Doutorado em Física (IF)

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Caracterização espectroscópica da Bufotenina e do óxido de bufotenina e suas interações com membranas modelo
(Universidade Federal de Goiás, 2022-07-21) Silva, Gustavo Almeida e; Marquezin, Cássia Alessandra; http://lattes.cnpq.br/1870152384940446; Marquezin, Cássia Alessandra; Souza, Eduardo Sérgio de; Muniz, Gabriel Silva Vignoli; Riske, Karin do Amaral; Alonso, Antônio
In this work, optical absorption and fluorescence emission properties of 5-hydroxy-N,N-dimethyltryptamine (Bufotenine) and N-oxi-5-hydroxy-N-N-dimethyltryptamine (Bufotenine oxide) were studied. In the presence of organic solvents the molecules presented two optical absorption bands; the spectra indicate a red shift in an aprotic solvent. The absorption coefficients of both molecules in several solvents were calculated. Also in the presence of organic solvents, fluorescent emission spectra were obtained, and it was observed that the intensity decreases with increasing the polarity of the medium. Fluorescence anisotropy measurements in the several solvents suggest that no aggregates are present in the concentration range studied. In aqueous solution the molecules showed fluorescence over a wide pH range. Changes in the absorption and emission spectra were observed for different pH values, suggesting the existence of different absorber structures (protonated/deprotonated species). The results for the molecules in the presence of surfactants suggest that molecules are located on the outer surface of the micelle, above a specific concentration of the surfactant. In the presence of model cell membranes, the results show that the molecules are located at the interface between the polar groups of the phospholipids and the water.
Hydrogen storage in two-dimensional transition-metal dichalcogenides
(Universidade Federal de Goiás, 2025-02-21) Oliveira, Flávio Bento de; Rosa, Andreia Luisa da; http://lattes.cnpq.br/1038061895538870; Rosa, Andreia Luisa da; Dias, Alexandre Cavalheiro; Moujaess, Elie Albert; Medeiros, Renato; Pontes, Renato Borges
Embargado.
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.
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.
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
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.
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.
Estudo teórico sobre membranas peptídicas e lipídicas: uma análise via dinâmica molecular
(Universidade Federal de Goiás, 2021-08-10) Alves, Eyber Domingos; Oliveira, Guilherme Colherinhas de; http://lattes.cnpq.br/0171051425848743; Oliveira, Guilherme Colherinhas de; Castro, Marcos Antonio de; Almeida, Norton Gomes de; Ludwig, Valdemir Eneias; Fileti, Eudes Eterno
In this work, the molecular dynamics formalism was used to study the physicochemical properties of peptide and lipid membranes when immersed in solution. Concerningpeptide membranes, the energetic and structural properties were evaluated in the situations in which these membranes were immersed in the Ionic Liquid (IL) formed by the choline (COL) and glycine (GLY) pair. The results indicate the existence of energetic and structural stability of these membranes when in IL, with potential application in energy storage in biodegradable supercapacitors. For lipid membranes, we used the umbrella sampling technique to proceed with a series of 150 insertions of the Fullerene-C 60 molecule in four lipid membranes composed of DOPC (Dipalmitoylphosphatidylcholine) at a ratio of 00% (pure membrane), 10%, 20% and 30% of cholesterol molecules, evaluating the average behavior of molecular insertion energies. The results showed that the presence of cholesterol molecules makes the inclusion process of Fullerene-C 60 energetically unfavorable. Under the computational pathway, we evaluated the pharmacological characteristics associated with monomers constructed based on peptides. For this purpose, we interact the lipid membranes composed of DOPC (Dipalmitoylphosphatidylcholine) at a proportion of 00% (pure membrane), 10% and 30% of cholesterol molecules with the peptide drug L-GL13K. The results reveal that the hydrogen bonds between the compound L-GL13K and the DOPC molecules promote membrane destabilization and increasing the infiltration of water molecules.
