Duration Of Motion Research Articles

Optimizing continuous passive motion duration following arthroscopic release of elbow contracture: a retrospective study.

The anatomical structure of the elbow joint makes it vulnerable to contractures. While elbow arthroscopy minimizes soft tissue damage and enhances early rehabilitation, the optimal duration for postoperative Continuous Passive Motion (CPM) therapy is unclear. This retrospective study aims to establish the appropriate duration of CPM following arthroscopic elbow contracture release. We analyzed postoperative outcomes from patients undergoing CPM rehabilitation for 1, 3, or 5 months. Metrics such as ASES, VAS, DASH, MEPS scores, grip strength, and range of motion were assessed before surgery and at 1,3,6 and 12 months post-surgery. Patients who received 3 or 5 months of CPM therapy showed statistically significant improvements in elbow flexion-extension, range of motion, and functional scores (ASES, VAS, DASH, MEPS) compared to the 1-month group (p < 0.05). However, no significant differences were observed between the 3- and 5-month groups. A 3-month CPM period is effective for patients with higher functional demands, with no additional benefit from extending therapy to 5 months.

Research on the Motion of Few Tooth Magnetic Gears with Given Initial Angular Velocity Based on Euler Method

Abstract This paper aims to investigate the motion patterns of magnetically interacting gears with a few teeth and given initial angular velocities. Based on Ampere’s molecular current hypothesis, an equivalent current model is utilized to solve the magnetic field generated by cylindrical permanent magnets. Comsol software is employed to simulate the distribution of the magnetic field, demonstrating that the magnetic field calculated by the equivalent current model is in good agreement with the actual situation. Vector analysis, field theory, and the symmetry of the magnetic field distribution are leveraged to simplify the calculations, thereby reducing the runtime of the program. The Euler method is adopted to numerically simulate the motion of the gears. Finally, a comparison with experiments shows that the motion patterns in the experiments are essentially consistent with those in the numerical simulations. It is concluded that the ratio of magnetic field intensity to resistance torque, initial magnetic potential energy, and initial angular velocity positively correlate with the motion duration; the ratio of magnetic field intensity to resistance torque and initial magnetic potential energy positively correlate with the intensity of motion; when the initial angular velocity is excessively high, the other gear exhibits slight vibrations in its original position, and only when the initial velocity decreases to a certain value do the two gears interact significantly.

Kinematic rupture modeling of broadband ground motion from the 2022 MS6.9 Menyuan earthquake

AbstractWe propose a novel kinematic rupture modeling procedure for synthesizing broadband ground motions derived from the frequency-wavenumber integration algorithm. This procedure addresses two key issues in characterizing the rupture processes relevant to broadband seismic radiation: an accurate Green's function and a well-constrained kinematic source model. For the first issue, we derive the theoretical Green's function based on an improved dynamic stiffness matrix approach that effectively handles wave propagation in a 1D crustal velocity structure across a broad frequency band. For the second issue, we generate the hybrid source model that combines asperity slip and random slip over the fault plane to effectively implement constraints on the radiated energy during the whole rupture process. The accuracy and effectiveness of the proposed methodology are verified by comparing with the surface acceleration traces and Fourier spectra calculated by spectral element method. With the hybrid source model and crustal velocity structure applicable to the target area, the broadband (0–10 Hz) ground motion of the 2022 MS6.9 Menyuan earthquake is synthesized. The amplitude, duration, and frequency content of the synthetic motions are systematically compared with those of the available observed records and ground motion attenuation relationships, as well as the spatial distribution characteristics of the near-field ground motions from the earthquake scenarios are presented. In conclusion, the case study of the Menyuan MS6.9 earthquake demonstrates that the presented modeling procedure can estimate broadband ground motions rapidly and reliably from a physics-based kinematic rupture perspective.

Dynamical maps for accelerating detectors

We study the open quantum dynamics using the language of dynamical maps of a two-level particle detector that starts accelerating through Minkowski vacuum weakly coupled to a massless scalar field. We consider a detector with non-zero size and study its time evolution for the case where it is initially in inertial motion and subsequently a constant acceleration is switched on for a finite time. We study the dynamical maps that describe the evolution of such a system and show that the dynamics is not completely positive (NCP). The inertial motion prior to the acceleration can entangle the detector and field leading to the NCP dynamics. We examine the nature of the open dynamics during the accelerated phase as a function of the duration of prior inertial motion and the magnitude of the acceleration.

