... doi.org/10.1002/9781118786352.wbieg0268Fábio D. A. Aarão Reis, Susan L. Brantley Models of transport and reaction ...
Tópico(s): Geology and Paleoclimatology Research
1909 - University of Chicago Press | The Journal of Geology
Produção Nacional
Revisado por pares
T. G. Mattos, F. D. A. Aarão Reis,
We study a model for unimolecular reaction on a supported catalyst including reactant diffusion and desorption, using analytical methods and scaling concepts. For rapid reactions, enhancing surface diffusion or increasing particle size favors the flux of reactants to the catalyst particles, which increases the turnover frequency (TOF). The reactant flux towards the support becomes dominant when the ratio of diffusion lengths in the catalyst and in the support exceeds a critical value. A peak in the ...
Tópico(s): Catalysts for Methane Reforming
2009 - Elsevier BV | Journal of Catalysis
Produção Nacional
Anna Chame, F. D. A. Aarão Reis,
We simulated a growth model in (1+1) dimensions in which particles are aggregated according to the rules of ballistic deposition with probability p or according to the rules of random deposition with surface relaxation (Family model) with probability 1-p. For any p>0, this system is in the Kardar-Parisi-Zhang (KPZ) universality class, but it presents a slow crossover from the Edwards-Wilkinson class (EW) for small p. From the scaling of the growth velocity, the parameter p is connected to the coefficient ...
Tópico(s): Material Dynamics and Properties
2002 - American Physical Society | Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics
Produção Nacional
Revisado por pares
Abstract Considering some deposition models with limited mobility, we show that the typical decay of the interface width to its saturation value is exponential, which defines the crossover or saturation time τ . We present a method to calculate a characteristic time τ 0 proportional to τ and estimate the dynamical exponent z. In one-dimensional substrates of lengths L ⩽2048, the method is applied to the Family model, the restricted solid-on-solid (RSOS) model and the ballistic deposition. Effective ...
Tópico(s): Material Dynamics and Properties
2002 - Elsevier BV | Physica A Statistical Mechanics and its Applications
Produção Nacional
We study a lattice model for etching of a crystalline solid including the deposition of a poisoning species. The model considers normal and lateral erosion of the columns of the solid by a flux of etching particles and the blocking effects of impurities formed at the surface. As the probability p of formation of this poisoning species increases, the etching rate decreases and a continuous transition to a pinned phase is observed. The transition is in the directed percolation (DP) class, with the ...
Tópico(s): Material Dynamics and Properties
2003 - American Physical Society | Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics
Produção Nacional
Tiago J. Oliveira, F. D. A. Aarão Reis,
Maximal- and minimal-height distributions (MAHD, MIHD) of two-dimensional interfaces grown with the nonlinear equations of Kardar-Parisi-Zhang (KPZ, second order) and of Villain-Lai-Das Sarma (VLDS, fourth order) are shown to be different. Two universal curves may be MAHD or MIHD of each class depending on the sign of the relevant nonlinear term, which is confirmed by results of several lattice models in the KPZ and VLDS classes. The difference between MAHD and MIDH is connected with the asymmetry ...
Tópico(s): Fluid Dynamics and Turbulent Flows
2008 - American Physical Society | Physical Review E
Produção Nacional
Vladimir G. Miranda, F. D. A. Aarão Reis,
We integrate numerically the Kardar-Parisi-Zhang (KPZ) equation in $1+1$ and $2+1$ dimensions using a Euler discretization scheme and the replacement of ${(\ensuremath{\nabla}h)}^{2}$ by exponentially decreasing functions of that quantity to suppress instabilities. When applied to the equation in $1+1$ dimensions, the method of instability control provides values of scaling amplitudes consistent with exactly known results, in contrast to the deviations generated by the original scheme. In $2+1$ dimensions, ...
