Programa de Pós-graduação em Física

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Estudo das interações dos surfactantes iônicos SDS, CTAC e HPS e miltefosina com membranas de leishmania, macrófagos e eritrócitos
(Universidade Federal de Goiás, 2023-09-18) Cardoso, Éder Jéferson Souza; Alonso, Antônio; http://lattes.cnpq.br/5013069863616789; Alonso, Antônio; Mendanha Neto, Sebastião Antônio; Silva, Kleber Santiago Freitas e
Miltefosine (MT) is an internationally approved oral drug for the treatment of leishmaniasis, however, its mechanism of action is not yet well established. Understanding the mechanism of action of compounds with leishmanicidal activity is important to help in the search for new drug prototypes with greater activity and fewer side effects. Surfactants are compounds widely used in the industry in the manufacture of soap, shampoos and other cosmetics. They are usually classified according to the molecular charge, and may be nonionic, anionic, cationic or zwitterionic (or amphoteric) when they have a positive and negative charge in the same compound. Electron Paramagnetic Resonance (RPE) spectroscopy associated with the spin-label method was used to compare the interactions of MT and the surfactants Sodium Dodecyl Sulfate (SDS, anionic), Cetyl Trimethyl Ammonium Chloride (CTAC, cationic) and N, N-dimethyl-3-ammonio-1-propanesulfonate (HPS, zwitterionic) with the membranes of Leishmania (L.) amazonensis, erythrocyte and macrophage. All compounds increased the molecular dynamics of membrane proteins; however, SDS caused the smallest increase in parasite and erythrocyte membrane dynamics and was also the least effective in antileishmanial activity, cytotoxicity in macrophages J774.A1 and hemolytic potential in both PBS and whole blood. It was detected, in blood plasma, the albumin stiffness caused by 2.5 mM SDS due to the electrostatic and hydrophobic interactions of the compound with the protein. CTAC did not show significant differences in relation to the other compounds, but at higher cell concentrations (>1x109 cells/mL), it showed high activity against the L. amazonensis promastigotes, besides being the most cytotoxic to macrophages J774.A1. For all the experiments, the zwitterionic molecules HPS and MT did not present significant differences between them. The data suggest the possibility of using cationic or zwitterionic surfactants in formulations containing leishmanicides, aiming at the treatment of cutaneous leishmaniasis.
Um estudo sobre termodinâmica e informação em modelos holográficos
(Universidade Federal de Goiás, 2024-12-20) Costa, Ronaldo Ferreira; Céleri, Lucas Chibebe; http://lattes.cnpq.br/6630683190018665; Pereira, Rômulo Cesar Rougemont; http://lattes.cnpq.br/9207462207391635; Pereira, Romulo Cesar Rougemont; Acevedo, Willians Oswaldo Barreto; Guimarães, Marcelo Santos
This dissertation addresses aspects of information theory and thermodynamics in the context of gauge/gravity duality, focusing on two specific holographic models: 1RCBH and 2RCBH. The study analyzes fundamental concepts of information theory, such as entanglement entropy and discusses gauge/gravity duality as a tool for analyzing thermodynamic and information properties of these models. Initially, we review in detail the thermodynamics of the 1RCBH model, which is a toy-model for a strongly-coupled quantum field theory at finite temperature and density and has a critical point in its phase diagram, while the 2RCBH model describes a different strongly-coupled quantum field theory, also defined at finite temperature and density, but without a critical point in its phase diagram. The main focus of the research is to calculate thermodynamic and information observables using holographic gauge/gravity duality in these models. We also review the entanglement entropy of the 1RCBH model, and, as an original contribution, we propose a new and more efficient method to evaluate it than previously considered in the literature. Due to some numerical issues still to be understood and solved, a detailed analysis of the entanglement entropy in the 1RCBH and 2RCBH models will be postponed to an upcoming work intended for publication.
