Characterization of natural rubber membranes using scaling laws analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Scaling properties of the regular dynamics for a dissipative bouncing ball model

Some scaling properties of the regular dynamics for a dissipative version of the one-dimensional Fermi accelerator model are studied. The dynamics of the model is given in terms of a two-dimensional nonlinear area contracting map. Our results show that the velocities of saddle fixed points (saddle velocities) can be described using scaling arguments for different values of the control parameter. (c) 2007 Elsevier B.V. All rights reserved.

A theoretical characterization of scaling properties in a bouncing ball system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Universal aspects of light halo nuclei

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

Phase Transition in Dynamical Systems: Defining Classes of Universality for Two-Dimensional Hamiltonian Mappings via Critical Exponents

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Suppressing Fermi acceleration in two-dimensional driven billiards

We consider a dissipative oval-like shaped billiard with a periodically moving boundary. The dissipation considered is proportional to a power of the velocity V of the particle. The three specific types of power laws used are: (i) F proportional to-V; (ii) F proportional to-V-2 and (iii) F proportional to-V-delta with 1 < delta < 2. In the course of the dynamics of the particle, if a large initial velocity is considered, case (i) shows that the decay of the particle's velocity is a linear function of the number of collisions with the boundary. For case (ii), an exponential decay is observed, and for 1 < delta < 2, an powerlike decay is observed. Scaling laws were used to characterize a phase transition from limited to unlimited energy gain for cases (ii) and (iii). The critical exponents obtained for the phase transition in the case (ii) are the same as those obtained for the dissipative bouncer model. Therefore near this phase transition, these two rather different models belong to the same class of universality. For all types of dissipation, the results obtained allow us to conclude that suppression of the unlimited energy growth is indeed observed.

In-flight and collisional dissipation as a mechanism to suppress Fermi acceleration in a breathing Lorentz gas

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

Influence of solution treatment on the adsorption and morphology of poly(o-methoxyaniline) layer-by-layer films

It is shown that the adsorption and morphological properties of layer-by-layer films of poly(o-methoxyaniline) (POMA) alternated with poly(vinyl sulfonic acid) (PVS) are affected dramatically by different treatments of the POMA solutions employed to prepare the films. Whereas the dimension of the globular structures seen by atomic force microscopy increases non monotonically during film growth in parent POMA solution, owing to a competition of adsorption/desorption processes, it changes monotonically for the fractionated POMA. The roughness of the latter films depends on the concentration of the solution and saturates at a given size of the scan window. This allowed us to apply scaling laws that indicated a self-affine mechanism for adsorption of the treated POMA.

Locating invariant tori for a family of two-dimensional Hamiltonian mappings

The location of invariant tori for a two-dimensional Hamiltonian mapping exhibiting mixed phase space is discussed. The phase space of the mapping shows a large chaotic sea surrounding periodic islands and limited by a set of invariant tori. Given the mapping considered is parameterised by an exponent γ in one of the dynamical variables, a connection with the standard mapping near a transition from local to global chaos is used to estimate the position of the invariant tori limiting the size of the chaotic sea for different values of the parameter γ. © 2011 Elsevier B.V. All rights reserved.

Critical adsorption of polyelectrolytes onto charged Janus nanospheres

Based on extensive Monte Carlo simulations and analytical considerations we study the electrostatically driven adsorption of flexible polyelectrolyte chains onto charged Janus nanospheres. These net-neutral colloids are composed of two equally but oppositely charged hemispheres. The critical binding conditions for polyelectrolyte chains are analysed as function of the radius of the Janus particle and its surface charge density, as well as the salt concentration in the ambient solution. Specifically for the adsorption of finite-length polyelectrolyte chains onto Janus nanoparticles, we demonstrate that the critical adsorption conditions drastically differ when the size of the Janus particle or the screening length of the electrolyte are varied. We compare the scaling laws obtained for the adsorption-desorption threshold to the known results for uniformly charged spherical particles, observing significant disparities. We also contrast the changes to the polyelectrolyte chain conformations close to the surface of the Janus nanoparticles as compared to those for simple spherical particles. Finally, we discuss experimentally relevant physicochemical systems for which our simulations results may become important. In particular, we observe similar trends with polyelectrolyte complexation with oppositely but heterogeneously charged proteins.

Termodinâmica do modelo Bouncer: um gás unidimensional simplificado

Pós-graduação em Física - IGCE

DE SITTER TRANSITIVITY, CONFORMAL TRANSFORMATIONS AND CONSERVATION LAWS

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

New laws for author's rights: adequate for digital preservation?

Introduction. Besides technical and economic-organisational problems, digital preservation also faces legal issues, especially regarding copyright legislation, since all digital preservation strategies involve copying materials and/or using software which is typically copyrighted. The purpose of this paper is to ascertain the extent to which current copyright laws meet the preservation requirements of library materials..Methodology. A cross-sectional analysis of recently updated national copyright laws as well as the impact of the other two protection methods: contractual and technological.Results. Even after the latest updates current copyright legislation is almost useless for digital preservation activities since the opportunities provided by WIPO Copyright Treaty to adapt and extend copyright exceptions and limitations have been used to the full.Conclusion. We need a legislation reform that will make it possible to carry out all required copying and communication activities and software use, even if circumventing technological protection is needed. But that is not enough for licensed works. The best solution for this kind of work is to include specific clauses in the licences that facilitate preservation activities. Thus, cooperation between both parties, libraries and rights' holders, is essential.

Library exceptions in the copyright laws of Ibero-American countries

The development of the digital setting has made it absolutely necessary to revise copyright legislation as a whole, including the exceptions that benefit libraries and similar institutions. Unfortunately, adaptation to the new technological reality is not taking place satisfactorily in most countries - the predominating trend is a refortification of copyright as opposed to user interests, and the maintenance of a certain pre-digital philosophy. In the case of Ibero-America the problem is twofold: aside from obsolescence or a lack of adaptation to the new technological setting, there are countries that have not yet included library-related exceptions in the national laws. Moreover, these happen to be developing countries, whose needs and interests do not coincide with those of the richer nations who paved the path to be followed by international treaties and copy- or copyright agreements. This study looks into the situation of exceptions to copyright to benefit libraries in the countries constituting Ibero-America, with a comparative analysis of the most significant characteristics of their national laws. It is concluded that it is crucial for these countries to take advantage of the options offered through the WIPO Copyright Treaty of 1996 and the results of the WIPO Development Agenda to update their legislation, in order that copyright will be respected, while at the same time making it easier for libraries to continue carrying out their social function in an adequate manner, always with the understanding of the developmental context of these countries.

Scaling-Up of Dental Pulp Stem Cells Isolated from Multiple Niches

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