Programa de Pós-graduação em Física

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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 da
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.
Propriedades elétricas de cadeias de poliacetileno fluoretadas
(Universidade Federal de Goiás, 2015-08-02) Abreu, Leonardo Martins de; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Fonseca, Tertius Lima; Gargano, Ricardo; Braghin, Fábio Luis
Using Hartree-Fock (HF) and the second-order Møller-Plesset perturbation theory (MP2) methods with the 6-31G(d) basis set, we have investigated the chain length dependence of the dipole moment, linear polarizability, first and second hyperpolarizabilities of fluorinated polyacetylene chains (PFHA). Such properties were calculated using converged geometries obtained at the HF/6-31G(d) e MP2/6-31G(d) levels theory. The converged geometric parameters were obtained from equilibrium geometry of the oligomer with 40 carbon atoms. Our results show that the dipole moment and the first hyperpolarizability grow initially and exhibit a saturation pattern with the size of chain. In opposition, the linear polarizability and second hyperpolarizability present an increase with increasing chain length. It is found that the effects of electron correlation have an important role on the equilibrium geometry and on the electric properties. For the first hyperpolarizability, in particular, the asymptotic value including the electron correlation effects is 17 times larger than the uncorrelated one. These calculations were performed using the GAUSSIAN03, GAUSSIAN09 and Finito.f programs.
Estudo teórico de propriedades elétricas de derivados de retinal em solução
(Universidade Federal de Goiás, 2011-03-03) Adriano Júnior, Luizmar; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Fonseca, Tertius Lima da; Chaudhuri, Puspitapallab; Maia, Lauro June Queiroz
In this work we study the dipole moment, linear polarizability and first hiperpolarizability of 09cis, 11cis, 13cis and all-trans retinal derivatives in the gaseous phase and in different solvents. The solvent effects were modelled using the sequential Quantum Mechanics/Molecular Mechanics – S-QM/MM – methodology and the electric properties were calculated numerically with the finite field method. We use an average solvent electrostatic configuration – ASEC – to obtain the same statistical average with just one quantum mechanics calculation, instead of performing several quantum mechanics calculations for each one of the configurations of liquid. The second-order Møller–Plesset perturbation theory – MP2 – were used to describe the electronic structure. Our results show that the presence of the solvent increases the first hyperpolarizability of molecules of retinal [retinoic acid] by 17%-120% [5%-65%] when compared with corresponding gas phase results. It is found, in addition, that the dipole moment and the first hyperpolarizability are particularly affected by changes in the polarity and nature of solvent. A comparative analysis between cis and trans retinal derivatives shows that the isomerization effects have a marked influence on both the dipole moment and the average first hyperpolarizability.
Análise comparativa da eficiência fotodinâmica de fotossensibilizadores em sua forma base livre e formando complexados com zinco
(Universidade Federal de Goiás, 2014-04-09) Alonso, Lais; Gonçalves, Pablo José; http://lattes.cnpq.br/0515343409614452; Gonçalves, Pablo José; Borissevitch, Iouri; Bakuzis, Andris Figueiroa
Photodynamic therapy (PDT) is a technique that has been increasingly used in cancer treatment. It consists in introduce a photosensitizer (PS) in cancerous tissue and irradiate it with light in the visible range. Targeting a more effective treatment of PDT, currently there are several studies on the efficacy of these PS. In this work, we studied the photodynamic efficiency seven PS: meso-tetrametilpiridil, meso-tetrasulfonatofenil and carboxiftalocianinas with their base free or metallated with zinc atom in its center ring and protoporphyrin IX. Erythrocytes suspended in 2 to 10% hematocrit were treated with or without 25 μM of PS were exposed to light from a halogen lamp, and measured the time required to obtain 50 % hemolysis (T1/2). To examine whether the photodynamic efficiency is related to the affinity of PS by membrane, we performed measurements of the octanol/water partition coefficient (PO/W) of each PS. Our results indicated that the PS studied were very hydrophilic and showed a trend for greater photodynamic efficiency the PS with higher Log PO/W. To better understand the mechanism of action of the studied PS the degree of lipid peroxidation in erythrocyte membranes irradiated with PS was assessed by measuring the formation of malondialdehyde (MDA) and a correlation between the rate of peroxidation and hemolytic potential was found. The ability of PS to degrade proteins was assessed using bovine serum albumin (BSA), monitoring the fluorescent signal of this protein into solution and under irradiation in the presence of PS.
