Beat Pattern Research Articles

Beat perception in polyrhythms: Time is structured in binary units.

In everyday life, we group and subdivide time to understand the sensory environment surrounding us. Organizing time in units, such as diurnal rhythms, phrases, and beat patterns, is fundamental to behavior, speech, and music. When listening to music, our perceptual system extracts and nests rhythmic regularities to create a hierarchical metrical structure that enables us to predict the timing of the next events. Foot tapping and head bobbing to musical rhythms are observable evidence of this process. In the special case of polyrhythms, at least two metrical structures compete to become the reference for these temporal regularities, rendering several possible beats with which we can synchronize our movements. While there is general agreement that tempo, pitch, and loudness influence beat perception in polyrhythms, we focused on the yet neglected influence of beat subdivisions, i.e., the least common denominator of a polyrhythm ratio. In three online experiments, 300 participants listened to a range of polyrhythms and tapped their index fingers in time with the perceived beat. The polyrhythms consisted of two simultaneously presented isochronous pulse trains with different ratios (2:3, 2:5, 3:4, 3:5, 4:5, 5:6) and different tempi. For ratios 2:3 and 3:4, we additionally manipulated the pitch of the pulse trains. Results showed a highly robust influence of subdivision grouping on beat perception. This was manifested as a propensity towards beats that are subdivided into two or four equally spaced units, as opposed to beats with three or more complex groupings of subdivisions. Additionally, lower pitched pulse trains were more often perceived as the beat. Our findings suggest that subdivisions, not beats, are the basic unit of beat perception, and that the principle underlying the binary grouping of subdivisions reflects a propensity towards simplicity. This preference for simple grouping is widely applicable to human perception and cognition of time.

Reconfigurable millimeter-range optical binding of dielectric microparticles in hollow-core photonic crystal fiber.

Optical binding of microparticles offers a versatile playground for investigating the optomechanics of levitated multi-particle systems. We report millimeter-range optical binding of polystyrene microparticles in hollow-core photonic crystal fiber. The first particle scatters the incident LP01 mode into several LP0n modes, creating a beat pattern that exerts a position-dependent force on the second particle. Particle binding results from the interplay of the forces created by counterpropagating beams. A femtosecond trapping laser is used so that group velocity walk-off eliminates disturbance caused by higher order modes accidentally excited at the fiber input. The inter-particle distance can be optically switched over 2 orders of magnitude (from 42 µm to 3 mm), and the bound particle pairs can be translated along the fiber by unbalancing the powers in the counterpropagating trapping beams. The frequency response of a bound particle pair is investigated at low gas pressure by driving with an intensity-modulated control beam. The system offers new degrees of freedom for manipulating the dynamics and configurations of optically levitated microparticle arrays.

Rolling controls sperm navigation in response to the dynamic rheological properties of the environment.

Mammalian sperm rolling around their longitudinal axes is a long-observed component of motility, but its function in the fertilization process, and more specifically in sperm migration within the female reproductive tract, remains elusive. While investigating bovine sperm motion under simple shear flow and in a quiescent microfluidic reservoir and developing theoretical and computational models, we found that rolling regulates sperm navigation in response to the rheological properties of the sperm environment. In other words, rolling enables a sperm to swim progressively even if the flagellum beats asymmetrically. Therefore, a rolling sperm swims stably along the nearby walls (wall-dependent navigation) and efficiently upstream under an external fluid flow (rheotaxis). By contrast, an increase in ambient viscosity and viscoelasticity suppresses rolling, consequently, non-rolling sperm are less susceptible to nearby walls and external fluid flow and swim in two-dimensional diffusive circular paths (surface exploration). This surface exploration mode of swimming is caused by the intrinsic asymmetry in flagellar beating such that the curvature of a sperm's circular path is proportional to the level of asymmetry. We found that the suppression of rolling is reversible and occurs in sperm with lower asymmetry in their beating pattern at higher ambient viscosity and viscoelasticity. Consequently, the rolling component of motility may function as a regulatory tool allowing sperm to navigate according to the rheological properties of the functional region within the female reproductive tract.

