Vibrational Resonance Effect Research Articles

Amplifying a Zeptonewton Force with a Single-Ion Nonlinear Oscillator.

Nonlinear mechanical resonators display rich and complex dynamics and are important in many areas of fundamental and applied sciences. Here, we present a general strategy to generate mechanical nonlinearities for trapped particles by transverse driving in a funnel-shaped potential. Employing a trapped ion platform, we study the nonlinear oscillation, bifurcation, and hysteresis of a single calcium ion and demonstrate a 20-fold enhancement of the signal from a zeptonewton-magnitude harmonic force through the effect of vibrational resonance. Our results represent a first step in combining the rich nonlinear dynamics with the precision control over mechanical motions offered by atomic physics and open up possibilities for exploiting nonlinear mechanical phenomena in the quantum regime.

Vibrational resonance in a neuron-astrocyte coupled model.

Recent findings have revealed that not only neurons but also astrocytes, a special type of glial cells, are major players of neuronal information processing. It is now widely accepted that they contribute to the regulation of their microenvironment by cross-talking with neurons via gliotransmitters. In this context, we here study the phenomenon of vibrational resonance in neurons by considering their interaction with astrocytes. Our analysis of a neuron-astrocyte pair reveals that intracellular dynamics of astrocytes can induce a double vibrational resonance effect in the weak signal detection performance of a neuron, exhibiting two distinct wells centred at different high-frequency driving amplitudes. We also identify the underlying mechanism of this behaviour, showing that the interaction of widely separated time scales of neurons, astrocytes and driving signals is the key factor for the emergence and control of double vibrational resonance. This article is part of the theme issue 'Vibrational and stochastic resonance in driven nonlinear systems (part 2)'.

Influence of Non-fundamental Modes on Mid-infrared Spectra: Anharmonic DFT Study of Aliphatic Ethers.

Fundamental and non-fundamental vibrational modes, first overtones, and binary combination modes of selected aliphatic ethers (di-n-propylether, di-iso-propylether, n-butylmethyl ether, n-butylethyl ether, di-n-butyl ether, tert-buytlmethyl ether, and tert-amylmethyl ether) were modeled in a fully anharmonic generalized second-order vibrational perturbation theory (GVPT2) approach on the DFT-B2PLYP/SNST level. The modeling procedure of theoretical line shapes took into account conformational isomers of studied molecules. The calculated spectra of the above ethers were compared to the corresponding experimental spectra in the infrared (IR) region (4000-560 cm-1) of the absorption index k(ν) derived from the neat liquid thin-film transmission data. It was found that IR spectra of aliphatic ethers are heavily influenced by the bands originating from non-fundamental modes, particularly from the combination modes in the C-H stretching region (3200-2800 cm-1). Because of the effects of vibrational resonances, the intensities of overtones and combination bands originating from methyl and methylene deformation modes increase sufficiently to influence the experimental line shape in this region. Less significant contributions from non-fundamental vibrational modes were noticed in the lower IR region (1600-560 cm-1), particularly in the vicinity of the C-O stretching band. The 2700-1600 cm-1 region, which is rich in weak bands due to non-fundamental vibrations, was reproduced accurately as well. It was concluded that a fully anharmonic approach allows significantly more accurate reproduction of the complex IR line shapes, particularly in the C-H stretching region of aliphatic ethers. On the basis of the achieved agreement between the experimental and calculated spectra, it may be concluded that the anharmonic GVPT2 method can adequately reproduce the anharmonic effects and vibrational resonances in particular, influencing the IR spectra of aliphatic ethers. The results obtained in this study show that the non-fundamental modes may play a significant role in shaping the IR spectra of aliphatic ethers and similar molecules in the neat liquid phase.

Nuclear-Spin-Induced Circular Dichroism in the Infrared Region for Liquids.

Recently, the nuclear-spin-induced optical rotation (NSOR) and circular dichroism (NSCD) for liquids were discovered and extensively studied and developed. However, so far, nuclear-spin-induced magnetic circular dichroism in the IR region (IR-NSCD) has not been explored, even though all polyatomic molecules exhibit extensive IR spectra. Herein, IR-NSCD is proposed and discussed theoretically. The results indicate that in favorable conditions the IR-NSCD angle may be much larger than the NSOR angle in the UV/Vis region due to a vibrational resonance effect and can be measurable by using the NSOR experiment scheme. IR-NSCD can automatically combine and give NMR spectra and IRCD spectra of the nuclear spin prepolarized samples in liquids, which, in principle, could be developed to become a unique, novel analytical tool.

Enhanced multiple vibrational resonances by Na+ and K+ dynamics in a neuron model.

Some neuronal receptors perceive external input in the form of hybrid periodic signals. The signal detection may be based on the mechanism of vibrational resonance, in which a system's response to the low frequency signal can become optimal by an appropriate choice of the vibration amplitude of HFS. The vibrational resonance effect is investigated in a neuron model in which the intra- and extra-cellular potassium and sodium concentrations are allowed to evolve temporally, depending on ion currents, Na+-K+ pumps, glial buffering, and ion diffusion. Our results reveal that, compared to the vibrational resonances in the model with constant ion concentrations, the significantly enhanced vibrational multi-resonances can be observed for the single neuron system where the potassium and sodium ion concentrations vary temporally. Thus, in contradiction to a popular view that ion concentrations dynamics play little role in signal detection, we indicate that the neuron's response to an external subthreshold signal can be largely improved by sodium and potassium dynamics.

