External Oscillation Research Articles

Stability of thermal convection in two superimposed miscible viscous fluids under gravitational modulation

Abstract The thermal stability of a system of two superimposed miscible viscous fluid layers, under gravitational modulation, is investigated using linear stability analysis. It is well known in the literature that in the absence of gravitational modulation, there exist two convection regimes depending on the buoyancy number: the single-cell regime, where convection is oscillating and occupies the entire volume of the two fluid layers, and the stratified regime where stationary convection occurs in each fluid layer. Using Chebyshev's spectral collocation method and Floquet's theory, the numerical results show that under gravitational modulation, single-cell convection oscillates at half the frequency of the external oscillation (subharmonic threshold), while the stratified regime oscillates at a frequency equal to that of the forcing (harmonic threshold). The critical buoyancy number corresponding to the transition between the two convection regimes depends, in addition to the viscosity ratio and the depth of the two layers, on certain dimensionless frequencies permeating this transition and also on the amplitude of oscillation via the Froude number. In the plane of the critical Rayleigh number versus dimensionless modulation frequency, the branch associated with stratified convection does not depend on the buoyancy number for equal viscosities whereas this is the case for the whole-convection regime. For different viscosities, both convection regimes depend on the buoyancy number. At last, in the stratified regime (harmonic threshold), the critical value of the viscosity contrast, corresponding to the passage from an active layer to a passive layer and vice versa, increases with the modulation frequency.

Modeling and analysis of a two-stage tri-linear pendulum ultra-low frequency horizontal vibration isolator with experimental investigations.

In engineering practice, the external horizontal oscillations always influence the working performance of precise instruments, advanced manufacture equipment, and gravitational wave detection. In order to ensure the normal operation of these instruments, it is necessary to attenuate these vibrations adequately. The pendulum mechanism horizontal vibration isolator is an efficient method. Hence, this paper presents a type of two-stage tri-linear pendulum horizontal vibration isolator (TPHVI). The first-stage TPHVI is connected in series with the second-stage one. The dynamic equations of the two-stage TPHVI are subsequently established so that the vibration isolation performance of the two-stage TPHVI is acquired. The analysis result of the natural frequency of the two-stage TPHVI reveals that it can obtain a low frequency vibration isolation performance when the first-stage TPHVI swings in a small value. As a case study, an experimental rig is constructed. The measured transmissibility keeps in good agreement with the calculated one. The natural frequency of the second-stage TPHVI is 0.25Hz. The initial vibration isolation frequency is 0.3Hz. When the external frequency is 0.8Hz, the transmissibility of the second-stage TPHVI reaches -20 dB. Meanwhile, when the external frequency is 3Hz, the transmissibility of the second-stage TPHVI is -40 dB. These measured data demonstrate that the proposed two-stage TPHVI can realize low frequency vibration isolation horizontally, which will have broad application prospects in the field of ultra-precision in engineering practice.

Fluctuations in the “static” atmosphere and their effects on tropospheric ozone distribution

Atmospheric fluctuation can be seen everywhere. This study focuses on the record-breaking increase of O3 concentration during the summer in some sensitive areas in recent years. The findings indicate that in the vicinity of the East Asian continent near western Pacific ocean, when the atmospheric conditions are stable or neutral, it is conducive to the maintenance and propagation of atmospheric oscillations near the height of the pollutant mixed layer (H_PML). Accompanied by the "peak-trough" effect of external gravity wave oscillations, due to the abundant water vapor of the cloud system (there are low pressure or typhoon disturbances in summer) near the large-scale cloud belt at the edge of the subtropical high in the western Pacific, the bright temperature at cloud top shows "light and dark changes" on satellite images, forming a wave-like cloud system. The novelty of this study lies in the fact that atmospheric fluctuations near the H_PML is not only related to the known aggravation of heavy rainfall, but also leads to the additional value-added effect of aerosols. Under static atmospheric conditions, the impact of atmospheric fluctuations near the H_PML on additional rise of O3 concentration helps us to deepen our understanding of the so-called "entrained ozone (EZ) effect" in the atmosphere. Due to the external gravity waves, the concentration of O3 increased further. Diurnal variations of solar zenith angle and H_PML are key meteorological factors influencing the significant increase in near-surface O3 concentration entrainment. The formation mechanism of solar photochemical O3 is further deepened and supplemented by analyzing the record-breaking increase of O3 concentration in summer observed in recent years.

