Programa de Pós-graduação em Física

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Superposição assimétrica de estados coerentes circulares
(Universidade Federal de Goiás, 2002) Maia, Luciano Paulo de Araújo; Baseia, Basilio; http://lattes.cnpq.br/5804506385505435
In this paper we present a new quantum state of light, obtained from an asymmetric superposition of coherent states in circular stationary mode. The generation of this state was proposed and the experimental apparatus required is presented. General expressions describing various properties (statistical distribution, variances, atomic inversion, etc..) Were obtained for arbitrary generations. We observed how they behave their properties by varying the phase between the components of superpo- sition states. We show that the statistical properties do not fully characterize the resulting state, showing different states with the same statistics. Alternative ways to distinguish these states were considered. Based on quantum interference in phase space, we show how we can generate an approximation of the number state N2 thru a process called "quantum sculpture,"and check the influence of the stage in this process. Finally, we measured the classicalidade not analyze this state and its representation in phase space.
Dinâmica de proteínas: efeitos da hidratação em estrato córneo e de detergentes em albumina
(Universidade Federal de Goiás, 2002-12-19) Silva, Junaine Vasques da; Alonso, Antônio; http://lattes.cnpq.br/5013069863616789; Alonso, Antônio; Ito, Amando Siuiti; Rabelo, José Nicodemos Teixeira
The main function of the most superficial layer of the epidermis, the Stratum Corneum (SC), is to provide a physical barrier that controls the transepidermal water loss as well as the permeation of another substances in both directions across the skin. The SC is formed by anabolically dead cells, the terminally differentiated corneocyte, and its function is essentially accomplished by forming a highly insoluble protein structure on the surface of the corneocytes, termed the cornified cell envelope, and by impeding water diffusion across the SC by mortaring the corneocytes together by layers of skin-specific lipids, essentially ceramide, cholesterol and fatty acid. In this work the cell envelope of the SC was spin labeled with a sulfhydryl-specific nitroxide reagent to investigate the water content effects upon the protein dynamics directly in the intact tissue. A two-state model for the nitroxide side chain described the coexistence of two spectral components in the electron paramagnetic resonance (EPR) spectra. The so-called strongly immobilized component, S, is associated with the EPR signal of a motionally restricted nitroxide fraction having its N-O group hydrogen bonded to protein (rigid structure) while the weakly immobilized component, W, corresponds to the signal provided by the spin labels with higher mobility (~10 times greater) exposed to the aqueous environment. The relative populations between these two mobility states, S and W, are in thermodynamic equilibrium. The standard Gibbs free energy, enthalpy and entropy changes for transferring the nitroxide side chain from the state contacting the solvent, W, to the one contacting protein, S, indicated that the reduction of the SC water content to below ~h 0.69, g H2O per g dry SC, stabilizes the protein interacting state, S. Upon decreasing the SC hydration level below ~h 0.69 the segmental motion of the polypeptide chains and the rotational motion of the spin-labeled side chain were also constrained. To test our methodology in a pure and very well known protein, we also studied the effects of two types of detergents on the bovine serum albumin (BSA). Both detergents, the anionic sodium dodecyl sulfate (SDS) and the zwitterionic N-hexadecyl-N,N-dimethyl-3-ammonium-1-propanesulfonate (HPS) increase the mobility of the protein backbone and of the nitroxide side chain. The thermodynamic parameters indicated that these detergents destabilize the protein favoring less compact conformations. This work can also be useful to improve the spectral analysis of site-directed spin labeling, especially for a more quantitative description in terms of thermodynamic parameters.
Efeitos da correlação eletrônica sobre as polarizabilidades longitudinais do polidifluoroacetileno
(Universidade Federal de Goiás, 2005-03-31) TORRES, Elber Magalhães; FONSECA, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; AMARAL, Orlando Afonso Valle do; http://lattes.cnpq.br/5776659588409128
This work presents ab initio results, including correlation corrections, for the static longitudinal linear polarizability, ®L, and longitudinal second hyperpolarizability, °L, of planar and twisted fluorinated polyacetylene (polyacetylene) chains. These electric properties were calculated by the finite field (FF) method and the correlated energies were obtained by means of the second order MÁller-Plesset perturbation theory (MP2). Our MP2 calculations were performed using the 6-31G basis set, although the geometry optimization involved both, the 6-31G and 6-31G(d) basis sets. Our results show that the incorporation the electron of correlation effects in the calculations of the polarizabilities, specially the hyperpolarizabilities, is essencial in order to obtain reliable estimates of these properties. Our estimates also demonstrate that the substitution of the H atoms in polyacetylene by F atoms, a procedure that gives rise to polydifluoroacetylene (PDFA), has the effect of incrasing the non-linear response of this material.
