Properties Of Oscillations Research Articles

Spin polarization transport through a four InAs quantum dots system irradiated by terahertz light field

We design a four InAs quantum dot system in which two leads are irradiated by terahertz light fields. The average current through the system is obtained by means of non-equilibrium Green's function theory. Typical photon-assisted tunneling is observed in the current energy spectrum. 100% polarization can be achieved by adjusting the intensity of Zeeman magnetic field or the amplitude of terahertz light field. As the frequency of terahertz light field is invariant, a zero current can be obtained by adjusting the amplitude of the terahertz light field, indicating an optically controlled quantum switch device. The spin polarization can be converted between 0 and 1 by tuning the energy level of quantum dots, suggesting a physical scheme of a polarization pulse device. Moreover, the system can be constructed as a terahertz detector due to the oscillation properties of spin polarization. The present work sheds lights onto the design of quantum computing and spin-dependent quantum devices.

Effects of Damping Constant of Electron and Size on Quantum-Based Frequency-dependent Dielectric Function of Small Metallic Plasmonic Devices

Electron surface dissipation and quantum-limited size tend to control the material properties of exterior plasmon oscillation as the size of metal nanoparticles goes into the nanoscale domain. The need to examine this characteristic behaviour and its potential becomes imperative. This study explores the effects of the damping constant of electrons and size quantum-based frequency-dependent dielectric function (FDDF) of small metallic materials using an elementary model of electrons in a confined box. The frequency-dependent dielectric function is employed to study quantum size impacts and damping constant in the optical spectra region. The quantum amended frequency-dependent dielectric function and the absorbing spectra of silver-cube geometry for different sizes by adding damping constant and without damping constant are critically examined. The findings reveal that when the damping constant effect is absent, the multiple crests emerge for the quantum-amended frequency-dependent dielectric function and absorbing spectra of the metallic materials, highlighting the electronic discretization levels in the tiny quantum-limited structure. While the damping constant is included, the multiple summits are hidden and vanish owing to a considerable widening of the structures independently. The change in the numerical results from the quantum case to the classical case for growing widths is further illustrated for both cases. The numerical results enhance our knowledge of damping constant dissipation and quantum limited-size impact in small-scaled plasmonic devices.

Variability and phase lags of the type-C quasi-periodic oscillation of MAXI J1348–630 with NICER

ABSTRACT We study the properties of the type-C quasi-periodic oscillation (type-C QPO) of MAXI J1348–630 during its 2019 outburst and reflare with NICER. This is the first time that the evolution of the properties of type-C QPOs is studied during an outburst reflare. We found that the properties of the type-C QPO during the reflare are similar to those of type-C QPOs observed in other black hole systems during outburst. This suggests that the physical processes responsible for type-C QPOs are the same in a reflare and in an outburst. We also found that the full width at half-maximum of a high-frequency broad-band component observed during the reflare changes significantly with energy. We studied the energy-dependent fractional rms amplitude and phase lags of the type-C QPO from 0.5 to 12 keV. We found that the fractional rms amplitude increases up to 2–3 keV and then remains approximately constant above this energy, and the lag spectra of the type-C QPO are hard. We discuss the dependence of the fractional rms amplitude and phase lags with energy in the context of Comptonization as the radiative mechanism driving the QPO rms and lag spectra.

Characterization of Liquid Oscillation and Sloshing Properties of Toroidal TLCDs for Multidirectional Vibration Control

The toroidal tuned liquid column damper (TTLCD) has been known so far only for its multidirectional vibration control capabilities. The details of its liquid motion characteristics and energy dissipation capacity have been missing. To cover this gap, in this paper, experimental studies are carried out by shaking table tests and an effective three-dimensional computational fluid dynamics model of the TTLCD is developed. All parametric effects and the characteristics of the liquid motion in the TTLCD are addressed. The findings of the paper now clearly reveal that the TTLCD encompasses both an oscillatory liquid deflection as the first mode and a sloshing motion as the second mode vibration response. Accordingly, the results prove that the TTLCD operates not only multidirectionally but also as a unique multimodal device, which unites the properties of tuned liquid dampers (TLDs)/tuned sloshing dampers (TSDs) with tuned liquid column dampers (TLCDs).

Astrocytes Sustain Circadian Oscillation and Bidirectionally Determine Circadian Period, But Do Not Regulate Circadian Phase in the Suprachiasmatic Nucleus.