Lubricant depletion and interface dynamics in liquid-infused microchannel subjected to external oscillations

Lubricant-infused surfaces (LIS) find suitability in a plethora of applications due to their omniphobic functionalities. LIS, however, lose their functionality in the absence of the lubricant. A majority of the studies have focused on understanding the liquid-repellent properties of LIS, but only limited attention has been paid to understanding their durability. In this work, we focus on the interface dynamics for prolonging the durability of LIS during transport for food packaging applications. We analyze the lubricant retention characteristics within cavities when subjected to pure oscillations (zero net flow). The microchannel is excited at f=0.1–10 Hz for viscosity ratio (μr=0.4–1.0 and μr=1.8) for a dovetail cavity with lubricant of two different densities. The failure and stability of LIS are characterized based on the orientation of velocity vectors and the position of vortex formed within the cavity. A random orientation of velocity vectors within the cavity signifies failure of LIS. External oscillations cause the interface to rupture and form drops. Upon rupture, drops of both the external liquid and lubricant are present in the cavity leading to a chaotic interaction between the two fluids and finally resulting in random orientation of vectors. On the other hand, a vortex formed at the liquid–lubricant interface signifies a stable LIS with an intact meniscus. The results show that the stability of LIS has a strong dependence on the viscosity of external liquid and the density of lubricant. A more viscous external liquid and a denser lubricant dampen the vibration effects, thereby exhibiting a stable state with an intact meniscus. The amplitude variation (A=0.001–0.1 m) surprisingly does not show a significant variation in the failure states. Furthermore, the rate of depletion of lubricant from the cavity and its effect on meniscus failure with time are also illustrated. The results from this work will aid in realizing a robust LIS system with prolonged lubricant retention.

Cosmological constraints on early dark energy from the full shape analysis of eBOSS DR16

ABSTRACT We evaluate the effectiveness of early dark energy (EDE) in addressing the Hubble tension using the luminous red galaxy (LRG), quasar (QSO), and emission line galaxy (ELG) samples from the completed eBOSS survey. We perform cosmological parameter measurements based on full shape analysis of the power spectrum employing the effective field theory of large-scale structure (EFTofLSS). EDE is known to strongly suffer from volume projection effects, complicating cosmological constraints’ interpretation. To quantify the volume projection effects within an EDE full shape analysis, we explore the impact of different prior choices on the nuisance parameters of EFTofLSS through an extensive mock study. We compare classical Gaussian priors to the non-informative Jeffreys prior, known to mitigate volume projection effects in ΛCDM. Our full shape analysis combines eBOSS and BOSS data with Planck, external Baryon Acoustic Oscillation (BAO), PantheonPlus, and SH0ES supernova data. EDE reduces the tension from 5.2σ to 3σ compared to ΛCDM, yielding $H_0=71.73_{-0.86}^{+0.82}$ km s−1 Mpc−1 with $f_\mathrm{EDE} = 0.1179_{-0.022}^{+0.025}$ (Gaussian priors) and $H_0=72.03_{-0.87}^{+0.82}$ km s−1 Mpc−1 with $f_\mathrm{EDE} = 0.1399_{-0.022}^{+0.023}$ (Jeffreys prior). Although the Hubble tension is mitigated compared to ΛCDM, the inclusion of eBOSS data amplifies the tension within EDE from 2σ to 3σ, in contrast to the full shape analysis of BOSS data with Planck, external BAO, PantheonPlus, and SH0ES. This highlights the significance of incorporating additional large-scale structure data in discussions concerning models aiming to resolve the Hubble tension.

