Spatial Diffusion of the HIV/AIDS Epidemic: Modeling Implications and Case Study of AIDS Incidence in Ohio

This paper extends a compartmental epidemiological model for HIV transmission and AIDS incidence to include hierarchical and expansion spatial diffusion. An implication of the resultant model is that hierarchical diffusion causes the large infection growth rates of densely populated areas at the top of the central places hierarchy to “chain” down and dominate small local growth rates during the exponential-growth phase of the epidemic. Also, hierarchical diffusion causes a high transient growth rate in the first few years of a local epidemic. The spatial compartmental model fits observed AIDS incidence spatial diffusion patterns in Ohio reasonably well.     

Planning in the 1990s: An international agenda

This paper, originally presented to the AESOP‐ACSP joint conference in Oxford in 1991, stresses that both in Europe and in the US, there is a major difference for planning in the switch from boom to recession. During the 1990s a major challenge will be to find new ways of public‐private partnership in financing new urban infrastructure at a time when developer contributions — a major innovation of the 1980s — have dried up. This particularly applies to the European high‐speed train system — one critical element of which will run through the East Thames Corridor, one of Britain's major urban developments in the coming years. In the US, planners are likely to remain more locally focused, less internationally concerned, than in a Europe in which national barriers are rapidly eroding.     

THE APPLICATION OF ACETATE PEELS IN LITHIC USEWEAR ANALYSIS

A technique for making acetate peels of tools using Triafol is outlined. A series of ‘blind tests’ is described where the suitability of this replica material for reproducing the details of usewear was tested. The advantages and disadvantages of the use of acetate peels are discussed with reference to examination of usewear traces.     

The direction of migration: a dynamic general equilibrium model

A two-sector dynamic general equilibrium model is developed "to investigate the direction of migration in response to differing demographic and consumption demand behavior, as well as variations in production conditions." The model, which involves a rural sector and an urban sector, incorporates "returns to scale and the natural rate of sectoral population growth as important determinants of the direction of migration, in addition to price and income elasticities, and the sectoral technical change rate with which...previous studies dealt."     

Net migration estimation in an extended,multiregional gravity model

A multi-regional framework is developed in order to analyze net migration over time to all 10 Canadian provinces within an integrated system of equations. "An extended gravity model is the basis for the equation specification and the use of constrained econometric estimation techniques allows for the provincial interdependence of the migration decision while at the same time ensuring that an important system-wide requirement is respected." The model is estimated using official Canadian data for the 1960s and 1970s. "The results suggest the predominance of the push factor for interprovincial migration for most provinces, although net migration to the Atlantic provinces is also shown to be subject to pull forces from the rest of the country." The effects of wage rate variables, unemployment, and political disturbances in Quebec on inter-provincial migration are noted.