Vibronic coupling in energy transfer dynamics and two-dimensional electronic-vibrational spectra.

We introduce a heterodimer model in which multiple mechanisms of vibronic coupling and their impact on energy transfer can be explicitly studied. We consider vibronic coupling that arises through either Franck-Condon activity in which each site in the heterodimer has a local electron-phonon coupling or Herzberg-Teller activity in which the transition dipole moment coupling the sites has an explicit vibrational mode-dependence. We have computed two-dimensional electronic-vibrational (2DEV) spectra for this model while varying the magnitude of these two effects and find that 2DEV spectra contain static and dynamic signatures of both types of vibronic coupling. Franck-Condon activity emerges through a change in the observed excitonic structure, while Herzberg-Teller activity is evident in the appearance of significant side-band transitions that mimic the lower-energy excitonic structure. A comparison of quantum beating patterns obtained from analysis of the simulated 2DEV spectra shows that this technique can report on the mechanism of energy transfer, elucidating a means of experimentally determining the role of specific vibronic coupling mechanisms in such processes.

Higher-Order Fabry-Pérot Interferometer from Topological Hinge States.

We propose an intrinsic three-dimensional Fabry-Pérot type interferometer, coined "higher-order interferometer," that is based on the chiral hinge states of second-order topological insulators and cannot be mapped to an equivalent two-dimensional setting because of higher-order topological obstructions. Quantum interference patterns in the two-terminal conductance of this interferometer are controllable not only by tuning the strength but also, particularly, by rotating the direction of the magnetic field applied perpendicularly to the transport direction. Remarkably, the conductance exhibits a characteristic beating pattern with multiple frequencies depending on the field strength and direction in a unique fashion. Our novel interferometer thus provides feasible and robust magnetotransport signatures for hinge states of higher-order topological insulators.

Reconstruction of the three-dimensional beat pattern underlying swimming behaviors of sperm

The eukaryotic flagellum propels sperm cells and simultaneously detects physical and chemical cues that modulate the waveform of the flagellar beat. Most previous studies have characterized the flagellar beat and swimming trajectories in two space dimensions (2D) at a water/glass interface. Here, using refined holographic imaging methods, we report high-quality recordings of three-dimensional (3D) flagellar bending waves. As predicted by theory, we observed that an asymmetric and planar flagellar beat results in a circular swimming path, whereas a symmetric and non-planar flagellar beat results in a twisted-ribbon swimming path. During swimming in 3D, human sperm flagella exhibit torsion waves characterized by maxima at the low curvature regions of the flagellar wave. We suggest that these torsion waves are common in nature and that they are an intrinsic property of beating axonemes. We discuss how 3D beat patterns result in twisted-ribbon swimming paths. This study provides new insight into the axoneme dynamics, the 3D flagellar beat, and the resulting swimming behavior.Graphic abstract

Detection of photometric variability in the very low-mass binary VHS J1256-1257AB using TESS and Spitzer

Aims. We investigate the photometric properties of the M7.5 equal-mass binary VHS J1256-1257AB, which, combined with the late-L dwarf VHS J1256-1257 b, forms one of the few young triple systems of ultra-cool dwarfs currently known. Methods. We analyzed two-minute TESS and two-second Spitzer archival data with total durations of about 25 days and 36 h, respectively. Typical precision in the data is ±1.5% for TESS and ±0.1% (in 1 min) for Spitzer. Results. The optical and infrared light curves periodically exhibit epochs of quasi-sinusoidal modulation followed by epochs of stochastic variability, which resembles the beat pattern created by two waves of similar frequencies that interfere with each other. Our two-wave model for the TESS data shows that the components of VHS J1256-1257AB rotate with periods of 2.0782 ± 0.0004 h and 2.1342 ± 0.0003 h, which is also supported by the Spitzer observations. As a result, the fluxes of the equally bright VHS J1256-1257A and B alternate between states of phase and anti-phase, explaining the observed photometric variability in their combined light. The projected spectroscopic velocity of VHS J1256-1257AB is remarkably similar to those obtained by combining the measured rotation periods and the expected radii, which indicates that the spin axes of VHS J1256-1257A and B are likely inclined at nearly 90 deg, as previously reported for VHS J1256-1257 b.