Comprehensive ground-motion characterization of the 6 February 2023 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\\varvec{M}}_{\\varvec{W}}$$\\end{document} 7.8 Pazarcık earthquake in Kahramanmaraş, Türkiye: insights into attenuation effects, site responses and source properties

The devastating \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{M}_{W}$$\\end{document} 7.8 Pazarcık earthquake on February 6, 2023, profoundly impacted a large region in south-central Türkiye and northwestern Syria, resulting in over 50,000 casualties and widespread damage. To better understand source properties and wave-propagation effects of this event, we analyze the strong ground-motion data recorded at ~ 230 stations. We determine the regional distance-dependent attenuation using the horizontal RotD50 Fourier acceleration amplitude spectrum (FAS) in the frequency range of 0.1–20 Hz. We find an apparent near-source saturation effect which needs to incorporate an additional finite-fault factor for the distance scaling. Uncertainty and sensitivity analyses are considered by variable decay rates in the geometric spreading model. For each decay rate, we derive a corresponding \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:Q\\left(f\\right)$$\\end{document} model to account for the frequency-dependent anelastic attention. Significant duration of ground motions is modelled for two different measurements based on Arias intensity (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{I}_{A}$$\\end{document}). For site amplification, we construct a model containing both \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{V}_{S30}$$\\end{document}-scaling and peak ground acceleration (PGA)-scaling. Source parameters are then determined using a reference Fourier source spectrum at 1.0 km. Specifically, we estimate the mean corner-frequency as \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{f}_{0}$$\\end{document}= 0.036 Hz, Brune stress drop as Δσ = 4.79 MPa and the reference rock site κ0 = 0.051 s. By analyzing near-source pulse-like waveforms, we demonstrate that the mismatch of peak ground velocity (PGV) between our model and close-distance observations is due to the rupture directivity effect. Finally, we compare ground motions of the 2023 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{M}_{W}$$\\end{document} 7.8 event to those of the 2023 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{M}_{W}$$\\end{document} 7.6 Elbistan and the 2020 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{M}_{W}$$\\end{document} 6.7 Sivrice earthquakes. Attenuation effects estimated for the three events are found to be identical between ~ 0.2 and 6.0 Hz, with slight differences in site responses above ~ 5.0 Hz. Source spectra comparisons indicate that the source properties are complicated for all three events. Our comprehensive ground-motion analyses contribute to understanding and modeling regional properties of attenuation, site response, and event-based source characteristics that are important for future region-specific seismic hazard assessment.

Dealing with rectum motion during radiotherapy: How can we anticipate it?

IntroductionIntra- and inter-fraction rectum motion is important for pelvic radiotherapy (RT). This study assesses how RT session duration, the presence or the absence of an intra-rectal tumour, and the distance from the anorectal junction (ARJd) impact rectal motion. Materials and methodsAnalyses used cone-beam computed tomographies (CBCTs) from RT patients treated for rectal and prostate cancer. Three structures were evaluated: (1) the entire rectum in patients without a rectal tumour (RectumProstate); (2) the non-invaded portion (RectumRectum) and (3) the tumour-invaded portion (RectumTumour) in rectal cancer patients.Intrafraction motion was assessed using the Hausdorff distance 95% and the Mean distance-to-agreement between structures delineated on the first CBCT and the 2 subsequent CBCTs within a same RT session. Interfraction motion was quantified by comparing structures delineated on the planning-CT and the first CBCT of each session.Linear mixed model evaluated rectum motion in relation to time, tumour presence, and ARJd, respectively. ResultsWe included 10 patients with and 10 without rectal cancer, collecting 385 CBCTs. A significant correlation (p < 0.05) between rectum motion and RT session duration was found. Intrafraction motion was significantly higher in prostate cancer patients (RectumProstate motion > RectumRectum and RectumTumour, p < 0.01). For interfraction motion, only the mean distance to agreement was significantly higher for RectumProstate (p < 0.05). Motion increased significantly with ARJd for all three structures (p < 0.001). ConclusionsSession duration, absence of a tumour, and ARJd are associated with larger intra- and interfraction rectal motion. This highlights the need for tailored RT treatment, including online-adaptive RT, to manage intra- and interfraction variations. Rectal motion should be handled differently for patients with prostate cancer and those with rectal cancer.