Harmonic resonance and entrainment of propagating chemical waves by external mechanical stimulation in BZ self-oscillating hydrogels

Smart polymer materials that are nonliving yet exhibit complex "life-like" or biomimetic behaviors have been the focus of intensive research over the past decades, in the quest to broaden our understanding of how living systems function under nonequilibrium conditions. Identification of how chemical and mechanical coupling can generate resonance and entrainment with other cells or external environment is an important research question. We prepared Belousov-Zhabotinsky (BZ) self-oscillating hydrogels which convert chemical energy to mechanical oscillation. By cyclically applying external mechanical stimulation to the BZ hydrogels, we found that when the oscillation of a gel sample entered into harmonic resonance with the applied oscillation during stimulation, the system kept a "memory" of the resonant oscillation period and maintained it post stimulation, demonstrating an entrainment effect. More surprisingly, by systematically varying the cycle length of the external stimulation, we revealed the discrete nature of the stimulation-induced resonance and entrainment behaviors in chemical oscillations of BZ hydrogels, i.e., the hydrogels slow down their oscillation periods to the harmonics of the cycle length of the external mechanical stimulation. Our theoretical model calculations suggest the important roles of the delayed mechanical response caused by reactant diffusion and solvent migration in affecting the chemomechanical coupling in active hydrogels and consequently synchronizing their chemical oscillations with external mechanical oscillations.

Effect of bending deformation on suspended topological insulator nanowires: Towards a topological insulator based NEM switch

Nanodevices consisting of the suspended and supported parts of topological insulator Bi2Se3 nanowires were fabricated and measured at low and room temperatures. Probing of topological surface states, accompanied by the electrostatic field effect used to dynamically manipulate bending deformation, was carried out to monitor the external strain introduced into the suspended and supported parts within the same Bi2Se3 nanowire. Depending on the device geometry, pure elastic and elastoplastic types of concave deformation, as well as convex buckling deformation, were realized in the suspended parts of the nanowires. For various types of observed deformations, different magnitudes of increase in the Source-Drain resistance of the deformed part compared to the relaxed part of the same devices were determined. All suspended devices exhibit external strain-sensitive Shubnikov-de Haas oscillation frequencies representing the carriers of top and bottom surface states and bulk, whereas, in the case of supported devices, the bottom surface states are masked by a trivial 2DEG. The obtained results may be useful for strain engineering of TI materials, as well as for applications in NEMS and other areas related to suspended nanostructures.

Trained recurrent neural networks develop phase-locked limit cycles in a working memory task.

Neural oscillations are ubiquitously observed in many brain areas. One proposed functional role of these oscillations is that they serve as an internal clock, or 'frame of reference'. Information can be encoded by the timing of neural activity relative to the phase of such oscillations. In line with this hypothesis, there have been multiple empirical observations of such phase codes in the brain. Here we ask: What kind of neural dynamics support phase coding of information with neural oscillations? We tackled this question by analyzing recurrent neural networks (RNNs) that were trained on a working memory task. The networks were given access to an external reference oscillation and tasked to produce an oscillation, such that the phase difference between the reference and output oscillation maintains the identity of transient stimuli. We found that networks converged to stable oscillatory dynamics. Reverse engineering these networks revealed that each phase-coded memory corresponds to a separate limit cycle attractor. We characterized how the stability of the attractor dynamics depends on both reference oscillation amplitude and frequency, properties that can be experimentally observed. To understand the connectivity structures that underlie these dynamics, we showed that trained networks can be described as two phase-coupled oscillators. Using this insight, we condensed our trained networks to a reduced model consisting of two functional modules: One that generates an oscillation and one that implements a coupling function between the internal oscillation and external reference. In summary, by reverse engineering the dynamics and connectivity of trained RNNs, we propose a mechanism by which neural networks can harness reference oscillations for working memory. Specifically, we propose that a phase-coding network generates autonomous oscillations which it couples to an external reference oscillation in a multi-stable fashion.

Shared External Driver for VHF Converter With a Synchronous Rectifier Based on Matching Network Parameters Optimization

In order to reduce the conduction loss of diode, synchronous rectification is usually adopted in very-high-frequency (VHF) converters, in which the rectifier diode is replaced by a MOSFET with very low on-state resistance. And to ensure normal operation of the synchronous rectifier switch, it is necessary to design a suitable driver with accurate timing. The widely used self-oscillating resonant drive circuit has a limited range of duty cycle adjustment, and the body diode of synchronous rectifier switch has long on-state time and a large conduction loss. Therefore, based on the analysis and parameters optimization of matching network, a shared external drive circuit is put forward. That is, the drive signals of the inverter switch and the synchronous rectifier switch come from the same external oscillation signal. On the premise of ensuring accurate drive timing, it can improve the drive signal's duty cycle of synchronous rectifier switch, reduce the conduction loss of body diode, and improve the efficiency of converter. Then on the basis of the proposed drive circuit, a VHF converter prototype with operating frequency of 10 MHz, 13 V input and 8 V/10 W output is designed, and the feasibility of the proposed drive circuit is verified by simulations together with experiments.

