DSpace Coleção:https://repositorio.ufms.br/handle/123456789/36082026-07-22T13:24:14Z2026-07-22T13:24:14ZSexagem de Aves Utilizando Espectroscopia no Infravermelho por Transformada de Fourier e Machine Learninghttps://repositorio.ufms.br/handle/123456789/146202026-07-06T14:32:05Z2026-05-15T00:00:00ZTítulo: Sexagem de Aves Utilizando Espectroscopia no Infravermelho por Transformada de Fourier e Machine Learning
Abstract: Early identification of sex in birds plays a crucial role in reproduction, breeding,
commercialization, and scientific knowledge production. DNA-based molecular techniques have
been the primary approach for sex determination, distinguished by their accuracy and risk-free
nature for the bird, but they face challenges related to time consumption, costs, and the need for
specialized laboratories. This study investigates the application of Fourier Transform Infrared
Spectroscopy (FTIR) combined with machine learning algorithms as a non-invasive and precise
technique for early sex determination in birds, through measurements made in a feather region
known as the vexil. The research focuses on four species: Oryzoborus maximiliani (Bicudo),
Nymphicus hollandicus (Cockatiel), Oryzoborus angolensis (Curió), and Psittacula krameri
(Ring Neck). The methodology involved collecting feather FTIR spectra from young birds (sex
confirmed by DNA analysis) using the Attenuated Total Reflectance (ATR) accessory. Spectra
obtained in the range of 3800 to 800 cm⁻¹ were processed using Standard Normal Variate (SNV)
and subjected to Principal Component Analysis (PCA) to reduce dimensionality and identify
significant variables. The combination of FTIR with the Random Forest classifier demonstrated
promising results. Significant accuracies were obtained in the identification of bird sex, with
emphasis on Bicudo and Curió (94.4%), Cockatiel (77,8%) and Ring Neck (72,2%). In this way,
the study shows great potential for application in avian sexing and indicates the need for
additional studies to allow its generalized application in certain species.
Tipo: Tese2026-05-15T00:00:00ZInfluência dos Parâmetros de Anodização no Crescimento de Nanotubos de TiO2 Visando Sua Aplicação na Fotodegradação de Contaminantes Orgânicoshttps://repositorio.ufms.br/handle/123456789/144082026-05-28T17:27:45Z2026-01-01T00:00:00ZTítulo: Influência dos Parâmetros de Anodização no Crescimento de Nanotubos de TiO2 Visando Sua Aplicação na Fotodegradação de Contaminantes Orgânicos
Abstract: Titanium dioxide (TiO2) is a semiconductor with a prominent position for various
applications, mainly due to its chemical stability, non-toxicity, biocompatibility, and
environmental friendliness. Among these applications, photocatalytic processes for the
degradation of organic compounds and energy storage through the production of green
hydrogen stand out. However, despite its promise, many research groups are still seeking
to optimize its properties in order to enhance the photocatalytic properties of TiO2 and
make its production method simple, inexpensive, and environmentally viable. In this
sense, scaling up materials from bulk to nanostructures represents a significant increase
in the photocatalytic efficiency of TiO2, as it provides more adsorption/reactive sites and
transport pathways. Within this context, this work presents a systematic study of the
growth mechanisms of titanium nanotubes (TNTs) using the anodic oxidation technique.
For this purpose, metallic titanium (Ti) plates were used as anodes and a metallic copper
(Cu) plate as cathodes. Ammonium fluoride (NH4F) solution was used as the electrolyte.
Voltages of 10V, 20V, and 30V were used, and anodizing times of 30 min, 60 min, and
120 min were applied. During electrocorrosion, the electrolyte was kept under magnetic
stirring and at room temperature by a water cooling system. The distance between the
electrodes was kept fixed at 0.5 cm in all electrocorrosions. Once the process was
finished, the samples were subjected to heat treatment in a tubular furnace for 2 hours at
450ºC, with a ramp of 5ºC/min, at ambient pressure. The properties of the non-woven
fabrics (NTF) were studied by X-ray diffraction, Raman scattering, and Scanning
Electron Microscopy. Finally, the photocatalytic properties of the TNTs were evaluated
by photodegradation tests of methylene blue dye using a UV light source, which showed
greater effectiveness in samples anodized for 60 min at 30 V.
