Effect of stride frequency on thermoregulatory responses during endurance running in distance runners.

PubMed

Amano, Tatsuro; Ishitobi, Masaki; Ogura, Yukio; Inoue, Yoshimitsu; Koga, Shunsaku; Nishiyasu, Takeshi; Kondo, Narihiko

2016-10-01

Changing stride frequency may influence oxygen uptake and heart rate during running as a function of running economy and central command. This study investigated the influence of stride frequency manipulation on thermoregulatory responses during endurance running. Seven healthy endurance runners ran on a treadmill at a velocity of 15km/h for 60min in a controlled environmental chamber (ambient temperature 27°C and relative humidity 50%), and stride frequency was manipulated. Stride frequency was intermittently manipulated by increasing and decreasing frequency by 10% from the pre-determined preferred frequency. These periods of increase or decrease were separated by free frequency running in the order of free stride frequency, stride frequency manipulation (increase or decrease), free stride frequency, and stride frequency manipulation (increase or decrease) for 15min each. The increased and decreased stride frequencies were 110% and 91% of the free running frequency, respectively (196±6, 162±5, and 178±5steps/min, respectively, P<0.01). Compared to the control, stride frequency manipulation did not affect rectal temperature, heart rate, or the rate of perceived exhaustion during running. Whole-body sweat loss increased significantly when stride frequency was manipulated (1.48±0.11 and 1.57±0.11kg for control and manipulated stride frequencies, respectively, P<0.05), but stride frequency had a small effect on sweat loss overall (Cohen's d=0.31). A higher mean skin temperature was also observed under mixed frequency conditions compared to that in the control (P<0.05). While the precise mechanisms underlying these changes remain unknown (e.g. running economy or central command), our results suggest that manipulation of stride frequency does not have a large effect on sweat loss or other physiological variables, but does increase mean skin temperature during endurance running. Copyright © 2016. Published by Elsevier Ltd.

Passive in-home measurement of stride-to-stride gait variability comparing vision and Kinect sensing.

PubMed

Stone, Erik E; Skubic, Marjorie

2011-01-01

We present an analysis of measuring stride-to-stride gait variability passively, in a home setting using two vision based monitoring techniques: anonymized video data from a system of two web-cameras, and depth imagery from a single Microsoft Kinect. Millions of older adults fall every year. The ability to assess the fall risk of elderly individuals is essential to allowing them to continue living safely in independent settings as they age. Studies have shown that measures of stride-to-stride gait variability are predictive of falls in older adults. For this analysis, a set of participants were asked to perform a number of short walks while being monitored by the two vision based systems, along with a marker based Vicon motion capture system for ground truth. Measures of stride-to-stride gait variability were computed using each of the systems and compared against those obtained from the Vicon.

Cutting-edge platforms in cardiac tissue engineering.

PubMed

Fleischer, Sharon; Feiner, Ron; Dvir, Tal

2017-10-01

As cardiac disease takes a higher toll with each passing year, the need for new therapies to deal with the scarcity in heart donors becomes ever more pressing. Cardiac tissue engineering holds the promise of creating functional replacement tissues to repair heart tissue damage. In an attempt to bridge the gap between the lab and clinical realization, the field has made major strides. In this review, we will discuss state of the art technologies such as layer-by-layer assembly, bioprinting and bionic tissue engineering, all developed to overcome some of the major hurdles faced in the field. Copyright © 2017 Elsevier Ltd. All rights reserved.

Youth Baseball Pitching Stride Length: Normal Values and Correlation With Field Testing

PubMed Central

Fry, Karl E.; Pipkin, Andrew; Wittman, Kelcie; Hetzel, Scott; Sherry, Marc

2016-01-01

Background: Pitching biomechanical analysis has been recommended as an important component of performance, injury prevention, and rehabilitation. Normal values for youth pitching stride length have not been established, leading to application of normative values found among professional pitchers to youth pitchers. Hypotheses: The average youth pitching stride length will be significantly less than that of college and professional pitchers. There will be a positive correlation between stride length, lower extremity power, balance, and pitching experience. Study Design: Prospective cohort study. Level of Evidence: Level 3. Methods: Ninety-two youth baseball pitchers (aged 9-14 years) met the inclusion/exclusion criteria and completed the study. Stride length was recorded using a Dartfish video system over 3 maximal effort pitches. Both intra- and interrater reliability was calculated for the assessment of stride length. Double-leg vertical jump, single-leg stance time, leg length, weight, age, and pitching experience were also recorded. Results: Mean (SD) stride length was 66.0% (7.1%) of height. Stride length was correlated (P < 0.01) with vertical jump (0.38), pitching experience (0.36), and single-leg balance (0.28), with excellent intra- and interrater reliability (0.985 or higher). No significant correlations between stride length and body weight, leg length, or age existed. Conclusions: There was a significant difference between youth pitching stride length and the current published norms for older and more elite throwers. There was a positive correlation between stride length and lower extremity power, pitching experience, and single-leg balance. Clinical Relevance: Two-dimensional analysis of stride length allows for the assessment of pitching biomechanics in a practical manner. These values can be used for return to pitching parameters after an injury and designing injury prevention and performance programs. PMID:27864504

Youth Baseball Pitching Stride Length: Normal Values and Correlation With Field Testing.

PubMed

Fry, Karl E; Pipkin, Andrew; Wittman, Kelcie; Hetzel, Scott; Sherry, Marc

Pitching biomechanical analysis has been recommended as an important component of performance, injury prevention, and rehabilitation. Normal values for youth pitching stride length have not been established, leading to application of normative values found among professional pitchers to youth pitchers. The average youth pitching stride length will be significantly less than that of college and professional pitchers. There will be a positive correlation between stride length, lower extremity power, balance, and pitching experience. Prospective cohort study. Level 3. Ninety-two youth baseball pitchers (aged 9-14 years) met the inclusion/exclusion criteria and completed the study. Stride length was recorded using a Dartfish video system over 3 maximal effort pitches. Both intra- and interrater reliability was calculated for the assessment of stride length. Double-leg vertical jump, single-leg stance time, leg length, weight, age, and pitching experience were also recorded. Mean (SD) stride length was 66.0% (7.1%) of height. Stride length was correlated ( P < 0.01) with vertical jump (0.38), pitching experience (0.36), and single-leg balance (0.28), with excellent intra- and interrater reliability (0.985 or higher). No significant correlations between stride length and body weight, leg length, or age existed. There was a significant difference between youth pitching stride length and the current published norms for older and more elite throwers. There was a positive correlation between stride length and lower extremity power, pitching experience, and single-leg balance. Two-dimensional analysis of stride length allows for the assessment of pitching biomechanics in a practical manner. These values can be used for return to pitching parameters after an injury and designing injury prevention and performance programs.

How humans use visual optic flow to regulate stepping during walking.

PubMed

Salinas, Mandy M; Wilken, Jason M; Dingwell, Jonathan B

2017-09-01

Humans use visual optic flow to regulate average walking speed. Among many possible strategies available, healthy humans walking on motorized treadmills allow fluctuations in stride length (L n ) and stride time (T n ) to persist across multiple consecutive strides, but rapidly correct deviations in stride speed (S n =L n /T n ) at each successive stride, n. Several experiments verified this stepping strategy when participants walked with no optic flow. This study determined how removing or systematically altering optic flow influenced peoples' stride-to-stride stepping control strategies. Participants walked on a treadmill with a virtual reality (VR) scene projected onto a 3m tall, 180° semi-cylindrical screen in front of the treadmill. Five conditions were tested: blank screen ("BLANK"), static scene ("STATIC"), or moving scene with optic flow speed slower than ("SLOW"), matched to ("MATCH"), or faster than ("FAST") walking speed. Participants took shorter and faster strides and demonstrated increased stepping variability during the BLANK condition compared to the other conditions. Thus, when visual information was removed, individuals appeared to walk more cautiously. Optic flow influenced both how quickly humans corrected stride speed deviations and how successful they were at enacting this strategy to try to maintain approximately constant speed at each stride. These results were consistent with Weber's law: healthy adults more-rapidly corrected stride speed deviations in a no optic flow condition (the lower intensity stimuli) compared to contexts with non-zero optic flow. These results demonstrate how the temporal characteristics of optic flow influence ability to correct speed fluctuations during walking. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparison of the temporal kinematics of the canter pirouette and collected canter.

PubMed

Burns, T E; Clayton, H M

1997-05-01

The objectives were to compare the temporal characteristics of canter pirouette strides with collected canter strides in elite dressage horses, and to determine whether the stride kinematics of the canter pirouettes fulfilled the requirements specified in the Federation Equestre Internationale Rules for Dressage Events. Eleven horses were videotaped (60 fields/s) during the individual medal competition at the 1992 Olympic Games. Temporal variables were extracted from the videotapes using standard methods. Two strides were analysed on each of the left and right leads and these were pooled to give mean values for the collected canter and the pirouettes. The pirouettes were completed in 4-9 strides, (mean of 6.4). In the collected canter strides, mean duration of the suspension was 0.013 s. There was no suspension in any of the pirouette strides, instead the stance phases of the leading forelimb and trailing hindlimb overlapped by a mean of 0.163 s. In 9 horses the trailing forelimb contacted the ground before the diagonal leading hindlimb in the collected canter, whereas in the pirouettes the leading hindlimb always made contact before the trailing forelimb (mean dissociation 0.164 s), giving the strides a distinct 4 beat rhythm. Due to increases in advanced placement between the diagonal limb pair and between the 2 forelimbs, the stride duration was longer in the pirouette (0.879 s) than the collected canter (0.629 s). It is concluded that the canter pirouette strides did not maintain the rhythm and timing of the the collected canter strides in any of the 11 horses.

Locomotion evaluation for racing in thoroughbreds.

PubMed

Barrey, E; Evans, S E; Evans, D L; Curtis, R A; Quinton, R; Rose, R J

2001-04-01

The potential racing and locomotory profile of a Thoroughbred yearling should be taken into account for its training programme and racing career. A gait test has been designed to assist the trainer in this task. The aim of this study was to investigate the temporal and kinetic locomotory variables of Thoroughbreds at the gallop, in relationship to their racing ability. Thirty Thoroughbred horses in race training were tested at maximal speed during a training session. The training exercise consisted of a warming-up session at trot and canter for 10 min followed by a gallop session at increasing speed on a dirt track 1942 m long. The maximal speed was measured for the last 800 m before the finishing post. An acclerometric device attached to the girth provided quantitative information about the kinetic and temporal variables of the gallop such as: stride length (SL), stride frequency (SF), times elapsed between each hoof midstance phase (HIND, DIAGO, FORE), regularity of the strides (REG), mean vector of propulsion (VPROP), energy of propulsion (EPROP) and energy of loading (ELOAD). The performance records (number of wins, placings and average earning/start [PERF]) were used to analyse the relationship with the gait measurements. The mean maximum speed was 15.26 m/s. Several locomotory variables were significantly (P < 0.05) correlated to the gallop speed: SL (0.90), SF (0.75), DIAGO (0.42), REG (-0.47), VPROP (0.52), ELOAD (0.56) and EPROP (0.65). There were significant correlations between PERF and the following gait variables: REG (0.79), DIAGO (0.43), SF (0.42), SL (-0.32) and ELOAD (-0.40). The horses that won short distance races (< 1400 m) had a larger relative ground contact duration and higher stride frequency than horses that won in longer distance races. The gait test was easy to perform and provided useful locomotory variables that may be used to evaluate the racing ability of the Thoroughbreds in training.

GAIT DYNAMICS, FRACTALS AND FALLS: FINDING MEANING IN THE STRIDE-TO-STRIDE FLUCTUATIONS OF HUMAN WALKING

PubMed Central

Hausdorff, Jeffrey M

2007-01-01

Until recently, quantitative studies of walking have typically focused on properties of a typical or average stride, ignoring the stride-to-stride fluctuations and considering these fluctuations to be noise. Work over the past two decades has demonstrated, however, that the alleged noise actually conveys important information. The magnitude of the stride-to-stride fluctuations and their changes over time during a walk – gait dynamics – may be useful in understanding the physiology of gait, in quantifying age-related and pathologic alterations in the locomotor control system, and in augmenting objective measurement of mobility and functional status Indeed, alterations in gait dynamics may help to determine disease severity, medication utility, and fall risk, and to objectively document improvements in response to therapeutic interventions, above and beyond what can be gleaned from measures based on the average, typical stride. This review discusses support for the idea that gait dynamics has meaning and may be useful in providing insight into the neural control of locomtion and for enhancing functional assessment of aging, chronic disease, and their impact on mobility. PMID:17618701

PoleStriding exercise and vitamin E for management of peripheral vascular disease.

PubMed

Collins, Eileen G; Edwin Langbein, W; Orebaugh, Cynthia; Bammert, Christine; Hanson, Karla; Reda, Domenic; Edwards, Lonnie C; Littooy, Fred N

2003-03-01

The purpose of this investigation was to evaluate the efficacy of PoleStriding exercise (a form of walking that uses muscles of the upper and lower body in a continuous movement similar to cross-country skiing) and vitamin E (alpha-tocopherol) to improve walking ability and perceived quality of life (QOL) of patients with claudication pain secondary to peripheral arterial disease (PAD). Fifty-two subjects were randomized into four groups: PoleStriding with vitamin E (N = 13), PoleStriding with placebo (N= 14), vitamin E without exercise (N= 13), and placebo without exercise (N = 12). The dose of vitamin E was 400 IU daily. Only the PoleStriding with vitamin E and PoleStriding with placebo groups received PoleStriding instruction and training. Assignment to vitamin E or placebo was double blind. Subjects trained three times weekly for 30-45 min (rest time excluded). Individuals in vitamin E and placebo groups came to the laboratory biweekly for ankle blood-pressure measurements. Results of this randomized clinical trial provide strong evidence that PoleStriding significantly (P< 0.001) improved exercise tolerance on the constant work-rate and incremental treadmill tests. Ratings of perceived claudication pain were significantly less after the PoleStriding training program (P= 0.02). In contrast, vitamin E did not have a statistically significant effect on the subjects' ratings of perceived leg pain (P= 0.35) or treadmill walking duration ( P= 0.36). Perceived distance and walking speed (Walking Impairment Questionnaire) and perceived physical function (Rand Short Form-36) improved in the PoleStriding trained group only (P< 0.001, 0.022 and 0.003, respectively). PoleStriding effectively improved the exercise tolerance and perceived QOL of patients with PAD. Little additional benefit to exercise capacity was realized from vitamin E supplementation.

Increased gait variability may not imply impaired stride-to-stride control of walking in healthy older adults: Winner: 2013 Gait and Clinical Movement Analysis Society Best Paper Award.

PubMed

Dingwell, Jonathan B; Salinas, Mandy M; Cusumano, Joseph P

2017-06-01

Older adults exhibit increased gait variability that is associated with fall history and predicts future falls. It is not known to what extent this increased variability results from increased physiological noise versus a decreased ability to regulate walking movements. To "walk", a person must move a finite distance in finite time, making stride length (L n ) and time (T n ) the fundamental stride variables to define forward walking. Multiple age-related physiological changes increase neuromotor noise, increasing gait variability. If older adults also alter how they regulate their stride variables, this could further exacerbate that variability. We previously developed a Goal Equivalent Manifold (GEM) computational framework specifically to separate these causes of variability. Here, we apply this framework to identify how both young and high-functioning healthy older adults regulate stepping from each stride to the next. Healthy older adults exhibited increased gait variability, independent of walking speed. However, despite this, these healthy older adults also concurrently exhibited no differences (all p>0.50) from young adults either in how their stride variability was distributed relative to the GEM or in how they regulated, from stride to stride, either their basic stepping variables or deviations relative to the GEM. Using a validated computational model, we found these experimental findings were consistent with increased gait variability arising solely from increased neuromotor noise, and not from changes in stride-to-stride control. Thus, age-related increased gait variability likely precedes impaired stepping control. This suggests these changes may in turn precede increased fall risk. Copyright © 2017 Elsevier B.V. All rights reserved.

Dynamic markers of altered gait rhythm in amyotrophic lateral sclerosis

NASA Technical Reports Server (NTRS)

Hausdorff, J. M.; Lertratanakul, A.; Cudkowicz, M. E.; Peterson, A. L.; Kaliton, D.; Goldberger, A. L.

2000-01-01

Amyotrophic lateral sclerosis (ALS) is a disorder marked by loss of motoneurons. We hypothesized that subjects with ALS would have an altered gait rhythm, with an increase in both the magnitude of the stride-to-stride fluctuations and perturbations in the fluctuation dynamics. To test for this locomotor instability, we quantitatively compared the gait rhythm of subjects with ALS with that of normal controls and with that of subjects with Parkinson's disease (PD) and Huntington's disease (HD), pathologies of the basal ganglia. Subjects walked for 5 min at their usual pace wearing an ankle-worn recorder that enabled determination of the duration of each stride and of stride-to-stride fluctuations. We found that the gait of patients with ALS is less steady and more temporally disorganized compared with that of healthy controls. In addition, advanced ALS, HD, and PD were associated with certain common, as well as apparently distinct, features of altered stride dynamics. Thus stride-to-stride control of gait rhythm is apparently compromised with ALS. Moreover, a matrix of markers based on gait dynamics may be useful in characterizing certain pathologies of motor control and, possibly, in quantitatively monitoring disease progression and evaluating therapeutic interventions.

Locomotor, cardiocirculatory and metabolic adaptations to training in Andalusian and Anglo-Arabian horses.

PubMed

Muñoz, A; Santisteban, R; Rubio, M D; Agüera, E I; Escribano, B M; Castejón, F M

1999-02-01

The effects of two training programmes in 20 Andalusian and 12 Anglo-Arabian horses were evaluated by an increasing intensity work test at velocities of 4, 5, 6, 7 and 8 m sec(-1). Heart rate was monitored and blood samples were drawn at rest and after each velocity to analyse packed cell volume, haemoglobin concentration, plasma lactate and potassium levels. Furthermore, the programmes were video-taped and stride length, duration and frequency, stance (restraint and propulsion), swing phase durations and stride vertical component were measured. The training protocol of the Andalusian horses produced significant decreases in the cardiovascular, haematological and metabolic responses to exercise. Locomotory training adaptation consisted of an increased stride frequency and a reduced stride length and vertical stride component. The last variable was the limiting factor of stride length both before and after training in the Andalusian horses. A different training protocol for show-jumping competition in Anglo-Arabian horses failed to show significant differences in the studied parameters to the work test, although an increase in stride length at velocities of over 6 m sec(-1) was observed. Stride vertical component did not have an effect on the physiological response to exercise, either before or after training.

Investigating the correlation between paediatric stride interval persistence and gross energy expenditure.

PubMed

Fairley, Jillian A; Sejdić, Ervin; Chau, Tom

2010-02-26

Stride interval persistence, a term used to describe the correlation structure of stride interval time series, is thought to provide insight into neuromotor control, though its exact clinical meaning has not yet been realized. Since human locomotion is shaped by energy efficient movements, it has been hypothesized that stride interval dynamics and energy expenditure may be inherently tied, both having demonstrated similar sensitivities to age, disease, and pace-constrained walking. This study tested for correlations between stride interval persistence and measures of energy expenditure including mass-specific gross oxygen consumption per minute (VO₂), mass-specific gross oxygen cost per meter (VO₂) and heart rate (HR). Metabolic and stride interval data were collected from 30 asymptomatic children who completed one 10-minute walking trial under each of the following conditions: (i) overground walking, (ii) hands-free treadmill walking, and (iii) handrail-supported treadmill walking. Stride interval persistence was not significantly correlated with (p > 0.32), VO₂ (p > 0.18) or HR (p > 0.56). No simple linear dependence exists between stride interval persistence and measures of gross energy expenditure in asymptomatic children when walking overground and on a treadmill.

Select injury-related variables are affected by stride length and foot strike style during running.

PubMed

Boyer, Elizabeth R; Derrick, Timothy R

2015-09-01

Some frontal plane and transverse plane variables have been associated with running injury, but it is not known if they differ with foot strike style or as stride length is shortened. To identify if step width, iliotibial band strain and strain rate, positive and negative free moment, pelvic drop, hip adduction, knee internal rotation, and rearfoot eversion differ between habitual rearfoot and habitual mid-/forefoot strikers when running with both a rearfoot strike (RFS) and a mid-/forefoot strike (FFS) at 3 stride lengths. Controlled laboratory study. A total of 42 healthy runners (21 habitual rearfoot, 21 habitual mid-/forefoot) ran overground at 3.35 m/s with both a RFS and a FFS at their preferred stride lengths and 5% and 10% shorter. Variables did not differ between habitual groups. Step width was 1.5 cm narrower for FFS, widening to 0.8 cm as stride length shortened. Iliotibial band strain and strain rate did not differ between foot strikes but decreased as stride length shortened (0.3% and 1.8%/s, respectively). Pelvic drop was reduced 0.7° for FFS compared with RFS, and both pelvic drop and hip adduction decreased as stride length shortened (0.8° and 1.5°, respectively). Peak knee internal rotation was not affected by foot strike or stride length. Peak rearfoot eversion was not different between foot strikes but decreased 0.6° as stride length shortened. Peak positive free moment (normalized to body weight [BW] and height [h]) was not affected by foot strike or stride length. Peak negative free moment was -0.0038 BW·m/h greater for FFS and decreased -0.0004 BW·m/h as stride length shortened. The small decreases in most variables as stride length shortened were likely associated with the concomitant wider step width. RFS had slightly greater pelvic drop, while FFS had slightly narrower step width and greater negative free moment. Shortening one's stride length may decrease or at least not increase propensity for running injuries based on the variables that we measured. One foot strike style does not appear universally better than the other; rather, different foot strike styles may predispose runners to different types of injuries. © 2015 The Author(s).

Strategies for obstacle avoidance during walking in the cat.

PubMed

Chu, Kevin M I; Seto, Sandy H; Beloozerova, Irina N; Marlinski, Vladimir

2017-08-01

Avoiding obstacles is essential for successful navigation through complex environments. This study aimed to clarify what strategies are used by a typical quadruped, the cat, to avoid obstacles during walking. Four cats walked along a corridor 2.5 m long and 25 or 15 cm wide. Obstacles, small round objects 2.5 cm in diameter and 1 cm in height, were placed on the floor in various locations. Movements of the paw were recorded with a motion capture and analysis system (Visualeyez, PTI). During walking in the wide corridor, cats' preferred strategy for avoiding a single obstacle was circumvention, during which the stride direction changed while stride duration and swing-to-stride duration ratio were preserved. Another strategy, stepping over the obstacle, was used during walking in the narrow corridor, when lateral deviations of walking trajectory were restricted. Stepping over the obstacle involved changes in two consecutive strides. The stride preceding the obstacle was shortened, and swing-to-stride ratio was reduced. The obstacle was negotiated in the next stride of increased height and normal duration and swing-to-stride ratio. During walking on a surface with multiple obstacles, both strategies were used. To avoid contact with the obstacle, cats placed the paw away from the object at a distance roughly equal to the diameter of the paw. During obstacle avoidance cats prefer to alter muscle activities without altering the locomotor rhythm. We hypothesize that a choice of the strategy for obstacle avoidance is determined by minimizing the complexity of neuro-motor processes required to achieve the behavioral goal. NEW & NOTEWORTHY In a study of feline locomotor behavior we found that the preferred strategy to avoid a small obstacle is circumvention. During circumvention, stride direction changes but length and temporal structure are preserved. Another strategy, stepping over the obstacle, is used in narrow walkways. During overstepping, two strides adjust. A stride preceding the obstacle decreases in length and duration. The following stride negotiating the obstacle increases in height while retaining normal temporal structure and nearly normal length. Copyright © 2017 the American Physiological Society.

