# Doutorado em Física (IF)

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Item 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 LuisMostrar mais 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.Mostrar mais Item 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 EternoMostrar mais 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.Mostrar mais Item 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 daMostrar mais 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.Mostrar mais Item 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 CastroMostrar mais 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.Mostrar mais Item 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 PessoaMostrar mais 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.Mostrar mais Item 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, AntonioMostrar mais 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: PhotodynamicMostrar mais Item 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 SoaresMostrar mais 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.Mostrar mais Item 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 SoaresMostrar mais 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.Mostrar mais Item 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 AlvesMostrar mais 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.Mostrar mais Item 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 deMostrar mais 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.Mostrar mais Item 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 AvelinoMostrar mais 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.Mostrar mais Item 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 PintoMostrar mais 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.Mostrar mais Item 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 SousaMostrar mais 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.Mostrar mais Item 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 deMostrar mais 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.Mostrar mais Item Estudo de soluções localizadas na equação não linear de Schrödinger logarítmica, saturada e com efeitos de altas ordens(Universidade Federal de Goiás, 2018-06-07) Alves, Luciano Calaça; Avelar, Ardiley Torres; http://lattes.cnpq.br/5732286631137637; Cardoso, Wesley Bueno; http://lattes.cnpq.br/6845416823133684; Bazeia Filho, Dionisio; Valverde, Clodoaldo; Santana, Ricardo Costa de; Maia, Lauro June QueirozMostrar mais This work presents the study of solitary wave solutions, known as solitons, in non-linear and non- homogeneous media using non-linear Schrödinger equations. Three cases are studied: first considering a logarithmic nonlinear term; second with saturation effect and finally including effects of high orders (Raman scattering). Solutions are modulated by three different types of potential. First, linear in the spatial and oscillatory coordinate in the temporal coordinate. The second, quadratic in the spatial and oscillatory in the temporal coordinates. Finally, it is also modulated using a mixed potential, which is the junction of the two potentials presented above. After including inomogeneities in linear and nonlinear coefficients, the similarity transformation technique is used to convert the non-linear, non-autonomous equation into an autonomous one that will be solved analytically. This field of study has potential applications in crystals, optical fibers and in Bose- Einstein condensates, also serving to understand the fundamentals related to this state of matter. The stability of the solutions are checked by numerical simulations.Mostrar mais Item Avaliação da dependência com a pressão de propriedades estruturais de compostos orgânicos de interesse farmacêutico(Universidade Federal de Goiás, 2018-05-07) Castro, Rosane de Paula; Sabino, José Ricardo; http://lattes.cnpq.br/9101677399031185; Pinheiro, Carlos Basílio; Santos Júnior, Sauli dos; Bufaiçal, Leandro Félix de Sousa; Fonseca, Tertius Lima daMostrar mais This thesis presents the structure determination using single crystal x-ray crystallography of four drug candidates under ambient conditions of temperature and pressure, as well as submitted to high pressure. The crystallographic analysis of this type of compound allows to obtain the three-dimensional structure in an unambiguous way. This information is useful for the development process of new drugs in order to achieve the planned properties, such as the study of combinations of the drug with the excipients to be used to guarantee the rate of expected release of the drug in the human body and the optimization of interaction between the drug and the target. Furthermore during the process of drug manufacturing in the pharmaceutical industry polymorphic phases may arise due to the application of pressure, which occurs during grinding and in the preparation of tablets, which may alter the bioavailability, solubility and stability of the medicament. Thus, identifying the conditions under which such modifications may occur guarantees the reliability of the final product. In this sense, the crystallization and crystallographic analysis of drug candidates developed by the Laboratório de Avaliação e Síntese de Substâncias Bioativas (LASSBio) of the Universidade Federal do Rio de Janeiro (UFRJ) was carried out. The compounds analyzed were: LASSBio-1773 and LASSBio-1774, which have hypoglycemic activity, LASSBio-1606, with anti-inflammatory properties, and LASSBio-1735, which has been shown to be active against several types of cancer. For the compounds LASSBio-1774 and LASSBio-1606 X-ray diffraction at high pressures was also performed with Diamond Anvil Cell (DAC), determining their unit cells and analyzing the effects of pressure on the crystalline arrangement. In both compounds reversible phase transitions were observed. The analysis of the structural changes for LASSBio-1774 due to pressure was performed with the aid of strain tensors.Mostrar mais Item Incerteza quântica local em transições de fase quânticas e uma generalização para sistemas multipartidos(Universidade Federal de Goiás, 2018-05-02) Carrijo, Thiago Mureebe; Céleri, Lucas Chibebe; http://lattes.cnpq.br/6630683190018665; Avelar, Ardiley Torres; http://lattes.cnpq.br/5732286631137637; Almeida, Agnaldo Rosa de; Avelar, Ardiley Torres; Valverde, Clodoaldo; Oliveira, Guilherme Colherinhas de; Cardoso, Wesley BuenoMostrar mais In this work, we have studied how local quantum uncertainty (LQU) and linear entropy behave in critical systems. Two models of spin 1/2 systems were investigated: XY and XY with triple interaction (XYT), both unidimensional. It was concluded that these measures and their derivatives locate the phase transitions of these systems and a justification was given for the difference of behavior between the LQU and the linear entropy in the region near the transition in the XY model. A measure of multipartite quantum correlations was also created according to a set of axiomatic criteria, which