Transverse Motion Research Articles

Lumbopelvic Stability during a Single Leg Step Down Predicts Elbow Varus Torque during Baseball Pitching.

During a baseball pitch, energy is transferred from the lower extremities through the lumbopelvic junction to the upper extremity. Reduced lumbopelvic stability has been associated with elbow injuries, but the mechanisms are unclear. Characterize the predictive ability of lumbopelvic stability on elbow varus torque during a baseball pitch. Cross-Sectional. Facilities at NCAA Division 1 universities. NCAA Division 1 baseball players (N=44; 19.6+1.3yrs). Pitchers completed a warm-up and then threw ten fastballs from a mound to a catcher. During the pitches, elbow varus torque was recorded using an inertial measurement unit and ball velocity was recorded with a radar gun. Participants also completed a single leg step down (SLSD) task with and without a cognitive Stroop, while triplanar pelvic and trunk kinematics were recorded by inertial measurement units. Statistical analysis consisted of a cluster analysis, principal component analysis (PCA), and a multivariate logistic regression model. Cluster analysis revealed 2 clusters: Low Torque-High Velocity and High-Torque-Low Velocity. The PCA analysis revealed 4 patterns of variability (principal components) during the SLSD: 1-sagittal plane, 2-transverse plane, 3-frontal plane trail limb, and 4-frontal plane lead limb. Logistic regression indicated increased transverse plane trunk and pelvis motion predicted higher odds of belonging to the High Torque-Low Velocity cluster; trunk [OR=2.9 (95%CI:1.1,8.0), p=0.036] and pelvis [OR=2.6 (95%CI:1.1,6.0), p=0.031]. Lumbopelvic movement assessed during the SLSD can identify deficits that relate to high elbow torque-low ball velocity during the baseball pitch. Specifically, higher pelvis and trunk transverse plane motion was associated with pitchers in the High Torque-Low Velocity cluster. Our assessment of trunk and pelvis motion during a SLSD provides a method for coaches and clinicians to identify a potential risk factor related to increased elbow varus torque and decreased ball velocity.

Phase control of nonlinear Breit-Wheeler pair creation

Electron-positron pair creation occurs throughout the universe in the environments of extreme astrophysical objects, such as pulsar magnetospheres and black hole accretion disks. The difficulty of emulating these environments in the laboratory has motivated the use of ultrahigh-intensity laser pulses for pair creation. Here we show that the phase offset between a laser pulse and its second harmonic can be used to control the relative transverse motion of electrons and positrons created in the nonlinear Breit-Wheeler process. Analytic theory and particle-in-cell simulations of a head-on collision between a two-color laser pulse and electron beam predict that with an appropriate phase offset, the electrons will drift in one direction and the positrons in the other. The resulting current may provide a collective signature of nonlinear Breit-Wheeler, while the spatial separation resulting from the relative motion may facilitate isolation of positrons for subsequent applications or detection. Published by the American Physical Society 2024

Wake-induced torsional oscillation of two tethered cylinders for energy harvesting

When two cylinders submerged in a uniform flow are arranged in tandem, the downstream cylinder can oscillate in response to the wake from the upstream cylinder. In this investigation, the downstream cylinder is allowed to oscillate freely around the center of a fixed upstream cylinder, mimicking a pendulum-like motion. Our findings suggest that the wake stiffness concept, initially verified for relatively large cylinder spacing (ℓ≥4) and linear transverse cylinder motion, is also relevant for characterizing the wake-induced vibration (WIV) response observed for two tandem tethered cylinders situated in close proximity (2≤ℓ≤4) for Reynolds numbers in the range 1.0×104≲Re≲1.2×105, with tests conducted up to Re≈1.4×105. For small cylinder spacing (ℓ≤2.5), the downstream cylinder attains a maximum oscillation angle amplitude and exhibits consistent vibration, providing reliable potential for energy harvesting. We also explore hysteresis in the WIV response, which is observed to depend on the history of Reynolds number variation. Our findings reveal hysteresis at both the onset and termination of oscillation.