Targeting dopa-sensitive and dopa-resistant gait dysfunction in Parkinson's disease: selective responses to internal and external cues.

PubMed

Rochester, Lynn; Baker, Katherine; Nieuwboer, Alice; Burn, David

2011-02-15

Independence of certain gait characteristics from dopamine replacement therapies highlights its complex pathophysiology in Parkinson's disease (PD). We explored the effect of two different cue strategies on gait characteristics in relation to their response to dopaminergic medications. Fifty people with PD (age 69.22 ± 6.6 years) were studied. Participants walked with and without cues presented in a randomized order. Cue strategies were: (1) internal cue (attention to increase step length) and (2) external cue (auditory cue with instruction to take large step to the beat). Testing was carried out two times at home (on and off medication). Gait was measured using a Stride Analyzer (B&L Engineering). Gait outcomes were walking speed, stride length, step frequency, and coefficient of variation (CV) of stride time and double limb support duration (DLS). Walking speed, stride length, and stride time CV improved on dopaminergic medications, whereas step frequency and DLS CV did not. Internal and external cues increased stride time and walking speed (on and off dopaminergic medications). Only the external cue significantly improved stride time CV and DLS CV, whereas the internal cue had no effect (on and off dopaminergic medications). Internal and external cues selectively modify gait characteristics in relation to the type of gait disturbance and its dopa-responsiveness. Although internal (attention) and external cues target dopaminergic gait dysfunction (stride length), only external cues target stride to stride fluctuations in gait. Despite an overlap with dopaminergic pathways, external cues may effectively address nondopaminergic gait dysfunction and potentially increase mobility and reduce gait instability and falls. Copyright © 2010 Movement Disorder Society.

Bobcat attack on a cottontail rabbit

USGS Publications Warehouse

Biggins, D.E.; Biggins, D.M.

2006-01-01

We observed an attack by a bobcat (Lynx rufus) on a cottontail rabbit (Sylvilagus) that involved stealthy approach by the cat for >1 h, followed by a 12.3-s chase covering 116.0 m for the cat and 128.4 m for the rabbit. During the chase, the route of the cat from starting point to kill site was more direct than the semi-circular route of the rabbit. Stride lengths for the cat and total distance covered by the chase were longer than those previously reported for bobcats.

Interaction effects of stride angle and strike pattern on running economy.

PubMed

Santos-Concejero, J; Tam, N; Granados, C; Irazusta, J; Bidaurrazaga-Letona, I; Zabala-Lili, J; Gil, S M

2014-12-01

This study aimed to investigate the relationship between stride angle and running economy (RE) in athletes with different foot strike patterns. 30 male runners completed 4 min running stages on a treadmill at different velocities. During the test, biomechanical variables such as stride angle, swing time, contact time, stride length and frequency were recorded using an optical measurement system. Their foot strike pattern was determined, and VO2 at velocities below the lactate threshold were measured to calculate RE. Midfoot/forefoot strikers had better RE than rearfoot strikers (201.5±5.6 ml · kg(-1) · km(-1) vs. 213.5±4.2 ml · kg(-1) · km(-1)respectively; p=0.019). Additionally, midfoot/fore-foot strikers presented higher stride angles than rearfoot strikers (p=0.043). Linear modelling analysis showed that stride angle is closely related to RE (r=0.62, p<0.001) and that the effect of stride angle on RE was different in the 2 groups. From an arbitrary value of 4°, a rearfoot strike pattern is likely to be more economical, whereas at any lower degree, the midfoot/forefoot strike pattern appears to be more desirable. A biomechanical running technique characterised by high stride angles and a midfoot/forefoot strike pattern is advantageous for a better RE. Athletes may find stride angle useful for improving RE. © Georg Thieme Verlag KG Stuttgart · New York.

The gait standard deviation, a single measure of kinematic variability.

PubMed

Sangeux, Morgan; Passmore, Elyse; Graham, H Kerr; Tirosh, Oren

2016-05-01

Measurement of gait kinematic variability provides relevant clinical information in certain conditions affecting the neuromotor control of movement. In this article, we present a measure of overall gait kinematic variability, GaitSD, based on combination of waveforms' standard deviation. The waveform standard deviation is the common numerator in established indices of variability such as Kadaba's coefficient of multiple correlation or Winter's waveform coefficient of variation. Gait data were collected on typically developing children aged 6-17 years. Large number of strides was captured for each child, average 45 (SD: 11) for kinematics and 19 (SD: 5) for kinetics. We used a bootstrap procedure to determine the precision of GaitSD as a function of the number of strides processed. We compared the within-subject, stride-to-stride, variability with the, between-subject, variability of the normative pattern. Finally, we investigated the correlation between age and gait kinematic, kinetic and spatio-temporal variability. In typically developing children, the relative precision of GaitSD was 10% as soon as 6 strides were captured. As a comparison, spatio-temporal parameters required 30 strides to reach the same relative precision. The ratio stride-to-stride divided by normative pattern variability was smaller in kinematic variables (the smallest for pelvic tilt, 28%) than in kinetic and spatio-temporal variables (the largest for normalised stride length, 95%). GaitSD had a strong, negative correlation with age. We show that gait consistency may stabilise only at, or after, skeletal maturity. Copyright © 2016 Elsevier B.V. All rights reserved.

The desert ant odometer: a stride integrator that accounts for stride length and walking speed.

PubMed

Wittlinger, Matthias; Wehner, Rüdiger; Wolf, Harald

2007-01-01

Desert ants, Cataglyphis, use path integration as a major means of navigation. Path integration requires measurement of two parameters, namely, direction and distance of travel. Directional information is provided by a celestial compass, whereas distance measurement is accomplished by a stride integrator, or pedometer. Here we examine the recently demonstrated pedometer function in more detail. By manipulating leg lengths in foraging desert ants we could also change their stride lengths. Ants with elongated legs ('stilts') or shortened legs ('stumps') take larger or shorter strides, respectively, and misgauge travel distance. Travel distance is overestimated by experimental animals walking on stilts, and underestimated by animals walking on stumps - strongly indicative of stride integrator function in distance measurement. High-speed video analysis was used to examine the actual changes in stride length, stride frequency and walking speed caused by the manipulations of leg length. Unexpectedly, quantitative characteristics of walking behaviour remained almost unaffected by imposed changes in leg length, demonstrating remarkable robustness of leg coordination and walking performance. These data further allowed normalisation of homing distances displayed by manipulated animals with regard to scaling and speed effects. The predicted changes in homing distance are in quantitative agreement with the experimental data, further supporting the pedometer hypothesis.

Complexity, fractal dynamics and determinism in treadmill ambulation: Implications for clinical biomechanists.

PubMed

Hollman, John H; Watkins, Molly K; Imhoff, Angela C; Braun, Carly E; Akervik, Kristen A; Ness, Debra K

2016-08-01

Reduced inter-stride complexity during ambulation may represent a pathologic state. Evidence is emerging that treadmill training for rehabilitative purposes may constrain the locomotor system and alter gait dynamics in a way that mimics pathological states. The purpose of this study was to examine the dynamical system components of gait complexity, fractal dynamics and determinism during treadmill ambulation. Twenty healthy participants aged 23.8 (1.2) years walked at preferred walking speeds for 6min on a motorized treadmill and overground while wearing APDM 6 Opal inertial monitors. Stride times, stride lengths and peak sagittal plane trunk velocities were measured. Mean values and estimates of complexity, fractal dynamics and determinism were calculated for each parameter. Data were compared between overground and treadmill walking conditions. Mean values for each gait parameter were statistically equivalent between overground and treadmill ambulation (P>0.05). Through nonlinear analyses, however, we found that complexity in stride time signals (P<0.001), and long-range correlations in stride time and stride length signals (P=0.005 and P=0.024, respectively), were reduced on the treadmill. Treadmill ambulation induces more predictable inter-stride time dynamics and constrains fluctuations in stride times and stride lengths, which may alter feedback from destabilizing perturbations normally experienced by the locomotor control system during overground ambulation. Treadmill ambulation, therefore, may provide less opportunity for experiencing the adaptability necessary to successfully ambulate overground. Investigators and clinicians should be aware that treadmill ambulation will alter dynamic gait characteristics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Stride search: A general algorithm for storm detection in high-resolution climate data

DOE PAGES

Bosler, Peter A.; Roesler, Erika L.; Taylor, Mark A.; ...

2016-04-13

This study discusses the problem of identifying extreme climate events such as intense storms within large climate data sets. The basic storm detection algorithm is reviewed, which splits the problem into two parts: a spatial search followed by a temporal correlation problem. Two specific implementations of the spatial search algorithm are compared: the commonly used grid point search algorithm is reviewed, and a new algorithm called Stride Search is introduced. The Stride Search algorithm is defined independently of the spatial discretization associated with a particular data set. Results from the two algorithms are compared for the application of tropical cyclonemore » detection, and shown to produce similar results for the same set of storm identification criteria. Differences between the two algorithms arise for some storms due to their different definition of search regions in physical space. The physical space associated with each Stride Search region is constant, regardless of data resolution or latitude, and Stride Search is therefore capable of searching all regions of the globe in the same manner. Stride Search's ability to search high latitudes is demonstrated for the case of polar low detection. Wall clock time required for Stride Search is shown to be smaller than a grid point search of the same data, and the relative speed up associated with Stride Search increases as resolution increases.« less

Experimental investigation of starting characteristics and wave propagation from a shallow open cavity and its acoustic emission at supersonic speed

NASA Astrophysics Data System (ADS)

Pandian, S.; Desikan, S. L. N.; Niranjan, Sahoo

2018-01-01

Experiments were carried out on a shallow open cavity (L/D = 5) at a supersonic Mach number (M = 1.8) to understand its transient starting characteristics, wave propagation (inside and outside the cavity) during one vortex shedding cycle, and acoustic emission. Starting characteristics and wave propagation were visualized through time resolved schlieren images, while acoustic emissions were captured through unsteady pressure measurements. Results showed a complex shock system during the starting process which includes characteristics of the bifurcated shock system, shock train, flow separation, and shock wave boundary layer interaction. In one vortex shedding cycle, vortex convection from cavity leading edge to cavity trailing edge was observed. Flow features outside the cavity demonstrated the formation and downstream movement of a λ-shock due to the interaction of shock from the cavity leading edge and shock due to vortex and generation of waves on account of shear layer impingement at the cavity trailing edge. On the other hand, interesting wave structures and its propagation were monitored inside the cavity. In one vortex shedding cycle, two waves such as a reflected compression wave from a cavity leading edge in the previous vortex shedding cycle and a compression wave due to the reflection of Mach wave at the cavity trailing edge corner in the current vortex shedding cycle were visualized. The acoustic emission from the cavity indicated that the 2nd to 4th modes/tones are dominant, whereas the 1st mode contains broadband spectrum. In the present studies, the cavity feedback mechanism was demonstrated through a derived parameter coherence coefficient.

Association between daily walking and antioxidant capacity in patients with symptomatic peripheral artery disease.

PubMed

Gardner, Andrew W; Montgomery, Polly S; Zhao, Yan D; Silva-Palacios, Federico; Ungvari, Zoltan; Csiszar, Anna; Sonntag, William E

2017-06-01

The primary aim of the study was to assess whether both the amount and pace of daily walking were associated with circulating antioxidant capacity in symptomatic patients with peripheral artery disease (PAD). Community-based walking was measured in 244 men and women who were limited by symptomatic PAD during a 1-week period in which they wore an ankle-mounted step activity monitor. Patients were further characterized by circulating antioxidant capacity with the OxiSelect (Cell Biolabs Inc, San Diego, Calif) hydroxyl radical antioxidant capacity (HORAC) activity assay. To assess the amount of walking, patients were grouped into low (≤2440 strides/d), middle (2441-3835 strides/d), and high (>3835 strides/d) stride tertiles. HORAC was higher in the middle (P = .03) and high (P = .01) stride tertiles than in the low tertile, but there was no difference between middle and high tertiles (P = .44). To assess the pace of walking, patients were grouped into slow (<25.0 strides/min), middle (25.0-31.6 strides/min), and fast (>31.6 strides/min) cadence tertiles. HORAC was higher in the high cadence tertile than in the low (P < .01) and middle (P < .01) tertiles, but there was no difference between low and middle tertiles (P = .48). Similar findings were obtained on group differences in HORAC after adjusting for age, sex, race, and ankle-brachial index for both the amount and pace of daily walking. Walking >2440 strides each day and walking at a cadence faster than 31.6 strides/min for 30 minutes each day are both associated with greater circulating antioxidant capacity in symptomatic patients with PAD. The clinical significance is that a home-based walking program may be one approach to increase endogenous antioxidant capacity. Copyright © 2017 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Identifying Stride-To-Stride Control Strategies in Human Treadmill Walking

PubMed Central

Dingwell, Jonathan B.; Cusumano, Joseph P.

2015-01-01

Variability is ubiquitous in human movement, arising from internal and external noise, inherent biological redundancy, and from the neurophysiological control actions that help regulate movement fluctuations. Increased walking variability can lead to increased energetic cost and/or increased fall risk. Conversely, biological noise may be beneficial, even necessary, to enhance motor performance. Indeed, encouraging more variability actually facilitates greater improvements in some forms of locomotor rehabilitation. Thus, it is critical to identify the fundamental principles humans use to regulate stride-to-stride fluctuations in walking. This study sought to determine how humans regulate stride-to-stride fluctuations in stepping movements during treadmill walking. We developed computational models based on pre-defined goal functions to compare if subjects, from each stride to the next, tried to maintain the same speed as the treadmill, or instead stay in the same position on the treadmill. Both strategies predicted average behaviors empirically indistinguishable from each other and from that of humans. These strategies, however, predicted very different stride-to-stride fluctuation dynamics. Comparisons to experimental data showed that human stepping movements were generally well-predicted by the speed-control model, but not by the position-control model. Human subjects also exhibited no indications they corrected deviations in absolute position only intermittently: i.e., closer to the boundaries of the treadmill. Thus, humans clearly do not adopt a control strategy whose primary goal is to maintain some constant absolute position on the treadmill. Instead, humans appear to regulate their stepping movements in a way most consistent with a strategy whose primary goal is to try to maintain the same speed as the treadmill at each consecutive stride. These findings have important implications both for understanding how biological systems regulate walking in general and for being able to harness these mechanisms to develop more effective rehabilitation interventions to improve locomotor performance. PMID:25910253

Recommended number of strides for automatic assessment of gait symmetry and regularity in above-knee amputees by means of accelerometry and autocorrelation analysis

PubMed Central

2012-01-01

Background Symmetry and regularity of gait are essential outcomes of gait retraining programs, especially in lower-limb amputees. This study aims presenting an algorithm to automatically compute symmetry and regularity indices, and assessing the minimum number of strides for appropriate evaluation of gait symmetry and regularity through autocorrelation of acceleration signals. Methods Ten transfemoral amputees (AMP) and ten control subjects (CTRL) were studied. Subjects wore an accelerometer and were asked to walk for 70 m at their natural speed (twice). Reference values of step and stride regularity indices (Ad1 and Ad2) were obtained by autocorrelation analysis of the vertical and antero-posterior acceleration signals, excluding initial and final strides. The Ad1 and Ad2 coefficients were then computed at different stages by analyzing increasing portions of the signals (considering both the signals cleaned by initial and final strides, and the whole signals). At each stage, the difference between Ad1 and Ad2 values and the corresponding reference values were compared with the minimum detectable difference, MDD, of the index. If that difference was less than MDD, it was assumed that the portion of signal used in the analysis was of sufficient length to allow reliable estimation of the autocorrelation coefficient. Results All Ad1 and Ad2 indices were lower in AMP than in CTRL (P < 0.0001). Excluding initial and final strides from the analysis, the minimum number of strides needed for reliable computation of step symmetry and stride regularity was about 2.2 and 3.5, respectively. Analyzing the whole signals, the minimum number of strides increased to about 15 and 20, respectively. Conclusions Without the need to identify and eliminate the phases of gait initiation and termination, twenty strides can provide a reasonable amount of information to reliably estimate gait regularity in transfemoral amputees. PMID:22316184

Treadmill locomotion of the mouse lemur (Microcebus murinus); kinematic parameters during symmetrical and asymmetrical gaits.

PubMed

Herbin, Marc; Hommet, Eva; Hanotin-Dossot, Vicky; Perret, Martine; Hackert, Rémi

2018-06-01

The gaits of the adult grey mouse lemur Microcebus murinus were studied during treadmill locomotion over a large range of velocities. The locomotion sequences were analysed to determine the gait and the various spatiotemporal gait parameters of the limbs. We found that velocity adjustments are accounted for differently by stride frequency and stride length depending on whether the animal showed a symmetrical or an asymmetrical gait. When using symmetrical gaits the increase in velocity is associated with a constant contribution of the stride length and stride frequency; the increase of the stride frequency being always lower. When using asymmetrical gaits, the increase in velocity is mainly assured by an increase in the stride length which tends to decrease with increasing velocity. A reduction in both stance time and swing time contributed to the increase in stride frequency for both gaits, though with a major contribution from the decrease in stance time. The pattern of locomotion obtained in a normal young adult mouse lemurs can be used as a template for studying locomotor control deficits during aging or in different environments such as arboreal ones which likely modify the kinematics of locomotion.

The Effects of Music Salience on the Gait Performance of Young Adults.

PubMed

de Bruin, Natalie; Kempster, Cody; Doucette, Angelica; Doan, Jon B; Hu, Bin; Brown, Lesley A

2015-01-01

The presence of a rhythmic beat in the form of a metronome tone or beat-accentuated original music can modulate gait performance; however, it has yet to be determined whether gait modulation can be achieved using commercially available music. The current study investigated the effects of commercially available music on the walking of healthy young adults. Specific aims were (a) to determine whether commercially available music can be used to influence gait (i.e., gait velocity, stride length, cadence, stride time variability), (b) to establish the effect of music salience on gait (i.e., gait velocity, stride length, cadence, stride time variability), and (c) to examine whether music tempi differentially effected gait (i.e., gait velocity, stride length, cadence, stride time variability). Twenty-five participants walked the length of an unobstructed walkway while listening to music. Music selections differed with respect to the salience or the tempo of the music. The genre of music and artists were self-selected by participants. Listening to music while walking was an enjoyable activity that influenced gait. Specifically, salient music selections increased measures of cadence, velocity, and stride length; in contrast, gait was unaltered by the presence of non-salient music. Music tempo did not differentially affect gait performance (gait velocity, stride length, cadence, stride time variability) in these participants. Gait performance was differentially influenced by music salience. These results have implications for clinicians considering the use of commercially available music as an alternative to the traditional rhythmic auditory cues used in rehabilitation programs. © the American Music Therapy Association 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The influence of minimalist footwear and stride length reduction on lower-extremity running mechanics and cumulative loading.

PubMed

Firminger, Colin R; Edwards, W Brent

2016-12-01

To examine the effects of shoe type and stride length reduction on lower-extremity running mechanics and cumulative loading. Within-subject with four conditions: (1) control shoe at preferred stride length; (2) control shoe at 90% preferred stride length; (3) minimalist shoe at preferred stride length; (4) minimalist shoe at 90% preferred stride length. Fourteen young healthy males ran overground at their preferred speed while motion capture, force platform, and plantar pressure data were collected. Peak moments, impulse, mechanical work, and cumulative impulse were calculated at the metatarsophalangeal, ankle, and knee joint, and compared between conditions using a 2×2 factor repeated measures ANOVA. In general, running in minimalist footwear increased measures of loading at the metatarsophalangeal joint and ankle joint (mean increases of 7.3% and 5.9%, respectively), but decreased measures of loading at the knee (mean decrease of 7.3%). Conversely, running with reduced stride length decreased single-stance measures of loading at the ankle and knee joint (ranging from -0.9% to -20.5%), though cumulative impulse was higher at the ankle and lower at the knee. Running in minimalist shoes increased loads at the metatarsophalangeal and ankle joint, which may explain some of the incidence of overuse injuries observed in minimalist shoe users. Decreased ankle loads at 90% preferred stride length were not necessarily sufficient to reduce cumulative loads when impulse and loading cycles were weighted equally. Knee loads decreased more when running at 90% preferred stride length (16.2% mean reduction) versus running in a minimalist shoe (7.3% mean reduction), but both load reduction mechanisms appeared to have an additive effect (22.2% mean reduction). Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

The Evolution of Neuroprosthetic Interfaces

PubMed Central

Adewole, Dayo O.; Serruya, Mijail D.; Harris, James P.; Burrell, Justin C.; Petrov, Dmitriy; Chen, H. Isaac; Wolf, John A.; Cullen, D. Kacy

2017-01-01

The ideal neuroprosthetic interface permits high-quality neural recording and stimulation of the nervous system while reliably providing clinical benefits over chronic periods. Although current technologies have made notable strides in this direction, significant improvements must be made to better achieve these design goals and satisfy clinical needs. This article provides an overview of the state of neuroprosthetic interfaces, starting with the design and placement of these interfaces before exploring the stimulation and recording platforms yielded from contemporary research. Finally, we outline emerging research trends in an effort to explore the potential next generation of neuroprosthetic interfaces. PMID:27652455

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bosler, Peter A.; Roesler, Erika L.; Taylor, Mark A.

This study discusses the problem of identifying extreme climate events such as intense storms within large climate data sets. The basic storm detection algorithm is reviewed, which splits the problem into two parts: a spatial search followed by a temporal correlation problem. Two specific implementations of the spatial search algorithm are compared: the commonly used grid point search algorithm is reviewed, and a new algorithm called Stride Search is introduced. The Stride Search algorithm is defined independently of the spatial discretization associated with a particular data set. Results from the two algorithms are compared for the application of tropical cyclonemore » detection, and shown to produce similar results for the same set of storm identification criteria. Differences between the two algorithms arise for some storms due to their different definition of search regions in physical space. The physical space associated with each Stride Search region is constant, regardless of data resolution or latitude, and Stride Search is therefore capable of searching all regions of the globe in the same manner. Stride Search's ability to search high latitudes is demonstrated for the case of polar low detection. Wall clock time required for Stride Search is shown to be smaller than a grid point search of the same data, and the relative speed up associated with Stride Search increases as resolution increases.« less

[Kinetics of heifers and cows walking on an instrumented treadmill].

