This article demonstrates the generation of enhanced ion-acoustic waves by beam-plasma instability in a density cavity. The self-consistent equations of weak turbulence theory that include quasi-linear, decay, and scattering processes as well as convective and dispersive effects are numerically solved for a one-dimensional density cavity. It is shown that significant enhancements of ion-acoustic waves occur in the presence of counterstreaming electron beams and that the enhanced ion-acoustic waves are initially localized near the center of the density cavity at large wavelengths. Later in the evolution, the enhancement in the spectrum of ion-acoustic waves spreads out toward the edges of the cavity, with a shift to smaller wavelengths, while the enhancement near the center of the cavity tends to decrease in magnitude. The significance of the present findings is discussed.

This cross-sectional study evaluated the consumption of fluoridated dentifrice and associated factors in Passo Fundo, Rio Grande do Sul State, Brazil. A total of 688 households were selected. A structured questionnaire was answered by the mother to obtain demographics, habits, and toothpaste consumption. Household toothpaste consumption was considered low when a tube lasted > 1 month and high when < 1 month. Logistic regression models were applied to evaluate the association between consumption and independent variables. 61.2% of households showed high toothpaste consumption. In the multivariate model, mother's age > 50 years (OR = 1.62; 95%CI: 1.02-2.61), mother's brushing frequency (OR = 2.53; 95%CI: 1.53-4.16), number of people brushing (OR = 5.69; 95%CI: 3.68-8.81), and cosmetic features in choice of the dentifrice (OR = 1.64; 95%CI: 1.03-2.61) showed the highest odds of high toothpaste consumption.

The problem of electron-beam propagation in inhomogeneous solar wind is intimately related to the solar type II and/or type III radio bursts. Many scientists have addressed this issue in the past by means of quasi-linear theory, but in order to fully characterize the nonlinear dynamics, one must employ weak-turbulence theory. Available numerical solutions of the weak-turbulence theory either rely on only one nonlinear process (either decay or scattering), or when both nonlinear terms are included, the inhomogeneity effect is generally ignored. The present paper reports the full solution of weak-turbulence theory that includes both decay and scattering processes, and also incorporating the effects of density gradient. It is found that the quasi-linear effect sufficiently accounts for the primary Langmuir waves, but to properly characterize the back-scattered Langmuir wave, which is important for eventual radiation generation, it is found that both nonlinear decay and scattering processes make comparable contributions. Such a finding may be important in the quantitative analysis of the plasma emission process with application to solar type II and/or type III radio bursts.

We present general expressions for the components of the dielectric tensor of magnetized dusty plasmas, valid for arbitrary direction of propagation and for situations in which populations of dust particles of different sizes are present in the plasma. These expressions are derived using a kinetic approach which takes into account the variation of the charge of the dust particles due to inelastic collisions with electrons and ions, and features the components of the dielectric tensor in terms of a finite and an infinite series, containing all effects of harmonics and Larmor radius, and is valid for the whole range of frequencies above the plasma frequency of the dust particles, which are assumed to be motionless. The integrals in velocity space which appear in the dielectric tensor are solved assuming that the electron and ion populations are described by anisotropic non-thermal distributions characterized by parameters κ ∥ and κ ⊥ , featuring the Maxwellian as a limiting case. These integrals can be written in terms of generalized dispersion functions, which can be expressed in terms of hypergeometric functions. The formulation therefore becomes specially suitable for numerical analysis.

Beam–plasma instability of inhomogeneous media is an important problem associated with practical applications in space and laboratory plasmas. Previous investigations of the spatially inhomogeneous beam–plasma instability problem assumed one-dimensional velocity and wave number space. This paper extends the available theory to two-dimensional velocity and wave number space. A fully self-consistent set of quasilinear particle and wave kinetic equations is solved for two-dimensional velocity and wave number space in both time and one-dimensional spatial inhomogeneity scale length. The analytical equations include induced and spontaneous emission processes, as well as convective and dispersive effects.

AIM: To describe the distribution of clinical attachment loss (CAL) and to study risk indicators for chronic periodontitis in a large population-based sample of adolescents and young adults from south Brazil. MATERIAL AND METHODS: This cross-sectional study used a subset of data from a larger survey representative of Porto Alegre, Brazil. The sample consisted of 612 individuals (291 males/321 females) aged 14-29 years. Full-mouth, six sites per tooth clinical examinations were performed by calibrated periodontists. Chronic periodontitis was defined as CAL 3mm affecting two or more teeth. Aggressive periodontitis cases were excluded from the analysis. RESULTS: CAL 3 and 5mm affected 50.4% and 17.4% of subjects and 9.7% and 1.1% of teeth, respectively. Prevalence of chronic periodontitis ranged between 18.2% and 72.0% among subjects 14-19 and 24-29 years old, respectively. In the multivariable logistic regression analysis, older age [odds ratio (OR)=2.6, 95% confidence interval (CI)=1.7-3.9 and OR=7.2, 95% CI=3.7-14.0 for 20-24 and 25-29 years old, respectively], low socioeconomic status (OR=1.9, 95% CI=1.4-2.7), heavy smoking (OR=1.7, 95% CI=1.1-2.7) and larger amounts of calculus (OR=2.0, 95% CI=1.2-3.2) were significantly associated with chronic periodontitis. CONCLUSION: This population of adolescents and young adults had a high prevalence of chronic periodontitis, and its presence was associated with age, socioeconomic status, smoking and calculus.

presente artigo tem por objetivo apresentar o desenvolvimento de pictogramas específicos para o
ambiente virtual de aprendizagem de Geometria Descritiva denominado HyperCAL3D. Os pictogramas são
desenvolvidos a partir de uma metodologia fundamentada no design de informação e no design de
interação, com o objetivo de qualificar o aplicativo quanto à usabilidade e à interatividade.