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A comprehensive physical electro-thermal modeling approach is explored to investigate the intricate mechanisms underlying filament formation and the effect of surface perturbation in nanoscale Y2O3-based memristors. The approach integrates fundamental principles of solid-state physics, electrochemistry, and materials science to develop a detailed physical model that captures the key phenomena governing the operation of Y2O3 memristors. The simulation is carried out in a semiconductor physics-based tool, i.e., COMSOL Multiphysics with a defined MATLAB script, wherein simulation is based on the minimum free energy of the used materials at an applied input voltage. The fundamental processes in filament growth include ion migration, redox reactions, and vacancy dynamics within the Y2O3 lattice. Furthermore, the influence of surface perturbation on the overall device behavior, grain boundaries, and electrode interactions impact on memristor performance is also investigated. The surface perturbations significantly influenced the switching dynamics of the memristor, including variations in switching voltages, ON/OFF current ratio, filament radius, and filament temperature during the switching process. Therefore, the presented findings contribute to a deeper understanding of the physical mechanisms at play in Y2O3 memristors, offering valuable guidance for the design and engineering of these nanoscale devices for next-generation memory and neuromorphic computing applications. This physical modeling approach not only enhances our comprehension of memristor behavior but also paves the way for the development of more efficient and reliable memristor-based technologies. [ABSTRACT FROM AUTHOR]

Background: As a strategy to maintain postural control, the stiffening strategy (agonist-antagonist co-contractions) is often considered dysfunctional and associated with poor physical capacity. The aim was to investigate whether increased stiffening is associated with unsuccessful postural control during an unpredictable surface perturbation, and which sensory and motor variables that explain postural stiffening.Methods: A sample of 34 older adults, 75.8 ± 3.8 years, was subjected to an unpredicted surface perturbation with the postural task to keep a feet-in-place strategy. The participants also completed a thorough sensory- and motor test protocol. During the surface perturbation, electromyography was measured from tibialis anterior and gastrocnemius to further calculate a co-contraction index during the feed-forward and feedback period. A binary logistic regression was done with the nominal variable, if the participant succeeded in the postural task or not, set as dependent variable and the co-contraction indexes set as independent variables. Further, the variables from the sensory and motor testing were set as independent variables in two separate Orthogonal Projections of Latent Structures (OPLS)-models, one with the feed-forward- and the other with the feedback co-contraction index as dependent variable.Results: Higher levels of ankle joint stiffening during the feedback, but not the feed-forward period was associated with postural task failure. Feedback stiffening was explained by having slow non-postural reaction times, poor leg muscle strength and being female whereas feed-forward stiffening was not explained by sensory and motor variables.Conclusions: When subjected to an unpredicted surface perturbation, individuals with higher feedback stiffening had poorer postural control outcome, which was explained by poorer physical capacity. The level of feed-forward stiffening prior the perturbation was not associated with postural control outcome nor the investigated sensory and motor variables. The intricate causal relationships between physical capacity, stiffening and postural task success remains subject for future research. [ABSTRACT FROM AUTHOR]

To deal with the land surface physics uncertainties, a stochastic scheme based on stochastic perturbation of physics tendencies is implemented and tested. The impact of land surface physics uncertainties and their relative importance to land surface initial uncertainties are investigated in the regional ensemble forecasting system ALADIN‐LAEF (Aire Limitée Adaptation Dynamique Développement InterNational – Limited Area Ensemble Forecasting). The land surface initial perturbation is generated by using an ensemble of land surface data assimilation; and the land surface physics uncertainties by applying the idea of stochastically perturbed parametrization tendencies (SPPT) scheme. Three experiments are conducted and compared with the reference ensemble over a 2‐month period. The results show the introduction of land surface stochastic physics increases the ensemble spread, reduces the ensemble bias, and keeps neutral in deterministic forecast skill of the ensemble, its impact strongly depending on the quality of ensemble initial conditions. The ensemble land surface data assimilation has stronger positive impact on the ALADIN‐LAEF than the land surface stochastic physics for screen‐level temperature and humidity. There is not much impact on 10 m wind and precipitation. Best results are obtained when both the ensemble land surface data assimilation and land surface stochastic physics are used simultaneously; it gives a more reliable and statistically consistent forecast, which is contributed mainly by ensemble land surface data assimilation in the first forecast hours and largely by land surface stochastic physics in the later forecast hours. [ABSTRACT FROM AUTHOR]