Cerâmicas multifuncionais de oxido de zinco dopadas com cobalto: propriedades ópticas, dielétricas e magnéticas
(Universidade Federal de Goiás, 2019-10-23) Silva, Hermínia Veridiana dos Santos Pessoni e; Franco Júnior, Adolfo; http://lattes.cnpq.br/0187547195548392; Franco Júnior, Adolfo; Machado, Fernando Luis de Araujo; Silva, Sebastião Willian da; Bufaiçal, Leandro Felix de Sousa; Rosa, Andreia Luisa da
In this work, Zinc oxide Cobalt-doped ceramics (Zn1−xCoxO) were produced with 0,00≤x≤0,05 molar concentrations to obtain multifunctional materials. The Solid State Reaction with slow pressing step and maximum sintering temperature of T=1150ºC was used. Structural characterization by Apparent Density (ρap), Energy Dispersion Spectroscopy (EDS), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) indicated formation of typical ZnO hexagonal wurtizite phase for all samples (space group - P63mc (C6v)), without formation of spurious phases and good stoichiometric measured coherence. The results also indicated good densification for the ceramics (ρrel=97−91%). The optical characterizations performed by Infrared (FTIR), UV-Vis and Raman allowed the observation of the characteristic vibrational modes of ZnO and the confirmation of the total introduction of Co ions in the tetrahedral sites in the lattice, it also allows the study of evolution in the defects’ amount of VO and Zni type and systematic reduction of optical bandgap Eg due to doping. Electrical characterizations performed by Dielectric Permittivity Spectroscopy (EPD) and Impedance revealed Colossal Dielectric Permittivity (PDC) behavior in all samples (ϵ’~105) and, doping intensifies the effect. The overall dielectric behavior of ceramics is consistent with the Maxwell-Wagner (MW) dielectric relaxation model, which was also used to explain the PDC phenomenon. Magnetic characterizations performed using Magnetic Hysteresis, Zero Field / Field Cooling (ZFC / FC) and Electronic Paramagnetic Resonance (EPR) measurements indicated diamagnetic ordering (DM) in the pure sample and predominant paramagnetic (PM) ordering in the doped samples, as well antiferromagnetic ordering (AFM) in doped samples due to the approximation of Co ions in the lattice (sample x=0,05 - 62%PM×38%AFM). Weak Co-ion spin-orbit coupling has been identified in the presence of the ZnO crystalline field. Non-occurrence of ferromagnetism (FM) was discussed in terms of the defects’ placement in ZnO samples.
Versatilidade estrutural de aminoácidos agregados: design de nanomateriais orgânicos via dinâmica molecular
(Universidade Federal de Goiás, 2022-02-25) Andrade, Douglas Xavier de; Oliveira, Guilherme Colherinhas de; http://lattes.cnpq.br/0171051425848743; Oliveira, Guilherme Colherinhas de; Cruzeiro, Vinícius Wilian dias; Fonseca, Tertius Lima da; Ludwig, Valdemir Eneias; Georg, Herbert de Castro
In this work, we carried out structural and energetic characterization of nine nanomembranes and two nanofibers composed of surfactant-like peptides (SLPs), using Molecular Dynamics (MD) simulations with atomistic resolution. The nanomembranes [nanofibers] studied are formed by the peptides I3V3A3G3K3 and K3G3A3V3I3 [G3A3V3I3K3 and K3I3V3A3G3]; A6Hε and A6Hδ; and I3XGK (X = Q, S, N, G or L). The nanomembranes I3V3A3G3K3 and K3G3A3V3I3 are formed by the same amino acids, but linked in inverted primary sequences, which changes torsions, the side chains, and the C and N peptide terminals, affecting the hydration and stability of the nanomembranes. The A6Hε and A6Hδ nanomembranes are differentiated by the position of the hydrogen atom attached to the aromatic ring of histidine (H) residues, alterning the way that this residue is exposed to water, and consequently, the lateral attachment of alanine residues (A). By studying the I3XGK (X = Q, S, N, G or L) nanomembranes, we realized that the peptides with polar residues (X = Q, S, or N) present properties of polar zippers connecting β-sheets laterally. Therefore, this work aims at elucidating and characterizing the formation of polar zippers that, recently, have attracted significant scientific and technological interest. The nanofibers G3A3V3I3K3 and K3I3V3A3G3 are formed by peptides with the same amino acids, but linked in inverted primary