Regulation of mechanical force on cardiomyocytes beating

The mechanical behavior of cardiomyocytes plays an essential role in maintaining life and health. It is traditionally believed that both electrical signals and chemical signals modulate the cardiomyocytes behaviors. Recent discoveries have elucidated that the physical cues of microenvironment can regulate cell activities such as proliferation, spreading, migration, and differentiation. However, there is still limited research on regulating cardiomyocytes beating through mechanical force. Herein we prepare different polyacrylamide gels coated with different cell adhesion ligand proteins to simulate the physical microenvironment of cardiomyocytes. Then the mechanical loading forces are loaded by using a tungsten probe to stretch elastic hydrogels which can emulate the mechanical oscillations induced by the beating of adjacent cardiomyocytes. We investigate the responsive behavior of cardiomyocytes to external mechanical oscillations within various physical microenvironments. Firstly, we load 1 Hz mechanical oscillation on the matrix (<i>E</i> = 11 kPa) with different kinds and concentrations of ligands (0, 5, 20, 100 μg/mL) to stimulate cardiomyocytes and observe their mechanical response behavior. Our findings indicate that all kinds of ligands including Laminin, Fibronectin and Collagen I , can mediate the cardiomyocytes response to extrinsic mechanical oscillatory stimuli, which might be due to distinct mechanisms of mechanical force coupling (Fig. (b)). This suggests that mechanical force signals can regulate the beating of cardiomyocytes through matrix-ligand-cell signaling pathway, thereby inducing intercellular coupled oscillations for rhythmic control of cardiomyocytes. Cardiomyocytes cultured on the matrix coated with 20 μg/mL Laminin show the highest and most stable response fraction. We hypothesize that there exist dual force transduction pathways for Laminin binding to integrin and dystrophin glycoprotein complex (DGC) (Fig. (a)). We further analyze the cardiomyocytes behaviors under mechanical oscillation with different values of substrate stiffness (<i>E</i> = 1.8, 11, 27 kPa) and concentrations of Laminin (0, 5, 20, 100 μg/mL). We find that cardiomyocytes cultured on 1.8 kPa coated with 20 μg/mL Laminin show the highest response fraction (Fig. (c)). Our results demonstrate that the stiffness of substrate, the type and density of cell adhesion ligands, as well as the strength and rhythm of the mechanical signals can synergetically affect the cardiomyocytes responses to external mechanical stimulations, which provides the foundation for understanding the diseases such as cardiac arrhythmias and heart failure following myocardial infarction.

Генератор хаотических колебаний

The article analyzes existing schemes of chaos generators. Numerical and simulation modeling is carried out aimed at identifying chaotic dynamics. Based on wellknown concepts, a chaos generator is developed and a simulation model is built. A mathematical description of the generator is given and phase portraits are obtained. Diagrams of chaotic oscillations of the Lorentz model and the Colpitts model are presented. The operation of the Van der Pol generator is considered and the chaotic processes that arise during external harmonic oscillations are shown. Chua's model is presented, its mathematical description is given, and an analysis of oscillations in the deterministic chaos regime is presented.