Tópico(s): Stochastic processes and statistical mechanics
2008 - American Physical Society | Physical Review E
Produção Nacional
Revisado por pares
Patrícia de Fátima dos Santos Teixeira, Vaneska Spinelli Reuters, Márcia Martins Ferreira, Cloyra Paiva Almeida, Fabíola Alves Aarão Reis, Alexandru Buescu, Antônio José Leal Costa, Mário Vaisman,
The aim of this study was to evaluate the lipid profile of patients with different degrees of hypothyroidism and the effect of levothyroxine replacement in subclinical hypothyroidism (SH). Initially, a cross-sectional study was performed with 226 participants [SH = 133 participants, manifest hypothyroidism (MH) = 23 participants, and euthyroidism (EU) = 70 participants]. The mean levels of atherogenic lipid variables were greater in MH than in SH and were greater in SH than in EU, although the differences ...
Tópico(s): Pituitary Gland Disorders and Treatments
2008 - Elsevier BV | Translational research
Produção Nacional
We study dynamic scaling in a model with collective diffusion (CD) of isolated atoms in terraces and irreversible aggregation at step edges. Simulations are performed in two-dimensional substrates with several diffusion to deposition ratios R identical with D/F. Data collapse of scaled roughness distributions confirms that this model is in the class of the fourth-order nonlinear growth equation by Villain, Lai, and Das Sarma (VLDS) with negligible finite-size effects, while estimates of scaling exponents ...
Tópico(s): nanoparticles nucleation surface interactions
2010 - American Physical Society | Physical Review E
Produção Nacional
Revisado por pares
Depois de propor uma reflexão sobre as relações entre Memória e História, o artigo discute uma série de questões relativas à Lei da Anistia (aprovada, no Brasil, em agosto de 1979), e aos silêncios que ela estabeleceu: sobre a tortura e os torturadores, sobre o apoio da sociedade à ditadura e sobre os projetos revolucionários de esquerda. O texto defende a necessidade da revisão da lei porque um debate a respeito poderia ajudar a sociedade brasileira a compreender melhor o período ditatorial, a tortura ...
Tópico(s): Historical and Contemporary Political Dynamics
2010 - FUNDAÇÃO GETÚLIO VARGAS | Estudos Históricos (Rio de Janeiro)
Produção Nacional
Revisado por pares
Tiago J. Oliveira, F. D. A. Aarão Reis,
We study the local and global roughness scaling in growth models with grains at the film surfaces. The local roughness, measured as a function of window size r, shows a crossover at a characteristic length rc, from a rapid increase with exponent α1 to a slower increase with exponent α2. The result α1≈1 is explained by the large height differences in the borders of the grains when compared to intragrain roughness, and must not be interpreted as a consequence of a diffusion dominated intragrain dynamics. ...
Tópico(s): Stochastic processes and statistical mechanics
2007 - American Institute of Physics | Journal of Applied Physics
Produção Nacional
Cloyra Almeida, Mário Vaisman, Antônio José Leal Costa, Fabíola Alves Aarão Reis, Vaneska Spinelli Reuters, Patrícia de Fátima dos Santos Teixeira, Márcia Serra Ferreira, Letícia B. B. de M. Teixeira, Glória R.B. de Araújo, Marco Antônio Alves Brasil,
Neuropsychological changes are still controversial in patients with subclinical hypothyroidism (SH). The objective of this study is to assess these changes.Cross-sectional study comparing the results of the neurocognitive evaluation of 65 SH patients and 31 individuals without thyroid disease. Subclinical hypothyroidism was defined as at least two elevated serum TSH levels (> 4 microUI/ml) with normal serum free T4 levels (0.9-1.8 ng/dl). The participants underwent the following neuropsychological assessment: ...