PubMed

Nuss, K; Waldern, N M; Weishaupt, M A; Wiestner, T

2015-01-01

Kinetic data of stride characteristics and ground reaction forces of cattle become increasingly important as automated lameness detection may be installed in dairy cow housing systems in the future. Therefore, sound heifers and cows were measured on an instrumented treadmill to collect such basic data. Nine heifers and 10 cows were trained to walk on an instrumented treadmill. Vertical ground reaction forces as well as step and stride timing and length variables were measured for all limbs simultaneously. On average, 16 stride cycles in cows and 24 strides in heifers were analysed in each case. The cows walked on the treadmill at an average speed of 1.2 ± 0.05 m/s (mean ± standard deviation), with a stride rate of 43.0 ± 1.9/min and a stride length of 1.68 ± 0.1 m. The heifers had average values of 1.3 ± 0.04 m/s, 53.7 ± 2.2/min and 1.49 ± 0.05 m, respectively. The stance duration relative to stride duration (the duty factor) was for the cows significantly longer in the forelimbs (67%) than in the hind limbs (64%). Force-time-curves of all limbs showed two peaks, one after landing (FP1) and another during push off (FP2). Vertical ground reaction force was highest for FP1 in the hind limbs, but for FP2 in the forelimbs. At all limbs, force minimum between the peaks occurred shortly before midstance. The vertical impulse carried by both forelimbs amounted to 53.7% of the total stride impulse in cows and to 55.0% in heifers. The location of the centre of body mass varied during the stride cycle but was always located more towards the front limbs. Cows and heifers showed a symmetrical walk with minimal intra-individual variations. Relative stride impulse of the front limbs was higher than that of the hind limbs. Peak vertical force in the hind limbs was highest at landing and in the forelimbs at push off. The present study offers kinetic data of sound cows and heifers which might be helpful as guidelines for automated systems for lameness detection in cattle.

Changes in Knee Biomechanics After a Hip-Abductor Strengthening Protocol for Runners With Patellofemoral Pain Syndrome

PubMed Central

Ferber, Reed; Kendall, Karen D.; Farr, Lindsay

2011-01-01

Abstract Context: Very few authors have investigated the relationship between hip-abductor muscle strength and frontal-plane knee mechanics during running. Objective: To investigate this relationship using a 3-week hip-abductor muscle-strengthening program to identify changes in strength, pain, and biomechanics in runners with patellofemoral pain syndrome (PFPS). Design: Cohort study. Setting: University-based clinical research laboratory. Patients or Other Participants: Fifteen individuals (5 men, 10 women) with PFPS and 10 individuals without PFPS (4 men, 6 women) participated. Intervention(s): The patients with PFPS completed a 3-week hip-abductor strengthening protocol; control participants did not. Main Outcome Measure(s): The dependent variables of interest were maximal isometric hip-abductor muscle strength, 2-dimensional peak knee genu valgum angle, and stride-to-stride knee-joint variability. All measures were recorded at baseline and 3 weeks later. Between-groups differences were compared using repeated-measures analyses of variance. Results: At baseline, the PFPS group exhibited reduced strength, no difference in peak genu valgum angle, and increased stride-to-stride knee-joint variability compared with the control group. After the 3-week protocol, the PFPS group demonstrated increased strength, less pain, no change in peak genu valgum angle, and reduced stride-to-stride knee-joint variability compared with baseline. Conclusions: A 3-week hip-abductor muscle-strengthening protocol was effective in increasing muscle strength and decreasing pain and stride-to-stride knee-joint variability in individuals with PFPS. However, concomitant changes in peak knee genu valgum angle were not observed. PMID:21391799

The Stride Rite Intergenerational Day Care Center: Background.

ERIC Educational Resources Information Center

Stride Rite Corp., Cambridge, MA.

The Stride Rite Intergenerational Day Care Center is located in the Stride Rite Corporation's headquarters in Cambridge, Massachusetts. The facility is designed to provide day care to both children and elders, using two separate wings to afford privacy to each group and a large central area for informal interaction between children and elders. The…

STRIDE: Species Tree Root Inference from Gene Duplication Events.

PubMed

Emms, David M; Kelly, Steven

2017-12-01

The correct interpretation of any phylogenetic tree is dependent on that tree being correctly rooted. We present STRIDE, a fast, effective, and outgroup-free method for identification of gene duplication events and species tree root inference in large-scale molecular phylogenetic analyses. STRIDE identifies sets of well-supported in-group gene duplication events from a set of unrooted gene trees, and analyses these events to infer a probability distribution over an unrooted species tree for the location of its root. We show that STRIDE correctly identifies the root of the species tree in multiple large-scale molecular phylogenetic data sets spanning a wide range of timescales and taxonomic groups. We demonstrate that the novel probability model implemented in STRIDE can accurately represent the ambiguity in species tree root assignment for data sets where information is limited. Furthermore, application of STRIDE to outgroup-free inference of the origin of the eukaryotic tree resulted in a root probability distribution that provides additional support for leading hypotheses for the origin of the eukaryotes. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Project Stride: An Equine-Assisted Intervention to Reduce Symptoms of Social Anxiety in Young Women.

PubMed

Alfonso, Sarah V; Alfonso, Lauren A; Llabre, Maria M; Fernandez, M Isabel

2015-01-01

Although there is evidence supporting the use of equine-assisted activities to treat mental disorders, its efficacy in reducing signs and symptoms of social anxiety in young women has not been examined. We developed and pilot tested Project Stride, a brief, six-session intervention combining equine-assisted activities and cognitive-behavioral strategies to reduce symptoms of social anxiety. A total of 12 women, 18-29 years of age, were randomly assigned to Project Stride or a no-treatment control. Participants completed the Liebowitz Social Anxiety Scale at baseline, immediate-post, and 6 weeks after treatment. Project Stride was highly acceptable and feasible. Compared to control participants, those in Project Stride had significantly greater reductions in social anxiety scores from baseline to immediate-post [decrease of 24.8 points; t (9) = 3.40, P = .008)] and from baseline to follow-up [decrease of 31.8 points; t (9) = 4.12, P = .003)]. These findings support conducting a full-scale efficacy trial of Project Stride. Copyright © 2015 Elsevier Inc. All rights reserved.

Estimation of spatial-temporal gait parameters using a low-cost ultrasonic motion analysis system.

PubMed

Qi, Yongbin; Soh, Cheong Boon; Gunawan, Erry; Low, Kay-Soon; Thomas, Rijil

2014-08-20

In this paper, a low-cost motion analysis system using a wireless ultrasonic sensor network is proposed and investigated. A methodology has been developed to extract spatial-temporal gait parameters including stride length, stride duration, stride velocity, stride cadence, and stride symmetry from 3D foot displacements estimated by the combination of spherical positioning technique and unscented Kalman filter. The performance of this system is validated against a camera-based system in the laboratory with 10 healthy volunteers. Numerical results show the feasibility of the proposed system with average error of 2.7% for all the estimated gait parameters. The influence of walking speed on the measurement accuracy of proposed system is also evaluated. Statistical analysis demonstrates its capability of being used as a gait assessment tool for some medical applications.

Detrended Fluctuation Analysis and Adaptive Fractal Analysis of Stride Time Data in Parkinson's Disease: Stitching Together Short Gait Trials

PubMed Central

Liebherr, Magnus; Haas, Christian T.

2014-01-01

Variability indicates motor control disturbances and is suitable to identify gait pathologies. It can be quantified by linear parameters (amplitude estimators) and more sophisticated nonlinear methods (structural information). Detrended Fluctuation Analysis (DFA) is one method to measure structural information, e.g., from stride time series. Recently, an improved method, Adaptive Fractal Analysis (AFA), has been proposed. This method has not been applied to gait data before. Fractal scaling methods (FS) require long stride-to-stride data to obtain valid results. However, in clinical studies, it is not usual to measure a large number of strides (e.g., strides). Amongst others, clinical gait analysis is limited due to short walkways, thus, FS seem to be inapplicable. The purpose of the present study was to evaluate FS under clinical conditions. Stride time data of five self-paced walking trials ( strides each) of subjects with PD and a healthy control group (CG) was measured. To generate longer time series, stride time sequences were stitched together. The coefficient of variation (CV), fractal scaling exponents (DFA) and (AFA) were calculated. Two surrogate tests were performed: A) the whole time series was randomly shuffled; B) the single trials were randomly shuffled separately and afterwards stitched together. CV did not discriminate between PD and CG. However, significant differences between PD and CG were found concerning and . Surrogate version B yielded a higher mean squared error and empirical quantiles than version A. Hence, we conclude that the stitching procedure creates an artificial structure resulting in an overestimation of true . The method of stitching together sections of gait seems to be appropriate in order to distinguish between PD and CG with FS. It provides an approach to integrate FS as standard in clinical gait analysis and to overcome limitations such as short walkways. PMID:24465708

The influence of lower limb amputation level on the approach in the amputee long jump.

PubMed

Nolan, Lee; Lees, Adrian

2007-02-15

In this study, we investigated the adjustments to posture, kinematic and temporal characteristics of performance made by lower limb amputees during the last few strides in preparation for long jump take-off. Six male unilateral trans-femoral and seven male unilateral trans-tibial amputees competing in a World Championships final were filmed in the sagittal plane using a 100-Hz digital video camera positioned so that the last three strides to take-off were visible. After digitizing using a nine-segment model, a range of kinematic variables were computed to define technique characteristics. Both the trans-femoral and trans-tibial athletes appeared to achieve their reduction in centre of mass during the flight phase between strides, and did so mainly by extending the flight time by increasing stride length, achieved by a greater flexion of the hip joint of the touch-down leg. The trans-tibial athletes appeared to adopt a technique similar to that previously reported for able-bodied athletes. They lowered their centre of mass most on their second last stride (-1.6% of body height compared with -1.4% on the last stride) and used a flexed knee at take-off on the last stride, but they were less able to control their downward velocity at touch-down (-0.4 m x s(-1)). Both this and their restricted approach speed (8.9 m x s(-1) at touch-down), rather than technique limitations, influenced their jump performance. The trans-femoral athletes lowered their centre of mass most on the last stride (-2.3% of body height compared with -1.6% on the second last stride) and, as they were unable to flex their prosthetic knee sufficiently, achieved this by abducting their prosthetic leg during the support phase, which led to a large downward velocity at touch-down (-0.6 m x s(-1)). This, combined with their slower approach velocity (7.1 m x s(-1) at touch-down), restricted their performance.

Stride-to-stride variability and complexity between novice and experienced runners during a prolonged run at anaerobic threshold speed.

PubMed

Mo, Shiwei; Chow, Daniel H K

2018-05-19

Motor control, related to running performance and running related injuries, is affected by progression of fatigue during a prolonged run. Distance runners are usually recommended to train at or slightly above anaerobic threshold (AT) speed for improving performance. However, running at AT speed may result in accelerated fatigue. It is not clear how one adapts running gait pattern during a prolonged run at AT speed and if there are differences between runners with different training experience. To compare characteristics of stride-to-stride variability and complexity during a prolonged run at AT speed between novice runners (NR) and experienced runners (ER). Both NR (n = 17) and ER (n = 17) performed a treadmill run for 31 min at his/her AT speed. Stride interval dynamics was obtained throughout the run with the middle 30 min equally divided into six time intervals (denoted as T1, T2, T3, T4, T5 and T6). Mean, coefficient of variation (CV) and scaling exponent alpha of stride intervals were calculated for each interval of each group. This study revealed mean stride interval significantly increased with running time in a non-linear trend (p<0.001). The stride interval variability (CV) maintained relatively constant for NR (p = 0.22) and changed nonlinearly for ER (p = 0.023) throughout the run. Alpha was significantly different between groups at T2, T5 and T6, and nonlinearly changed with running time for both groups with slight differences. These findings provided insights into how the motor control system adapts to progression of fatigue and evidences that long-term training enhances motor control. Although both ER and NR could regulate gait complexity to maintain AT speed throughout the prolonged run, ER also regulated stride interval variability to achieve the goal. Copyright © 2018. Published by Elsevier B.V.

Water reservoir maintained by cell growth fuels the spreading of a bacterial swarm

PubMed Central

Wu, Yilin; Berg, Howard C.

2012-01-01

Flagellated bacteria can swim across moist surfaces within a thin layer of fluid, a means for surface colonization known as swarming. This fluid spreads with the swarm, but how it does so is unclear. We used micron-sized air bubbles to study the motion of this fluid within swarms of Escherichia coli. The bubbles moved diffusively, with drift. Bubbles starting at the swarm edge drifted inward for the first 5 s and then moved outward. Bubbles starting 30 μm from the swarm edge moved inward for the first 20 s, wandered around in place for the next 40 s, and then moved outward. Bubbles starting at 200 or 300 μm from the edge moved outward or wandered around in place, respectively. So the general trend was inward near the outer edge of the swarm and outward farther inside, with flows converging on a region about 100 μm from the swarm edge. We measured cellular metabolic activities with cells expressing a short-lived GFP and cell densities with cells labeled with a membrane fluorescent dye. The fluorescence plots were similar, with peaks about 80 μm from the swarm edge and slopes that mimicked the particle drift rates. These plots suggest that net fluid flow is driven by cell growth. Fluid depth is largest in the multilayered region between approximately 30 and 200 μm from the swarm edge, where fluid agitation is more vigorous. This water reservoir travels with the swarm, fueling its spreading. Intercellular communication is not required; cells need only grow. PMID:22371567

Water reservoir maintained by cell growth fuels the spreading of a bacterial swarm.

PubMed

Wu, Yilin; Berg, Howard C

2012-03-13

Flagellated bacteria can swim across moist surfaces within a thin layer of fluid, a means for surface colonization known as swarming. This fluid spreads with the swarm, but how it does so is unclear. We used micron-sized air bubbles to study the motion of this fluid within swarms of Escherichia coli. The bubbles moved diffusively, with drift. Bubbles starting at the swarm edge drifted inward for the first 5 s and then moved outward. Bubbles starting 30 μm from the swarm edge moved inward for the first 20 s, wandered around in place for the next 40 s, and then moved outward. Bubbles starting at 200 or 300 μm from the edge moved outward or wandered around in place, respectively. So the general trend was inward near the outer edge of the swarm and outward farther inside, with flows converging on a region about 100 μm from the swarm edge. We measured cellular metabolic activities with cells expressing a short-lived GFP and cell densities with cells labeled with a membrane fluorescent dye. The fluorescence plots were similar, with peaks about 80 μm from the swarm edge and slopes that mimicked the particle drift rates. These plots suggest that net fluid flow is driven by cell growth. Fluid depth is largest in the multilayered region between approximately 30 and 200 μm from the swarm edge, where fluid agitation is more vigorous. This water reservoir travels with the swarm, fueling its spreading. Intercellular communication is not required; cells need only grow.

Manipulating the stride length/stride velocity relationship of walking using a treadmill and rhythmic auditory cueing in non-disabled older individuals. A short-term feasibility study.

PubMed

Eikema, D J A; Forrester, L W; Whitall, J

2014-09-01

One target for rehabilitating locomotor disorders in older adults is to increase mobility by improving walking velocity. Combining rhythmic auditory cueing (RAC) and treadmill training permits the study of the stride length/stride velocity ratio (SL/SV), often reduced in those with mobility deficits. We investigated the use of RAC to increase velocity by manipulating the SL/SV ratio in older adults. Nine participants (6 female; age: 61.1 ± 8.8 years) walked overground on a gait mat at preferred and fast speeds. After acclimatization to comfortable speed on a treadmill, participants adjusted their cadence to match the cue for 3 min at 115% of preferred speed by either (a) increasing stride length only or (b) increasing stride frequency only. Following training, participants walked across the gait mat at preferred velocity without, and then with, RAC. Group analysis determined no immediate overground velocity increase, but reintroducing RAC did produce an increase in velocity after both conditions. Group and single subject analysis determined that the SL/SV ratio changed in the intended direction only in the stride length condition. We conclude that RAC is a powerful organizer of gait parameters, evidenced by its induced after-effects following short duration training. Copyright © 2014 Elsevier B.V. All rights reserved.

Assessment of repeatability of a wireless, inertial sensor-based lameness evaluation system for horses.

PubMed

Keegan, Kevin G; Kramer, Joanne; Yonezawa, Yoshiharu; Maki, Hiromitchi; Pai, P Frank; Dent, Eric V; Kellerman, Thomas E; Wilson, David A; Reed, Shannon K

2011-09-01

To determine repeatability of a wireless, inertial sensor-based lameness evaluation system in horses. 236 horses. Horses were from 2 to 29 years of age and of various breeds and lameness disposition. All horses were instrumented with a wireless, inertial sensor-based motion analysis system on the head (accelerometer), pelvis (midline croup region [accelerometer]), and right forelimb (gyroscope) before evaluation in 2 consecutive trials, approximately 5 minutes apart, as the horse was trotted in a straight line. Signal-processing algorithms generated overall trial asymmetry measures for vertical head and pelvic movement and stride-by-stride differences in head and pelvic maximum and minimum positions between right and left sides of each stride. Repeatability was determined, and trial difference was determined for groups of horses with various numbers of strides for which data were collected per trial. Inertial sensor-based measures of torso movement asymmetry were repeatable. Repeatability for measures of torso asymmetry for determination of hind limb lameness was slightly greater than that for forelimb lameness. Collecting large numbers of strides degraded stride-to-stride repeatability but did not degrade intertrial repeatability. The inertial sensor system used to measure asymmetry of head and pelvic movement as an aid in the detection and evaluation of lameness in horses trotting in a straight line was sufficiently repeatable to investigate for clinical use.

Kinematic Mechanisms of How Power Training Improves Healthy Old Adults' Gait Velocity.

PubMed

Beijersbergen, Chantal M I; Granacher, Urs; Gäbler, Martijn; Devita, Paul; Hortobágyi, Tibor

2017-01-01

Slow gait predicts many adverse clinical outcomes in old adults, but the mechanisms of how power training can minimize the age-related loss of gait velocity is unclear. We examined the effects of 10 wk of lower extremity power training and detraining on healthy old adults' lower extremity muscle power and gait kinematics. As part of the Potsdam Gait Study, participants started with 10 wk of power training followed by 10 wk of detraining (n = 16), and participants started with a 10-wk control period followed by 10 wk of power training (n = 16). We measured gait kinematics (stride characteristic and joint kinematics) and isokinetic power of the ankle plantarflexor (20°·s, 40°·s, and 60°·s) and knee extensor and flexor (60°·s, 120°·s, and 180°·s) muscles at weeks 0, 10, and 20. Power training improved isokinetic muscle power by ~30% (P ≤ 0.001) and fast (5.9%, P < 0.05) but not habitual gait velocity. Ankle plantarflexor velocity measured during gait at fast pace decreased by 7.9% (P < 0.05). The changes isokinetic muscle power and joint kinematics did not correlate with increases in fast gait velocity. The mechanisms that increased fast gait velocity involved higher cadence (r = 0.86, P ≤ 0.001) rather than longer strides (r = 0.49, P = 0.066). Detraining did not reverse the training-induced increases in muscle power and fast gait velocity. Because increases in muscle power and modifications in joint kinematics did not correlate with increases in fast gait velocity, kinematic mechanisms seem to play a minor role in improving healthy old adults' fast gait velocity after power training.

Transfer effects of fall training on balance performance and spatiotemporal gait parameters in healthy community-dwelling older adults: a pilot study.

PubMed

Donath, Lars; Faude, Oliver; Bridenbaugh, Stephanie A; Roth, Ralf; Soltermann, Martin; Kressig, Reto W; Zahner, Lukas

2014-07-01

This study examined transfer effects of fall training on fear of falling (Falls Efficacy Scale-International [FES-I]), balance performance, and spatiotemporal gait characteristics in older adults. Eighteen community-dwelling older adults (ages 65-85) were randomly assigned to an intervention or control group. The intervention group completed 12 training sessions (60 min, 6 weeks). During pre- and posttesting, we measured FES-I, balance performance (double limb, closed eyes; single limb, open eyes; double limb, open eyes with motor-interfered task), and gait parameters (e.g., velocity; cadence; stride time, stride width, and stride length; variability of stride time and stride length) under single- and motor-interfered tasks. Dual tasks were applied to appraise improvements of cognitive processing during balance and gait. FES-I (p = .33) and postural sway did not significantly change (0.36 < p < .79). Trends toward significant interaction effects were found for step width during normal walking and stride length variability during the motor dual task (p = .05, ηp 2 = .22). Fall training did not sufficiently improve fear of falling, balance, or gait performance under single- or dual-task conditions in healthy older adults.

Aerodynamics of dynamic wing flexion in translating wings

NASA Astrophysics Data System (ADS)

Liu, Yun; Cheng, Bo; Sane, Sanjay P.; Deng, Xinyan

2015-06-01

We conducted a systematic experimental study to investigate the aerodynamic effects of active trailing-edge flexion on a high-aspect-ratio wing translating from rest at a high angle of attack. We varied the timing and speed of the trailing-edge flexion and measured the resulting aerodynamic effects using a combination of direct force measurements and two-dimensional PIV flow measurements. The results indicated that the force and flow characteristics depend strongly on the timing of flexion, but relatively weakly on its speed. This is because the force and vortical flow structure are more sensitive to the timing of flexion relative to the shedding of starting vortex and leading-edge vortex. When the trailing-edge flexion occurred slightly before the starting vortex was shed, the lift production was greatly improved with the instantaneous peak lift increased by 54 % and averaged lift increased by 21 % compared with the pre-flexed case where the trailing-edge flexed before wing translation. However, when the trailing-edge flexed during or slightly after the leading-edge vortex shedding, the lift was significantly reduced by the disturbed development of leading-edge vortex. The force measurement results also imply that the trailing-edge flexion prior to wing translation does not augment lift but increases drag, thus resulting in a lower lift-drag ratio as compared to the case of flat wing.

Leg stiffness and stride frequency in human running.

PubMed

Farley, C T; González, O

1996-02-01

When humans and other mammals run, the body's complex system of muscle, tendon and ligament springs behaves like a single linear spring ('leg spring'). A simple spring-mass model, consisting of a single linear leg spring and a mass equivalent to the animal's mass, has been shown to describe the mechanics of running remarkably well. Force platform measurements from running animals, including humans, have shown that the stiffness of the leg spring remains nearly the same at all speeds and that the spring-mass system is adjusted for higher speeds by increasing the angle swept by the leg spring. The goal of the present study is to determine the relative importance of changes to the leg spring stiffness and the angle swept by the leg spring when humans alter their stride frequency at a given running speed. Human subjects ran on treadmill-mounted force platform at 2.5ms-1 while using a range of stride frequencies from 26% below to 36% above the preferred stride frequency. Force platform measurements revealed that the stiffness of the leg spring increased by 2.3-fold from 7.0 to 16.3 kNm-1 between the lowest and highest stride frequencies. The angle swept by the leg spring decreased at higher stride frequencies, partially offsetting the effect of the increased leg spring stiffness on the mechanical behavior of the spring-mass system. We conclude that the most important adjustment to the body's spring system to accommodate higher stride frequencies is that leg spring becomes stiffer.

Building corporate character. Interview by Nan Stone.