Friedel oscillations in graphene gapped by breaking P and T symmetries: Topological and geometrical signatures of electronic structure

The measurement of Friedel oscillations (FOs) is conventionally used to recover the energy dispersion of electronic structure. Besides the energy dispersion, the modern electronic structure also embodies other key ingredients such as the geometrical and topological properties; it is one promising direction to explore the potential of FOs for the relevant measurement. Here, we present a comprehensive study of FOs in substrate-supported graphene under off-resonant circularly polarized light, in which a valley-contrasting feature and topological phase transition occur due to the combined breaking of inversion ($\mathcal{P}$) and time reversal ($\mathcal{T}$) symmetries. Depending on the position of the Fermi level, FOs may be contributed by electronic backscattering in one single valley or two valleys. In the single-valley regime, the oscillation periods of FOs can be used to determine the topological phase boundary of electronic structure, while the amplitudes of FOs distinguish trivial insulators and topological insulators in a quantitative way. In the two-valley regime, the unequal Fermi surfaces lead to a beating pattern (robust two-wave-front dislocations) of FOs contributed by intravalley (intervalley) scattering. This study implies the great potential of FOs in characterizing topological and geometrical properties of the electronic structure of two-dimensional materials.

Clinical characteristics and genetic spectrum of 26 individuals of Chinese origin with primary ciliary dyskinesia

BackgroundPrimary ciliary dyskinesia (PCD) is a rare, highly heterogeneous genetic disorder involving the impairment of motile cilia. With no single gold standard for PCD diagnosis and complicated multiorgan dysfunction, the diagnosis of PCD can be difficult in clinical settings. Some methods for diagnosis, such as nasal nitric oxide measurement and digital high-speed video microscopy with ciliary beat pattern analysis, can be expensive or unavailable. To confirm PCD diagnosis, we used a strategy combining assessment of typical symptoms with whole-exome sequencing (WES) and/or low-pass whole-genome sequencing (WGS) as an unbiased detection tool to identify known pathogenic mutations, novel variations, and copy number variations.ResultsA total of 26 individuals of Chinese origin with a confirmed PCD diagnosis aged 13 to 61 years (median age, 24.5 years) were included. Biallelic pathogenic mutations were identified in 19 of the 26 patients, including 8 recorded HGMD mutations and 24 novel mutations. The detection rate reached 73.1%. DNAH5 was the most frequently mutated gene, and c.8383C > T was the most common mutated variant, but it is relatively rare in PCD patients from other ethnic groups.ConclusionThis study demonstrates the practical clinical utility of combining WES and low-pass WGS as a no-bias detecting tool in adult patients with PCD, showing a clinical characteristics and genetic spectrum of Chinese PCD patients.

Multi-ciliated microswimmers\u2013metachronal coordination and helical swimming

The dynamics and motion of multi-ciliated microswimmers with a spherical body and a small number N (with 5< N < 60) of cilia with length comparable to the body radius, is investigated by mesoscale hydrodynamics simulations. A metachronal wave is imposed for the cilia beat, for which the wave vector has both a longitudinal and a latitudinal component. The dynamics and motion is characterized by the swimming velocity, its variation over the beat cycle, the spinning velocity around the main body axis, as well as the parameters of the helical trajectory. Our simulation results show that the microswimmer motion strongly depends on the latitudinal wave number and the longitudinal phase lag. The microswimmers are found to swim smoothly and usually spin around their own axis. Chirality of the metachronal beat pattern generically generates helical trajectories. In most cases, the helices are thin and stretched, i.e., the helix radius is about an order of magnitude smaller than the pitch. The rotational diffusion of the microswimmer is significantly smaller than the passive rotational diffusion of the body alone, which indicates that the extended cilia contribute strongly to the hydrodynamic radius. The swimming velocity is found to increase with the cilia number N with a slightly sublinear power law, consistent with the behavior expected from the dependence of the transport velocity of planar cilia arrays on the cilia separation.Graphic abstract

