federal University of Lavras, Minas Gerais, Brazil. Treatments consisted of applying the commercial product Auba® or the isolate B. amyloliquefaciens CN 307 to seeds of soybean (Glycine max L.), cv. M 6410 IPRO, common bean (Phaseolus vulgaris L.), cv. 2051, and corn (Zea mays L.), hybrid P 3707VYH C1. Chemotaxis assays showed that treated root exudates and roots exhibited a repellent effect on J2 nematodes, a result also observed when only the product or the isolate was tested. Biofilm formation occurred only in bean roots treated with the product. In beans, the commercial product and the isolate reduced the number of galls per gram of root by 31.24% and 42.96%, respectively, and the number of eggs per gram of root by 55.32% and 40%. In the second experiment, there was no significant reduction in the number of galls, but there were reductions in the number of eggs per gram of root of 59.78% with the product and 32.14% with the isolate. In soybeans, in the first experiment, there was no significant reduction in the number of galls per gram of root; however, the number of eggs was reduced by 64.18% with the product and 38.31% with the isolate. In the second experiment, the reductions in the number of galls per gram of root were 38.33% with the product and 27.80% with the isolate, with no significant effect on the number of eggs. Microscopic analysis with Raman spectroscopy indicated, in the treated roots, peaks associated with cellulose, xylan, and lignin, with a predominance of cellulose in beans and lignin in soybeans. The results indicate that the product and the isolate have potential for the biological management of M. incognita, acting through direct effects and biochemical alterations in root tissues.
Modelos de regressão para dados de áreas com valores extremos no estudo da incidência de dengue em Minas Gerais
(Universidade Federal de Lavras, 2025-09-30) Damaceno, Gean Pereira.; Scalon, João Domingos; Silva, Douglas Mateus da; Lima, Renato Ribeiro de; Manzato, Lourenço; Oliveira, Deive Círio de
Dengue fever has become a growing threat in recent years, with frequent outbreaks and overwhelming healthcare systems. The spread of the virus, transmitted by Aedes aegypti, is strongly related to environmental and urban factors, making the use of statistical methods essential to understand its dissemination and implement more effective actions to combat it. Traditional linear regression models, although widely used, assume the independence of observations and do not consider spatial autocorrelation, which, when present, can compromise the accuracy of estimates in geographically interdependent areas. To overcome this limitation, spatial models such as Simultaneous Autoregressive Regression (SAR) and Conditional Autoregressive Regression (CAR) have emerged as solutions. These models are able to capture spatial patterns that are normally present in area data. However, these models are sensitive to outliers, which generally impair the quality of the analyses. Geographically Weighted Regression (GWR), which incorporates spatial variation through local estimation of coefficients, has been proposed as an alternative but can also be influenced by outliers. Robust Geographically Weighted Regression (RGWR) has been proposed as an improved solution that can provide greater robustness against outliers and, consequently, lead to more effective estimates. This study applies RGWR to investigate the incidence of dengue fever in the state of Minas Gerais, in the year of 2023, aiming to improve the accuracy of estimates in the face of outliers, which are very common in this type of data. The variables used in the study were: dengue fever incidence as the dependent variable and adequate sanitation, urbanized area, street urbanization, and street tree planting as independent variables. The results showed that RGWR can provide a more accurate approach to understanding the spatial distribution of dengue in data from areas with outliers which can contribute to more efficient and effective management of public health actions.
Para além dos fantasmas: o rapto de Paulo e os limites do conhecimento humano na Suma Teológica de Tomás de Aquino
(Universidade Federal de Lavras, 2025-10-27) Botelho, Lincoln Antônio Corrêa; Lima, Arthur Klik de; Oliveira, Carlos Eduardo de; Souza, Meline Costa
Thomas Aquinas maintains that it is impossible for the human intellect, in the state of the present life, to understand actually without turning to phantasms. This thesis, which marks the necessity of the convertio ad phantasmata in intellectual operations in via, is stated and defended in the Prima Pars of the Summa Theologiae and has important consequences for the limitations of human knowledge in Aquinas’s philosophy. Indeed, if every act of understanding takes place by reference to phantasms derived from sensible experience, then even our knowledge of what is purely intelligible or spiritual can occur only in the same way. With respect to immaterial and purely intelligible realities, we can attain only a kind of knowledge that has its roots in material and sensible things and that always refers back to them through the convertio ad phantasmata. It follows, therefore, that such knowledge will always be imperfect, mediated, and relatively inadequate when compared to what these invisible realities truly are in themselves. The thesis of the necessity of the convertio, therefore, establishes limits to our knowledge of purely spiritual realities, and these limits are repeatedly affirmed by Aquinas throughout his entire work. Despite this, Paul was able to state in his Letter to the Corinthians that he had seen the “third heaven,” which the tradition understands—and Aquinas likewise in the Secunda Secundae—as meaning that the Apostle had an essential vision of God. Like Moses, Paul was raptured to the vision of the divine essence, which, however, cannot occur through any mediation whatsoever, phantasms included. The aim of the present study is to understand how Aquinas explains Paul’s rapture, that is, a direct vision of the essence of God, in light of the necessity that the intellect has, in the state of the present life, to understand by turning to phantasms. To this end, (i) we present the thesis of the necessity of the convertio, deepening its foundations and consequences; (ii) we present the principal articles of the question concerning spiritual rapture; and (iii) finally, we seek to relate them.