Experimental and numerical study of noise effects in a FitzHugh–Nagumo system driven by a biharmonic signal

Using a nonlinear circuit ruled by the FitzHugh–Nagumo equations, we experimentally investigate the combined effect of noise and a biharmonic driving of respective high and low frequency F and f. Without noise, we show that the response of the circuit to the low frequency can be maximized for a critical amplitude B∗ of the high frequency via the effect of Vibrational Resonance (V.R.). We report that under certain conditions on the biharmonic stimulus, white noise can induce V.R. The effects of colored noise on V.R. are also discussed by considering an Ornstein–Uhlenbeck process. All experimental results are confirmed by numerical analysis of the system response.

Effects of hybrid synapses on the vibrational resonance in small-world neuronal networks

We investigate the effect of vibrational resonance in small-world neuronal networks with hybrid chemical and electrical synapses. It is shown that, irrespective of the probability of chemical synapses, an optimal amplitude of high-frequency component of the signal can optimize the dynamical response of neuron populations to the low-frequency component, which encodes the information. This effect of vibrational resonance of neuronal systems depends extensively on the network structure and parameters, which determine the ability of neuronal networks to enhance the outreach of localized subthreshold low-frequency signal. In particular, chemical synaptic coupling is more efficient than the electrical coupling for the transmission of local input signal due to its selective coupling. Moreover, there exists an optimal small-world topology characterized by an optimal value of rewiring probability, warranting the largest peak value of the system response. Considering that two-frequency signals are ubiquity in brain dynamics, we expect the presented results could have important implications for signal processing in neuronal systems.

Experimental and numerical enhancement of vibrational resonance in neural circuit

A neural circuit exactly ruled by the FitzHugh-Nagumo equations is excited by a biharmonic signal of frequencies f and F with respective amplitudes A and B. The magnitude spectrum of the circuit response is estimated at the low frequency driving f and presents a resonant behaviour against the amplitude B of the high frequency. For the first time, it is shown experimentally that this vibrational resonance effect is much more pronounced when the two frequencies are multiple. This novel enhancement is also confirmed by numerical predictions. Applications of this nonlinear effect to the detection of weak stimuli are finally discussed.

Vibrational resonance in excitable neuronal systems

In this paper, we investigate the effect of a high-frequency driving on the dynamical response of excitable neuronal systems to a subthreshold low-frequency signal by numerical simulation. We demonstrate the occurrence of vibrational resonance in spatially extended neuronal networks. Different network topologies from single small-world networks to modular networks of small-world subnetworks are considered. It is shown that an optimal amplitude of high-frequency driving enhances the response of neuron populations to a low-frequency signal. This effect of vibrational resonance of neuronal systems depends extensively on the network structure and parameters, such as the coupling strength between neurons, network size, and rewiring probability of single small-world networks, as well as the number of links between different subnetworks and the number of subnetworks in the modular networks. All these parameters play a key role in determining the ability of the network to enhance the outreach of the localized subthreshold low-frequency signal. Considering that two-frequency signals are ubiquity in brain dynamics, we expect the presented results could have important implications for the weak signal detection and information propagation across neuronal systems.

Vibrational resonance in a noise-induced structure.

We report on the effect of vibrational resonance in a spatially extended system of coupled noisy oscillators under the action of two periodic forces, a low-frequency one (signal) and a high-frequency one (carrier). Vibrational resonance manifests itself in the fact that for optimally selected values of high-frequency force amplitude, the response of the system to a low-frequency signal is optimal. This phenomenon is a synthesis of two effects, a noise-induced phase transition leading to bistability, and a conventional vibrational resonance, resulting in the optimization of signal processing. Numerical simulations, which demonstrate this effect for an extended system, can be understood by means of a zero-dimensional "effective" model. The behavior of this "effective" model is also confirmed by an experimental realization of an electronic circuit.

The effects of vibrational resonances on Renner–Teller coupling in triatomic molecules: The stretch–bender approach

A vibration–rotation Hamiltonian for a symmetric triatomic molecule, based upon a stretch–bender reference frame has been derived. This frame is chosen so that as the molecule bends the reference geometry follows the minimum in the potential energy surface, thus minimizing the size of the displacements required to reach the instantaneous axis geometry. This may be regarded as an extension of methods based upon the rigid–bender reference frame approach developed by Hougen, Bunker, and Johns [J. Mol. Spectrosc. 34, 136 (1970)]. This new stretch–bender Hamiltonian is combined with the Barrow, Dixon, and Duxbury [Mol. Phys. 27, 1217 (1974)] and the Jungen and Merer [Mol. Phys. 40, 25 (1980)] methods of solving the Renner–Teller coupling problem in which molecules execute large amplitude nuclear motion, producing a compact method for the variational calculation of the energies of such a system. The ã 1A1 and b̃ 1B1 states of the methylene radical, CH2, are used to demonstrate the use of this method for the analysis of the behavior of strongly coupled electronic and vibrational states.

Renner-Teller correlation diagrams for orbital angular momentum in ∏ and △ states of triatomic molecules

A method is described for relating the energy level correlation diagrams introduced by Renner to the angular momentum 'sawtooth' correlation diagrams constructed by Jungen and Merer. In order to do this new spin-orbit coupling versions of the diagrams are introduced for the strictly linear and bent-linear behaviour, and a version of the linear 'sawtooth' diagram is constructed. Finally the effects of vibrational resonances are introduced to modify the interference effects seen in the 'sawtooth' diagrams. The diagrams are constructed using an extension of the calculation method first introduced by Barrow, Dixon and Duxbury to allow to be obtained.

Microwave Spectra in the ν4 Vibrational State of Methyl Cyanide and Methyl Isocyanide and Their 15N Derivatives

Four pure rotational transitions have been observed between 99 and 183 GHz for the ν4 vibrational state of CH3CN, CH3NC, and their 15N derivatives. The rotation and centrifugal distortion constants are given for the four molecules. A vibrational resonance effect is detected on the [Formula: see text] lines of CH3NC.