The influence of the nasal brushing samples storage conditions on ciliary function

Primary ciliary dyskinesia (PCD) is an inherited otosinopulmonary ciliopathy in which respiratory cilia are stationary or dyskinetic. Digital high speed videomicroscopy (DHSV) is highly sensitive and specific for PCD diagnosis, but lacks standardization, particularly about the conditions for the storage of ciliated epithelial samples before ciliary functional analysis (CFA). Indeed, storage temperature and duration may impact ciliary function, but this has never been extensively studied. We aimed to evaluate the stability of ciliary function over time when nasal brushing samples are conserved either in the fridge (4 °C)or at room temperature (22 °C). Ciliated epithelial samples were obtained by brushing nasal from 9 healthy subjects. These samples were divided equally and conserved either at 4 °C or at 22 °C. Beating cilia were recorded using DHSV at 37 °C immediately, 3 hours and then 9 hours after sampling. CFA was assessed by ciliary beat frequency (CBF) and the % of normal ciliary beat pattern (CBP). There was no significant difference in CFA over time after sampling, regardless of the sample storage temperature ( Table 1 ). This pilot study suggests that stability of CFA may be preserved during 9 hours after sampling, whatever if the sample is conserved at 4 °C or at 22 °C. Larger studies are needed to confirm these preliminary results notably in pathological conditions.

Tapping into linguistic rhythm

Rhythmic properties of speech and language have been a matter of long-standing debates, with both traditional production and perception studies delivering controversial findings. The present study examines the possibility of investigating linguistic rhythm using movement-based paradigms. Informed by the theory and methods of sensorimotor synchronization, we developed two finger-tapping tasks (synchronization and reproduction), and tested them with English participants. The synchronization task required participants to tap along with the beat of a looped sentence while the reproduction task asked them to tap out the perceived beat patterns after listening to a sentence loop. The results showed that both tasks engaged participants in period tracking of a beat-like structure in the linguistic stimuli, though synchronization did so to a greater extent. Patterns obtained in the reproduction task tended to converge toward participants’ spontaneous tapping rates and showed a degree of regularization. Data collected in the synchronization task displayed a consistent anchoring of taps with the vowel onsets. Overall, synchronization performance with language resembled many well-established findings of sensorimotor synchronization with metronome and music. We conclude that our setting of the sensorimotor synchronization paradigm—finger tapping along with looped spoken phrases—is a valid experimentation tool for studying rhythm perception in language.

Design of non-autonomous pH oscillators and the existence of chemical beat phenomenon in a neutralization reaction

The beat in physical systems is a transparent and well-understood phenomenon. It may occur in forced oscillatory systems and as a result of the interference of two waves of slightly different frequencies. However, in chemical systems, the realization of the latter type of the beat phenomenon has been lacking. Here we show that a periodic titration of acid and alkaline solutions with each other using programmable syringe pumps in a continuous stirred-tank reactor exhibits the beat phenomenon in the temporal pH oscillation pattern if the time periods of sinusoidal inflow rates of the reagents are slightly different. Interestingly, the frequency of the chemical beat pattern follows the well-known relationship from physics, namely the frequency of the beat is equal to the absolute value of the difference of the two wave frequencies. Based on our strategy, we can design and engineer non-autonomous pH oscillatory systems, in which the characteristics of the temporal oscillations (amplitude, time period) can easily and precisely be controlled by the experimental conditions such as the inflow rates and feed concentrations. The demonstrated phenomena can be exploited in practical applications, we use the non-autonomous pH oscillators to drive the reversible assembly and disassembly of pH-sensitive building blocks (oleic acid and gold nanoparticles), both highly relevant in nanotechnology and biomedical applications.