Study on the motion characteristics of bedload sediment particles under different sediment transport intensities

AbstractBedload studies at the particle scale may help grasp the essence of the problem. Existing studies suffer from short filming durations, limited data volume, and a narrow range of sediment transport intensity variations. This paper employs the high‐speed photography technology and conducts experimental studies on bedload particle motion under 8 different sediment transport intensities. Using the latest image processing technology, over 6 million sediment particle coordinate points and nearly 400,000 particle motion trajectory curves were automatically obtained and used to compare the motion characteristics of bedload particles under different sediment transport intensities. The results show that under low sediment transport intensity, both the number of moving particles and particle motion velocity contribute to the bedload sediment transport rate, while under high‐intensity conditions, the transport rate mainly depends on the number of moving particles. The probability density distribution of sediment transport rate is concentrated and varies within a small range under low‐intensity conditions, exhibiting a tailing phenomenon. In contrast, under high‐intensity conditions, the range of sediment transport rate values increases, and the probability density curve tends to be symmetric, more closely approximating a normal distribution. Additionally, the paper compares the longitudinal and transverse motion velocities of particles and the coefficient of variation of the bedload sediment transport rate.

Mixed (regular and chaotic) dynamics under the channeling of the high energy positrons in [100] direction of the silicon crystal and Podolskiy-Narimanov distribution

The character of motion (regular or chaotic) on the quantum level manifests itself in the statistics of the set of the system's energy levels. The completely regular case generates the sequence of the levels with exponential (Poisson) level spacing distribution; the completely chaotic one — with Wigner distribution. The most interesting case is the co-existence of the regular and chaotic motion domains in the phase space of the system under consideration. The assumption of independent generation of two level sequencies by one chaotic domain and by all regular domains leads to Berry-Robnik distribution. However, the presence of the chaotic motion domain in the phase space affects the levels produced by the regular domains via the so-called chaos-assisted tunneling (CAT) that leads to Podolskiy-Narimanov distribution of the level spacings. This distribution needs the mean amplitude of the tunnel transition and the relative contribution of the regular domains to the mean level density as the parameters. Using their estimations for the transverse motion of the high energy positrons channeling near [100] direction in the silicon crystal we found that Podolskiy-Narimanov distribution demonstrates the best agreement with the level spacing distribution.

Dynamical chaos and level splitting under the channeling of the high energy positrons in [100] direction of the silicon crystal

The motion of charged particles in a crystal in the axial channeling regime can be both regular and chaotic. The chaos in quantum case manifests itself in the statistical properties of the energy levels set. These properties have been studied previously for the electrons channeling along [110] direction of the silicon crystal, in the case when the classical motion was completely chaotic, as well as for the ones channeling along [100] direction, when the classical motion can be both regular and chaotic for the same energy depending on the initial conditions. Here we study the positrons channeling in [100] direction. This case is of special interest due to the substantial tunneling probability between dynamically isolated regular motion domains in the phase space. The interaction of the energy levels via tunneling distinctly changes the level spacing statistics. All transverse motion energy levels as well as corresponding stationary wave functions are computed numerically for the 30 GeV positrons channeling in [100] direction of the silicon crystal. The values of the matrix elements for the tunnel transitions areextractedfrom these data. These results confirm the chaos assistance for the tunneling and the level splitting. These values will be used in the further researches of the quantum chaos manifestations in the channeling phenomenon.

A weakly nonlinear Love hypothesis for longitudinal waves in elastic rods

When investigating nonlinear wave propagation in slender hyperelastic rods, the usual stance is to construct a reduced kinematics and then derive a system of coupled nonlinear PDEs for the unknown functions. To make further analytical progress, the linear Love hypothesis, that connects longitudinal and transversal strain, is often reverted to. The viability of this assumption, that was originally proposed within the framework of linear elasticity, remains uncertain. In this paper, a refined Love hypothesis is derived in the weakly nonlinear regime by slow-time perturbation of the motion equations. For the sake of illustration, the simplest two-modal setting is adopted. This refined Love assumption is not equivalent, not even in principle, to that derived by Porubov and Samsonov (1993) by accommodating for the free boundary conditions at the rod mantle. Besides, the perturbation process lends a uni-dimensional model equation which parallels that obtained by Ostrovskii and Sutin (1977) with the help of the linear Love hypothesis, with yet different coefficients in the dispersive term. The corresponding longitudinal motion is compared numerically against the solution of the bimodal nonlinear system and the transversal motion is contrasted with the linear Love hypothesis. For both motions, excellent agreement is found and the quality of the approximation extends to a wide range of values for the small parameter. Finally, within this setting, the corresponding unimodal Lagrangian is also derived, and it remains accurate regardless of the first correction terms to the linear Love hypothesis.

