1,345 research outputs found
Transition from anticipatory to lag synchronization via complete synchronization in time-delay systems
The existence of anticipatory, complete and lag synchronization in a single
system having two different time-delays, that is feedback delay and
coupling delay , is identified. The transition from anticipatory to
complete synchronization and from complete to lag synchronization as a function
of coupling delay with suitable stability condition is discussed. The
existence of anticipatory and lag synchronization is characterized both by the
minimum of similarity function and the transition from on-off intermittency to
periodic structure in laminar phase distribution.Comment: 14 Pages and 12 Figure
Global phase synchronization in an array of time-delay systems
We report the identification of global phase synchronization (GPS) in a
linear array of unidirectionally coupled Mackey-Glass time-delay systems
exhibiting highly non-phase-coherent chaotic attractors with complex
topological structure. In particular, we show that the dynamical organization
of all the coupled time-delay systems in the array to form GPS is achieved by
sequential synchronization as a function of the coupling strength. Further, the
asynchronous ones in the array with respect to the main sequentially
synchronized cluster organize themselves to form clusters before they achieve
synchronization with the main cluster. We have confirmed these results by
estimating instantaneous phases including phase difference, average phase,
average frequency, frequency ratio and their differences from suitably
transformed phase coherent attractors after using a nonlinear transformation of
the original non-phase-coherent attractors. The results are further
corroborated using two other independent approaches based on recurrence
analysis and the concept of localized sets from the original non-phase-coherent
attractors directly without explicitly introducing the measure of phase.Comment: 11 pages, 13 figures, Appear in Physical Review
Phase synchronization in time-delay systems
Though the notion of phase synchronization has been well studied in chaotic
dynamical systems without delay, it has not been realized yet in chaotic
time-delay systems exhibiting non-phase coherent hyperchaotic attractors. In
this article we report the first identification of phase synchronization in
coupled time-delay systems exhibiting hyperchaotic attractor. We show that
there is a transition from non-synchronized behavior to phase and then to
generalized synchronization as a function of coupling strength. These
transitions are characterized by recurrence quantification analysis, by phase
differences based on a new transformation of the attractors and also by the
changes in the Lyapunov exponents. We have found these transitions in coupled
piece-wise linear and in Mackey-Glass time-delay systems.Comment: 4 pages, 3 Figures (To appear in Physical Review E Rapid
Communication
Iron environment non-equivalence in both octahedral and tetrahedral sites in NiFe2O4 nanoparticles: study using Mössbauer spectroscopy with a high velocity resolution
Mössbauer spectrum of NiFe2O4 nanoparticles was measured at room temperature in 4096 channels. This spectrum was fitted using various models, consisting of different numbers of magnetic sextets from two to twelve. Non-equivalence of the 57Fe microenvironments due to various probabilities of different Ni2+ numbers surrounding the octahedral and tetrahedral sites was evaluated and at least 5 different microenvironments were shown for both sites. The fit of the Mössbauer spectrum of NiFe 2O4 nanoparticles using ten sextets showed some similarities in the histograms of relative areas of sextets and calculated probabilities of different Ni2+ numbers in local microenvironments. © 2012 American Institute of Physics
Experimental confirmation of chaotic phase synchronization in coupled time-delayed electronic circuits
We report the first experimental demonstration of chaotic phase
synchronization (CPS) in unidirectionally coupled time-delay systems using
electronic circuits. We have also implemented experimentally an efficient
methodology for characterizing CPS, namely the localized sets. Snapshots of the
evolution of coupled systems and the sets as observed from the oscilloscope
confirming CPS are shown experimentally. Numerical results from different
approaches, namely phase differences, localized sets, changes in the largest
Lyapunov exponents and the correlation of probability of recurrence
(), corroborate the experimental observations.Comment: Physical_Review_E_82_065201(R) 201
Transition from phase to generalized synchronization in time-delay systems
The notion of phase synchronization in time-delay systems, exhibiting highly
non-phase-coherent attractors, has not been realized yet even though it has
been well studied in chaotic dynamical systems without delay. We report the
identification of phase synchronization in coupled nonidentical piece-wise
linear and in coupled Mackey-Glass time-delay systems with highly
non-phase-coherent regimes. We show that there is a transition from
non-synchronized behavior to phase and then to generalized synchronization as a
function of coupling strength. We have introduced a transformation to capture
the phase of the non-phase coherent attractors, which works equally well for
both the time-delay systems. The instantaneous phases of the above coupled
systems calculated from the transformed attractors satisfy both the phase and
mean frequency locking conditions. These transitions are also characterized in
terms of recurrence based indices, namely generalized autocorrelation function
, correlation of probability of recurrence (CPR), joint probability of
recurrence (JPR) and similarity of probability of recurrence (SPR). We have
quantified the different synchronization regimes in terms of these indices. The
existence of phase synchronization is also characterized by typical transitions
in the Lyapunov exponents of the coupled time-delay systems.Comment: Accepted for publication in CHAO
Chemical composition and antibacterial activity of essential oil from the leaves of Murraya koenigii (L.) Spreng.
Chemical composition and antibacterial activity of the leaf essential oil of Murraya koenigii were investigated against clinically isolated bacterial strains. Fourteen compounds were identified by GC and GC-MS accounting for about 98.1% of the total essential oil. a-pinene (49.3%), 2H-1-benzopyran (24.3%), 2-allyl-4-methylphenol (16.7%) and D-isomenthol (2.1%) were identified as the major chemical compounds. The essential oil produced mean zone of inhibition ranged between 14.0 and 7.6 mm. The essential oil showed antibacterial activity against all the bacterial strains tested with the MIC values of 125-500 µg/ml. Although, the activity of the essential oil against the clinical isolates were much less than of Ciprofloxacin, the standard drug used, the demonstrated antibacterial activities of M. koenigii leaf essential may support the folkloric uses of the plant.Â
Isolation of mosquito larvicidal molecule form the leaves of Clausena anista
The vector-borne diseases caused by mosquitoes are one of the major health problems in many countries especially in tropical and sub-tropical countries. The resistance of mosquitoes to synthetic chemicals and environmental toxicity created by the chemicals raised the demand for finding of alternate natural molecules that control mosquito. In the present study, the compound 1, 2-Benzenedicarboxylic acid, mono (2-ethylhexyl) ester was isolated from the ethyl acetate extract of leaves of Clausena anisata and it was identified by various spectral studies. The larvicidal potential of the isolated compound was evaluated against early 4th instar larvae of Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi. The compound exhibited 100% larval mortality against A. aegypti and A. stephensi at 40 ppm with LC50 values of 8.944 and 9.230 ppm respectively. The molecule also showed the LC50 value of 12.067 ppm against C. quinquefasciatus. The molecule isolated from C. anisata can be better explored for the control of mosquito population after toxicological evaluation
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