Beat Response Research Articles

Electric Field Effects in Hybrid Perovskites Studied via Picosecond Kerr Microscopy.

We present time-resolved Kerr rotation (TRKR) spectra in thin films of CH3NH3PbI3 (MAPI) hybrid perovskite using a unique picosecond microscopy technique at 4 K having a spatial resolution of 2 μm and temporal resolution of 1 ps, subjected to both an in-plane applied magnetic field up to 700 mT and an electric field up to 104 V/cm. We demonstrate that the obtained TRKR dynamics and spectra are substantially inhomogeneous across the MAPI films with prominent resonances at the exciton energy and interband transition of this compound. From the obtained quantum beating response as a function of magnetic field in the Voigt configuration, we also extract the inhomogeneity of the electron and hole Lande g-values and spin coherence time, T2*. We also report the TRKR dependence on both the applied magnetic field and electric field. From the change in the quantum beating dynamics, we found that T2* substantially decreases upon the application of an electric field. At the same time, from the induced spatial TRKR changes, we show that the electric field induced effects are caused by ion migration in the MAPI films.

Numerical Analysis of Flow-Induced Transverse Vibration of a Cylinder with Cubic Non-Linear Stiffness at High Reynolds Numbers

Numerical calculations were performed to study the vortex-induced vibration (VIV) of a circular cylinder, which was elastically supported by springs of linear and cubic terms. These simulations were conducted at high Reynolds numbers ranging from 4200 to 42,000. To simulate the cylinder’s motion and the associated aerodynamic forces, Computational Fluid Dynamics were employed in conjunction with dynamic mesh capabilities. The numerical method was initially verified by testing it with various grid resolutions and time steps, and subsequently, it was validated using experimental data. The response of cubic nonlinearities was investigated using insights gained from a conventional linear vortex-induced vibration (VIV) system. This 2D study revealed that both the amplitude and frequency of vibrations are contingent on the flow velocity. The highest output was achieved within the frequency lock-in region, where internal resonance occurs. In the case of a hardening spring, the beating response was observed from the lower end of the initial branch to the upper end of the initial branch. The response displacement amplitude obtained for the linear spring case was 27 mm, whereas in the cubic nonlinear case, the value was 31.8 mm. More importantly, the results indicate that the inclusion of nonlinear springs can substantially extend the range of wind velocities in which significant energy extraction through vortex-induced vibration (VIV) is achievable.

A Simple Three-Degree-of-Freedom Digital Current Controller With Dead Beat Response for AC Machines

Since current controllers are implemented digitally, digital current controllers need to be established for pursuing high performance alternating current (AC) machine drives. Considering to enhance the dynamic response, disturbance rejection and stability both, this paper proposes a simple three-degree-of-freedom (3DOF) digital current controller. In the proposed structure, three needed coefficients have been theoretically designed, which stand for the dynamic response ability, disturbance rejection and rejection of the instability caused by machine parameters mismatch, respectively. In addition, the proposed 3DOF current controller can own dead beat response characteristic with one-step delay compensation. Experimental results validate the effectiveness of the proposed digital current controller in a AC machine drive test rig.

Evaluating process of auto-hydrolysis prior to kraft pulping on production of chemical pulp for end used paper-grade products

The objective of this work is to systematically evaluate the performance of the hydrolysis-based kraft pulping process and associated pulp and black liquor characteristics. Acacia wood chips were auto-hydrolyzed under various severities, then the hydrolyzed wood chips were kraft pulping. The results indicated that the yield of pulp significantly dropped with intensifying the auto-hydrolysis severity. Meanwhile, the removal rate of pentosan reached 98.6% in the screened pulp at the P-factor of 1 000. The fiber length, fines and fiber crimp of the screened pulp were not affected by the auto-hydrolysis treatment. Auto-hydrolyzed pulps deteriorated fibrillation and beating response of the pulp in a refining process. However, fiber length and fines changed obviously after beating treatment. After auto-hydrolysis, the tensile index of the paper matrices decreased, some particle substances were found on the surface of the pulp fiber, and the solid and organic content of the black liquor were improved.

