# Doutorado em Física (IF)

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Item Anisotropia magnética em filmes epitaxiais Fe/Mn, Fe/Mn/Fe e Fe/Mn/Co(Universidade Federal de Goiás, 2013-06-07) Pessoa, Márcio Solino; Pelegrini, Fernando; http://lattes.cnpq.br/0159280600583768; Pelegrini, Fernando; Silva, Edson Corrêa da; Saitovitch, Elisa Maria Baggio; Franco Júnior, Adolfo; Rabelo, José Nicodemos TeixeiraMostrar mais This work reports the study of magnetic anisotropy of Fe/Mn bilayers, and Fe/Mn/Fe and Fe/Mn/Co trilayers, grown by molecular beam epitaxy onto monocrystalline MgO(001) substrates. Samples were produced with the Fe layer grown at a temperature of 175 ° C, with a thickness of 5 or 10 nm, the Co layer grown at 50 ° C, with a thickness of 2 or 5 nm, and the Mn layer grown at temperatures of 50 ° C, 150 ° C or 175 ° C, with thicknesses in the range from 0.80 to 2.20 nm. The angular variations of the in-plane absorption field, at Q-band (33.9 Ghz) microwave frequency, reveal the presence of a large four-fold magnetic anisotropy in all studied films. In samples with thicker Mn layers, two uniform resonance modes of bcc-Fe and bcc-Co layers are excited by the microwave field. The angular variations of the in-plane absorption field reveal for both layers the presence of fourth order cubic magnetic anisotropy. Films with the Mn layer thickness exceeding 1.16 nm exhibits, however, only a single absorption mode due to the overlapping of Fe-bcc and Co-bcc uniform resonance modes. Experiments at X-band (9.4 GHz) microwave frequency reveal the excitation of non-aligned and non-resonant modes, suggesting, for samples with the Mn layer grown at low temperature, a non-collinear coupling between the magnetic layers in the presence of low-intensity magnetic fields. Four-fold magnetic anisotropy constants in the range from 3.0 x 105 to 4.8 x 105 erg/cm3 for the Fe layer, and from 2.0 x 105 to 6.4 x 105 erg/cm3, for the Co layer, are given by the experiments. The magnetic parameters deduced from the in-plane measurements at Q-band microwave frequency are used to fit the in-plane and out-of-plane angular variations of resonance fields at X-band frequency.Mostrar mais Item Aspectos de modelos eletrônicos bidimensionais fortemente correlacionados: aplicações em cupratos supercondutores(Universidade Federal de Goiás, 2016-06-06) Carvalho, Vanuildo Silva de; SIlva, Hermann Freire Ferreira Lima e; http://lattes.cnpq.br/7198902316435183; Silva, Hermann Freire Ferreira Lima e; Oliveira, Luiz Nunes de; Miranda, Eduardo; Rabelo, Jose Nicodemos Teixeira; Braghin, Fabio LuisMostrar mais We investigate here the low-energy properties of two strongly correlated electronic models in two spatial dimensions. The first one consists in a version of the Hubbard model in which are considered just the degrees of freedom of the system in the neighborhood of the so-called hot spots, which are defined as the intersection of the Fermi surface of the model with the antiferromagnetic zone. Initially, we set our theory up by linearizing the dispersion model in hot spots and consider all the interacting processes between these regions that conserve momentum within a reciprocal-lattice wave vector. In order to access the physics of the model, we then turn to the renormalization group method of quantum field theory and derive the flow equations for the couplings in the two-loop approximation. As a result, we obtain that the Fermi surface is strongly renormalized in hot spots as the renormalized couplings flow to a non-trivial fixed point in the low-energy limit. Then we suggest that this system can be viewed as an example of a non-Fermi liquid in two spatial dimensions, due to the lack of well defined quasiparticle fermionic excitations in the region close to hot spots. Moreover, we solve the Callan-Symanzik equation for the oneparticle Green function up to two-loop order, calculate the density of states in the hot spots, and derive the renormalization group equations for the order parameters of the potential instabilities which may eventually occur in the system at lower energies. We verify that the system can be characterized, in this regime, in terms of an emergent pseudospin symmetry [SU(2)]4, which leads to the appearance of entangled orders in the region close to the non-trivial fixed point of the model. We also show that the fermionic excitations in the