The suprachiasmatic nucleus (SCN) is the master circadian clock of mammals, generating and transmitting an internal representation of environmental time that is produced by the cell-autonomous transcriptional/post-translational feedback loops (TTFLs) of the 10,000 neurons and 3500 glial cells. Recently, we showed that TTFL function in SCN astrocytes alone is sufficient to drive circadian timekeeping and behavior, raising questions about the respective contributions of astrocytes and neurons within the SCN circuit. We compared their relative roles in circadian timekeeping in mouse SCN explants, of either sex. Treatment with the glial-specific toxin fluorocitrate revealed a requirement for metabolically competent astrocytes for circuit-level timekeeping. Recombinase-mediated genetically complemented Cryptochrome (Cry) proteins in Cry1-deficient and/or Cry2-deficient SCNs were used to compare the influence of the TTFLs of neurons or astrocytes in the initiation of de novo oscillation or in pacemaking. While neurons and astrocytes both initiated de novo oscillation and lengthened the period equally, their kinetics were different, with astrocytes taking twice as long. Furthermore, astrocytes could shorten the period, but not as potently as neurons. Chemogenetic manipulation of Gi- and Gq-coupled signaling pathways in neurons acutely advanced or delayed the ensemble phase, respectively. In contrast, comparable manipulations in astrocytes were without effect. Thus, astrocytes can initiate SCN rhythms and bidirectionally control the SCN period, albeit with lower potency than neurons. Nevertheless, their activation does not influence the SCN phase. The emergent SCN properties of high-amplitude oscillation, initiation of rhythmicity, pacemaking, and phase are differentially regulated: astrocytes and neurons sustain the ongoing oscillation, but its phase is determined by neurons.SIGNIFICANCE STATEMENT The hypothalamic suprachiasmatic nucleus (SCN) encodes and disseminates time-of-day information to allow mammals to adapt their physiology to daily environmental cycles. Recent investigations have revealed a role for astrocytes, in addition to neurons, in the regulation of this rhythm. Using pharmacology, genetic complementation, and chemogenetics, we compared the abilities of neurons and astrocytes in determining the emergent SCN properties of high-amplitude oscillation, initiation of rhythmicity, pacemaking, and determination of phase. These findings parameterize the circadian properties of the astrocyte population in the SCN and reveal the types of circadian information that astrocytes and neurons can contribute within their heterogeneous cellular network.

Nonlinear oscillator design based on phase reduction method for closed‐loop system

SummaryTo widely utilize the synchronization properties of nonlinear oscillators in the control and signal processing engineering field, a common design method for a nonlinear oscillator model would be helpful. The output response of a nonlinear oscillator excited by a periodic signal implicitly includes the information of both the instantaneous phase and the amplitude of the input signal. Explicitly expressing the dynamics of both phase and amplitude with the phase reduction method, and organizing them by the number of events in one period, could enable the design of a nonlinear oscillator model in the same manner that can synchronize with an arbitrary cyclic phenomenon in a broad sense. Assuming the cyclic phenomenon is a single periodic signal, the property of the generalized nonlinear oscillator model has the role as a common‐dimensional observer to attain the pseudo‐property of both iso‐damping and flat‐gain. Thus, this article determines the essential role of the nonlinear oscillator inserted in the closed‐loop system through investigating the input–output characteristic of the generalized nonlinear oscillator model. As a result of the numerical simulation using a simple vibration excitation and suppression system, it was found that using the generalized nonlinear oscillator model enables us to easily build the closed‐loop system including the pseudo‐property of both iso‐damping and flat‐gain.

Effects of Intense Laser Field on Electronic and Optical Properties of Harmonic and Variable Degree Anharmonic Oscillators

In this paper, we calculated the electronic and optical properties of the harmonic oscillator and single and double anharmonic oscillators, including higher-order anharmonic terms such as the quartic and sextic under the non-resonant intense laser field. Calculations are made within the effective mass and parabolic band approximations. We have used the diagonalization method by choosing a wave function based on the trigonometric orthonormal functions to find eigenvalues and eigenfunctions of the electron confined within the harmonic and anharmonic oscillator potentials under the non-resonant intense laser field. A two-level approach in the density matrix expansion is used to calculate the linear and third-order nonlinear optical absorption coefficients. Our results show that the electronic and optical properties of the structures we focus on can be adjusted to obtain a suitable response to specific studies or aims by changing the structural parameters such as width, depth, coupling between the wells, and applied field intensity.

