Existing theories relating patterns of pedestrian and vehicular movement to urban form characterise the problem in terms of flows to and from 'attractor' land uses. This paper contains evidence in support of a new 'configurational' paradigm in which a primary property of the form of the urban grid is to privilege certain spaces over others for through movement. In this way it is suggested that the configuration of the urban grid itself is the main generator of patterns of movement. Retail land uses are then located to take advantage of the opportunities offered by the passing trade and may well act as multipliers on the basic pattern of 'natural movement' generated by the grid configuration. The configurational correlates of movement patterns are found to be measures of global properties of the grid with the 'space syntax' measure of 'integration' consistently found to be the most important. This has clear implications for urban design suggesting that if we wish to design for well used urban space, then it is not the local properties of a space that are important in the main but its configurational relations to the larger urban system.

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The concept of an isovist has had a long history in both architecture and geography, as well as mathematics. Tandy (1967) appears to have been the originator of the term isovist'. He presents isovists as a method of``taking away from the [architectural or landscape] site a permanent record of what would otherwise be dependent on either memory or upon an unwieldy number of annotated photographs'' (page 9). The same idea has a similarly long history in the guise of the`viewshed' in the field of landscape architecture and planning (Amidon and Elsner, 1968; Lynch, 1976) and in terms of intervisibility' in computer topographic models (Gallagher, 1972). The appeal of the concept is that isovists are an intuitively attractive way of thinking about a spatial environment, because they provide a description of the spacè from inside', from the point of view of individuals, as they perceive it, interact with it, and move through it. As such, isovists have particular relevance to architectural analysis. Benedikt (1979) introduced a set of analytic measurements of isovist properties to be applied to achieve quantitative descriptions of spatial environments. Benedikt starts by considering the volume visible from a location and then simplifies this representation by taking a horizontal slice through the`isovist polyhedron'. The resulting`isovists' are always single polygons without holes, as shown in figure 1 (see over). Consequently, Benedikt considers geometric properties of isovists, such as area and perimeter. Thus he begins to quantify space, or what our perception of space might be, and the potential for its use. Benedikt notes that, in order to quantify a whole configuration, more than a single isovist is required and he suggests that the way in which we experience a space, and how we use it, is related to the interplay of isovists. This leads

The sporadic form of mitochondrial myopathy is associated with somatic mutations in the cytochrome b gene of mtDNA. This myopathy is one cause of the common and often elusive syndrome of exercise intolerance.

Andersen's syndrome is a clinically distinct form of potassium-sensitive periodic paralysis associated with cardiac dysrhythmias. The subtle nature of the cardiac and dysmorphic features may delay the recognition of this syndrome and its potentially lethal cardiac dysrhythmias. The genetic defect in Andersen's syndrome is not genetically linked to other forms of potassium-sensitive periodic paralysis and is probably distinct from the long QT syndrome locus.

Space syntax research has found that spatial configuration alone explains a substantial proportion of the variance between aggregate human movement rates in different locations in both urban and building interior space. Although it seems possible to explain how people move on the basis of these analyses, the question of why they move this way has always seemed problematic because the analysis contains no explicit representations of either motivations or individual cognition. One possible explanation for the method’s predictive power is that some aspects of cognition are implicit in space syntax analysis. This article reviews the contribution made by syntax research to the understanding of environmental cognition. It proposes that cognitive space, defined as that space which supports our understanding of configurations more extensive than our current visual field, is not a metric space, but topological. A hypothetical process for deriving a nonmetric space from the metric visibility graph involving exploratory movement is developed. The resulting space is shown to closely resemble the axial graph.

IntroductionIn the literature on cognitive psychology, the issues raised by Gibson's ecological theory of perception (Gibson, 1979) have been examined and taken on board. Gibson's theory was formulated primarily in order to overturn theories laden with subjective and objective knowledge, and to replace them with a model in which the agent and its environment are conjoined by a set of affordances so the agent perceives the contents of the environment directly and uses the affordances within it to guide its action without reference to superior representational models. Today, Gibson's work has been contextualised and broken into further models in which recognition and representation do play a part (Neisser, 1994). However, in the domain of agent-based modelling we still appear to ignore the original concerns he voiced öin particular`the model' is always preceded by a theoretical framework, rather than simply being a perceptual model in its own right (see, for example, Casti, 1998;Epstein and Axtell, 1996). This paper is not an attempt to overturn the body of literature which already exists in agentbased modelling, although it does constitute a plea for the use of direct perception where the approach is available, and to try to regard the environment as the provider of possibilities rather than as a place to be rationalised. As an example, consider human movement around an art gallery. There might be any number of causal factors for the routes people take. People might, for example, follow a map, or signage, take into account the direction other people are taking, a glimpse of a familiar painting, reject a route on the grounds of personal prejudice against a style, and so on. On the other hand, the possibility of exploring the walkable surface of the layout ahead (the rooms of the gallery) may simply be enough for a human to do exactly that. Abstract. Gibson's ecological theory of perception has received considerable attention within psychology literature, as well as in computer vision and robotics. However, few have applied Gibson's approach to agent-based models of human movement, because the ecological theory requires that individuals have a vision-based mental model of the world, and for large numbers of agents this becomes extremely expensive computationally. Thus, within current pedestrian models, path evaluation is based on calibration from observed data or on sophisticated but deterministic route-choice mechanisms;there is little open-ended behavioural modelling of human-movement patterns. One solution which allows individuals rapid concurrent access to the visual information within an environment is an`exosomatic visual architecture', where the connections between mutually visible locations within a configuration are prestored in a lookup table. Here we demonstrate that, with the aid of an exosomatic visual architecture, it is possible to develop behavioural models in which movement rules originating from Gibson's principle of affordance are utilised. We apply large numbers of agents programmed with these r...

A retrospective study of 108 patients with myasthenia gravis who had solely ocular symptoms and signs at onset was carried out to identify factors influencing prognosis. Increasing duration of pure ocular myasthenia was associated with a decreasing risk of late generalized symptoms; only 9 (15%) of the observed generalizations occurred after more than 2 years of solely ocular symptoms. Increasing age at onset was associated with greater risk of respiratory crisis or death caused by myasthenia, whereas patients younger at onset had a greater chance of a benign outcome. Neither systemic curare tests nor responses to repetitive nerve stimulation had prognostic value.