Instabilidade modulacional em equações não lineares de Schrödinger
(Universidade Federal de Goiás, 2015-10-16) Alves , Erivelton de Oliveira; Cardoso , Wesley Bueno; http://lattes.cnpq.br/6845416823133684; Avelar , Ardiley Torres; http://lattes.cnpq.br/5732286631137637; Avelar , Ardiley Torres; Cardoso , Wesley Bueno; Souza , Márcio Adriano Rodrigues; Bazeia Filho , Dionízio; Malbouisson , Jorge Mario Carvalho
In this work the influence of a saturable nonlinearity on the modulation instability (MI) in the contexts oppositely directed coupler and optical fibers in the presence of high-order effects are investigated. The instability gain is attained by using standard linear stability analysis. In particular, we study the combination of a saturable nonlinearity with self-steepening or intrapulse Raman scattering effects on MI for both normal and anomalous group velocity dispersion regimes. In the case of the directional couplers we investigated how the gain of modulational instability is affected by the saturation model and self-steepening or intrapulse Raman scattering effects. Our results show that instability gain exhibits significant changes due to the effects of saturable nonlinearity. When we analyze self-steepening effect, we show that its effective influence on the gain of the modulational instability depends on the algebraic sum of the parameters in each channel. Analyzing the intrapulse Raman scattering, we observe a symmetry break in the gain regions when the Raman scattering parameter with opposite signals in each channel is considered. Finally, in the context of optical fibers we show how the reduction of the Of the gain frequency of the IM, induced by saturation, can drastically limit the formation of soliton trains.
Éxcitons em semicondutores magnéticos diluídos
(Universidade Federal de Goiás, 2006-08-02) ALVES, Erivelton de Oliveira; Souza, Márcio Adriano Rodrigues; http://lattes.cnpq.br/2980610890056479
We investigate the resonant tunneling of electrons and holes in an asymmetric double quantum bit CdTe / CdMnTe in the presence of electric and magnetic fields applied along the growth direction. We show that in this case it is possible to achieve a condition of simultaneous resonant tunneling of electrons and holes with spin set, ie, a resonant tunneling of excitons polarized. Then we calculated the excitonic binding energy as a function of applied fields, showing the strong dependence of the binding energy with the tunneling of carriers. The electronic structure was calculated using the k ~ ~ p multiband Kane model. The eigenstates were obtained by solving numerically the equations ° C ~ the effective mass using the method of inverse power. The effects of lattice strain were treated by the Bir-Pikus model. The energy calculation of excitonic Dial-Up was conducted using the variational method. We consider the perfectly abrupt interfaces of the heterostructures, ie effects of enlargement of the interfaces were neglected.
Dinâmica populacional em sistemas atômicos de dois e três níveis de energia
(Universidade Federal de Goiás, 2017-08-10) Alves, Eyber Domingos; Almeida, Norton Gomes de; http://lattes.cnpq.br/3182841849332242; Oliveira, Guilherme Colherinhas de; Almeida, Agnaldo Rosa de
In this work a description of the interaction between electromagnetic radiation and matter will be made. Two and three-level atomic systems will be addressed, which in turn is in the (Lambda) configuration.We will use the Dicke states to calculate the transition probability between the energetic levels for a 2-level ensemble of atoms interacting with a circularly polarized field. We will deduce the master equation for a two-level atom interacting with a thermal reservoir, observing the effects of irreversible spontaneous decay and loss of coherence between quantum states. Finally, we will study the phenomenon of Electromagnetically Induced Transparency (EIT) and Dark states.