Reliability and variability of pressure reactivity index (prx) during oscillatory pattern in arterial blood pressure and intracranial pressure in traumatic brain injured patients

IntroductionPressure reactivity index (PRx) is used for continuous monitoring of cerebrovascular reactivity in traumatic brain injury (TBI). However, PRx has a noisy character. Oscillations in arterial blood pressure (ABP) introduced by cyclic positive end-expiratory pressure adjustment, can make PRx more reliable. However, if oscillations are introduced by the cycling process of an anti-decubitus-mattress the effect on PRx is confounding, as they affect directly also intracranial pressure (ICP). In our routine monitoring in TBI patients we noticed periods of highly regular, slow, spontaneous oscillations in ABP and ICP signals. Research questionWe set out to explore the nature of these oscillations and establish if PRx remains reliable during the oscillations. Materials and methods10 TBI patients’ recordings with oscillations in ICP and ABP were analysed. We computed PRx, PRx variability (hourly-average of standard-deviation, SD), phase-shift and coherence between ABP and ICP in the slow frequency range. Metrics were compared between oscillation and peri-oscillation periods. ResultsDuring oscillations (frequency 0.006± 0.002Hz), a significantly lower variability of PRx (SD 0.185vs0.242) and higher coherence ABP-ICP (0.618±0.09 vs 0.534 ±0.09) were observed. No external oscillations sources could be identified. 34 out of 48 events showed signs of 'active' transmission associated with negative PRx, indicating a potential positive impact on PRx reliability. Discussion and conclusionsSpontaneous oscillations observed in ABP and ICP signals were found to enhance rather than confound PRx reliability. Further research is warranted to elucidate the nature of these oscillations and develop strategies to leverage them for enhancing PRx reliability in TBI monitoring.

Hydrodynamic performance of an elastic capsule oscillating water column type WEC: An experimental study

Wave energy represents a promising and sustainable source of energy with substantial potential. To promote the utilization of wave energy resources as well as develop new wave energy converters (WECs) with application prospects, an innovative elastic capsule oscillating water column (EC-OWC) WEC is proposed, and an initial experimental investigation is conducted on the device. Besides, the expansion characteristics of the elastic capsule and the motion characteristics of the free bulge wave are investigated through bulge wave tests. Moreover, the hydrodynamic performances of the device on the condition that coupled with traveling regular waves are investigated through wave tests, as well as the damping characteristics of the impulse turbine model and the ring-opening as power take-off (PTO) systems in the EC-OWC. It indicates that the variation in the speed of the free bulge wave is consistent with the one-dimensional longitudinal wave theory, that the ring-opening model with an opening ratio of 0.76 percent has comparable operating characteristics to the impulse turbine, and that the impulse turbine model has outstanding operating characteristics in the EC-OWC system. The maximum primary hydrodynamic efficiency of the system is approximately 0.475. When the relative water depth is in the interval of approximately 0.07-0.09, the efficiency can reach 0.4. Furthermore, the efficiency increases and subsequently decreases with the variation of the relative hydraulic head, and the efficiency reaches the maximum value when the relative tube length is around 1.6. The results indicate that the one-dimensional longitudinal wave theory can provide support for the design of the elastic capsule. When the capsule length is close to half a wavelength and the internal and external oscillation periods are matched, the system reaches a near-resonant state, and the level of efficiency is optimized. The bulge wave contained within the EC-OWC is a half-wavelength standing wave.

NON-LINEAR MODEL OF A RECUPERATIVE SHOCK ABSORBER

This article examines the rationale for using a shock absorber with the function of recuperating mechanical energy into electrical energy. Current trends in the transport industry, regarding the need to use autonomous power sources in the transport infrastructure, are considered. This direction is promising due to the replacement of vehicles with internal combustion engines by electric transport, as well as the need for autonomous power supply of individual nodes and aggregates. The need for autonomy emerges acutely in the conditions of the energy crisis, and at the same time, the lack of energy resources. Special attention is paid to energy recovery using the direct and conversepiezoelectric effect. The structure, chemical and physical properties, principle of operation and practical application of piezoceramic transducers, and the possibility of their use as energy harvesters (generators) are considered. The considered scientific and technical problem, which consists in determining the nature of the negative impact of various types of external oscillations on the functioning of structural elements of vehicles, to reduce which various shock absorbers or dampers are used. This work considers the use of a recuperative shock absorber of vibration loads with the use of a piezoelectricenergy harvester as a converter of mechanical energy of vibrations into electrical energy. Piezoceramic inserts are used as an energy collector in the design of an automobile hydraulic shock absorber. An assessment of the efficiency of recuperation and conclusions regarding the feasibility of use and implementation are provided. The shock absorbers which are installed to absorb vibrations consume a large amount of mechanical energy, converting it into heat which is dissipated into the atmosphere. This energy, without reducing the efficiency of functioning, can be beneficially used by using a piezoelectric generator with piezoelectric ceramics to convert mechanical energy into electrical energy.