Quebra de simetria em condensados de Bose-Einstein confinados por um potencial funil
(Universidade Federal de Goiás, 2021-04-09) Miranda, Bruno Martins; Cardoso, Wesley Bueno; http://lattes.cnpq.br/6845416823133684; Cardoso, Wesley Bueno; Malbouisson, Jorge Mário Carvalho; Almeida, Norton Gomes de
Theoretically predicted in 1923-1924 by Bose and Einstein and experimentally obtained only in 1995, the Bose-Einstein condensate became an important laboratory for the investigation of various quantum phenomena, such as the Josepshon oscillations, the study of vortex, use as interferometers, etc. Using mean-field theory to include the effects of the average interaction between particles, in the 1960s, Gross and Pitaevskii obtained an equation capable of describing the dynamics of a diluted gas at a temperature of 0 K. Dimensional reduction models for the Gross-Pitaevskii equation were developed for several types of confining potentials in order to simplify numerical calculations and reproduce accurate results. For condensates with a strong attractive strength, confined by doublewell potentials, it is known that the phenomenon of spontaneous symmetry breaking occurs. In this state, the particle population between wells becomes asymmetrical, in contrast with the symmetry of the confining potential. In this work, we consider a condensate in the self-focusing regime, confined transversely by a funnel-like potential and axially by a double well formed by the combination of two inverted Pöschl-Teller potentials. We used an effective equation, obtained by means of a variational method for the Gross-Pitaevskii equation, to analyze the symmetry break of the probability density of the wave function that describes the condensate. This symmetry break was observed for several interaction strength values as a function of the minimum potential well. A quantum phase diagram was obtained, in which it is possible to recognize the three phases of the system: symmetric phase (Josepshon), asymmetric phase (spontaneous symmetry breaking - SSB), and collapsed states, i.e., when the solution becomes singular, which does not represent the physical system, showing a validity limit for the model under consideration. We analyzed our symmetric and asymmetric solutions using the real-time evolution method, in which it was possible to confirm the stability of the results. Finally, a comparison with the cubic nonlinear Schrödinger equation in one dimension and the Gross-Pitaevskii equation in three dimensions is performed for the purpose of analyzing the accuracy of the effective equation used here.
Development and investigation of lanthanide-doped oxide nanocrystals for nanothermometry
(Universidade Federal de Goiás, 2024-11-14) Nogueira, Camila Tsuchida; Ibanez, Alain; Maia, Lauro June Queiroz; http://lattes.cnpq.br/9454054374479016; Carvalho, Jesiel Freitas; http://lattes.cnpq.br/5841291496427516; Carvalho, Jesiel Freitas; Maia, Lauro June Queiroz; Araújo, Eudes Borges de; Gomes, Danielle Cangussu de Castro
Temperature sensing with accuracy and good spectral resolution is highly sought in research and industry, especially in biomedicine and microelectronics, where conventional thermal probes are unsuitable for remote measurements below 10 μm. In biology, thermal monitoring can indicate inflammatory areas, diseases, and tumors. Previous studies suggest temperature monitoring is promising for early diagnosis and assisting disease treatments, such as hyperthermia for cancer treatment. In this regard, luminescent nanoprobes made of inorganic materials doped with rare-earth ions have emerged as an effective means to measure local temperature precisely and remotely. The thermal readout is obtained by tracking the Luminescence Intensity Ratio (LIR) between two photoluminescence (PL) emission lines, which evolves with temperature. A calibration curve between LIR and temperature can then be extracted from experimental data in the laboratory. Nonetheless, developing adequate luminescent nanothermometers for biological applications continues to be a major hurdle. These thermal sensors must be small, stable and well-dispersed in physiological solutions, nontoxic, and exhibit strong PL emissions within the biological windows (BWs) ¾ the wavelength ranges where light penetrates tissues deeply. This work focuses on oxides doped with rare-earth ions for nanothermometry in future biological applications, comprising the synthesis, characterization, and analysis of thermal sensing performance using PL emissions in the BWs of Y3Al5O12 (YAG), Y2O3, and Y4Al2O9 (YAM) co-doped with Nd3+ and Yb3+. The first two host matrices were synthesized via the modified Pechini method for co-doping engineering to optimize the concentrations of Nd3+ and Yb3+ for ideal PL emission. To obtain well-dispersed individual nanocrystals (NCs), YAG: Nd3+- Yb3+ and Y2O3: Nd3+-Yb3+ were synthesized by the solvothermal route and the two-step urea-based route, respectively, with conditions systematically optimized to fulfill the requirements of this thesis. The third host matrix, YAM, was also studied using the modified Pechini synthesis to