Fernando Oliveira - Profile on Academia.edu (original) (raw)
Papers by Fernando Oliveira
arXiv (Cornell University), May 2, 2008
Recent investigations call attention to the dynamics of anomalous diffusion and its connection wi... more Recent investigations call attention to the dynamics of anomalous diffusion and its connection with basic principles of statistical mechanics. We present here a short review of those ideas and their implications.
Physica A: Statistical Mechanics and its Applications, 2016
h i g h l i g h t s • We investigated fractal properties of quasiperiodic chains diluted in solve... more h i g h l i g h t s • We investigated fractal properties of quasiperiodic chains diluted in solvent. • Solvent-accessible surface area and volume was calculated for these molecules. • As demonstrated just in an infinity rigid chain the exponents tend to unity. • The molecular flexibility is fundamental for explaining the exponents obtained. • Both classes of macromolecules analyzed present a self-similar characteristic.
Frontiers in Physics, 2022
arXiv: Pattern Formation and Solitons, 2016
In this work, we investigate the pattern solutions of doubly non-local Fisher population equation... more In this work, we investigate the pattern solutions of doubly non-local Fisher population equation that include spatial kernels in both growth and competition terms. We show the existence of two types of stationary nonlinear solutions: one cosine, which we refer to as a wavelike solution and another in the form of Gaussians. We obtain analytical expressions that describe the nonlinear pattern behavior in the system and establish the stability criterion. Based on this, the pattern-no-pattern and pattern-pattern transitions are properly analyzed. We show that these pattern solutions may be related to the recently observed peak-adding phenomenon in non-linear optics.
arXiv (Cornell University), Nov 19, 2021
A computational model is proposed to investigate drug delivery systems in which erosion and diffu... more A computational model is proposed to investigate drug delivery systems in which erosion and diffusion mechanisms are participating in the drug release process. Our approach allowed us to analytically estimate the crossover point between those mechanisms through the value of the parameter b (bc = 1) and the scaling behavior of parameter τ on the Weibull function, exp[−(t/τ) b ], used to adjust drug release data in pharmaceutical literature. Numerical investigations on the size dependence of the characteristic release time τ found it to satisfy either linear or quadratic scaling relations on either erosive or diffusive regimes. Along the crossover, the characteristic time scales with the average coefficient observed on the extreme regimes (i.e., τ ∼ L 3/2), and we show that this result can be derived analytically by assuming an Arrhenius relation for the diffusion coefficient inside the capsule. Based on these relations, a phenomenological expression for the characteristic release in terms of size L and erosion rate κ is proposed, which can be useful for predicting the crossover erosion rate κc. We applied this relation to the experimental literature data for the release of acetaminophen immersed in a wax matrix and found them to be consistent with our numerical results.
Physica D: Nonlinear Phenomena, Oct 1, 2016
A lattice gas model is proposed for investigating the release of drug molecules in capsules cover... more A lattice gas model is proposed for investigating the release of drug molecules in capsules covered with semi-permeable membranes. Release patterns in one and two dimensional systems are obtained with Monte Carlo simulations and adjusted to the semi-empirical Weibull distribution function. An analytical solution to the diffusion equation is used to complement and guide simulations in one dimension. Size and porosity dependence analysis was made on the two semi-empirical parameters of the Weibull function, which are related to characteristic time and release mechanism, and our results indicate that a simple scaling law occurs only for systems with almost impermeable membranes, represented in our model by capsules with a single leaking site.
Physical Review E, 2001
In this paper we present an analysis of fragmentation of dilute polymer solutions in extensional ... more In this paper we present an analysis of fragmentation of dilute polymer solutions in extensional flow. The transition rate is investigated both from theoretical and computational approaches, where the existence of a Gaussian distribution for the breaking bonds has been controversial. We give as well an explanation for the low fragmentation frequency found in DNA experiments.
