A simulation of the transmission of HIV and AIDS in regional populations within the United Kingdom

"The spread of HIV-1 in the United Kingdom is simulated by a model which integrates behavioural and epidemiological processes within a multi-regional population projection framework and represents the spatial heterogeneities in the distribution of HIV which have significant effects on transmission patterns. Analyses determine the significance of different parameters in contributing to prediction uncertainty and highlight the importance of behavioural change and international population movements."     

Markov Models of Inertia and Dynamism on Two Contiguous Ohio Landscapes

This study examined landcover change during 1940–1988 in two contiguous landscapes of approximately 12,400 hectares in central Ohio, USA: an inertial till plain area and a more dynamic moraine area. Agriculture dominated both landscapes throughout, however, the cover of natural vegetation and urban-suburban development increased over time on the moraine while natural vegetation decreased and agriculture increased on the till plain. Markov process models for landcover change were constructed for three 14–17-year time intervals and for the entire forty-eight-year study period. Probabilities of self-replacement for agricultural lands (0.91–0.97) were higher and those for forests (0.54–0.65) lower than those reported for other landscapes. Predictions of landcover percentages for fifty years in the future were made using Markov process models derived from actual cover changes in 1940–1957, 1971–1988, and 1940–1988. All three models produced similar predictions for the inertial till plain area. In contrast, the three models' predictions differed considerably for the moraine area. Only the 1971–1988 transition matrix was sensitive to increases in urbanization and reforestation which began on the moraine in the 1970s. These results indicate that reliance on lengthy study intervals and net rates of change can obscure spatial and temporal patterns of landcover change that are caused by natural and socioeconomic factors operating on shorter time scales.     

A Little Bit of Dirt

An examination of the surface deposit of an Etruscan cup said to have been dug up in Cheshire suggests instead that it had been buried in Italy and brought to England in recent times. The method described here might usefully be employed to assess the provenance of buried artefacts.     

For Whom is the Rural Economy Resilient? Initial Effects of Drought in Western Sudan

This discussion piece addresses two recent debates: entitlement theory and the resilience of rural systems. The authors find that in western Sudan entitlement theory provides a specific and useful framework for understanding the nature of the crisis confronting the society. Arguments about the resilience of rural systems, however, need to be more closely examined and will depend on site-specific factors. The rural economy and society of western Sudan were not found to be resilient.     

Demand in the Spatial Economy: II Homo Stochasticus

Probabilistic preferences and choices and their connections to trip making and to distance-related demand are discussed. They are seen to aid aggregation. Risk aversion in retail shopping behavior and entropy maximizing as rational random behavior are examined. Elasticity of substitution is presented in terms of the covariance matrix. A Markovian phrasing and potential theory allow an analogy with deterministic choice: various applications of potential operators are outlined. Changes in utilities can only be modeled stochastically and some mechanisms are detailed. Price changes are random walked in time and space as a diffusion process. A fairly coherent theory of spatial demand emerges