adjacent regions to the hot spots get a gap in both charge a spin excitation spectra. Because of this, we argue that the Fermi surface of the model can be reconstructed, leading therefore to the formation of either Fermi arcs or electronic pockets. The second model analyzed in this thesis was the three-band Emery model, which describes all the interacting processes between fermionic excitations localized in both copper (Cu) and oxygen (O) orbitals in the CuO2 unit cell. By making use of a Hubbard-Stratonovich transformation, we introduce two order parameters in the system: one for the so-called ΘII-loop-current order, which violates Z2 time-reversal symmetry, and another one for the entangled phase with dx 2 -y 2 symmetry involving the singlet superconducting instability and the quadrupole density wave order, whose wave vector points in the direction of the Brillouin zone diagonal. Minimizing the free energy of the model, we derive the self-consistent mean-field equations for these order parameters. The solution of these equations for the zero temperature regime shows that the two phases compete with themselves for the same region of the phase space and, consequently, the system tends not to display coexistence between them. We argue that this effect could be the main reason for the fact that the quadrupole density wave order has never been observed in experiments performed on the cuprate superconductors. Next, we analyze the competition between the ΘII-loop-current order, which is experimentally observed, and charge order with dx 2 -y 2 symmetry and wave vectors in the direction of the main axes of the Brillouin zone. As a result, we obtain that the system only exhibits coexistence between the ΘII-loop-current phase and the bidirectional charge order. Due to the existence of a pseudospin symmetry in this model, we also confirm that the ΘII-loop-current phase coexists with the bidirectional pair density wave order. Finally, we discuss the implications of these results for the pseudogap phase of the cuprate superconductors, which appears in the underdoped regime in these systems.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 Avaliação experimental e teórica da hipertermia magnética de magnetolipossomos para tratamento oncológico(Universidade Federal de Goiás, 2016-08-17) Silva, Anderson Costa da; Bakuzis, Andris Fisgueiroa; http://lattes.cnpq.br/3477269475651042; Bakuzis, Andris Figueiroa; Miotto, Ronei; Silva, Sebastião William da; Bufaiçal, Leandro Felix; Pelegrini, FernandoMostrar mais In this work we investigated the magnetothermal efficacy of two nanocarriers, magnetic fluids (MF) and magnetoliposomes (ML), with potential for oncology therapy. Ferrofluids based on manganese ferrite nanoparticles, surface coated with citric acid, were synthesized. Magnetoliposomes, vesicles containing magnetic nanoparticles inside, were prepared by the extrusion method. X-ray diffraction corfimed the spinel structure, while transmission electron microscopy revealed spherical nanoparticles with a lognormal size distribution and mean diameter of (11,1 ± 3,5) nm. Magnetization curves, at quasi-static conditions revealed particles at the superparamagnetic regime. A reduction in the saturation magnetization in comparison with bulk samples were explained by a nonmagnetic shell with thickness of 1.1 nm. The concentration and particle size distribution of the liposomes (mean diameter of 180 nm) were obtained from the nanoparticle tracking analysis (NTA). The combination of magnetometry and NTA data revealed an encapsulation particle volume fraction in the range of 0.26 to 0.83% for the samples. Magnetic birefringence data showed a higher fraction of aggregates in ML in comparison to MF. Magnetic hyperthermia experiments were perfomed at distinct frequencies (111 -632 kHz) and field amplitudes (up to 250 Oe) for distinct ML and MF samples. In general, we found a reduction of magnetothermal efficacy for magnetoliposomes when compared to MF. although the effect is less evident at lower frequencies (<170 kHz). The explanation was obtained through a new theoretical model that, not only takes into account the effect of dipolar interaction in the magnetic anisotropy, but also the reduction of susceptibility due to blocked nanoparticles. This contribution was shown to be strongly dependent upon field frequency, amplitude and aggregates in the