Operador Deslocamento Condicional: Geração de Estados e Medida da Função de Wigner
(Universidade Federal de Goiás, 2006-03-24) SOUZA, Simone Ferreira; BASEIA, Basilio; http://lattes.cnpq.br/5804506385505435
We present a feasible proposal for the construction of the conditional displacement operator using a Kerr medium between two beam splitters fed from coherent states highly excited. The device allows the implementation of the generation of a new class of states the quantized electromagnetic field (arbitrary superpositions of states with states moved) and the measurement of the Wigner function for arbitrary states. The application special case of the number of states and study their nonclassical properties were also considered.
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.
Geração e Propriedades de Superposição de Estados Comprimidos deslocados.
(Universidade Federal de Goiás, 2007-07-20) WEBER, Paulo Estevão Rezende; BASEIA, Basilio; http://lattes.cnpq.br/5804506385505435; AVELAR, Ardiley Torres; http://lattes.cnpq.br/5732286631137637
A feasible scheme for generating squeezed states of superposiçãao displaced in superconducting cavities is presented. The characteristics and properties, especially the non-classical, are studied by means of the Wigner function and Q parameter of Mandel. The probability of successful generation of such superposition are also considered.
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.
Cálculo da condutividade térmica do Argônio sólido puro e com defeito pontual
(Universidade Federal de Goiás, 2008-03-14) Trindade, Ranyere Deyler; Silva, Ladir Cândido da; http://lattes.cnpq.br/7442411485710574
In this work, using the Green-Kubo method combined with Molecular Dynamic (DM), we calculate the thermal conductivity of a solid Argon "free of defects"and with point defect present, for temperatures varying from 10 up to 60 K at density 22,3 ml/mol. The obtained results are in good agreement with the available theoretical and experimental results in the limites of low and high temperatures, but with some discrepances in about 15 % for intermediate values of temperatures. The purpose to include point defects with the objective of correction of the simulational results to compare with experimental measuremments for intermediate temperatues had not the expected e?ect. However, we believe that it should be due to the fact that the density used in the simulation for the point defect is high based on the experimental estimates of point defect density in this system. Our results suggest that the Green-Kubo method combined with Molecular Dynamics is a powerful tool to calculate the thermal conductivity of solids at high temperatures. With the construction of accurate and reliable interatomic potentials to describe more complex materials, such as high temperature ceramic and minerals at extreme condiction of pressure and temperature, this method could soon become very useful to calculate thermal conductivity in materials where the access to experimental data is hard.
Cálculos de propriedades elétricas da metanol incluindo correções vibracionais e correlação eletrônica
(Universidade Federal de Goiás, 2009) Dutra, Adriano da Silva; Castro, Marcos Antônio de; http://lattes.cnpq.br/3500875789893244
In this work we report results for the polarizability, and first and second hyperpolariz- abilities of the methanol molecule including vibrational corrections and electron correlation effects. The Vibrational corrections were computed using the perturbation theoretic approach of Bishop and Kirtman and the electron correlation effects were taken into account through the CCSD(T) method implemented in the GAUSSIAN 03 program. The electronic contributions to the electric properties were calculated using the finite-field scheme. Comparisons of our CCSD(T) values with previous TDHF result show that the electron correlation effects, are in general, important. An analysis of the importance of the vibrational corrections shows that the zpva correction is not negligible, specially for the hyperpolarizabilities. The pv correction is, in general, important and the double-harmonic approximation is suitable to the calculation of this correction for most of the nonlinear optical processes studied.
Monte Carlo quântico aplicado ao estudo do comportamento quântico-clássico do Neônio
(Universidade Federal de Goiás, 2009-02-20) CARVALHO, Thiago Milograno de; SILVA, Ladir Cândido da; http://lattes.cnpq.br/7442411485710574
In this work we have applied Quantum Monte Carlo method at finite temperature known as Path Integral Monte Carlo (PIMC) to study the quantum-classical behavior of the Neon. We have calculated the one body density matrix as well as the atomic momentum distribution which have shown to be significantly different from the classical Maxwell- Boltzmman distribution in the range of densities and temperatures studied. The deviations from a classical gaussian are substantial but it decreases as one goes to temperatures above T = 35 K or densities below p = 20 nm−3. Furthermore, at low temperature the results show that there are more low momentum atoms than in a classical gaussian distribution.