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 Queiroz
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.
Estudos da sinterização de Bi12TiO20 (BTO) visando obter cerâmicas transparentes
(Universidade Federal de Goiás, 2011-02-16) AMARAL, Thiago Martins; Carvalho, Jesiel Freitas; http://lattes.cnpq.br/5841291496427516
This work presents the systematic results of studies concerning the sintering of the Bi12TiO20 (BTO) aiming the production of transparent ceramic samples. All that because the BTO is a material that has great scientific and technologic visibility due to its optical, electro and electro-optical properties, but still little explored as ceramic. The sintering starting material was obtained by solid state reaction between Bi2O3 e TiO2; the synthesized BTO was grinded in ball milling until sub micrometric sizes. The conditions for preparing green samples were also investigated, allowing samples with green relative density between 58% and 62%, with uniaxial and isostatic pressing techniques. The study of the sintering process involved different sintering programs, under different atmospheres conditions and additive utilization. Optimized conditions were established and the limiting factors discussed. The quality of the obtained ceramics was assessed by their final relative density, phase homogeneity, microstructure and optical properties (transmission, optical activity and electro-optical performance). Samples with relative density above 99,9% and 50% of the monocrystal´s optical transmission in the 633 nm wavelength and equal optical activity were obtained. Nevertheless, the ceramics still show scattering centers and none liquid electro-optical effect was observed.
Interações da albumina de soro bovino com surfactantes e efeitos de antioxidantes sobre a oxidação de lipoproteínas de baixa densidade induzida por íons de cobre
(Universidade Federal de Goiás, 2012-08-02) ANJOS, Jorge Luiz Vieira dos; Alonso, Antônio; http://lattes.cnpq.br/5013069863616789
Human plasma contains primarily large proteins, ranging in composition and concentration as the individual's physiological state. Among these proteins, albumin and low density lipoprotein (LDL) have been widely studied. The albumin (the most abundant protein in blood plasma) is responsible for important functions in the human body due to its excellent ability to bind and transport small molecules. In turn, the LDL (responsible for transporting cholesterol to the cells) in its oxidized form is directly associated with atherosclerosis, the main cause of cardiovascular disease. In the first part of this work, the interaction of bovine serum albumin (BSA) with the ionic surfactants sodium dodecylsulfate (SDS), cetyltrimethylammonium chloride (CTAC) and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) was studied by electron paramagnetic resonance (EPR) spectroscopy of spin label covalently bound to the single free thiol group of the protein. In the second part was studied the oxidation of human LDL by copper ions and also the antioxidant potential of polyphenols resveratrol, (+)-catechin and quercetin, using the EPR of a spin label, derived from stearic acid (5-DSA), and the method malondialdehyde content (MDA). Part I: The dynamics of the BSA and the thermodynamic parameters for transferring the nitroxide side chain from the more motionally restricted to the less restricted component were monitored through EPR spectra simulation. Whereas SDS and CTAC showed similar increases in the dynamics of the protein backbone for all concentrations used, HPS presented a smaller effect at concentrations above 1.5mM. At 10mM of surfactants and 0.15 mM BSA, the standard Gibbs free energy change was consistent with protein backbone conformations more expanded and exposed to the solvent, but with a less pronounced effect for HPS. In the presence of the surfactants, the enthalpy change, related to the energy required to dissociate the nitroxide side chain from the protein, was greater, suggesting a lower water activity. The nitroxide side chain also detected a higher viscosity environment in the vicinity of the Mal-5 induced by the addition of the surfactants. The results suggest that the surfactant-BSA interaction, at higher surfactant concentration, is affected by the affinities of the surfactant to its own micelles and micelle-like aggregates. Complementary DLS (Dynamic Light Scattering) data suggests that the temperature induced changes monitored by the Mal-5 reflects local changes in the vicinity of Cys-34 BSA residue. Part II: The oxidative process induced by copper ions results in lipid peroxidation of LDL (evidenced by high concentration of MDA) could also be monitored by the decrease in the dynamics of 5-DSA, reflected in increased spectral parameter 2A//. The oxidation of LDL resulted in increased energy barrier that the spin labels must overcome to achieve higher degrees of motion. All polyphenols studied were able to protect LDL completely against oxidation for concentrations from 30 M, whereas the protection provided by the Butylated hydroxytoluene (BHT) occurred only partially. This result, based on data from the literature, was attributed to the ability of polyphenols act as scavenger and chelating agents, while the BHT acts just like scavenger due the presence of only a single hydroxyl group in its molecule.