PubMed

Hiatt, A

1992-01-01

Stride Rite is a good company by any definition: Keds, Sperry Top-Siders, and Stride Rite children's shoes are consumer favorites for their fit, quality, and comfort. Wall Street analysts praise the company's outstanding financial performance. Innovative programs such as the first corporate child-care center and public service scholarships support Stride Rite's reputation as one of the most responsible employers and corporate citizens in the United States. Behind Stride Rite's good performance are the building blocks of corporate character: a legacy of quality and service and a leader committed to keeping that legacy lively. When Stride Rite shipped its first children's shoes in 1919, they came with the company's commitment "to produce an honest quality product in an honest way and deliver it as promised." For Arnold Hiatt, that commitment has been the driving force behind the company's evolution from manufacturing into marketing and product development as well as the guiding principle in its relations with consumers, dealers, suppliers, and employees. But Stride Rite's corporate character is also a reflection of Hiatt himself. In his early 20s, Hiatt fled a management training program "designed to make carnivores" out of its new employees and bought Blue Star Shoes, a small manufacturing company that had gone into Chapter 11. Through experience and "stumbling around," he built Blue Star's sales to $5 million-and got a practical education in management, markets, and human nature that has proved equally useful in running Stride Rite.

Community Literacy at Work with STRIDE (Success Through Reading Improvement and DEvelopment): Overview of a Successful Community Literacy Program.

ERIC Educational Resources Information Center

Macy, Rita

STRIDE (Success Through Reading Improvement and DEvelopment) is a literacy program developed in 1986 by Crowder College, located in the rural Ozarks of southwestern Missouri. Serving all age groups with trained literacy tutors ranging in age from 11 to over 60, STRIDE has been built on five main activities: (1) develop a philosophy that is…

Abnormal gait pattern emerges during curved trajectories in high-functioning Parkinsonian patients walking in line at normal speed

PubMed Central

Godi, Marco; Giardini, Marica; Arcolin, Ilaria; Nardone, Antonio; Giordano, Andrea; Schieppati, Marco

2018-01-01

Background Several patients with Parkinson´s disease (PD) can walk normally along straight trajectories, and impairment in their stride length and cadence may not be easily discernible. Do obvious abnormalities occur in these high-functioning patients when more challenging trajectories are travelled, such as circular paths, which normally implicate a graded modulation in the duration of the interlimb gait cycle phases? Methods We compared a cohort of well-treated mildly to moderately affected PD patients to a group of age-matched healthy subjects (HS), by deliberately including HS spontaneously walking at the same speed of the patients with PD. All participants performed, in random order: linear and circular walking (clockwise and counter-clockwise) at self-selected speed. By means of pressure-sensitive insoles, we recorded walking speed, cadence, duration of single support, double support, swing phase, and stride time. Stride length-cadence relationships were built for linear and curved walking. Stride-to-stride variability of temporal gait parameters was also estimated. Results Walking speed, cadence or stride length were not different between PD and HS during linear walking. Speed, cadence and stride length diminished during curved walking in both groups, stride length more in PD than HS. In PD compared to HS, the stride length-cadence relationship was altered during curved walking. Duration of the double-support phase was also increased during curved walking, as was variability of the single support, swing phase and double support phase. Conclusion The spatio-temporal gait pattern and variability are significantly modified in well-treated, high-functioning patients with PD walking along circular trajectories, even when they exhibit no changes in speed in straight-line walking. The increased variability of the gait phases during curved walking is an identifying characteristic of PD. We discuss our findings in term of interplay between control of balance and of locomotor progression: the former is challenged by curved trajectories even in high-functioning patients, while the latter may not be critically affected. PMID:29750815

Effects of roughness and compressibility of flooring on cow locomotion.

PubMed

Rushen, J; de Passillé, A M

2006-08-01

We examined the effects of roughness and degree of compressibility of flooring on the locomotion of dairy cows. We observed 16 cows walking down specially constructed walkways with materials that differed in surface roughness and degree of compressibility. Use of a commercially available soft rubber flooring material decreased slipping, number of strides, and time to traverse the corridor. These effects were most apparent at difficult sections of the corridor, such as at the start, at a right-angle turn, and across a gutter. Covering the walkway with a thin layer of slurry increased frequency of slipping, number of strides, and time taken to traverse the walkway. Effects of adding slurry were not overcome by increasing surface roughness or compressibility. Placing more compressible materials under a slip-resistant material reduced the time and number of steps needed to traverse the corridor but did not reduce slips, and the effects on cow locomotion varied nonlinearly with the degree of compressibility of the floor. Use of commercially available rubber floors improved cow locomotion compared with concrete floors. However, standard engineering measures of the floor properties may not predict effects of the floor on cow behavior well. Increasing compressibility of the flooring on which cows walk, independently of the roughness of the surface, can improve cow locomotion.

Effect of stride length on overarm throwing delivery: A linear momentum response.

PubMed

Ramsey, Dan K; Crotin, Ryan L; White, Scott

2014-12-01

Changing stride length during overhand throwing delivery is thought to alter total body and throwing arm linear momentums, thereby altering the proportion of throwing arm momentum relative to the total body. Using a randomized cross-over design, nineteen pitchers (15 collegiate and 4 high school) were assigned to pitch two simulated 80-pitch games at ±25% of their desired stride length. An 8-camera motion capture system (240Hz) integrated with two force plates (960Hz) and radar gun tracked each throw. Segmental linear momentums in each plane of motion were summed yielding throwing arm and total body momentums, from which compensation ratio's (relative contribution between the two) were derived. Pairwise comparisons at hallmark events and phases identified significantly different linear momentum profiles, in particular, anteriorly directed total body, throwing arm, and momentum compensation ratios (P⩽.05) as a result of manipulating stride length. Pitchers with shorter strides generated lower forward (anterior) momentum before stride foot contact, whereas greater upward and lateral momentum (toward third base) were evident during the acceleration phase. The evidence suggests insufficient total body momentum in the intended throwing direction may potentially influence performance (velocity and accuracy) and perhaps precipitate throwing arm injuries. Copyright © 2014 Elsevier B.V. All rights reserved.

Day-to-day reliability of gait characteristics in rats.

PubMed

Raffalt, Peter C; Nielsen, Louise R; Madsen, Stefan; Munk Højberg, Laurits; Pingel, Jessica; Nielsen, Jens Bo; Wienecke, Jacob; Alkjær, Tine

2018-04-27

The purpose of the present study was to determine the day-to-day reliability in stride characteristics in rats during treadmill walking obtained with two-dimensional (2D) motion capture. Kinematics were recorded from 26 adult rats during walking at 8 m/min, 12 m/min and 16 m/min on two separate days. Stride length, stride time, contact time, swing time and hip, knee and ankle joint range of motion were extracted from 15 strides. The relative reliability was assessed using intra-class correlation coefficients (ICC(1,1)) and (ICC(3,1)). The absolute reliability was determined using measurement error (ME). Across walking speeds, the relative reliability ranged from fair to good (ICCs between 0.4 and 0.75). The ME was below 91 mm for strides lengths, below 55 ms for the temporal stride variables and below 6.4° for the joint angle range of motion. In general, the results indicated an acceptable day-to-day reliability of the gait pattern parameters observed in rats during treadmill walking. The results of the present study may serve as a reference material that can help future intervention studies on rat gait characteristics both with respect to the selection of outcome measures and in the interpretation of the results. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of footwear and stride length on metatarsal strains and failure in running.

PubMed

Firminger, Colin R; Fung, Anita; Loundagin, Lindsay L; Edwards, W Brent

2017-11-01

The metatarsal bones of the foot are particularly susceptible to stress fracture owing to the high strains they experience during the stance phase of running. Shoe cushioning and stride length reduction represent two potential interventions to decrease metatarsal strain and thus stress fracture risk. Fourteen male recreational runners ran overground at a 5-km pace while motion capture and plantar pressure data were collected during four experimental conditions: traditional shoe at preferred and 90% preferred stride length, and minimalist shoe at preferred and 90% preferred stride length. Combined musculoskeletal - finite element modeling based on motion analysis and computed tomography data were used to quantify metatarsal strains and the probability of failure was determined using stress-life predictions. No significant interactions between footwear and stride length were observed. Running in minimalist shoes increased strains for all metatarsals by 28.7% (SD 6.4%; p<0.001) and probability of failure for metatarsals 2-4 by 17.3% (SD 14.3%; p≤0.005). Running at 90% preferred stride length decreased strains for metatarsal 4 by 4.2% (SD 2.0%; p≤0.007), and no differences in probability of failure were observed. Significant increases in metatarsal strains and the probability of failure were observed for recreational runners acutely transitioning to minimalist shoes. Running with a 10% reduction in stride length did not appear to be a beneficial technique for reducing the risk of metatarsal stress fracture, however the increased number of loading cycles for a given distance was not detrimental either. Copyright © 2017 Elsevier Ltd. All rights reserved.

A method for automated control of belt velocity changes with an instrumented treadmill.

PubMed

Hinkel-Lipsker, Jacob W; Hahn, Michael E

2016-01-04

Increased practice difficulty during asymmetrical split-belt treadmill rehabilitation has been shown to improve gait outcomes during retention and transfer tests. However, research in this area has been limited by manual treadmill operation. In the case of variable practice, which requires stride-by-stride changes to treadmill belt velocities, the treadmill control must be automated. This paper presents a method for automation of asymmetrical split-belt treadmill walking, and evaluates how well this method performs with regards to timing of gait events. One participant walked asymmetrically for 100 strides, where the non-dominant limb was driven at their self-selected walking speed, while the other limb was driven randomly on a stride-by-stride basis. In the control loop, the key factors to insure that the treadmill belt had accelerated to its new velocity safely during the swing phase were the sampling rate of the A/D converter, processing time within the controller software, and acceleration of the treadmill belt. The combination of these three factors resulted in a total control loop time during each swing phase that satisfied these requirements with a factor of safety that was greater than 4. Further, a polynomial fit indicated that belt acceleration was the largest contributor to changes in this total time. This approach appears to be safe and reliable for stride-by-stride adjustment of treadmill belt speed, making it suitable for future asymmetrical split-belt walking studies. Further, it can be incorporated into virtual reality rehabilitation paradigms that utilize split-belt treadmill walking. Copyright © 2015 Elsevier Ltd. All rights reserved.

Locomotor-respiratory coupling patterns and oxygen consumption during walking above and below preferred stride frequency.

PubMed

O'Halloran, Joseph; Hamill, Joseph; McDermott, William J; Remelius, Jebb G; Van Emmerik, Richard E A

2012-03-01

Locomotor respiratory coupling patterns in humans have been assessed on the basis of the interaction between different physiological and motor subsystems; these interactions have implications for movement economy. A complex and dynamical systems framework may provide more insight than entrainment into the variability and adaptability of these rhythms and their coupling. The purpose of this study was to investigate the relationship between steady state locomotor-respiratory coordination dynamics and oxygen consumption [Formula: see text] of the movement by varying walking stride frequency from preferred. Twelve male participants walked on a treadmill at a self-selected speed. Stride frequency was varied from -20 to +20% of preferred stride frequency (PSF) while respiratory airflow, gas exchange variables, and stride kinematics were recorded. Discrete relative phase and return map techniques were used to evaluate the strength, stability, and variability of both frequency and phase couplings. Analysis of [Formula: see text] during steady-state walking showed a U-shaped response (P = 0.002) with a minimum at PSF and PSF - 10%. Locomotor-respiratory frequency coupling strength was not greater (P = 0.375) at PSF than any other stride frequency condition. The dominant coupling across all conditions was 2:1 with greater occurrences at the lower stride frequencies. Variability in coupling was the greatest during PSF, indicating an exploration of coupling strategies to search for the coupling frequency strategy with the least oxygen consumption. Contrary to the belief that increased strength of frequency coupling would decrease oxygen consumption; these results conclude that it is the increased variability of frequency coupling that results in lower oxygen consumption.

Parkinsonian gait ameliorated with a moving handrail, not with a banister.

PubMed

Rabin, Ely; Demin, Aleksandr; Pirrotta, Stefania; Chen, Jason; Patel, Hemal; Bhambri, Ankur; Noyola, Estella; Lackner, James R; DiZio, Paul; DiFrancisco-Donoghue, Joanne; Werner, William

2015-04-01

To determine whether haptic (touch and proprioception) cues from touching a moving handrail while walking can ameliorate the gait symptoms of Parkinson disease (PD), such as slowness and small stride length. Nonrandomized, controlled before-after trial. Physical therapy clinic. People with PD (n=16) and healthy age-matched control subjects (n=16) with no neurologic disorders volunteered. No participants withdrew. We compared gait using a moving handrail as a novel assistive aid (speed self-selected) versus a banister and unassisted walking. Participants with PD were tested on and off dopaminergic medication. Mean gait speed, stride length, stride duration, double-support duration, and medial-lateral excursion. With the moving handrail, participants with PD increased gait speed relative to unassisted gait by 16% (.166m/s, P=.009, d=.76; 95% confidence interval [CI], .054-.278m/s) and increased stride length by 10% (.053m, P=.022, d=.37; 95% CI, .009-.097m) without significantly changing stride or double-support duration. The banister reduced speed versus unassisted gait by 11% (-.097m/s, P=.040, d=.40; 95% CI, .002-.193m/s) and reduced stride length by 8% (.32m, P=.004, d=.26; 95% CI, .010-.054m), whereas it increased stride duration by 3% (.023s, P=.022, d=.21; 95% CI, .004-.041s) and double-support duration by 35% (.044s, P=.031, d=.58; 95% CI, .005-.083s). All medication × condition interactions were P>.05. Using haptic speed cues from the moving handrail, people with PD walked faster by spontaneously (ie, without specific instruction) increasing stride length without altering cadence; banisters slowed gait. Haptic cues from the moving handrail can be used by people with PD to engage biomechanical and neural mechanisms for interpreting tactile and proprioception changes related to gait speed to control gait better than static cues afforded by banisters. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Smartphone App-Based Assessment of Gait During Normal and Dual-Task Walking: Demonstration of Validity and Reliability.

PubMed

Manor, Brad; Yu, Wanting; Zhu, Hao; Harrison, Rachel; Lo, On-Yee; Lipsitz, Lewis; Travison, Thomas; Pascual-Leone, Alvaro; Zhou, Junhong

2018-01-30

Walking is a complex cognitive motor task that is commonly completed while performing another task such as talking or making decisions. Gait assessments performed under normal and "dual-task" walking conditions thus provide important insights into health. Such assessments, however, are limited primarily to laboratory-based settings. The objective of our study was to create and test a smartphone-based assessment of normal and dual-task walking for use in nonlaboratory settings. We created an iPhone app that used the phone's motion sensors to record movements during walking under normal conditions and while performing a serial-subtraction dual task, with the phone placed in the user's pants pocket. The app provided the user with multimedia instructions before and during the assessment. Acquired data were automatically uploaded to a cloud-based server for offline analyses. A total of 14 healthy adults completed 2 laboratory visits separated by 1 week. On each visit, they used the app to complete three 45-second trials each of normal and dual-task walking. Kinematic data were collected with the app and a gold-standard-instrumented GAITRite mat. Participants also used the app to complete normal and dual-task walking trials within their homes on 3 separate days. Within laboratory-based trials, GAITRite-derived heel strikes and toe-offs of the phone-side leg aligned with smartphone acceleration extrema, following filtering and rotation to the earth coordinate system. We derived stride times-a clinically meaningful metric of locomotor control-from GAITRite and app data, for all strides occurring over the GAITRite mat. We calculated stride times and the dual-task cost to the average stride time (ie, percentage change from normal to dual-task conditions) from both measurement devices. We calculated similar metrics from home-based app data. For these trials, periods of potential turning were identified via custom-developed algorithms and omitted from stride-time analyses. Across all detected strides in the laboratory, stride times derived from the app and GAITRite mat were highly correlated (P<.001, r 2 =.98). These correlations were independent of walking condition and pocket tightness. App- and GAITRite-derived stride-time dual-task costs were also highly correlated (P<.001, r 2 =.95). The error of app-derived stride times (mean 16.9, SD 9.0 ms) was unaffected by the magnitude of stride time, walking condition, or pocket tightness. For both normal and dual-task trials, average stride times derived from app walking trials demonstrated excellent test-retest reliability within and between both laboratory and home-based assessments (intraclass correlation coefficient range .82-.94). The iPhone app we created enabled valid and reliable assessment of stride timing-with the smartphone in the pocket-during both normal and dual-task walking and within both laboratory and nonlaboratory environments. Additional work is warranted to expand the functionality of this tool to older adults and other patient populations. ©Brad Manor, Wanting Yu, Hao Zhu, Rachel Harrison, On-Yee Lo, Lewis Lipsitz, Thomas Travison, Alvaro Pascual-Leone, Junhong Zhou. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 30.01.2018.

Smartphone App–Based Assessment of Gait During Normal and Dual-Task Walking: Demonstration of Validity and Reliability

PubMed Central

Yu, Wanting; Zhu, Hao; Harrison, Rachel; Lo, On-Yee; Lipsitz, Lewis; Travison, Thomas; Pascual-Leone, Alvaro; Zhou, Junhong

2018-01-01

Background Walking is a complex cognitive motor task that is commonly completed while performing another task such as talking or making decisions. Gait assessments performed under normal and “dual-task” walking conditions thus provide important insights into health. Such assessments, however, are limited primarily to laboratory-based settings. Objective The objective of our study was to create and test a smartphone-based assessment of normal and dual-task walking for use in nonlaboratory settings. Methods We created an iPhone app that used the phone’s motion sensors to record movements during walking under normal conditions and while performing a serial-subtraction dual task, with the phone placed in the user’s pants pocket. The app provided the user with multimedia instructions before and during the assessment. Acquired data were automatically uploaded to a cloud-based server for offline analyses. A total of 14 healthy adults completed 2 laboratory visits separated by 1 week. On each visit, they used the app to complete three 45-second trials each of normal and dual-task walking. Kinematic data were collected with the app and a gold-standard–instrumented GAITRite mat. Participants also used the app to complete normal and dual-task walking trials within their homes on 3 separate days. Within laboratory-based trials, GAITRite-derived heel strikes and toe-offs of the phone-side leg aligned with smartphone acceleration extrema, following filtering and rotation to the earth coordinate system. We derived stride times—a clinically meaningful metric of locomotor control—from GAITRite and app data, for all strides occurring over the GAITRite mat. We calculated stride times and the dual-task cost to the average stride time (ie, percentage change from normal to dual-task conditions) from both measurement devices. We calculated similar metrics from home-based app data. For these trials, periods of potential turning were identified via custom-developed algorithms and omitted from stride-time analyses. Results Across all detected strides in the laboratory, stride times derived from the app and GAITRite mat were highly correlated (P<.001, r2=.98). These correlations were independent of walking condition and pocket tightness. App- and GAITRite-derived stride-time dual-task costs were also highly correlated (P<.001, r2=.95). The error of app-derived stride times (mean 16.9, SD 9.0 ms) was unaffected by the magnitude of stride time, walking condition, or pocket tightness. For both normal and dual-task trials, average stride times derived from app walking trials demonstrated excellent test-retest reliability within and between both laboratory and home-based assessments (intraclass correlation coefficient range .82-.94). Conclusions The iPhone app we created enabled valid and reliable assessment of stride timing—with the smartphone in the pocket—during both normal and dual-task walking and within both laboratory and nonlaboratory environments. Additional work is warranted to expand the functionality of this tool to older adults and other patient populations. PMID:29382625

Kinetic and temporospatial gait parameters in a heterogeneous group of dogs.

PubMed

Kano, Washington T; Rahal, Sheila C; Agostinho, Felipe S; Mesquita, Luciane R; Santos, Rogerio R; Monteiro, Frederico O B; Castilho, Maira S; Melchert, Alessandra

2016-01-04

A prime concern of the gait analysis in a heterogeneous group of dogs is the potential influence of factors such as individual body size, body mass, type of gait, and velocity. Thus, this study aimed to evaluate in a heterogeneous group of dogs a possible correlation of the stride frequency with kinetic and temporospatial variables, as well as the percentage of body weight distribution (%BWD), and compare symmetry index (SI) between trotting and walking dogs. Twenty-nine clinically healthy dogs moving in a controlled velocity were used. The dogs were organized into two groups based on duty factor. Group 1 comprised 15 walking dogs, aged from 9 months to 8 years and weighing about 22.3 kg. Group 2 had 14 trotting dogs, aged from 1 to 6 years and weighing about 6.5 kg. The kinetic data and temporospatial parameters were obtained using a pressure-sensing walkway. The velocity was 0.9-1.1 m/s. The peak vertical force (PVF), vertical impulse (VI), gait cycle time, stance time, swing time, stride length, and percentages of body weight distribution among the four limbs were determined. For each variable, the SIs were calculated. Pearson's coefficient was used to evaluate correlation between stride frequency and other variables, initially in each group and after including all animals. Except for the %BWD (approximately 60% for the forelimbs and 40% for the hind limbs), all other parameters differed between groups. Considering each Group individually a strong correlation was observed for most of the temporospatial parameters, but no significant correlation occurred between stride frequency and PVF, and stride frequency and %BWD. However, including all dogs a strong correlation was observed in all temporospatial parameters, and moderate correlation between stride frequency and VI, and weak correlation between stride frequency and PVF. There was no correlation between stride frequency and %BWD. Groups 1 and 2 did not differ statistically in SIs. In a heterogeneous group of dogs conducted at a controlled velocity, the %BWD and most of SIs presented low variability. However, %BWD seems to be the most accurate, since factors such as the magnitude of the variables may influence the SIs inducing wrong interpretation. Based on results obtained from correlations, the standardization of stride frequency could be an alternative to minimize the variability of temporospatial parameters.

When Human Walking is a Random Walk

NASA Astrophysics Data System (ADS)

Hausdorff, J. M.

1998-03-01

The complex, hierarchical locomotor system normally does a remarkable job of controlling an inherently unstable, multi-joint system. Nevertheless, the stride interval --- the duration of a gait cycle --- fluctuates from one stride to the next, even under stationary conditions. We used random walk analysis to study the dynamical properties of these fluctuations under normal conditions and how they change with disease and aging. Random walk analysis of the stride-to-stride fluctuations of healthy, young adult men surprisingly reveals a self-similar pattern: fluctuations at one time scale are statistically similar to those at multiple other time scales (Hausdorff et al, J Appl Phsyiol, 1995). To study the stability of this fractal property, we analyzed data obtained from healthy subjects who walked for 1 hour at their usual pace, as well as at slower and faster speeds. The stride interval fluctuations exhibited long-range correlations with power-law decay for up to a thousand strides at all three walking rates. In contrast, during metronomically-paced walking, these long-range correlations disappeared; variations in the stride interval were uncorrelated and non-fractal (Hausdorff et al, J Appl Phsyiol, 1996). To gain insight into the mechanism(s) responsible for this fractal property, we examined the effects of aging and neurological impairment. Using detrended fluctuation analysis (DFA), we computed α, a measure of the degree to which one stride interval is correlated with previous and subsequent intervals over different time scales. α was significantly lower in healthy elderly subjects compared to young adults (p < .003) and in subjects with Huntington's disease, a neuro-degenerative disorder of the central nervous system, compared to disease-free controls (p < 0.005) (Hausdorff et al, J Appl Phsyiol, 1997). α was also significantly related to degree of functional impairment in subjects with Huntington's disease (r=0.78). Recently, we have observed that just as there are changes with α during aging, there also changes with development. Apparently, the fractal scaling of walking does not become mature until children are eleven years old. Conclusions: The fractal dynamics of spontaneous stride interval fluctuations are normally quite robust and are apparently intrinsic to the healthy adult locomotor system. However, alterations in this fractal scaling property are associated with impairment in central nervous system control, aging and neural development.