Evaluating process of auto-hydrolysis prior to kraft pulping on production of chemical pulp for end used paper-grade products

The objective of this work is to systematically evaluate the performance of the hydrolysis-based kraft pulping process and associated pulp and black liquor characteristics. Acacia wood chips were auto-hydrolyzed under various severities, then the hydrolyzed wood chips were kraft pulping. The results indicated that the yield of pulp significantly dropped with intensifying the auto-hydrolysis severity. Meanwhile, the removal rate of pentosan reached 98.6% in the screened pulp at the P-factor of 1 000. The fiber length, fines and fiber crimp of the screened pulp were not affected by the auto-hydrolysis treatment. Auto-hydrolyzed pulps deteriorated fibrillation and beating response of the pulp in a refining process. However, fiber length and fines changed obviously after beating treatment. After auto-hydrolysis, the tensile index of the paper matrices decreased, some particle substances were found on the surface of the pulp fiber, and the solid and organic content of the black liquor were improved.

Human Neurons Form Axon-Mediated Functional Connections with Human Cardiomyocytes in Compartmentalized Microfluidic Chip.

The cardiac autonomic nervous system (cANS) regulates cardiac function by innervating cardiac tissue with axons, and cardiomyocytes (CMs) and neurons undergo comaturation during the heart innervation in embryogenesis. As cANS is essential for cardiac function, its dysfunctions might be fatal; therefore, cardiac innervation models for studying embryogenesis, cardiac diseases, and drug screening are needed. However, previously reported neuron-cardiomyocyte (CM) coculture chips lack studies of functional neuron–CM interactions with completely human-based cell models. Here, we present a novel completely human cell-based and electrophysiologically functional cardiac innervation on a chip in which a compartmentalized microfluidic device, a 3D3C chip, was used to coculture human induced pluripotent stem cell (hiPSC)-derived neurons and CMs. The 3D3C chip enabled the coculture of both cell types with their respective culture media in their own compartments while allowing the neuronal axons to traverse between the compartments via microtunnels connecting the compartments. Furthermore, the 3D3C chip allowed the use of diverse analysis methods, including immunocytochemistry, RT-qPCR and video microscopy. This system resembled the in vivo axon-mediated neuron–CM interaction. In this study, the evaluation of the CM beating response during chemical stimulation of neurons showed that hiPSC-neurons and hiPSC-CMs formed electrophysiologically functional axon-mediated interactions.

Sleep Pattern Study with Respect to Binaural Beats Using Sensors and Mobile Application

Sleep disorders are common among people in the present lifestyle and this may occur due to irregular sleep patterns. The disordered sleep pattens arise due to various reasons and can be prevented by ensuring a relaxed and deep sleep for everyone. Binaural beats are the stimuli that are set to a particular rhythm and generated to get the required audio frequency to synchronize with the brainwaves. This paper focuses on the effects and analysis of binaural beat response on the brain waves of adults and how they help to induce sleep for an individual. This work highlights the results that were obtained by performing the real time hardware experiments accordingly. The head movement is recorded from the experiment using the readings from the accelerometer and gyroscope sensors which are depicted by the angle coordinates based on two conditions, first when the subjects fall asleep without application of binaural beats and second when minimal frequency of binaural beats are applied close to their ears. Using the real time hardware experiment values, an application is created to differentiate the cases of with and without binaural beats application. In order to validate the real time experiment with an application, a statistical analysis is done from the obtained real time hardware results depicting the sleep pattern by performing corresponding tests.

Calmodulin and protein kinases A/G mediate ciliary beat response in the human nasal epithelium.