Efeitos de terpenos nas membranas de estrato córneo estudados por ressonância paramagnética eletrônica
(Universidade Federal de Goiás, 2008-02-18) Anjos, Jorge Luiz Vieira dos; Alonso, Antônio; http://lattes.cnpq.br/5013069863616789
The interaction of the skin penetration enhancers DL-menthol, -terpineol, 1,8-cineole and (+)-limonene with membranes of the uppermost skin layer, the stratum corneum (SC) and with multilamellar vesicles from 1,2-dipalmitoyl-sn-glycero-3-phosphaticylcholine (DPPC)is investigated by electron paramagnetic resonance (EPR) spectroscopy using spin-labeled analogs of androstanol ASL),stearic acid (5-DSA), methyl stearate (5-DMS) and a small spin label 2,2,6,6-tetramethylpiperedine-1-oxyl (TEMPO). The terpenes were added to SC samples using ethanol as a co-solvent (20% ethanol in the buffer), the effect of ethanol on the SC also was investigated. The spectra of spin labels ASL, 5-DSA and 5-DMS in the membranes of SC are characterized by the presence of two spectral components differing in mobility.Component 1 was attributed to the spin labels H-bonded to the headgroups, while component 2 was assigned to the spin labels H-bonded to water molecules or temporally non-hydrogen-bonded. EPR results showed that ethanol in the range 0-70% did not alter the fluidity in SC membranes or the relative fractions of these two components. Instead, ethanol only caused a selective extraction of spin labels, indicating that ethanol acts as extractor and not as fluidizer when facilitates molecular permeation in the skin. Addition of 1% DLmenthol to the solvent containing 20% ethanol increases both the mobility and the fraction of spin labels in the component 2 (more mobile spectral component). Similarly, with the addition of 1,8-cineole, the spin probes were gradually transferred from the motionally more restricted component 1 to the more mobile component 2. The spectrum of the spin label TEMPO in the membranes of SC allows for the determination of the actual partition coefficient and rotational diffusion rates of the spin probe in the aqueous and hydrocarbon environments. The enthalpy changes,H°,to transfer the spin probe from the aqueous to the hydrocarbon phase, as well as the activation energies associated to its rotational motion, were considerably smaller for SC when compared to DPPC, indicating less pronounced thermal reorganizations for SC samples. For DPPC,all terpenes increased both the partition coefficient and the rotational diffusion rate of the spin label in the membrane, except in the liquid-crystalline phase. These results suggest that the terpenes,effectively acting as spacers in the membrane,fluidize the lipids and cause ruptures in the hydrogen-bonded network of the membrane-water interface, with consequent displacements of spin probes towards the hydrophobic core. The EPR spectra of maleimide derivative spin label (6-MSL)covalently attached to stratum corneum proteins indicate that 1,8-cineole does not alter the dynamics of protein backbones.Instead, this terpene only increases the solvent s ability to dissolve and mobilize the nitroxide side chain, which is in agreement with its low irritation response.
