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Interference of robust tori on the resonance overlapEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We study a dynamical system which describes the overlap of resonances in a global integrable context and we present a new topological scenario for the reconnection of three resonance island chains in the presence of two robust tori. These tori induce this new scenario and they play the role of transport barriers which are relevant for plasma confinement in Tokamaks. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Inter hydrogen bonded complexes of hexadecylaniline and alkoxy benzoic acids: a study of crystallization kineticsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A systematic crystallization kinetic study of two smectogens of homologous series of the inter molecular hydrogen bonded between undecyl, dodecyl benzoic acids and hexadecylaniline complexes viz., 16A+11BA and 16A+12BA respectively has been carried out by thermal microscopy, differential scanning calorimetry (DSC) and dielectric studies. FTIR studies indicate the formation of hydrogen bond in these complexes. The crystallization kinetics was studied by two techniques viz., the traditional thermal analysis (DSC) and electrical studies in which capacitance and dielectric loss variation with temperature were recorded and anal...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

A simple way to avoid metastable configurations in the density-matrix renormalization-group algorithmsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We use the spin-1 Heisenberg chain with periodic boundary conditions to ilustrate that the systems get stuck in metastable configurations only when the density-matrix renormalization-group algorithm start with small number of states m. We also show that the convergence of the energies have a huge improvement if we start the algorithm with a large number of states m. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

MOND virial theorem applied to a galaxy clusterEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Large values for the mass-to-light ratio (Ò) in self-gravitating systems is one of the most important evidences of dark matter. We propose a expression for the mass-to-light ratio in spherical systems using MOND. Results for the COMA cluster reveal that a modification of the gravity, as proposed by MOND, can reduce significantly this value. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

The spin dynamics of molecular magnets beyond Kubo's linear response theoryEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The description of quantum dynamics of nanomagnets is a central issue in most applications proposed for those systems. In this paper, we put forward a modified perturbation approach to study the spin dynamics of a molecular magnet in the presence of time-dependent magnetic fields.The non-perturbed Hamiltonian H0, which defines the interaction picture, may be time-dependent proviso it can be diagonalized at all times by the same basis of states. We probe the method using a simple model Hamiltonian, that contains the important anisotropy terms relevant for Fe8 molecular clusters, and solve as an example the case with the sma...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

EPR study of gamma induced radicals in amino and iminodiacetic acid derivativesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, electron paramagnetic resonance spectroscopy was used to investigate free radicals formed in gamma irradiated L-glutamine hydrochloride, iminodiacetic acid hydrochloride and N-(2-hyroxyethyl) iminodiacetic acid powders. The free radicals produced in L-glutamine hydrochloride powders were attributed to the CH2CHCOOH radical; and those in iminodiacetic acid hydrochloride and N-(2-hyroxyethyl) iminodiacetic acid powders to the HNCHCH2(COOH)2 and HOCH2CH2NCHCH2(COOH)2, respectively. The g-values of the radicals and the hyperfine structure constants of the free electron with the environmental protons and 14N nucl...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Implications of a decay law for the cosmological constant in higher dimensional cosmology and cosmological wormholesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Higher dimensional cosmological implications ofa decay law for the cosmological constant term are analyzed. Three independent cosmological models are explored mainly: 1) - In the first model, the effective cosmological constant was chosen to decay with times like Λeffective = Ca-2 + D(b/a i)² where aiis an arbitrary scale factor characterizing the isotropic epoch which proceeds the graceful exit period. Further, the extra-dimensional scale factor decays classically like b(t) ≈ a x (t),xisareal negative number. 2) - In the second model, we adopt in addition to Λeffective = Ca-2 + D(b/a i)² the phenomenological law b(t...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