sequences, similar to the case of the nanomembranes I3V3A3G3K3 and K3G3A3V3. This way, by studying nanomembranes and nanofibers composed with the same amino acids, this work allows us to understand how changes in the disposition of the peptide side chains lead to the formation of distinct nanostructures, evidencing the structural versatility of aggregate amino acids. The analyses performed are based on the mass density profiles, on nanomembrane thicknesses, on the radial distribution functions, g(r), on the average number of Hydrogen Bonds (HBs) between amino acids and between each amino acid and water molecules - for a better characterization of HBs between peptides and consequently the nanomembranes’ hydration, HB’s time correlation functions are presented - and in the Coulombic and vdW energetic interactions which together with the HBs play a fundamental role in the organization of the peptides forming the nanostructures. Our results indicate that the C-terminal attached to the charged lysine (K) leads to the formation of more hydrated nanomembranes; the A6Hε and A6Hδ are nanostructures with a high degree of organization and with features of crystalline structures; the polar zippers present an interesting route for the design of robust and stable nanostructures, by joining neighboring β-sheets; the peptide nanostructures presented in this work have interesting characteristics suggesting that they can be used to encapsulate and transport drugs, as hydrogels and as an antimicrobial agent. Our MD results show excellent agreement with experimental data reported in the literature. In addition, we show that the CHARMM36 force field could be recommended for the study of the peptide nanomembranes and nanofibers presented. This validation is important because it allows the prediction from the theoretical point of view of new features of peptide structures of this species, providing advances in the development of organic nanostructures.
Stability and aromaticity of small neutral and charged boron clusters: a quantum Monte Carlo study
(Universidade Federal de Goiás, 2019-07-26) Moreira, Emanuel Melo Isaac; Silva, Ladir Cândido da; http://lattes.cnpq.br/7442411485710574; Silva, Ladir Cândido da; Oliveira, Marcos Cesar de; Oliveira, Heibbe Cristhian Benedito de; Oliveira, Guilherme Colherinhas de; Vale, Renato Pessoa
Neste trabalho, investigamos as energias de ligação eletrônica dos clusters de boro neutros Bn, com n = 3 até n = 13, seus ânions e cátions, usando uma combinação dos métodos, Monte Carlo quântico na aproximação dos nós fixos (FN-DMC), teoria do funcional da densidade e Hartree-Fock. As energias de ligação eletrônica como adiabatic detachment energy, vertical detachment energy, adiabatic ionization potential e vertical ionization potential foram examinadas para diferentes isômeros, e os valores obtidos estão em excelente concordância com resultados disponíveis na literatura, indicando que as geometrias dos clusters de boro, obtidas neste trabalho, estão corretas. A decomposição dessas energias de ligação eletrônica em três componentes físicas como, o potencial eletrostático e a interação de exchange, a energia de relaxação, a qual inclui a relaxação da geometria e dos orbitais, e a correlação eletrônica, nos permitiu determinar que os clusters de boro neutros são estabilizados pelas interações eletrostática e de exchange, enquanto os clusters aniônicos são estabilizados pela energia eletrostática e exchange, energia de relaxação e efeitos de correlação eletrônica. Também investigamos a aromaticidade de pequenos clusters de boro com três e quatro átomos através de princípios de estrutura eletrônica e energia de ressonância. Os resultados FN-DMC aplicados aos princípios de estrutura eletrônica para a energia, hardness e electrophilicity suportam a aromaticidade dos clusters B3-, B4- e B4 , e parcialmente suportam a aromaticidade dos clusters B3 , B3+ e B4+. Os valores obtidos para a energia de ressonância dos clusters B3, B3-, B3+, B4, B4- e B4+ foram: 55.1(7), 54.2(8), 33.9(7), 84(1), 67(1), and 58(1) kcal/mol, respectivamente. Então, a ordem decrescente de estabilidade do trímero é B3- > B3 > B3+, enquanto que paro o tetrâmero é B4 > B4+ > B4- , o que está de acordo com resultados de análise de orbitais.