Modelo de Jaynes-Cummings completo de dois fótons: estudo e aplicações
(Universidade Federal de Goiás, 2009-02-20) SOUZA, Alexandre Divino de; AVELAR, Ardiley Torres; http://lattes.cnpq.br/5732286631137637; BASEIA, Basilio; http://lattes.cnpq.br/5804506385505435
In this work we have studied the two photon Jaynes-Cummings model to describe the interaction of a three-level atom in the configuration with a single-mode of a cativy-field. We have used the effetive and full microscopic Jamiltonian approach to compare the results obtained in these tow descriptions. We employed the two-photon Jaynes-Cummings model int the full microscopic Hamiltonian context to implement schemes to quantuam entanglement swapping, for approximate and conditional quantuam teleportation for an unknown atomic state, for a superposition of zero- and two photon states. Both schemes were implemented using no measurement in the Bell base states.
Espectro de Absorção da Orto-betaína em Água: um Estudo Teórico usando o Método Seqüencial Monte Carlo/Mecânica Quântica
(Universidade Federal de Goiás, 2009-03-26) OLIVEIRA, Leonardo Bruno Assis; FONSECA, Tertius Lima da; http://lattes.cnpq.br/8193800922148980
Using sequential Monte Carlo simulation and quantum mechanics calculations(S-QM/MM) based on the TD-DFT methods we have been used to study the solvatochromic shift of the orto-betaine in water. Statistically uncorrelated configurations have been obtained from MC simulations with unpolarized and in-solution polarized solute. To account for the solute electronic polarization, we have used an iterative procedure based on the S-QM/MM methodology to determine the in-solution dipole moment of orto-betaine in presence of water molecules treated as point charges. MP2/cc-pVDZ calculations on the configurations bearing the orto-betaine molecule electrostatically embedded in the 320 water molecules show that the solute polarization increases the dipole moment of orto-betaine, compared to gas phase, by 49%, giving the in-solvent dipole values of 12.2 D. MC simulation results for the Helmholtz free energy as function of the torsion angle indicate that the mosts table conformer of the orto-betaine in water is that with an angle of 60o, after including solute polarization. The average number of solute-solvent hydrogen bonds was analyzed and it was found a large increase of 3,25 in polarized situation to only 1,82 in the unpolarized situation. Modeling the water molecules by point charges (electrostatic embedding), the results show that solvent effects on the absorption spectrum have a significant contribution of the electrostatic interactions. In comparison with the result of gas-phase, TD-BHandHLYP/6311+G(2d,p) calculations give for the π → π∗ electronic transition solvatochromic shifts of 0.42 eV and 0.90 eV for the unpolarized and polarized orto-betaine, respectively. The experimental spectral shift value of 0.90 eV is very well reproduced by the present theoretical results after including the solute polarization. The TD-B3LYP/6311+G(2d,p) model gives the corresponding value for the polarized orto-betaine of 0.52 eV which is an underestimated result in qualitative agreement with experiment. This study indicates that the inclusion of the solute polarization is important for a reliable description of the spectral shifts considered here.
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
Ressonância Ferromagnética em Super-Redes NiFe/Ru
(Universidade Federal de Goiás, 2009-04-14) LANDI JUNIOR, Salmon; PELEGRINI, Fernando; http://lattes.cnpq.br/0159280600583768
The Ferromagnetic Resonance (FMR) technique was used to study the magnetic anisotropy of NiFe/Ru multilayers. The FMR spectra and absorption fields of multilayers with Ru layers thickness bellow 20 Å are the same as that of single monolayer films. Evidence of the coupling between the magnetic layers also is given by the fact that for the sample with Ru thickness equal to 7 Å, in normal configuration of the applied static field, spin-wave resonance modes also are excited by the microwave field. The interlayer coupling constant obtained is equal to 1, 1 £ 10¡7 erg/cm. For the set of samples with different NiFe thicknees, the analysis of the effective magnetic anisotropy in terms of volume and surface contributions, gives KV = 3, 4 £ 106 erg/cm3 and KS = 1, 2 erg/cm2.