GUP and higher dimensional Reissner-Nordström black hole radiationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Based on the generalized uncertainty principle (GUP), in which the quantum gravitational effects are taken in to account, the corrected Beckenstein-Hawking entropy of the higher dimensional Reissner-Nordström black hole, up to the square order of Planck length, is calculated. Using the corrected entropy, the black hole radiation probability is calculated in the tunneling formalism, which is corrected up to the same order of the Planck length and shows a more probable quantum tunneling. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Angiogenic properties of natural rubber latex biomembranes and the serum fraction of Hevea brasiliensisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The angiogenic properties of natural rubber were evaluated in this work. We have used the chick chorioallantoic membrane assay (CAM) as a model to investigate the influence of the heating on biological activity in rubber membranes and in non rubber fraction as well. Results showed that natural rubber membranes can induce vascularization. It was observed that angiogenesis activity was maximum when membranes were heated in temperatures between 65ºC and 85ºC, considering a range from 55ºC to 105ºC. The same behavior was observed for non rubber fraction and it indicates that this serum fraction may be responsible for angio...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Gupta-Bleuler quantization for massive and massless free vector fieldsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
It is shown that the usual quantum field theory leads to an ultraviolet divergence in the vacuum energies and an infrared divergence in the two-point functions of the massive and massless vector fields. Using a new method of quantization it is shown that the vacuum energies converge, and the normal ordering procedure is not necessary. Also the propagators are calculated, which are automatically renormalied. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Characteristics of austenitic stainless steel nitrided in a hybrid glow discharge plasmaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A nitriding process based on two distinct nitrogen glow discharge modes, with sample temperatures ranging from 380 0C to 480 0C, was employed to treat the surface of austenitic stainless steel (SS 304). The temperature is controlled exclusively by switching the operation conditions of the discharges. First mode of operation is the conventional one, named cathodic, which runs at higher pressure values (1 mbar) in comparison to the second mode, named anodic, which runs at the pressure range of 10-3 - 10-2 mbar. Cathodic mode is used to quickly heat the sample holder, by the high ion flux. On the other hand, in the anodic mod...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

A 3-D four-wing attractor and its analysisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper, several three dimensional (3-D) four-wing smooth quadratic autonomous chaotic systems are analyzed. It is shown that these systems have a number of similar features. A new 3-D continuous autonomous system is proposed based on these features. The new system can generate a four-wing chaotic attractor with less terms in the system equations. Several basic properties of the new system is analyzed by means of Lyapunov exponents, bifurcation diagrams and Poincare maps. Phase diagrams show that the equilibria are related to the existence of multiple wings. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Annealing time effect on the properties of CuInSe2 grown by electrodeposition using two electrodes systemEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper, we report the effect of annealing time on the properties of copper indium diselenide CuInSe2 films. The CuInSe2 thin films have been grown at room temperature by electrochemical deposition technique using two electrodes system. The as deposited films were annealed under argon atmosphere at 300 ºC during 15, 30, 45 and 60 min. The structural and morphological properties of the resulting films were characterized respectively by means of x-ray diffraction (XRD) and scanning electron microscopy (SEM). The optical band gap was estimated from transmittance measurements. We have found, that after annealing, all fi...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Sequential and double sequential fission observed in heavy ion interaction Of (11.67 MeV/u)197Au projectile with 197Au targetEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The heavy ion interaction of 11.67 MeV/u 197Au + 197Au has been investigated using mica as a passive detector. By employing Solid State Nuclear Track Detection Technique the data of elastic scattering as well as inelastic reaction channel was collected. The off-line data analysis of multi-pronged events was performed by measuring the three-dimensional geometrical coordinates of correlated tracks on event-by-event basis. Multi-pronged events observed in this reaction were due to sequential and double sequential fission. Using a computer code PRONGY based on the procedure of internal calibration, it was possible to derive qu...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Coherent vorticity extraction in 3D homogeneous isotropic turbulence: influence of the Reynolds number and geometrical statisticsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The coherent vorticity extraction method (CVE) is based on the nonlinear filtering of the vorticity field projected onto an orthonormal wavelet basis made of compactly supported functions. CVE decomposes each turbulent flow realization into two orthogonal components: a coherent and an incoherent random flow. They both contribute to all scales in the inertial range, but exhibit different statistical behavior. We apply CVE to 256³ subcubes extracted from 3D homogeneous isotropic turbulent flows at different Taylor microscale Reynolds numbers (R»= 140,240 and 680), computed by a direct numerical simulation (DNS) at differen...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Correlation energy in a triplet state of a two-electron spherical quantum dotEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Correlation energies in the (1s-1p) triplet state of a two-electron spherical QD with square-well potential confinement are estimated for dots of different radii. The results are presented taking GaAs dot as an example. Our results show that the correlation energies are i) negative in a triplet state in contrast to the singlet state, ii)approaches zero as the dot size approaches infinity, and iii) the "fictitious crossing" of the singlet and triplet state energies at a particular dot size is explained on the basis of Hund's rules. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Interatomic coulombic decay: a short reviewEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The transition process of the interatomic Coulombic decay (ICD), is an electronic radiationless transition process, driving molecular complexes or clusters to a doubly ionized final state. This process differs from the Auger effect, because it takes place from a neutral monomer after the absorption of a released amount energy of the neighboring monomer in the weakly bound molecule. This process has been theoretically studied and the most recent experimental evidence was observed with neon dimer. This work presents a description of the process and a detailed revision of the derivation for the distribution kinetic energy equ...
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