Estudo das interações de porfirinas com sistemas de interesse biológico: potencial uso no transporte de fármacos e aplicação fotodinâmica
(Universidade Federal de Goiás, 2019-08-23) Bezerra, Fábio de Castro; Gonçalves, Pablo José; http://lattes.cnpq.br/0515343409614452; Gonçalves, Pablo José; De Boni, Leonardo; Iglesias, Bernardo Almeida; Borissevitch, Iouri; Alonso, Antonio
The purpose of this work was to study the interactions of porphyrins in systems of biological interest aiming at drug transport and photodynamic applications. Interactions of anionic meso-tetrakis(p-sulphonatephenyl) porphyrin (TPPS4) and cationic meso-tetrakis (4- methyl-pyridyl) porphyrin (TMPyP) porphyrins with bovine serum albumin (BSA), antibodies, DNA and biocompatible nanoparticles of maghemite were evaluated. To obtain the binding constants and thermodynamic parameters, spectroscopic UV/Vis absorption and fluorescence techniques were used. Binding constants indicate a higher affinity of porphyrin TPPS4 for proteins compared to TMPyP. Thermodynamic parameters showed that electrostatic and hydrophobic interactions mediated the BSA interactions with the porphyrins TPPS4 and TMPyP, respectively. On the other hand, the nature of porphyrin-antibody interactions shows a behavior opposite to that observed for BSA (electrostatic for TMPyP and hydrophobic for TPPS4), indicating that the binding site of porphyrin TMPyP in the antibodies is likely to have a net negative charge. In the porphyrin TPPS4 interaction with maghemite nanoparticles, besides obtaining the binding parameters of the interaction, it was possible to estimate the number of 21 porphyrins coupled in each nanoparticle. Regarding the interaction of DNA with the porphyrins TPPS4, TMPyP and its complexes with zinc, it was observed that ZnTMPyP has higher affinity for DNA than TMPyP, whereas TPPS4 and ZnTPPS4 do not bind to DNA, which explains the results of photodegradation of DNA by these porphyrins. Keywords: Photodynamic
Markov monogamy inequalities
(Universidade Federal de Goiás, 2022-03-09) Capela, Matheus; Araújo, Rafael Chaves Souto; ttp://lattes.cnpq.br/1509277905143351; Céleri, Lucas Chibebe; http://lattes.cnpq.br/6630683190018665; Celeri, Lucas Chibebe; Avelar, Ardiley Torres; Oliveira, Thiago Rodrigues de; Santos, Marcelo Paleologo Elefteriadis de Franca; Pinto, Diogo de Oliveira Soares
O estudo dos limites na comunicação com canais ruidosos é um problema central na teoria de informação. Data processing inequalities são de fundamental importância sob esta perspectiva. Entretanto, estas não são as as únicas condições existentes sob o processamento de informação. Neste trabalho, apresentamos uma nova categoria de condições chamadas Markov monogamy inequalities. Estes novos resultados são aplicados ao estudo e caracterização de processos não-Markovianos clássicos e quânticos. De grande importância, as condições Markov monogamy inequalities revelam-se serem mais eficientes que as data processing inequalities na certificação de processos não-Markovianos em determinados exemplos.
Eficiência de um motor térmico de Otto quântico baseado em um sistema de dois níveis
(Universidade Federal de Goiás, 2021-12-09) Assis, Rogério Jorge de; Almeida, Norton Gomes de; http://lattes.cnpq.br/3182841849332242; Almeida, Norton Gomes de; Serra, Roberto Menezes; Cardoso, Wesley Bueno; Brito, Frederico Borges de; Pinto, Diogo de Oliveira Soares
Classical thermodynamics, also called equilibrium thermodynamics, is a theory that deals with macroscopic systems in equilibrium. After its development, other theories emerged to encompass macroscopic out-of-equilibrium systems. Over the past few decades, researchers have developed a new theory to describe also the thermodynamics of microscopic quantum systems, which became known as quantum thermodynamics. An important application of this theory is in the development of heat engines in which the working substance (the substance responsible for transforming heat into work) is a microscopic quantum system. Due to their composition, these devices came to be commonly called quantum heat engines. Notably, recent studies have shown that using an out-of-equilibrium reservoir as a heat source can improve the performance of quantum heat engines, compared to the usual case where the heat source is an equilibrium reservoir (a thermal reservoir). In this context, this thesis presents two studies related to a quantum Otto heat engine whose working substance is a two-level system: in the first study, the engine has a squeezed thermal reservoir as the heat source, while in the second study, the heat source is a reservoir with a negative temperature. Both studies explore the finite-time regime of the expansion and compression stages of the heat engine. The first study shows that the engine efficiency can be greater than the Carnot efficiency in both the quasi-static and finite-time regimes. However, as in the usual case, decreasing the time of the expansion and compression stages degrades the engine efficiency. In its turn, the second study shows that the engine efficiency can surpass the Otto efficiency in the finite-time regime. Here, different from the usual case, decreasing the time of the expansion and compression stages can increase the engine's efficiency. Finally, the present thesis shows an experimental scheme in the nuclear magnetic resonance context able to provide a proof of concept for the engine in the different situations studied.
