http://repositorio.ufc.br/handle/riufc/218 Thu, 09 Apr 2026 13:49:21 GMT 2026-04-09T13:49:21Z http://repositorio.ufc.br/handle/riufc/85730 Título: Ácido adipico em condições extremas de temperatura e pressão Autor(es): Silva, Rômulo Sampaio da Abstract: Dicarboxylic acids are organic compounds characterized by the presence of two carboxyl groups (COOH) in their molecular structure, which are responsible for their acidity. These compounds are found in more complex organic systems and play important roles in various chemical and biological processes. In addition, they attract significant interest due to their wide applicability in different industrial fields, making it essential to understand their physical and chemical properties under varying temperature and pressure conditions. In this context, this work investigates the structural behavior of adipic acid C6H10O4 under extreme temperature and pressure conditions through a combination of Raman spectroscopy, powder X-ray diffraction, and density functional theory (DFT) calculations. Initially, vibrational characterization was carried out under ambient conditions, allowing the classification and assignment of the observed modes with the support of computational calculations performed on the unit cell. At low temperatures, the sample was cooled down to 10 K, where a phase transition previously reported in the literature was observed in the range between 135 K and 130 K, accompanied by crystal fragmentation and significant changes in the Raman spectrum. In order to better understand these results, powder X-ray diffraction measurements were performed, revealing phase coexistence below the transition temperature, persisting down to approximately 10 K. Under high pressures, the sample was investigated up to values above 7 GPa in two independent Raman spectroscopy experiments. Significant changes in intermolecular vibrational modes, together with an increase in the number of modes above 1.6 GPa, indicated a phase transition associated with a reduction in the symmetry of the crystal structure. At higher pressures, variations in the intensities of internal modes suggest possible conformational changes of the molecules within the unit cell. The results obtained highlight the strong dependence of adipic acid on thermodynamic conditions, contributing to the understanding of phase transition mechanisms in this molecular system. Tipo: Tese Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/85730 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85588 Título: Estudo das propriedades vibracionais das perovskitas híbridas de azida Autor(es): Hora, Renata Rodrigues da Abstract: Recently, perovskite-type organic-inorganic hybrid compounds have attracted considerable interest due to their structural versatility, which allows for the manifestation of various interesting physical properties for application in devices. These materials exhibit a wide range of functionalities, including photovoltaic, ferroelectric, and multiferroic properties. In this thesis, we used the slow evaporation method to obtain three perovskite-type hybrid compounds, [(CH3)3N][Mn(N3)3] (TrMAMnN3), [(CH3)2NH][Mn(N3)3] (DMAMnN3), [(CH3)2NH]2[CoNa(N3)6], whose structural, thermal, and vibrational properties were investigated as a function of temperature. In the case of the compound [(CH3)3NH][Mn(N3)3], we analyzed in detail the wavenumber and full-width half-height (FWHM) of lattice modes and internal modes of the NC3 skeleton, N3– and CH3 molecular groups. In general, the modes exhibited unusual behavior during phase transitions, including discontinuity in phonon wavenumber, bandwidth, and unconventional changes due to temperature variation. Furthermore, we used differential scanning calorimetry (DSC) to confirm a subtle monoclinic-to-monoclinic phase transition (P21/c →C2/c) around 330 K; and the phase transition to trigonal structure (R m) above 359 K, whose associated entropy variation becomes |ΔS| ~ 22.3 J·kg⁻¹ K⁻¹ and exhibits a barocaloric coefficient (BC) |δTt/δP| ~ 3.17 K kbar⁻¹. For DMAMnN₃, a first-order structural transition from the orthorhombic phase (Cmca) to the monoclinic phase (P2₁) was identified, with an entropy variation of ~37.2 J·kg⁻¹·K⁻¹ and a barocaloric coefficient of ~2.94 K·kbar⁻¹, in agreement with the Clausius-Clapeyron method. Room-temperature Fourier transform infrared (FTIR) reflectivity spectra identified polar phonons and their damping coefficients. Minimal contributions from the DMA+ mode were observed in the intrinsic dielectric constant (~4.3). An anomaly was observed at ~85 K, indicating a transition from the paramagnetic to the antiferromagnetic state (PM-AFM). Finally, we present a new compound obtained through the slow evaporation synthesis [(CH3)2NH]2[CoNa(N3)6], where single-crystal XRD measurements resolved the material's structure, showing that up to 100 K the structure does not exhibit a structural phase transition. A room-temperature Raman spectrum was also obtained, and mode assignment was performed. Tipo: Tese Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/85588 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85545 Título: Análise biomecânica e perfil proteômico de células em resposta à absorção de luz vermelha Autor(es): Silva, Antônio Vinnie dos Santos Abstract: Photobiomodulation (PBM) is a non-invasive technique for tissue repair whose underlying cellular mechanisms still lack full understanding. Biomechanical responses of