Study on dual-concentric-core dispersion compensation photonic crystal fiberEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The dual-concentric-core photonic crystal fiber composed of pure silica and air is proposed in this paper. Around 1.55 ¼m, it exhibits a negative chromatic dispersion as high as -5850 ps/km/nm. Based on multipole method, a systemic and in-depth simulation is realized to investigate the mode characteristics. The explanations to propagation states of the fundamental mode and the second mode are given elaborately. Finally, the variation of structural parameters is investigated to evaluate the tolerance of the fabrication. As a result, the designed fiber can be fabricated easily. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - October 23, 2009 Category: Physics Source Type: journals

A characterization of the scientific impact of Brazilian institutionsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper we studied the research activity of Brazilian Institutions for all sciences and also their performance in the area of physics between 1945 and December 2008. All the data come from the Web of Science database for this period. The analysis of the experimental data shows that, within a nonextensive thermostatistical formalism, the Tsallis q-exponential distribution N(c) can constitute a new characterization of the research impact for Brazilian Institutions. The data examined in the present survey can successfully be fitted by applying a universal curve namely, with q 4/3 for all the available citations c, T bei...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Nonlocal effects on the thermal behavior of non-crystalline solidsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We argue that nonlocal effects represented by fractionary terms in the kinetic energy can be relevant to achieve a satisfactory phenomenological description of the thermal behavior of the specific heat of non-crystalline solids at very low temperature. We propose a simple model formed by the direct sum of two Hamiltonians, one of which is obtained by incorporating fractional derivatives in the kinetic energy of a conventional Hamiltonian, and the other one accounts for the presence of phonons in the system. Some experimental data are used to support the proposed description. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Note on semiclassical uncertainty relationsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
An important manifestation of the Uncertainty Principle, one of the cornerstones of our present understanding of Nature, is that related to semiclassical localization in phase-space. We wish here to add some notes on the subject with reference to the canonical harmonic oscillator problem, with emphasis in the concepts of semiclassical Husimi distributions, the associated Wehrl entropy, escort distributions, and Fisher's information measure. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Probability distribution in a quantitative linguistic problemEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In the present contribution, we propose a possible way to discuss the distributions of words in a given text. We have devoted our study to discuss some relevant properties observed in Spanish texts of Latin-American writers. We start analyzing the appearance of distributions of the frequency of occurrence in the Zipf perspective. We identify two regions of behavior separated by a special point. In order to correctly define such a point, we work beyond the Zipf law, defining other probability distribution that takes the frequency of repetition of a particular word among other different words into account. At this point, we ...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Nonextensivity in a memory network access mechanismEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We have previously described neurotic psychopathology and psychoanalytic working-through by an associative memory mechanism, based on a neural network. Memory was initially modelled by a Boltzmann machine (BM). We simulated known microscopic mechanisms that control synaptic properties and showed that the network self-organizes to a hierarchical, clustered structure. Some properties of the complex networks which result from this self-organization indicate that a generalization of the BM may be necessary to model memory. We have thus generalized the memory model, using Generalized Simulated Annealing, derived from the nonext...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