Simulações entrópicas do modelo de Bell-Lavis para a água
(Universidade Federal de Goiás, 2020-04-07) Ferreira, Lucas de Souza; Caparica, Álvaro de Almeida; http://lattes.cnpq.br/4726638254587108; Caparica, Álvaro de Almeida; Rabelo, José Nicodemos Teixeira; Bakuzis, Andris Figueiroa; Chahine, Jorge; Barbosa, Marco Aurélio Alves
In this work we used the entropic sample simulation to study the Bell-Lavis model for the liquid water. We estimed the joint density of states with which we obtain the average of the termodynamic properties of the energy, specific heat, density of particles, hydrogen bond energies, and the susceptibility of the density of particles to many values of the constants H and μ. Through of the analyze of this quantities we determined the possible ground states and the values for H and μ for which happen the transition between the ground states. We observe that for H = 1, 0 and 0, 0 < μ < 0, 5 the density of particles shows a maximum associated to transition from a configuration of low density to a configuration of high density. In this range the specific heat show two maxima, the first associated to maximum in the density, and do not shows finite size effects , and the second a transition order disorder. For 0.5 < μ < 1.5 we have only one maximum for the specific heat which is the fusion of the two before. We performed a finite size scaling study for μ = 1, 0 observing the thermodynamic quantities that characterize a second order fase transition and we found a critical temperature Tc = 0, 510718(49), while when observing the thermodynamic quantities that characterize a first order fase transition we obtain Tc = 0, 564520(37). Such results indicate the presence of two orders of phase transitions at very close temperatures. For understand the behavior we analise the order parameter to the one dimensional Ising model and conclude that the right choice of the order parameter for the model is decisive to visualize the phase transition. For the Bell-Lavis model the choice of this parameter is yet a challenge to be overcome.
Junções moleculares: O impacto dos eletrodos e dos grupos ancoradores nas propriedades estruturais, eletrônicas e de transporte
(Universidade Federal de Goiás, 2019-03-26) Silva, Carlos Eduardo; Pontes, Renato Borges; http://lattes.cnpq.br/2008125431826046; Pontes, Renato Borges; Sousa, José Eduardo Padilha de; Miwa, Roberto Hiroki; Bakuzis, Andris Figueiroa; Castro, Marcos Antônio de
In this Thesis we performed atomistic first-principles calculations aiming to investigate the structural, electronic, and transport properties of single-molecule junctions formed by electrodes of gold (Au), silver (Ag), or copper (Cu), and 1,4-benzenediamine or 1,4- benzeneaminethiol (only to gold electrodes) molecules. Such molecules were studied under two conditions: (i) with the hydrogen atoms linked to the anchoring groups (BDAH 4 and BATH 3 ), and (ii) without the hydrogen atoms linked in the anchoring groups (BDA and BAT). This work shows that intensity of the interaction of the molecule BDAH 4 with the electrodes of Au, Ag, and Cu follows the trend: Cu > Au > Ag. For the electronic transport properties, it is observed that the transmittance, at the Fermi level, of the junctions containing the molecule BDAH 4 occur due to the HOMO of this molecule and, in addition, the transmission coefficients follow the order: T(E F ) Au = 2,54 × 10 −2 > T (E F ) Cu = 1,97 × 10 −2 > T(E F ) Ag = 1,96 × 10 −2 , which is in good agreement with the work function of the metallic electrodes. For the junctions with the molecule BDA, the same tendency, for the intensity of the interaction, that the junctions containing the molecule BDAH 4 is obtained (Cu > Au > Ag). On the other hand, a significant increasing in the intensity of the interaction with the Au, Ag, and Cu electrodes, can also be seen, with