Impairment of the ER/mitochondria compartment in human cardiomyocytes with PLN p.Arg14del mutation

The phospholamban (PLN) p.Arg14del mutation causes dilated cardiomyopathy, with the molecular disease mechanisms incompletely understood. Patient dermal fibroblasts were reprogrammed to hiPSC, isogenic controls were established by CRISPR/Cas9, and cardiomyocytes were differentiated. Mutant cardiomyocytes revealed significantly prolonged Ca2+ transient decay time, Ca2+‐load dependent irregular beating pattern, and lower force. Proteomic analysis revealed less endoplasmic reticulum (ER) and ribosomal and mitochondrial proteins. Electron microscopy showed dilation of the ER and large lipid droplets in close association with mitochondria. Follow‐up experiments confirmed impairment of the ER/mitochondria compartment. PLN p.Arg14del end‐stage heart failure samples revealed perinuclear aggregates positive for ER marker proteins and oxidative stress in comparison with ischemic heart failure and non‐failing donor heart samples. Transduction of PLN p.Arg14del EHTs with the Ca2+‐binding proteins GCaMP6f or parvalbumin improved the disease phenotype. This study identified impairment of the ER/mitochondria compartment without SR dysfunction as a novel disease mechanism underlying PLN p.Arg14del cardiomyopathy. The pathology was improved by Ca2+‐scavenging, suggesting impaired local Ca2+ cycling as an important disease culprit.

Analytical study of spin current density and spin-transfer torque in semi-Dirac heterostructures

Using a low energy effective Hamiltonian for a ferromagnetic semi-Dirac material the energy eigenvalues and eigenvectors for a heterostructure including ferromagnet/normal metal/ferromagnet (FM/NM/FM) made of semi-Dirac materials have been obtained. Then analytic expressions for spin current density components and spin transfer torques for the heterostructure as a function of the ferromagnetic magnetization, chemical potential as well as length of the spacer layer have been obtained. It is shown that the spin current density and spin transfer torques are very sensitive functions of the length and chemical potential of the spacer layer. More interestingly,a beating pattern of oscillations, in terms of the thicknessof the NM spacer, occurs for the y-component of both the STT and spin current density. The variation of spin transfer torque components versus the angular and azimuthal angles for the second magnetization direction is also noteworthy, where we get symmetric behaviour but different magnitudes. The obtained calculations make possible to study the spin current density and spin transfer torques regarding the arrangement of the magnetizations in the two ferromagnetic layers.

Involvement of Huntingtin in Development and Ciliary Beating Regulation of Larvae of the Sea Urchin, Hemicentrotus pulcherrimus.

The multiple functions of the wild type Huntington’s disease protein of the sea urchin Hemicentrotus pulcherrimus (Hp-Htt) have been examined using the anti-Hp-Htt antibody (Ab) raised against synthetic oligopeptides. According to immunoblotting, Hp-Htt was detected as a single band at around the 350 kDa region at the swimming blastula stage to the prism larva stage. From the 2-arm pluteus stage (2aPL), however, an additional smaller band at the 165 kDa region appeared. Immunohistochemically, Hp-Htt was detected in the nuclei and the nearby cytoplasm of the ectodermal cells from the swimming blastula stage, and the blastocoelar cells from the mid-gastrula stage. The Ab-positive signal was converged to the ciliary band-associated strand (CBAS). There, it was accompanied by several CBAS-marker proteins in the cytoplasm, such as glutamate decarboxylase. Application of Hp-Htt morpholino (Hp-Htt-MO) has resulted in shortened larval arms, accompanied by decreased 5-bromo-2-deoxyuridin (BrdU) incorporation by the ectodermal cells of the larval arms. Hp-Htt-MO also resulted in lowered ciliary beating activity, accompanied by a disordered swirling pattern formation around the body. These Hp-Htt-MO-induced deficiencies took place after the onset of CBAS system formation at the larval arms. Thus, Hp-Htt is involved in cell proliferation and the ciliary beating pattern regulation signaling system in pluteus larvae.