Sensitivity and bifurcation analysis of an analytical model of a trapped object in an externally excited acoustic radiation force field

Acoustic radiation force (ARF) is a nonlinear acoustic phenomenon for which the acoustic field properties and, to an even greater extent, the explicit dynamics of the object, have received limited attention in the published literature to date. Any oscillations due to the flow field or external perturbations are thereby negligible while the particle is trapped in a stable position. By changing the viewpoint from the acoustic field to the dynamics of a levitated particle, the amplitude and frequency of external oscillation is non-negligible, we ask the question of how external excitation changes the dynamics of the object. We explicitly derive an analytical formulation of a trapped object in the form of a Duffing-like equation with its constants being defined by the object itself, the fluid, the acoustic wave, and the external vibration properties. In this case, the bifurcation behaviour is studied, and we show this together with a sensitivity analysis to represent correct dynamic behaviour in certain regimes of the bifurcation diagram.

Low-Frequency Oscillations for Nonlocal Neuronal Coupling in Shared Intentionality Before and After Birth: Toward the Origin of Perception

The theoretical study observes literature to understand whether or not low-frequency oscillations can simultaneously alter the excitability of neurons from peripheral nervous subsystems in different individuals to provide Shared Intentionality in recipients (e.g., fetuses and newborns) and what are the attributes of ecological context for Shared Intentionality. To grasp the perception of objects during environmental learning at the onset of cognition, a fetus needs exogenous factors that could stimulate her nervous system to choose the relevant sensory stimulus. Low-frequency brain oscillations can cause the nonlocal coupling of neurons in peripheral and central nervous subsystems that provide subliminal perception. An external low-frequency oscillator and the proximity of individuals can stimulate the coordination of their heart rates and modulate neuronal excitability. External low-frequency oscillations can increase the cognitive performance of the subjects. The characteristics of this pulsed low-frequency field are oscillations with 400 and 700 nm wavelengths alternately with the pulsed frequency ranging from 1 to 1.6 Hz. This theoretical work contributes to knowledge about nonlocal neuronal coupling in different organisms that can appear due to low-frequency oscillations. The significance of the article is that it explains the neurophysiological processes occurring during Shared Intentionality - one of the central issues in understanding the cognitive development of young children, as the conventional view in cognitive sciences argues. The article's impact is a proposal of the universal mechanism of nonlocal neuronal coupling in shaping the embryonal nervous system in animals of all species, which opens new directions for research on the origin of perception of objects.

Monolithic VECSEL for stable kHz linewidth.

Vertical-external-cavity surface-emitting semiconductor lasers (VECSELs) are of increasing interest for applications requiring ultra-coherence and/or low noise at novel wavelengths; performance that is currently achieved via high-Q, air-spaced resonators to achieve long intra-cavity photon lifetimes (for the so-called class-A low noise regime), power scaling and high beam quality. Here, we report on the development of a compact, electronically tunable, monolithic-cavity, class-A VECSEL (monolithic VECSEL) for ultra-narrow free-running linewidths. A multi-quantum-well, resonant periodic gain structure with integrated distributed Bragg reflector (DBR) was optically-bonded to an air-gap-free laser resonator created inside a right-angle fused-silica prism to suppress the influence of environmental noise on the external laser oscillation, thus achieving high stability. Mode-hop-free wavelength tuning is performed via the stabilized temperature; or electronically, and with low latency, via a shear piezo-electric transducer mounted on the top of the prism. The free-running linewidth, estimated via the frequency power spectral density (PSD), is sub-kHz over ms timescales and <1.9 kHz for time sampling as long as 1s, demonstrating at least two orders-of-magnitude improvement in noise performance compared to previously reported single frequency VECSELs. The stable, total internal reflection resonator concept is akin to the prevalent monolithic non-planar ring oscillator (NPRO), however the monolithic VECSEL has several important advantages: tailored emission wavelength (via semiconductor bandgap engineering), no relaxation oscillations, no applied magnetic field, and low requirements on the pump beam quality. This approach is power-scalable in principle and could be applied to VECSELs at any of the wavelengths from the visible to the mid-infrared at which they are already available, to create a range of robust, ultra-coherent laser systems with reduced bulkiness and complexity. This is of particular interest for remote metrology and the translation of quantum technologies, such as optical clocks, from research laboratories into real world applications.

