BACKGROUND Although the tendency to repeat examinations is a major determinant of the capacity to serve new patients and of the ability to contain health care costs, little research has described the patterns observed in actual practice. METHODS We investigated patterns of repeat testing in a longitudinal study of a 5% random sample of Medicare beneficiaries, restricted to 743,478 fee-for-ser...

Population growth in West Africa has outpaced local efforts to expand potable water services, and private sector sale of packaged drinking water has filled an important gap in household water security. Consumption of drinking water packaged in plastic sachets has soared in West Africa over the last decade, but the long-term implications of these changing consumption patterns remain unclear and ...

Spatially extensive analysis of satellite, climate, and census data reveals humanenvironment interactions of regional or continental concern i n the United States. A grid-based principal components analysis of Bureau of Census variables revealed two independent demographic phenomena, a-settlement reflecting traditional human settlement patterns and p-settlement describing relative population gr...

An urban microeconomic model of households evolving in a 2D cellular automata allows to simulate the growth of a metropolitan area where land is devoted to housing, road network and agricultural/green areas. This system is self-organised: based on individualistic decisions of economic agents who compete on the land market, the model generates a metropolitan area with houses, roads, and agricult...

The unusual mixed public-private structure of the urban bus market in the metropolitan area of Barcelona provides an interesting context in which to analyze the management challenges and opportunities of the partial privatization of public services. Initiatives used by the public regulator to promote competition for contracts, such as short term concessions to private contractors and the remova...

This study applied logistic regression to model urban growth in the Atlanta Metropolitan Area of Georgia in a GIS environment and to discover the relationship between urban growth and the driving forces. Historical land use/cover data of Atlanta were extracted from the 1987 and 1997 Landsat TM images. Multi-resolution calibration of a series of logistic regression models was conducted from 50 m...

Demographically, cities throughout the world seem to be expanding rather than shrinking. However a closer look at recent urban population change among the world’s largest urban agglomerations of one million people or more reveals that between 2000 and 2005, 30 out of 414 cities experienced zero to negative average annual growth (U.N. 2005). Recently, this internationalized pattern of city contr...