investigate its thermal response when single-doped with Nd3+ and co-doped with Nd3+ and Yb3+. Lastly, a new synthesis method for YAM was explored. The findings showed that YAG: Nd3+-Yb3+ exhibited great potential, particularly after applying a silica coating around the NCs synthesized by the solvothermal route. This coating allowed annealing at 850°C to enhance the PL emission without agglomerating the NCs. The resulting YAG: Nd3+-Yb3+@SiO2 nanoparticles (NPs) had a final size of 87 ± 20 nm, a relative thermal sensitivity (Sr) of 0.60%.K-1, and thermal resolution (δT) of 0.2 K at physiological temperature. Y2O3: Nd3+-Yb3+ NCs of 22 ± 10 nm had Sr of ~ 0.50%.K-1, but δT ~ 0.4 K due to a lower signal-to-noise ratio. YAM, when single-doped with Nd3+, revealed competitive thermal response with Sr = 0.50%.K-1 and δT = 0.3 K at body temperature. However, co-doping YAM with both Nd3+ and Yb3+ ions hampers the thermal sensing efficiency to less than 0.40%.K-1 of Sr at physiological temperature, with δT fluctuating between 0.2 and 0.7 K across the temperature range. Thus, this study paves the way for improving the synthesis and applications of the oxides in nanothermometry and highlights promising prospects of Nd3+-Yb3+ co-doped YAG nanothermometers thanks to their decreased size, good thermal sensing features, and intense PL emission within the BWs.
The dynamical Casimir effect and the generation of thermodynamic entropy
(Universidade Federal de Goiás, 2024-03-12) Oliveira, Gustavo de; Céler, Lucas Chibebe; http://lattes.cnpq.br/6630683190018665; Céler, Lucas Chibebe; Landi, Gabriel Teixeira; Maia Neto, Paulo Américo
In this dissertation, we investigate the dynamics of the thermodynamic entropy production in the dynamical Casimir effect. This is done by considering a quantum scalar field confined by a one-dimensional cavity composed of a pair of ideal mirrors, one fixed and the other allowed to move in a prescribed trajectory. The central goal of this work is to understand how the thermodynamic entropy of the field evolves over time due to the particle creation process induced by the non trivial boundary conditions imposed by the moving mirror. By employing an effective Hamiltonian approach, the system’s entropy production is shown to increase with the number of particles created within the short-time limit. Moreover, one can also demonstrate that this approach is directly related to the generation of quantum coherence in the energy basis of the field. Utilizing a distinct method, grounded in the theory of Gaussian states, we were able to analyze the long-time limit of the entropy production for a single mode of the field. The obtained results establish a relationship between the increase in thermodynamic entropy in the field mode and the entanglement between the considered mode and the rest of the field mode structure. In this way, we link the entropy production in the field due to the dynamical Casimir effect with two fundamental features of quantum mechanics: quantum coherence and entanglement.
Simulação da razão de carga de múons atmosféricos utilizando o CORSIKA
(Universidade Federal de Goiás, 2023-10-18) Paulo Júnior, Ademar; Gomes, Ricardo Avelino; http://lattes.cnpq.br/6538341799051577; Gomes, Ricardo Avelino; Peixoto, Carlos José Todero; Valdiviesso, Gustavo do Amaral; Tognini, Stefano Castro; Braghin, Fábio Luis
The muon charge ratio, $R_{\mu} = N_{\mu^{+}}/N_{\mu^{-}}$, is a quantity that can be measured both at at different altitude levels from Earth's surface and in underground experiments. The muons result from the hadronic interactions developed in extensive air showers (EAS) created from the interaction of cosmic rays with nuclei in the atmosphere. The muon charge ratio allows obtaining important information both from the point of view of physics involving cosmic rays, and from the study of the ratio between neutrinos and antineutrinos, $\nu/\bar{\nu}$, since their production is directly connected to the muons. The present work is a study using Monte Carlo simulations of EAS produced by cosmic rays with energy between 100 and $10^{6}$ GeV generated by CORSIKA, using the high energy hadronic interaction models: QGSJETII-04, EPOS -LHC, DPMJET III, SYBILL 2.3c, VENUS and QGSJET01-C. EAS were simulated separately with protons as primaries and He nuclei, and these datasets were combined in the performed analyses. Simulations aimed to verify which one of these hadronic interaction models are able to reproduce the expected behavior for the energies involved considering the increase of $R_{\mu}$ due to the contribution of the kaons to the EAS. It was observed that, to the set formed by protons and He nuclei, with the exception of DPMJET, the other models reproduce an increase in $R_{\mu}$ as a function of the energy of the muons on the surface $E_{\mu }\cos\theta^{*}$. However, when compared to the data obtained in the MINOS, OPERA and CMS experiments, the results, in general, does not reproduce the increase in $R_{\mu}$. Our results show that it would be useful to improve these models so that they can reproduce the expected behavior of the muon charge ratio.