suspension.Mostrar mais Item Cálculos de (hiper)polarizabilidades dinâmicas das moléculas de ozônio, dióxido de enxofre, óxido nitroso e dióxido de carbono incluindo correções vibracionais e efeitos de correlação eletrônica(Universidade Federal de Goiás, 2013-11-08) Naves, Emílio Santiago; Castro, Marcos Antônio de; http://lattes.cnpq.br/3500875789893244; Fileti, Thaciana Valentina Malaspina Fileti; http://lattes.cnpq.br/2600060786895700; Silva Filho, Demétrio Antônio da; http://lattes.cnpq.br/8032106763743620; Georg, Herbert de Castro; http://lattes.cnpq.br/8026419467214372; Braghin, Fabio Luis; http://lattes.cnpq.br/9375085677737347Mostrar mais This work presents results for the dynamic (hyper)polarizabilities of ozone, sulfur dioxide, nitrous oxide and carbon dioxide molecules, with inclusion of vibrational corrections. The electronic contributions for the properties of interest were computed analytically at the single and double coupled cluster level through response theory. Ozone and sulfur dioxide were studied separately. For both systems, contributions of connected triple excitations were also estimated by the multiplicative correction scheme. The vibrational corrections were calculated by the perturbation theoretical method (PT). The zero-point vibrational average correction, calculated only for ozone and sulfur dioxide, proved to be small. Results also show that the pure vibrational correction is relevant for the following nonlinear optical processes: dc-Pockels effect, intensity dependent refractive index, and dc-Kerr effect. For the ozone molecule the dc-second harmonic generation effect also had a significant pure vibrational correction. In addition, pure vibrational correction was calculated according to a variational methodology proposed by our research group (VAR) for the four systems, and the results were compared with the corresponding PT results. A comparison between PT and VAR results shows that ozone is the system most sensitive to the method, while sulfur dioxide and carbon dioxide are the most well behaved.Mostrar mais Item Caracterizações óptica e elétrica de cristais de Bi2TeO5 crescidos por um método de duplo cadinho(Universidade Federal de Goiás, 2015-01-22) Fabris, Zanine Vargas; Carvalho, Jesiel Freitas; http://lattes.cnpq.br/5841291496427516; Carvalho, Jesiel Freitas; Baldochi, Sonia Licia; Santo, Ana Maria do Espírito; Lariucci, Carlito; Gonçalves, Pablo JoséMostrar mais Bismuth tellurite, Bi2TeO5, here labeled BTeO has a lot of properties like improper ferroelectricity, photochromic, photorefractive, with two optical axes large optical window and another interesting optical and electrical properties, as recently we discovered, photovoltaic effect. BTeO single crystal growth and processing has two inherent difficulties, high vapor pressure of tellurium oxide close to bismuth tellurite melting point and BTeO cleavage plane parallel to (100) plane. So, BTeO factory good sample for material characterization require singular precautions and depends on researcher experience invariably. Present work is dedicated to detailed study of BTeO single crystals growth parameters in a modified Czochralski method with unpublished concept double crucible system. In our case, we used oxides mix on external crucible with volatile oxide bigger quantity related to internal crucible to create a supersaturated atmosphere used to control crystal growth liquid phase stoichiometry reducing tellurium oxide evaporation. We also highlighted important details about good quality samples production, like crystal cut and polish enclosed in acrylic resin to avoid cleavages during this processes. Finally, we characterized BTeO by optical spectroscopy (optical absorption, Raman scattering and luminescence) and electrical properties (conductivity, photoconductivity and impedance spectroscopy). We measured BTeO photorefractive properties with 633 nm wavelength for the first time and results suggested that material could be photovoltaic, hypothesis tested and confirmed in the present work.