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Measures of the effects of population pressure on the landscape using traditional methods for classifying urban territory are inadequate. The crude scale at which population densities are calculated and dependence on country-specific administration divisions hinder their ability to address such questions as the environmental impacts of cities and suburbs and make cross-national comparisons particularly difficult. This paper examines comparative urbanization measures among three case studies: the Pearl River Delta in Guangdong Province of China, the Indian state of Kerala, and the southern part of Florida in the United States. It proposes a measure based on the distribution of local population densities, taking advantage of the detailed data on small area populations and land area available in modern censuses and model-derived population databases such as LandScan, and the increasing potential of spatial analysis using geographic information systems (GIS). Examined with a similar set of thresholds, the resulting density distributions offer the potential to show better the ecological effects of population than do traditional measures.

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Applied geographers solve problems that inform decision-making and policy. The problems most often arise in government or the private sector, require practical, rapid, and cost-effective solutions, and are usually client-driven. Often, government or the private sector funds the research of applied geographers, and the research results have specific and usually current implications for government policies and programs or business strategies. Applied geographers use techniques, tools, methods, and concepts from the discipline of geography, but borrow liberally from other disciplines as necessary. This approach is well suited to solving problems that have multiple, not merely spatial, dimensions. As a subdiscipline of geography, applied geography has an ill-defined niche. Is applied geography a subdiscipline similar to biogeography, geomorphology, or economic geography? Or does it occupy an intermediary position within the discipline, synthesizing concepts from various subdisciplines? A certain ambiguity exists as to the point of origin of applied geography as a subdiscipline as well as whether it is even a distinct subdiscipline within geography (Hart 1989). The nature of applied geography has been a staple topic of discussion in professional papers and applied geography texts. Such discussions tend to focus on applied geography’s role within the discipline and what differentiates applied geographers from other geographers. Kenzer (1989) provides an excellent and lively account, in part noting that aspects of the discussion are bound up in the historic differences between academic and non-academic (professional) geographers. Kenzer and the contributors to the volume he edited provide plenty of grist for discussion. Over the past twenty years considerable interest has been attracted toward this discussion. In particular, we draw attention to work by Frazier (1982), Kenzer (1989), Hart (1989), Palm and Brazel (1992), Johnston (1993); Frazier et al. (1995), Harvey (1997), and Golledge et al. (1997) for discussions of the origins, purpose, and focus of applied geography. For the purposes of this review, applied geography is treated as one of many subdisciplines or specialties. Notwithstanding attaining the status of a subdiscipline, however, there is no single body of research that applied geographers can point to as clearly their own.

CNS demyelinating disorders encompass a wide spectrum of syndromes affecting the integrity of myelin in the brain. These disorders can be classified into primary and secondary processes with secondary causes being further subclassified into infectious, alcohol-related, iatrogenic/toxic, and vascular, depending on the etiology. Unfortunately, the imaging appearances of the resulting white matter lesions are often nonspecific in nature. An understanding of the clinical features and parenchymal patterns of involvement of demyelinating diseases is essential to permit the radiologist to generate a narrow differential diagnosis, which the clinician can refine further with knowledge of the patient's history and laboratory testing. This pictorial review presents the imaging features of demyelinating disorders. Imaging features allowing their optimal differentiation will be discussed.