Identificação de estrelas do tipo A na base de dados do S-PLUS e estimativas de seus parâmetros atmosféricos
(Universidade Federal de Goiás, 2025-03-12) Sampaio, Franklin Tyerry Silva; Santucci, Rafael Miloni; http://lattes.cnpq.br/7644987837821138; Santucci, Rafael Miloni; Placco, Vinicius Moris; Perottoni, Hélio Dotto
This work aims to identify candidate A-type stars within the Southern Photometric Local Universe Survey (S-PLUS) database. The data from this purely photometric survey were cross-matched with other databases to gather reference spectroscopic and astrometric information. Through comparisons, limits were defined for the selection of A-type stars using S-PLUS photometry. With the aid of a robust statistical tool, the Gaussian Mixture Model (GMM), criteria were established to distinguish between blue horizontal branch (BHB) stars and main sequence stars in a sample of A-type stars from S-PLUS. The main atmospheric parameters, like Teff , log g and [Fe/H], were determined for thousands of A-type stars using a symbolic regression software. Finally, the distance were estimated through an absolute magnitude calibration for the selected BHB stars.
Investigação das propriedades de magneto-transporte das perovskitas La2-xCaxMnRuO6 com 1.0 ≤ x ≤ 2.0
(Universidade Federal de Goiás, 2025-01-23) Silva, Arthur Garcia; Bufaiçal, Leandro Felix de Sousa; http://lattes.cnpq.br/1392206843733548; Bufaiçal, Leandro Félix de Sousa; Silva, Eduardo Monteiro Granado da; Garcia, Flávio; Serrano, Raimundo Lora; Santana, Ricardo Costa de
In this thesis we describe the synthesis and characterization of the structural, electronic, magnetic, and electrical transport properties of polycrystalline samples of the La2-xCaxMnRuO6 perovskites, at concentrations x = 1.0, 1.5, 1.75 and 2.0. The main objective of this work was to investigate the effects of substituting La with Ca, with particular interest in the magnetoresistance effect, characterized by the change in electrical resistance in response to the application of a magnetic field. The polycrystalline samples investigated in this study were synthesized by conventional solid-state reaction and studied using experimental characterization techniques. These include x ray powder diffraction, magnetization as a function of temperature [M(T)] and applied magnetic field [M(H)], electrical resistivity as a function of temperature [ρ(T)] and as a function of field [ρ(H)], x ray absorption spectroscopy (XAS), and x ray magnetic circular dichroism (XMCD). All compounds crystallize with orthorhombic symmetry in the Pnma space group. M(T) measurements indicate that the x = 1.5 sample exhibits the highest magnetic ordering temperature, at approximately 291 K, very close to room temperature. The M(H) curves of the x = 1.0, 1.5, 1.75 and 2.0 samples show characteristic behavior of ferrimagnetic systems. The ρ(T) measurements indicate negative magnetoresistance along the whole temperature interval investigated. Compounds with x = 1.5, 1.75 and 2.0 exhibits ρ(T) curves typical of half-metal systems. XAS measurements at the Mn L2,3 edges indicate Mn3+/Mn4+ mixed valence in intermediate concentrations of the series, and the opposite XMCD signals observed for Mn and Ru suggest antiferromagnetic coupling between the transition metal ions.