Association between resting-state EEG oscillation and psychometric properties in perimenopausal women

BackgroundThe perimenopausal period is associated with a higher risk of various mood disorders. Similarly, although resting-state electroencephalogram (rsEEG) brain oscillatory activity has been associated with various neuropsychological disorders and behaviours, these issues have not been assessed in perimenopausal women. This study aimed to evaluate quantitative relationships between psychometric properties and rsEEG rhythms (delta, theta, alpha, beta and gamma powers) in perimenopausal women.MethodsA cross-sectional correlational descriptive study was conducted to quantitatively analyze the correlations between rsEEG low-to-high band activities (delta, theta, alpha, beta, and gamma powers) and psychometric properties in 14 perimenopausal women. Participants completed a psychological inventory comprising the State Anxiety Inventory (SAI), Depression Inventory (DI), Behavioural Inhibition Scale (BIS) and short-form UPPS Impulsive Behaviour Scale (IS) before EEG recording.ResultsResults showed that impulsivity was positively related to the beta power, symmetrical at most channels (frontal, temporal, central, parietal and occipital regions; p < .05); but did not related to the delta, theta, alpha and gamma powers. The brainwave low-to-high bands, delta, theta, alpha, beta and gamma power were not associated with DI, SAI or BIS scores.ConclusionsThis study’s findings propose that significantly enhanced resting-state beta activity is a trait of impulsivity in perimenopausal women. Therefore, results have potential implications for the preclinical or clinical evaluation of these issues in perimenopausal women.

Quantum dynamics of a harmonic oscillator in a non-equilibrium bath without the rotating wave approximation

The aim of this paper is to investigate dynamical properties of a harmonic oscillator coupled to a non-equilibrium bath without the rotating wave approximation. At first, we investigate the theory of this model and obtain the Heisenberg equations of motion for the oscillator and bath annihilation operators in the absence and in the presence of a rotating wave approximation. Then, we obtain the fluctuation and fluctuation-dissipation relations in the absence and in the presence of a rotating wave approximation for the non-equilibrium bath annihilation operator, respectively. After that, we study the decay of system modes using the Wigner-Weisskopf approximation. Finally, we calculate the time-dependent spectrum of a cavity field mode coupled to a non-equilibrium reservoir. We show that even under the condition in which the RWA is considered to be valid (weak interaction), there are significant effects of virtual-photon field on the diffusion coefficient, the energy density, line width and the shift frequency.

Slow Magnetoacoustic Oscillations in Stellar Coronal Loops

Slow magnetoacoustic oscillations in stellar coronal loops with gravitational stratification are analyzed with a numerical solution of the boundary value problem for eigenvalues and eigenfunctions. In this study, we only focus on the resonant periods. The effects of the gravitational stratification, star mass, loop temperature, and loop length on the properties of slow magnetoacoustic oscillations are investigated. It is shown that the discrepancy between stratified and nonstratified loops is higher in density perturbations than in velocity perturbations. When the star has a larger mass, higher coronal temperature, and longer loop, the density perturbations in the stratified loop are significantly different from the harmonic functions. The periods in the stratified loop are slightly longer than in the nonstratified loop. The periods calculated in our model (14–644 minutes) are consistent with the periods of stellar quasi-periodic pulsations observed in both soft X-rays (2–70 minutes) and white lights (8–390 minutes).

High-frequency Waves in Chromospheric Spicules

Using high-cadence observations from the Hydrogen-alpha Rapid Dynamics camera imaging system on the Dunn Solar Telescope, we present an investigation of the statistical properties of transverse oscillations in spicules captured above the solar limb. At five equally separated atmospheric heights, spanning approximately 4900–7500 km, we have detected a total of 15,959 individual wave events, with a mean displacement amplitude of 151 ± 124 km, a mean period of 54 ± 45 s, and a mean projected velocity amplitude of 21 ± 13 km s−1. We find that both the displacement and velocity amplitudes increase with height above the solar limb, ranging from 132 ± 111 km and 17.7 ± 10.6 km s−1 at ≈4900 km, and 168 ± 125 km and 26.3 ± 14.1 km s−1 at ≈7500 km, respectively. Following the examination of neighboring oscillations in time and space, we find 45% of the waves to be upwardly propagating, 49% to be downwardly propagating, and 6% to be standing, with mean absolute phase velocities for the propagating waves on the order of 75–150 km s−1. While the energy flux of the waves propagating downwards does not appear to depend on height, we find the energy flux of the upwardly propagating waves decreases with atmospheric height at a rate of −13,200 ± 6500 W m−2/Mm. As a result, this decrease in energy flux as the waves propagate upwards may provide significant thermal input into the local plasma.