Sagittal and transverse ankle angle coupling can influence prosthetic socket transverse plane moments.

The intact foot and ankle comprise a complex set of joints that allow rotation in multiple planes of motion. Some of these motions are coupled, meaning rotation in one plane induces motion in another. One such coupling is between the sagittal and transverse planes. For every step, plantar- and dorsi-flexion motion is coupled with external and internal rotation of the shank relative to the foot, respectively. There is no prosthetic foot available for prescription that mimics this natural coupling. The purpose of this study was to determine if a sagittal:transverse ankle angle coupling ratio exists that minimizes the peak transverse plane moment during prosthetic limb stance. A novel, torsionally active prosthesis (TAP) was used to couple sagittal and transverse plane motions using a 60-watt motor. An embedded controller generated transverse plane rotation trajectories proportional to sagittal plane ankle angles corresponding to sagittal:transverse coupling ratios of 1:0 (rigid coupling analogous to the standard-of-care), 6:1, 4:1, 3:1, and 2:1. Individuals with unilateral transtibial amputation were block randomized to walk in a straight line and in both directions around a 2 m circle at their self-selected speed with the TAP set at randomized coupling ratios. The primary outcome was the peak transverse plane moment, normalized to body mass, during prosthetic limb stance. Secondary outcomes included gait biomechanic metrics and a measure of satisfaction. Eleven individuals with unilateral transtibial amputations participated in the study. The 6:1 coupling ratio resulted in reduced peak transverse plane moments in pairwise comparisons with 3:1 and 2:1 coupling ratios while walking in a straight line and with the prosthesis on the outside of the circle (p < .05). Coupling ratio had no effect on gait biomechanic metrics or satisfaction. The general pattern of results suggests a quadratic relationship between the peak transverse plane moment and coupling ratio with a minimum at the 6:1 coupling ratio. The coupling ratio did not appear to adversely affect propulsion or body support. Subjects indicated they found all coupling ratios to be comfortable. While a mechatronic prosthesis like the TAP may have limited commercial potential, our future work includes testing a robust, passive prosthetic foot with a fixed coupling ratio.

Collisions of Light Bullets with Different Circular Polarizations

Collisions of left- and right-polarized spatiotemporal optical solitons have been numerically simulated for a locally isotropic focusing Kerr medium with anomalous chromatic dispersion. The stable propagation of such “light bullets” in a moderate nonlinear regime is ensured by a transverse parabolic profile of the refraction index in a multimode waveguide. The transverse motion of centers of mass of wave packets in such systems occurs on classical trajectories of a harmonic oscillator, whereas the motion in the longitudinal direction is uniform. Therefore, collisions of two solitons can be not only head-on but also tangential. An inelastic collision of two solitons with opposite circular polarizations can result either in two binary light bullets combining the left and right polarization or in more complex bound systems.

Are winter conditions impacting annual organic production in the northern Adriatic? Verifications and future projections

Primary production in the northern Adriatic (NAd) reaches its yearly peak in the winter with high-intensity variations from year to year. According to the hypothesis, the intensity of local winter primary production, controlled by the degree of the spreading of Po River waters across the NAd, reflects on the annual secondary production of the ongoing year. The hypothesis is evaluated here based on the new data set and extends from 2018 to 2020, referring additionally to 2017 data which are already published. Data collected in 2017 and 2020 support the hypothesis, pointing to the large organic outputs after highly productive winters. Despite the lack of seasonal data for 2018 and 2019, large annual production was deducted by large abundances of the allochthonous gelatinous zooplankton species – Mnemiopsis leidyi. Numerical models show that in 2018–2020 the NAd was mostly “separated” from the rest of the Adriatic Sea by a northern branch of a large cyclonic gyre with high salinity water (from central Adriatic and/or Kvarner Bay) entering the NAd along the eastern (Istrian) coast. Such a circulation system could favour the spreading of the Po River waters across the NAd, inducing high primary production in winter, at the beginning of the yearly pelagic cycle, with a subsequent retention/accumulation of organic matter produced in the following months in the area. Using climate projections of temperature and salinity and the associated circulation and following the observed biological relations, a prediction of the organic matter production in the NAd can be obtained. With increased horizontal density gradients in future winters, an intensification of transversal motions across the NAd is expected. Thus, the retention of the Po waters with higher winter production in the NAd may be predicted. Following the hypothesis, a higher annual organic production and a probable higher occurrence of gelatinous plankton in the east of the NAd are expected.