A nonextensive method for spectroscopic data analysis with artificial neural networksEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper we apply an evolving stochastic method to construct simple and effective Artificial Neural Networks, based on the theory of Tsallis statistical mechanics. Our aim is to establish an automatic process for building a smaller network with high classification performance. We aim to assess the utility of the method based on statistical mechanics for the estimation of transparent coating material on security papers and cholesterol levels in blood samples. Our experimental study verifies that there are indeed improvements in the overall performance in terms of classification success and at the size of network compar...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Green function for a non-Markovian Fokker-Planck equation: comb-model and anomalous diffusionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We investigate solutions, by using the Green function approach, for a system governed by a non-Markovian Fokker-Planck equation and subjected to a Comb structure. This structure consists of the axis of structure as the backbone and fingers which are attached perpendicular to the axis. For this system, we consider an arbitrary initial condition, in the presence of time dependent diffusion coefficients and spatial fractional derivative, and analyze the connection to the anomalous diffusion. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Lie symmetries and related group-invariant solutions of a nonlinear Fokker-Planck equation based on the Sharma-Taneja-Mittal entropyEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In the framework of the statistical mechanics based on the Sharma-Taneja-Mittal entropy we derive a family of nonlinear Fokker-Planck equations characterized by the associated non-increasing Lyapunov functional. This class of equations describes kinetic processes in anomalous mediums where both super-diffusive and subdiffusive mechanisms arise contemporarily and competitively. We classify the Lie symmetries and derive the corresponding group-invariant solutions for the physically meaningful Uhlenbeck-Ornstein process. For the purely diffusive process we show that any localized state asymptotically approaches a bell shape w...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

q-distributions in complex systems: a brief reviewEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The nonextensive statistical mechanics proposed by Tsallis is today an intense and growing research field. Probability distributions which emerges from the nonextensive formalism(q-distributions) have been applied to an impressive variety of problems. In particular, the role of q-distributions in the interdisciplinary field of complex systems has been expanding. Here, we make a brief review of q-exponential, q-Gaussian and q-Weibull distributions focusing some of their basic properties and recent applications. The richness of systems analyzed may indicate future directions in this field. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Quantum entanglement in a many-body system exhibiting multiple quantum phase transitionsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We investigate the quantum entanglement-related features of the many-body model of Plastino and Moszkowski [N. Cimento 47 (1978) 470]. This is an exactly solvable N-body, SU2 two-level model exhibiting several quantum phase transitions. We show that these transitions happen to be also entanglement-transitions associated with different many-body Dicke states. The main properties of the model considered here make it particularly well suited to study, by recourse to exact analytical computations, some connections between quantum phase transitions and quantum entanglement-theory. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Nonextensive relativistic nuclear and subnuclear equation of stateEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Following the basic prescriptions of the Tsallis' nonextensive relativistic thermodynamics, we investigate the relevance of nonextensive statistical effects on the relativistic nuclear and subnuclear equation of state. In this framework, we study the first order phase transition from hadronic to quark-gluon plasma phase by requiring the Gibbs conditions on the global conservation of the electric and the baryon charges. The relevance of small deviations from the standard extensive statistics is investigated in the context of intermediate and high energy heavy-ion collisions. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Modeling long-memory processes by stochastic difference equations and superstatistical approachEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
It is shown that the Poissonian-like process with slowly diffusing-like time-dependent average interevent time may be represented as the superstatistical one and exhibits 1/ f noise. The distribution of the Poissonian-like interevent time may be expressed as q-exponential distribution of the Nonextensive Statistical Mechanics. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Generalised cascadesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this manuscript we give thought to the aftermath on the stable probability density function when standard multiplicative cascades are generalised cascades based on the q-product of Borges that emerged in the context of non-extensive statistical mechanics. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Symbolic sequences and Tsallis entropyEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We address this work to investigate symbolic sequences with long-range correlations by using computational simulation. We analyze sequences with two, three and four symbols that could be repeated l times, with the probability distribution p(l) ∝ 1/l µ. For these sequences, we verified that the usual entropy increases more slowly when the symbols are correlated and the Tsallis entropy exhibits, for a suitable choice of q, a linear behavior. We also study the chain as a random walk-like process and observe a nonusual diffusive behavior depending on the values of the parameter µ. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