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 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 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 Efeito da interação dipolar magnética na eficiência de aquecimento de nanopartículas: Implicações para magnetohipertermia(Universidade Federal de Goiás, 2014-12-09) Branquinho, Luis Cesar; Bakuzis, Andris Figueiroa; http://lattes.cnpq.br/3477269475651042; Bakuzis, Andris Figueiroa; Pelegrini, Fernando; Franco Junior, Adolfo; Morais, Paulo Cesar de; Landi, Gabriel TeixeiraMostrar mais Magnetic nanoparticles can generate heat when submitted to alternating magnetic fields of adequate amplitude and frequency. This phenomenon is named magnetic hyperthermia and has several therapeutic applications, as for example, in the treatment of cancer. In general, the theoretical models used to describe this neglect the effect of interparticle interaction. In this thesis we investigate the effect of magnetic dipolar interaction in the magnetothermal efficiency (named specific loss power – SLP) of bicompatible magnetic nanoparticles. Firstly, we develop a chain of magnetic particles model, where we prove that the interaction leads to a contribution to the uniaxial anisotropy. This term in the free energy density allowed us to extract from the electron magnetic resonance technique (EMR) information about the mean chain size in the colloid. Further, this additional magnetic nanoparticle anisotropy term was used to develop an analytical theoretical model that takes into account the effect of the dipolar interaction between nanoparticles to SLP, considering the case where the magnetization responds linearly to the field (Linear Response Theory). Our calculations indicate that depending on the particle parameters, specially the anisotropy, the effect can be to enhance or decrease the heat generation. Moreover, we showed that increasing the chain size (number of particles in the chain) the optimal particle size for hyperthermia can decrease up to 30% in comparison with non-interacting particles. This result has several clinical implications, which allowed us to suggest some strategies for improving the therapeutic efficacy. In order to investigate experimentally the effect, two magnetic fluids, one containing spherical nanoparticles based on manganese ferrite (MnF-citrate) in the superparamagnetic regime, and another commercial one (BNF-starch) magnetite-based with a shape of a parallellepiped and blocked, were selected and deeply characterized. We found a decrease of SLP increasing the chain size for the MnF sample, while for BNF-starch no effect was found at the same experimental conditions. The decrease of SLP in the MnF sample, within the particle concentration range, was explained considering in the model not only the effect in the anisotropy but also by an increase in the damping factor parameter, a term correlated to spin-phonon interaction. Data obtained using EMR and Monte Carlo simulations corroborate our hypothesis. The absence of concentration effect for the BNF sample was attributed to the higher anisotropy value and to the probable influence of brownian relaxation. In addition, the same chain model was used to investigate the behavior of blocked nanoparticles of Stoner-Wohlfarth type. In this case, we demonstrate that the chain formation increases the magnetic hyperthermia, as found in magnetosomes. Finally, we showed that a fluctuation of the dipolar interaction field between particles in the chain, which does not destroy the symmetry of this term, shows a Vogel-Fulcher behaviour in the weak coupling regime.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 Estudo da oscilação de neutrinos muônicos usando dados atmosféricos e de acelerador nos experimentos MINOS e MINOS+(Universidade Federal de Goiás, 2015-05-07) Medeiros, Michelle Mesquita de; Gomes, Ricardo Avelino; http://lattes.cnpq.br/6538341799051577; Gomes, Ricardo Avelino; Peres, Orlando Luis Goulart; Maciel, Arthur Kos Antunes; Leao, Salviano de Araujo; Celeri, Lucas ChibebeMostrar mais The MINOS (Main Injector Neutrino Oscillation Search) and MINOS+ experiments were designed to study neutrino oscillations using a muon neutrino beam which is detected in two different locations, in the Near Detector and in the Far Detector. The distance between the detectors allows the beam neutrinos to oscillate to a different flavor. Therefore, a disappearance of the muon neutrinos from the beam is observed in the Far Detector. The Far Detector has a special apparatus which makes possible the selection of atmospheric neutrinos and antineutrinos. These come from interactions of cosmic rays with the Earth’s atmosphere. Both detectors have a magnetic field, allowing the distiction