Investigation into the Uniformization of Proton Beams for FLASH Therapy

FLASH proton therapy is widely considered in many labs. However, achieving a dose rate sufficient for FLASH is challenging, especially when using the scanning method. A beam uniformization process using a nonlinear magnet is employed to reduce the scanning time, supplemented by multi-energy extraction to enhance the dose rate. The impact of octupole fields, multipole field components, and step field on the transport line are tested. The nonlinear effect of the magnetic fields on the transverse motion of the particle beam is used to establish a uniform dose distribution at the target. Different schemes are investigated and the octupole approach was finally selected.

Experimental realization of entangled coherent states in two-dimensional harmonic oscillators of a trapped ion

Entangled coherent states play pivotal roles in various fields such as quantum computation, quantum communication, and quantum sensing. We experimentally demonstrate the generation of entangled coherent states with the two-dimensional motion of a trapped ion system. Using Raman transitions with appropriate detunings, we simultaneously drive the red and blue sidebands of the two transverse axes of a single trapped ion and observe multi-periodic entanglement and disentanglement of its spin and two-dimensional motion. Then, by measuring the spin state, we herald entangled coherent states of the transverse motions of the trapped ion and observe the corresponding modulation in the parity of the phonon distribution of one of the harmonic oscillators. Lastly, we trap two ions in a linear chain and realize Mølmer–Sørensen gate using two-dimensional motion.

Effect of sensor location for modifying center of pressure during gait using haptic feedback in people with chronic ankle instability

BackgroundGait retraining using haptic biofeedback medially shifts the center of pressure (COP) while walking in orthopedic populations. However, the ideal sensor location needed to effectively shift COP medially has not been identified in people with chronic ankle instability (CAI). Research questionsCan a heel sensor location feasibly be employed in people with CAI without negatively altering kinematics? Does a heel sensor placement relative to the 5th metatarsal head (5MH) impact COP location while walking in people with CAI? MethodsIn this exploratory crossover study, 10 participants with CAI walked on a treadmill with vibration feedback for 10 minutes with a plantar pressure sensor under the heel and 5MH. Separate 2×2 repeated measures analyses of covariances (rmANCOVAs) were used to compare the averaged COP location and 3-D lower extremity kinematics from the first 10% of stance before and after training and between sensor locations. Baseline measures served as covariates to adjust for baseline differences. ResultsFeedback triggered by a heel sensor resulted in 40% of participants avoiding a heel strike. There were no significant main effects or interactions between time and sensor location on COP location when controlling for baseline COP (p>0.05). However, with the 5MH placement, participants displayed less ankle internal rotation(IR) (5MH/Heel: −4.12±0.00º/ −6.43±0.62º), less forefoot abduction (-4.29±0.00º/ −5.14±1.01º), more knee flexion (3.40±0.32º/ 0.14±0.57º), less knee external rotation (-10.95±0.00º/-11.24±1.48º), less hip extension (-0.20±0.00º/-1.42±1.05º), and less hip external rotation (3.12±0.00º/3.75±1.98º). SignificanceA 5MH location may be more feasible based on difficulties maintaining heel strike when the sensor was under the heel. While no sensor location was statistically better at changing the COP, the 5MH location decreased proximal transverse plane motions making participants’ gait more like controls. Individual response variations support comprehensive lower extremity assessments and the need to identify responder profiles using sensory feedback in people with CAI.

Heat transport in an angular-momentum-conserving lattice.