q-exponential distribution in time correlation function of water hydrogen bondsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In a series of molecular dynamics simulations we analyzed structural and dynamics properties of water at different temperatures (213 K to 360 K), using the Simple Point Charge-Extended (SPC/E) water. We detected a q-exponential behavior in the history-dependent bond correlation function of hydrogen bonds. We found that q increases with T -1 below approximately 300 K and is correlated to the increase of the tetrahedral structure of water and the subdiffusive motion of the molecules. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Nonextensive statistical mechanics applied to protein folding problem: kinetics aspectsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A reduced (stereo-chemical) model is employed to study kinetic aspects of globular protein folding process, by Monte Carlo simulation. Nonextensive statistical approach is used: transition probability p i j between configurations i → j is given by p i j =[1 +(1 - q)ΔGi j/kB T ]1/(1-q), where q is the nonextensive (Tsallis) parameter. The system model consists of a chain of 27 beads immerse in its solvent; the beads represent the sequence of amino acids along the chain by means of a 10-letter stereo-chemical alphabet; a syntax (rule) to design the amino acid sequence for any given 3D structure is embedded in the model. T...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Critical behavior of the delay-induced chaos transition in a nonlinear model for the immune responseEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper we analyze a model for the dynamics of the immune system interacting with a target population. The model consists in a set of two-dimensional delayed differential equations. The model is effectively infinite dimensional due to the presence of the delay and chaotic regimes can be supported. We show that a delayed response induces sustained oscillations and larger delay times implies in a series of bifurcations leading to chaos. The characteristic exponent of the critical power law relaxation towards the stationary state is obtained as well as the critical exponent governing the vanishing of the order parameter...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Main shocks and evolution of complex earthquake networksEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Dynamical evolution of earthquake network is studied. Through the analysis of the real data taken from California and Japan, it is found that the values of the clustering coefficient exhibit a specific behavior around the moment of a main shock: the coefficient remains stationary before a main shock, suddenly jumps up at the main shock, and then slowly decreases to become stationary again. Thus, the network approach to seismicity dynamically characterizes main shocks in a peculiar manner. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Generating more realistic complex networks from power-law distribution of fitnessEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this work we analyze the implications of using a power law distribution of vertice's quality in the growth dynamics of a network studied by Bianconi and Barabási. Using this suggested distribution we show the degree distribution interpolates the Barabási et al. model and Bianconi et al. model. This modified model (with power law distribution) can help us understand the evolution of complex systems. Additionally, we determine the exponent gamma related to the degree distribution, the time evolution of the average number of links,< ki >∝ (t/i)β (i coincindes with the input-time of the i th node), the average path len...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Tsallis scaling in the long-range Ising chain with competitive interactionsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A numerically efficient transfer matrix approach is used to investigate the validity of the Tsallis scaling hypothesis in the long-range Ising spin chain with competitive interactions. In this model, the interaction between two spins i and j placed r lattice steps apart is Ji, j = (-1)ζ(i,j)J0/rα, where ζ(i, j) is either 0 or 1. This procedure has succeeded to show the validity of the scaling hypothesis for the well investigated ferromagnetic version of the model, i.e., ζ(i, j)= 0,∀i, j, ∀α > 0. Results are reported for some models of a set, which is defined by requiring ζ(i, j) to be a periodic sequence of 0's a...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Generalized-generalized entropies and limit distributionsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Limit distributions are not limited to uncorrelated variables but can be constructively derived for a large class of correlated random variables, as was shown e.g. in the context of large deviation theory [1], and recently in a very general setting by Hilhorst and Schehr [2]. At the same time it has been conjectured, based on numerical evidence, that several limit distributions originating from specific correlated random processes follow q-Gaussians. It could be shown that this is not the case for some of these situations, and more complicated limit distributions are necessary. In this work we show the derivation of the an...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