respect to the junctions containing the molecule BDAH 4 . In addition, there is an increasing in the mechanical stretching of these junctions. The length of the elongations is in agreement with the reorganization capacity of the atoms that compose the electrodes. On the absence of the hydrogen atoms in the anchoring groups, the molecule BDA becomes spin-dependent, and when it is coupled to the metallic electrodes this spin-dependence vary with mechanical stretching of the junctions. Thus, the spin-resolved transmittances of these junctions are dependent upon the stretching of the junction. It is also verified that the Au/BATH 3 /Au junction exhibit mechanical and electronic transport properties similar to the Au/BDAH 4 /Au junction, since the rupture of the junction occurred between an atom of the tip and the nitrogen atom. However, for the Au/BAT/Au junction the rupture occurs between the atom of the tip of the electrode and the sulfur atom. It was verified that this occurs due to the intensity of the interaction between the electrode atoms and sulfur (1,09 eV) to be smaller than the interaction of the nitrogen (1,28 eV). Finally, by analyzing the DFT-NEGF calculated I × V curves, for the junctions Au, Ag, Cu/BDAH 4 ,BDA/Cu, Ag, Au and Au/BATH 3 ,BAT/Au, we verified an ohmic behavior, with a weak rectification performance.
Decoerência quântica em neutrinos de aceleradores
(Universidade Federal de Goiás, 2019-03-18) Gomes, Abner Leonel Gadelha; Gomes, Ricardo Avelino; http://lattes.cnpq.br/6538341799051577; Nunokawa, Hiroshi; Guzzo, Marcelo Moraes; Avelar, Ardiley Torres; Cardoso, Wesley Bueno; Gomes, Ricardo Avelino
In this thesis we investigate the three flavor neutrino oscillation in vacuum considering the open quantum system framework. This allow us to introduce the quantum decoherence effects in the temporal evolution dynamics of neutrinos eigenstates. The characterization of this effect is given by Г12, Г13 and Г23 parameters, which are associated with the decoherence effects in which there is no neutrino energy dissipation, and the Г33 and Г88, which correspond to possible dissipative effects. We propose some possible scenarios to investigate the effects of decoherence on neutrino systems. In each of these scenarios we assume only one parameter of decoherence Г. In our analysis we consider a phenomenology for the parameter of decoherence, which Γ has a neutrino energy (E) dependence, by a law-power given by n and by a constant γ0, which is the decoherence parameter without energy dependence. This is the parameterization most used in studies that include quantum decoherence in neutrinos, in which where we consider to this analysis, n=-2, 0, 2. This formalism was applied to the data of the disappearance analysis of MINOS FHC and in the neutrino run and anti-neutrino run configurations of both disappearance and appearence analysis of T2K. We had as aim obtain new possibles limits to the quantum decoherence with the analyzed data to the different proposed scenarios. We have showed that for n=-2 and n=0 we obtained limits in the order of O(1E−23) GeV and for n=2, in the order of O(1E−25) GeV at level of 90% C.L. - Confidence Level. In particular for n=-2, we obtained a limit three orders of magnitude more constrained than the previous analysis (P. Coloma, J. Lopez-Pavon, I. Martinez-Soler and H. Nunokawa, Decoherence in Neutrino Propagation Through Matter, and Bounds from IceCube/DeepCore , Eur. Phys. J. C78 (2018) 614), where we obtained that γ0⩽1,69E-23 GeV at level of 90%C.L.. Through the investigated scenarios in this thesis we also were able to analyze the decoherence effect in the solar oscillation parameter (Г12 ≠ 0), of possibles dissipative effects (Г33 = Г88 ≠ 0) and the possibility of the oscillation phase be complex and it possibles consequences in the usual neutrino oscillation.