Tópico(s): Pituitary Gland Disorders and Treatments
2007 - Editora da Universidade de São Paulo | Arquivos Brasileiros de Endocrinologia & Metabologia
Produção Nacional
Revisado por pares
Cloyra Almeida, Marco Antônio Alves Brasil, Antônio José Leal Costa, Fabíola Alves Aarão Reis, Vaneska Spinelli Reuters, Patrícia de Fátima dos Santos Teixeira, Márcia Serra Ferreira, Amanda M Marques, Bianca A Melo, Letícia B. B. de M. Teixeira, Alexandre Buescu, Mário Vaisman,
OBJECTIVE: To evaluate the prevalence of psychiatric disorders and symptoms in patients with subclinical hypothyroidism. METHOD: Ninety-four outpatients with at least two elevated serum thyrotrophin levels (> 4 µU/ml) and normal FT4, and 43 euthyroid outpatients, both groups from HUCFF-UFRJ, were evaluated. Psychiatric diagnosis was based on the Structured Clinical Interview Diagnostic for the DSM-IV axis I (SCID-I/DSM-IV), the psychopathological symptoms on Hamilton anxiety and depression scales, and ...
Tópico(s): Ion channel regulation and function
2007 - Associação Brasileira de Psiquiatria | Brazilian Journal of Psychiatry
Produção Nacional
F. A. Silveira, F. D. A. Aarão Reis,
We study roughness scaling of the outer surface and the internal porous structure of deposits generated with the three-dimensional bidisperse ballistic deposition (BBD), in which particles of two sizes are randomly deposited. Systematic extrapolation of roughness and dynamical exponents and the comparison of roughness distributions indicate that the top surface has Kardar-Parisi-Zhang (KPZ) scaling for any ratio $F$ of the flux between large and small particles. A scaling theory predicts the characteristic ...
Tópico(s): Material Dynamics and Properties
2007 - American Physical Society | Physical Review E
Produção Nacional
F. D. A. Aarão Reis, J. Stafiej,
We study a simple model for metal corrosion controlled by the reaction rate of the metal with an anionic species and the diffusion of that species in the growing passive film between the solution and the metal. A crossover from the reaction-controlled to the diffusion-controlled growth regime with different roughening properties is observed. Scaling arguments provide estimates of the crossover time and film thickness as functions of the reaction and diffusion rates and the concentration of anionic ...
Tópico(s): Fluid Dynamics and Thin Films
2007 - American Physical Society | Physical Review E
Produção Nacional
Tiago J. Oliveira, F. D. A. Aarão Reis,
We study numerically finite-size corrections in scaling relations for roughness distributions of various interface growth models. The most common relation, which considers the average roughness as a scaling factor, is not obeyed in the steady states of a group of ballisticlike models in 2+1 dimensions, even when very large system sizes are considered. On the other hand, good collapse of the same data is obtained with a scaling relation that involves the root mean square fluctuation of the roughness, ...
Tópico(s): Complex Network Analysis Techniques
2007 - American Physical Society | Physical Review E
Produção Nacional
Revisado por pares
Marilia F. Alamini, R.C. da Silva, Vinícius C. Zoldan, E.A. Isoppo, Ubirajara Pereira Rodrigues Filho, F. D. A. Aarão Reis, Aloı́sio Nelmo Klein, André A. Pasa,
Electrochemical deposition of Prussian Blue shows a time increase of adsorption rate and produces films with faceted surfaces and smooth morphology at short length scales. Roughness scaling suggests anomalous roughening. However, an interpretation of normal Family–Vicsek scaling provides exponents consistent with roughening dominated by surface diffusion and time-dependent deposition rate characteristic of electrodeposition.
Tópico(s): Corrosion Behavior and Inhibition
2011 - Elsevier BV | Electrochemistry Communications
Produção Nacional
Tiago J. Oliveira, F. D. A. Aarão Reis,
In surfaces with grainy features, the local roughness $w$ shows a crossover at a characteristic length $r_c$, with roughness exponent changing from $\alpha_1\approx 1$ to a smaller $\alpha_2$. The grain shape, the choice of $w$ or height-height correlation function (HHCF) $C$, and the procedure to calculate root mean-square averages are shown to have remarkable effects on $\alpha_1$. With grains of pyramidal shape, $\alpha_1$ can be as low as 0.71, which is much lower than the previous prediction 0.85 for rounded ...
