Trends in U.S. Public Awareness of Racial and Ethnic Health Disparities (1999-2010): Study Brief

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Trends in U.S. Public Awareness of Racial and Ethnic Health Disparities (1999-2010): 2009 General Population Toplines

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Mineralogy of some soils from the Amazonia Sedimentary Basin.

ABSTRACT: The Amazonia Forest is an important biome that possesses great diversity of fauna and flora, which can play a significant role in several science areas, specially, the gene reserve for the future of humankind. Nevertheless, it is a very poorly understood environment, particularly the basis of this ecosystem, its soils. This study was conducted to gain insight in the mineralogy of important soils classes of the Amazonia sedimentary basin. The soils in the upland position in the landscape are developed from tertiary sediments belonging to the Alter do Chão series and those in the floodplain position are derived from quaternary, more specifically, Holocene´s sediments. Sand, silt and clay fractions were separated and X-ray diffraction analysis was conducted. Very simple mineralogy composed basically of quartz in the coarser fractions and kaolinite, goethite and anatase for the finer fraction was found for the Oxisol, the Ultisol and the Entisol from an upland toposequence but differences in kaolinite crystallography could be noticed among them. Gibbsite was virtually absent, in spite of the advanced degree of development of most of these soils. More distinctive mineralogy was revealed for the soils developed in the more recent sediments with quartz and feldspars in the sand and silt fractions and a suite of 2:1 minerals also appearing in their clay fraction, besides kaolinite and goethite. In one upland soil petroplinthite is the main feature and its mineralogy reflected its environment of formation which is usually associated with level to gently sloping areas with fluctuating water table

Trapping in the random conductance model

We consider random walks on $\Z^d$ among nearest-neighbor random conductances which are i.i.d., positive, bounded uniformly from above but whose support extends all the way to zero. Our focus is on the detailed properties of the paths of the random walk conditioned to return back to the starting point at time $2n$. We show that in the situations when the heat kernel exhibits subdiffusive decay --- which is known to occur in dimensions $d\ge4$ --- the walk gets trapped for a time of order $n$ in a small spatial region. This shows that the strategy used earlier to infer subdiffusive lower bounds on the heat kernel in specific examples is in fact dominant. In addition, we settle a conjecture concerning the worst possible subdiffusive decay in four dimensions.Comment: 21 pages, version to appear in J. Statist. Phy