Physica D: Nonlinear Phenomena, Feb 1, 2020
A lattice gas model is proposed for investigating the release of drug molecules on devices with s... more A lattice gas model is proposed for investigating the release of drug molecules on devices with semi-permeable, porous membranes in two and three dimensions. The kinetic of this model was obtained through the analytical solution of the three-dimension diffusion equation for systems without membrane and with Monte Carlo simulations. Pharmaceutical data from drug release is usually adjusted to the Weibull function, exp[−(t/τ) b ], also known as stretched exponential, and the dependence of adjusted parameters b and τ is usually associated, in the pharmaceutical literature, with physical mechanisms dominating the drug dynamics inside the capsule. The relation of parameters τ and b with porosity λ are found to satisfy, a simple linear relation for between τ and λ −1 , which can be explained through simple physically based arguments, and a scaling relation between b and λ, with the scaling coefficient proportional to the system dimension.
arXiv: Statistical Mechanics, 2020
The Kardar-Parisi-Zhang (KPZ) equation in the d+1d + 1d+1 dimensional space has been connected to a l... more The Kardar-Parisi-Zhang (KPZ) equation in the d+1d + 1d+1 dimensional space has been connected to a large number of important stochastic processes in physics, chemistry and growth phenomena. A central quest in this field is the search for ever more precise universal growth exponents. In this work, we present physical and geometric analytical methods that directly associate these exponents to the fractal dimension of the rough interface. Based on this, we determine exactly the growth exponents for the d+1d + 1d+1 dimensions. In addition, we show that the KPZ model has no upper critical dimension.
The Kardar-Parisi-Zhang (KPZ) equation in the d+1 dimensional space has been connected with a lar... more The Kardar-Parisi-Zhang (KPZ) equation in the d+1 dimensional space has been connected with a large number of stochastic process in physics and chemistry. Therefore, the quest for its universal exponents has been a very intensive field of research. In this work using geometric analytical methods, we associate these exponents with the fractal dimension of the rough surface. Consequently, we obtain the exponents exactly for 2 + 1 dimensions and, for higher dimensions, we set theoretical limits for them. We prove as well that the KPZ model has no upper critical dimension.
Frontiers in Physics, 2021
Growth in crystals can be usually described by field equations such as the Kardar-Parisi-Zhang (K... more Growth in crystals can be usually described by field equations such as the Kardar-Parisi-Zhang (KPZ) equation. While the crystalline structure can be characterized by Euclidean geometry with its peculiar symmetries, the growth dynamics creates a fractal structure at the interface of a crystal and its growth medium, which in turn determines the growth. Recent work by Gomes-Filho et al. (Results in Physics, 104,435 (2021)) associated the fractal dimension of the interface with the growth exponents for KPZ and provides explicit values for them. In this work, we discuss how the fluctuations and the responses to it are associated with this fractal geometry and the new hidden symmetry associated with the universality of the exponents.
Physics Subject Headings (PhySH)
Recent investigations call attention to the dynamics of anomalous diffusion and its connection wi... more Recent investigations call attention to the dynamics of anomalous diffusion and its connection with basic principles of statistical mechanics. We present here a short review of those ideas and their implications.
An analytical solution for the Yukawa potential. Uma solucao analitica para o potencial de Yukawa
Cornell University - arXiv, Aug 29, 2006
A l ex H ansen D epartm ent of Physics, N orwegian U niversity of Science and Technol ogy, N {749... more A l ex H ansen D epartm ent of Physics, N orwegian U niversity of Science and Technol ogy, N {7491 Trondheim , N orway (D ated: M arch 2,2019) W e i nvesti gate vi scous and non-vi scous ow i n tw o-di m ensi onalsel f-a ne fracture joi nts through di rect num eri calsi m ul ati ons of the N avi er-Stokes equati ons. A s a novelhydrodynam i c feature of thi s ow system ,w e nd that the e ecti ve perm eabi l i ty at hi gher R eynol ds num ber to cubi c order, fal l s i nto tw o regi m es as a functi on ofthe H urst exponent h characteri zi ng the fracture joi nts. For h > 1=2, w e nd a w eak dependency w hereas for h < 1=2, the dependency i s strong. A si m i l ar behavi or i s found for the hi gher order coe ci ents. W e al so study the vel oci ty uctuati ons i n space ofa passi ve scal ar. T hese are strongl y correl ated on sm al l er l ength scal es,butdecorrel ates on l arger scal es. M oreover,the uctuati onson l argerscal e are i nsensi ti ve to theval ue ofthe R eynol dsnum ber.
