Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “bistability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,315 records · Page 73Linked to original sources
PubMed2002

Defect turbulence in inclined layer convection.

We report experimental results on the defect turbulent state of undulation chaos in inclined layer convection of a fluid with Prandtl number approximately 1. By measuring defect density and undulation wave number, we find that the onset of undulation chaos coincides with the theoretically predicted onset for stable, stationary undulations. At stronger driving, we observe a competition between ordered undulations and undulation chaos, suggesting bistability between a fixed-point attractor and spatiotemporal chaos. In the defect turbulent regime, we measured the defect creation, annihilation, entering, leaving, and rates. We derive a universal probability distribution function which agrees with the experimental findings.

Journal Article↗
PubMed2002

Autonomous swinging of a lipid tubule under stationary irradiation by a Nd3+:YAG laser.

A micrometer-sized lipid tubule exhibits oscillatory swinging motion under stationary irradiation by a Nd(3+):YAG laser ( lambda = 1064 nm). By choosing an appropriate optical path through an objective lens, the laser can be split into dual beams focused on the same position. Using this splitting, a lipid tubule can be shown to exhibit bistability with regard to the orientation of trapping. Driven by a temperature gradient induced by local photon heating, the trapped lipid tubule shows oscillatory motion between two possible orientations. This oscillatory phenomenon of the lipid tubule is thought to represent the breaking of time-translational symmetry under thermodynamically open conditions.

Journal Article↗
PubMed2002

Supercurrent through hybrid junctions with anisotropic Cooper-pair condensates.

A general formula for the supercurrent between different internal structures in a wide class of hybrid junctions is derived on the basis of the Andreev-reflection picture. The formula extends existing formulas and also enables us to analyze novel B-phase/A-phase/B-phase junctions in superfluid 3He systems. We propose a mechanism for pi states due to the (circumflex)l texture in the A phase of the junction, which could elucidate major features of the pi states with higher critical current ( H states) discovered in superfluid 3He weak links. The bistability of the pi states is also discussed.

Journal Article↗
PubMed2002

Decoherence and 1/f noise in Josephson qubits.

We propose and study a model of dephasing due to an environment of bistable fluctuators. We apply our analysis to the decoherence of Josephson qubits, induced by background charges present in the substrate, which are also responsible for the 1/f noise. The discrete nature of the environment leads to a number of new features which are mostly pronounced for slowly moving charges. Far away from the degeneracy this model for the dephasing is solved exactly.

Journal Article↗
PubMed2002

Oscillatory decay of a two-component bose-einstein condensate.

We study the decay of a two-component Bose-Einstein condensate with negative effective interaction energy. With a decreasing atom number due to losses, the atom-atom interaction becomes less important and the system undergoes a transition from a bistable Josephson regime to the monostable Rabi regime, displaying oscillations in phase and number. We study the equations of motion and derive an analytical expression for the oscillation amplitude. A quantum trajectory simulation reveals that the classical description fails for low loss rates, as expected from analytical considerations. Observation of the proposed effect will provide evidence for negative effective interaction.

Journal Article↗
PubMed2002

Curvature instability in passive diffractive resonators.

We study the stability of localized structures in a passive optical bistable system. We show that there is a critical value of the input field intensity above which localized structures are unstable with respect to a curvature instability. Beyond this instability boundary, a transition from the localized branch of solutions to stable hexagons is found.

Journal Article↗
PubMed2002

High-intensity laser-field amplification between two foils.

Interaction of two oppositely directed ultraintense laser pulses with two closely placed thin foils is modeled analytically and investigated by particle-in-cell simulation. It is shown that laser energy can be trapped and accumulated between the foils. The intensity could reach a 100-fold that of the pump lasers. The trapping is found to be bistable and the parameters for stable energy confinement and enhancement are given. The ultrahigh fields that can be produced have many potential applications, including that of verifying nonlinear quantum electrodynamics effects.

Journal Article↗
PubMed2002

Structure, properties, and dynamics of oxygen vacancies in amorphous SiO2.

Oxygen vacancies in SiO2 have long been regarded as bistable, forming a Si-Si dimer when neutral and a puckered configuration when positively charged. We report first-principles calculations of O vacancies in amorphous SiO2 supercells that unveil significantly more complex behavior. We find that the vast majority of O vacancies do not pucker after capture of a hole, but are shallow traps. The remaining vacancies exhibit two distinct types of puckering. Upon capturing an electron, one type forms a metastable dipole, while the other collapses to a dimer. A statistical distribution of O vacancies is obtained, and the implications for charge transport and trapping in SiO2 are discussed.

Journal Article↗
PubMed2003

Noise activated granular dynamics.

We study the behavior of two particles moving in a bistable potential, colliding inelastically with each other and driven by a stochastic heat bath. The system has the tendency to clusterize, placing the particles in the same well at low drivings, and to fill all of the available space at high temperatures. We show that the hopping over the potential barrier occurs following the Arrhenius rate, where the heat bath temperature is replaced by the granular temperature. Moreover, within the clusterized "phase" one encounters two different scenarios: For moderate inelasticity, the jumps from one well to the other involve one particle at a time, whereas for strong inelasticity the two particles hop simultaneously.