Estudo teórico de propriedades espectroscópicas de bases nitrogenadas e derivados de vitamina A em solução
(Universidade Federal de Goiás, 2012-03-23) Oliveira, Guilherme Colherinhas de; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Fonseca , Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Moreno, Roberto Rivelino de Melo; Stassen, Hubert Karl; Maia, Lauro June Queiroz; Osório, Francisco Aparecido Pinto
In this work we present a theoretical study for the optical absorption spectrum UV-VIS and nuclear magnetic resonance (NMR) parameters of molecules that forming the structure of the deoxyribonucleic acid (DNA): adenine, guanine, thymine and cytosine in aqueous solution and of aldehydes and carboxylic acids derivatives of vitamin A in solution of chloroform, acetonitrile, methanol and water. The Solvent effects are treated using a sequential methodology that combines Monte Carlo simulation and quantum mechanics calculations (S-MC / MQ). Effects of polarization of the reference molecules by the solvent are obtained iteratively assuring the convergence of the dipole moment in solution, with the atoms of the solvent molecules modeled by point charges. The results show that the polarization effect can give marked increases for the dipole moments of the reference molecules, especially in water, as compared with the results of gas phase. TD-DFT calculations for the vertical electronic transitions were performed with hybrid functionalities: B3LYP, PBE1PBE and BHandHLYP; and with long-range corrected functionals: CAM-B3LYP and LC-wPBE. For the isotropic magnetic shielding constants, GIAO-B3LYP results were obtained with several basis set functions: 6-311 ++ G (2d, 2p), AUG-cc-pVTZ, pcS-2, pcS-3 and AUG-pcS -2. The results obtained show the optical absorption spectrum variations between 6 and 28 nm for the nucleotide bases and between 13 and 80 nm for the derivatives of vitamin A with the functional type, whereas that for the NMR parameters of carbon atoms variations between 3 and 10 ppm with the choice of the basis set functions. However, the inclusion of the solvent polarization effects provides a reliable description for these electronic properties in solution, in comparison with available experimental results. The classical simulations were performed with the DICE program and the quantum calculations with the GAUSSIAN03 / 09 program.
Construção, caracterização e otimização da magnetohipertermia de nanocarreadores multifuncionais fluorescentes: a importância da relaxação coletiva na geração de calor
(Universidade Federal de Goiás, 2018-02-22) Zufelato, Nícholas; Bakuzis, Andris Figueiroa; http://lattes.cnpq.br/3477269475651042; Bakuzis, Andris Figueiroa; Nunes, Wallace de Castro; Silva, Sebastião William da; Pelegrini, Fernando; Bufaiçal, Leandro Felix de Sousa
In this work, we developed a multifunctional nanocarrier that has diagnostics and therapeutic applications in oncology, and evaluated the magnetothermal efficiency (SLP) properties in a comparative manner with respect to magnetic fluids. The nanocarrier consists of Mn-ferrite magnetic nanoparticles, a near-infrared fluorescent molecule IR-780, that are surface-coated with albumin proteins (BSA). The samples were characterized by dynamic light scattering (DLS), electron microscopy (TEM and MEV-FEG), vibrating sample magnetometer (VSM), fluorescence molecular tomography (FMT). FMT data proved the coupling of IR-780 to the protein allowing the fabrication of a magnetofluorescent nanostructure. Magnetic hyperthermia data as function of field amplitude (60-200 Oe) and frequency (170-990 kHz) were obtained for all samples containing the same magnetic particle volume fraction in the liquid carrier, but with distinct agregate sizes. The sizes were controlled by tuning the ionic force, and monitored experimentally using DLS. Magnetization curves revealed a (quasi-static) superparamagneticlike behavior, and was used to extract the particle concentration. The hyperthermia efficiency SLP of the magnetic fluids decreased increasing the hidrodynamic diameter. On the contrary, the nanocarrier showed a maximum of SLP, that can be optimized for hyperthermia and is more efficient than the ferrofluid. SLP data as function of frequency revealed a relaxation time of the order of 10-7 s and an equilibrium susceptibility lower than the Langevin value. A theoretical analysis of SLP at the linear responde regime was developed taking into account the dipolar interaction of nanoparticles organized in distinct arrangements. In magnetic fluids we considered a linear chain using the longitudinal configuration (anisotropy axis aligned), while for the nanocarriers we considered spherical agregates where the anisotropy axis of the nanoparticles are arranged randomly. The theoretical analysis indicate that the relaxation time cannot be explained by brownian relaxation or the Néel relaxation of single particle (even considering the dipolar effect). But instead, a mechanism of collective relaxation, mediated by dipolar interaction, is responsible for heat generation. It also indicates that only a fraction of agregates in the colloid is responsible for heating. In addition, the theoretical model revealed the existence of a transition from single particle relaxation to collective relaxation only if the dipolar interaction for the aggregate is higher than a critical value, which depends on material parameters, as for instance anisotropy field and saturation magnetization. Indeed, the model indicates that collective states are more easily achieved on soft magnets, and therefore suggests enhanced magnetothermal properties for this kind of materials.