Estudos de materiais dopados com íons lantanídeos para aplicações em nanotermometria
(Universidade Federal de Goiás, 2023-10-31) Silva, Daniel Lopo da; Maia, Lauro June Queiroz; http://lattes.cnpq.br/9454054374479016; Maia, Lauro June Queiroz; Poirier, Gaël Yves; Santana, Ricardo Costa de
Optical phenomena such as luminescence of materials depend on several characteristics such as temperature, dopants, crystalline structure, etc. Electromagnetic emissions from materials doped with rare-earth ions can provide thermal information regarding the environment where these materials are inserted. Materials with good thermal sensitivity are considered promising for the development of technologies for nanoscale temperature measurements. In this work, nine samples previously prepared through different synthesis routes such as sol-gel process and modified Pechini were analyzed. The samples studied have matrices of several compounds such as aluminum borates (Al4B2O9) monophasic and embedded in silica, aluminum germanates (Al6Ge2O13) monophasic and embedded in silica, yttrium borates (YBO3) and yttrium aluminum silicates (YAS). Altogether, five trivalent lanthanide ions were used as dopants of the samples: Nd, Eu, Er, Tb and Yb. The emission spectra of the samples were analyzed at seven different temperatures from 25 °C to 55 °C with a variation of 5 °C. Diffuse reflectance spectra were studied to confirm the presence of ions in the matrix and enable the calculation of the energy gap for each sample. From the emission spectrum, photoluminescent intensity ratios (RIFs) were calculated for the calculation of relative thermal sensitivities. The sample that showed the highest value for relative thermal sensitivity (Sr) was the one with the composition YBO3 : Nd3+, Eu3+, Er3+, Yb3+, Tb3+ synthesized at 900°C, presenting a value of Sr = (1,52 ± 0,20) %.K-1 in the temperature range of 35°C and 55°C.
Rigidez de membrana em leishmania amazonensis causada por lipossomas contendo miltefosina e/ou anfotericina B
(Universidade Federal de Goiás, 2024-09-06) Silva, Jean Carlo de Sousa e; Alonso, Antonio; http://lattes.cnpq.br/5013069863616789; Alonso, Antonio; Gomes, Rodrigo Saar; Lima, Eliana Martins; Silva, Kleber Santiago Freitas e; Mendanha Neto, Sebastião Antônio
Leishmaniasis is a tropical disease, still neglected, caused by protozoa of the genus Leishmania, representing a serious public health problem in many regions of the world. In this study, liposome formulations containing the leishmanicidal drugs miltefosine (MTF) and amphotericin B (AmB) were prepared. The liposomes are intended to function as carriers for the drugs, eliminating the need for potentially toxic organic solvents and aiding in their delivery to target cells. To characterize the liposomes, Dynamic Light Scattering (DLS) analysis was performed to assess vesicle size, and Zeta potential was measured to evaluate liposome stability. Drug quantification was carried out to estimate losses during the preparation process, using HPLC for MTF-containing liposomes and absorbance for AmB-containing liposomes. Electron Paramagnetic Resonance (EPR) was employed to uncover the crucial interactions of the drugs with the liposome membrane, the stratum corneum (SC), parasites, and macrophages, paving the way for significant advancements in the understanding of their mechanism of action. The formulations were applied to the SC to evaluate the outcome of their interaction with the liposomes. EPR data revealed that formulations containing soybean phosphatidylcholine (PC) caused an increase in stratum corneum fluidity, while those containing distearoylphosphatidylglycerol (a lipid found in commercial liposomal AmB) did not cause significant changes. The increase in fluidity provided by PC is expected to facilitate the targeted delivery of the compounds to the parasites, thereby enhancing therapeutic efficacy in the topical treatment of cutaneous leishmaniasis. The drugs, when encapsulated in liposomes, also caused increased rigidity in Leishmania membranes after 24 hours of exposure, suggesting that both drugs generate oxidative stress in the parasite. However, the formulations did not cause changes in the membrane of the uninfected macrophage. On the other hand, they caused membrane rigidity in the system of Leishmania-infected macrophages at concentrations in the range of their IC50 values in promastigotes. The EPR data also indicated that the membranes of the macrophageamastigote system can also undergo oxidative processes even without treatment. This work further showed that both MTF and AmB are active drugs at the plasma membrane of the Leishmania parasite and suggest that their antileishmanial mechanisms of activity are associated with their primary effects on the cell membrane. The increase in fluidity caused by MTF or the pore formation produced by AmB are membrane alterations that can likely result in ionic leakage, leading to plasma membrane depolarization, which in turn should hyperpolarize the mitochondrial membrane and thus increase the formation of reactive oxygen species (ROS), triggering other events such as membrane rigidity, which result in the death of the parasite. These findings have the potential to significantly contribute to the development of more effective and safer therapies for the treatment of leishmaniasis. However, additional studies are needed to validate these results in clinical trials and to further improve the liposomal formulations.