Mucociliary clearance of the airway epithelium is an essential function for mucosal defense. We recently proposed a hypothetical mechanism of ciliary beat regulation, in which the pannexin-1 (Panx1)-P2X7 unit serves as an oscillator generating a periodic increase in intracellular Ca2+ ([Ca2+ ]i ). In the present study, we examined the localization of Panx1 and P2X7 at the ultrastructural level, and investigated the regulatory pathway subsequent to [Ca2+ ]i increase. The inferior turbinate mucosa was collected from patients with chronic hypertrophic rhinitis during endoscopic sinonasal surgery. The mucosa was examined by transmission immunoelectron microscopy for Panx1 and P2X7. Alternatively, the mucosa was cut into thin strips, and ciliary beat frequency (CBF) was measured under a phase-contrast light microscope with a high-speed digital video camera. In immunoelectron microscopy, immunoreactivities for Panx1 and P2X7 were localized along the plasma membrane of the entire length of the cilia. CBF was significantly increased by stimulation with 100 µM acetylcholine (Ach). The Ach-induced CBF increase was significantly inhibited by calmidazolium (calmodulin antagonist), SQ22536 (adenylate cyclase inhibitor), ODQ (guanylate cyclase inhibitor), KT5720 (protein kinase A inhibitor), and KT5823 (protein kinase G inhibitor). Fluorodinitrobenzene (creatine kinase inhibitor) completely inhibited the ciliary beat in a time- and dose-dependent manner. These results indicate that Panx1 and P2X7 coexist at the cilia of the human nasal epithelial cells and that the ciliary beat is regulated by calmodulin, adenylate/guanylate cyclases and protein kinases A/G, and crucially depends on creatine kinase.

Beat wave method for mode pair extraction of a bell type structure

This paper presents a mode pair extraction method for a bell-type structure that employs a generated beat response signal. Due to the occurrence of small asymmetries in the bell structure, a mode pair can be observed on the circumference. Each mode in the pair has very close frequencies and interference between these frequencies produces beats. Beats are a very interesting acoustics phenomenon in the bell sound. Controlling the beat characteristics requires extraction of a mode pair after the bell is cast. The conventional modal test needed excitation force and response signals at several points. On the contrary, the proposed method requires only the beat response measured at two points on the circumference. This method applied the theory of shell-of-revolution and measured the amplitude ratios of the beat wave’s peak and the valley. The position of the nodes and anti-nodes of the mode pair was determined using the amplitude ratio and the auto-spectrum. The validity of the new method was verified by comparing the experimental results with those of the multi-point test method. Moreover, this method is much simpler and faster than the conventional ones.

Phenotyping ciliary dynamics and coordination in response to CFTR-modulators in Cystic Fibrosis respiratory epithelial cells

Personalized approaches for systematically assessing ciliary beat dynamics and for drug testing would improve the challenging task of diagnosing and treating respiratory disorders. In this pilot study, we show how multiscale differential dynamic microscopy (multi-DDM) can be used to characterize collective ciliary beating in a non-biased automated manner. We use multi-DDM to assess the efficacy of different CFTR-modulating drugs in human airway epithelial cells derived from subjects with cystic fibrosis (ΔF508/ΔF508 and ∆F508/-) based on ciliary beat frequency and coordination. Similar to clinical observations, drug efficacy is variable across donors, even within the same genotype. We show how our assay can quantitatively identify the most efficient drugs for restoring ciliary beating for each individual donor. Multi-DDM provides insight into ciliary beating responses following treatment with drugs, and has application in the broader context of respiratory disease and for drug screening.

The effect of cubic stiffness nonlinearity on the vortex-induced vibration of a circular cylinder at low Reynolds numbers

The vortex-induced vibration (VIV) of a circular cylinder elastically supported by linear and cubic springs is investigated numerically at low Reynolds numbers. The cylinder has a low mass ratio and zero structural damping. Nine dimensionless cubic stiffness nonlinearity strength values are considered. It is found that within the parameter space examined, the VIV response for the linear and softening springs can be divided into four regimes, namely the initial, upper, lower and desynchronised regimes. When the softening spring nonlinearity gets stronger, there exist a reduction in the peak amplitude and shifts in the initial-upper branch and upper-lower branch transitions to lower Reynolds number ranges. In contrast, as the hardening spring nonlinearity increases, the response envelope moves to a higher Reynolds number range and the profile of the initial and upper branches becomes smoother with the lower branch gradually disappearing. In the hardening spring case, the beating response is observed near the low end of the initial branch up to the high end of the initial branch. The modulations in the vibration amplitude gradually diminish with increasing Reynolds number. The cubic spring results coincide with those of the linear spring when they are presented with the equivalent reduced velocity. Due to the low Reynolds number range considered, the majority of the vortex shedding is in the 2S mode. The wake in the cases with smaller vibration amplitudes exhibits a single-row configuration. Whereas, a double-row vortex street is mainly observed in the upper branch. Disorders in the wake are found to be associated with beating responses which have larger vibration amplitudes.