Europhysics Letters (EPL), 2007
Ballistic transportation introduces new challenges in the thermodynamic properties of a gas of pa... more Ballistic transportation introduces new challenges in the thermodynamic properties of a gas of particles. For example, violation of mixing, ergodicity and of the fluctuation-dissipation theorem may occur, since all these processes are connected. In this work, we obtain results for all ranges of diffusion, i.e., both for subdiffusion and superdiffusion, where the bath is such that it gives origin to a colored noise. In this way we obtain the skewness and the non-Gaussian factor for the probability distribution function of the dynamical variable. We put particular emphasis on ballistic diffusion, and we demonstrate that in this case, although the second law of thermodynamics is preserved, the entropy does not reach a maximum and a non-Gaussian behavior occurs. This implies the non-applicability of the central limit theorem.
arXiv: Pattern Formation and Solitons, 2016
In this work, we study the pattern solutions of doubly nonlocal logistic map that include spatial... more In this work, we study the pattern solutions of doubly nonlocal logistic map that include spatial kernels in both growth and competition terms. We show that this map includes as a particular case the nonlocal Fisher-Kolmogorov equation, and we demonstrate the existence of three kinds of stationary nonlinear solutions: one uniform, one cosine type that we refer to as wavelike solution, and another in the form of Gaussian. We also obtain analytical expressions that describe the nonlinear pattern behavior in the system, and we establish the stability criterion. We define thermodynamics grandeurs such as entropy and the order parameter. Based on this, the pattern-no-pattern and pattern-pattern transitions are properly analyzed. We show that these pattern solutions may be related to the recently observed peak adding phenomenon in nonlinear optics.
Heritage of Humanity, the Brasilia's Pilot Plan has a distinctive sound ambience, atypical to... more Heritage of Humanity, the Brasilia's Pilot Plan has a distinctive sound ambience, atypical to a big city. When the urban plan was designed by Lucio Costa, noise was not an evident principle, but the adopted solutions incorporated premises that contribute with the urban acoustic comfort-like the existence of local commercial buildings and green belt, which protects the residential buildings. Scientific research carried out for UNESCO identified low percentage of people by traffic noise. However, the nocturnal noise is actually a relevant nuisance factor to the population, causing conflicts between community, bar owners and cultural producers. These annoyances emerged mainly due to the growth of nocturnal activity in Local Commercial Sectors in recent years, and due to their proximity with residential buildings of the Superblocks. By evaluating the soundscape of North Superblock 410 (SQN 410), a place of intense nocturnal activity, we sought to identify and analyze the different s...
Os ruídos gerados pela construção civil normalmente atingem níveis elevados, provocando transtorn... more Os ruídos gerados pela construção civil normalmente atingem níveis elevados, provocando transtornos e incômodos à população. É neste contexto, de contaminação acústica causado pelas construções, que se baseia o presente estudo. O objetivo principal foi avaliar o impacto sonoro causado pelo ruído da construção civil na cidade de Águas Claras, Distrito Federal. Realizou-se medidas acústicas in situ e elaborou-se cartas acústicas com os ruídos advindos de 13 obras. Das fontes de ruído identificadas destacam-se: atividades de corte e dobra de aço (setor de serralheria), confecção de fôrmas de madeiras (setor de marcenaria) e processo de concretagem. Os níveis de pressão sonora (NPS) medidos apresentaram valores acima dos limites indicados na legislação vigente e com as cartas acústicas verificou-se que as áreas residenciais, próximas às construções, estão expostas a NPS elevados. Conclui-se que as obras avaliadas provocam alterações no cenário acústico da região estudada.
arXiv (Cornell University), May 2, 2008
Recent investigations call attention to the dynamics of anomalous diffusion and its connection wi... more Recent investigations call attention to the dynamics of anomalous diffusion and its connection with basic principles of statistical mechanics. We present here a short review of those ideas and their implications.