Modeling the effects of external oscillations on mucus clearance in obstructed airways.

Various therapeutic methods are employed to facilitate the clearance of secretions accumulated in the respiratory tracts of individuals with lower respiratory tract disorders. High-frequency chest wall oscillation (HFCWO) device, designed to apply variable amplitude and frequency vibrations to the individuals' chests, stands out among these therapies. In this study, the effectiveness of this treatment method was investigated numerically using computational fluid dynamics (CFD) on the generated mucus-obstructed bronchial geometry. The conducted analyses compared the effects of vibrations acting in the axial, radial, and tangential directions on the clearance of mucus, which exhibits non-Newtonian flow behavior with shear-thinning properties. Simultaneously, the effects of changes in vibration amplitude and frequency, pressure differentials, fluid properties, and ciliary movements on the flow were separately examined and interpreted. The findings demonstrate that ciliary movements are insufficient in mucus-accumulated airways, applied vibrations enhance mucus clearance, and potential improvements in flow are quite sensitive to boundary conditions.

Shared Intentionality Modulation at the Cell Level: Low-Frequency Oscillations for Temporal Coordination in Bioengineering Systems

The theoretical article aims to develop knowledge about the modulation of shared intentionality at the cellular level. A hypothesis about the neurobiological processes during shared intentionality argues that this pre-perceptual communication occurs through nonlocal neuronal coupling in an ecosystem that can be described as the mother-fetus communication model. The current theoretical study analyses literature to discuss recent findings on the effect of oscillations on neuronal temporal coordination to verify whether external low-frequency oscillations can only synchronize specific local neuronal networks from peripheral and central nervous subsystems for modulating shared intentionality. The review discusses 4 findings. First, gamma oscillations are associated with the temporal coordination of local ensembles of cells. Second, there is a relationship between low-frequency brain oscillations and the temporal coordination of peripheral and central nervous subsystems. Third, delta oscillations influence neuronal activity by modulating gamma activity. Fourth, external delta and gamma oscillations increase cortical excitability. The article concludes that delta oscillations can modulate gamma oscillations in the different subsystems of the nervous system, providing temporal network coordination. An external low-frequency oscillator can coordinate only relevant local neuronal networks in various subsystems already exhibiting gamma activity.

Oscillations and bistability of complex electrochemical reactions in 3D printed microfluidic devices

We investigate the kinetic features of complex charge transfer chemical reactions using a microelectrode integrated in a flow cell made with 3D printing technology. Thin layer electrochemical cells with 350 μm (height) × 1000 μm (width) channels were designed. Ferrocyanide oxidation on a 100 μm diameter Pt electrode using the printed cell showed mass transfer limiting current at large overpotentials. The variation of the limiting current with the flow rate (1 μL/min ≤ Q ≤ 100 μL/min) was interpreted with the superposition of a constant current due to radial diffusion and a Levich-type square-root relationship, indicating a mixed radial diffusion/thin layer mass transport condition. These findings were further supported by numerical simulation of a diffusion-convection equation in the flow channel. Experiments with copper electrodissolution in phosphoric acid electrolyte reproduced oscillatory behavior that was previously seen in macrocells and polydimethylsiloxane (PDMS) microchips. The 3D printed cell can accommodate multiple electrodes – to demonstrate this application we showed that the current oscillations with copper electrodissolution can exhibit frequency synhcronization with a dual electrode configuration. Finally, hydrogen oxidation on a Pt wire in the presence of Cu2+ and Cl− inhibitors displayed bistability at relatively large external resistance and oscillations at high volumetric flow rates. The results show that the 3D printed thin layer design is an alternative to studying nonlinear phenomena in electrochemical cells with distinct advantages to the traditional approaches of using macrocells and PDMS microchip flow cells.