Non-linearities in the Rod and Cone Photoreceptor Inputs to the Afferent Pupil Light Response.

Purpose: To assess the nature and extent of non-linear processes in pupil responses using rod- and cone-isolating visual beat stimuli.Methods: A four-primary photostimulating method based on the principle of silent substitution was implemented to generate rod or cone isolating and combined sinusoidal stimuli at a single component frequency (1, 4, 5, 8, or 9 Hz) or a 1 Hz beat frequency (frequency pairs: 4 + 5, 8 + 9 Hz). The component frequencies were chosen to minimize the melanopsin photoresponse of intrinsically photosensitive retinal ganglion cells (ipRGCs) such that the pupil response was primarily driven by outer retinal photoreceptor inputs. Full-field (Ganzfeld) pupil responses and electroretinograms (ERGs) were recorded to the same stimuli at two mesopic light levels (−0.9 and 0 log cd/m2). Fourier analysis was used to derive the amplitudes and phases of the pupil and ERG responses.Results: For the beat frequency condition, when modulation was restricted to the same photoreceptor type at the higher mesopic level (0 log cd/m2), there was a pronounced pupil response to the 1 Hz beat frequency with the 4 + 5 Hz frequency pair and rare beat responses for the 8 + 9 Hz frequency pair. At the lower mesopic level there were few and inconsistent beat responses. When one component modulated the rod excitation and the other component modulated the cone excitation, responses to the beat frequency were rare and lower than the 1 Hz component frequency condition responses. These results were confirmed by ERG recordings.Conclusions: There is non-linearity in both the pupil response and electroretinogram to rod and cone inputs at mesopic light levels. The presence of a beat response for modulation components restricted to a single photoreceptor type, but not for components with cross-photoreceptor types, indicates that the location of a non-linear process in the pupil pathway occurs at a retinal site earlier than where the rod and cone signals are combined, that is, at the photoreceptor level.

TNFα Affects Ciliary Beat Response to Increased Viscosity in Human Pediatric Airway Epithelium.

In airway epithelium, mucociliary clearance (MCC) velocity depends on the ciliary beat frequency (CBF), and it is affected by mucus viscoelastic properties. Local inflammation induces secretion of cytokines (TNFα) that can alter mucus viscosity; however airway ciliated cells have an autoregulatory mechanism to prevent the collapse of CBF in response to increase in mucus viscosity, mechanism that is associated with an increment in intracellular Ca+2 level ([Ca2+]i). We studied the effect of TNFα on the autoregulatory mechanism that regulates CBF in response to increased viscosity using dextran solutions, in ciliated cells cultured from human pediatric epithelial adenoid tissue. Cultures were treated with TNFα, before and after the viscous load was changed. TNFα treatment produced a significantly larger decrease in CBF in cultures exposed to dextran. Furthermore, an increment in [Ca2+]i was observed, which was significantly larger after TNFα treatment. In conclusion, although TNFα has deleterious effects on ciliated cells in response to maintaining CBF after increasing viscous loading, it has a positive effect, since increasing [Ca2+]i may prevent the MCC collapse. These findings suggest that augmented levels of TNFα associated with an inflammatory response of the nasopharyngeal epithelium may have dual effects that contribute to maintaining the effectiveness of MCC in the upper airways.

Human cortical responses to slow and fast binaural beats reveal multiple mechanisms of binaural hearing.