FORCED NONLINEAR OSCILLATOR IN A FRACTAL SPACE

A critical hurdle of a nonlinear vibration system in a fractal space is the inefficiency in modelling the system. Specifically, the differential equation models cannot elucidate the effect of porosity size and distribution of the periodic property. This paper establishes a fractal-differential model for this purpose, and a fractal Duffing-Van der Pol oscillator (DVdP) with two-scale fractal derivatives and a forced term is considered as an example to reveal the basic properties of the fractal oscillator. Utilizing the two-scale transforms and He-Laplace method, an analytic approximate solution may be attained. Unfortunately, this solution is not physically preferred. It has to be modified along with the nonlinear frequency analysis, and the stability criterion for the equation under consideration is obtained. On the other hand, the linearized stability theory is employed in the autonomous arrangement. Consequently, the phase portraits around the equilibrium points are sketched. For the non-autonomous organization, the stability criteria are analyzed via the multiple time scales technique. Numerical estimations are designed to confirm graphically the analytical approximate solutions as well as the stability configuration. It is revealed that the exciting external force parameter plays a destabilizing role. Furthermore, both of the frequency of the excited force and the stiffness parameter, execute a dual role in the stability picture.

ν-e Scattering radiative corrections in a short baseline experiment

Precision tests in future long-baseline experiments will measure neutrino oscillation properties with high accuracy. Besides, with their near detectors will be possible to perform measurements with high statistics, such as neutrino scattering with electrons, among other neutrino interactions. Near detectors will give the chance to measure the radiative corrections of this process with unprecedented precision. This work will discuss how the test of the radiative corrections in the neutrino-electron scattering may measure the neutrino charge radius.

Transition of the breather wave of six-order nonlinear Schrödinger equation

In this work, we study the dynamic properties of the transformed nonlinear waves of the six-order nonlinear Schrödinger equation. The breather wave of the equation is obtained based on the Darboux transformation. In order to study the state transition, we give the transition conditions of the breather wave. Based on this transition condition, the breather wave is transformed into various types of nonlinear waves, including W-shaped solitons, M-shaped solitons, multi-peak solitons, oscillation solitons, etc. Furthermore, the oscillation properties of these transformed nonlinear waves are analyzed. Finally, these transformed nonlinear waves are graphically presented.

Useful zero friction simulations for assessing MBS codes Pascal's formula giving wheelsets frequency for zero wheel-rail friction

Present study provides a simple analytical formula, the “Klingel-like formula” or “Pascal's Formula” that can be used as a reference to test some results of existing railway codes and specifically those using rigid contact. It develops properly the 3D Newton-Euler equations governing the 6 degrees of freedom (DoF) of unsuspended loaded wheelsets in case of zero wheel-rail friction and constant conicity. Thus, by solving numerically these equations, we got pendulum like harmonic oscillations of which the calculated angular frequency is used for assessing the accuracy of the proposed formula so that it can in turn be used as a fast practical target for testing multi-body system (MBS) railway codes. Due to the harmonic property of these pendulum-like oscillations, the square ω2 of their angular frequency can be made in the form of a ratio K/M where K depends on the wheelset geometry and load and M on its inertia. Information on K and M are useful to understand wheelsets behavior. The analytical formula is derived from the first order writing of full trigonometric Newton-Euler equations by setting zero elastic wheel-rail penetration and by assuming small displacements. Full trigonometric equations are numerically solved to assess that the formula provides ω2 inside a 1% accuracy for usual wheelsets dimensions. By decreasing the conicity down to 1 × 10−4 rad, the relative formula accuracy is under 3 × 10−5. In order to test the formula reliability for rigid contact formulations, the stiffness of elastic contacts can be increased up to practical rigidity (Hertz stiffness × 1000).

Oscillation and Sensor Properties of Integrated Opto-Chemical Sensors in Different Solvents

Oscillation and Sensor Properties of Integrated Opto-Chemical Sensors in Different Solvents

Dynamical evolution of the shock cone around 4D Einstein-Gauss Bonnet rotating black hole

In this paper, a Bondi-Hoyle accretion onto the rotating black hole in Einstein-Gauss Bonnet gravity is studied. By injecting the gas from the upstream region of the computational domain, we have found the occurrence of the stable shock cones in the downstream region. The dynamical structures and oscillation properties of these shock cones strongly depend on the black hole spin parameter a and Gauss-Bonnet coupling constant α. It is found that the various values of α can lead the different amounts of matter to pile up close to the black hole horizon, higher α causes bigger oscillation amplitude in the mass accretion rate, and the required time to reach the steady state is getting smaller with the increase in α. Moreover, increasing α in the negative direction causes a decrease in the shock opening angle and this angle slightly increases with the increasing α in the positive direction. We found that the negative values of Gauss-Bonnet coupling constant are more favored to have interesting physical outcomes such as accretion rate and oscillation. In addition, the higher the black hole rotation parameter a emerges the higher the accretion rate. It is also confirmed that, for α→0, the black hole solution in EGB gravity converges to Kerr in general relativity. Furthermore, Gauss-Bonnet coupling constant could be used to constrain the size of the observed shadow of M87⁎ radius for various values of the black hole rotation parameter.