Tipo: Dissertação2026-01-01T00:00:00ZMagnetic Properties of the frustrated J1-J2 square lattice with Kondo interactionshttps://repositorio.ufms.br/handle/123456789/143782026-05-13T14:55:38Z2026-02-26T00:00:00ZTítulo: Magnetic Properties of the frustrated J1-J2 square lattice with Kondo interactions
Abstract: The magnetic and electronic properties of materials are governed by the complex interplay between localized exchange interactions and coupling with itinerant electrons. This work investigates the competition between magnetic frustration and the Kondo effect in a J1 − J2 square lattice. Magnetic frustration is introduced through competing nearest-neighbor (J1) and next-nearest-neighbor (J2) interactions. The Kondo effect, governed by the coupling JK, introduces a nonmagnetic screening mechanism via the formation of Kondo inglets. To solve the resulting Hamiltonian, we employ a rigorous Cluster Mean-Field (CMF) approximation coupled with exact diagonalization on a 4-site cluster. The methodology is validated by reproducing the known J1 − J2 phase diagram, which shows the suppression of the N´eel temperature (TN ) at the point of maximum frustration (J2/J1 ≈ 0.5). The results demonstrate that the introduction of JK further suppresses long-range magnetic order, promoting the formation of a Kondo singlet state, particularly in the highly frustrated regime. These findings characterize the quantum boundaries between magnetic and non-magnetic phases and provide a crucial foundation for mapping the full phase diagram across varying coupling strengths and electron densities.
Tipo: Dissertação2026-02-26T00:00:00ZSÍNTESE DE NANOPARTÍCULAS À BASE DE COBRE PARA APLICAÇÃO COMO ÂNODOS DE CÉLULAS A COMBUSTÍVEL MICROFLUÍDICAS IMPRESSAS EM 3D ALIMENTADAS POR METANOLhttps://repositorio.ufms.br/handle/123456789/143262026-03-03T21:24:20Z2025-01-01T00:00:00ZTítulo: SÍNTESE DE NANOPARTÍCULAS À BASE DE COBRE PARA APLICAÇÃO COMO ÂNODOS DE CÉLULAS A COMBUSTÍVEL MICROFLUÍDICAS IMPRESSAS EM 3D ALIMENTADAS POR METANOL
Abstract: Technological advances have increased the demand for low-power energy converters to supply portable devices such as laptops, smartphones, and smartwatches. This demand arises from growing social automation – communication mediated by electronic devices – and the widespread use of portable systems in healthcare, defense, and entertainment. In this context, miniaturized fuel cells (µFCs) have emerged as promising alternatives. However, their commercial implementation remains limited by: (i) unstable catalysts with low electrocatalytic activity and (ii) architectures that restrict power output. This work aimed to synthesize new materials for application as anodes in microfluidic µFCs. A simple, rapid, small-scale, and surfactant-free route was proposed for the synthesis of Cu nanoparticles (NPs) at room temperature under three distinct conditions: stationary (ST), magnetic stirring (MS), and ultrasonic bath (US). The catalytic activity toward methanol electrooxidation in alkaline medium was evaluated using electrochemical and spectroelectrochemical techniques, revealing higher current densities for the US-synthesized NPs. In situ FTIR analyses confirmed that all materials promote methanol oxidation to carbonate via a formate intermediate, without detectable CO formation. The US sample exhibited superior performance, associated with a higher surface proportion of Cu(OH)2, lower carbon contamination, and greater availability of active sites. At higher potentials, this sample further displayed distinct behavior, involving an additional step of formate formation and its subsequent conversion to carbonate (or CO2 in the thin-layer configuration), suggesting a more efficient reaction mechanism. Finally, a mixed-media µFC was constructed and fed with methanol in alkaline medium and sodium persulfate in acidic medium. The device, comprising a Carbon Paper™ (CP) anode modified with US-synthesized Cu NPs and a metal-free CP cathode, achieved a maximum current density of 0.56 mA cm-2 and a peak power density of 26 µW cm-2 at 100 µL min-1. These results confirm that the membrane-free configuration optimizes the performance of each half-cell and demonstrate the feasibility of µFCs with noble-metal-free anodes and fully metal-free cathodes, representing a promising alternative for sustainable energy conversion technologies.
Keywords: fuel cell; microfluidic; methanol electrooxidation; copper anode; metal-free cathode; in situ FTIR; energy conversion.
Tipo: Tese2025-01-01T00:00:00Z