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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 45 (1983), S. 483-506 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Qualitative theory for multidimensional stochastic dynamical models $$\dot x = f(x, \xi )$$ is presented where the random influences ξ may be white or colored, i.e. a (possibly bounded) diffusion process. We concentrate on transience, stationary solutions and boundary behavior and discuss a set-up for reliable simulations. The method consists in associating a deterministic control system where the (approximate) controllability properties determine the qualitative behavior of the stochastic system. Applications to some biological systems indicate the usefulness of qualitative theory in life sciences.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 53 (1991), S. 579-589 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A mathematical model (Kliemann, W. 1987.Bull. math. Biol. 49, 135–152.) that predicts the quantitative branching pattern of dendritic tree was evaluated using the apical and basal dendrites of rat hippocampal neurons. The Wald statistics for χ2-test was developed for the branching pattern of dendritic trees and for the distribution of the maximal order of the tree. Using this statistic, we obtained a reasonable, but not excellent, fit of the mathematical model for the dendritic data. The model's predictability of branching patterns was greatly enhanced by replacing one of the assumptions used for the original model “splitting of branches for all dendritic orders is stochastically independent”, with a new assumption “branches are more likely to split in areas where there is already a high density of branches”. The modified model delivered an excellent fit for basal dendrites and for the apical dendrites of hippocampal neurons from young rats (30–34 days postpartum). This indicates that for these cells the development of dendritic patterns is the result of a purely random and a systematic component, where the latter one depends on the density of dendritic branches in the brain area considered. For apical dendrites there is a trend towards decreasing pattern predictability with increasing age. This appears to reflect the late arrival of afferents and subsequent synaptogenesis proximal on the apical dendritic tree of hippocampal neurons.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied mathematics & optimization 20 (1989), S. 113-130 
    ISSN: 1432-0606
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract For smooth nonlinear systems $$\dot x(t) = X_0 (x(t)) + \sum\limits_{i = 1}^r {u_i (t)X_i (x(t)),}$$ the infinite time optimal control problems: maximize $$\mathop {\lim \sup }\limits_{T \to \infty } \frac{1}{T}\int_0^T {g(x(t)), u(t)) dt}$$ (average yield criterion) or $$\mathop {\lim }\limits_{T \to \infty } \int_0^T {e^{ - \delta l} g(x(t), u(t)) dt}$$ (discounted criterion) are considered, where the initial valuex(0) may be free or restricted. We study the existence of optimal periodic solutions for the above problems: if approximately optimal solutions have a limit point in the interior of some control set, then there exist approximately optimal periodic solutions. This result is applied to the growth of linear control semigroups and to a three-dimensional predator-prey harvesting model.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of dynamics and differential equations 5 (1993), S. 495-528 
    ISSN: 1572-9222
    Keywords: semilinear control systems ; bilinear control systems ; linear control semigroups ; control sets ; chain control sets ; control flows on vector bundles ; 93B05 ; 93C10 ; 58F25 ; 58F12 ; 34C35
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Linear control semigroupsL⊂=Gl(d,R) are associated with semilinear control systems of the form whereA:R m → gl(d,R) is continuous in some open set containingU. The semigroupL then corresponds to the solutions with piecewise constant controls, i.e., L acts in a natural way onR d {0}, on the sphereS d−1, and on the projective spaceP d−1. Under the assumption that the group generated byL in Gl(d,R) acts transitively onP d−1, we analyze the control structure of the action ofL onP d−1: We characterize the sets inP d−1, where the system is controllable (the control sets) using perturbation theory of eigenvalues and (generalized) eigenspaces of the matrices g εL For nonlinear control systems on finitedimensional manifoldsM, we study the linearization on the tangent bundleTM and the projective bundleP M via the theory of Morse decompositions, to obtain a characterization of the chain-recurrent components of the control flow onU×PM. These components correspond uniquely to the chain control sets onP M, and they induce a subbundle decomposition ofU×TM. These results are used to characterize the chain control sets ofL acting onP d−1 and to compare the control sets and chain control sets.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of dynamics and differential equations 5 (1993), S. 469-494 
    ISSN: 1572-9222
    Keywords: Control systems ; dynamical systems ; control sets ; topological mixing ; chain recurrence ; recurrence ; invariant measures ; 93C10 ; 93B05 ; 58F11
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Consider the smooth control system (C) $$\dot x = X_0 (x) + \sum\limits_{i = 1}^m {u_i X_i (x)}$$ on a manifold M with admissible controlsu εU={u:R →U, locally integrable} and compact control spaceU ⊂R m. Associated with (C) is a dynamical system whereθ t is the shift byt ε R to the right onU, andϕ(t, x, u) is the solution of (C) at timet ε R with initial condition ϑ(0,x, u) = x, under the control action of uεU We discuss some connections between control properties of (C) and basic notions for dynamical systems, such as topological mixing, chain recurrence, recurrence, invariant (ergodic) measures, and their support. It turns out that these concepts for (D) are related to the control sets and chain control sets of (C): A setD ⊂M is a control set of (C) iff the liftD=cl{(u, x) εU ×M,ϕ(t, x, u) ε D for allt ε R} toU×M is a maximal topologically mixing (transitive) component ofφ, similarly for the lifts of chain control sets and the components of the chain recurrent set ofφ. Furthermore, ifμ is an ergodic, invariant measure ofφ, thenπ M(suppμ) ⊂=D for some control setD ⊂M, and the pointsx ε M that are contained in control sets, are the projections ontoM ofφ-recurrent points.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 49 (1987), S. 135-152 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Under certain basic assumptions the branching pattern of dendrites can be modeled as a Galton-Watson process in varying environment. Using results from graph theory we compute the probability distributions, expectations and variances for biologically significant variables such as the number of (intermediate and terminal) branches, the maximum number of orders, etc., together with the limit behavior of these quantities. Furthermore, the probability measure induced by the Galton-Watson process on the set of all trees is calculated. The measure assigns to any set of branching patterns the probability that it is realized by a certain process, which is completely described through the bifurcation probabilities.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Nonlinear dynamics 5 (1994), S. 353-373 
    ISSN: 1573-269X
    Keywords: Bifurcation ; stationary Markov solutions ; stationary flow solutions ; control sets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Random perturbations of one dimensional bifurcation diagrams can exhibit qualitative behavior that is quite different from that of the unperturbed, deterministic situation. For Markov solutions of one dimensional random differential equations with bounded ergodic diffusion processes as perturbations, effects like disappearance of stationary Murkov solutions (‘break through’), slowing down, bistability, and random symmetry breaking can occur. These effects are partially the results of local considerations, but as the perturbation range increases, global dynamics can alter the picture as well. The results are obtained via the analysis of stationary solutions of degenerate Markov diffusion processes, of stationary, non-Markovian solutions of stochastic flows, and of Lyapunov exponents of stochastic flows with respect to steady states.
    Type of Medium: Electronic Resource
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  • 8
    Title: Delay and differential equations: Proc. in honor of George Seifert on his retirement
    Contributer: Fink, A. M. , Miller, Richard K. , Kliemann, Wolfgang
    Publisher: London u.a. :World Scientific,
    Year of publication: 1992
    Pages: 166 S.
    Type of Medium: Book
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