Estudo por ressonância ferromagnética das anisotropias uniaxial e unidirecional em bicamadas e tricamadas magnéticas
(Universidade Federal de Goiás, 2009-04-15) Sousa, Marcos Antonio de; PELEGRINI, Fernando; http://lattes.cnpq.br/0159280600583768
The Ferromagnetic Resonance (FMR) technique at the X-band (~ 9.70 GHz) and Q-band (~ 34.0 GHz) was used to study the magnetic properties of NiO/Co, NiO/Py and Py/FeMn bilayers, and Co/NiO/Co trilayers with different thicknesses, deposited by dc magnetron sputtering technique in the presence of a 400 Oe magnetic field. The FMR experiments were all done at room temperature using a high sensitivity Bruker ESP-300 spectrometer, with static scanning field and usual modulation and phase sensitive detection techniques. The angular dependence of the inplane resonance field allows the measurement of the exchange bias field for some NiO/Py bilayers and the uniaxial anisotropy of the Co layer of NiO/Py bilayers and Co/NiO/Co trilayers. The value of the exchange bias field of the NiO/Py bilayers varies from 29 Oe to 123 Oe while the uniaxial anisotropy field of the Co layer, varies from 5 to 45 Oe. For Co/NiO/Co trilayers, the Co in-plane uniaxial anisotropy field varies from 34 to 216 Oe. The out-of-plane angular dependence of the resonance field allows the measurement of the effective magnetization and the g-factor, which depend not only on the specific parameters of the samples, such as thickness of the ferromagnetic layer, but also on the deposition conditions. The results obtained were compared with known values in the literature and show the high sensitivity of the ferromagnetic resonance technique in the study of the magnetic anisotropy and the exchange bias phenomena.
Estudo estrutural de complexos de cobre (II) como modelos de sítios metálicos de enzimas com atividade oxidativa
(Universidade Federal de Goiás, 2009-04-24) SOUSA JÚNIOR, Joel Padilha de; SABINO, José Ricardo; http://lattes.cnpq.br/9101677399031185
We present the structural study, by x-rays diffraction, of two forms on the crystalline and molecular structures of the metal-organic single-crystal compounds Dicloro[N- benzoyl-N´-(4-methylphenyl)-N´´-(2-pyridinyl)-guanidine)]copper(II). Such compound is known for the phenol oxidative catalictic bioactivity. The compound is a copper(II)-guanidine de- rivative complex. The main motivation of the present work is the polimorphism observed on such complex when the crystallization conditions are changed. The structures were sol- ved using the Direct Methods method and the structural parameters were refined with full matrix least-squares method. The copper(II) complex C19H22Cl2CuN4O crystallizes in the triclinic system in the P¯1 space group, with a single molecule in the assymetric unit and unit cell parameters: a = 8.616 (3) °A, b = 9.288 (3) °A, c = 13.623 (2) °A, α = 106.96 (2)o, β = 96.02 (3)o, γ = 100.60 (2)o, with volume 1010.3 (5) °A3 and calculated density of 1.528 Mgm−3. The same compound also crystallizes in the monoclinic system in the P21/n space group and unit cell parameters: a = 7.937 (2) °A, b = 18.727 (2) °A, c = 13.993 (2) °A, β = 102.03 (2)o, with volume 2034.2 (6) °A3 and calculated density 1.518 Mgm−3. The two isomeric molecules showed different conformations from one crystal packing to the other, due to the different intermolecular interactions. Given the different crystal packing and intermolecular interactions, we performed electronic structure calculations using the Density Functional Theory in order to derive the energetic differences, including calculations of dimers linked by hydrogen bonds, for evaluating the crystal packing influence on the complex stability in their crystal structures.