Tratamento de sistemas abertos via reservatórios térmicos bosônico e fermiônico
(Universidade Federal de Goiás, 2019-04-15) Araújo, Dannilo Iágor Evangelista de; Almeida, Norton Gomes de; http://lattes.cnpq.br/3182841849332242; Almeida, Norton Gomes de; Colherinhas, Guilherme; Almeida, Agnaldo Rosa de; Cardoso, Wesley Bueno; Sales, José de Sousa
We developed this work at the moment with the objective to resolver the master equation for both thermal reservoir: bosonic and fermionic, as well as the master equation in reservoirs of vacuum and of Fock compressed . the bosonic thermal reservoir is modeled by a collection of coupled harmonic oscillators and the fermionic reservoir by a collection of two-level atoms. We made use of the Jaynes-Cummings model and the Bohr, Bohr-Markov and Markov approaches. In the end we discussed the application to the master equation for two distinct phenomena, Cooling by Heating (CBH) analyzing average energy graphs to the atomic system versus number of photons, and the average energy of the bosonic system as a function of the mean number of phonons, we observed the negative temperature in the absolute scale due to the inversion of population of states in function of cooperativity, we also analyzed a signature of negative response in a three level system interacting in a optical cavity, that comes as a result of decrease in the output field intensity when the input field intensity is increased.
Síntese, caracterização e magnetohipertermia de ferritas de manganês Mn1-xAxFe2O4 dopadas com cobre, magnésio ou cobalto
(Universidade Federal de Goiás, 2017-07-12) Araújo, Marcus Vinicíus; Bakuzis, Andris Figueirôa; http://lattes.cnpq.br/3477269475651042; Bakuzis, Andris Figueirôa; Coaquira, José Antônio Huamaní; Santos, Marcus Carrião dos; Silva, Sebastião Willian da; Bufaiçal, Leandro Félix de Sousa
Nanoparticles based on Mn-ferrite, Mn1−xAxFe2O4, doped with copper, magnesium and cobalt (A = Cu, Mg ou Co) were synthesized by hydrothermal method under pressure, with X varying from 0 to 0, 5. Magnetic fluids stable in physiological conditions were obtained surface-coating the nanoparticle with citric acid. X-ray diffraction confirmed the spinel structure. Energy dispersive spectroscopy (EDS) confirmed the success of the synthesis of the mixed ferrite, where the element composition agreed with the value expected within an error of 10%. Transmission electron microscopy showed sphericalshaped nanoparticles, while magnetization data at room temperature allowed the analysis of the coercivity field (Hc) and the saturation magnetization (Ms). Ms decreased with the increase of X for the Cu and Mg doped samples, while the opposite effect was observed for Co doped nanoparticles. Hc increased the higher the X value for all the samples. The effect on the Cu and Mg-doped ferrites are explained by the increase in particle size. However, the Co-doped samples, showed a diameter increasing the higher X, but Hc also increased. In this case the Hc behavior is explained by the increase concentration of Co and its effect on the magnetic anisotropy which increases for higher Co content. The magnetic hyperthermia efficiency of the magnetic fluids, for all samples, were investigated in a field amplitude ranging from 50 Oe to 170 Oe and frequencies from 110 kHz up to 990 kHz. The hyperthermia efficiency decreased with X increasing, considering the case of 130Oe and 333 kHz, which indicates that at this experimental condition undoped Mnferrite nanoparticles are better for hyperthermia. In most of the samples it was observed that the efficiency scaled with the square of the field amplitude, which is in accordance with Linear Response Theory (LRT). In addition, the hyperthermia frequency dependence study showed a saturation effect, for some samples, at a frequency higher than 600 kHz. The experimental data as function of frequency were susccessfully curve fitted with the LRT model using 2 free parameters related to the effective relaxation time ( ef ) and the equilibrium susceptibility ( 0). In particular, for theMn-ferrite sample for a field of 130Oe it is found ef = 5, 2 · 10−7s and 0 = 0, 028. The value of ef can be explained using an effective magnetic anisotropy value of 2·105 erg/cm3. The value is one order of magnitude higher than the bulk value, and allowed one to estimate the surface anisotropy contribution to in the order of 0, 04 erg/cm2. On the other hand, a linear chain formation model, for this sample consisted of a trimer (3 nanoparticles), can also explain the increase of the effective anisotropy. Moreover, we found a 0 value lower than the estimated Langevin susceptibility. In order to explain this, a new model, valid in the linear regime, was developed considering the contribution from blocked nanoparticles. Indeed, the analysis of hyperthermia data using this model indicates that the contribution to heat generation spans from 34.7% of the nanoparticles for a field of 110 Oe up to 52.5% at 170 Oe.