Force plates for human movement analysis provide accurate measurements when mounted rigidly on an inertial reference frame. Large measurement errors occur, however, when the force plate is accelerated, or tilted relative to gravity. This prohibits the use of force plates in human perturbation studies with controlled surface movements, or in conditions where the foundation is moving or not sufficiently rigid. Here we present a linear model to predict the inertial and gravitational artifacts using accelerometer signals. The model is first calibrated with data collected from random movements of the unloaded system and then used to compensate for the errors in another trial. The method was tested experimentally on an instrumented force treadmill capable of dynamic mediolateral translation and sagittal pitch. The compensation was evaluated in five experimental conditions, including platform motions induced by actuators, by motor vibration, and by human ground reaction forces. In the test that included all sources of platform motion, the root-mean-square (RMS) errors were 39.0 N and 15.3 N m in force and moment, before compensation, and 1.6 N and 1.1 N m, after compensation. A sensitivity analysis was performed to determine the effect on estimating joint moments during human gait. Joint moment errors in hip, knee, and ankle were initially 53.80 N m, 32.69 N m, and 19.10 N m, and reduced to 1.67 N m, 1.37 N m, and 1.13 N m with our method. It was concluded that the compensation method can reduce the inertial and gravitational artifacts to an acceptable level for human gait analysis. [ABSTRACT FROM AUTHOR]

The edge effect and the Faraday cage effect are two major problems that occur when the target surface contains sharp corners and recessed areas. This can significantly affect the electric field and degrade the deposition uniformity of paint, which is important in electrostatic painting. A numerical study is presented in this paper to investigate the methods to minimize these problems. A 2D axisymmetric numerical model is proposed to analyze the electric field distribution in the electrostatic painting system, assuming a grounded target with a small surface perturbation at the center using COMSOL. Simulations have been performed for different configurations on the target, different values of the corner radius and the space charge. Also, simulations of paint particle trajectories and deposition have been obtained using ANSYS to examine the effect of the particle size and the charge-to-mass ratio on the coating buildup rate of a flat target and a target with an indentation or a protrusion. The injections of mono- and poly-dispersed uncharged and charged particles were considered. The results suggest that preliminary analysis of the electric field distribution on a target having a perturbation provides a simple design tool for predicting coating uniformity. [ABSTRACT FROM AUTHOR]

Instrumented treadmills provide a convenient means for applying horizontal perturbations during gait or standing. However, varying the treadmill belt speed introduces inertial artifacts in the sagittal plane moment component of the ground reaction force. Here we present a compensation method based on a second-order dynamic model that predicts inertial pitch moment from belt acceleration. The method was tested experimentally on an unloaded treadmill at a slow belt speed with small random variations (1.20±0.10 m/s) and at a faster belt speed with large random variations (2.00±0.50 m/s). Inertial artifacts of up to 12 Nm (root-mean-square, RMS) and 30 Nm (peak) were observed. Coefficients of the model were calibrated on one trial and then used to predict and compensate the pitch moment of another trial with different random variations. Coefficients of determination (R²) were 72.08% and 96.75% for the slow and fast conditions, respectively. After compensation, the root-mean-square (RMS) of the inertial artifact was reduced by 47.37% for the slow speed and 81.98% for fast speed, leaving only 1.5 Nm and 2.1 Nm of artifact uncorrected, respectively. It was concluded that the compensation technique reduced inertial errors substantially, thereby improving the accuracy in joint moment calculations on an instrumented treadmill with varying belt speed. [ABSTRACT FROM AUTHOR]

Background Postural control is organized around a task goal. The two most frequently used types of tasks for postural control research are translational (translation along the anterior-posterior axis) and rotational (rotation in sagittal plane) surface perturbations. These types of perturbations rotate the ankle joint, causing different magnitudes and directions of body sway. The purpose of this study was to investigate the effects of the type (translation vs. rotation) and direction (forward/toe up vs. backward/toe down) of the perturbation on postural responses. Method Nineteen healthy subjects were tested with four perturbations, i.e., forward and backward translation and toe up and toe down rotation. The onset latency and magnitude of muscle activations, angular changes, and COM displacements were measured. In addition, the kinematic data were divided into two phases. The initial phase reflected the balance disturbance induced by the platform movement, and the reversal phase reflected the balance reaction. Results The results showed that, in the initial phase, rotational perturbation induced earlier ankle movement and faster and larger vertical COM displacement, while translational and forward/toe up perturbations induced larger head and trunk angular change and faster and larger horizontal COM displacement. In the reversal phase, balance reaction was attained by multi-joint movements. Translational and forward/toe up perturbations that induced larger upper body instability evoked faster muscle activation as well as faster and larger hip or knee joint movements. Conclusions These findings provide insights into an appropriate support surface perturbation for the evaluation and training of balance. [ABSTRACT FROM AUTHOR]