Estudo de fases cristalinas no sistema Bi2O3-Tb4O7
(Universidade Federal de Goiás, 2009-08-25) MATOS, Lucyene Nascimento; CARVALHO, Jesiel Freitas; http://lattes.cnpq.br/5841291496427516
A systematic study concerning the crystalline phases in the Bi2O3-rich region of the system Bi2O3-Tb4O7 was made. X-ray powder diffraction method, differential thermal analysis (DTA) and differential scanning calorimetry (DSC) were used in the study of the obtained crystalline phases. Sixteen samples with composition in the range of 4.21 to 33.33 mol% of Tb4O7 were synthesized at 800oC by solid state reaction synthesis. Three distinct crystalline phases were initially identified: a tetragonal phase in the composition range of 4.21 to 5.69 mol% of Tb4O7, a cubic phase for compositions between 6.12 and 29.03 mol% of Tb4O7, and a monoclinic one with 33.33 mol% of Tb4O7. The thermal stability of these compositions was rigorously investigated and the results shown that they are metastable phases in almost all studied range. Under thermal annealing at 500oC, tetragonal phase undergoes decomposition into two phases, monoclinic and rhombohedral ones. The cubic phase, under the same thermal annealing, decomposes partially into a rhombohedral one, except for the interval between 25.0 and 29.1 mol% of Tb4O7. In this case, there was not decomposition under thermal annealing at 500oC during 373 hours, suggesting the cubic phase is stable in this composition range. The monoclinic phase was also tested concerning its thermal stability, but no phase transition was verified. The existence of a possible composition range in the system Bi2O3-Tb4O7 with stable cubic -Bi2O3 type structure is a new and promise result, because of the high ionic conductivity presented by this phase
Estudo magnético e magneto-ótico do internalização de nanopartículas magnéticas biocompatíveis de γ-F e2O3 recobertas com dextrana por células tumorais de sarcoma
(Universidade Federal de Goiás, 2010) Silva, Anderson Costa da; Bakuzis, Andris Figueiroa; http://lattes.cnpq.br/3477269475651042
In this work we investigated the internalization process of magnetite nanoparticles, surface coated with dextran, by mice tumour cells of Sarcoma 180 (S180) through the tech- niques of vibrating sample magnetometer (VSM) and static magnetic birefringence (SMB). The magnetic fluid sample, stable in physiological conditions, was prepared by the coprecip- itation method. The growth of nanoparticles occurred in conjunction with the nanoparticle surface coating process by dextran. The crystal structure was confirmed by X-ray diffraction. The nanoparticles were characterized by high resolution transmission electronic microscopy. The Sturges method was used to obtain the polydispersity in diameter, which was fitted by a lognormal size distribution obtaining a modal diameter of 5.5 ± 0.1 nm and dispersity of 0.18 ± 0.02.The mice tumour cell sarcoma 180 was obtained using protocol established by the American Type Culture Collection (ATCC, Rockville, MD, USA). Studies of cytotoxicity, using the MTT method, were obtained for a nanoparticle volumetric fraction of φ = 0.00065 after one and five hours of exposure of cells S180 to the nanoparticles. In particular, we found a cellular viability of 87 ± 11 % after one hour of exposure proving that there was no appreciable cell death in the time interval in which the measurements of MAV and BME were performed. Magnetization measurements were performed to obtain the volume fraction of nanoparticles. Tests regarding the effect of centrifugation of nanoparticles suspended in cell culture medium RPMI 1640 showed a extremely low sedimentation of magnetic nanoparticles. A procedure, using a acceleration of 260×g for 10 minutes, was used to separate cells containing internalized nanoparticles from nanoparticles suspended in RPMI 1640. Measurements of magnetization of S180 cells containing nanoparticles were performed in a wide range of exposure time (100 iv minutes). Between 10 and 70 minutes the amount of nanoparticles in mass unit increased from 52 ± 20 pg/cell to 110 ± 15 pg/cell. Indeed magnetometry data indicate that the process of internalization had achieved saturation between 30 to 40 minutes. Magneto-optical technique of SMB was also used to investigate the process of inter- nalization of nanoparticles. Firstly, SMB measurements were performed in control samples consisting of magnetic nanoparticles suspended in RPMI 1640. We investigated the effects of nanoparticle concentration and aging time (related to the dynamics of nanoparticle agglom- eration). In particular, the average size of the agglomerate (Q), associated with the number of nanoparticles forming a linear chain, remained basically constant, Q = 4.8 ± 0.2 for a full- time of 70 minutes. Magnetic birefringence saturation data also remained stable in this time interval. Additionally, analysis of the measurements of SMB were also used to estimate the thickness of the coating layer (dextran), from which we found 1.70 ± 0.02 nm. Unlike VSM data, SMB measurements were obtained on samples containing both S180 cells and magnetic nanoparticles inside the RPMI medium 1640. Data were obtained in a wide range of time (120 min.). Initially it was observed that the SMB signal decreases in a time range and then increases again (between 30-40 min.). The fit of the experimental data indicate that the mag- netic birefringence saturation (∆ns) decreases in the first 30 minutes and then increases again smoothly, while the average size of the cluster has the opposite behavior, i.e. increases in the first 30 minutes and then decreases. In particular, for a exposure time, t(exp), of 10 min. the average size of the agglomerate (magnetic birefringence saturation) changed from 4.18 ± 0.04 (∆n(s) = 3.41 ± 0.02 ×1018 cm−3 min. As the birefringence saturation is proportional to the number of nanoparticles contribut- ing to the magneto-optical signal one can conclude that the decrease in the magneto-optical signal was due to the process of internalization of magnetic nanoparticles by cells S180. On the other hand, the analysis of the aging time dependence of the mean size of the agglomerate also suggests that the process of internalization occurs primarily with anisometric nanoparticles or nanostructures forming small agglomerates. Finally, after reaching saturation of the process ) to 5.22 ± 0.08 (∆ns = 2.75 ± 0.02 ×1018 cm−3 ) at texp = 30 v of nanoparticle internalization we found a formation of small agglomerates in the RPMI 1640 medium, which is responsible for the increased intensity of the magneto-optical signal, as well as the decrease of the mean size of the agglomerate for times longer than 30 minutes.