between neutrinos and antineutrinos interactions. This thesis presents the first combined analysis of data from the MINOS and MINOS+ experiments. We have analyzed the combined neutrino energy spectrum from the complete MINOS beam data and the first, more energetic, MINOS+ beam data. The disappearance of the muon neutrinos was observed and the data has shown to be congruent with the oscillation model. Beyond that, we have measured the atmospheric oscillation parameters of the beam and atmospheric neutrinos and antineutrinos from MINOS combined with the atmospheric neutrinos and antineutrinos from MINOS+. Assuming the same oscillation parameters for both neutrinos and antineutrinos, the best fit is obtained for inverted hierarchy and lower octant with m2 32 = 2:37 103 eV2 and sin2 23 = 0:43, and the limits m2 32 = [2,29 - 2,49] 103 eV2 (68%) and sin2 23 = 0.36 - 0.66 (90%). These results are the most precise measurement of the neutrinos mass splitting using muon neutrino disappearance data only.Mostrar mais Item Estudo das interações da miltefosina com membranas de L. (Leishmania) amazonensis e macrófagos peritoneais(Universidade Federal de Goiás, 2016-02-15) Fernandes, Kelly de Souza; Dorta, Miriam Cristina Leandro; ttp://lattes.cnpq.br/3933395097851681; Alonso, Antonio; http://lattes.cnpq.br/5013069863616789; Alonso, Antonio; Dorta, Miriam Cristina Leandro; Izumi, Erika; Souza, Paulo Eduardo Narcizo de; Oliveira, Valéria deMostrar mais Miltefosine (MT) is a alkylphospholipid originally developed for treatment of breast cancer and other solid tumors. It is currently used in the treatment of leishmaniasis, an infectious parasitic disease caused by protozoa of the genus Leishmania, being the first oral drug adopted for this purpose. However, its mechanism of action remains unclear. Electron paramagnetic resonance (EPR) spectroscopy of a spin-labeled lipid (5-DOXIL stearate) and a thiol-specific spin label (4-maleimido-TEMPO) in the membrane of axenic amastigotes of L.(Leishmania) amazonensis and peritoneal macrophages from Balb/c mice showed that MT causes significant increase in membrane dynamics at similar concentrations that inhibit parasite growth or are cytotoxic to macrophage. Although these alterations can be detected using a spin-labeled lipid, our experimental results indicated that MT interacts predominantly with the protein component of the membrane. Using a method for the rapid incorporation of MT into the membrane, these effects were measured immediately after treatment. Cytotoxicity, estimated via microscopic counting of living and dead cells, indicated ~80% parasites and macrophages death at the concentration of MT at which EPR spectroscopy detected a significant change in membrane dynamics. Cell viability, analyzed using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide tetrazolium) reduction assay, showed that 50% inhibitory concentration (IC50) of MT depends on the cell concentration used in the assay. This dependence was analyzed using a theoretical equation involving biophysical parameters such as the partition coefficient of watermembrane and MT concentrations on the membrane and in the aqueous medium. The data showed that cells more sensitive to MT are respectively: erythrocytes, Leishmania promastigotes and Leishmania amastigotes and macrophage. The IC50 value of MT for 4 x 107 parasites/mL was 24,35 M. For the same cell concentration, a significant alteration was detected in the membrane lipid fluidity of parasites to 15 M of MT. The EPR spectra of spinlabeled membrane-bound proteins were consistent with more expanded and solvent exposed protein conformations, suggesting a detergent-like action, with a possible formation of micelle-like structures around polypeptide chains.