Optimization study of tail-lateral occupant injury and restraint system for an off-road vehicle ramp rollover

The process of rollover accidents involving specialized vehicles is characterized by intense motion and long duration. Although these accidents are infrequent, they often lead to a high fatality rate. In this study, we utilized LS-Dyna software to simulate the rollover of a vehicle on a side ramp. This simulation aimed to verify the reliability of our model establishment by comparing the vehicle’s motion attitude and center-of-mass acceleration with experimental results. Additionally, we sought to investigate the lateral occupant injuries that occur in the tail section of a certain type of specialized vehicle during a rollover. Initially, we obtained the vehicle’s motion trajectory and the dummy’s motion state through simulation. Subsequently, we extracted the injury response of each part of the dummy. We then simplified the entire vehicle model and made improvements to the occupant restraint system, ultimately designing an enhanced system. Finally, we approximated and replaced the entire vehicle model by establishing an approximation model. We combined this with an optimization algorithm to optimize the occupant restraint system. The simulation results demonstrate that the improved occupant restraint system significantly reduces the axial force on the neck of the occupant and the comprehensive evaluation index of injury. Furthermore, the simulation results for each component fall below the injury limit value specified in the FMVSS208 crash occupant protection standard. Therefore, the improved occupant restraint system proposed in this study effectively mitigates lateral occupant injury during rollover accidents.

Comparison of dental force applied during endotracheal intubation with hyper-angulated and macintosh-type video laryngoscopy blades used by emergency medicine trainees: A randomized cross-over manikin study.

This study aimed to compare the effects of Macintosh-type and hyperangulated video laryngoscopy (VL) blades on dental force during endotracheal intubation (ETI) using Glidescope and McGrath VL devices. In this randomized, crossover, manikin study conducted at a university emergency medicine (EM) program, 65 EM trainees included interns and residents performed 520 intubations using four different VL blades (GlideScope VL with Macintosh-type Mac T3 and hyperangular Lo Pro T3 blades and McGrath VL Macintosh-type MAC 4 and hyperangular McGrath X3 blades) in normal and difficult airway scenarios. The primary outcome of this study was the dental pressure (Newton) exerted during ETI. The secondary outcomes included c-spine motion (degree), intubation success (%), duration (seconds), successful glottic view (%), and intubator comfort (7-point Likert). Significant differences were observed in dental force (H(3) = 11.7, P = 0.008), c-spine motion (H(3) = 8.34, P = 0.039), duration (H(3) = 16.56, P = 0.001), and comfort (H(3) = 174.96, P < 0.001) across blade types. Glidescope LoPro T3 provided a significant lower dental force (adjusted P = 0.01), less c-spine motion (adjusted P = 0.031), and shorter intubation duration (adj P < 0.01) than the McGrath Mac 4. First attempt success and intubator comfort were significantly better with all Glidescope blades (z score of 3.7 and 4.7) than with McGrath blades (z score of-4.1 and-4.4). The Glidescope LoPro T3 blade demonstrated advantages in dental force, c-spine motion, and intubation duration compared with McGrath Mac 4. Overall, the Glidescope blades provided superior comfort and higher first attempt success rates.

Generation of spectrum compatible ground motions considering duration

The seismic inputs hold utmost significance in the aspect of conducting response history analysis on city infrastructures. However, the selection of recorded ground motions matching the desired scenarios from past earthquakes within a specific region presents a significant challenge. To address this challenge, a novel approach is introduced in this study, which proposes a ground motion generation method that ensures compatibility with the target spectrum while also considering ground motion duration. The methodology commences by employing the principal component analysis algorithm to extract orthogonal bases from ground motions derived from recorded earthquakes. These orthogonal bases are subsequently combined and modified using a multi-objective algorithm and tapered cosine wavelet. Four earthquake scenarios are examined to validate the reliability of the proposed method. It is concluded that this novel approach offers a solution to the complex task of selecting appropriate ground motions for conducting nonlinear time-history analyses.