Tópico(s): Surface and Thin Film Phenomena
2011 - American Physical Society | Physical Review E
Produção Nacional
Tiago J. Oliveira, F. D. A. Aarão Reis,
Island size and capture zone distributions (ISDs, CZDs) are studied numerically in submonolayer growth with various critical island sizes and shapes. CZDs scaled by the variance show excellent agreement with the Wigner surmise, confirming the Pimpinelli-Einstein approach for large CZs/large island dynamics. The ISDs decay as $\mathrm{exp}(\ensuremath{-}{s}^{\ensuremath{\gamma}})$, with $\ensuremath{\gamma}=4$, $\ensuremath{\approx}$$2.4$, and $2$ for point, fractal, and square islands, respectively. A scaling ...
Tópico(s): Oceanographic and Atmospheric Processes
2011 - American Physical Society | Physical Review B
Produção Nacional
Revisado por pares
Patrícia de Fátima dos Santos Teixeira, Vaneska Spinelli Reuters, Cloyra Paiva Almeida, Márcia Martins Ferreira, Márcia Branco Wagman, Fabíola Alves Aarão Reis, Antônio José Leal Costa, Mário Vaisman,
OBJETIVO: Analisar e correlacionar características clínicas, sintomas psiquiátricos e dados laboratoriais no hipotireoidismo subclínico (HS). MÉTODOS: Estudo transversal comparando achados de 103 pacientes com HS aos de 60 indivíduos eutireoidianos. A avaliação clínica e a psiquiátrica foram baseadas, respectivamente, na escala de Zulewski e nos questionários de Hamilton A, Hamilton D e Beck. Todos foram submetidos a dosagens de tireotropina (TSH), T4 livre e antitireoperoxidase (ATPO). Variáveis contínuas ...
Tópico(s): Retinoids in leukemia and cellular processes
2006 - Brazilian Medical Association | Revista da Associação Médica Brasileira
Produção Nacional
Revisado por pares
Thereza Paiva, F. D. A. Aarão Reis,
We study height and roughness distributions of films grown with discrete Kardar–Parisi–Zhang (KPZ) models in a small time regime which is expected to parallel the typical experimental conditions. Those distributions are measured with square windows of sizes 8 ⩽ r ⩽ 128 gliding through a much larger surface. Results for models with weak finite-size corrections indicate that the absolute value of the skewness and the value of the kurtosis of height distributions converge to 0.2 ⩽ ∣S∣ ⩽ 0.3 and 0 ⩽ Q ⩽ 0.5, respectively. ...
Tópico(s): Complex Systems and Time Series Analysis
2006 - Elsevier BV | Surface Science
Produção Nacional
In systems where deposition rates are high compared to diffusion, desorption, and other mechanisms that generate correlations, a crossover from random to correlated growth of surface roughness is expected at a characteristic time t0. This crossover is analyzed in lattice models via scaling arguments, with support from simulation results presented here and in other works. We argue that the amplitudes of the saturation roughness and of the saturation time t(x) scale as t0(1/2) and t0, respectively. ...
Tópico(s): Material Dynamics and Properties
2006 - American Physical Society | Physical Review E
Produção Nacional
Revisado por pares
F. D. A. Aarão Reis, J. Stafiej, J. P. Badiali,
We study a model for corrosion and passivation of a metallic surface after small damage of its protective layer using scaling arguments and simulation. We focus on the transition between an initial regime of slow corrosion rate (pit nucleation) to a regime of rapid corrosion (propagation of the pit), which takes place at the so-called incubation time. The model is defined in a lattice in which the states of the sites represent the possible states of the metal (bulk, reactive, and passive) and the solution ( ...
