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  • 1
    Publication Date: 2014-02-26
    Description: We model a symmetric system of coupled oscillators as a graph with symmetry group $\gamma$. Each vertex of the graph represents an "oscillator" or a "cell" of reactants. The magnitude (concentration) of the reactants in the $ i $ th cell is represented by a vector $ x^i $. The edges represent the coupling of the cells. The cells are assumed to evolve by identical reaction-diffusion equation which depends on the sum of the reactants in the nearest neighbors. Thus the dynamics of the system is described by a nonlinear differential system \begin{flushleft} \[ \mbox {(*) \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ } \dot{x}^i = f (x^i,\sum_{j \in N_i} x^j), \mbox { \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ } \] \end{flushleft} where the sum ranges over the set $ N_i $ of neighbors of cell $ i $ . If $ f $ also has a symmetry (e.g., oddness), there are geometric conditions on the graph such that the nonlinear system $ (*) $ decouples globally into a product flow on certain sums of isotropy subspaces. Thus we may detect higher-dimensional tori of solutions of $ (*) $ which are not amenable to other types of analysis. We present a number of examples, such as bipartite graphs, complete graphs, the square, the octahedron, and a 6-dimensional cube.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 4 (1956), S. 708-711 
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Manuscripta mathematica 27 (1979), S. 159-166 
    ISSN: 1432-1785
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this note it will be shown how a theorem of Alexander [1] and Ize [9] together with computational results of Alexander and Yorke [4] and Alexander and Fitzpatrick [2] may be used to generalize the existence theorem for, and to prove some global results about, certain wave-like solutions of nonlinear systems of partial differential equations. The equations to be studied are weakly coupled parabolic systems of equations defined on a bounded axisymmetric domain. Such equations are often called reaction-diffusion equations (or interaction-diffusion equations) and arise in many parts of biology and chemistry. The question as to how wave-like solutions of these equations may bifurcate from a family of trivial solutions was studied by Auchmuty [5] and the results will be considerably extended here.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Mathematische Annalen 256 (1981), S. 429-437 
    ISSN: 1432-1807
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 37 (1982), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The statistical properties and applicability of the Dry-Weight-Rank (DWR) method of pasture sampling are examined. Formulae for the expected value and variance of the DWR estimates are presented.The extent of bias in DWR is examined using several mathematical models. DWR is shown to break down when estimating multinomial proportions; however it provides good estimates for a subset of models simulated from a class of compound probability distributions.The success of DWR in practice does not rest on a theoretical basis. It appears to be a remarkable empirical discovery that DWR estimates are virtually unbiased on most pasture types. Several cases are considered where difficulties may be encountered in using DWR. Provided the theoretical reservations of this paper are borne in mind, DWR will continue to be a useful practical tool, especially in the absence of non-destructive observational alternatives.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 28 (1963), S. 2522-2526 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 48 (1983), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cooking fats from a pressure deep-fat frying operation producing fried chicken, were compared with laboratory heated and fresh fats in the diets of animals. Included were corn oil (CO), peanut oil (PO), and partially hydrogenated soybean oil (HSBO). Weanling rats were fed diets containing 15% fat for 28 days. Laboratory heating reduced absorption of CO and PO, but not that of HSBO. Pressure deep-frying increased absorption of HSBO. Animals derived less metabolizable energy from diets containing heated or hydrogenated fats relative to fresh oil. Polar lipid fractions of liver changed due to heating. Pressure deep-frying with fats resulted in less deterioration than with laboratory heating, as shown by chemical analyses, coefficient of digestibility, and metabolizable energy studies.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 44 (1993), S. 189-200 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract Triple pulses are constructed for systems of two coupled reaction-diffusion equations with an asymptotically oscillatory single pulse. In (Alexander and Jones [1993]) it has been shown that an infinite sequence of double pulses can be constructed near the single pulse. Under the condition that the wave speed of a stable double pulse coincides with that of the single pulse, it is shown here that an infinite sequence of triple pulses can be constructed. These pulses have the form of the double pulse concatenated with a further single pulse far behind, and cannot be constructed in the same way for the situations considered by previous authors. Moreover, the pulses are shown to be alternately stable and unstable.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical biology 29 (1991), S. 405-423 
    ISSN: 1432-1416
    Keywords: Bursting ; Fast-slow decomposition ; Bifurcation ; Pancreatic β-cell model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The dynamics of three-variable models of bursting are studied. It is shown that under certain conditions, the dynamics on the attractor can be essentially reduced to two dimensions. The salient dynamics on the attractor can thus be completely described by the return map of a section which is a logistic interval map. Two specific bursting models from the literature are shown to fit in the general framework which is developed. Bifurcation of the full system for one case in investigated and the dynamical behavior on the attractor is shown to depend on the position of a certain nullcline.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical biology 23 (1986), S. 205-219 
    ISSN: 1432-1416
    Keywords: Coupled oscillators ; Diffuse instabilities ; Brusselator ; Glycolytic oscillations ; Hopf bifurcation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Mathematical examples are presented of oscillators with two variables which do not oscillate in isolation, but which do oscillate stably when coupled with a twin via difiusion. Two examples are presented, the LefeverPrigogine Brusselator and a system used to model glycolytic oscillations. The mathematical method is not the usual bifurcation theory, but rather a type of singular perturbation theory combined with bifurcation theory. For both examples, it is shown that all stationary solutions are unstable for appropriate parameter settings. In the case of the Brusselator, it is further shown that there exist limit cycles; i.e. stable oscillations, in this parameter range. A numerical example is presented.
    Type of Medium: Electronic Resource
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