Scaling invariance of the diffusion coefficient in a family of two-dimensional Hamiltonian mappings

We consider a family of two-dimensional nonlinear area-preserving mappings that generalize the Chirikov standard map and model a variety of periodically forced systems. The action variable diffuses in increments whose phase is controlled by a negative power of the action and hence effectively uncorrelated for small actions, leading to a chaotic sea in phase space. For larger values of the action the phase space is mixed and contains a family of elliptic islands centered on periodic orbits and invariant Kolmogorov-Arnold-Moser (KAM) curves. The transport of particles along the phase space is considered by starting an ensemble of particles with a very low action and letting them evolve in the phase until they reach a certain height h. For chaotic orbits below the periodic islands, the survival probability for the particles to reach h is characterized by an exponential function, well modeled by the solution of the diffusion equation. On the other hand, when h reaches the position of periodic islands, the diffusion slows markedly. We show that the diffusion coefficient is scaling invariant with respect to the control parameter of the mapping when h reaches the position of the lowest KAM island. © 2013 American Physical Society.

An analysis of diurnal cycles in the mass of ambient aerosols derived from biomass burning and agro-industry

Strong diurnal cycles in ambient aerosol mass were observed in a rural region of Southeast Brazil where the trace composition of the lower troposphere is governed mainly by emissions from agro-industry. An optical particle counter was used to record size-segregated aerosol number concentrations between 13 May 2010 and 15 March 2011. The data were collected every 10 min and used to calculate aerosol mass concentrations. Aerosol samples were also collected onto filters during daytime (10:00-16:00 local time) and nighttime (20:00-06:00) periods, for subsequent analysis of soluble ions and water-soluble organic carbon. Biomass burning aerosols predominated during the dry winter, while secondary aerosols were most important in the summer rainy season. In both seasons, diurnal cycles in calculated aerosol mass concentrations were due to the uptake of water by the aerosols and, to a lesser extent, to emissions and secondary aerosol formation. In neither season could the observed mass changes be explained by changes in the depth of the boundary layer. In the summer, nighttime increases in aerosol mass ranged from 2.7-fold to 81-fold, depending on particle size, while in the winter, the range was narrower, from 2.2-fold to 9.5-fold, supporting the possibility that the presence of particles derived from biomass burning reduced the overall ability of the aerosols to absorb water. Key Points Diurnal cycle of agro-industrial aerosol mass governed by humidity Biomass burning emissions act to suppress particle growth Need to consider diurnal mass cycles in aerosol dry deposition models ©2013. American Geophysical Union. All Rights Reserved.

Structure and kinetics of formation of APTS/GPTS-derived organic/inorganic hybrids

The structure and the kinetics of formation of APTS/GPTS-derived organic/inorganic hybrids were studied in situ by small-angle-X-ray scattering. The data were interpreted in terms of a process of primary particles formation and growth of mass-fractal clusters. At the very early stage, the population of the nonfractal primary particles (D = 3) increases with time. As the mass-fractal clusters appear (D < 3) as a result of the aggregation process, the radius of gyration, Rg, of the clusters increases on average. At advanced stages of aggregation, the clusters grow in a mechanism in which the number of particles per clusters increases while the number of clusters diminishes with time, in such a way that the correlation volume of the clusters, Vc, fulfills the relationship Vc â̂ R g D, in agreement with a mass-fractal character of the clusters. These results supporting a cluster-cluster aggregation process, together with the typically very low value found for the mass-fractal dimension D, are in favor of a diffusion-controlled cluster aggregation mechanism. © 2013 American Chemical Society.

Dissipação via arrasto viscoso como mecanismo de supressão da aceleração de Fermi no bilhar elíptico-ovoide com fronteira dependente do tempo

Pós-graduação em Física - IGCE

Estudo dos fotoiniciadores utilizados em resinas compostas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis and photocatalytic properties of bismuth titanate with different structures via oxidant peroxo method (OPM)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A theoretical characterization of scaling properties in a bouncing ball system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Enhanced photoabsorption properties of composites of Ti/TiO2 nanotubes decorated by Sb2S3 and improvement of degradation of hair dye

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

On the shock performance of a nonlinear vibration isolator with high-static-low-dynamic-stiffness

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fluid-dynamic assessment of sugarcane bagasse to use as feedstock in bubbling fluidized bed gasifiers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Gestão ambiental aplicada a prevenção, controle e recuperação de erosão linear acelerada no município de Ipeúna-SP

The erosion is a natural process of detachment, transport and deposition of soil and rock particles from one place to another. Human activities with no previous planning may accelerate this process, causing several damages to the environment and to society. In order to control the acceleration of these erosion processes caused by humans, prevention and improvement initiatives emerge. Regarding works which interfere directly in some of the natural resources, these initiatives must respect the intrinsic physical properties of the area of interest, if they aim to obtain effective results. Based on this scenario, this work proposes a few methods of accelerated linear erosion prevention, control and recovery in a specific area of the municipal district of Ipeúna (SP). For that matter, this study is based on a method of physiographic compartmentalization of the area, considering and integrating soil, relief, geology and the use and land cover properties of the study area. Plus, a flowchart with general orientations regarding management of eroded areas was produced, focused on the control and recovery of linear erosion. The result demonstrates the importance of careful erosion control, respecting the physical properties of each physiographic unit. The vegetative and mechanical conservationists methods, and the discipline of water flow, have found wide applicability in the study area.

Structural and functional characterization of barium zirconium titanate/epoxy composites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and characterization of NaNbO3 mesostructure by a microwave-assisted hydrothermal method

In the present work, we report the synthesis and characterization of NaNbO3 particles obtained by microwave-assisted hydrothermal method from Nb2O5 and NaOH. The synthesis was made at different periods at 180 °C and 300W. The crystallization of NaNbO3 structures produced Na2Nb2O6.H2O in the intermediate phase with fiber-like morphology, and this is associated with the synthesis time. Pure orthorhombic NaNbO3 with cube-like morphology originates after synthesizing for 240 minutes. To verify the remnant polarization of particles, films were obtained by electrophoresis process and sintered at 800°C for 10 minutes in a microwave furnace. The films characterization indicated that films of niobate with fiber-like morphology present remaining polarization, and the morphology of cubes did not show remaining polarization. Considering these results, it can be concluded that the morphology implemented ferroelectric property of NaNbO3.

Cytotoxicity of resin-based luting cements to pulp cells

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nicotine-enhanced oxidation of low-density lipoprotein and its components by myeloperoxidase/H2O2/Cl- system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)