Observational Evidence for Beat Phenomenon in Complex Solar Type III Radio Bursts

Abstract We present new observational evidence for one of the most important three wave interactions, called the electrostatic decay instability (ESD) in the source regions of complex solar type III radio bursts (L is the electron beam-excited Langmuir wave, and and S are the ESD excited daughter Langmuir and ion sound waves, respectively). The STEREO in situ wave observations in the source regions of complex type III bursts show that Langmuir waves often occur as one-dimensional magnetic field aligned beat-type wave packets, with peak intensities well in excess of the threshold for excitation of ESD, and with spectra containing (a) two closely spaced narrow peaks (L and ) corresponding probably to the beating modes responsible for the beat patterns at frequencies very close to the local electron plasma frequency, f pe , and (b) narrow peaks at ion sound frequencies, f S , which are very close to beat frequencies. Using the FFT and higher order spectral techniques, we show that the frequency, wavevector and phase resonance conditions required for excitation of ESD are well satisfied for these wave packets, and the speeds of electron beams derived from the resonance conditions agree reasonably well with those derived from the drift rates of the associated type III events. We also show that the merging of (L) and ( ) most probably is the excitation mechanism of the second harmonic radio emission of these type III bursts.

A Tail's Tale: Biomechanical Roles of Dorsal Thoracic Spine of Barnacle Nauplii.

Many marine invertebrates have complex life histories that begin with a planktonic larval stage. Similar to other plankton, these larval invertebrates often possess protruding body extensions, but their function beyond predator deterrence is not well-documented. For example, the planktonic nauplii of crustaceans have spines. Using the epibiotic pedunculate barnacle Octolasmis spp., we investigated how the dorsal thoracic spine affects swimming and fluid disturbance by comparing nauplii with their spines partially removed against those with intact spines. Our motion analysis showed that amputated Octolasmis spp. swam slower, in jerkier trajectories, and were less efficient per stroke cycle than those with intact spines. Amputees showed alterations in limb beat pattern: larger beat amplitude, increased phase lag, and reduced contralateral symmetry. These changes might partially help increase propulsive force generation and streamline the flow, but were insufficient to restore full function. Particle image velocimetry further showed that amputees had a larger relative area of influence, implying elevated risk by rheotactic predator. Body extensions and their interactions with limb motion play important biomechanical roles in shaping larval performance, which likely influences the evolution of form.

A new kind of beat

New mathematical model reveals how the flagella of some single-celled algae generate a lasso-like beat pattern that propels the cell through water.

Higher throughput drug screening for rare respiratory diseases: readthrough therapy in primary ciliary dyskinesia.

BackgroundDevelopment of therapeutic approaches for rare respiratory diseases is hampered by the lack of systems that allow medium-to-high-throughput screening of fully differentiated respiratory epithelium from affected patients. This is a particular problem for primary ciliary dyskinesia (PCD), a rare genetic disease caused by mutations in genes that adversely affect ciliary movement and consequently mucociliary transport. Primary cell culture of basal epithelial cells from nasal brush biopsies followed by ciliated differentiation at the air–liquid interface (ALI) has proven to be a useful tool in PCD diagnostics but the technique's broader utility, including in pre-clinical PCD research, has been restricted by the limited number of basal cells that can be expanded from such biopsies.MethodsWe describe an immunofluorescence screening method, enabled by extensive expansion of basal cells from PCD patients and the directed differentiation of these cells into ciliated epithelium in miniaturised 96-well transwell format ALI cultures. As proof-of-principle, we performed a personalised investigation in a patient with a rare and severe form of PCD (reduced generation of motile cilia), in this case caused by a homozygous nonsense mutation in the MCIDAS gene.ResultsInitial analyses of ciliary ultrastructure, beat pattern and beat frequency in the 96-well transwell format ALI cultures indicate that a range of different PCD defects can be retained in these cultures. The screening system in our proof-of-principal investigation allowed drugs that induce translational readthrough to be evaluated alone or in combination with nonsense-mediated decay inhibitors. We observed restoration of basal body formation but not the generation of cilia in the patient's nasal epithelial cells in vitro.ConclusionOur study provides a platform for higher throughput analyses of airway epithelia that is applicable in a range of settings and suggests novel avenues for drug evaluation and development in PCD caused by nonsense mutations.