It is expected that the energy-diffusion propagator in a one-dimensional nonlinear lattice with three conserved quantities: energy, momentum, and stretch, consists of a central heat mode and two sound modes. The heat mode follows a Lévy distribution. Consequently, the heat diffusion is super, i.e., the second moment of the diffusion propagator diverges as t^{β} with β>1; and the heat conduction is anomalous, i.e., the heat conductivity is size dependent and diverges with size N by N^{α}, with α>0. In this paper, we study a one-dimensional lattice with two-dimensional transverse motions, in which the total angular momentum also conserves. More importantly, the diffusion of this conserved quantity is ballistic. Surprisingly, the above pictures and the values of the mentioned power exponents keep unchanged. The universality of the scalings is then further extended. On the other hand, the detailed strengths of heat transports are largely enhanced. Such a counterintuitive finding can be explained by the change of the phonon mean-free path of the lattices.

Acoustic-driven magnetic skyrmion motion.

Magnetic skyrmions have great potential for developing novel spintronic devices. The electrical manipulation of skyrmions has mainly relied on current-induced spin-orbit torques. Recently, it was suggested that the skyrmions could be more efficiently manipulated by surface acoustic waves (SAWs), an elastic wave that can couple with magnetic moment via the magnetoelastic effect. Here, by designing on-chip piezoelectric transducers that produce propagating SAW pulses, we experimentally demonstrate the directional motion of Néel-type skyrmions in Ta/CoFeB/MgO/Ta multilayers. We find that the shear horizontal wave effectively drives the motion of skyrmions, whereas the elastic wave with longitudinal and shear vertical displacements (Rayleigh wave) cannot produce the motion of skyrmions. A longitudinal motion along the SAW propagation direction and a transverse motion due to topological charge are simultaneously observed and further confirmed by our micromagnetic simulations. This work demonstrates that acoustic waves could be another promising approach for manipulating skyrmions, which could offer new opportunities for ultra-low power skyrmionics.

MHD modelling of coronal streamers and their oscillations

Context. The present work investigates solar coronal dynamics in particular streamer waves. Streamer waves are transverse oscillations of the streamer stalk, often generated by the passage of a coronal mass ejection (CME). Recent observational studies infer that the streamer wave is an eigenmode of the streamer plasma slab and an excellent candidate for coronal seismology. Aims. In the present work, we aim to numerically investigate the theoretical concepts of the physics and properties of streamer waves and to complement the observational statistical analysis of these events. Methods. We used the magnetohydrodynamics (MHD) module of MPI-AMRVAC. An adaptive mesh refinement scheme was employed to achieve high resolution for the streamer structure. All the simulations were computed on the same base grid with the same numerical methods. We considered a dipole magnetic field on the Sun and a uniformly accelerating solar wind. We introduced a θ-velocity perturbation within our computational domain in the plane of a streamer to excite the transverse motion. Results. A numerical model for the streamer wave phenomena was constructed in the framework of 2.5D MHD. We performed a parameter study and identified a sensitivity of the streamer dynamics to the background solar wind speed, the characteristics of the perturbation, and the input parameters for the model, such as temperature and magnetic field. We performed a statistical analysis and compared the obtained modelling results with the database of such events from observations from three different coronagraphs. We observed a narrow range of phase speeds and a correlation between wavelength and period. This is consistent with the observations and supports the idea that the streamer wave is an eigenmode of the streamer plasma slab. The measured phase speed is consistently significantly higher than the speed calculated from the measured period and wavelength. The simple fit, when the difference between these two speeds is exactly the background solar wind speed, only matches a small fraction of the data. The obtained results indicate that further investigation is required into the Doppler shift effect in the MHD theory for coronal seismology.