Journal Article↗
PubMed2003

Wave initiation through spatiotemporally controllable perturbations.

We study the initiation of pulses and fronts in a two-dimensional catalytic reaction-diffusion system: CO oxidation on Pt(110). Using a computer-controlled mobile focused laser beam, we impart various patterns (in space and time) of localized temperature "kicks" to the surface. We explore, and also rationalize through modeling, the cooperativity of such individually subcritical perturbations in both the excitable and the bistable regime.

Journal Article↗
PubMed2003

Simple chemomechanical process for self-generation of rhythms and forms.

We show that cross-coupling between the geometrical changes and the chemical reaction-diffusion regimes within a piece of gel embedded in a stationary reactive medium kept far from equilibrium can destabilize the trivial steady state and lead to spatiotemporal dissipative structures. The involved physical processes are the spatial bistability and the swelling properties of the gel. As an illustration of this morphogenetic process, we show that a sphere of gel immersed within such a medium with autocatalytic properties can exhibit periodic radius pulsations, the amplitude of which are controlled by chemistry.

Biomimetic Materials↗
PubMed2003

Z1/Z2 defects in 4H-SiC.

First-principles calculations are carried out on models for the Z(1)/Z(2) defects in 4H-SiC which are found in as-grown and irradiated n-type material. We show that an interstitial-nitrogen-interstitial-carbon defect is exceptionally thermally stable, bistable, and has negative-U character with donor and acceptor levels close to those attributed to the defect.

Journal Article↗
PubMed2003

Unstable trigger waves induce various intricate dynamic regimes in a reaction-diffusion system of blood clotting.

In this work we demonstrate that the unstable trigger waves, connecting stable and unstable spatially uniform steady states, can create intricate dynamic regimes in one-dimensional three-component reaction-diffusion model describing blood clotting. Among the most interesting regimes are the composite and replicating waves running at a constant velocity. The front part of the running composite wave remains constant, while its rear part oscillates in a complex manner. The rear part of the running replicating wave periodically gives rise to new daughter waves, which propagate in the direction opposite the parent wave. The domain of these intricate regimes in parameter space lies in the region of monostability near the region of bistability.

Blood Coagulation↗
PubMed2003

Optical multistability in three-level atoms inside an optical ring cavity.

Optical multistability in an optical ring cavity filled with a collection of three-level Lambda-type rubidium atoms has been experimentally demonstrated. The observed multistability is very sensitive to the induced atomic coherence in the system and can evolve from a normal bistable behavior with the change of the coupling field as well as the atomic number density. The underlying mechanism for the formation of such multistability is also discussed.

Journal Article↗
PubMed2003

Collective atomic motion in an optical lattice formed inside a high finesse cavity.

We report on collective nonlinear dynamics in an optical lattice formed inside a high finesse ring cavity in a so far unexplored regime, where the light shift per photon times the number of trapped atoms exceeds the cavity resonance linewidth. We observe bistability and self-induced squeezing oscillations resulting from the retroaction of the atoms upon the optical potential wells. We can well understand most of our observations within a simplified model assuming adiabaticity of the atomic motion. Nonadiabatic aspects of the atomic motion are reproduced by solving the complete system of coupled nonlinear equations of motion.

Journal Article↗
PubMed2003

The smallest molecular switch.

Ab initio total energy calculations reveal benzene-dithiolate molecules on a gold surface, contacted by a monatomic gold STM tip to have two classes of low-energy conformations with differing symmetries. Lateral motion of the tip or excitation of the molecule cause it to change from one conformation class to the other and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity, these Au/BDT/Au nanowires are shown to be electrically bistable switches, the smallest two-terminal molecular switches to date.

Journal Article↗
PubMed2003

Two-state theory of nonlinear stochastic resonance.

An amenable, analytical two-state description of the nonlinear population dynamics of a noisy bistable system driven by a rectangular subthreshold signal is put forward. Explicit expressions for the driven population dynamics, the correlation function (its coherent and incoherent parts), the signal-to-noise ratio (SNR), and the stochastic resonance (SR) gain are obtained. Within a suitably chosen range of parameter values this reduced description yields anomalous SR gains exceeding unity and, simultaneously, gives rise to a nonmonotonic behavior of the SNR vs the noise strength. The analytical results agree well with those obtained from numerical solutions of the Langevin equation.

Nonlinear Dynamics↗
PubMed2003

Experimental evidence of "vibrational resonance" in an optical system.

The experimental evidence and characterization of "vibrational resonance" in a bistable vertical cavity laser are reported. The system is driven by two periodic forcings, with frequencies differing by several orders and studied in the case of both symmetrical and asymmetrical quasipotentials. The phenomenon shows up in the dynamics of the polarized laser emission as a resonance in the low-frequency response and signal-to-noise ratio, depending on the amplitude of an applied high-frequency modulation. The possibility to use the phenomenon for low-level detection is experimentally demonstrated.

Models, Theoretical↗