was tested in the family of Werner-GHZ quantum states, producing results in accordance with the expected result, according to the literature.Mostrar mais Item Observação da variação sazonal de múons múltiplos no NOvA Near Detector(Universidade Federal de Goiás, 2018-04-26) Tognini, Stefano Castro; Gomes, Ricardo Avelino; http://lattes.cnpq.br/6538341799051577; Gomes, Ricardo Avelino; Goodman, Maury Charles; Bolzam, Maurício José Alves; Braghin, Fábio Luis; Almeida, Norton Gomes deMostrar mais The interaction of a cosmic ray particle with an element of the atmosphere results in a cascade of particles, known as extensive air showers, which can be divided into three main branches, known as the hadronic, the electromagnetic, and the muonic component. As for the latter, since muons can reach high depths underground, they are generally used to study cosmic rays at different underground depths. The dynamics of extensive air showers is directly connected to the density of the atmosphere, as it defines the probability of particles to decay or interact. As muons are mainly produced from the decay of pions and kaons, and a warmer atmosphere results in higher number of meson decays, such particles are prone to suffer a sea- sonality effect that is directly correlated to the yearly seasonal variations of the atmosphere, an effect that has been verified by a large number of experiments over the past six decades. In 2015 the MINOS experiment presented an anti correlation between the effective temperature of the atmosphere and the seasonality of the muon flux for multiplicities higher than one (i.e. more than one muon track per cosmic ray event). Said anti correlation is not yet fully understood, counting with only a qualitative hypothesis as a probable mechanism. As such, the main goals of this study are to verify the MINOS anti correlation effect and extend the study to verify the seasonality of the effect as a function of different variables in order to improve the understanding of the phenomenon and possible corroborations with the known hypothesis. Two full years of the NOνA Near Detector, ranging from April 2015 to April 2017, were used as the dataset for the analysis. The anti correlation between the multiple muon flux and the effective temperature of the atmosphere is confirmed by the NOνA Near Detector, being in full agreement with the results presented by the MINOS Collaboration. The seasonal effect is also broken down by different variables: i) track separation, ii) zenith angle, iii) track angular separation, and iv) multiplicity. Different regions of these variables represent different energy ranges for the detected underground muons, their hadron parents or the primary particles that originated the cosmic ray shower, being a way to verify any particular dependency with energy. The results show that there are no clear trends in any of the studied variables, except for the multiplicity, in which the intensity of the seasonal variation increases for higher multiplicities.Mostrar mais Item Simulações entrópicas do Modelo de Baxter-Wu(Universidade Federal de Goiás, 2017-08-04) Jorge, Lucas Nunes; Caparica, Álvaro de Almeida; http://lattes.cnpq.br/4726638254587108; Sousa, José Ricardo de; Godoy, Maurício; Vale, Renato Pessoa; Silva, Hermann Freire Ferreira Lima eMostrar mais In this work, we used a refined entropy sampling technique based on the Wang- Landau method and finite-size scaling techniques to study variations of the Baxter-Wu model, namely: spin-$1/2$, spin-$1$, spin-$1$ with the crystal field interaction and was done a three-dimensional proposal for the model. It was also verified characteristics in the order parameter to be adopted in the simulations. The universality class and the critical temperature were calculated for the spin-$1/2$ case, and the results founded were in good agreement with the exact ones found in the literature. We sought to determine the kind of the phase transition that the model suffers for the spin-$1$ case, being carried out a detailed study for continuous and discontinuous phase transitions. The Baxter-Wu model with crystal field, $D$, had its phase diagram constructed, as well as the determination of the point at which discontinuous transitions finalizes. The critical exponent, $\nu$, was evaluated for several values of the crystal field, where we verified is variation along the critical line, with the existence of a peak, corroborating the existence of a multicritic behavior of the model. We also observed the existence of an anomaly in the specific heat, associated to the Schottky defect. This anomaly appears more clearly for values of $D \geq 1.990$. In the study of the order parameter, we verified that in the simulations one should not, when considering lattice sizes multiple of three, use the order parameter as the total magnetization of the lattice, but to consider the magnetization by sub-lattices. When working with sizes of lattices that are not multiples of three, it is not a problem to adopt the order parameter as the total magnetization of the lattice. A three-dimensional proposal was also made for the Baxter-Wu model, and its phase transition was characterized.Mostrar mais Item Variação da energia livre na hidratação de séries homólogas de poliol, glicina e peptídeos ANK usando modelos contínuo e discreto de solvente(Universidade Federal de Goiás, 2017-05-12) Abreu, Leonardo Martins de; Fileti, Eudes Eterno; http://lattes.cnpq.br/5294929829300325; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Fonseca, Tertius Lima da; Moreno, Roberto Rivelino de Melo; Fujimoto , Milton Massumi; Vale, Renato Pessoa; Silva, Ladir Cândido daMostrar mais Using continuum and discrete solvent description models, we have investigated the chain length dependence of hydration free energy of polyol, glycine and ANK peptides. In this work this property values were calculated using thermodynamics integration with classical molecular dynamics simulation of one solute molecule to around 1000 solvent molecules. In addition, hydration free energy of polyol, glycine and ANK peptides were also calculated using polarizable continuum model in combination with the universal solvation model. Dipole moment and linear polarizability of the three systems had been also calculate using the PCM method. Our MD results show that ΔG exhibit a linear pattern with the size of glycine and ANK chain as well as observed for organic compounds in literature. In opposition, polyol’s ΔG shows a nonlinear behavior with increasing chain length and for this group of molecules it were found that water solvating effects have an important role over the polyol’s electric properties. These results suggest that in the case of polyols not only variation of polarizability but also variations of dipole moment in going from vacuum to water can influence the behavior of the free energy of hydration. All DM and PCM calculations were performed using the GROMACS 4.5 and the GAUSSIAN09 programs, respectively.Mostrar mais

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