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Computational tool to evaluate the efficency of hydrogen in internal combustion engines
(Universidade Federal de Lavras, 2025-03-20) Rincon, Alvaro Ferney Algarra; Alvarez, Carlos Eduardo Castilla; Ensinas, Adriano Viana; Rodriguez, Christian Jeremi Coronado
Behavioral studies on the efficiency of a hydrogen engine are important, as they are part of a global initiative to decarbonize the automotive sector, and this technological route for the use of hydrogen is promising within recent energy transition studies. In this sense, the exploration of new technological development routes around production, commercialization and use of hydrogen for the state of Minas Gerais and for Brazil has been proposed through various government initiatives in recent years. For this reason, this work has developed a computational tool based on a zero-dimensional mathematical model capable of predicting the efficiency of a spark ignition engine when using hydrogen as fuel. The simplicity of the model offers a quick view of the operation and thermodynamics of the engine, which reduces computational effort and produces results that represent the real behavior of hydrogen combustion. This focus helps in the study of combustion and in making decisions about the economic viability of using hydrogen in internal combustion engines. To do this, the compression, combustion and expansion processes in the Otto cycle were mathematically modeled to represent the combustion behavior of the air-hydrogen blend inside the engine cylinder, using code written in MATLAB. The mathematical model was validated with experimental data taken from the research engine bench and those reported in the literature in relation to the pressure curve for the different engines and operating conditions evaluated, and the efficiency produced by the engine under these conditions was estimated. A graphical interface was generated in AppDesigner for the computational tool, making it easier for the user to develop the behavioral and operational study of a hydrogen engine. The results obtained with the computational tool show that the estimated pressure and efficiency values are in good agreement with those found in the literature in all the cases evaluated. The maximum error when comparing the pressure curve was 1.32% for an engine with a speed of 3300 RPM. In addition, the minimum fit of the mathematical model to the experimental data was 86%, which represents a good alternative for estimating the thermal efficiency value.
hCG não é uma alternativa à eCG no protocolo de iatf em vacas bos indicus mas aumenta a eficiência dos protocolos de iatf em vacas que não apresentam estro
(Universidade Federal de Lavras, 2025-05-23) Vicente, Matheus Pedroso; Sales, José Nélio de Sousa; Gasperin, Bernardo Garziera; Mello, Marco Roberto Bourg de
The objective of this study was to evaluate the use of hCG at different times in the TAI protocol on the fertility of lactating Bos indicus cows. In experiments 1 and 2, the cows received an intravaginal progesterone (P4) device and 2 mg of estradiol benzoate (EB) on day zero (D0). In experiment 1, the device was removed after eight and a half days (D8.5; study A) or at seven days (D7; study B). At that moment of the P4 device removal, 500 µg of sodium cloprostenol (PGF2α) and 1 mg of an ovulation inducer (EB in study A and EC in study B) were administered. After the removal of the device, in study A, the cows in the control groups (n=320) did not receive additional treatment, while those in the eCG (n=316) and hCG (n=321) groups received 300 IU of eCG and 150 IU of hCG, respectively. Similarly, in study B, the cows in the control (n=146), eCG (n=151), and hCG (n=151) groups received the same aforementioned treatments. Artificial insemination occurred 36 hours after the removal of the P4 device in study A and 48 hours in study B. Ultrasonographic exams were performed on day zero (D0), on the day of the removal of the P4 device, and at insemination. Experiment 2 was subdivided into three studies (A, B, and C). In study A, cows in the control group (n=42) did not receive additional treatment, while the GnRH (n=44) and hCG (n=41) groups received 100 µg of gonadorelin and 1000 IU of hCG, respectively. Ultrasonographic examinations were performed on D0, D8, D10, D11, D12, and D22. In study B, the cows received the same treatments as in study A (Control; n=228, GnRH; n=227, and hCG; n=229). In study C, 500 IU of hCG were administered to the hCG500 group (n=162), 800 IU to the hCG800 group (n=165), and 1000 IU to the hCG1000 group (n=168). In studies A and B of experiment 1, a greater (P>0.05) follicular growth rate was observed in the eCG (P=0.003) and hCG (P=0.001) groups. The cows in the hCG group had greater rates of anticipated ovulation (P=0.001) and estrus expression (P=0.006). However, a lower pregnancy rate was observed in the cows of the hCG group (P=0.01) and the Control group (P=0.04). In experiment 2, cows treated with hCG showed greater ovulation rates (P=0.03; study A) and P/AI rates (P=0.04; studies B). In study C, the hCG1000 group achieved the greater pregnancy rates (P=0.05). It is concluded that hCG is not an alternative to eCG in the removal of the P4 device. However, the administration of 1000 IU of hCG at the time of insemination increases the fertility of Bos indicus cows that did not show estrus.