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 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 Estudo do fenômeno de exchange bias em bicamadas NiFe/IrMn e tricamadas NiFe/IrMn/Co(Universidade Federal de Goiás, 2013-06-27) Sousa, Marcos Antonio de; Pelegrini, Fernando; http://lattes.cnpq.br/0159280600583768; Pelegrini, Fernando; Geshev, Julian Penkov; Feitosa, Carlos Chesman de Araújo; Bakuzis, Andris Figueiroa; Castro, Marcos Antônio deMostrar mais This work reports the study of the phenomenon of exchange bias in NiFe/IrMn bilayers and NiFe/IrMn/Co trilayers. In the NiFe/IrMn bilayers, ferromagnetic resonance experiments at X and Q bands microwave frequencies reveal that spin wave and NiFe resonance modes are excited by the oscillating microwave field. Angular variations of the absorption fields in the plane of the films for both resonance modes shows the effect of the unidirectional anisotropy field, whose intensity is twice larger for the spin wave mode, due to an additional contribution of an unidirectional surface anisotropy. The experiments also indicate the presence of a uniaxial anisotropy of the NiFe layer, apparently dependent on the applied magnetic field. The magnetic parameters of both resonance modes were deduced considering a generalized phenomenological model which also includes the contribution of a rotatable anisotropy. In the NiFe/IrMn/Co trilayers, the angular variations of the resonance field in the plane of the films reveal the effect of the unidirectional anisotropy field for both independent resonance modes of NiFe and Co layers. The ferromagnetic resonance results combined with magnetometry data show that the exchange bias phenomenon at the NiFe/IrMn interface influences the same phenomenon at the IrMn/Co interface, and that this effect must be mediated by a spiral structure of spins across the IrMn antiferromagnetic layer. For both systems studied, the values of the exchange bias field deduced from the ferromagnetic resonance experiments are consistent with the values given by magnetization measurements.Mostrar mais Item Estudo e geração de estados não clássicos em nanocircuitos: propriedades e aplicações(Universidade Federal de Goiás, 2012) Valverde, Clodoaldo; Avelar, Ardiley Torres; http://lattes.cnpq.br/5732286631137637; Baseia, Basilio; http://lattes.cnpq.br/5804506385505435Mostrar mais In this work we used an arrangement consisting of Cooper pairs (Cooper Pair Box, CPB) interacting with a nanomechanical Resonator (NR) for various studies: to produce controlable holes in the statistical distribution of excitations of the NR, for resonant and non-resonant cases; to study the evolution of the entropy and the inversion of excitations, including losses in the CPB; and to study the evolution of the Wigner function under the infuence of a reservoir. We have obtained the exact solution of the master equation describing the non-degenerate parametric amplifier interacting with a generalized model of linear phase sensitive reservoir, having the form of the equation equivalent to that of the Fokker-Planck propagator for the Wigner function. We have calculated the Wigner function describing the temporal evolution of a state initially in a superposition of two coherent states, a kind of "Schr?odinger cat", and finally, we have also studied the temporal evolution of the negativity of this function, one of the indicators of nonclassicality of vibrational states of the NR.Mostrar mais Item Estudo teórico de (hiper) polarizabilidades de cristais orgânicos(Universidade Federal de Goiás, 2016-10-27) Santos, Orlei Luiz dos; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Gargano, Ricardo; Martins, João Batista Lopes; Silva, Ladir Cândido da; Souza, Márcio Adriano RodriguesMostrar mais This work presents the results for the dipole moment and the static (hyper)polarizabilities of urea, thiourea and 3-methyl-4-nitropyridine-1-oxyde crystals under the influence of the crystalline environment. We have used the approach of Hartree-Fock together with Moller- Plesset theory of second order to include the effects of electron correlation in the electrical properties of the compounds. These properties were calculated using the numerical method of finite field. The polarization effects were included using an iterative electrostatic process where the neighboring molecules to the reference compound are treated as point charges. All compounds were found to be very sensitive to environmental effects, especially with regard to the dipole moment and the first hyperpolarizability. The linear polarizability presented values embedded with insignificant variations in relation to isolated results. However, in all of the compounds, it showed an additive behavior. Additionally, it was possible to estimate values for the macroscopic electrical properties and verify a reasonable agreement with other theoretical and/or experimental results.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

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