Physica A: Statistical Mechanics and its Applications, 2016
h i g h l i g h t s • We investigated fractal properties of quasiperiodic chains diluted in solve... more h i g h l i g h t s • We investigated fractal properties of quasiperiodic chains diluted in solvent. • Solvent-accessible surface area and volume was calculated for these molecules. • As demonstrated just in an infinity rigid chain the exponents tend to unity. • The molecular flexibility is fundamental for explaining the exponents obtained. • Both classes of macromolecules analyzed present a self-similar characteristic.
Frontiers in Physics, 2022
arXiv: Pattern Formation and Solitons, 2016
In this work, we investigate the pattern solutions of doubly non-local Fisher population equation... more In this work, we investigate the pattern solutions of doubly non-local Fisher population equation that include spatial kernels in both growth and competition terms. We show the existence of two types of stationary nonlinear solutions: one cosine, which we refer to as a wavelike solution and another in the form of Gaussians. We obtain analytical expressions that describe the nonlinear pattern behavior in the system and establish the stability criterion. Based on this, the pattern-no-pattern and pattern-pattern transitions are properly analyzed. We show that these pattern solutions may be related to the recently observed peak-adding phenomenon in non-linear optics.
arXiv (Cornell University), Nov 19, 2021
A computational model is proposed to investigate drug delivery systems in which erosion and diffu... more A computational model is proposed to investigate drug delivery systems in which erosion and diffusion mechanisms are participating in the drug release process. Our approach allowed us to analytically estimate the crossover point between those mechanisms through the value of the parameter b (bc = 1) and the scaling behavior of parameter τ on the Weibull function, exp[−(t/τ) b ], used to adjust drug release data in pharmaceutical literature. Numerical investigations on the size dependence of the characteristic release time τ found it to satisfy either linear or quadratic scaling relations on either erosive or diffusive regimes. Along the crossover, the characteristic time scales with the average coefficient observed on the extreme regimes (i.e., τ ∼ L 3/2), and we show that this result can be derived analytically by assuming an Arrhenius relation for the diffusion coefficient inside the capsule. Based on these relations, a phenomenological expression for the characteristic release in terms of size L and erosion rate κ is proposed, which can be useful for predicting the crossover erosion rate κc. We applied this relation to the experimental literature data for the release of acetaminophen immersed in a wax matrix and found them to be consistent with our numerical results.
Physica D: Nonlinear Phenomena, Oct 1, 2016
A lattice gas model is proposed for investigating the release of drug molecules in capsules cover... more A lattice gas model is proposed for investigating the release of drug molecules in capsules covered with semi-permeable membranes. Release patterns in one and two dimensional systems are obtained with Monte Carlo simulations and adjusted to the semi-empirical Weibull distribution function. An analytical solution to the diffusion equation is used to complement and guide simulations in one dimension. Size and porosity dependence analysis was made on the two semi-empirical parameters of the Weibull function, which are related to characteristic time and release mechanism, and our results indicate that a simple scaling law occurs only for systems with almost impermeable membranes, represented in our model by capsules with a single leaking site.
Physical Review E, 2001
In this paper we present an analysis of fragmentation of dilute polymer solutions in extensional ... more In this paper we present an analysis of fragmentation of dilute polymer solutions in extensional flow. The transition rate is investigated both from theoretical and computational approaches, where the existence of a Gaussian distribution for the breaking bonds has been controversial. We give as well an explanation for the low fragmentation frequency found in DNA experiments.
