Homogeneity and plane-wave limits

We explore the plane-wave limit of homogeneous spacetimes. For plane-wave limits along homogeneous geodesics the limit is known to be homogeneous and we exhibit the limiting metric in terms of Lie algebraic data. This simplifies many calculations and we illustrate this with several examples. We also investigate the behaviour of (reductive) homogeneous structures under the plane-wave limit.Comment: In memory of Stanley Hobert, 33 pages. Minor corrections and some simplification of Section 4.3.

Nariai, Bertotti-Robinson and anti-Nariai solutions in higher dimensions

We find all the higher dimensional solutions of the Einstein-Maxwell theory that are the topological product of two manifolds of constant curvature. These solutions include the higher dimensional Nariai, Bertotti-Robinson and anti-Nariai solutions, and the anti-de Sitter Bertotti-Robinson solutions with toroidal and hyperbolic topology (Plebanski-Hacyan solutions). We give explicit results for any dimension D>3. These solutions are generated from the appropriate extremal limits of the higher dimensional near-extreme black holes in a de Sitter, and anti-de Sitter backgrounds. Thus, we also find the mass and the charge parameters of the higher dimensional extreme black holes as a function of the radius of the degenerate horizon.Comment: 10 pages, 11 figures, RevTeX4. References added. Published versio

Prevalência de cárie e necessidades de tratamento em escolares de seis a doze anos de idade, Goiânia, GO, Brasil, 1994 The prevalence of dental caries and necessary treatment in six to twelve years old schoolchildren in Brazil, 1994

OBJETIVO: Investigou-se a prevalência de cárie e necessidades de tratamento em escolares de Goiânia-GO, Brasil, que possui água fluoretada há 9 anos. METODOLOGIA: A amostra foi constituída de 1.400 escolares de 6 a 12 anos de idade que freqüentavam escolas públicas na zona urbana do município estudado. RESULTADOS: Os índices CPO-D e ceo-d encontrados no total da amostra foram 2,19 e 2,86, respectivamente, demonstrando uma redução de 57,1% em relação ao CPO-D verificado na região Centro-Oeste, em 1986. Para os escolares de 12 anos de idade, o CPO-D encontrado foi 4,59, estando acima da meta estabelecida para o ano 2.000 pela FDI/OMS. Verificou-se que a percentagem de escolares livres de cárie foi muito baixa em todas as idades, apresentando-se em torno de 11% para o total da amostra. Houve predomínio do tratamento restaurador na dentição decídua em todas as idades e na permanente a partir dos 9 anos de idade. CONCLUSÃO: A prevalência de cárie em escolares de Goiânia-GO é alta e comparável à situação verificada na maioria dos países da América Latina e nas regiões menos favorecidas de países desenvolvidos. Há necessidade de se implantar medidas educativas e preventivas em saúde bucal que intervenham nos reais determinantes da doença na população.<br>OBJECTIVE: The prevalence of dental caries and needs of treatment among schoolchildren in Goiânia-GO, middle-west of Brazil was assessed. METHODOLOGY: The study population consisted of 6-12-yr-old schoolchildren (n=1,400) attending public schools located in the urban area of the city, where the water-supply had been fluoridated for 9 years. RESULTS: Mean dmf-t and DMF-T for the total sample were 2.19 and 2.86, respectively, showing a reduction of 57.1% in the DMF-T as compared to the regional data from the national survey carried out in 1986. At age 12 DMF-T was 4.59, which is above the acceptable level according to the FDI/WHO goal for the year 2000. Percentage of caries-free schoolchildren was very low at all ages (11% of the total sample). The most significant need was for restorative treatment in the treatment deciduous dentition at all ages and in the permanent dentition from age 9. CONCLUSION: It was concluded that the prevalence of dental caries among schoolchildren in Goiânia-GO is high, comparable to the situation in most Latin American countries and poor regions of developed countries. The results indicate the need for oral health education and preventive programs targeted at the underlying causes of the disease, in the population