Aplicação do método de Rietveld `a determinação da distribuição de cátions em ferritas de cobalto e de magnésio
(Universidade Federal de Goiás, 2010) Nunes, Rafael Silva; Sabino, José Ricardo; http://lattes.cnpq.br/9101677399031185
We present cobalt ferrites (CoxFe3−xO4) and magnesium ferrites (MgxFe3−xO4) nanoparticles synthesized by combustion reaction and coprecipitation. The study by powder diffraction, with CuK (λ =1,5406 °A) radiation, allowed us a phase qualitative analysis, determine the lattice parameter and the crystallites average size. How Co and Fe scattering factor are close to this radiation, we also used synchrotron radiation with energies 7.038 KeV, 7.112 KeV, 7.122 KeV and 7.718 KeV. With Rietveld refinement we made a phase quantitative analysis, we found Fe2O3, MgO and MgO2 as additional phases for MgxFe3−xO4 and we found CoO and Co3O4 as additional phases for Co1,2Fe1,8O4, all obtained by combustion method. The distribution determined for all ferrites nanoparticles characterized a cubic spinel type mixed, i.e. divalent ions were found in both sites. With experiments on a vibrating sample magnetometer (VSM) we compare the saturation magnetization of our samples with the magnetization of the unit cell calculated from the distribution determined experimentally.
Condutância em nanofios magnéticos diluídos
(Universidade Federal de Goiás, 2010) Mendes, Udson Cabra; Leão, Salvino de Araújo; Avelar, Ardiley Torres; http://lattes.cnpq.br/5732286631137637
We investigate core-shell nanowires of diluted magnetic semiconductors (DMS) with remote n-type modulation doping. The incorporation of Mn2 ions acting as spin 5/2 impurities in the core region of the wire gives rise to a strong s-d exchange coupling between electrons in the wire and those of the d levels of the Mn2 ions. Applying an external magnetic eld along the axis of the wire, within the mean eld approximation, the s-d exchange generates a spin-dependent core potential. A gate voltage is applied radially to wire, to obtain some control over the density of the wire. Electronic strucutre of the wire was calculated within the e?ective mass approximation, in both approximations Hartree and spin density functional theory. We calculated the conductance of wire using the Landauer-B?uttiker formulation in the linear response regime, which generally results in a total conductance with well-de ned plateaus in GT = 2; 6; 10G0 (G0 = e2=h is the quanta of conductance), which occurred because in the system investigated the rst level is twofold degenerated (spin degenerescence) and the others are fourfold degenerated (spin degenerescence and orbital angular momentum). In the absence of a magnetic eld we observe that when we take into account the e?ects of exchange and correlation, the states with eigenvalues of Lz nonzero will be polarized while those with l = 0 isn't polarized. This unpolarized level with eigenvalue of Lz null suggests that, perhaps, the 0.7 anomaly (the emergence of two plateau at G = 0:7G0 and the other in G = G0) quantum wires on existing geometry of split-gate is related to the geometry of the wire. The results for total energy show that there are a competition between the ferromagnetic and paramagnetic states.

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