Probabilistic seismic demand of typical highway bridges in moderate-intensity zones

The probabilistic seismic demand for typical highway bridges in moderate-intensity zones is investigated. The seismic demands and infrastructure destructions are severe on critical bridge components during and after seismic activity in moderate-intensity zones. This article aims to determine seismic demand, predict the probabilistic seismic demand model (PSDM), and identify the interdependence of bridge components. Based on bin-ground motion, 154 analytical bridge-ground motion samples are prepared to record output data using nonlinear time history analysis (NLTHA). High-level ground motion duration and peak ground acceleration are used to measure the seismic demand and intensity of the bridge. The best-fitting lognormal distribution and correlation coefficient between demand in the transformation states are analysed to indicate the interaction between the two at dissimilar levels of interdependence. As a result, bearing pads on all abutments, the bearing pad on pier-1, and the shear key on pier-2 are best fitted with a high level of interdependence to design the seismic performance of highway bridges. Therefore, the ground motion characteristics play a vital role in the infrastructure collapse of the highway bridges in the moderate-intensity zone and should be held in high regard.

Error analysis of asymptotic solution of a heavy particle motion equation in fluid flows

For weakly inertial particles subjected to volumetric forces and Stokes drag force in fluid flows, we can solve the simplified particle motion equation using the perturbation method. This method allows us to obtain a recursive formula for the nth-order correction of the asymptotic solution of particle velocity. We verified the error of the asymptotic solution under two typical flow fields: a time-varying uniform flow field with a volumetric force field and a two-dimensional non-uniform cellular flow field. In the former, the relative error of the asymptotic solution of particle velocity and position increases with the Stokes number, and we provided a quantitative analysis of the results. In the latter, we verify and analyze the asymptotic solution from two perspectives: the behavior of a single particle and the collective behaviors of many particles. For asymptotic solutions with maximum velocity and position errors of less than 5%, we select the solution with the lowest order correction and designate it as the optimal asymptotic solution. The order of the optimal asymptotic solution increases with increasing Stokes numbers and motion durations. However, in most cases, for weakly inertial particles [St ∼ O(10−3)], and the time t* ∼ O(10), the first-order asymptotic solution can achieve accuracy, where both St and t* are defined using the flow field characteristic time, Tf = 4π s. The results validate the rationale behind utilizing first-order asymptotic solutions in the fast Eulerian method for turbulent dispersion of weakly inertial particles.

Influence of ground motion characteristics on the heating effect of lead‐rubber bearings in base‐isolated structures

AbstractUnder earthquake excitations, the lead core inside the lead‐rubber bearing (LRB) generates heat, causing the mechanical degradation of LRBs. However, the heating effect is not commonly considered in the seismic analysis and design of base‐isolated structures with LRBs, which may underestimate the seismic response of structures, especially under ground motions with certain specific characteristics. This paper aims to reveal the influence of ground motion characteristics on the heating effect and provide useful references for the seismic analysis and design. In this study, the validated LRB model considering heating effect was employed in a base‐isolated building calibrated by testing data. Ground motion characteristics including amplitude, duration, and frequency content were separated by spectrally equivalent and different records. The results indicate that the rate and peak of the lead core temperature rise are strongly correlated to ground motion characteristics. Seismic responses ignoring the heating effect are underestimated, and this underestimate varies as the amplitude, duration, and frequency content change and reaches up to 60% in the studied case. Note that seismic responses of the isolation system are more affected by heating effects than the superstructure, and the duration shows a more significant influence on the stiffness degradation of LRBs than the frequency content. It is strongly recommended that the required duration of ground motions should be raised and the low stories of the superstructure should be reinforced for isolated structures with LRBs. The significant duration indicator DS5–95 is more reasonable than DS5–75 in the analysis of the heating effect.

