Fractality of largest clusters and the percolation transition in power-law diluted chains.

Relying on the fractal character of the largest clusters at criticality, we employ a finite-size scaling analysis to obtain an accurate phase-diagram of the percolation transition in chains with bond concentration decaying as a power-law on the form 1/ r(1+sigma) . For the particular case of sigma=1, no percolation transition is observed to occur at a finite dilution, in contrast with the finite temperature Kosterlitz-Thouless transition exhibited in Ising and Potts chains with inverse square-law couplings. The fractal dimension of the critical percolation cluster is found to follow distinct dependencies on the decay exponent being numerically fitted by d(f) =0.35+4sigma/5 for 0

Enhanced localization, energy anomalous diffusion and resonant mode in harmonic chains with correlated mass-spring disorder.

In this work, we study the vibrational modes and energy spreading in a harmonic chain model with diluted second-neighbors couplings and correlated mass-spring disorder. While all nearest neighbor masses are coupled by an elastic spring, second neighbors springs are introduced with a probability pD. The masses are randomly distributed according to the site connectivity mi = m0 (1 + 1/n(α)(I), where ni is the connectivity of the site i and α is a tunable exponent. We show that maximum localization of the vibrational modes is achieved for α ≃ 3/4. The time-evolution of the energy wave-packet is followed after an initial localized excitation. While the participation number remains finite, the energy spread is shown to be sub-diffusive after a displacement and super-diffusive after an impulse excitation. These features are related to the development of a power-law tail in the wave-packet distribution. Further, we unveil that the spring dilution leads to the emergence of a resonant localized state which is signaled by a van Hove singularity in the density of states.

[Silent myocardial ischemia: its increase with aging]. / Isquemia miocárdica silenciosa: seu aumento com a idade.

PURPOSE: To evaluate whether the number and duration of the episodes of silent myocardial ischemia increase with aging of patients. METHODS: A Holter monitoring, with CardioData equipment, was made in 1,300 patients and 330 with proven significant coronary obstructions were selected for this study. The anti-anginal medication was maintained during the 24 or 48 hours of Holter recording. The patients were arbitrarily divided into four groups according to age less than 50 years, 50 to 59 years, 60 to 69 years and greater than or equal to 70 years old. The statistical analysis was made with two models, the model of logistic regression and the Poisson model. RESULTS: Myocardia ischemia was detected in 72 patients (21.8%), 55 (76%) had only silent episodes, 6 (9%) had only anginal ischemia and 11 patients (155) had both silent and anginal ischemia. There was a progressive increase in the number and duration of the episodes of myocardial ischemia with aging. The proportion of patients with episodes of myocardial ischemia in the 4 age groups was 12.12%, 19.75%, 22.25% and 31.48% and the duration of the episodes of ischemia per patient 37, 37.5, 50.8 and 85.1 minutes, respectively. Statistical analysis showed a significant increase with aging in number and duration of the episodes. CONCLUSIONS: Myocardial ischemia is still present in asymptomatic patients during anti-anginal treatment and the ischemia is mainly silent. There is a progressive increase with aging in number and duration of the episodes of ischemia.

Energy transport in a one-dimensional harmonic ternary chain with Ornstein-Uhlenbeck disorder.

In this paper we study a one-dimensional ternary harmonic chain with the mass distribution constructed from an Ornstein-Uhlenbeck process. We generate a ternary mass disordered distribution by generating the correlated Ornstein-Uhlenbeck process and mapping it into a sequence of three different values. The probability of each value is controlled by a fixed parameter b. We analyze the localization aspect of the above model by numerical solution of the Hamilton equations and by the transfer matrix formalism. Our results indicate that the correlated ternary mass distribution does not promote the appearance of new extended modes. In good agreement with previous work, we obtain extended modes for b â†’ ∞; however, we explain in detail the main issue behind this apparent localization- delocalization transition. In addition, we obtain the energy dynamics for this classical chain.

Resonant localized states and quantum percolation on random chains with power-law-diluted long-range couplings.

We investigate the nature of one-electron eigenstates in power-law-diluted chains for which the probability of occurrence of a bond between sites separated by a distance r decays as p(r) = p/r(1+σ). Using an exact diagonalization scheme and a phenomenological finite-size scaling analysis, we determine the quantum percolation transition phase diagram in the full parameter space (p,σ). We show that the density of states displays singularities at some resonance energies associated with degenerate eigenstates localized in a pair of sites with special symmetries. This model is shown to present an intermediate phase for which there is classical percolation but no quantum percolation. Quantum percolation only takes place for σ < 0.78, a value larger than the corresponding one for the Anderson transition in long-ranged coupled chains with random diagonal disorder. The fractality of critical wavefunctions is also characterized.

Prevalence of dental trauma children aged 1-3 years in Joao Pessoa (Brazil).

AIM: This was to determine the prevalence and distribution of traumatic injuries to primary anterior teeth in children from 1 to 3 years-old. METHODS: A cross-sectional survey was carried out through clinical examination of the primary dentitions of preschool children enrolled in public nursery schools in Joao Pessoa (Brazil). A total of 293 boys and girls participated in the study. The children were clinically examined for signs of trauma according to Andreasen's classification. RESULTS: Traumatic injuries were identified in 10.2% of children. The largest percentage of injuries was demonstrated by 2-3 years-old, with no significant difference between boys and girls. The most common type of injury was enamel fracture and enamel-dentine fracture. The maxillary central incisor was the most vulnerable to injury, without differences between the right and left side. STATISTICS: The data were entered in the SPSS program, and the chi square test was used with a 5% significance level. CONCLUSION: The primary dentition was most affected by fracture of enamel, especially the maxillary central incisor teeth, in patients between 2 and 3 years of age. There is a need of providing adequate preventive and treatment care for preschool children.