Possible biomechanical origins of the long-range correlations in stride intervals of walking

NASA Astrophysics Data System (ADS)

Gates, Deanna H.; Su, Jimmy L.; Dingwell, Jonathan B.

2007-07-01

When humans walk, the time duration of each stride varies from one stride to the next. These temporal fluctuations exhibit long-range correlations. It has been suggested that these correlations stem from higher nervous system centers in the brain that control gait cycle timing. Existing proposed models of this phenomenon have focused on neurophysiological mechanisms that might give rise to these long-range correlations, and generally ignored potential alternative mechanical explanations. We hypothesized that a simple mechanical system could also generate similar long-range correlations in stride times. We modified a very simple passive dynamic model of bipedal walking to incorporate forward propulsion through an impulsive force applied to the trailing leg at each push-off. Push-off forces were varied from step to step by incorporating both “sensory” and “motor” noise terms that were regulated by a simple proportional feedback controller. We generated 400 simulations of walking, with different combinations of sensory noise, motor noise, and feedback gain. The stride time data from each simulation were analyzed using detrended fluctuation analysis to compute a scaling exponent, α. This exponent quantified how each stride interval was correlated with previous and subsequent stride intervals over different time scales. For different variations of the noise terms and feedback gain, we obtained short-range correlations (α<0.5), uncorrelated time series (α=0.5), long-range correlations (0.5<α<1.0), or Brownian motion (α>1.0). Our results indicate that a simple biomechanical model of walking can generate long-range correlations and thus perhaps these correlations are not a complex result of higher level neuronal control, as has been previously suggested.

Inducing self-selected human engagement in robotic locomotion training.

PubMed

Collins, Steven H; Jackson, Rachel W

2013-06-01

Stroke leads to severe mobility impairments for millions of individuals each year. Functional outcomes can be improved through manual treadmill therapy, but high costs limit patient exposure and, thereby, outcomes. Robotic gait training could increase the viable duration and frequency of training sessions, but robotic approaches employed thus far have been less effective than manual therapy. These shortcomings may relate to subconscious energy-minimizing drives, which might cause patients to engage less actively in therapy when provided with corrective robotic assistance. We have devised a new method for gait rehabilitation that harnesses, rather than fights, least-effort tendencies. Therapeutic goals, such as increased use of the paretic limb, are made easier than the patient's nominal gait through selective assistance from a robotic platform. We performed a pilot test on a healthy subject (N = 1) in which altered self-selected stride length was induced using a tethered robotic ankle-foot orthosis. The subject first walked on a treadmill while wearing the orthosis with and without assistance at unaltered and voluntarily altered stride length. Voluntarily increasing stride length by 5% increased metabolic energy cost by 4%. Robotic assistance decreased energy cost at both unaltered and voluntarily increased stride lengths, by 6% and 8% respectively. We then performed a test in which the robotic system continually monitored stride length and provided more assistance if the subject's stride length approached a target increase. This adaptive assistance protocol caused the subject to slowly adjust their gait patterns towards the target, leading to a 4% increase in stride length. Metabolic energy consumption was simultaneously reduced by 5%. These results suggest that selective-assistance protocols based on targets relevant to rehabilitation might lead patients to self-select desirable gait patterns during robotic gait training sessions, possibly facilitating better adherence and outcomes.

Gait Implications of Visual Field Damage from Glaucoma.

PubMed

Mihailovic, Aleksandra; Swenor, Bonnielin K; Friedman, David S; West, Sheila K; Gitlin, Laura N; Ramulu, Pradeep Y

2017-06-01

To evaluate fall-relevant gait features in older glaucoma patients. The GAITRite Electronic Walkway was used to define fall-related gait parameters in 239 patients with suspected or manifest glaucoma under normal usual-pace walking conditions and while carrying a cup or tray. Multiple linear regression models assessed the association between gait parameters and integrated visual field (IVF) sensitivity after controlling for age, race, sex, medications, and comorbid illness. Under normal walking conditions, worse IVF sensitivity was associated with a wider base of support (β = 0.60 cm/5 dB IVF sensitivity decrement, 95% confidence interval [CI] = 0.12-1.09, P = 0.016). Worse IVF sensitivity was not associated with slower gait speed, shorter step or stride length, or greater left-right drift under normal walking conditions ( P > 0.05 for all), but was during cup and/or tray carrying conditions ( P < 0.05 for all). Worse IVF sensitivity was positively associated with greater stride-to-stride variability in step length, stride length, and stride velocity ( P < 0.005 for all). Inferior and superior IVF sensitivity demonstrated associations with each of the above gait parameters as well, though these associations were consistently similar to, or weaker than, the associations noted for overall IVF sensitivity. Glaucoma severity was associated with several gait parameters predictive of higher fall risk in prior studies, particularly measures of stride-to-stride variability. Gait may be useful in identifying glaucoma patients at higher risk of falls, and in designing and testing interventions to prevent falls in this high-risk group. These findings could serve to inform the development of the interventions for falls prevention in glaucoma patients.

Surface-EMG analysis for the quantification of thigh muscle dynamic co-contractions during normal gait.

PubMed

Strazza, Annachiara; Mengarelli, Alessandro; Fioretti, Sandro; Burattini, Laura; Agostini, Valentina; Knaflitz, Marco; Di Nardo, Francesco

2017-01-01

The research purpose was to quantify the co-contraction patterns of quadriceps femoris (QF) vs. hamstring muscles during free walking, in terms of onset-offset muscular activation, excitation intensity, and occurrence frequency. Statistical gait analysis was performed on surface-EMG signals from vastus lateralis (VL), rectus femoris (RF), and medial hamstrings (MH), in 16315 strides walked by 30 healthy young adults. Results showed full superimpositions of MH with both VL and RF activity from terminal swing, 80 to 100% of gait cycle (GC), to the successive loading response (≈0-15% of GC), in around 90% of the considered strides. A further superimposition was detected during the push-off phase both between VL and MH activation intervals (38.6±12.8% to 44.1±9.6% of GC) in 21.9±13.6% of strides, and between RF and MH activation intervals (45.9±5.3% to 50.7±9.7 of GC) in 32.7±15.1% of strides. These findings led to identify three different co-contractions among QF and hamstring muscles during able-bodied walking: in early stance (in ≈90% of strides), in push-off (in 25-30% of strides) and in terminal swing (in ≈90% of strides). The co-contraction in terminal swing is the one with the highest levels of muscle excitation intensity. To our knowledge, this analysis represents the first attempt for quantification of QF/hamstring muscles co-contraction in young healthy subjects during normal gait, able to include the physiological variability of the phenomenon. Copyright © 2016 Elsevier B.V. All rights reserved.

Gait and risk of falls associated with frontal cognitive functions at different stages of Alzheimer's disease.

PubMed

Coelho, Flávia Gomes de Melo; Stella, Florindo; de Andrade, Larissa Pires; Barbieri, Fabio Augusto; Santos-Galduróz, Ruth Ferreira; Gobbi, Sebastião; Costa, José Luiz Riani; Gobbi, Lilian Teresa Bucken

2012-09-01

The decline in frontal cognitive functions contributes to alterations of gait and increases the risk of falls in patients with dementia, a category which included Alzheimer's disease (AD). The objective of the present study was to compare the gait parameters and the risk of falls among patients at different stages of AD, and to relate these variables with cognitive functions. This is a cross-sectional study with 23 patients with mild and moderate AD. The Clinical Dementia Rating was used to classify the dementia severity. The kinematic parameters of gait (cadence, stride length, and stride speed) were analyzed under two conditions: (a) single task (free gait) and (b) dual task (walking and counting down). The risk of falls was evaluated using the Timed Up-and-Go test. The frontal cognitive functions were evaluated using the Frontal Assessment Battery (FAB), the Clock Drawing Test (CDT) and the Symbol Search Subtest. The patients who were at the moderate stage suffered reduced performance in their stride length and stride speed in the single task and had made more counting errors in the dual task and still had a higher fall risk. Both the mild and the moderate patients exhibited significant decreases in stride length, stride speed and cadence in the dual task. Was detected a significant correlation between CDT, FAB, and stride speed in the dual task condition. We also found a significant correlation between subtest Similarities, FAB and cadence in the dual task condition. The dual task produced changes in the kinematic parameters of gait for the mild and moderate AD patients and the gait alterations are related to frontal cognitive functions, particularly executive functions.

A single hydrotherapy session increases range of motion and stride length in Labrador retrievers diagnosed with elbow dysplasia.

PubMed

Preston, T; Wills, A P

2018-04-01

Canine elbow dysplasia is a debilitating condition of unknown aetiology and is a common cause of forelimb lameness in dogs. Canine hydrotherapy is a therapeutic approach rapidly increasing in popularity for the treatment of a range of musculoskeletal pathologies. In this study, kinematic analysis was used to assess the effect of a customised hydrotherapy session on the range of motion, stride length and stride frequency of healthy Labrador retrievers (n=6) and Labrador retrievers diagnosed with bilateral elbow dysplasia (n=6). Reflective kinematic markers were attached to bony anatomical landmarks and dogs were recorded walking at their preferred speed on a treadmill before and 10min after a single hydrotherapy session. Range of motion, stride length and stride frequency were calculated for both forelimbs. Data were analysed via a robust mixed ANOVA to assess the effect of hydrotherapy on the kinematic parameters of both groups. Range of motion was greater in the healthy dogs at baseline (P<0.05). Hydrotherapy increased the range of motion of the forelimbs of both groups (P<0.05); dogs with elbow dysplasia demonstrated a greater improvement in range of motion than healthy dogs (P<0.05). Hydrotherapy stride length (P<0.01) of all dogs, but differences were not seen between the two groups. Stride frequency increased after hydrotherapy only in the left limb (P<0.05) in all dogs. These results support the potential of canine hydrotherapy as a therapeutic tool for the rehabilitation and treatment of Labradors with elbow dysplasia. Furthermore, results indicate that hydrotherapy might improve the gait and movement of healthy dogs. However, whether these results are transient or sustained remains undetermined. Copyright © 2018 Elsevier Ltd. All rights reserved.

Gait variability and basal ganglia disorders: stride-to-stride variations of gait cycle timing in Parkinson's disease and Huntington's disease

NASA Technical Reports Server (NTRS)

Hausdorff, J. M.; Cudkowicz, M. E.; Firtion, R.; Wei, J. Y.; Goldberger, A. L.

1998-01-01

The basal ganglia are thought to play an important role in regulating motor programs involved in gait and in the fluidity and sequencing of movement. We postulated that the ability to maintain a steady gait, with low stride-to-stride variability of gait cycle timing and its subphases, would be diminished with both Parkinson's disease (PD) and Huntington's disease (HD). To test this hypothesis, we obtained quantitative measures of stride-to-stride variability of gait cycle timing in subjects with PD (n = 15), HD (n = 20), and disease-free controls (n = 16). All measures of gait variability were significantly increased in PD and HD. In subjects with PD and HD, gait variability measures were two and three times that observed in control subjects, respectively. The degree of gait variability correlated with disease severity. In contrast, gait speed was significantly lower in PD, but not in HD, and average gait cycle duration and the time spent in many subphases of the gait cycle were similar in control subjects, HD subjects, and PD subjects. These findings are consistent with a differential control of gait variability, speed, and average gait cycle timing that may have implications for understanding the role of the basal ganglia in locomotor control and for quantitatively assessing gait in clinical settings.

Effect of rhythmic auditory stimulation on gait kinematic parameters of patients with multiple sclerosis.

PubMed

Shahraki, M; Sohrabi, M; Taheri Torbati, H R; Nikkhah, K; NaeimiKia, M

2017-01-01

Purpose: This study aimed to examine the effect of rhythmic auditory stimulation on gait kinematic parameters of patients with multiple sclerosis. Subjects and Methods: In this study, 18 subjects, comprising 4 males and 14 females with Multiple Sclerosis with expanded disability status scale of 3 to 6 were chosen. Subjects were selected by available and targeted sampling and were randomly divided into two experimental (n = 9) and control (n = 9) groups. Exercises were gait with rhythmic auditory stimulation by a metronome device, in addition to gait without stimulation for the experimental and control groups, respectively. Training was carried out for 3 weeks, with 30 min duration for each session 3 times a week. Stride length, stride time, double support time, cadence and gait speed were measured by motion analysis device. Results: There was a significant difference between stride length, stride time, double support time, cadence and gait speed in the experimental group, before and after the training. Furthermore, there was a significant difference between the experimental and control groups in the enhancement of stride length, stride time, cadence and gait speed in favor of the experimental group. While this difference was not significant for double support time. Conclusion: The results of this study showed that rhythmic auditory stimulation is an effective rehabilitation method to improve gait kinematic parameters in patients with multiple sclerosis.

Effects of a minimalist shoe on running economy and 5-km running performance.

PubMed

Fuller, Joel T; Thewlis, Dominic; Tsiros, Margarita D; Brown, Nicholas A T; Buckley, Jonathan D

2016-09-01

The purpose of this study was to determine if minimalist shoes improve time trial performance of trained distance runners and if changes in running economy, shoe mass, stride length, stride rate and footfall pattern were related to any difference in performance. Twenty-six trained runners performed three 6-min sub-maximal treadmill runs at 11, 13 and 15 km·h(-1) in minimalist and conventional shoes while running economy, stride length, stride rate and footfall pattern were assessed. They then performed a 5-km time trial. In the minimalist shoe, runners completed the trial in less time (effect size 0.20 ± 0.12), were more economical during sub-maximal running (effect size 0.33 ± 0.14) and decreased stride length (effect size 0.22 ± 0.10) and increased stride rate (effect size 0.22 ± 0.11). All but one runner ran with a rearfoot footfall in the minimalist shoe. Improvements in time trial performance were associated with improvements in running economy at 15 km·h(-1) (r = 0.58), with 79% of the improved economy accounted for by reduced shoe mass (P < 0.05). The results suggest that running in minimalist shoes improves running economy and 5-km running performance.

The effect of racetrack design on gait symmetry of the pacer.

PubMed Central

Crawford, W H; Leach, D H

1984-01-01

A survey of a western Canadian racetrack determined the superelevation and transition curves to be less than the cited design standards. High-speed cinematography was used to film seven Standardbred pacers as they proceeded around one curve of the track at racing speed and for each horse 19 temporal stride parameters were obtained from these films using a film analyzer system. Average velocities were calculated and the mean stride length was found to vary from 5.08 m to 5.77 m. In all frames analyzed the hind foot was observed to contact the track surface prior to the ipsilateral forefoot and all horses displayed significant (p less than 0.05) contralateral asymmetry of some temporal stride parameters. Fifteen temporal stride parameters were significantly different (p less than 0.05) when compared between horses but only three temporal stride parameters were significantly different (p less than 0.05) when their values were compared between segments of the curved portions of the track. It is suggested that temporal gait asymmetry should not be used to judge the standards of racetrack design. PMID:6509365

Exploring the relationship between stride, stature and hand size for forensic assessment.

PubMed

Guest, Richard; Miguel-Hurtado, Oscar; Stevenage, Sarah; Black, Sue

2017-11-01

Forensic evidence often relies on a combination of accurately recorded measurements, estimated measurements from landmark data such as a subject's stature given a known measurement within an image, and inferred data. In this study a novel dataset is used to explore linkages between hand measurements, stature, leg length and stride. These three measurements replicate the type of evidence found in surveillance videos with stride being extracted from an automated gait analysis system. Through correlations and regression modelling, it is possible to generate accurate predictions of stature from hand size, leg length and stride length (and vice versa), and to predict leg and stride length from hand size with, or without, stature as an intermediary variable. The study also shows improved accuracy when a subject's sex is known a-priori. Our method and models indicate the possibility of calculating or checking relationships between a suspect's physical measurements, particularly when only one component is captured as an accurately recorded measurement. Copyright © 2017 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

Ambiguity domain-based identification of altered gait pattern in ALS disorder

NASA Astrophysics Data System (ADS)

Sugavaneswaran, L.; Umapathy, K.; Krishnan, S.

2012-08-01

The onset of a neurological disorder, such as amyotrophic lateral sclerosis (ALS), is so subtle that the symptoms are often overlooked, thereby ruling out the option of early detection of the abnormality. In the case of ALS, over 75% of the affected individuals often experience awkwardness when using their limbs, which alters their gait, i.e. stride and swing intervals. The aim of this work is to suitably represent the non-stationary characteristics of gait (fluctuations in stride and swing intervals) in order to facilitate discrimination between normal and ALS subjects. We define a simple-yet-representative feature vector space by exploiting the ambiguity domain (AD) to achieve efficient classification between healthy and pathological gait stride interval. The stride-to-stride fluctuations and the swing intervals of 16 healthy control and 13 ALS-affected subjects were analyzed. Three features that are representative of the gait signal characteristics were extracted from the AD-space and are fed to linear discriminant analysis and neural network classifiers, respectively. Overall, maximum accuracies of 89.2% (LDA) and 100% (NN) were obtained in classifying the ALS gait.

The effect of racetrack design on gait symmetry of the pacer.

PubMed

Crawford, W H; Leach, D H

1984-10-01

A survey of a western Canadian racetrack determined the superelevation and transition curves to be less than the cited design standards. High-speed cinematography was used to film seven Standardbred pacers as they proceeded around one curve of the track at racing speed and for each horse 19 temporal stride parameters were obtained from these films using a film analyzer system. Average velocities were calculated and the mean stride length was found to vary from 5.08 m to 5.77 m. In all frames analyzed the hind foot was observed to contact the track surface prior to the ipsilateral forefoot and all horses displayed significant (p less than 0.05) contralateral asymmetry of some temporal stride parameters. Fifteen temporal stride parameters were significantly different (p less than 0.05) when compared between horses but only three temporal stride parameters were significantly different (p less than 0.05) when their values were compared between segments of the curved portions of the track. It is suggested that temporal gait asymmetry should not be used to judge the standards of racetrack design.

Safety considerations for fabricating lithium battery packs

NASA Technical Reports Server (NTRS)

Ciesla, J. J.

1986-01-01

Lithium cell safety is a major issue with both manufacturers and end users. Most manufacturers have taken great strides to develop the safest cells possible while still maintaining performance characteristics. The combining of lithium cells for higher voltages, currents, and capacities requires the fabricator of lithium battery packs to be knowledgable about the specific electrochemical system being used. Relatively high rate, spirally wound (large surface area) sulfur oxychloride cells systems, such as Li/Thionyl or Sulfuryl chloride are considered. Prior to the start of a design of a battery pack, a review of the characterization studies for the cells should be conducted. The approach for fabricating a battery pack might vary with cell size.

Controlled formation of closed-edge nanopores in graphene

NASA Astrophysics Data System (ADS)

He, Kuang; Robertson, Alex W.; Gong, Chuncheng; Allen, Christopher S.; Xu, Qiang; Zandbergen, Henny; Grossman, Jeffrey C.; Kirkland, Angus I.; Warner, Jamie H.

2015-07-01

Dangling bonds at the edge of a nanopore in monolayer graphene make it susceptible to back-filling at low temperatures from atmospheric hydrocarbons, leading to potential instability for nanopore applications, such as DNA sequencing. We show that closed edge nanopores in bilayer graphene are robust to back-filling under atmospheric conditions for days. A controlled method for closed edge nanopore formation starting from monolayer graphene is reported using an in situ heating holder and electron beam irradiation within an aberration-corrected transmission electron microscopy. Tailoring of closed-edge nanopore sizes is demonstrated from 1.4-7.4 nm. These results should provide mechanisms for improving the stability of nanopores in graphene for a wide range of applications involving mass transport.Dangling bonds at the edge of a nanopore in monolayer graphene make it susceptible to back-filling at low temperatures from atmospheric hydrocarbons, leading to potential instability for nanopore applications, such as DNA sequencing. We show that closed edge nanopores in bilayer graphene are robust to back-filling under atmospheric conditions for days. A controlled method for closed edge nanopore formation starting from monolayer graphene is reported using an in situ heating holder and electron beam irradiation within an aberration-corrected transmission electron microscopy. Tailoring of closed-edge nanopore sizes is demonstrated from 1.4-7.4 nm. These results should provide mechanisms for improving the stability of nanopores in graphene for a wide range of applications involving mass transport. Electronic supplementary information (ESI) available: Low magnification images, image processing techniques employed, modelling and simulation of closed edge nanoribbon, comprehensive AC-TEM dataset, and supporting analysis. See DOI: 10.1039/c5nr02277k

Magnetism of Nanographene-Based Microporous Carbon and Its Applications: Interplay of Edge Geometry and Chemistry Details in the Edge State

NASA Astrophysics Data System (ADS)

Enoki, Toshiaki; Kiguchi, Manabu

2018-03-01

This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. Nanographenes have important edge geometry dependence in their electronic structures. In armchair edges, electron wave interference works to contribute to energetic stability. Meanwhile, zigzag edges possess an edge-localized and spin-polarized nonbonding edge state, which causes electronic, magnetic, and chemical activities. In addition to the geometry dependence, the electronic structures are seriously affected by edge chemistry details. The edge chemistry dependence together with edge geometries on the electronic structures are discussed with samples of randomly networked nanographenes (microporous activated carbon fibers) in pristine state and under high-temperature annealing. In the pristine sample with the edges oxidized in ambient atmospheric conditions, the edge state, which is otherwise unstable, can be stabilized because of the charge transfer from nanographene to terminating oxygen. Nanographene, whose edges consist of a combination of magnetic zigzag edges and nonmagnetic armchair edges, is found to be ferrimagnetic with a nonzero net magnetic moment created under the interplay between a strong intrazigzag-edge ferromagnetic interaction and intermediate-strength interzigzag-edge antiferromagnetic-ferromagnetic interaction. At heat-treatment temperatures just below the fusion start (approximately 1500 K), the edge-terminating structure is changed from oxygen-containing groups to hydrogen in the nanographene network. Additionally, hydrogen-terminated zigzag edges, which are present as the majority and chemically unstable, play a triggering role in fusion above 1500 K. The fusion start brings about an insulator-to-metal transition at TI -M˜1500 K . Local fusions taking place percolatively between nanographenes work to expand the π -bond network, eventually resulting in the development of antiferromagnetic short-range order toward spin glass in the magnetic moments of nanographenes. For applications, the edge-state spins in nanographene-based microporous carbon can be a good tool as a molecule sensor in detecting molecules having different chemical properties and sizes. The on-off magnetic switching phenomena upon the adsorption of H2O and other OH-containing molecules offers a molecule sensor. A He sensor, in which the edge-state spins is employed as a probe, is also proposed on the basis of a huge condensation of He into ultramicropores.

Optic flow odometry operates independently of stride integration in carried ants.