Physica D: Nonlinear Phenomena, Feb 1, 2020
A lattice gas model is proposed for investigating the release of drug molecules on devices with s... more A lattice gas model is proposed for investigating the release of drug molecules on devices with semi-permeable, porous membranes in two and three dimensions. The kinetic of this model was obtained through the analytical solution of the three-dimension diffusion equation for systems without membrane and with Monte Carlo simulations. Pharmaceutical data from drug release is usually adjusted to the Weibull function, exp[−(t/τ) b ], also known as stretched exponential, and the dependence of adjusted parameters b and τ is usually associated, in the pharmaceutical literature, with physical mechanisms dominating the drug dynamics inside the capsule. The relation of parameters τ and b with porosity λ are found to satisfy, a simple linear relation for between τ and λ −1 , which can be explained through simple physically based arguments, and a scaling relation between b and λ, with the scaling coefficient proportional to the system dimension.
arXiv: Statistical Mechanics, 2020
The Kardar-Parisi-Zhang (KPZ) equation in the d+1d + 1d+1 dimensional space has been connected to a l... more The Kardar-Parisi-Zhang (KPZ) equation in the d+1d + 1d+1 dimensional space has been connected to a large number of important stochastic processes in physics, chemistry and growth phenomena. A central quest in this field is the search for ever more precise universal growth exponents. In this work, we present physical and geometric analytical methods that directly associate these exponents to the fractal dimension of the rough interface. Based on this, we determine exactly the growth exponents for the d+1d + 1d+1 dimensions. In addition, we show that the KPZ model has no upper critical dimension.
The Kardar-Parisi-Zhang (KPZ) equation in the d+1 dimensional space has been connected with a lar... more The Kardar-Parisi-Zhang (KPZ) equation in the d+1 dimensional space has been connected with a large number of stochastic process in physics and chemistry. Therefore, the quest for its universal exponents has been a very intensive field of research. In this work using geometric analytical methods, we associate these exponents with the fractal dimension of the rough surface. Consequently, we obtain the exponents exactly for 2 + 1 dimensions and, for higher dimensions, we set theoretical limits for them. We prove as well that the KPZ model has no upper critical dimension.
Frontiers in Physics, 2021
Growth in crystals can be usually described by field equations such as the Kardar-Parisi-Zhang (K... more Growth in crystals can be usually described by field equations such as the Kardar-Parisi-Zhang (KPZ) equation. While the crystalline structure can be characterized by Euclidean geometry with its peculiar symmetries, the growth dynamics creates a fractal structure at the interface of a crystal and its growth medium, which in turn determines the growth. Recent work by Gomes-Filho et al. (Results in Physics, 104,435 (2021)) associated the fractal dimension of the interface with the growth exponents for KPZ and provides explicit values for them. In this work, we discuss how the fluctuations and the responses to it are associated with this fractal geometry and the new hidden symmetry associated with the universality of the exponents.
Physics Subject Headings (PhySH)
Recent investigations call attention to the dynamics of anomalous diffusion and its connection wi... more Recent investigations call attention to the dynamics of anomalous diffusion and its connection with basic principles of statistical mechanics. We present here a short review of those ideas and their implications.
An analytical solution for the Yukawa potential. Uma solucao analitica para o potencial de Yukawa
Cornell University - arXiv, Aug 29, 2006
A l ex H ansen D epartm ent of Physics, N orwegian U niversity of Science and Technol ogy, N {749... more A l ex H ansen D epartm ent of Physics, N orwegian U niversity of Science and Technol ogy, N {7491 Trondheim , N orway (D ated: M arch 2,2019) W e i nvesti gate vi scous and non-vi scous ow i n tw o-di m ensi onalsel f-a ne fracture joi nts through di rect num eri calsi m ul ati ons of the N avi er-Stokes equati ons. A s a novelhydrodynam i c feature of thi s ow system ,w e nd that the e ecti ve perm eabi l i ty at hi gher R eynol ds num ber to cubi c order, fal l s i nto tw o regi m es as a functi on ofthe H urst exponent h characteri zi ng the fracture joi nts. For h > 1=2, w e nd a w eak dependency w hereas for h < 1=2, the dependency i s strong. A si m i l ar behavi or i s found for the hi gher order coe ci ents. W e al so study the vel oci ty uctuati ons i n space ofa passi ve scal ar. T hese are strongl y correl ated on sm al l er l ength scal es,butdecorrel ates on l arger scal es. M oreover,the uctuati onson l argerscal e are i nsensi ti ve to theval ue ofthe R eynol dsnum ber.