When two tones with slightly different frequencies are presented to both ears, they interact in the central auditory system and induce the sensation of a beating sound. At low difference frequencies, we perceive a single sound, which is moving across the head between the left and right ears. The percept changes to loudness fluctuation, roughness, and pitch with increasing beat rate. To examine the neural representations underlying these different perceptions, we recorded neuromagnetic cortical responses while participants listened to binaural beats at a continuously varying rate between 3 Hz and 60 Hz. Binaural beat responses were analyzed as neuromagnetic oscillations following the trajectory of the stimulus rate. Responses were largest in the 40-Hz gamma range and at low frequencies. Binaural beat responses at 3 Hz showed opposite polarity in the left and right auditory cortices. We suggest that this difference in polarity reflects the opponent neural population code for representing sound location. Binaural beats at any rate induced gamma oscillations. However, the responses were largest at 40-Hz stimulation. We propose that the neuromagnetic gamma oscillations reflect postsynaptic modulation that allows for precise timing of cortical neural firing. Systematic phase differences between bilateral responses suggest that separate sound representations of a sound object exist in the left and right auditory cortices. We conclude that binaural processing at the cortical level occurs with the same temporal acuity as monaural processing whereas the identification of sound location requires further interpretation and is limited by the rate of object representations.

Damping identification in rotors from run-up beat responses using Hilbert transforms

In a rotor bearing system operating with constant angular acceleration, after passing through the critical speed, typical beat characteristics are observed because the transverse vibration response contains both excited and natural motion, and shortly after passing resonance, vibrations with close frequencies appear. The present study explains a method for estimating damping of rotor bearing systems from transient beat vibration signals observed during run up stage. A mathematical derivation to prove that a part of run-up vibration of the rotor system consists of beat phenomenon when the system crosses critical speed. It is also observed from the mathematical model that the beat vibrations depend on the damping in the system. This beat response is considered for Hilbert analysis and the damping is estimated. Increase in angular acceleration of the rotor will increase the damping. This paper investigates how the damping varies with respect to different angular acceleration values of the rotor bearing system. Experimental validation of the beat phenomenon and damping estimation are done for the rotor system. The proposed method is validated by using half-power band width method applied to run-up response.

Yellow poplar (Liriodendron tulipiferaL.)grown in Korea versus imported Eucalyptus globules as a raw material for kraft pulping

Yellow poplar grown in Korea and imported eucalyptus were compared their kraft pulping characteristics and evaluated the replacing possibility of eucalyptus by yellow poplar. Difference between yellow poplar and eucalyptus were investigated in chemical composition and fiber morphology. Yellow poplar kraft pulp resulted in the higher yield, longer fiber length and thicker fiber, and higher pulp strength than that of eucalyptus. More xylan survived in eucalyptus than yellow poplar during kraft pulping, which led to similar pulp yield even though polysaccharides in Eucalyptus was 4.5% less than in yellow poplar. Longer and thicker yellow poplar pulp fiber resulted in better beating response and pulp strength properties.

Estimation of damping in rotors using complex morlet wavelet transform

In a rotor-bearing system running with uniform angular acceleration, after running through the resonance, typical beat vibrations occur because the response of the system consists of the natural and excited motion. Shortly after resonance both are vibrations with frequencies close to each other. The present study explains a method for estimating damping of rotor-bearing systems from transient beat characteristics observed during the run-up stage. A mathematical justification is provided that the transient response of the rotor-bearing system consists of a beat response when the system crosses resonance. It is also clear from the mathematical model that the beat phenomenon observed depends on the level of damping in the system. The beat time period is also dependent on the angular acceleration of the system. This beat response is considered for wavelet analysis and the damping is estimated. Angular acceleration (α) of the rotor often increases the damping effects. This paper investigates how the damping ratio changes with respect to different angular acceleration values of the rotor-bearing system. Experimental validation of the beat phenomenon and damping identification is done for a rotor-bearing system. Validation for the above proposed method is done by the half-power bandwidth method of the run-up response and logarithmic decrement method of the beat response. A damping estimation from the impulse response of the stationary rotor by using wavelet transforms is also presented and validated using the logarithmic decrement method.