PubMed

Pfeffer, Sarah E; Wittlinger, Matthias

2016-09-09

Cataglyphis desert ants are impressive navigators. When the foragers roam the desert, they employ path integration. For these ants, distance estimation is one key challenge. Distance information was thought to be provided by optic flow (OF)-that is, image motion experienced during travel-but this idea was abandoned when stride integration was discovered as an odometer mechanism in ants. We show that ants transported by nest mates are capable of measuring travel distance exclusively by the use of OF cues. Furthermore, we demonstrate that the information gained from the optic flowmeter cannot be transferred to the stride integrator. Our results suggest a dual information channel that allows the ants to measure distances by strides and OF cues, although both systems operate independently and in a redundant manner. Copyright © 2016, American Association for the Advancement of Science.

Anticipatory kinematics and muscle activity preceding transitions from level-ground walking to stair ascent and descent.

PubMed

Peng, Joshua; Fey, Nicholas P; Kuiken, Todd A; Hargrove, Levi J

2016-02-29

The majority of fall-related accidents are during stair ambulation-occurring commonly at the top and bottom stairs of each flight, locations in which individuals are transitioning to stairs. Little is known about how individuals adjust their biomechanics in anticipation of walking-stair transitions. We identified the anticipatory stride mechanics of nine able-bodied individuals as they approached transitions from level ground walking to stair ascent and descent. Unlike prior investigations of stair ambulation, we analyzed two consecutive "anticipation" strides preceding the transitions strides to stairs, and tested a comprehensive set of kinematic and electromyographic (EMG) data from both the leading and trailing legs. Subjects completed ten trials of baseline overground walking and ten trials of walking to stair ascent and descent. Deviations relative to baseline were assessed. Significant changes in mechanics and EMG occurred in the earliest anticipation strides analyzed for both ascent and descent transitions. For stair descent, these changes were consistent with observed reductions in walking speed, which occurred in all anticipation strides tested. For stair ascent, subjects maintained their speed until the swing phase of the latest anticipation stride, and changes were found that would normally be observed for decreasing speed. Given the timing and nature of the observed changes, this study has implications for enhancing intent recognition systems and evaluating fall-prone or disabled individuals, by testing their abilities to sense upcoming transitions and decelerate during locomotion. Copyright © 2016 Elsevier Ltd. All rights reserved.

Persistent fluctuations in stride intervals under fractal auditory stimulation.

PubMed

Marmelat, Vivien; Torre, Kjerstin; Beek, Peter J; Daffertshofer, Andreas

2014-01-01

Stride sequences of healthy gait are characterized by persistent long-range correlations, which become anti-persistent in the presence of an isochronous metronome. The latter phenomenon is of particular interest because auditory cueing is generally considered to reduce stride variability and may hence be beneficial for stabilizing gait. Complex systems tend to match their correlation structure when synchronizing. In gait training, can one capitalize on this tendency by using a fractal metronome rather than an isochronous one? We examined whether auditory cues with fractal variations in inter-beat intervals yield similar fractal inter-stride interval variability as isochronous auditory cueing in two complementary experiments. In Experiment 1, participants walked on a treadmill while being paced by either an isochronous or a fractal metronome with different variation strengths between beats in order to test whether participants managed to synchronize with a fractal metronome and to determine the necessary amount of variability for participants to switch from anti-persistent to persistent inter-stride intervals. Participants did synchronize with the metronome despite its fractal randomness. The corresponding coefficient of variation of inter-beat intervals was fixed in Experiment 2, in which participants walked on a treadmill while being paced by non-isochronous metronomes with different scaling exponents. As expected, inter-stride intervals showed persistent correlations similar to self-paced walking only when cueing contained persistent correlations. Our results open up a new window to optimize rhythmic auditory cueing for gait stabilization by integrating fractal fluctuations in the inter-beat intervals.

Persistent Fluctuations in Stride Intervals under Fractal Auditory Stimulation

PubMed Central

Marmelat, Vivien; Torre, Kjerstin; Beek, Peter J.; Daffertshofer, Andreas

2014-01-01

Stride sequences of healthy gait are characterized by persistent long-range correlations, which become anti-persistent in the presence of an isochronous metronome. The latter phenomenon is of particular interest because auditory cueing is generally considered to reduce stride variability and may hence be beneficial for stabilizing gait. Complex systems tend to match their correlation structure when synchronizing. In gait training, can one capitalize on this tendency by using a fractal metronome rather than an isochronous one? We examined whether auditory cues with fractal variations in inter-beat intervals yield similar fractal inter-stride interval variability as isochronous auditory cueing in two complementary experiments. In Experiment 1, participants walked on a treadmill while being paced by either an isochronous or a fractal metronome with different variation strengths between beats in order to test whether participants managed to synchronize with a fractal metronome and to determine the necessary amount of variability for participants to switch from anti-persistent to persistent inter-stride intervals. Participants did synchronize with the metronome despite its fractal randomness. The corresponding coefficient of variation of inter-beat intervals was fixed in Experiment 2, in which participants walked on a treadmill while being paced by non-isochronous metronomes with different scaling exponents. As expected, inter-stride intervals showed persistent correlations similar to self-paced walking only when cueing contained persistent correlations. Our results open up a new window to optimize rhythmic auditory cueing for gait stabilization by integrating fractal fluctuations in the inter-beat intervals. PMID:24651455

The influence of inertial sensor sampling frequency on the accuracy of measurement parameters in rearfoot running.

PubMed

Mitschke, Christian; Zaumseil, Falk; Milani, Thomas L

2017-11-01

Increasingly, inertial sensors are being used for running analyses. The aim of this study was to systematically investigate the influence of inertial sensor sampling frequencies (SF) on the accuracy of kinematic, spatio-temporal, and kinetic parameters. We hypothesized that running analyses at lower SF result in less signal information and therefore the inability to sufficiently interpret measurement data. Twenty-one subjects participated in this study. Rearfoot strikers ran on an indoor running track at a velocity of 3.5 ± 0.1 ms -1 . A uniaxial accelerometer was attached at the tibia and an inertial measurement unit was mounted at the heel of the right shoe. All sensors were synchronized at the start and data was measured with 1000 Hz (reference SF). Datasets were reduced to 500, 333, 250, 200, and 100 Hz in post-processing. The results of this study showed that a minimum SF of 500 Hz should be used to accurately measure kinetic parameters (e.g. peak heel acceleration). In contrast, stride length showed accurate results even at 333 Hz. 200 Hz were required to calculate parameters accurately for peak tibial acceleration, stride duration, and all kinematic measurements. The information from this study is necessary to correctly interpret measurement data of existing investigations and to plan future studies.

Is walking a random walk? Evidence for long-range correlations in stride interval of human gait

NASA Technical Reports Server (NTRS)

Hausdorff, Jeffrey M.; Peng, C.-K.; Ladin, Zvi; Wei, Jeanne Y.; Goldberger, Ary L.

1995-01-01

Complex fluctuation of unknown origin appear in the normal gait pattern. These fluctuations might be described as being (1) uncorrelated white noise, (2) short-range correlations, or (3) long-range correlations with power-law scaling. To test these possibilities, the stride interval of 10 healthy young men was measured as they walked for 9 min at their usual rate. From these time series we calculated scaling indexes by using a modified random walk analysis and power spectral analysis. Both indexes indicated the presence of long-range self-similar correlations extending over hundreds of steps; the stride interval at any time depended on the stride interval at remote previous times, and this dependence decayed in a scale-free (fractallike) power-law fashion. These scaling indexes were significantly different from those obtained after random shuffling of the original time series, indicating the importance of the sequential ordering of the stride interval. We demonstrate that conventional models of gait generation fail to reproduce the observed scaling behavior and introduce a new type of central pattern generator model that sucessfully accounts for the experimentally observed long-range correlations.

Influence of footwear and equipment on stride length and range of motion of ankle, knee and hip joint.

PubMed

Schulze, Christoph; Lindner, Tobias; Woitge, Sandra; Schulz, Katharina; Finze, Susanne; Mittelmeier, Wolfram; Bader, Rainer

2014-01-01

Footwear and equipment worn by military personnel is of importance for them to be able to meet the physical demands specific to their profession daily activities. The aim of the present study was to investigate by means of gait analysis how army-provided footwear and equipment influence the range of motion of hip, knee and ankle joints as well as stride length. Thirty-two soldiers were subjected to gait analysis on a treadmill by way of video recordings and goniometric measurements. The stride length increased when military shoes are worn. We found no influence on stride length in connection to increased loading. The weight of the shoes represents the decisive factor. Neither shoes nor equipment changed the range of motion of the knee joint. Weight of equipment affected range of motion of the hip joint. The range of motion of the upper and lower ankle joints was mainly influenced by the properties of the shoes. Military footwear and weight of equipment influence stride length and range of motion of joints of the lower extremities in a specific way. Shape of material is the decisive factor.

Increased delivery stride length places greater loads on the ankle joint in elite male cricket fast bowlers.

PubMed

Spratford, Wayne; Hicks, Amy

2014-01-01

The purpose of this study was to investigate the effect stride length has on ankle biomechanics of the leading leg with reference to the potential risk of injury in cricket fast bowlers. Ankle joint kinematic and kinetic data were collected from 51 male fast bowlers during the stance phase of the final delivery stride. The bowling cohort comprised national under-19, first class and international-level athletes. Bowlers were placed into either Short, Average or Long groups based on final stride length, allowing statistical differences to be measured. A multivariate analysis of variance with a Bonferroni post-hoc correction (α = 0.05) revealed significant differences between peak plantarflexion angles (Short-Long P = 0.005, Average and Long P = 0.04) and negative joint work (Average-Long P = 0.026). This study highlighted that during fast bowling the ankle joint of the leading leg experiences high forces under wide ranges of movement. As stride length increases, greater amounts of negative work and plantarflexion are experienced. These increases place greater loads on the ankle joint and move the foot into positions that make it more susceptible to injuries such as posterior impingement syndrome.

Long-Range Correlations in Stride Intervals May Emerge from Non-Chaotic Walking Dynamics

PubMed Central

Ahn, Jooeun; Hogan, Neville

2013-01-01

Stride intervals of normal human walking exhibit long-range temporal correlations. Similar to the fractal-like behaviors observed in brain and heart activity, long-range correlations in walking have commonly been interpreted to result from chaotic dynamics and be a signature of health. Several mathematical models have reproduced this behavior by assuming a dominant role of neural central pattern generators (CPGs) and/or nonlinear biomechanics to evoke chaos. In this study, we show that a simple walking model without a CPG or biomechanics capable of chaos can reproduce long-range correlations. Stride intervals of the model revealed long-range correlations observed in human walking when the model had moderate orbital stability, which enabled the current stride to affect a future stride even after many steps. This provides a clear counterexample to the common hypothesis that a CPG and/or chaotic dynamics is required to explain the long-range correlations in healthy human walking. Instead, our results suggest that the long-range correlation may result from a combination of noise that is ubiquitous in biological systems and orbital stability that is essential in general rhythmic movements. PMID:24086274

Energy absorption of impacts during running at various stride lengths.

PubMed

Derrick, T R; Hamill, J; Caldwell, G E

1998-01-01

The foot-ground impact experienced during running produces a shock wave that is transmitted through the human skeletal system. This shock wave is attenuated by deformation of the ground/shoe as well as deformation of biological tissues in the body. The goal of this study was to investigate the locus of energy absorption during the impact phase of the running cycle. Running speed (3.83 m x s[-1]) was kept constant across five stride length conditions: preferred stride length (PSL), +10% of PSL, -10% of PSL, +20% of PSL, and -20% of PSL. Transfer functions were generated from accelerometers attached to the leg and head of ten male runners. A rigid body model was used to estimate the net energy absorbed at the hip, knee, and ankle joints. There was an increasing degree of shock attenuation as stride length increased. The energy absorbed during the impact portion of the running cycle also increased with stride length. Muscles that cross the knee joint showed the greatest adjustment in response to increased shock. It was postulated that the increased perpendicular distance from the line of action of the resultant ground reaction force to the knee joint center played a role in this increased energy absorption.

A Descriptive Case Study of the Perceptions and Use of Adventist Edge: An Initiative Developed in Response to the North American Division of Seventh-Day Adventists' Document, "Journey to Excellence"

ERIC Educational Resources Information Center

Forbes, Pamela C.

2011-01-01

Problem. The Southern Union started the Adventist EDGE initiative as an action plan in response to the North American Division's document, "Journey to Excellence." The Adventist EDGE became a comprehensive educational reform initiative. However, there were different ideas on how the innovation should look when in action in the schools, and these…

30 CFR 14.22 - Test for flame resistance of conveyor belts.

Code of Federal Regulations, 2010 CFR

2010-07-01

... the front of the rails and 1 ± 1/8 inch (2.5 ± 0.3 cm) from the outer lengthwise edge of each rail; (3... holes approximately 9/32 inch (0.7 cm) in diameter along both edges of the belt sample, starting at the first rail hole within 2 inches (5.1 cm) from the front edge of the sample. Make the next hole 5 ± 1/4...

EPA Making Strides in Cleaning Up the Nation’s Most Contaminated Sites

EPA Pesticide Factsheets

Due to the hard work of staff to implement Administrator Pruitt's initiatives to make strides in cleaning up the nation's most contaminated toxic land sites, the USEPA is announcing significant improvement in 2017...

Stride search: A general algorithm for storm detection in high resolution climate data

DOE PAGES

Bosler, Peter Andrew; Roesler, Erika Louise; Taylor, Mark A.; ...

2015-09-08

This article discusses the problem of identifying extreme climate events such as intense storms within large climate data sets. The basic storm detection algorithm is reviewed, which splits the problem into two parts: a spatial search followed by a temporal correlation problem. Two specific implementations of the spatial search algorithm are compared. The commonly used grid point search algorithm is reviewed, and a new algorithm called Stride Search is introduced. Stride Search is designed to work at all latitudes, while grid point searches may fail in polar regions. Results from the two algorithms are compared for the application of tropicalmore » cyclone detection, and shown to produce similar results for the same set of storm identification criteria. The time required for both algorithms to search the same data set is compared. Furthermore, Stride Search's ability to search extreme latitudes is demonstrated for the case of polar low detection.« less

Walking on an Oscillating Treadmill: Two Paths to Functional Adaptation

NASA Technical Reports Server (NTRS)

Brady, Rachel A.; Peters, Brian T.; Bloomberg, Jacob J.

2010-01-01

We mounted a treadmill on top of a six degree-of-freedom motion base platform to investigate and characterize locomotor responses produced by healthy adults when introduced to a novel walking condition. Subjects were classified into two groups according to how their stride times were affected by the perturbation. Our data suggest that a person's choice of adaptation strategy is influenced by the relationship between his unique, natural stride frequency and the external frequency imposed by the motion base. Our data suggest that a person's stride time response while walking on a laterally oscillating treadmill is influenced by the relationship between his unique, natural stride frequency and the imposed external frequency of the motion base. This relationship may be useful for checking the efficacy of gait training and rehabilitation programs. Preselecting and manipulating a person's EST could be one way to draw him out of his preferred "entrainment well" during therapy or training.

19 CFR 10.242 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-04-01

... knitting machine. Several components with finished edges may be linked by yarn or thread as they are... reference to fabric components, means that all of the production processes, starting with the production of... fabric(s), means that all of the production processes, starting with polymers, fibers, filaments, textile...

19 CFR 10.242 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-04-01

... knitting machine. Several components with finished edges may be linked by yarn or thread as they are... reference to fabric components, means that all of the production processes, starting with the production of... fabric(s), means that all of the production processes, starting with polymers, fibers, filaments, textile...

19 CFR 10.242 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-04-01

... knitting machine. Several components with finished edges may be linked by yarn or thread as they are... reference to fabric components, means that all of the production processes, starting with the production of... fabric(s), means that all of the production processes, starting with polymers, fibers, filaments, textile...

19 CFR 10.242 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-04-01

... knitting machine. Several components with finished edges may be linked by yarn or thread as they are... reference to fabric components, means that all of the production processes, starting with the production of... fabric(s), means that all of the production processes, starting with polymers, fibers, filaments, textile...

19 CFR 10.242 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-04-01

... knitting machine. Several components with finished edges may be linked by yarn or thread as they are... reference to fabric components, means that all of the production processes, starting with the production of... fabric(s), means that all of the production processes, starting with polymers, fibers, filaments, textile...

The ambiguity about death in Japan: an ethical implication for organ procurement.

PubMed Central

McConnell, J R

1999-01-01

In the latter half of the twentieth century, developed countries of the world have made tremendous strides in organ donation and transplantation. However, in this area of medicine, Japan has been slow to follow. Japanese ethics, deeply rooted in religion and tradition, have affected their outlook on life and death. Because the Japanese have only recently started to acknowledge the concept of brain death, transplantation of major organs has been hindered in that country. Currently, there is a dual definition of death in Japan, intended to satisfy both sides of the issue. This interesting paradox, which still stands to be fully resolved, illustrates the contentious conflict between medical ethics and medical progress in Japan. PMID:10461595

Growth factors in urologic tissues: detection, characterization, and clinical applications.

PubMed

Mydlo, J H; Macchia, R J

1992-12-01

During the last two decades, enormous strides have been made in understanding cellular and molecular biology. The direction of treatment of many neoplasms and other diseases are starting at the microscopic level. Growth factors are polypeptides that play a part in the development and maintenance of living tissues. We, as well as others, have investigated the role that growth factors play particularly in urologic tissues, both benign and malignant. We review several well-known growth factors and their function in prostate, kidney, and bladder tissues, as well as their functions in other regulating processes of the human body, and also the use of growth factors as tumor markers, and antibodies to growth factors as possible treatment of disease.

Increased gait unsteadiness in community-dwelling elderly fallers

NASA Technical Reports Server (NTRS)

Hausdorff, J. M.; Edelberg, H. K.; Mitchell, S. L.; Goldberger, A. L.; Wei, J. Y.

1997-01-01

OBJECTIVE: To test the hypothesis that quantitative measures of gait unsteadiness are increased in community-dwelling elderly fallers. STUDY DESIGN: Retrospective, case-control study. SETTING: General community. PARTICIPANTS: Thirty-five community-dwelling elderly subjects older than 70 years of age who were capable of ambulating independently for 6 minutes were categorized as fallers (age, 82.2 +/- 4.9 yrs [mean +/- SD]; n = 18) and nonfallers (age, 76.5 +/- 4.0 yrs; n = 17) based on history; 22 young (age, 24.6 +/- 1.9 yrs), healthy subjects also participated as a second reference group. MAIN OUTCOME MEASURES: Stride-to-stride variability (standard deviation and coefficient of variation) of stride time, stance time, swing time, and percent stance time measured during a 6-minute walk. RESULTS: All measures of gait variability were significantly greater in the elderly fallers compared with both the elderly nonfallers and the young subjects (p < .0002). In contrast, walking speed of the elderly fallers was similar to that of the nonfallers. There were little or no differences in the variability measures of the elderly nonfallers compared with the young subjects. CONCLUSIONS: Stride-to-stride temporal variations of gait are relatively unchanged in community-dwelling elderly nonfallers, but are significantly increased in elderly fallers. Quantitative measurement of gait unsteadiness may be useful in assessing fall risk in the elderly.

Effects of high doses of oxytetracycline on metacarpophalangeal joint kinematics in neonatal foals.

PubMed

Kasper, C A; Clayton, H M; Wright, A K; Skuba, E V; Petrie, L

1995-07-01

Thirteen clinically normal Belgian-type foals were used to study the effects of high doses of oxytetracycline on metacarpophalangeal joint kinematics. Seven foals (treatment group) received 2 doses of oxytetracycline (3 g, IV). The first dose was given when foals were 4 days old; the second dose was given 24 hours later. Six foals (control group) received 2 doses of saline (0.9% NaCl) solution (15 ml, IV) at equivalent time periods. All foals were videotaped at a walk twice: immediately prior to the first treatment and 24 hours after the second treatment. The tapes were digitized, and metacarpophalangeal joint angle was measured along the palmar surface of the limb during 3 strides. The angular data were normalized for time, and data from the 3 strides were averaged to describe a representative stride. Repeated measures ANOVA was used to test for differences between groups and within groups over time. Values for stride duration, stance phase percentage, and minimum metacarpophalangeal joint angle obtained before treatment were not significantly different from values obtained after treatment. Maximum metacarpophalangeal joint angle, which occurred during the stance phase of the stride, and range of joint motion were significantly increased for foals in the treatment group, compared with foals in the control group.

Advanced Metallic Air Vehicle Structure Program

DTIC Science & Technology

1974-06-01

soapstone line around the periphery of the lower plate from XFO.00 to the outboard edge using edge of MSLO X7224175 as guide. Remove MSLO X7224175. D...hole in the lug reinforcement plates). Make soapstone line to edge of MSLO to denote periphery of cutouts. E. Relocate MSLO X7224175 on opposite end of...of plate). G. Drill .50 diameter holes (10) using the Bux- Magnetic drill unit. See MAP-I-3 for approximate locations of these start and stop holes. A 1

Kinematic variability, fractal dynamics and local dynamic stability of treadmill walking

PubMed Central

2011-01-01

Background Motorized treadmills are widely used in research or in clinical therapy. Small kinematics, kinetics and energetics changes induced by Treadmill Walking (TW) as compared to Overground Walking (OW) have been reported in literature. The purpose of the present study was to characterize the differences between OW and TW in terms of stride-to-stride variability. Classical (Standard Deviation, SD) and non-linear (fractal dynamics, local dynamic stability) methods were used. In addition, the correlations between the different variability indexes were analyzed. Methods Twenty healthy subjects performed 10 min TW and OW in a random sequence. A triaxial accelerometer recorded trunk accelerations. Kinematic variability was computed as the average SD (MeanSD) of acceleration patterns among standardized strides. Fractal dynamics (scaling exponent α) was assessed by Detrended Fluctuation Analysis (DFA) of stride intervals. Short-term and long-term dynamic stability were estimated by computing the maximal Lyapunov exponents of acceleration signals. Results TW did not modify kinematic gait variability as compared to OW (multivariate T2, p = 0.87). Conversely, TW significantly modified fractal dynamics (t-test, p = 0.01), and both short and long term local dynamic stability (T2 p = 0.0002). No relationship was observed between variability indexes with the exception of significant negative correlation between MeanSD and dynamic stability in TW (3 × 6 canonical correlation, r = 0.94). Conclusions Treadmill induced a less correlated pattern in the stride intervals and increased gait stability, but did not modify kinematic variability in healthy subjects. This could be due to changes in perceptual information induced by treadmill walking that would affect locomotor control of the gait and hence specifically alter non-linear dependencies among consecutive strides. Consequently, the type of walking (i.e. treadmill or overground) is important to consider in each protocol design. PMID:21345241

Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance.