Europhysics Letters (EPL), 2007
Ballistic transportation introduces new challenges in the thermodynamic properties of a gas of pa... more Ballistic transportation introduces new challenges in the thermodynamic properties of a gas of particles. For example, violation of mixing, ergodicity and of the fluctuation-dissipation theorem may occur, since all these processes are connected. In this work, we obtain results for all ranges of diffusion, i.e., both for subdiffusion and superdiffusion, where the bath is such that it gives origin to a colored noise. In this way we obtain the skewness and the non-Gaussian factor for the probability distribution function of the dynamical variable. We put particular emphasis on ballistic diffusion, and we demonstrate that in this case, although the second law of thermodynamics is preserved, the entropy does not reach a maximum and a non-Gaussian behavior occurs. This implies the non-applicability of the central limit theorem.
arXiv: Pattern Formation and Solitons, 2016
In this work, we study the pattern solutions of doubly nonlocal logistic map that include spatial... more In this work, we study the pattern solutions of doubly nonlocal logistic map that include spatial kernels in both growth and competition terms. We show that this map includes as a particular case the nonlocal Fisher-Kolmogorov equation, and we demonstrate the existence of three kinds of stationary nonlinear solutions: one uniform, one cosine type that we refer to as wavelike solution, and another in the form of Gaussian. We also obtain analytical expressions that describe the nonlinear pattern behavior in the system, and we establish the stability criterion. We define thermodynamics grandeurs such as entropy and the order parameter. Based on this, the pattern-no-pattern and pattern-pattern transitions are properly analyzed. We show that these pattern solutions may be related to the recently observed peak adding phenomenon in nonlinear optics.
Heritage of Humanity, the Brasilia's Pilot Plan has a distinctive sound ambience, atypical to... more Heritage of Humanity, the Brasilia's Pilot Plan has a distinctive sound ambience, atypical to a big city. When the urban plan was designed by Lucio Costa, noise was not an evident principle, but the adopted solutions incorporated premises that contribute with the urban acoustic comfort-like the existence of local commercial buildings and green belt, which protects the residential buildings. Scientific research carried out for UNESCO identified low percentage of people by traffic noise. However, the nocturnal noise is actually a relevant nuisance factor to the population, causing conflicts between community, bar owners and cultural producers. These annoyances emerged mainly due to the growth of nocturnal activity in Local Commercial Sectors in recent years, and due to their proximity with residential buildings of the Superblocks. By evaluating the soundscape of North Superblock 410 (SQN 410), a place of intense nocturnal activity, we sought to identify and analyze the different s...
Os ruídos gerados pela construção civil normalmente atingem níveis elevados, provocando transtorn... more Os ruídos gerados pela construção civil normalmente atingem níveis elevados, provocando transtornos e incômodos à população. É neste contexto, de contaminação acústica causado pelas construções, que se baseia o presente estudo. O objetivo principal foi avaliar o impacto sonoro causado pelo ruído da construção civil na cidade de Águas Claras, Distrito Federal. Realizou-se medidas acústicas in situ e elaborou-se cartas acústicas com os ruídos advindos de 13 obras. Das fontes de ruído identificadas destacam-se: atividades de corte e dobra de aço (setor de serralheria), confecção de fôrmas de madeiras (setor de marcenaria) e processo de concretagem. Os níveis de pressão sonora (NPS) medidos apresentaram valores acima dos limites indicados na legislação vigente e com as cartas acústicas verificou-se que as áreas residenciais, próximas às construções, estão expostas a NPS elevados. Conclui-se que as obras avaliadas provocam alterações no cenário acústico da região estudada.