q-entropies and the entanglement dynamics of two-qubits interacting with an environmentEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We investigate entropic aspects of the quantum entanglement dynamics of two-qubits systems interacting with an environment. In particular we consider the detection, based on the violation of classical entropic inequalities involving q-entropies, of the phenomenon of entanglement disappearance and subsequent entanglement revival during the alluded two-qubits' evolution. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Some properties of deformed q-numbersEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Nonextensive statistical mechanics has been a source of investigation in mathematical structures such as deformed algebraic structures. In this work, we present some consequences of q-operations on the construction of q-numbers for all numerical sets. Based on such a construction, we present a new product that distributes over the q-sum. Finally, we present different patterns of q-Pascal's triangles, based on q-sum, whose elements are q-numbers. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Generalized entropy indices to measure α- and β-diversities of macrophytesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A family of entropy indices constructed in the framework of Tsallis entropy formalism is used to investigate ecological diversity. It represents a new perspective in ecology because a simple equation can incorporate all aspects of α-diversity, from richness to dominance and can be also related to a measure of species rarity. In addition, a generalized Kullback-Leibler distance, constructed in the framework of a nonextensive formalism, is recalled and used as a measure of β-diversity between two systems. These tools are applied to data relative to the macrophytes collected from two not far apart arms of Itaipu Reservoir, ...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Introducing the q-Theil indexEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Starting from the idea of Tsallis on non-extensive statistical mechanics and the q-entropy notion, we recall the Theil index Th and transform it into the Th q index. Both indices can be used to map onto themselves any time series in a non linear way. We develop an application of the Th q to the GDP evolution of 20 rich countries in the time interval [1950 -2003] and search for a proof of globalization of their economies. First we calculate the distances between the "new" time series and to their mean, from which such data simple networks are constructed. We emphasize that it is useful to, and we do, take into account diffe...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Nuclear problems in astrophysical q-plasmas and environmentsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Experimental measurements in terrestrial laboratory, space and astrophysical observations of variation and fluctuation of nuclear decay constants, measurements of large enhancements in fusion reaction rate of deuterons implanted in metals and electron capture by nuclei in solar core indicate that these processes depend on the environment where they take place and possibly also on the fluctuation of some extensive parameters and eventually on stellar energy production. Electron screening is the first important environment effect. We need to develop a treatment beyond the Debye-Hückel screening approach, commonly adopted wi...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Central limit theorems for correlated variables: some critical remarksEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this talk I first review at an elementary level a selection of central limit theorems, including some lesser known cases, for sums and maxima of uncorrelated and correlated random variables. I recall why several of them appear in physics. Next, I show that there is room for new versions of central limit theorems applicable to specific classes of problems. Finally, I argue that we have insufficient evidence that, as a consequence of such a theorem, q-Gaussians occupy a special place in statistical physics. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Dynamics towards the Feigenbaum attractorEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
As an essential component in the demonstration of an atypical, q-deformed, statistical mechanical structure in the dynamics of the Feigenbaum attractor we expose, at a previously unknown level of detail, the features of the dynamics of trajectories that either evolve towards the Feigenbaum attractor or are captured by its matching repellor. Amongst these features are the following: i) The set of preimages of the attractor and of the repellor are embedded (dense) into each other. ii) The preimage layout is obtained as the limiting form of the rank structure of the fractal boundaries between attractor and repellor positions ...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Recent developments in superstatisticsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We provide an overview on superstatistical techniques applied to complex systems with time scale separation. Three examples of recent applications are dealt with in somewhat more detail: the statistics of small-scale velocity differences in Lagrangian turbulence experiments, train delay statistics on the British rail network, and survival statistics of cancer patients once diagnosed with cancer. These examples correspond to three different universality classes: Lognormal superstatistics, χ2-superstatistics and inverse χ2 superstatistics. (Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Nonadditive entropy and nonextensive statistical mechanics -an overview after 20 yearsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Statistical mechanics constitutes one of the pillars of contemporary physics. Recognized as such - together with mechanics (classical, quantum, relativistic), electromagnetism and thermodynamics -, it is one of the mandatory theories studied at virtually all the intermediate-and advanced-level courses of physics around the world. As it normally happens with such basic scientific paradigms, it is placed at a crossroads of various other branches of knowledge. In the case of statistical mechanics, the standard theory - hereafter referred to as the Boltzmann-Gibbs (BG) statistical mechanics - exhibits highly relevant connectio...
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

ForewordEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
(Source: Brazilian Journal of Physics)
Source: Brazilian Journal of Physics - September 11, 2009 Category: Physics Source Type: journals

Influence of high frequency and moderate energy pulses on DLC deposition onto metallic substrates by magnetron sputtering techniqueEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The deposition of Diamond-like carbon (DLC) films brings excellent mechanical, chemical, optical and electronic properties to a large range of materials. However, a problem to be overcome is its poor adhesion on metallic substrates. Usually, a silicon layer must be deposited on the surface of metals previous to DLC film deposition. In fact, in our experiments using conventional Magnetron Sputtering (MS) technique for deposition of DLC film on metal surfaces (AISI 304 stainless steel, Al 2024, Ti-6Al-4V), the silicon interlayer was crucial to avoid delamination. However, a combined process using MS and high frequency and mo...
Source: Brazilian Journal of Physics - July 24, 2009 Category: Physics Source Type: journals