https://repositorio.ufu.br/handle/123456789/5166 2026-08-11T14:29:47Z 2026-08-11T14:29:47Z https://repositorio.ufu.br/handle/123456789/49400 2026-08-11T06:28:50Z 2026-07-09T00:00:00Z

Title: Medida da atividade biológica de sementes de soja utilizando imagens de Laser Speckle Abstract: This study presents the application of Laser Speckle in analyzing the initial biological phases of soybean seeds, from their imbibition in a moist substrate to the activation of the germination process. This technique demonstrates high efficacy due to its high optical sensitivity and non-destructive nature. The applied computational methodology involves capturing the Biospeckle, calculating the Time History of Speckle Pattern (THSP), constructing the Co-Occurrence Matrix (COM), and extracting the Normalized Moment of Inertia (NMI). The latter quantifies the dynamics of the images, reflecting the sample’s level of biological activity at the time of measurement. The use of the NMI is crucial, as the normalization by the average image intensity ensures the reproducibility of the experiment. Without this mathematical adjustment, physical variables of the experimental setup, such as the laser wavelength and camera distance, could yield inaccurate measurements. Thus, this research consolidates the optical metrology technique by standardizing measurements through normalization and compares the results of the crop’s metabolic stages with traditional methods already established in seed biology. The experimental results revealed that the biological activity, quantified by the NMI, reached a peak value of approximately 0.15 for the Olimpo IPRO soybean and 0.065 for the NEO 790 IPRO variety. While these quantitative findings are fundamental for validating the Laser Speckle technique, the qualitative analysis of the results is equally valuable in this study. By analyzing the temporal behavior of the obtained curve, it was possible to establish a correlation with the triphasic pattern of seed hydration, validating the Biospeckle technique as a sensitive and viable tool for the continuous and non-invasive monitoring of agricultural development.

2026-07-09T00:00:00Z https://repositorio.ufu.br/handle/123456789/49359 2026-08-08T06:23:10Z 2026-02-23T00:00:00Z

Title: Caracterização fotofísica dos derivados de Carbazol e Tetrazina para sensoriamento de radiação ultravioleta Abstract: This work investigates the photophysical properties and charge transport mechanisms in donor–acceptor conjugated polymers derived from carbazole and tetrazine. The ma terials analyzed were synthesized at the Paulo Scarpa Polymer Laboratory (LaPPS), Federal University of Paraná (UFPR). The polymer LaPPS80 is based on the carba zole–tetrazine combination (2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2yl)-9-(tridecan 7-yl)-9H-carbazole- alt-3,6-bis(4-octylthiophen-2-yl)-1,2,4,5-tetrazine), whereas LaPPS81 is derived from condensed carbazole–tetrazine (5,11-bis(2-ethylhexyl)dihydroindolo[3,2 b]-carbazole-alt- 3,6-bis(4-octylthiophen-2-yl)-1,2,4,5-tetrazine). It is worth noting that LaPPS81 can be obtained through different synthetic routes and is therefore denoted throughout this work as LaPPS81-C and LaPPS81-S. This study proposes a novel application of these materials as selective photodetectors in the ultraviolet–visible region. Spectroscopic characterization by optical absorption, photoluminescence (PL), and photoluminescence excitation (PLE) revealed that the transition from solution to the solid state (thin films) induces strong intermolecular interactions. These interactions are evidenced by Stokes shifts on the order of approximately 59 nm, 101 nm, and 139 nm, as well as by pronounced red-shifts in the emission spectra. These results indicate the formation of molecular aggregates and delocalized excited states, which play a key role in charge transport in these polymeric systems. Photoresistor devices with planar architecture and interdigitated fluorine-doped tin oxide (FTO) electrodes were fabricated and characterized. Morphological and electrical analyses showed that the oligomer LaPPS81-C, due to its low molar mass, does not form efficient percolation networks. In contrast, the polymers LaPPS80 and LaPPS81-S yielded func tional devices with distinct and complementary physical behaviors. LaPPS80 exhibited maximum sensitivity at 450 nm but showed the anomalous phenomenon of negative photoconductivity (NPC) under UV excitation (280–370 nm), attributed to the activation of deep recombination centers by high-energy photons. LaPPS81-S demonstrated positive photoconductivity, with high selectivity at 370 nm, and notable anisotropy in the response to light polarization, indicating a macroscopic molecular alignment that favors directional charge transport. Electrical stability tests (20 voltage sweep cycles) indicated the robustness of the devices, which maintained ohmic behavior without significant degradation or hysteresis. Analysis of the I–V curves suggested the predominance of direct tunneling injection mechanisms at low electric fields, with a transition to regimes consistent with field emission at higher voltages. Impedance spectroscopy corroborated the modulation of bulk resistance under illumination, indicating that LaPPS81 exhibits higher intrinsic conductivity compared to LaPPS80. Taken together, these results suggest that the LaPPS family holds potential for application in selective optical sensors, with responses that can be tuned through molecular engineering and morphological control.

2026-02-23T00:00:00Z https://repositorio.ufu.br/handle/123456789/49341 2026-08-07T06:23:15Z 2026-02-27T00:00:00Z

Title: Dinâmica de Skyrmions Abstract: Random Access Memory (RAM) is of paramount importance in modern electronics, determining both processing quality and speed. However, its evolution is reaching physical limits, necessitating research into alternative memory types. This work contributes to these efforts by studying a magnetic texture that promises to be a major breakthrough for future data storage: the skyrmion. This magnetic quasi-particle is a vortex-like spin configuration. Being topologically stable, skyrmions are protected against information loss, enabling the development of high-density non-volatile memory. This study aims to understand the movement of these textures through Spin-Transfer Torque. To this end, micromagnetic simulations were performed using the MuMax3 software, based on the Landau–Lifshitz–Gilbert (LLG) equation and the STT models of Zhang-Li and Slonczewski. We observed their locomotion and resulting effects, focusing on a primary challenge for technological application: the Skyrmion Hall Effect, which consists of a transverse path deflection driven by the Magnus force

2026-02-27T00:00:00Z https://repositorio.ufu.br/handle/123456789/49266 2026-08-05T06:21:30Z 2026-07-31T00:00:00Z

Title: Do Jaynes–Cummings ao modelo de Dicke: emaranhamento e efeitos coletivos em sistemas Qubit–Bóson

2026-07-31T00:00:00Z