Seismic hazard study for the duration of ground-motions triggered by intraslab earthquakes

This paper presents a probabilistic seismic hazard analysis for the duration of ground motions in Mexico City caused by intraslab earthquakes. The study implies establishing criteria to measure the duration of ground motions and developing predictive equations (GMPEs) for its estimation. Focus is placed on the relative significant duration, DSr\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{Sr}$$\\end{document}, which is based on the accumulation of energy of ground motions. The study extends to the development of hazard curves that allow estimating the annual probability of exceedance of said parameter. The scope is limited to ground motions caused by intraslab earthquakes occurring in Mexico and that engineeringly affect its capital, Mexico City, which is in a geographical region where the effects of soil-dynamic amplification are manifested considerably. A strong-motion database that includes 1517 horizontal accelerograms, with peak ground acceleration, PGA\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$PGA$$\\end{document}, greater than or equal to 3 cm/s2, recorded during 21 earthquakes from 1994 to 2023 were used to develop the GMPEs. The quantitative description of the time, size, and spatial distribution of the seismic-activity occurrence was defined using a catalog of 46 earthquakes that occurred from 1900 to 2023. The earthquakes have moment magnitude, Mw\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{w}$$\\end{document}, greater than or equal to 6. With the tools developed, amplitude- and duration-based hazard-consistent accelerograms can be simulated and used in nonlinear dynamic analyses (NDAs) of structures. This study includes an application example where three sites in Mexico City are selected to compute inelastic response spectra. Hysteretic-energy demands up to 5 times higher are found after a comparison between the inelastic-response spectra from hazard-consistent accelerograms and those provided by current Mexican regulations.

Explicit solutions for the ground displacement of a sliding model simulating both the frictional and rotational effects under idealized acceleration pulses

AbstractFor the first time, the present work derives explicit equations predicting the downward ground displacement of a sliding model simulating both the frictional and rotational effects under idealized acceleration pulses, in the form of simple formulas. Explicit equations allow not only accurate predictions in all cases, but also analysis of the solutions and derivation of expressions for limit cases. Half and full cycles of (i) rectangular, (ii) triangular, (iii) trapezoidal, and (iv) sinusoidal pulses and slopes both under static stability and instability are considered. For this purpose, for pulse cases (i)–(iii) recently proposed implicit analytical solutions are used, while for case (iv), first the analytical equations predicting the sliding displacement and velocity of a sinusoidal pulse in terms of time are obtained and then the time duration of motion is estimated, by using the Bhaskara approximation of the sine and cosine functions. Then, from these, solutions for the particular limit cases corresponding to the “conventional” sliding‐block model (Case A) and the post‐failure run‐off movement without any applied pulse (Case B) are derived. The results for Case A provide a useful tabulation of sliding‐block solutions, some of which are not reported in the literature. The results for Case B provide novel predictions of the time duration of motion in the case of post‐failure movement. The general solutions are analyzed graphically and the deviation from the solutions of Cases A and B is illustrated. Finally, the explicit solutions are compared to solutions of actual accelerograms.

Assessing the Impact of Ground Motion Duration on Losses in Typical Modern Steel Moment Frames

This research was undertaken to study the duration effects on the seismic economic risk of steel moment frame (SMF) buildings, a prominent class of buildings in commercial stock. Firstly, a modified version of FEMA P-695 ground motion scaling, tailored for seismic loss estimation purposes and incorporating two sets of spectrally matched bi-directional short- and long-duration ground motions, is proposed to study code-compliant plan-symmetrical SMFs with different heights (i.e., two to 20 stories). It is shown that long-duration ground motions increase the collapse risk of SMFs, on average, by 28.0% at the MCE level. Next, a component-based loss estimation methodology was adopted for evaluating the seismic losses under each set of ground motions. These losses are studied separately for building components (i.e., structural and nonstructural) and contents. Moreover, we propose an approach for calculating average annualized loss (AAL) as a prominent risk meter that segregates contributions of short- and long-duration ground motions to attain hazard consistency. Loss analyses showed the minimal impact of building height on the contribution of these two types of earthquakes. The seismic risk analysis of buildings also revealed that collapse risk is influenced mainly by duration effects followed by building and content losses.

