1,449 research outputs found
Periodic solutions for planar autonomous systems with nonsmooth periodic perturbations
In this paper we consider a class of planar autonomous systems having an
isolated limit cycle x_0 of smallest period T>0 such that the associated
linearized system around it has only one characteristic multiplier with
absolute value 1. We consider two functions, defined by means of the
eigenfunctions of the adjoint of the linearized system, and we formulate
conditions in terms of them in order to have the existence of two geometrically
distinct families of T-periodic solutions of the autonomous system when it is
perturbed by nonsmooth T-periodic nonlinear terms of small amplitude. We also
show the convergence of these periodic solutions to x_0 as the perturbation
disappears and we provide an estimation of the rate of convergence. The
employed methods are mainly based on the theory of topological degree and its
properties that allow less regularity on the data than that required by the
approach, commonly employed in the existing literature on this subject, based
on various versions of the implicit function theorem.Comment: To appear in J. Math. Anal. App
Synchronization problems for unidirectional feedback coupled nonlinear systems
In this paper we consider three different synchronization problems consisting
in designing a nonlinear feedback unidirectional coupling term for two
(possibly chaotic) dynamical systems in order to drive the trajectories of one
of them, the slave system, to a reference trajectory or to a prescribed
neighborhood of the reference trajectory of the second dynamical system: the
master system. If the slave system is chaotic then synchronization can be
viewed as the control of chaos; namely the coupling term allows to suppress the
chaotic motion by driving the chaotic system to a prescribed reference
trajectory. Assuming that the entire vector field representing the velocity of
the state can be modified, three different methods to define the nonlinear
feedback synchronizing controller are proposed: one for each of the treated
problems. These methods are based on results from the small parameter
perturbation theory of autonomous systems having a limit cycle, from nonsmooth
analysis and from the singular perturbation theory respectively. Simulations to
illustrate the effectiveness of the obtained results are also presented.Comment: To appear in Dyn. Contin. Discrete Impuls. Syst., Ser. A, Math. Ana
Periodic solutions of periodically perturbed planar autonomous systems: A topological approach
Aim of this paper is to investigate the existence of periodic solutions of a
nonlinear planar autonomous system having a limit cycle x_0 of least period
T_0>0 when it is perturbed by a small parameter, T_1-periodic, perturbation. In
the case when T_0/T_1 is a rational number l/k, with l, k prime numbers, we
provide conditions to guarantee, for the parameter perturbation e>0
sufficiently small, the existence of klT_0-periodic solutions x_e of the
perturbed system which converge to the trajectory x_1 of the limit cycle as
e->0. Moreover, we state conditions under which T=klT_0 is the least period of
the periodic solutions x_e. We also suggest a simple criterion which ensures
that these conditions are verified. Finally, in the case when T_0/T_1 is an
irrational number we show the nonexistence, whenever T>0 and e>0, of T-periodic
solutions x_e of the perturbed system converging to x_1. The employed methods
are based on the topological degree theory
A continuation principle for a class of periodically perturbed autonomous systems
In this paper we evaluate the topological index of periodic solutions otained
via the Malkin-Loud bifurcation result. Incidentally, we do not assume that the
perturbation is differentiale.Comment: Accepted to Math. Nachr., Vol. 281, (2008), No.
Periodic bifurcation from families of periodic solutions for semilinear differential equations with Lipschitzian perturbations in Banach spaces
Let A:D(A)\to E be an infinitesimal generator either of an analytic compact
semigroup or of a contractive C_0-semigroup of linear operators acting in a
Banach space E. In this paper we give both necessary and sufficient conditions
for bifurcation of -periodic solutions for the equation x'=Ax+f(t,x)+e
g(t,x,e) from a k-parameterized family of T-periodic solutions of the
unperturbed equation corresponding to e=0. We show that by means of a suitable
modification of the classical Mel'nikov approach we can construct a bifurcation
function and to formulate the conditions for the existence of bifurcation in
terms of the topological index of the bifurcation function. To do this, since
the perturbation term g is only Lipschitzian we need to extend the classical
Lyapunov-Schmidt reduction to the present nonsmooth case.Comment: Submitted to Adv. Nonlinear Stu
On the behavior of periodic solutions of planar autonomous Hamiltonian systems with multivalued periodic perturbations
Aim of the paper is to provide a method to analyze the behavior of
-periodic solutions x_\eps, \eps>0, of a perturbed planar Hamiltonian
system near a cycle , of smallest period , of the unperturbed system.
The perturbation is represented by a -periodic multivalued map which
vanishes as \eps\to0. In several problems from nonsmooth mechanical systems
this multivalued perturbation comes from the Filippov regularization of a
nonlinear discontinuous -periodic term. \noindent Through the paper,
assuming the existence of a -periodic solution x_\eps for \eps>0 small,
under the condition that is a nondegenerate cycle of the linearized
unperturbed Hamiltonian system we provide a formula for the distance between
any point and the trajectories x_\eps([0,T]) along a transversal
direction to $x_0(t).
Non-trivial, non-negative periodic solutions of a system of singular-degenerate parabolic equations with nonlocal terms
We study the existence of non-trivial, non-negative periodic solutions for
systems of singular-degenerate parabolic equations with nonlocal terms and
satisfying Dirichlet boundary conditions. The method employed in this paper is
based on the Leray-Schauder topological degree theory. However, verifying the
conditions under which such a theory applies is more involved due to the
presence of the singularity. The system can be regarded as a possible model of
the interactions of two biological species sharing the same isolated territory,
and our results give conditions that ensure the coexistence of the two species.Comment: 39 page
Desensitization properties of P2X3 receptors shaping pain signaling
ATP-gated P2X3 receptors are mostly expressed by nociceptive sensory neurons and participate in transduction of pain signals. P2X3 receptors show a combination of fast desensitization onset and slow recovery. Moreover, even low nanomolar agonist concentrations unable to evoke a response, can induce desensitization via a phenomenon called "high affinity desensitization." We have also observed that recovery from desensitization is agonist-specific and can range from seconds to minutes. The recovery process displays unusually high temperature dependence. Likewise, recycling of P2X3 receptors in peri-membrane regions shows unexpectedly large temperature sensitivity. By applying kinetic modeling, we have previously shown that desensitization characteristics of P2X3 receptor are best explained with a cyclic model of receptor operation involving three agonist molecules binding a single receptor and that desensitization is primarily developing from the open receptor state. Mutagenesis experiments suggested that desensitization depends on a certain conformation of the ATP binding pocket and on the structure of the transmembrane domains forming the ion pore. Further molecular determinants of desensitization have been identified by mutating the intracellular N- and C-termini of P2X3 receptor. Unlike other P2X receptors, the P2X3 subtype is facilitated by extracellular calcium that acts via specific sites in the ectodomain neighboring the ATP binding pocket. Thus, substitution of serine275 in this region (called "left flipper") converts the natural facilitation induced by extracellular calcium to receptor inhibition. Given their strategic location in nociceptive neurons and unique desensitization properties, P2X3 receptors represent an attractive target for development of new analgesic drugs via promotion of desensitization aimed at suppressing chronic pain. \ua9 2013 Giniatullin and Nistri
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