Warped Riemannian metrics for location-scale models

The present paper shows that warped Riemannian metrics, a class of Riemannian metrics which play a prominent role in Riemannian geometry, are also of fundamental importance in information geometry. Precisely, the paper features a new theorem, which states that the Rao-Fisher information metric of any location-scale model, defined on a Riemannian manifold, is a warped Riemannian metric, whenever this model is invariant under the action of some Lie group. This theorem is a valuable tool in finding the expression of the Rao-Fisher information metric of location-scale models defined on high-dimensional Riemannian manifolds. Indeed, a warped Riemannian metric is fully determined by only two functions of a single variable, irrespective of the dimension of the underlying Riemannian manifold. Starting from this theorem, several original contributions are made. The expression of the Rao-Fisher information metric of the Riemannian Gaussian model is provided, for the first time in the literature. A generalised definition of the Mahalanobis distance is introduced, which is applicable to any location-scale model defined on a Riemannian manifold. The solution of the geodesic equation is obtained, for any Rao-Fisher information metric defined in terms of warped Riemannian metrics. Finally, using a mixture of analytical and numerical computations, it is shown that the parameter space of the von Mises-Fisher model of $n$-dimensional directional data, when equipped with its Rao-Fisher information metric, becomes a Hadamard manifold, a simply-connected complete Riemannian manifold of negative sectional curvature, for $n = 2,\ldots,8$. Hopefully, in upcoming work, this will be proved for any value of $n$.Comment: first version, before submissio

Mortalidade infantil e acesso geográfico ao parto nos municípios brasileiros

OBJETIVO: Analisar o acesso geográfico ao parto hospitalar nos municípios brasileiros. MÉTODOS: Foram analisadas informações de óbitos e nascimentos quanto à sua adequação para o cálculo do coeficiente de mortalidade infantil no período de 2005 a 2007 para os 5.564 municípios brasileiros. O acesso geográfico foi expresso por indicadores de deslocamento, oferta e acesso aos serviços de saúde. A associação entre o acesso geográfico ao parto e o coeficiente de mortalidade infantil em municípios com adequação de suas informações vitais foi avaliada por meio de regressão múltipla. RESULTADOS: Dentre os municípios analisados, 56% apresentaram adequação das informações vitais, correspondendo a 72% da população brasileira. O deslocamento geográfico ao parto mostrou-se inversamente associado ao porte populacional, à renda per capita, e à mortalidade infantil, mesmo controlado por fatores demográficos e socioeconômicos. CONCLUSÕES: Embora tenham sido desenvolvidas estratégias importantes para a melhoria da qualidade do atendimento às gestantes no Brasil, as ações para garantir o acesso igualitário à assistência ao parto ainda são insuficientes. O maior deslocamento intermunicipal para o parto se mostrou como um fator de risco para a mortalidade infantil, aliado à desigualdade de oferta de serviços qualificados e à falta de integração com a atenção básica de saúde

The role of centrosomal Nlp in the control of mitotic progression and tumourigenesis

The human centrosomal ninein-like protein (Nlp) is a new member of the γ-tubulin complexes binding proteins (GTBPs) that is essential for proper execution of various mitotic events. The primary function of Nlp is to promote microtubule nucleation that contributes to centrosome maturation, spindle formation and chromosome segregation. Its subcellular localisation and protein stability are regulated by several crucial mitotic kinases, such as Plk1, Nek2, Cdc2 and Aurora B. Several lines of evidence have linked Nlp to human cancer. Deregulation of Nlp in cell models results in aberrant spindle, chromosomal missegregation and multinulei, and induces chromosomal instability and renders cells tumourigenic. Overexpression of Nlp induces anchorage-independent growth and immortalised primary cell transformation. In addition, we first demonstrate that the expression of Nlp is elevated primarily due to NLP gene amplification in human breast cancer and lung carcinoma. Consistently, transgenic mice overexpressing Nlp display spontaneous tumours in breast, ovary and testicle, and show rapid onset of radiation-induced lymphoma, indicating that Nlp is involved in tumourigenesis. This review summarises our current knowledge of physiological roles of Nlp, with an emphasis on its potentials in tumourigenesis