Hierarchical Structure

5 Key excerpts on "Hierarchical Structure"

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  Evolving Hierarchical Systems

  Their Structure and Representation

  • Stanley N. Salthe(Author)
  • 2019(Publication Date)
  • Columbia University Press

    (Publisher)

  BASICS OF Hierarchical Structure 45 Pattee developed this view of complexity in the context of considering hierarchical systems. It is therefore not surpris-ing that, even though it is probably more widely applicable, it can be developed further in the context of the concept of scale. Note that, if a portion of a system (scale has already been intro-duced) has an internal representation of a portion of the sys-tem, we already have entities at three levels nested one within the other. A physical system is making its way as a part within a larger physical system using a smaller physical system (one of its parts) as a guide through, or map of, some portion(s) of the larger system (Roitblat 1982). The genome is the cell's guide through the pond. A molecular system is being used by a cellu-lar system to negotiate an ecosystem. The molecular system has the requisite informational entropy from the point of view of the cell so that it can store information about the environment-cell interaction. Viewed by an outside observer (the scientist) this situa-tion can be made explicit as three levels, each of which has an alternative description (Pattee 1970, 1972). The molecular level can be taken as a field of collisional energy-transferring activity of the molecules themselves or it can be alternatively described in terms of the kinds of effects aggregated molecular activity has on the cellular level as if it were being felt by the cell as a flow of foodstuffs, deformations of its liquid crystalline compartments, changes in pH, accumulation of waste products, and so on. Cellular activity in the pond can be described either in terms of escape from crowding, seeking mates, etc. or as changes in the density of cells or their products in various portions of the pond.

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  Hierarchical Organization in Society

  • James Pooler(Author)
  • 2017(Publication Date)
  • Taylor & Francis

    (Publisher)

  2 All about Hierarchies

  One thing that is truly fascinating about hierarchies is that they occur in nature, as well as in the human world. This is, however, perhaps not that surprising at all, given the usefulness of hierarchies as organizing systems for information and materials. Virtually every kind of complex system is organized hierarchically, and as we shall see in this chapter, there are a number of properties and characteristics that are common to all hierarchies.

  A hierarchy was defined in the first chapter as an organizational system that is structured in a treelike manner, with levels of status or authority stacked one above the another. Let's take a look at just what this means in a little more detail.

  Properties of Hierarchies

  The treelike hierarchy in Figure 2.1 has several interesting properties. These can be divided into three basic categories: physical properties, communications properties, and geographical properties.

  Physical Properties of Hierarchies

  First of all, under the topic of physical or visible characteristics of hierarchies we can note that there is a clear direction to a hierarchy. There is a definitive top and a definitive bottom. Second, the treelike shape shows us a large number of small branches at the bottom and a small number of large branches at the top. Small branches merge together to form larger branches, or alternatively, large branches split into smaller ones. Most hierarchies culminate in a single, final large branch. Third, there is an interesting logic to the connections in a hierarchy. Most of the levels in the hierarchy, except for the very top and very bottom ones, connect to both a lower level and a higher level. Thus we could say that many of the internal levels in a hierarchy are bi-directional having one link looking upwards and another link looking downwards. This property can be very important for individuals or corporations in the middle levels of a hierarchy.

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  Foundations of Mathematical Biology

  Subcellular Systems

  • Robert J. Rosen(Author)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  Structural hierarchies can often be distinguished by their graded size or by the way elements of a collec-tion are grouped. For example the atom, the molecule, the crystal, and the solid can be distinguished as structural levels by criteria of grouping and number; that is, each level is made up of large collection of the units of the lower level. However, there is a more fundamental physical hierarchy of forces underlying these groupings, the strongest forces being responsible for the smallest or lowest-level structures. The strongest force holds together the nuclei of the atoms, and the weakest force holds together the largest bodies of matter. There is also a corresponding hierarchy of dynamical time scales which may be associated with the levels of forces, the shortest time being related to the strongest force and smallest structures, and the longest time related to the weakest force and largest structures. It is because of the separability of these graded levels of numbers, forces, and time scales, or their partial decomposibility, as Simon [1962] calls it, that we can write fl do not think that discussion of the exact degree of reducibility of life to physics would be helpful here, although this remains a very profound question. To help the reader inter-pret my later remarks, however, I should say that on the one hand, according to my idea of physics, I do not believe that molecular biologists have now reduced life to physics and chemistry, which many have claimed [see, for example, Watson, 1965; Crick, 1966], or that they will have no difficulty in doing so [see, for example, Kendrew, 1967]. I have given my reasons for this belief elsewhere [Pattee, 1968, 1969a, b].