Entropy production in quantum systems and Nernst heat theorem for a single qubit
(Universidade Federal de Goiás, 2024-02-23) Sousa, Aryadine Fernandes de; Almeida, Norton Gomes de; http://lattes.cnpq.br/3182841849332242; Almeida, Norton Gomes de; Souza, Alexandre Martins de; Moraes Neto, Gentil Dias de
Classical thermodynamics, which focuses on macroscopic systems in equilibrium, has given rise to various theories to address systems out of equilibrium over time. Recently, quantum thermodynamics has emerged as a theory dedicated to describe microscopic quantum systems. A notable application of this theory is found in the development of thermal engines, where the working substance is a microscopic quantum system. In this work, we present the essential theoretical formulation to understand entropy production in quantum systems and its impact on thermal machines. The approach involves exploring quantum friction and conducting a deeper analysis of the laws of thermodynamics on a fundamental scale. Examining the effects of these phenomena in a Quantum Otto Heat Engine, we highlight the implications of quantum friction on engine performance. Particularly noteworthy is the observation that operating the cycle with a reservoir with effective negative temperature enhances the engine efficiency significantly. This improvement is attributed to strategic choices in the populations of excited states in the reservoirs, revealing an innovative approach to optimizing performance in quantum systems. Additionally, we extend the Nernst heat theorem for a single qubit. This result not only presents intriguing theoretical implications but is also supported by numerical simulations and experiments using Nuclear Magnetic Resonance (NMR). These pieces of evidence uphold the remarkable convergence of Helmholtz free energy and internal energy as the temperature approaches zero Kelvin, underscoring the practical applicability of these theorems in quantum systems.
Membranas formadas por peptídeos ácido glutâmico (E), fenilalanina (F) e lisina (K): um estudo energético e estrutural via dinâmica molecular
(Universidade Federal de Goiás, 2024-10-18) Sousa, Elias Rafael de; Oliveira, Guilherme Colherinhas de; http://lattes.cnpq.br/0171051425848743; Oliveira, Guilherme Colherinhas de; Almeida, Agnaldo Rosa de; Oliveira, Leonardo Bruno Assis; Cardoso, Wesley Bueno; Mendanha Neto, Sebastião Antônio
In this work, we developed a theoretical study on four models of peptide membranes formed by the amino acid sequence EF4K, (E) glutamic acid, (F) phenylalanine, and (K) lysine, where two models for the said sequence were created, Model-A and ModelB. Model-B differs by a 180o rotation in dimer 3, which composes the tetramer for membrane formation. The combination of the peptides EF4E and KF4K was carried out, creating two models for the said combination, Model-C and Model-D. In ModelC, the peptides were assembled asymmetrically to form the tetramer, and in Model-D, the peptides were arranged symmetrically to form the tetramer. Our results show, in all cases studied, a packing of the F4 group, characterizing the hydrophobic region of the structure, strongly formed by hydrogen bonds with lifetimes between 1.0 and 1.5 ns, depending on the model under analysis. The alternation in the polar head of the peptide in the nanostructure also strongly contributes to its stability and structural arrangement, demonstrating interactions similar to hydrogen bonds with lifetimes of 1.2–1.5 ns. This high interaction between the EF4K molecules forming the anomembrane is one of the factors ensuring the generation of long structures, as seen experimentally. Results for membranes formed by EF4E and KF4K show that the lifetime of hydrogen bonds (HBs) for Model-D peptides is approximately 12% longer than that observed for Model-C, providing greater rigidity to the former. These results are consistent with those obtained for Coulomb and van der Waals interaction energies and demonstrate that EF4E and KF4K (Model-D) presents better stability compared to EF4E and KF4K (Model-C). The average thickness of the membranes is approximately 1.72±0.06 nm and 2.27±0.02 nm, respectively. Our results also indicate that the EF4E and KF4K (Model-D) structure remains less hydrated in its interior

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