Nonlinear free vibrational behavior of temperature-dependent two-directional functionally graded truncated cone-like shells in thermal environment

This article investigates nonlinear free vibrations of temperature-dependent two-directional functionally graded (TDTDFG) cone-like shells in thermal environment. The structure material is a combination of ceramic and metal with temperature-dependent mechanical characteristics varying continuously in the thickness and longitudinal directions. Initially, the thermomechanical dynamic equations of the system are modeled based on the first-order shear deformation theory (FSDT) and the strain-displacement relations of von Kármán. Afterward, the final governing equation for the structure’s transverse motion is obtained using the Galerkin discretization method. Finally, the governing equation is solved using improved Lindstedt-Poincaré method as an analytical technique, resulting in an equation for calculating the nonlinear frequencies of the shell. To validate the research’s results, the system frequencies are calculated under different conditions and compared with the results of previous studies. After ensuring the accuracy of the results, a parametric study is performed to evaluate the effects of various parameters on the linear and nonlinear frequencies of the TDTDFG cone-like shell in thermal environment. The results of this study have demonstrated that gradient indices, geometric ratios, and thermal environment have a significant influence on the nonlinear vibration behavior of structures.

Non-stationary quasi-classical states of a charged particle in a strong magnetic field under conditions of the dissipative medium

Based on the quasi-classical approximation, a general approach is proposed for constructing non-stationary quantum states of a charged particle in a magnetic field, when the dissipative forces of viscous friction and drag, proportional to the velocity and the square of the velocity, respectively, are also significant. The corresponding quasi-classical Green’s function is found, with the help of which the squeezed and coherent states of the particle are studied. It is shown that the dissipation and a magnetic field suppress the quantum properties of the particle. This is especially true for the transverse motion with respect to the magnetic field. Over time, the coherent and squeezed states transform into the same static state, which is characterized by a zero uncertainty of the transverse coordinates and an uncertainty of the longitudinal coordinate, which contains information about the initial velocity of the particle.

Passive Control in a Continuous Beam under a Traveling Heavy Mass: Dynamic Response and Experimental Verification.

The motion of a heavy mass on a bridge span causes vibrations whose magnitude and frequency content depend on the mechanical properties of the structural system, including the magnitude of that mass and its speed of traverse. In order to limit vibrations that could potentially cause damage, a simple passive device configuration, namely the tuned mass damper (TMD), is introduced and its effect on the beam vibrations analyzed. Specifically, a TMD in the form of a single-degree-of-freedom (SDOF) unit comprising a mass and a spring is placed on the span to act as a secondary system for absorbing vibrations from the primary system, i.e., the bridge itself. A Lagrangian energy balance formulation is used to derive the governing equations of motion, followed by an analytical solution using the Laplace transform to investigate the transmission of vibratory energy between primary and secondary systems. Results are given in terms of time histories, Fourier spectra and spectrograms, where the influence of the TMD in reducing vibratory energy is demonstrated. The TMD is placed in the region where the beam's transverse motion is at a maximum, while its mechanical properties are sub-optimal, in the sense that there is no separate damper present and minimal damping is provided by the spring element itself. In parallel with the analysis, a series of experiments involving a simply supported model steel bridge span traversed by a heavy mass are conducted to first gauge the analytical solution and then to confirm the validity of the proposed passive scheme.

Navigating vortex gust interactions and mitigations by plunging wings

Inspired by the stability achieved by biological flapping-winged fliers in gusty environments, we conducted particle image velocimetry studies on the interactions between plunging wings and large-scale vortex gusts. Our experiments involved a flat plate wing performing sinusoidal plunging motions at various frequencies, resulting in Strouhal numbers (St) ranging from 0 to 0.5 within which biological fliers commonly operate. This range of St corresponded to reduced frequencies (k) between 0 and 0.79 at a chord Reynolds number of 2000. The gust structures, generated periodically by pitching vanes, traveled downstream to the wing. We observed the vortex interactions between wing-induced vortices [particularly the boundary layer and the leading-edge vortex (LEV)] and the gusts. Additionally, we quantified the gusts' effects on the local flow around the wing by calculating the circulation within a control region attached to the plunging wing. The wing-induced vorticity merged momentarily with gusts of the same-sign vorticity. In contrast, opposite-sign gusts not only increased the circulation of the wing-induced vortices but also led to the LEV detaching faster. While gusts had the potential to significantly alter the flow around the wings, the plunging wings sometimes managed to avoid the gusts due to their transverse motion. Furthermore, the prolonged presence of the stronger LEVs near the wing, which are characteristic of plunging wings at higher St and k, could deflect the gusts away, reducing their impact on the vorticity and circulation within the control region. These findings illustrate how robust flapping kinematics can mitigate the effects of vortex gusts.