Estudo das propriedades estruturais e óticas de compostos aluminoboratos e aluminogermanatos puros e dopados com íons terras-raras
(Universidade Federal de Goiás, 2017-04-12) Faria Filho, Fausto de Melo; Maia, Lauro June Queiroz; http://lattes.cnpq.br/9454054374479016; Maia, Lauro June Queiroz; Gonçalves, Pablo José; Santana, Ricardo Costa de; Gonçalves, Rogéria Rocha; Souza, Seila Rojas de
The objective of this thesis is study aluminogermanate and aluminoborate compounds containing lanthanide ions for photonic applications, especially light emitting diodes, as phosphors. Samples were prepared by sol-gel and polymeric precursor method (Pechini method). It was studied pure and doped Al6Ge2O13 with 1 mol% Eu3+ or Er3+ , heat treated at 1000 °C; 1 mol% Eu3+ doped xAl2O3+(1-x)B2O3, for x values: 0.33; 0.50; 0.60; 0.66; 0.75 and 0.80 under heat treatments at 800, 900 or 1000 °C; and the Al4B2O9 phase with xNd3+/ yYb3+, where x, y = 1, 0; 1, 1; 1, 2; 1, 4; 1, 8; 0, 1; 2, 1; 4, 1 and 8, 1, heat treated at 900 °C. The powders samples were characterized by X-ray diffraction, infrared vibrational spectroscopy, thermal analysis, and transmission electron microscopy. Diffuse reflectance spectra and photoluminescence emissions were collected under excitation at 394 nm for Eu3+ doped samples, at 378 and 977 nm for Er3+ doped samples, at 804 nm for Nd3+/Yb3+ doped samples and at 365 nm for pure samples. The Er3+ or Eu3+ doped aluminogermanate sample presented the Al6Ge2O13 crystalline phase identified by JCPDS card number 71-1061 after annealings at high temperatures. Absorption spectra in the infrared region showed Al-O-Ge and Al-O type bonds. The Eu3+ doped Al6Ge2O13 samples when excited at 394 nm showed red emission and the spectra analysis lead us to conclude that the lanthanides were located in a homogeneous environment with low symmetry. The Er3+ doped Al6Ge2O13 sample showed emission band in the infrared region with full width at half maximum of around 48 nm when excited at 977 nm. The band gap values were determined being between 4.19 and 4.30 eV. The Eu3+ doped xAl2O3+(1-x)B2O3 compositions presented the crystalline phase Al4B2O9 identified by JCPDS card number 29-0010. AlO6, AlO4, BO4 and BO3 groups were identified by FTIR technique. For these compositions, the emission spectra in the visible region showed a homogeneous environment with low symmetry. The Eu3+ doped 0.66Al2O3+0.34B2O3 sample possess the highest photoluminescence emission, after heat treatments at 900 °C . The lifetime of the Eu3+ 5D0 excited level were between 1.4 and 2.1 ms, depending on the B2O3 concentration and annealing temperature. The optical band gap was also determined having values between 3.72 and 4.42 eV. The Nd3+/Yb3+ doped Al4B2O9 samples present an efficient energy transfer between lanthanide ions and the best relative concentration was 1Nd3+ / 2Yb3+. The decay time of the emission at 1080 nm (975 nm) as function the Nd3+ concentration shows a maximum value around 120 μs at concentration of 4 mol% (around 200 μs for 2 mol%). On the other hand, changing the Yb3+concentration, the maximum decay time for emission at 1080 nm (975 nm) was around 100 μs (175 μs) for 1 mol% of Yb3+. In short, the materials studied are excellent candidates for application as luminophores in various technologies, such as LED´s and displays.

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