PubMed

Dorn, Tim W; Schache, Anthony G; Pandy, Marcus G

2012-06-01

Humans run faster by increasing a combination of stride length and stride frequency. In slow and medium-paced running, stride length is increased by exerting larger support forces during ground contact, whereas in fast running and sprinting, stride frequency is increased by swinging the legs more rapidly through the air. Many studies have investigated the mechanics of human running, yet little is known about how the individual leg muscles accelerate the joints and centre of mass during this task. The aim of this study was to describe and explain the synergistic actions of the individual leg muscles over a wide range of running speeds, from slow running to maximal sprinting. Experimental gait data from nine subjects were combined with a detailed computer model of the musculoskeletal system to determine the forces developed by the leg muscles at different running speeds. For speeds up to 7 m s(-1), the ankle plantarflexors, soleus and gastrocnemius, contributed most significantly to vertical support forces and hence increases in stride length. At speeds greater than 7 m s(-1), these muscles shortened at relatively high velocities and had less time to generate the forces needed for support. Thus, above 7 m s(-1), the strategy used to increase running speed shifted to the goal of increasing stride frequency. The hip muscles, primarily the iliopsoas, gluteus maximus and hamstrings, achieved this goal by accelerating the hip and knee joints more vigorously during swing. These findings provide insight into the strategies used by the leg muscles to maximise running performance and have implications for the design of athletic training programs.

Biologically-variable rhythmic auditory cues are superior to isochronous cues in fostering natural gait variability in Parkinson's disease.

PubMed

Dotov, D G; Bayard, S; Cochen de Cock, V; Geny, C; Driss, V; Garrigue, G; Bardy, B; Dalla Bella, S

2017-01-01

Rhythmic auditory cueing improves certain gait symptoms of Parkinson's disease (PD). Cues are typically stimuli or beats with a fixed inter-beat interval. We show that isochronous cueing has an unwanted side-effect in that it exacerbates one of the motor symptoms characteristic of advanced PD. Whereas the parameters of the stride cycle of healthy walkers and early patients possess a persistent correlation in time, or long-range correlation (LRC), isochronous cueing renders stride-to-stride variability random. Random stride cycle variability is also associated with reduced gait stability and lack of flexibility. To investigate how to prevent patients from acquiring a random stride cycle pattern, we tested rhythmic cueing which mimics the properties of variability found in healthy gait (biological variability). PD patients (n=19) and age-matched healthy participants (n=19) walked with three rhythmic cueing stimuli: isochronous, with random variability, and with biological variability (LRC). Synchronization was not instructed. The persistent correlation in gait was preserved only with stimuli with biological variability, equally for patients and controls (p's<0.05). In contrast, cueing with isochronous or randomly varying inter-stimulus/beat intervals removed the LRC in the stride cycle. Notably, the individual's tendency to synchronize steps with beats determined the amount of negative effects of isochronous and random cues (p's<0.05) but not the positive effect of biological variability. Stimulus variability and patients' propensity to synchronize play a critical role in fostering healthier gait dynamics during cueing. The beneficial effects of biological variability provide useful guidelines for improving existing cueing treatments. Copyright © 2016 Elsevier B.V. All rights reserved.

The effect of three different types of walking aids on spatio-temporal gait parameters in community-dwelling older adults.

PubMed

Härdi, Irene; Bridenbaugh, Stephanie A; Gschwind, Yves J; Kressig, Reto W

2014-04-01

Gait and balance impairments lead to falls and injuries in older people. Walking aids are meant to increase gait safety and prevent falls, yet little is known about how their use alters gait parameters. This study aimed to quantify gait in older adults during walking without and with different walking aids and to compare gait parameters to matched controls. This retrospective study included 65 older (≥60 years) community dwellers who used a cane, crutch or walker and 195 independently mobile-matched controls. Spatio-temporal gait parameters were measured with an electronic walkway system during normal walking. When walking unaided or aided, walking aid users had significantly worse gait than matched controls. Significant differences between the walking aid groups were found for stride time variability (cane vs. walker) in walking unaided only. Gait performances significantly improved when assessed with vs. without the walking aid for the cane (increased stride time and length, decreased cadence and stride length variability), crutch (increased stride time and length, decreased cadence, stride length variability and double support) and walker (increased gait speed and stride length, decreased base of support and double support) users. Gait in older adults who use a walking aid is more irregular and unstable than gait in independently mobile older adults. Walking aid users have better gait when using their walking aid than when walking without it. The changes in gait were different for the different types of walking aids used. These study results may help better understand gait in older adults and differentiate between pathological gait changes and compensatory gait changes due to the use of a walking aid.

Residual standard deviation: Validation of a new measure of dual-task cost in below-knee prosthesis users.

PubMed

Howard, Charla L; Wallace, Chris; Abbas, James; Stokic, Dobrivoje S

2017-01-01

We developed and evaluated properties of a new measure of variability in stride length and cadence, termed residual standard deviation (RSD). To calculate RSD, stride length and cadence are regressed against velocity to derive the best fit line from which the variability (SD) of the distance between the actual and predicted data points is calculated. We examined construct, concurrent, and discriminative validity of RSD using dual-task paradigm in 14 below-knee prosthesis users and 13 age- and education-matched controls. Subjects walked first over an electronic walkway while performing separately a serial subtraction and backwards spelling task, and then at self-selected slow, normal, and fast speeds used to derive the best fit line for stride length and cadence against velocity. Construct validity was demonstrated by significantly greater increase in RSD during dual-task gait in prosthesis users than controls (group-by-condition interaction, stride length p=0.0006, cadence p=0.009). Concurrent validity was established against coefficient of variation (CV) by moderate-to-high correlations (r=0.50-0.87) between dual-task cost RSD and dual-task cost CV for both stride length and cadence in prosthesis users and controls. Discriminative validity was documented by the ability of dual-task cost calculated from RSD to effectively differentiate prosthesis users from controls (area under the receiver operating characteristic curve, stride length 0.863, p=0.001, cadence 0.808, p=0.007), which was better than the ability of dual-task cost CV (0.692, 0.648, respectively, not significant). These results validate RSD as a new measure of variability in below-knee prosthesis users. Future studies should include larger cohorts and other populations to ascertain its generalizability. Copyright © 2016 Elsevier B.V. All rights reserved.

Differential effects of absent visual feedback control on gait variability during different locomotion speeds.

PubMed

Wuehr, M; Schniepp, R; Pradhan, C; Ilmberger, J; Strupp, M; Brandt, T; Jahn, K

2013-01-01

Healthy persons exhibit relatively small temporal and spatial gait variability when walking unimpeded. In contrast, patients with a sensory deficit (e.g., polyneuropathy) show an increased gait variability that depends on speed and is associated with an increased fall risk. The purpose of this study was to investigate the role of vision in gait stabilization by determining the effects of withdrawing visual information (eyes closed) on gait variability at different locomotion speeds. Ten healthy subjects (32.2 ± 7.9 years, 5 women) walked on a treadmill for 5-min periods at their preferred walking speed and at 20, 40, 70, and 80 % of maximal walking speed during the conditions of walking with eyes open (EO) and with eyes closed (EC). The coefficient of variation (CV) and fractal dimension (α) of the fluctuations in stride time, stride length, and base width were computed and analyzed. Withdrawing visual information increased the base width CV for all walking velocities (p < 0.001). The effects of absent visual information on CV and α of stride time and stride length were most pronounced during slow locomotion (p < 0.001) and declined during fast walking speeds. The results indicate that visual feedback control is used to stabilize the medio-lateral (i.e., base width) gait parameters at all speed sections. In contrast, sensory feedback control in the fore-aft direction (i.e., stride time and stride length) depends on speed. Sensory feedback contributes most to fore-aft gait stabilization during slow locomotion, whereas passive biomechanical mechanisms and an automated central pattern generation appear to control fast locomotion.

A PDF-based classification of gait cadence patterns in patients with amyotrophic lateral sclerosis.

PubMed

Wu, Yunfeng; Ng, Sin Chun

2010-01-01

Amyotrophic lateral sclerosis (ALS) is a type of neurological disease due to the degeneration of motor neurons. During the course of such a progressive disease, it would be difficult for ALS patients to regulate normal locomotion, so that the gait stability becomes perturbed. This paper presents a pilot statistical study on the gait cadence (or stride interval) in ALS, based on the statistical analysis method. The probability density functions (PDFs) of stride interval were first estimated with the nonparametric Parzen-window method. We computed the mean of the left-foot stride interval and the modified Kullback-Leibler divergence (MKLD) from the PDFs estimated. The analysis results suggested that both of these two statistical parameters were significantly altered in ALS, and the least-squares support vector machine (LS-SVM) may effectively distinguish the stride patterns between the ALS patients and healthy controls, with an accurate rate of 82.8% and an area of 0.87 under the receiver operating characteristic curve.

The Effect of a Six-Month Dancing Program on Motor-Cognitive Dual-Task Performance in Older Adults.

PubMed

Hamacher, Dennis; Hamacher, Daniel; Rehfeld, Kathrin; Hökelmann, Anita; Schega, Lutz

2015-10-01

Dancing is a complex sensorimotor activity involving physical and mental elements which have positive effects on cognitive functions and motor control. The present randomized controlled trial aims to analyze the effects of a dancing program on the performance on a motor-cognitive dual task. Data of 35 older adults, who were assigned to a dancing group or a health-related exercise group, are presented in the study. In pretest and posttest, we assessed cognitive performance and variability of minimum foot clearance, stride time, and stride length while walking. Regarding the cognitive performance and the stride-to-stride variability of minimum foot clearance, interaction effects have been found, indicating that dancing lowers gait variability to a higher extent than conventional health-related exercise. The data show that dancing improves minimum foot clearance variability and cognitive performance in a dual-task situation. Multi-task exercises (like dancing) might be a powerful tool to improve motor-cognitive dual-task performance.

Evaluation of the Applicability of HTML5 for Mobile Applications in Resource-Constrained Edge Environments

DTIC Science & Technology

2014-07-01

iOS, Blackberry , Windows Phone) and installed directly onto the device itself. CMU/SEI-2014-TN-002 | 2 2 Background 2.1 Edge Applications We...since this research started and adoption of HTML5 is growing . There are entire operating systems currently being developed in HTML5, such as Firefox

Sampling Operations on Big Data

DTIC Science & Technology

2015-11-29

gories. These include edge sampling methods where edges are selected by a predetermined criteria; snowball sampling methods where algorithms start... Sampling Operations on Big Data Vijay Gadepally, Taylor Herr, Luke Johnson, Lauren Milechin, Maja Milosavljevic, Benjamin A. Miller Lincoln...process and disseminate information for discovery and exploration under real-time constraints. Common signal processing operations such as sampling and

Effect of step-synchronized vibration stimulation of soles on gait in Parkinson's disease: a pilot study.

PubMed

Novak, Peter; Novak, Vera

2006-05-04

Previous studies have suggested that impaired proprioceptive processing in the striatum may contribute to abnormal gait in Parkinson's disease (PD). This pilot study assessed the effects of enhanced proprioceptive feedback using step-synchronized vibration stimulation of the soles (S-VS) on gait in PD. S-VS was used in 8 PD subjects (3 women and 5 men, age range 44-79 years, on medication) and 8 age-matched healthy subjects (5 women and 3 men). PD subjects had mild or moderate gait impairment associated with abnormal balance, but they did not have gait freezing. Three vibratory devices (VDs) were embedded in elastic insoles (one below the heel and two below the forefoot areas) inserted into the shoes. Each VD operates independently and has a pressure switch that activates the underlying vibratory actuator. The VD delivered the 70-Hz suprathreshold vibration pulse upon touch by the heel or forefoot, and the vibration pulse was deactivated upon respective push-offs. Six-minute hallway walking was studied with and without S-VS. Gait characteristics were measured using the force-sensitive foot switches. The primary outcome was the stride variability expressed as a coefficient of variation (CV), a measure of gait steadiness. Secondary outcome measures were walking distance and speed, stride length and duration, cadence, stance, swing and double support duration, and respective CVs (if applicable). The walking speed (p < 0.04) and the CV of the stride interval (p < 0.02) differed between the groups and S-VS conditions. In the PD group, S-VS decreased stride variability (p < 0.002), increased walking speed (p < 0.0001), stride duration (p < 0.01), stride length (p < 0.0002), and cadence (p < 0.03). In the control group, S-VS decreased stride variability (p < 0.006) and increased gait speed (p < 0.03), but other locomotion parameters were not significantly altered. Augmented sensory feedback improves parkinsonian gait steadiness in the short-term setting. Because the suprathreshold stimulation prevented blinding of subjects, the learning effect and increased attention can be a confounding factor underlying results. Long-term studies are needed to establish the clinical value of the S-VS.

Acute differences in foot strike and spatiotemporal variables for shod, barefoot or minimalist male runners.

PubMed

McCallion, Ciara; Donne, Bernard; Fleming, Neil; Blanksby, Brian

2014-05-01

This study compared stride length, stride frequency, contact time, flight time and foot-strike patterns (FSP) when running barefoot, and in minimalist and conventional running shoes. Habitually shod male athletes (n = 14; age 25 ± 6 yr; competitive running experience 8 ± 3 yr) completed a randomised order of 6 by 4-min treadmill runs at velocities (V1 and V2) equivalent to 70 and 85% of best 5-km race time, in the three conditions. Synchronous recording of 3-D joint kinematics and ground reaction force data examined spatiotemporal variables and FSP. Most participants adopted a mid-foot strike pattern, regardless of condition. Heel-toe latency was less at V2 than V1 (-6 ± 20 vs. -1 ± 13 ms, p < 0.05), which indicated a velocity related shift towards a more FFS pattern. Stride duration and flight time, when shod and in minimalist footwear, were greater than barefoot (713 ± 48 and 701 ± 49 vs. 679 ± 56 ms, p < 0.001; and 502 ± 45 and 503 ± 41 vs. 488 ±4 9 ms, p < 0.05, respectively). Contact time was significantly longer when running shod than barefoot or in minimalist footwear (211±30 vs. 191 ± 29 ms and 198 ± 33 ms, p < 0.001). When running barefoot, stride frequency was significantly higher (p < 0.001) than in conventional and minimalist footwear (89 ± 7 vs. 85 ± 6 and 86 ± 6 strides·min(-1)). In conclusion, differences in spatiotemporal variables occurred within a single running session, irrespective of barefoot running experience, and, without a detectable change in FSP. Key pointsDifferences in spatiotemporal variables occurred within a single running session, without a change in foot strike pattern.Stride duration and flight time were greater when shod and in minimalist footwear than when barefoot.Stride frequency when barefoot was higher than when shod or in minimalist footwear.Contact time when shod was longer than when barefoot or in minimalist footwear.Spatiotemporal variables when running in minimalist footwear more closely resemble shod than barefoot running.

Acute Differences in Foot Strike and Spatiotemporal Variables for Shod, Barefoot or Minimalist Male Runners

PubMed Central

McCallion, Ciara; Donne, Bernard; Fleming, Neil; Blanksby, Brian

2014-01-01

This study compared stride length, stride frequency, contact time, flight time and foot-strike patterns (FSP) when running barefoot, and in minimalist and conventional running shoes. Habitually shod male athletes (n = 14; age 25 ± 6 yr; competitive running experience 8 ± 3 yr) completed a randomised order of 6 by 4-min treadmill runs at velocities (V1 and V2) equivalent to 70 and 85% of best 5-km race time, in the three conditions. Synchronous recording of 3-D joint kinematics and ground reaction force data examined spatiotemporal variables and FSP. Most participants adopted a mid-foot strike pattern, regardless of condition. Heel-toe latency was less at V2 than V1 (-6 ± 20 vs. -1 ± 13 ms, p < 0.05), which indicated a velocity related shift towards a more FFS pattern. Stride duration and flight time, when shod and in minimalist footwear, were greater than barefoot (713 ± 48 and 701 ± 49 vs. 679 ± 56 ms, p < 0.001; and 502 ± 45 and 503 ± 41 vs. 488 ±4 9 ms, p < 0.05, respectively). Contact time was significantly longer when running shod than barefoot or in minimalist footwear (211±30 vs. 191 ± 29 ms and 198 ± 33 ms, p < 0.001). When running barefoot, stride frequency was significantly higher (p < 0.001) than in conventional and minimalist footwear (89 ± 7 vs. 85 ± 6 and 86 ± 6 strides·min-1). In conclusion, differences in spatiotemporal variables occurred within a single running session, irrespective of barefoot running experience, and, without a detectable change in FSP. Key points Differences in spatiotemporal variables occurred within a single running session, without a change in foot strike pattern. Stride duration and flight time were greater when shod and in minimalist footwear than when barefoot. Stride frequency when barefoot was higher than when shod or in minimalist footwear. Contact time when shod was longer than when barefoot or in minimalist footwear. Spatiotemporal variables when running in minimalist footwear more closely resemble shod than barefoot running. PMID:24790480

Path tortuosity in everyday movements of elderly persons increases fall prediction beyond knowledge of fall history, medication use, and standardized gait and balance assessments.

PubMed

Kearns, William D; Fozard, James L; Becker, Marion; Jasiewicz, Jan M; Craighead, Jeffrey D; Holtsclaw, Lori; Dion, Charles

2012-09-01

We hypothesized that variability in voluntary movement paths of assisted living facility (ALF) residents would be greater in the week preceding a fall compared with residents who did not fall. Prospective, observational study using telesurveillance technology. Two ALFs. The sample consisted of 69 older ALF residents (53 female) aged 76.9 (SD ± 11.9 years). Daytime movement in ALF common use areas was automatically tracked using a commercially available ultra-wideband radio real-time location sensor network with a spatial resolution of approximately 20 cm. Movement path variability (tortuosity) was gauged using fractal dimension (fractal D). A logistic regression was performed predicting movement related falls from fractal D, presence of a fall in the prior year, psychoactive medication use, and movement path length. Fallers and non-fallers were also compared on activities of daily living requiring supervision or assistance, performance on standardized static and dynamic balance, and stride velocity assessments gathered at the start of a 1-year fall observation period. Fall risk due to cognitive deficit was assessed by the Mini Mental Status Examination (MMSE), and by clinical dementia diagnoses from participant's activities of daily living health record. Logistic regression analysis revealed odds of falling increased 2.548 (P = .021) for every 0.1 increase in fractal D, and having a fall in the prior year increased odds of falling by 7.36 (P = .006). There was a trend for longer movement paths to reduce the odds of falling (OR .976 P = .08) but it was not significant. Number of psychoactive medications did not contribute significantly to fall prediction in the model. Fallers had more variable stride-to-stride velocities and required more activities of daily living assistance. High fractal D levels can be detected using commercially available telesurveillance technologies and offers a new tool for health services administrators seeking to reduce falls at their facilities. Copyright © 2012 American Medical Directors Association. Published by Elsevier Inc. All rights reserved.

Gait disorders in the elderly and dual task gait analysis: a new approach for identifying motor phenotypes.

PubMed

Auvinet, Bernard; Touzard, Claude; Montestruc, François; Delafond, Arnaud; Goeb, Vincent

2017-01-31

Gait disorders and gait analysis under single and dual-task conditions are topics of great interest, but very few studies have looked for the relevance of gait analysis under dual-task conditions in elderly people on the basis of a clinical approach. An observational study including 103 patients (mean age 76.3 ± 7.2, women 56%) suffering from gait disorders or memory impairment was conducted. Gait analysis under dual-task conditions was carried out for all patients. Brain MRI was performed in the absence of contra-indications. Three main gait variables were measured: walking speed, stride frequency, and stride regularity. For each gait variable, the dual task cost was computed and a quartile analysis was obtained. Nonparametric tests were used for all the comparisons (Wilcoxon, Kruskal-Wallis, Fisher or Chi 2 tests). Four clinical subgroups were identified: gait instability (45%), recurrent falls (29%), memory impairment (18%), and cautious gait (8%). The biomechanical severity of these subgroups was ordered according to walking speed and stride regularity under both conditions, from least to most serious as follows: memory impairment, gait instability, recurrent falls, cautious gait (p < 0.01 for walking speed, p = 0.05 for stride regularity). According to the established diagnoses of gait disorders, 5 main pathological subgroups were identified (musculoskeletal diseases (n = 11), vestibular diseases (n = 6), mild cognitive impairment (n = 24), central nervous system pathologies, (n = 51), and without diagnosis (n = 8)). The dual task cost for walking speed, stride frequency and stride regularity were different among these subgroups (p < 0.01). The subgroups mild cognitive impairment and central nervous system pathologies both showed together a higher dual task cost for each variable compared to the other subgroups combined (p = 0.01). The quartile analysis of dual task cost for stride frequency and stride regularity allowed the identification of 3 motor phenotypes (p < 0.01), without any difference for white matter hyperintensities, but with an increased Scheltens score from the first to the third motor phenotype (p = 0.05). Gait analysis under dual-task conditions in elderly people suffering from gait disorders or memory impairment is of great value in assessing the severity of gait disorders, differentiating between peripheral pathologies and central nervous system pathologies, and identifying motor phenotypes. Correlations between motor phenotypes and brain imaging require further studies.

Spatiotemporal characteristics of motor actions by blind long jump athletes.

PubMed

Torralba, Miguel Angel; Padullés, José María; Losada, Jose Luis; López, Jose Luis

2017-01-01

Blind people depend on spatial and temporal representations to perform activities of daily living and compete in sport. The aim of this study is to determine the spatiotemporal characteristics of long jumps performed by blind athletes and compare findings with those reported for sighted athletes. We analysed a sample of 12 male athletes competing in the F11 Long Jump Finals at the Paralympic Games in London 2012. Performances were recorded using four high-speed cameras, and speeds were measured using a radar speed gun. The images were processed using validated image analysis software. The long jump run-up is shorter in blind athletes than in sighted athletes. We observed statistically significant differences for body centre of mass velocity and an increase in speed over the last three strides prior to take-off, contrasting with reports for sighted athletes and athletes with less severe visual impairment, who maintain or reduce their speed during the last stride. Stride length for the last three strides was the only spatial characteristic that was not significantly associated with effective jump distance. Blind long jumpers extend rather than shorten their last stride. Contact time with the take-off board is longer than that reported for sighted athletes. The actions of blind long jumpers, unlike those without disabilities, do not vary their leg actions during the final runway approach for optimal placement on the take-off board.

Altered fractal dynamics of gait: reduced stride-interval correlations with aging and Huntington's disease

NASA Technical Reports Server (NTRS)

Hausdorff, J. M.; Mitchell, S. L.; Firtion, R.; Peng, C. K.; Cudkowicz, M. E.; Wei, J. Y.; Goldberger, A. L.

1997-01-01

Fluctuations in the duration of the gait cycle (the stride interval) display fractal dynamics and long-range correlations in healthy young adults. We hypothesized that these stride-interval correlations would be altered by changes in neurological function associated with aging and certain disease states. To test this hypothesis, we compared the stride-interval time series of 1) healthy elderly subjects and young controls and of 2) subjects with Huntington's disease and healthy controls. Using detrended fluctuation analysis we computed alpha, a measure of the degree to which one stride interval is correlated with previous and subsequent intervals over different time scales. The scaling exponent alpha was significantly lower in elderly subjects compared with young subjects (elderly: 0.68 +/- 0.14; young: 0.87 +/- 0.15; P < 0.003). The scaling exponent alpha was also smaller in the subjects with Huntington's disease compared with disease-free controls (Huntington's disease: 0.60 +/- 0.24; controls: 0.88 +/-0.17; P < 0.005). Moreover, alpha was linearly related to degree of functional impairment in subjects with Huntington's disease (r = 0.78, P < 0.0005). These findings demonstrate that strike-interval fluctuations are more random (i.e., less correlated) in elderly subjects and in subjects with Huntington's disease. Abnormal alterations in the fractal properties of gait dynamics are apparently associated with changes in central nervous system control.

