Contagious Diffusion

3 Key excerpts on "Contagious Diffusion"

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  Encyclopedia of Geography Terms, Themes, and Concepts

  • Reuel R. Hanks(Author)
  • 2011(Publication Date)
  • ABC-CLIO

    (Publisher)

  spread contagiously, especially in the era of visual media and the Internet, when mil- lions of people have almost instantaneous access to outlets that follow and promote the latest trends. In 1964, the Beatles first appeared on the Ed Sullivan show, an immensely popular variety show watched by millions of Americans, and their longer haircuts immediately caused controversy. But within a few months, thou- sands of young American men were wearing their hair in a similar style and donning “Nehru jackets” that the Beatles often wore while performing. The British quartet had changed American cultural standards and behavior almost overnight. Before the advent of mass visual media, Contagious Diffusion of ideas or practices generally required person-to-person contact. A second example of this type of diffusion is the spreading of proselytizing religions that seek mass conversion of a population. Both Islam and Christianity historically diffused when a few believers from these faiths encountered nonbelievers, converted them, and they in turn converted additional followers in a classic sequence of Contagious Diffusion based on personal contact. One of the most influential theoreticians in cultural geography regarding the concept of diffusion was the late Torsten Hagerstrand, who developed statistical models that illustrate how diffusion operates in space. His theory rests heavily on a core and periphery framework, which he employs to explain why new ideas and cultural trends, which could possibly arise at any point in space, tend to con- centrate and thereby create core areas and corresponding peripheral regions. A neighborhood effect also influences the movement of cultural traits through space at the local scale, when an individual acquires the new trait and then influences those near him, including his family and immediate neighbors.

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  Models in Spatial Analysis

  • Lena Sanders(Author)
  • 2013(Publication Date)
  • Wiley-ISTE

    (Publisher)

  A brief terminology reminder will be useful in introducing the chapter. Generally, by diffusion we mean the action, and the result of the action, of propagating an object in a homogenous way or transmitting the object or a phenomenon in a system whatever the propelling power. At the end of the process, the system is saturated. Its absorption capabilities are exhausted. The system invested by this action tends to go from one state to another. The notion of diffusion is therefore mobilized every time we study processes that involve movements of matter, products, people, intangible goods, practices or ideas for penetrating a system. Due to this, the diffusion processes are addressed by physical as well as biological and human sciences.

  Social sciences in general and geography in particular often associate diffusion and innovation (see Box 5.1 ). In its most trivial sense, innovation simply represents the newest thing (material or intangible) that, when it appears for the first time, is adopted by a person or a group. We have also studied the diffusion of contagious illnesses as well as of objects (such as, for example, a form of housing, a mode of transport, a new industrial product, an agricultural technique) and of intangible goods (for example, a type of economic development, a religious or a linguistic practice, a social model, etc.) which are all new things appearing at different places where they were not present before. In its strongest sense, innovating means introducing something new into an established thing, which can transform it. Thus defined, the innovation generates, by propagating, irreversibilities in the evolution of the environment that it penetrates [SCH 34]. The more complex it is, the more its diffusion will become a determining component in the transformation of the environment in which it appeared due to the growth of the induced effects that its adoption generates. Even if diffusion processes can be located and simulated for any new phenomenon that spreads over a system, the interest that is consistently given to these processes stems from the structuring effects that some of them hold.

  The spatio-temporal dimension of the diffusion process understood through the notion of spatial diffusion is considered when the diffusion is done in spatial systems. The elements of the system concerned by the innovation are identified by, among other things, their location. The focus of this chapter is the notion of spatial diffusion which covers all the processes competing for the movement and the migration of the innovation in the geographical space and for the effects that these movements generate in that space.

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  Complex Population Dynamics: Nonlinear Modeling In Ecology, Epidemiology And Genetics

  Nonlinear Modeling in Ecology, Epidemiology and Genetics

  • Bernd Blasius, Juergen Kurths, Lewi Stone(Authors)
  • 2007(Publication Date)
  • World Scientific

    (Publisher)

  The most prominent example is the bubonic plague pandemic of the 14th century which crossed the European continent as a wave within three years at an approximate speed of a few kilometers per day. Aside from factors which are known to play a role, such as social contact networks, age structure, inhomogeneities in local populations and inhomogeneities in the geographic distribution of the population, there is something fundamentally wrong with the diffusion assumption on which this class of equations is based upon. Humans (with the exception maybe of nomads) do not and never did diffuse on timescales of their lifespan. A simple argument can be given why this cannot be so. 112 D. Brockmann and L. Hufnagel Fig. 5.1. Human travel and the dispersal of pathogens. The gray areas depict home ranges of individuals. By virtue of overlapping home ranges and inter-homerange travel an infectious disease spreads in space. Although humans travel back and forth between home ranges, pathogens spread continuously in space. For a diffusion process the expected time for returning to the point of origin is infinite 19 (despite the fact that in spatial dimensions d ≤ 2 the probability of returning is unity). It would not make much sense to have a home if the expected time to return to it is infinite. However, in the context of the geographic spread of infectious diseases it does at times make sense to employ reaction-diffusion equations. That is because the position of what is passed from human to human, i.e. the pathogens, is what matters and not the position of single host individuals. Unlike humans, pathogens are passed from human to human and opposed to humans pathogens have no inclination of returning. They disperse diffusively and a description in terms of reaction-diffusion dynamics is justified, see Fig.

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