Tópico(s): Concrete Corrosion and Durability
2006 - American Chemical Society | The Journal of Physical Chemistry B
Produção Nacional
Tiago J. Oliveira, K. Dechoum, José Arnaldo Redinz, F. D. A. Aarão Reis,
We study a restricted solid-on-solid model involving deposition and evaporation with probabilities p and 1 - p, respectively, in one-dimensional substrates. It presents a crossover from Edwards-Wilkinson (EW) to Kardar-Parisi-Zhang (KPZ) scaling for p approximately 0.5. The associated KPZ equation is analytically derived, exhibiting a coefficient lambda of the nonlinear term proportional to q identical with p - 1/2, which is confirmed numerically by calculation of tilt-dependent growth velocities for ...
Tópico(s): Material Dynamics and Properties
2006 - American Physical Society | Physical Review E
Produção Nacional
Tiago J. Oliveira, F. D. A. Aarão Reis,
Simulations of irreversible growth of extended (fractal and square) islands with critical island sizes i=1 and 2 are performed in broad ranges of coverage \theta and diffusion-to-deposition ratios R in order to investigate scaling of island size and capture zone area distributions (ISD, CZD). Large \theta and small R lead to a crossover from the CZD predicted by the theory of Pimpinelli and Einstein (PE), with Gaussian right tail, to CZD with simple exponential decays. The corresponding ISD also cross ...
Tópico(s): Spectroscopy and Quantum Chemical Studies
2012 - American Physical Society | Physical Review B
Produção Nacional
Revisado por pares
F. D. A. Aarão Reis, R. Riera,
Tópico(s): Stochastic processes and statistical mechanics
1993 - Springer Science+Business Media | Journal of Statistical Physics
Produção Nacional
Revisado por pares
In order to estimate roughness exponents of interface growth models, we propose the calculation of effective exponents from the roughness fluctuation (sigma) in the steady state. We compare the finite-size behavior of these exponents and the ones calculated from the average roughness for two models in the 2+1-dimensional Kardar-Parisi-Zhang (KPZ) class and for a model in the 1+1-dimensional Villain-Lai-Das Sarma (VLDS) class. The values obtained from sigma provide consistent asymptotic estimates, eventually ...
Tópico(s): nanoparticles nucleation surface interactions
2005 - Elsevier BV | Physica A Statistical Mechanics and its Applications
Produção Nacional
We analyze the shapes of roughness distributions of discrete models in the Kardar, Parisi, and Zhang (KPZ) and in the Villain, Lai, and Das Sarma (VLDS) classes of interface growth, in one and two dimensions. Three KPZ models in $d=2$ confirm the expected scaling of the distribution and show a stretched exponential tail approximately as $\mathrm{exp}(\ensuremath{-}{x}^{0.8})$, with a significant asymmetry near the maximum. Conserved restricted solid-on-solid models belonging to the VLDS class were simulated ...
Tópico(s): Material Dynamics and Properties
2005 - American Physical Society | Physical Review E
Produção Nacional
Revisado por pares
Tópico(s): Mathematical Dynamics and Fractals
1996 - Elsevier BV | Physics Letters A
Produção Nacional
F. D. A. Aarão Reis, S. L. A. de Queiroz, Raimundo R. dos Santos,
We address the issue of universality in two-dimensional disordered Ising systems, by considering long, finite-width strips of ferromagnetic Ising spins with randomly distributed couplings. We calculate the free energy and spin-spin correlation functions (from which averaged correlation lengths, $\xi^{ave}$, are computed) by transfer-matrix methods. An {\it ansatz} for the size-dependence of logarithmic corrections to $\xi^{ave}$ is proposed. Data for both random-bond and site-diluted systems show that ...
Tópico(s): Opinion Dynamics and Social Influence
1996 - American Physical Society | Physical review. B, Condensed matter