http://repositorio.ufc.br/handle/riufc/218 2026-04-08T15:17:16Z 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 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 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 2024-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/84400 Título: Caracterização não-extensiva de ondas gravitacionais: o formalismo do q-tripleto de Tsallis Autor(es): Silva, Cleo Vieira da Abstract: The existence of gravitational waves was predicted by Einstein in 1916 as perturbations in the curvature of spacetime generated by accelerated masses. A century later, their direct detection by the LIGO interferometers inaugurated a new era in observational astrophysics. However, the complexity and inherently out-of-equilibrium nature of these signals challenge traditional statistical models based on Boltzmann–Gibbs entropy. In this context, this thesis proposes the application of Tsallis non-extensive statistical mechanics as a framework to describe and interpret gravitational-wave signals across multiple scales. This study investigates, through Tsallis non-extensive statistics, the multiscale structure of gravitational-wave signals originating from coalescing binary systems, relating the exponents of the q-triplet (qstat, qsen, qrel) to the physical parameters of the gravitational waves. The methodology is based on the analysis of publicly available time series from the Hanford and Livingston detectors, which were subjected to filtering, segmentation, and normalization procedures. The q-triplet exponents were obtained by: (i) fitting q-Gaussian distributions (qstat ); (ii) multifractal detrended fluctuation analysis (MF-DFA) to estimate qsen; and (iii) computation of average mutual information (AMI) to determine qrel. Pearson and Spearman correlation analyses, as well as linear regressions, were performed between the q-indices and the physical variables of the binary systems. For the GW150914 event, the estimated q-triplet values indicated strong non-extensivity: {1.46; 0.02; 2.28}H for Hanford and {1.43; 0.25; 2.26}L for Livingston. In the multi-event analysis, qsen exhibited a strong correlation with the peak frequency (R2=0.78) under linear fitting, while qrel showed a moderate correlation with the chirp mass (R2=0.26). In contrast, qstat did not present statistically significant correlations, suggesting the influence of stochastic factors. The application of Tsallis non-extensive statistics proved effective in characterizing the multiscale complexity and out-of-equilibrium behavior of gravitational-wave signals. The use of the q-triplet emerges as a promising approach for identifying distinct dynamical regimes during black hole coalescence processes, contributing new methodological perspectives to the astrophysics of extreme systems. Tipo: Tese 2025-01-01T00:00:00Z