Oscillatory Behaviour of the Nonlinear Damped Fractional Partial Dynamic Equation

In this paper, a partial dynamic equation of fractional order is considered with Neumann and Dirichlet boundary conditions, and we studied the oscillation properties of the fractional partial dynamic equation on time scales. Riccati transformation technique is used to establish oscillation criteria for the fractional partial dynamic equation. The obtained results are verified with examples.

Improving Functional Connectivity in Developmental Dyslexia through Combined Neurofeedback and Visual Training

This study examined the effects of combined neurofeedback (NF) and visual training (VT) on children with developmental dyslexia (DD). Although NF is the first noninvasive approach to support neurological disorders, the mechanisms of its effects on the brain functional connectivity are still unclear. A key question is whether the functional connectivities of the EEG frequency networks change after the combined NF–VT training of DD children (postD). NF sessions of voluntary α/θ rhythm control were applied in a low-spatial-frequency (LSF) illusion contrast discrimination, which provides feedback with visual cues to improve the brain signals and cognitive abilities in DD children. The measures of connectivity, which are defined by small-world propensity, were sensitive to the properties of the brain electrical oscillations in the quantitative EEG-NF training. In the high-contrast LSF illusion, the z-NF reduced the α/θ scores in the frontal areas, and in the right ventral temporal, occipital–temporal, and middle occipital areas in the postD (vs. the preD) because of their suppression in the local hub θ-network and the altered global characteristics of the functional θ-frequency network. In the low-contrast condition, the z-NF stimulated increases in the α/θ scores, which induced hubs in the left-side α-frequency network of the postD, and changes in the global characteristics of the functional α-frequency network. Because of the anterior, superior, and middle temporal deficits affecting the ventral and occipital–temporal pathways, the z-NF–VT compensated for the more ventral brain regions, mainly in the left hemispheres of the postD group in the low-contrast LSF illusion. Compared to pretraining, the NF–VT increased the segregation of the α, β (low-contrast), and θ networks (high-contrast), as well as the γ2-network integration (both contrasts) after the termination of the training of the children with developmental dyslexia. The remediation compensated more for the dorsal (prefrontal, premotor, occipital–parietal connectivities) dysfunction of the θ network in the developmental dyslexia in the high-contrast LSF illusion. Our findings provide neurobehavioral evidence for the exquisite brain functional plasticity and direct effect of NF–VT on cognitive disabilities in DD children.

Transverse kink oscillations of inhomogeneous prominence threads: Numerical analysis and Hα forward modelling

Context. Prominence threads are very long and thin flux tubes that are partially filled with cold plasma. Observations have shown that transverse oscillations are frequent in these solar structures. The observations are usually interpreted as the fundamental kink mode, while the detection of the first harmonic remains elusive. Aims. The properties of oscillations in threads are greatly affected by the density distribution along the flux tube. Here, we aim to study how the density inhomogeneities in the longitudinal and radial directions modify the periods and damping times of kink oscillations and how this effect would be reflected in the observations. Methods. We solved the ideal magnetohydrodynamics equations using two different methods: (a) performing 3D numerical simulations and (b) solving a 2D generalised eigenvalue problem. We studied the dependence of the periods, damping times, and amplitudes of transverse kink oscillations on the ratio between the densities at the centre and at the ends of the tube, and also on the average density. We applied forward modelling to our 3D simulations to compute synthetic Hα profiles. Results. We confirm that the ratio of the period of the fundamental oscillation mode to the period of the first harmonic increases as the ratio of the central density to the footpoint density is increased, or as the averaged density of the tube is decreased. We find that the damping times due to resonant absorption decrease as the central-to-footpoint density ratio increases. Contrary to the case of longitudinally homogeneous tubes, we find that the damping-time-to-period ratio also increases as the density ratio is increased or the average density is reduced. We present snapshots and time-distance diagrams of the emission in the Hα line. Conclusions. The results presented here have implications for the field of prominence seismology. While the Hα emission can be used to detect the fundamental mode, the first harmonic is barely detectable in Hα. This may explain the lack of detections of the first harmonic. A combination of different spectral lines is required to obtain information about the period ratio and to use it to infer physical properties of the threads.