Nonstationary regimes of homogeneous Hamiltonian systems in the state of sonic vacuum

In the present paper we study the mechanism that leads to the formation of regular patterns of energy localization and complete recurrent energy transport in the homogeneous systems of anharmonic oscillators and oscillatory chains subjected to a state of sonic vacuum. The basic model under investigation comprises a system of purely anharmonic oscillators as well as oscillatory chains given to a localized excitation where the initial energy is imported to one of the oscillators or oscillatory chains. The results of numerical simulations reveal the existence of a strong classical beating phenomenon, characterized by complete, recurrent, resonant energy exchanges between the oscillators and oscillatory chain and this in the state of sonic vacuum where no regular resonant frequencies can be defined. In this study we show that formation of the recurrent energy exchanges in this highly degenerate model is strictly stipulated by the system parameters. Thus, for instance, choosing the parameter of coupling below a certain threshold leads to significant energy localization on one of the oscillators or oscillatory chains. However, increasing the strength of coupling above the threshold leads to the formation of a strong beating response. The analytical study pursued in this paper predicts the origin of formation of a strong beating phenomenon and provides the necessary conditions on the system parameter for its excitation. Moreover, careful analysis of the beating phenomenon reveals the qualitatively different global bifurcation undergone by this type of highly nonstationary regime. The theoretical study is further extended to the system of coupled purely anharmonic lattices. Thus we show analytically and numerically that excitation of some particular solutions (e.g., spatially periodic standing waves and standing breathers) on one of the lattices results in the formation of similar patterns of energy (wave) localization as well as the regime of complete recurrent interchain energy transport. In particular we demonstrate that the formation of these regimes is solely affected by a particular choice of system parameters. The results of the analytical study are found to be in very good agreement with those of numerical simulations.

Electrophysiological Measurement of Binaural Beats

The purpose of this study was to determine the reliability of the electrophysiological binaural beat steady state response as a gauge of temporal fine structure coding, particularly as it relates to the aging auditory system. The hypothesis was that the response would be more robust in a lower, than in a higher, frequency region and in younger, than in older, adults. Two experiments were undertaken. The first measured the 40 Hz binaural beat steady state response elicited by tone pairs in two frequency regions: lower (390 and 430 Hz tone pair) and higher (810 and 850 Hz tone pair). Frequency following responses (FFRs) evoked by the tones were also recorded. Ten young adults with normal hearing participated. The second experiment measured the binaural beat and FFRs in older adults but only in the lower frequency region. Fourteen older adults with relatively normal hearing participated. Response metrics in both experiments included response component signal-to-noise ratio (F statistic) and magnitude-squared coherence. Experiment 1 showed that FFRs were elicited in both frequency regions but were more robust in the lower frequency region. Binaural beat responses elicited by the lower frequency pair of tones showed greater amplitude fluctuation within a participant than the respective FFRs. Experiment 2 showed that older adults exhibited similar FFRs to younger adults, but proportionally fewer older participants showed binaural beat responses. Age differences in onset responses were also observed. The lower prevalence of the binaural beat response in older adults, despite the presence of FFRs, provides tentative support for the sensitivity of this measure to age-related deficits in temporal processing. However, the lability of the binaural beat response advocates caution in its use as an objective measure of fine structure coding.

A signal decomposition theorem with Hilbert transform and its application to narrowband time series with closely spaced frequency components

Empirical mode decomposition and Hilbert spectral analysis have been extensively studied in recent years for the system identification of structures. It often encounters three challenges: (1) unable to decompose a signal with closely spaced frequency components such as wave groups in ocean engineering and beating responses in structural and mechanical systems, (2) difficult to distinguish the frequency components in a narrowband signal that is commonly seen in the free vibration of structures, and (3) unable to separate small intermittent fluctuations from a large wave. In this paper, a new analytical mode decomposition theorem based on the Hilbert Transform of a harmonics multiplicative time series is developed to address the challenges. The theorem can be applied with two procedures based on the decomposition of the original signal only or the previously decomposed (modified) signals in sequence. Numerical examples for four representative engineering applications indicate that the new theorem is superior to existing methods in decomposing a time series into many signals whose Fourier spectra are non-vanishing over mutually exclusive frequency ranges separated by bisecting frequencies. It is simple in concept, efficient in computation, consistent in performance, and reliable in signal processing. The accuracy of the new theorem is insensitive to noise. The discernable frequency spacing between the dominant frequencies of decomposed signals is theoretically near zero but practically equal to twice the frequency resolution of a finite length time series. Each bisecting frequency can be selected as an average of its two nearby frequencies of interest and is insensitive to other choices between 80% and 120% of the average value. The modified signal decomposition procedure can be less accurate than the original signal decomposition procedure due to potentially accumulated numerical errors in Hilbert transforms.