[Display omitted] • The dynamic ST data of BSA was experimentally measured and theoretically modeled. • Non-asymptotic short-time formalism could well describe the initial dynamic ST data. • The adsorption of BSA at air–water interface was mixed-controlled. • A new approach of using equation of state to estimate Γ ∞ and K of BSA was trialed. • Values of Γ ∞ and K could be roughly estimated without using the equilibrium ST. The adsorption kinetics of bovine serum albumin (BSA) at an air–water interface was investigated by experimentally measuring and theoretically modeling the dynamic surface tension (ST) data. A pendant bubble tensiometer was utilized for two ST measurements: (i) the adsorption onto a freshly created bubble surface and (ii) the bubble expansion/compression at the latter stage. The dynamic ST data, during the early stage of BSA adsorption, were best-fitted with the short-time approximation equation (diffusion-control) and the non-asymptomatic short-time formalism [mixed-control, Moorkanikkara and Blankschtein, JCIS, 296, 442–457 (2006)]. The fitting showed that the non-asymptotic short-time formalism could well predict the dynamic ST data; thereby, implying that the adsorption of BSA onto a clean air–water interface was mixed-controlled. A new approach for estimating the maximum surface concentration (Γ ∞) and the intermolecular interaction amongst the adsorbed BSA molecules (K) was trialed. The relaxation of ST during a surface expansion was best-fitted with the Langmuir/Frumkin equation of state. A reasonably good fitting between the dynamic ST data and the theoretical ST profiles indicated that this approach could be used to estimate the Γ ∞ and K for BSA without requiring the equilibrium ST data. [ABSTRACT FROM AUTHOR]

Background: Falls are the leading cause of fatal and non-fatal injuries among older adults. Exercise programs appear to reduce fall risk, but the optimal type, frequency, and duration of exercise is unknown. External perturbations such as tripping and slipping are a major contributor to falls, and task-specific perturbation training to enhance dynamic stability has emerged as a promising approach to modifying fall risk. The purpose of this pilot study was 1) to determine the feasibility of conducting a large pragmatic randomized trial comparing a multidimensional exercise program inclusive of the surface perturbation treadmill training (SPTT) to multidimensional exercise alone (Standard PT); and 2) to assess fall outcomes between the two groups to determine whether an effect size large enough to warrant further study might be present. Methods: A randomized pilot study at two outpatient physical therapy clinics. Participants were over age 64 and referred for gait and balance training. Feasibility for a larger randomized trial was assessed based on the ability of therapists to incorporate the SPTT into their clinical practice and acceptance of study participation by eligible patients. Falls were assessed by telephone interview 3 months after enrollment. Results: Of 83 patients who were screened, 73 met inclusion criteria. SPTT was successfully adapted into clinical practice and 88% of eligible subjects were willing to be randomized, although 10% of the SPTT cohort dropped out prior to treatment. The SPTT group showed fewer subjects having any fall (19.23% vs. 33.33% Standard PT; p < 0.227) and fewer having an injurious fall (7.69% vs. 18.18%; p < 0.243). These results were not statistically significant but this pilot study was not powered for hypothesis testing. Conclusions: Physical therapy inclusive of surface perturbation treadmill training appears clinically feasible, and randomization between these two PT interventions is acceptable to the majority of patients. These results appear to merit longer-term study in an adequately powered trial. [ABSTRACT FROM AUTHOR]

Abstract: Previous studies have shown that individuals with WAD display decreased postural stability during standing and walking tasks. However, their ability to maintain seated upright posture has never been investigated. The objective of this study was to characterize kinematic and electromyographic postural stabilization patterns in individuals with chronic WAD and to compare these patterns with those in an able-bodied control group. Ten individuals with WAD and an age- and gender-matched group of healthy individuals were exposed to sudden forward and backward support surface translations while they were seated. Neck and trunk muscle activity and angular displacements as well as centers of mass (COMs) linear displacements at four levels of the head and trunk were computed. The displacement onset of the combined head, arms and trunk COM was significantly delayed in persons with WAD. However, their peak trunk angles were smaller and were reached sooner. In the WAD group, the activation onset of the lumbar erector spinae was less affected by perturbation direction and the sternocleidomastoid muscle, a neck flexor, showed a trend towards being activated later, compared to the healthy group. These results suggest that individuals with WAD may alter stretch reflex threshold and/or elicit a learned response for pain avoidance that may be direction-specific. Such findings highlight the importance of assessing both spatial and temporal characteristics across different levels of the spinal musculoskeletal system to evaluate multidirectional postural responses in WAD individuals. [Copyright &y& Elsevier]

As we age there are natural physiological deteriorations that decrease the accuracy and flexibility of the postural control system, which increases the risk of falling. Studies have found that there are individual differences in the ability to learn to manage repeated postural threats. The aim of this study was to investigate which factors explain why some individuals are less proficient at adapting to recurrent postural perturbations. Thirty-five community dwelling older adults performed substantial sensory and motor testing and answered surveys regarding fall-related concerns and cognitive function. They were also subjected to three identical surface perturbations where both kinematics and electromyography was captured. Those that were able to adapt to the third perturbation were assigned to the group "Non-fallers" whereas those that fell during all perturbations were assigned to the group "Fallers". The group designation dichotomized the sample in a hierarchical orthogonal projection of latent structures- the discriminant analysis model. We found that those who fell were older, had poorer physical performance, poorer strength and longer reaction times. The Fallers' postural control strategies were more reliant on the stiffening strategy along with a more extended posture and they were less skillful at making appropriate feedforward adaptations prior to the third perturbation.