Explainable XGBoost–SHAP Machine-Learning Model for Prediction of Ground Motion Duration in New Zealand

Explainable XGBoost–SHAP Machine-Learning Model for Prediction of Ground Motion Duration in New Zealand

Truncating ground motions using the VMD-Hilbert transform for nonlinear dynamic analyses

Nonlinear dynamic analyses of engineered structures under long-duration ground motions usually require significant computational time, especially when performing incremental dynamic analyses or when developing fragility curves. This study proposes a truncation method of seismic records to reduce the computation cost of nonlinear structural analyses based on the Variational Mode Decomposition and the Hilbert Transform. The truncation-starting and -ending time instants are identified using the relative cumulative spectral energy, which is used to represent the Hilbert spectrum energy variation over time. The effectiveness of the proposed method is verified by the elastic pseudo-response spectrum, three different inelastic single-degree-of-freedom models and a multi-degree-of-freedom system. The proposed method, compared with the Arias intensity-based method, proves to be effective, not only for short-period structures, but also for medium- and long-period structures, allowing for reduction of ground motion duration of about 65% on average.

Predicting slight freezing of gait in Parkinson's disease with anticipatory postural adjustments and limits of stability

IntroductionGait initiation (GI) includes automatic and voluntary movements. However, research on their impact on the first step in patients with Parkinson's disease (PD) and their relationship to freezing of gait (FOG) is lacking. We examined the effects of automatic movements (anticipatory postural adjustments [APAs]) and voluntary movements (limits of stability [LOS]) on the first step (first-step duration and first-step range of motion), along with their early recognition and prediction of slight FOG. MethodsTwenty-three patients with PD and slight freezing (PD + FOG) and 25 non-freezing patients with PD (PD-FOG) were tested while off medications and compared with 24 healthy controls (HC). All participants completed a 7-m Stand and Walk Test (7 m SAW) and wore inertial sensors to quantify the APAs and first step. LOS was quantified by dynamic posturography in different directions using a pressure platform. We compared differences among all three groups, analysed correlations, and evaluated their predictive value for slight FOG. ResultsIn PD + FOG, APAs and LOS were worse than those in the PD-FOG and HC groups (p < 0.001), and the first step was worse than that in HC (p < 0.001). APAs were correlated mainly with the first-step duration. APAs and LOS were correlated with the first-step range of motion. APAs have been recognized as independent predictors of FOG, and their combination with LOS enhances predictive sensitivity. ConclusionAPAs and LOS in patients with PD directly affect the first step during GI. In addition, the combination of APAs and LOS helped predict slight FOG.

Internal dynamics of a polaron uniformly moving along a molecular chain in a constant electric field

This paper presents a detailed study of the uniform motion of a Holstein polaron as it moves along a chain in a constant electric field. The calculations showed that, depending on the parameters of the system, the duration of the uniform motion of the polaron along the chain can reach tens and hundreds of Bloch periods for a given value of the electric field intensity. It is shown that in the process of the uniform motion, the macro-part of the polaron moves at a constant velocity, retaining its shape. At the same time, the low-density components of the polaron, which arise immediately when a constant electric field is instantaneously switched on, have their own internal dynamics and demonstrate characteristic elements of the Bloch oscillations, such as the period of Bloch oscillations and the maximum Bloch amplitude. It is shown that not only the velocity and duration of the uniform motion of the polaron, but also the characteristics of the low-density components of the polaron depend on the value of the electric field intensity.

Phantom sensation: Threshold and quality indicators of a tactile illusion of motion

Utilizing a randomized, blind, controlled experiment, and the ascending method of limits, we determined the minimum amplitude of motion at which individuals perceive a tactile illusion called moving phantom sensation, the perceived level of clarity and continuity of motion. Implementing tactile illusions in virtual/augmented reality, sensory substitution systems, and other human–computer interaction technologies results in interfaces with improved resolution, using two vibrating actuators only. The actuators are attached to the skin in different locations to render a moving phantom sensation. The intensity of vibrations increases in one actuator while decreases in the other according to the envelope of the voltage supply signals. This intensity variation creates the illusion of a vibrating point moving between the actuators. We gradually increased the amplitude of motion until the participant reported perceiving the illusion, for eight values of duration of the stimulus from 0.1 to 6.0 s. Participants perceived the illusion at a minimum amplitude of motion of 20%; being 100% the motion from one actuator to the other. The median level of clarity of the perceived illusion at the minimum amplitude of motion was 2 (not so clear). Finally, we found a positive correlation between duration and continuity of motion.