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  Theory of Hierarchical, Multilevel, Systems

  • M. D. Mesarovic, D. Macko, Y. Takahara(Authors)
  • 2000(Publication Date)
  • Elsevier Science

    (Publisher)

  It 2. Basic Types of Hierarchies 43 can be argued that explanation in terms of the elements on the same stratum is merely a description, while for proper functional understanding the description should be given in terms of the elements on lower, more detailed, strata. As Bradley [19] points out: It is a serial process: The biologist explains transmission of heredity in terms of DNA replication; the biochemist explains the replication in terms of the formation of complementary nucleotide base pairs; the chemist explains base pairing in terms of hydrogen bonding; the molecular physicist explains hydrogen bonds in terms of intermolecular potential functions; the quantum mechanician explains potential functions in terms of the wave equation. One is able, by referring to lower strata, to explain more precisely and in more detail how the system functions so as to carry out a certain operation. On the other hand, by moving up the hierarchy, the description becomes broader and refers to larger subsystems and longer periods of time. The meaning and significance of the subsystems’ operation is better interpreted in such a broader context. In the example of the text producing machine, one compre- hends the significance of the system’s operation only on the highest strata of a literary composition. In summary, it can be stated that for a proper understanding of complex systems, the hierarchical approach through stratified modeling is quite fundamental. Initially, one can confine his interest to one stratum, depending upon his interest and knowledge, and then increase his understanding of the system’s significance or functioning by moving, respectively, up or down the hierarchy. Selection of the initial stratum is also affected by the simpli- city of the description on that stratum. Layers : Levels of Decision Complexity Another concept of hierarchy appears in the context of a complex decision- making process.

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  Handbook of Nanophysics

  Nanoelectronics and Nanophotonics

  • Klaus D. Sattler(Author)
  • 2010(Publication Date)
  • CRC Press

    (Publisher)

  In fact, a Hierarchical Structure can be found in these broadcast interconnects by relating far-field effects at a coarser scale and near-field effects at a finer scale. In this regard, it should also be mentioned that such physi-cal differences in optical near-field and far-field effects can be used for a wide range of applications. The behavior of usual opti-cal elements, such as diffractive optical elements, holograms, or glass components, is associated with their optical responses in optical far fields. In other words, nanostructures can exist in such optical elements as long as they do not affect the optical responses in far fields. Designing nanostructures accessible only via optical near fields provides additional, or hidden, informa-tion recorded in those optical elements, while maintaining the original optical responses in far fields. In fact, a “ hierarchical hologram ” or “ hierarchical diffraction grating ” has been experi-mentally demonstrated, as schematically shown in Figure 34.5 (Tate et al. 2008). Since there is more hierarchy in the optical near-field regime, further applications should be possible, for example, it should be possible for nanometer-scale high-density systems to be gradu-ally hierarchically connected to coarse layer systems. Hierarchical functionalities are also important for several aspects of memory systems. One is related to recent high-density, huge-capacity memory systems, in which data retrieval or searching from entire memory archives is made even more dif-ficult. Hierarchy is one approach for solving such a problem by making systems hierarchical, that is, by recording abstract data, metadata, or tag data in addition to the original raw data. Hierarchy in nanophotonics provides a physical solution to achieve such functional hierarchy. As will be introduced below, low-density, rough information is read out at a coarser scale, whereas high-density, detailed information is read out at a finer scale.

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