Foot Mechanics Define Directional Changes in Curved-Path Walking: New Methods to Assess the Motor Skill of Walking

Although it is essential to navigating the world, curved path walking is a challenge to mediolateral balance control. The focus of previous curved-path walking research was in spatiotemporal characteristics. We quantified the foot-ground interaction, center of pressure (COP) characteristics during non-linear (eg curved-path) walking important to understand the functional mechanics of directional changes for curved paths. We hypothesized the foot mechanics differ between older adults with better versus poorer curved-path walking (Figure of 8 Walk Test, F8W). Twenty-five older adults (mean age 71.8 ± 8.9 years) completed the F8W on an instrumented walkway (Protokinetics, LLC.) The derived metrics of the foot mechanics included medial/lateral movement of the COP for inside and outside steps, maximum medial and lateral COP excursions, and total medial/lateral COP range. Pearson correlations were used to examine relations F8W (time and steps) and COP metrics; ANOVAs were used to examine differences in COP metrics between older adults grouped by median-split of F8W time. Longer F8W time and more steps were related to lesser total COP range and outside foot lateral maximum excursion (r range -0.415 to -0.706, p<0.04). Older adults with stronger F8W performance compared to poorer F8W performance had larger outside foot total COP ranges (3.61cm vs 4.39cm, p=0.016) and greater lateral excursion (1.60cm vs 2.12cm, p=0,003). Foot-ground interactions offer new insights into control of curved path walking and methods for evaluating efficacy of interventions focused on improving walking skill in older adults.

Температурная активация электронов проводимости в двойной квантовой яме HgTe/CdHgTe p-типа проводимости со слоями HgTe критической толщины

The temperature dependences of the Hall coefficient and magnetoresistivity of a p -type HgTe/CdHgTe double quantum well with HgTe layers of critical thickness in the temperature range T = 35–300 K under magnetic fields up to 9 T are investigated. The position of the earlier observed reentrant quantum Hall transition from plateau i = 1 to plateau i = 2 is found to be close to the transition field from light to heavy holes with an increase in the magnetic field in the classical Hall effect. It is found that thermally activated light electrons contribute to the Hall effect along with light and heavy holes at T ≥ 35 K. The activation energy of electrons is estimated from the temperature dependence of the electron concentration as 28 meV, which exceeds the calculated value from the lateral maximum of the valence subband to the edge of the lowest conduction subband, probably because of heterostructure asymmetry.

The Nature and Control of Postural Adaptations of Boys with and Without Developmental Coordination Disorder

This study compared the nature of postural adaptations and control tendencies, between 7 (n = 9) and 11-year-old boys (n = 10) with Developmental Coordination Disorder (DCD) and age-matched, younger (n = 10) and older (n = 9) peers in a leaning task. Examination of anterior-posterior, medio-lateral, maximum and mean area of sway, and path length revealed one significant interaction as older, unaffected boys swayed more than all other groups (p < .01). As a group, boys with DCD displayed smaller anterior-posterior (p < .01) and area of sway (p < .01). Analysis of relative time spent in the corrective phase (p < .002) revealed that boys with DCD spent 54% under feedback control while boys without DCD spent 78%. This was attributed to reduced proprioceptive sensitivity, as confirmed by significant differences between the groups (p < .009) in spectral analysis of peak frequency of sway.