We prEsent a detailed derivation of the effective dielectric constant to be used in the dispersion relation for electrostatic waves in the case of a Plasma immersed in a inhomogeneous magnetic ?eld, with inhomogeneity perpendicular to the direction of the magnetic ?eld.

BACKGROUND: Gingival recession is a common manifestation of periodontal disease, but it is also associated with other risk factors. A few studies have investigated the epidemiology and risk factors of this condition. This study describes the epidemiology of gingival recession in a representative, urban Brazilian population and assesses various risk indicators. METHODS: A representative sample of 1,460 subjects was selected using a multi-stage, probability, cluster sampling strategy. The subjects were interviewed using a structured questionnaire and had a full-mouth clinical examination in a mobile examination center. RESULTS: More than half (51.6%) and 22.0% of the individuals and 17.0% and 5.8% of teeth per individual showed gingival recession > or = 3 mm and > or = 5 mm, respectively. The prevalence, extent, and severity of recession correlated with age. Recession showed a nonlinear relationship with age, with 25 to 50 year olds showing the highest level of recession. Males aged > or = 30 years showed significantly higher prevalence and extent of gingival recession than females. The percentage of teeth with recession was significantly higher in the lower socioeconomic groups irrespective of age, and in subjects > or = 30 years of age with irregular dental care than in subjects with regular care. Using a multivariable model, cigarette smoking and presence of supragingival calculus were the factors most significantly associated with localized and generalized recession, whereas gender, dental visits, and socioeconomic status were not significant risk indicators. CONCLUSIONS: The high level of gingival recession in this Brazilian population may be primarily related to destructive periodontal disease and is significantly associated with a high level of supragingival dental calculus and cigarette smoking. Population-based programs aimed at the prevention of periodontal diseases may reduce the prevalence of severe gingival recession in this and similar populations.

We compare and discuss several approximations to the dispersion relation for electrostatic waves in inhomogeneous Plasmas, either obtained directly from Poisson?s equation, or from the dielectric constant obtained using a dielectric tensor derived using the plAne wave approximation, or from the dielectric constant derived using the effective dielectric tensor.

The prEservation of Onsager symmetry for the effective dielectric tensor is discussed for a homogeneous Plasma immersed in a inhomogeneous magnetic ?eld, using the unperturbed orbits correct up to order $k\_B$, which is the scalelength of the field inhomogeneity. General features of the calculation of the components of the tensor are discussed and detailed calculations are developed for the $zz$ component, which is shown to satisfy the conditions for Onsager symmetry, in agreement with prEvious results obtained using less prEcise exprEssions for the unperturbed orbits.

Meu objetivo neste texto é simplesmente analisar o quarto parágrafo da Segunda Meditação (AT VII, 24-25; IX-1,19), no qual ele supostamente apresenta este mesmo argumento sem empregar a famosa expressão. Das muitas, diversas e relevantes questões filosóficas que este argumento suscita, gostaria de me concentrar em investigar se ele pode ser reconstruído sem que seja necessário introduzir – como uma premissa não justificada – a concepção do pensamento como sendo essencialmente consciência de si e, portanto, como envolvendo - por definição, a auto-referência imediata e incorrigível do sujeito a si mesmo. Gostaria de poder mostrar que o argumento não apenas independe dessa concepção como, além disso, conduz a essa concepção; todavia, somente o primeiro passo em direção a esta interpretação será dado neste artigo.