six cell lines were investigated under red light (633 nm) with different irradiance and time parameters (25 and 50 mW/cm² for 10 and 20 minutes). The cells were grouped as follows: (i) L929 fibroblasts, HaCaT keratinocytes, and OFCOL II osteoblasts; and (ii) C2C12 myoblasts, MG-63 osteosarcoma, and RAW 264.7 macrophages. Additionally, an integrated proteomic analysis of the first group was conducted to characterize the effects of irradiation from the epidermis to bone tissue. Using atomic force microscopy (AFM) and mass spectrometry, it was observed that red light induced cell-type-specific viscoelastic changes. L929 fibroblasts showed increased fluidity, decreased stiffness, and enhanced motility, while HaCaT keratinocytes exhibited irradiance-dependent responses. In contrast, OFCOL II osteoblasts were relatively insensitive to the treatment. RAW 264.7 macrophages demonstrated pronounced stiffening under higher doses and durations, reflecting their immune function and rapid cytoskeletal remodeling. C2C12 myoblasts showed moderate stiffness, with a slight increase in elasticity at higher doses. In the MG-63 sample, an increase in elastic modulus and a reduction in fluidity were observed, suggesting a reinforcement of the cytoskeletal structure. Proteomic analysis identified key roles in immune regulation, ATP production, and stress response, linking these pathways to viscoelastic modulation, especially in fibroblasts. Remodeling of the F-actin network, with contributions from microtubules and intermediate filaments, was identified as the primary mechanism for the mechanical changes. Our findings clarify how red light absorption influences cellular viscoelasticity via cytoskeletal rearrangement, providing insights for optimizing PBM-based therapies in tissue regeneration. Tipo: Tese Wed, 01 Jan 2025 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/85545 2025-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85017 Título: Eye-tracking as a proxy for coherence and complexity of texts, and for the interpretation of cytopathological images Autor(es): Torres, Débora Abstract: Eye movements offer a unique insight into cognitive processes, bridging the mechanics of vision with underlying neural activities. Through swift movements called “saccades”, our eyes direct attention to areas of interest, while “fixations” provide moments for detailed visual information gathering. In tasks like reading, fixation patterns reveal cognitive demands and processing depth. Eye tracking, a non-invasive method, captures these movements with precision, enabling the study of visual behavior across tasks and stimuli complexities. By analyzing eye movement data using statistical physics and machine learning tools, we gain insights into collective behaviors and cognitive processing patterns. Equipped with a cutting-edge eye tracker, our research focused on eye-tracking experiments across various visual tasks, resulting in two main projects published in reputable journals. Our primary project, “Eye-tracking as a Proxy for Text Complexity and Coherence”, involved experiments where participants read diverse texts. Using a binary model for fixation sequences akin to an Ising system integrated into the Maximum Entropy Model, we examined fixation patterns. Leveraging results from an extensive survey, we compared these findings with properties derived from eye-tracking experiments. Our analysis revealed a positive correlation between text complexity and average fixation density, measured by magnetizations. Additionally, statistical modeling and Pairwise Maximum-Entropy analysis demonstrated the effectiveness of critical point distance in assessing text coherence, indicating a potential for robust cognitive measures compared to conventional survey responses. In parallel, a collaborative project with the ``Engenheria em Teleinformatica'' post-graduate program focused on visual attention among cytopathologists analyzing Pap smear slides. This research offered insights into visual mechanisms during Pap smear analysis, potentially enhancing current practices and informing the development of innovative analysis techniques. Our investigation encompassed a review of visual attention dynamics, exploration of saliency learning models for medical diagnosis, and evaluation of eye-tracking applications in medical imaging. Through the comparison of eye fixation maps with saliency prediction algorithms, the reliability of these algorithms in detecting clinically relevant cells was assessed. The findings from our primary project demonstrate the robustness of the maximum-entropy approach for probing diverse complex systems effectively. Additionally, our observations highlight how humans respond cohesively to coherent textual information, reflecting advanced language formation and reading prediction mechanisms. Moreover, our secondary project revealed a significant agreement in gaze patterns among participants, supporting the identification of clinical Regions of Interest in Pap smear images. Further investigation into saliency models provided valuable insights into their predictive accuracy and potential implications for medical image interpretation. Lastly, our interdisciplinary research, spanning neuroscience, linguistics, and computer science, provided valuable insights into applying physical models to study cognitive activity. Tipo: Tese Mon, 01 Jan 2024 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/85017 2024-01-01T00:00:00Z