POVM no contexto de eletrodinâmica quântica de cavidades
(Universidade Federal de Goiás, 2017-03-13) Assis, Rogério Jorge de; Almeida, Norton Gomes de; http://lattes.cnpq.br/3182841849332242; Almeida, Norton Gomes de; Villas-Boas, Celso Jorge; Almeida, Agnaldo Rosa de
In this work it is proposed a simplified scheme to unambiguously discriminate between one of two nonorthogonal cavity field states. This scheme, which is based on POVM - positive operator valued measure, uses one three-level atom as the ancilla to obtain information on the cavity field state, the target. The efficiency of this scheme in discriminating the two quantum states is analy zed by comparing the maximum theoretical success probability with the maximum success probability possible to our case.
Phenomenological study of neutrino invisible decay on MINOS and MINOS+ experiments
(Universidade Federal de Goiás, 2025-04-03) Azevedo, Daniel Araújo de; Gomes, Ricardo Avelino; http://lattes.cnpq.br/6538341799051577; Gomes, Ricardo Avelino; Paulo Júnior, Ademar; Oliveira, Guilherme Colherinhas de
The neutrino oscillation model is already well stablished; however, there is still interest in investigating phenomena that may occur alongside it. One of them being decay, already ruled out as happening alone, but can still occur with oscillation. Some of the recent analysis in the literature try to, using experimental data from accelerator experiments, have a measurement of the parameter τ3/m3, carrying information about the decay of the mass eigenstate ν3. The following work consider the data from the MINOS and MINOS+ long-baseline experiments, for different models of neutrino oscillation: the standard oscillation and the oscillation with decay in vacuum and in matter. From the Pνµ→νµ probability, and considering the charged current events of νµ, we want to show: how the presence of the MINOS+ data affects the results obtained with the MINOS experiment; we also implement the oscillation with decay in matter model, which is a more suited one as a proof of concept, considering that modern studies do consider the matter effects; a value for the τ3/m3 parameter. This analysis also yields a best fit value for the oscillation with decay in matter of the combined experimental data, having ∆m 2 32 = 2.226 × 10−3 eV2 , sin2 θ23 = 0.715 and a lower bound limit of 90% C.L. for the decay parameter of τ3/m3 > 1.52×10−12 s/eV.
Estudo das interações de moléculas orgânicas com imunoglobulinas G
(Universidade Federal de Goiás, 2015-04-30) Bezerra, Fabio de Castro; Gonçalves, Pablo José; http://lattes.cnpq.br/0515343409614452; Gonçalves, Pablo José; Hioka, Noboru; Souza, Márcio Adriano Rodrigues
(Sem resumo em outra língua)
Estudo de encapsulação de nanopartículas magnéticas em nanoporos de alumina.