Características estruturais de galhas induzidas por Meloidogyne incognita em plantas de tomate e alface
(Universidade Federal de Lavras, 2026-02-25) Campos, Thaiani Maria; Magalhães, Thiago Alves; Vilela, Roberta Mendes Isaac Ferreira; Silva, Orivaldo Benedito da
Vegetables are essential for both food supply and the economy in Brazil. Among the main challenges in horticultural production are root-knot nematodes of the genus Meloidogyne, which impair the root system, reduce productivity, and affect the commercial quality of crops. Among the most widely cultivated vegetables, lettuce (Lactuca sativa L.) and tomato (Solanum lycopersicum L.) stand out, presenting a wide diversity of cultivars with different levels of susceptibility or resistance to nematodes. Root-knot nematodes induce morphological, anatomical, and physiological changes in the roots, resulting in the formation of galls associated with the differentiation of giant cells, disorganization of vascular tissues, and high metabolic demand. In this context, the present study aims to understand the morphological, anatomical, and cellular development of resistant and susceptible cultivars of lettuce and tomato infected by Meloidogyne incognita, evaluating the degree of root infestation as well as the morphological and anatomical changes induced by galls, in order to contribute to the improvement of agricultural practices and the sustainable management of crops. Susceptibility to infection, observed in the lettuce cultivar Regina and the tomato cultivar Santa Clara, was evidenced by reduced development of both the aerial parts and the root system. In contrast, the resistant cultivars, lettuce Mimosa and tomato COMPACK, maintained satisfactory growth and productive capacity even after pathogen inoculation. Gall formation occurred as a result of hyperplasia and hypertrophy processes, associated with the establishment of giant cells, leading to disorganization of the vascular cylinder. The results demonstrate that the genetic resistance present in the Mimosa and COMPACK cultivars, although it does not prevent initial infection, is effective in restricting nematode development. Thus, despite structural alterations in root tissues, the reduced number of galls does not compromise plant development.
Condicionamento com peróxido de hidrogênio em sementes de Corymbia citriodora
(Universidade Federal de Lavras, 2026-02-04) Bento, Paulo Félix; José, Anderson Cleiton; Faria, José Marcio Rocha; Nery, Marcela Carlota; Pereira, Wilson Vicente Souza
Corymbia citriodora is a species of great importance to the Brazilian forestry sector, commonly cultivated across different soils and regions, even those with low nutrients and water resources. However, abiotic stresses such as salinity represent a growing threat to its germination, establishment, and productivity. Therefore, the present study investigated the potential of hydrogen peroxide (H₂O₂) as an osmotic priming agent to improve germination rates, seedling characteristics, and salinity tolerance in C. citriodora. The experiment was conducted under controlled conditions using a completely randomized design in a factorial scheme, with five replicates of twenty seeds. Seeds were pre-treated with H₂O₂ (0, 100, 200, and 400 mM). Seedlings were grown for 14 days under control conditions (0) and germinated under stress induced by sodium chloride (NaCl) (0, 75, and 150 mM). Salt stress significantly inhibited (P < 0.05) the germination percentage, seed vigor index, root length, and chlorophyll content. Conversely, pre-treated seeds showed significant improvement (P < 0.05) in germination speed, seed vigor indices, root length, and anthocyanin content. Given the uniform germinative response among H₂O₂ doses, the 100 mM dose and hydropriming (to isolate the H₂O₂ effect) were selected for the biochemical study under a factorial scheme (2 priming agents × 4 soaking times + control). Neither priming treatment was able to induce over-expression of antioxidant enzymes (SOD, CAT, APX) or decrease lipid peroxidation (MDA). On the other hand, the priming agents were efficient in reducing endogenous H₂O₂ levels, indicating that the protective effect stems from a fine-tuning of the redox state
Ecologia de formigas subterrâneas em um carste neotropical: estratificação vertical, uso do solo e influência climática
(Universidade Federal de Lavras, 2026-02-12) Alves, Dara Veiga; Ferreira, Rodrigo Lopes; Carvalho, Icaro Wilker Gonzaga de; Van den Berg, Eduardo; Prado, Lívia Pires do
Subterranean environments represent one of the least understood compartments of terrestrial biodiversity, particularly regarding ant ecology. Although ants have been extensively studied in epigeic habitats, the diversity, community organization, and environmental responses of ants in the subsurface remain poorly explored. This dissertation aimed to investigate ecological patterns of subterranean ant communities in a neotropical karst landscape, integrating methodological and ecological approaches to understand their vertical distribution in the soil and the influence of edaphic and climatic factors on assemblage richness and composition. In the first chapter, we evaluated community responses to edaphic gradients, exploring vertical stratification along the soil profile with distinct physicochemical characteristics. The results revealed strong differentiation in assemblage richness and composition among strata, indicating that the subsurface consists of a mosaic of ecologically distinct microhabitats rather than a homogeneous environment. These patterns also highlight limitations in the current nomenclature used to classify subterranean strata, reinforcing the need for more refined approaches. In the second chapter, we investigated the influence of climatic variables, including temperature, humidity, precipitation, and soil temperature, on community richness and composition over time. Despite the relative thermal stability of the subsurface, subterranean assemblages responded significantly to climatic variation, exhibiting changes in richness and composition associated with environmental gradients. These results indicate that the subsurface does not function solely as a passive climatic refuge, but rather as a dynamic environment sensitive to external conditions. Overall, this dissertation advances the ecology of subterranean ants in neotropical karst ecosystems by highlighting the importance of vertical stratification, methodological choices, and climate in structuring these communities, and by reinforcing the relevance of the subsurface in biodiversity and conservation studies.