(Universidade Federal de Goiás, 2010-05-26) BRANQUINHO, Luis Cesar; Bakuzis, Andris Figueiroa; http://lattes.cnpq.br/3477269475651042
In this work we investigated the encapsulation of magnetite nanoparticles into the nanopores of anodic alumina membranes using atomic force microscopy (AFM), vibrating sample magnetometer (VSM) and electron magnetic resonance (EMR). Three biocompatible magnetic fluids, with different nanoparticle diameters, stably dispersed in water at physiological conditions, were used. The nanoparticles were obtained through the coprecipitation method and characterized by X-ray diffraction, from which we obtained the nanoparticle size and confirmed the crystal structure. The Scherrer´s relation revealed a nanoparticle diameter of 10.1nm, 12.3nm and 13.8nm. The alumina membrane were prepared through anodization process. The nanopores were arranged on a hexagonal lattice with an alumina thickness of 4 μm, a distance between pores (center to center) of 105 nm, and samples containing nanopores with diameter of 35 nm or 80 nm. The method of encapsulation of nanoparticles consisted of depositing a drop of magnetic fluid into the surface of alumina. The fluid enters the nanopores through capillarity carrying the nanoparticles into it. AFM images prove that we had success in encapsulating nanoparticles only for the alumina samples with nanopores with a size of 80 nm. Magnetization data of the alumina sample containing nanoparticles with a diameter of 13.8nm encapsulated into nanopores of 80 nm, revealed an increase, with respect to the first procedure of encapsulation, of 48 % of the nanoparticles internalized into the nanopore after the second process of encapsulation. Further, different from all the samples investigated, EMR data for the alumina containing nanopores of 80 nm and nanoparticles of 13.8 nm, after the first procedure of encapsulation, had shown perpendicular magnetization with respect to the alumina surface. The EMR spetra were curve fitted using two Gaussian lines, one representing the nanoparticles with magnetization parallel to the surface and the other perpendicular. AFM images suggest, in our sample, that residues on the alumina surface are responsible for the parallel component. The magnetic resonance field data, for the perpendicular contribution, were analyzed taking into account in the energy density terms with uniaxial and cubic symmetry. The uniaxial energy contribution had a term due to magnetic dipolar interaction, between nanoparticles forming a linear chain, a magnetostatic term, due to the nanostructures self-organization, and also a magnetoelastic contribution, which came from the stress generated by the packing of nanoparticles, whose origin were related to the dipolar interaction between nanoparticles forming the linear chain. Indeed, the theoretical analysis allowed us to conclude that the mean size of the chain could vary from 4 to 9.5 nanoparticles. Finally, after heating the alumina, at 300°C for one hour, which contained nanoparticles with a size of 10.1 nm, and dissolving it in NaOH aqueous solution, AFM data were obtained. The AFM images confirmed the existence of nanowires. The diameter distribution, obtained from the AFM images, were curve fitted with a lognormal distribution revealing a modal diameter for the nanowires of 25,8 0, ± 4nm and diameter dispersity of 0,30 ± 0,02nm .
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 Teixeira
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.
Dinâmica molecular e particionamento do marcador de spin di-terc-butil nitróxido em membranas de estrato córneo. Efeito de Terpenos
(Universidade Federal de Goiás, 2009-03-31) CAMARGOS, Heverton Silva de; Alonso, Antônio; http://lattes.cnpq.br/5013069863616789
Terpenes are a very promising class of skin penetration enhancers especially due to their low potential of irritation in the skin. In this work, we have used the electron paramagnetic resonance (EPR) spectroscopy of the small spin label di-tert-butyl nitroxide (DTBN), which partitions the aqueous and hydrocarbon phases, to study the interaction of the terpenes ®-terpineol, 1,8-cineole, L(-)-carvone and (+)-limonene with the uppermost skin layer, the stratum corneum, and the membrane models of 1,2-dipalmitoyl-sn-glycero- 3-phosphatidylcholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The EPR spectra indicated that the terpenes increase both the partition coe±cient and the rotational di®usion rate of the spin labels in the stratum corneum membranes whereas for DMPC and DPPC bilayers were observed similar e®ects only at temperatures below the liquid-crystalline phase. The EPR parameter associated to probe polarity inside the membranes showed thermotropic induced changes, suggesting relocations of spin probe, which were dependent of the membrane phases. While DMPC and DPPC bilayers showed abrupt changes in the partitioning and rotational correlation time parameters at the phase transitions, the SC membranes were characterized by slights changes in whole interval of measured temperatures, presenting the greatest changes or membranes reorganizations in the temperature range of v50 to v74±C. The results suggest that the terpenes act as spacers that weaken the hydrogen-bonded network at the polar interface thus °uidizing the stratum corneum lipids and, in consequence, increase the permeation of small polar molecules across the membranes. 2
Estudos de membranas modelo e efeitos de terpenos em membranas de leishmania por ressonância paramagnética eletrônica
(Universidade Federal de Goiás, 2013-11-16) Camargos, Heverton Silva de; Alonso, Antônio; http://lattes.cnpq.br/5013069863616789; Alonso, Antônio; Nakamura, Celso Vataru; Ruggiero Neto, João; Dorta, Miriam Cristina Leandro; Anjos, Jorge Luiz Vieira dos
Electron paramagnetic resonance (EPR) spectroscopy of spin labels was used to study the main structural accommodations of environment-sensitive probes in the bilayers of saturated phosphatidylcholines with acyl chains lengths ranging from 16 to 22 carbon atoms. The more detailed analysis were made on the spin probe 5-doxyl methyl stearate (5-DMS) whose EPR spectra allowed to identify two distinct spectral components in thermodynamic equilibrium at temperatures below and above the main phase transition. The EPR spectroscopy distinguishes two components associating lower motion with higher polarity (denoted component 1) and higher motion with lower polarity (component 2), which may be assigned to one shallow (more rigid structure) and one deep population of spin probe, respectively. At temperatures until 22◦C only one spectral component can be noted in the spectra whereas at 30◦C the component 1 coexists with an appreciable fraction of component 2. In the liquid-crystalline phase the 5-MSL showed two spectral components for all studied lipids in the entire range of measured temperatures. An accurate analysis of EPR spectra, performed using two fitting programs (NLLS and EPRSIM), allowed us to obtain the thermodynamic profile to these major probe accommodations. Focusing the analysis on two-component EPR spectra, it was studied the influences of cholesterol and a membrane permeation enhancer on the mobility and distribution of spin label on these two main bilayer environments. Parte II Cutaneous leishmaniasis is a neglected tropical disease that infects millions of people worldwide, representing a serious public health problem. The current treatment is based on chemotherapy, using pentavalent antimonials compounds, which cause serious side effects. Electron paramagnetic resonance (EPR) spectroscopy of the spin-label analog of stearic acid (5-DSA ) was used to monitor the effect of the terpenes α-terpineol, 1,8-cineole, III (+)-limonene and nerolidol on the plasma membrane fluidity of Leishmania amazonensis promastigotes. Cytotoxic effects on the parasite were also measured to investigate the relationship between the cytotoxic potential of terpenes and their ability to alter membrane fluidity. All terpenes increased the fluidity of the cellular membrane, without significant differences at higher concentrations. However, the minimum concentration required to cause a change in the membrane was very different between the terpenes and similar to that caused 50% growth inhibition (IC50) showing a correlation between membrane alterations and cytotoxicity. The IC50 values of terpenes analyzed showed the following relationship: nerolidol < (+)-limonene < α-terpineol < 1,8-cineole, with an IC50 of 8 μM for nerolidol and 4700 μM to 1,8- cineole. The EPR spectra of the maleimide derivative spin label (6-MSL) covalently attached to the Leishmania membrane proteins indicated that the terpenes essentially do not alter the dynamics of protein backbone and only increase the mobility of the nitroxide side chain. Cell lysis was not detected at cytotoxic concentrations, as measured by the presence of spin-labeled membrane fragments. Since the terpenes are considered potent skin permeation enhancers with low irritation potential, this work suggests checking the possibility of terpenes applications in the treatment of tegumentary leishmaniasis, where terpenes could perhaps perform a dual action of be an active principle and at the same time facilitate the penetration of other molecules with antileishmanial activity.

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