Energy Expenditure of Trotting Gait Under Different Gait Parameters

NASA Astrophysics Data System (ADS)

Chen, Xian-Bao; Gao, Feng

2017-07-01

Robots driven by batteries are clean, quiet, and can work indoors or in space. However, the battery endurance is a great problem. A new gait parameter design energy saving strategy to extend the working hours of the quadruped robot is proposed. A dynamic model of the robot is established to estimate and analyze the energy expenditures during trotting. Given a trotting speed, optimal stride frequency and stride length can minimize the energy expenditure. However, the relationship between the speed and the optimal gait parameters is nonlinear, which is difficult for practical application. Therefore, a simplified gait parameter design method for energy saving is proposed. A critical trotting speed of the quadruped robot is found and can be used to decide the gait parameters. When the robot is travelling lower than this speed, it is better to keep a constant stride length and change the cycle period. When the robot is travelling higher than this speed, it is better to keep a constant cycle period and change the stride length. Simulations and experiments on the quadruped robot show that by using the proposed gait parameter design approach, the energy expenditure can be reduced by about 54% compared with the 100 mm stride length under 500 mm/s speed. In general, an energy expenditure model based on the gait parameter of the quadruped robot is built and the trotting gait parameters design approach for energy saving is proposed.

The hindlimb in walking horses: 2. Net joint moments and joint powers.

PubMed

Clayton, H M; Hodson, E; Lanovaz, J L; Colborne, G R

2001-01-01

The objective of the study was to describe net joint moments and joint powers in the equine hindlimb during walking. The subjects were 5 sound horses. Kinematic and force data were collected synchronously and combined with morphometric information to determine net joint moments at each hindlimb joint throughout stance and swing. The results showed that the net joint moment was on the caudal/plantar side of all hindlimb joints at the start of stance when the limb was being actively retracted. It moved to the cranial/dorsal side around 24% stride at the hip and stifle and in terminal stance at the more distal joints. It remained on the cranial/dorsal side of all joints during the first half of swing to provide active limb protraction, then moved to the caudal/plantar aspect to reverse the direction of limb motion prior to ground contact. The hip joint was the main source of energy generation throughout the stride. It was assisted by the tarsal joint in both stance and swing phases and by the fetlock joint during the stance phase. The coffin joint acted as an energy damper during stance, whereas the stifle joint absorbed almost equal amounts of energy in the stance and swing phases. The coffin and fetlock joints absorbed energy as the limb was protracted and retracted during the swing phase, suggesting that their movements were driven by inertial forces. Future studies will apply these findings to detect changes in the energy profiles due to specific soft tissue injuries.

28 CFR 16.98 - Exemption of the Drug Enforcement Administration (DEA)-limited access.

Code of Federal Regulations, 2012 CFR

2012-07-01

... (Justice/DEA-013) (7) System to Retrieve Information from Drug Evidence (STRIDE/Ballistics) (Justice/DEA... Retrieve Information from Drug Evidence (STRIDE/Ballistics) (Justice/DEA-014) only to the extent that..., implemented internal quality assurance procedures to ensure that ESS data is as thorough, accurate, and...

28 CFR 16.98 - Exemption of the Drug Enforcement Administration (DEA)-limited access.

Code of Federal Regulations, 2011 CFR

2011-07-01

... (Justice/DEA-013) (7) System to Retrieve Information from Drug Evidence (STRIDE/Ballistics) (Justice/DEA... Retrieve Information from Drug Evidence (STRIDE/Ballistics) (Justice/DEA-014) only to the extent that..., implemented internal quality assurance procedures to ensure that ESS data is as thorough, accurate, and...

When human walking becomes random walking: fractal analysis and modeling of gait rhythm fluctuations

NASA Astrophysics Data System (ADS)

Hausdorff, Jeffrey M.; Ashkenazy, Yosef; Peng, Chang-K.; Ivanov, Plamen Ch.; Stanley, H. Eugene; Goldberger, Ary L.

2001-12-01

We present a random walk, fractal analysis of the stride-to-stride fluctuations in the human gait rhythm. The gait of healthy young adults is scale-free with long-range correlations extending over hundreds of strides. This fractal scaling changes characteristically with maturation in children and older adults and becomes almost completely uncorrelated with certain neurologic diseases. Stochastic modeling of the gait rhythm dynamics, based on transitions between different “neural centers”, reproduces distinctive statistical properties of the gait pattern. By tuning one model parameter, the hopping (transition) range, the model can describe alterations in gait dynamics from childhood to adulthood - including a decrease in the correlation and volatility exponents with maturation.

Compressible Navier-Stokes Equations in a Polyhedral Cylinder with Inflow Boundary Condition

NASA Astrophysics Data System (ADS)

Kwon, Ohsung; Kweon, Jae Ryong

2018-06-01

In this paper our concern is with singularity and regularity of the compressible flows through a non-convex edge in R^3. The flows are governed by the compressible Navies-Stokes equations on the infinite cylinder that has the non-convex edge on the inflow boundary. We split the edge singularity by the Poisson problem from the velocity vector and show that the remainder is twice differentiable while the edge singularity is observed to be propagated into the interior of the cylinder by the transport character of the continuity equation. An interior surface layer starting at the edge is generated and not Lipshitz continuous due to the singularity. The density function shows a very steep change near the interface and its normal derivative has a jump discontinuity across there.

Project STRIDE: Services for Transition to Independence through Education. Final Report, July 1988-June 1990 [and] Manual.

ERIC Educational Resources Information Center

Ross-Gordon, Jovita M.; And Others

The Services for Transition to Independence through Education (STRIDE) project evaluated a model for providing comprehensive training and employment services to adults with mild handicaps, using existing vocational education classes and special needs support programs in a secondary vocational technical school in Altoona, Pennsylvania. Services…

Greenwashing: Knowing Is Half the Battle

ERIC Educational Resources Information Center

Neugebauer, Adam

2011-01-01

The growing interest in "green" products in recent years has been met stride-for-stride with marketing campaigns attempting to tap into that trend. This once-niche sector was finally becoming mainstream and the market scrambled to meet that demand. Companies and organizations took steps to make themselves and their products and services more…

Can Democracy Represent Children? Toward a Politics of Difference

ERIC Educational Resources Information Center

Wall, John

2012-01-01

Children and youth under 18 have made significant strides in recent years toward fuller inclusion in democratic processes. These strides, however, rarely rise to the level of direct political representation, whether in changing policies, making laws, or voting. This article argues that democracies will be able to represent children only by…

Habituation of 10-year-old hockey players to treadmill skating.

PubMed

Lockwood, Kelly L; Frost, Gail

2007-05-01

This study assessed changes in selected physiological and kinematic variables over 6 weeks of treadmill skating in an effort to understand the process of habituation to this novel training modality. Seven male, Atom-A hockey players who were injury-free and had no previous treadmill skating experience participated in the study. Players performed four 1-min skating bouts at progressively increasing speeds, each week, for 6 weeks. One speed (10.5 km/h) was repeated weekly to allow for assessment of the habituation process. Our criteria for habituation were: a decrease in stride rate, heart rate and rating of perceived exertion, and an increase in stride length, trunk angle and vertical movement of the centre of mass, leading to a plateau, over the course of the 6-week study. Significant decreases were seen in stride rate, heart rate and ratings of perceived exertion, and significant increases were found in stride length. Some of these changes were evident after only one week of training and all were present by week 4. After 6 weeks (24 min) of exposure to treadmill skating, all participants displayed a visibly more efficient skating style.

Effects of gyrokinesis exercise on the gait pattern of female patients with chronic low back pain

PubMed Central

Seo, Kook-Eun; Park, Tae-Jin

2016-01-01

[Purpose] The purpose of the present study was to use kinematic variables to identify the effects of 8/weeks’ performance of a gyrokinesis exercise on the gait pattern of females with chronic low back pain. [Subjects] The subjects of the present study were females in their late 20s to mid 30s who were chronic back pain patients. [Methods] A 3-D motion analysis system was used to measure the changes in their gait patterns between pre and post-gyrokintic exercise. The SPSS 21.0 statistics program was used to perform the paired t-test, to compare the gait patterns of pre-post-gyrokinesis exercise. [Results] In the gait analysis, pre-post-gyrokinesis exercise gait patterns showed statistically significant differences in right and left step length, stride length, right-left step widths, and stride speed. [Conclusion] Gait pattern analysis revealed increases in step length, stride length, and stride speed along with a decrease in step width after 8 weeks of gyrokinesis exercise, demonstrating it improved gait pattern. PMID:27065537

Lower extremity muscle activation during baseball pitching.

PubMed

Campbell, Brian M; Stodden, David F; Nixon, Megan K

2010-04-01

The purpose of this study was to investigate muscle activation levels of select lower extremity muscles during the pitching motion. Bilateral surface electromyography data on 5 lower extremity muscles (biceps femoris, rectus femoris, gluteus maximus, vastus medialis, and gastrocnemius) were collected on 11 highly skilled baseball pitchers and compared with individual maximal voluntary isometric contraction (MVIC) data. The pitching motion was divided into 4 distinct phases: phase 1, initiation of pitching motion to maximum stride leg knee height; phase 2, maximum stride leg knee height to stride foot contact (SFC); phase 3, SFC to ball release; and phase 4, ball release to 0.5 seconds after ball release (follow-through). Results indicated that trail leg musculature elicited moderate to high activity levels during phases 2 and 3 (38-172% of MVIC). Muscle activity levels of the stride leg were moderate to high during phases 2-4 (23-170% of MVIC). These data indicate a high demand for lower extremity strength and endurance. Specifically, coaches should incorporate unilateral and bilateral lower extremity exercises for strength improvement or maintenance and to facilitate dynamic stabilization of the lower extremities during the pitching motion.

Effects of a Flexibility and Relaxation Programme, Walking, and Nordic Walking on Parkinson's Disease

PubMed Central

Reuter, I.; Mehnert, S.; Leone, P.; Kaps, M.; Oechsner, M.; Engelhardt, M.

2011-01-01

Symptoms of Parkinson's disease (PD) progress despite optimized medical treatment. The present study investigated the effects of a flexibility and relaxation programme, walking, and Nordic walking (NW) on walking speed, stride length, stride length variability, Parkinson-specific disability (UPDRS), and health-related quality of life (PDQ 39). 90 PD patients were randomly allocated to the 3 treatment groups. Patients participated in a 6-month study with 3 exercise sessions per week, each lasting 70 min. Assessment after completion of the training showed that pain was reduced in all groups, and balance and health-related quality of life were improved. Furthermore, walking, and Nordic walking improved stride length, gait variability, maximal walking speed, exercise capacity at submaximal level, and PD disease-specific disability on the UPDRS in addition. Nordic walking was superior to the flexibility and relaxation programme and walking in improving postural stability, stride length, gait pattern and gait variability. No significant injuries occurred during the training. All patients of the Nordic walking group continued Nordic walking after completing the study. PMID:21603199

Analysis of walking variability through simultaneous evaluation of the head, lumbar, and lower-extremity acceleration in healthy youth

PubMed Central

Toda, Haruki; Nagano, Akinori; Luo, Zhiwei

2016-01-01

[Purpose] The purpose of this study was to clarify whether walking speed affects acceleration variability of the head, lumbar, and lower extremity by simultaneously evaluating of acceleration. [Subjects and Methods] Twenty young individuals recruited from among the staff at Kurashiki Heisei Hospital participated in this study. Eight accelerometers were used to measure the head, lumbar and lower extremity accelerations. The participants were instructed to walk at five walking speeds prescribed by a metronome. Acceleration variability was assessed by a cross-correlation analysis normalized using z-transform in order to evaluate stride-to-stride variability. [Results] Vertical acceleration variability was the smallest in all body parts, and walking speed effect had laterality. Antero-posterior acceleration variability was significantly associated with walking speed at sites other than the head. Medio-lateral acceleration variability of the bilateral hip alone was smaller than the antero-posterior variability. [Conclusion] The findings of this study suggest that the effect of walking speed changes on the stride-to-stride acceleration variability was individual for each body parts, and differs among directions. PMID:27390419

Effects of different frequencies of rhythmic auditory cueing on the stride length, cadence, and gait speed in healthy young females.

PubMed

Yu, Lili; Zhang, Qi; Hu, Chunying; Huang, Qiuchen; Ye, Miao; Li, Desheng

2015-02-01

[Purpose] The aim of this study was to explore the effects of different frequencies of rhythmic auditory cueing (RAC) on stride length, cadence, and gait speed in healthy young females. The findings of this study might be used as clinical guidance of physical therapy for choosing the suitable frequency of RAC. [Subjects] Thirteen healthy young females were recruited in this study. [Methods] Ten meters walking tests were measured in all subjects under 4 conditions with each repeated 3 times and a 3-min seated rest period between repetitions. Subjects first walked as usual and then were asked to listen carefully to the rhythm of a metronome and walk with 3 kinds of RAC (90%, 100%, and 110% of the mean cadence). The three frequencies (90%, 100%, and 110%) of RAC were randomly assigned. Gait speed, stride length, and cadence were calculated, and a statistical analysis was performed using the SPSS (version 17.0) computer package. [Results] The gait speed and cadence of 90% RAC walking showed significant decreases compared with normal walking and 100% and 110% RAC walking. The stride length, cadence, and gait speed of 110% RAC walking showed significant increases compared with normal walking and 90% and 100% RAC walking. [Conclusion] Our results showed that 110% RAC was the best of the 3 cueing frequencies for improvement of stride length, cadence, and gait speed in healthy young females.

Spatiotemporal characteristics of motor actions by blind long jump athletes

PubMed Central

Torralba, Miguel Angel; Padullés, José María; Losada, Jose Luis; López, Jose Luis

2017-01-01

Background Blind people depend on spatial and temporal representations to perform activities of daily living and compete in sport. Objective The aim of this study is to determine the spatiotemporal characteristics of long jumps performed by blind athletes and compare findings with those reported for sighted athletes. Methods We analysed a sample of 12 male athletes competing in the F11 Long Jump Finals at the Paralympic Games in London 2012. Performances were recorded using four high-speed cameras, and speeds were measured using a radar speed gun. The images were processed using validated image analysis software. Results The long jump run-up is shorter in blind athletes than in sighted athletes. We observed statistically significant differences for body centre of mass velocity and an increase in speed over the last three strides prior to take-off, contrasting with reports for sighted athletes and athletes with less severe visual impairment, who maintain or reduce their speed during the last stride. Stride length for the last three strides was the only spatial characteristic that was not significantly associated with effective jump distance. Blind long jumpers extend rather than shorten their last stride. Contact time with the take-off board is longer than that reported for sighted athletes. Conclusion The actions of blind long jumpers, unlike those without disabilities, do not vary their leg actions during the final runway approach for optimal placement on the take-off board. PMID:29018542

Three-dimensional kinematics of the pelvis and hind limbs in chimpanzee (Pan troglodytes) and human bipedal walking.

PubMed

O'Neill, Matthew C; Lee, Leng-Feng; Demes, Brigitte; Thompson, Nathan E; Larson, Susan G; Stern, Jack T; Umberger, Brian R

2015-09-01

The common chimpanzee (Pan troglodytes) is a facultative biped and our closest living relative. As such, the musculoskeletal anatomies of their pelvis and hind limbs have long provided a comparative context for studies of human and fossil hominin locomotion. Yet, how the chimpanzee pelvis and hind limb actually move during bipedal walking is still not well defined. Here, we describe the three-dimensional (3-D) kinematics of the pelvis, hip, knee and ankle during bipedal walking and compare those values to humans walking at the same dimensionless and dimensional velocities. The stride-to-stride and intraspecific variations in 3-D kinematics were calculated using the adjusted coefficient of multiple correlation. Our results indicate that humans walk with a more stable pelvis than chimpanzees, especially in tilt and rotation. Both species exhibit similar magnitudes of pelvis list, but with segment motion that is opposite in phasing. In the hind limb, chimpanzees walk with a more flexed and abducted limb posture, and substantially exceed humans in the magnitude of hip rotation during a stride. The average stride-to-stride variation in joint and segment motion was greater in chimpanzees than humans, while the intraspecific variation was similar on average. These results demonstrate substantial differences between human and chimpanzee bipedal walking, in both the sagittal and non-sagittal planes. These new 3-D kinematic data are fundamental to a comprehensive understanding of the mechanics, energetics and control of chimpanzee bipedalism. Copyright © 2015 Elsevier Ltd. All rights reserved.

Gait characteristics, balance performance and falls in ambulant adults with cerebral palsy: An observational study.

PubMed

Morgan, P; Murphy, A; Opheim, A; McGinley, J

2016-07-01

The relationship between spatiotemporal gait parameters, balance performance and falls history was investigated in ambulant adults with cerebral palsy (CP). Participants completed a single assessment of gait using an instrumented walkway at preferred and fast speeds, balance testing (Balance Evaluation Systems Test; BESTest), and reported falls history. Seventeen ambulatory adults with CP, mean age 37 years, participated. Gait speed was typically slow at both preferred and fast speeds (mean 0.97 and 1.21m/s, respectively), with short stride length and high cadence relative to speed. There was a significant, large positive relationship between preferred gait speed and BESTest total score (ρ=0.573; p<0.05) and fast gait speed and BESTest total score (ρ=0.647, p<0.01). The stride lengths of fallers at both preferred and fast speeds differed significantly from non-fallers (p=0.032 and p=0.025, respectively), with those with a prior history of falls taking shorter strides. Faster gait speed was associated with better performance on tests of anticipatory and postural response components of the BESTest, suggesting potential therapeutic training targets to address either gait speed or balance performance. Future exploration of the implications of slow walking speed and reduced stride length on falls and community engagement, and the potential prognostic value of stride length on identifying falls risk is recommended. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Relationships between body composition, body dimensions, and peak speed in cross-country sprint skiing.

PubMed

Stoggl, Thomas; Enqvist, Jonas; Muller, Erich; Holmberg, Hans-Christer

2010-01-01

In modern sprint cross-country skiing, strength and maximal speed are major determinants of performance. The aims of this study were to ascertain the anthropometric characteristics of world-class sprint skiers and to evaluate whether a specific body composition and/or body dimension characterizes a successful sprint skier. Our hypothesis was that body height and lean body mass are related to peak speed in double poling and diagonal stride. Fourteen male national and international elite skiers performed two peak speed tests in double poling and diagonal stride roller skiing on a treadmill and were analysed using dual-energy X-ray absorptiometry to determine body composition and body dimensions. Relative pole length was positively correlated with both techniques (double poling: r = 0.77, P < 0.01; diagonal stride: r = 0.60, P < 0.05) and was the only variable that was part of the multiple regression model for both double poling and diagonal stride peak speed. Body height was not correlated with any technique, whereas lean trunk mass (r = 0.75, P < 0.01), body mass index (r = 0.66, P < 0.01), total lean mass (r = 0.69, P < 0.01), and body mass (r = 0.57, P < 0.05) were positively related to double poling peak speed. Total lean mass (absolute: r = 0.58, P < 0.05; relative: r = 0.76, P < 0.001) and relative lean mass of the trunk, arms (both r = 0.72, P < 0.01), and legs (r = 0.54, P < 0.05) were positively related to diagonal stride peak speed. In conclusion, skiers should aim to achieve a body composition with a high percentage of lean mass and low fat mass. A focus on trunk mass through increased muscle mass appears to be important, especially for double poling. The use of longer poles (percent body height) seems to be advantageous for both double poling and diagonal stride peak speed, whereas body dimensions do not appear to be a predictive factor.

Impact of stride-coupled gaze shifts of walking blowflies on the neuronal representation of visual targets

PubMed Central

Kress, Daniel; Egelhaaf, Martin

2014-01-01

During locomotion animals rely heavily on visual cues gained from the environment to guide their behavior. Examples are basic behaviors like collision avoidance or the approach to a goal. The saccadic gaze strategy of flying flies, which separates translational from rotational phases of locomotion, has been suggested to facilitate the extraction of environmental information, because only image flow evoked by translational self-motion contains relevant distance information about the surrounding world. In contrast to the translational phases of flight during which gaze direction is kept largely constant, walking flies experience continuous rotational image flow that is coupled to their stride-cycle. The consequences of these self-produced image shifts for the extraction of environmental information are still unclear. To assess the impact of stride-coupled image shifts on visual information processing, we performed electrophysiological recordings from the HSE cell, a motion sensitive wide-field neuron in the blowfly visual system. This cell has been concluded to play a key role in mediating optomotor behavior, self-motion estimation and spatial information processing. We used visual stimuli that were based on the visual input experienced by walking blowflies while approaching a black vertical bar. The response of HSE to these stimuli was dominated by periodic membrane potential fluctuations evoked by stride-coupled image shifts. Nevertheless, during the approach the cell’s response contained information about the bar and its background. The response components evoked by the bar were larger than the responses to its background, especially during the last phase of the approach. However, as revealed by targeted modifications of the visual input during walking, the extraction of distance information on the basis of HSE responses is much impaired by stride-coupled retinal image shifts. Possible mechanisms that may cope with these stride-coupled responses are discussed. PMID:25309362

Effect of step-synchronized vibration stimulation of soles on gait in Parkinson's disease: a pilot study

PubMed Central

Novak, Peter; Novak, Vera

2006-01-01

Background Previous studies have suggested that impaired proprioceptive processing in the striatum may contribute to abnormal gait in Parkinson's disease (PD). Methods This pilot study assessed the effects of enhanced proprioceptive feedback using step-synchronized vibration stimulation of the soles (S-VS) on gait in PD. S-VS was used in 8 PD subjects (3 women and 5 men, age range 44–79 years, on medication) and 8 age-matched healthy subjects (5 women and 3 men). PD subjects had mild or moderate gait impairment associated with abnormal balance, but they did not have gait freezing. Three vibratory devices (VDs) were embedded in elastic insoles (one below the heel and two below the forefoot areas) inserted into the shoes. Each VD operates independently and has a pressure switch that activates the underlying vibratory actuator. The VD delivered the 70-Hz suprathreshold vibration pulse upon touch by the heel or forefoot, and the vibration pulse was deactivated upon respective push-offs. Six-minute hallway walking was studied with and without S-VS. Gait characteristics were measured using the force-sensitive foot switches. The primary outcome was the stride variability expressed as a coefficient of variation (CV), a measure of gait steadiness. Secondary outcome measures were walking distance and speed, stride length and duration, cadence, stance, swing and double support duration, and respective CVs (if applicable). Results The walking speed (p < 0.04) and the CV of the stride interval (p < 0.02) differed between the groups and S-VS conditions. In the PD group, S-VS decreased stride variability (p < 0.002), increased walking speed (p < 0.0001), stride duration (p < 0.01), stride length (p < 0.0002), and cadence (p < 0.03). In the control group, S-VS decreased stride variability (p < 0.006) and increased gait speed (p < 0.03), but other locomotion parameters were not significantly altered. Conclusion Augmented sensory feedback improves parkinsonian gait steadiness in the short-term setting. Because the suprathreshold stimulation prevented blinding of subjects, the learning effect and increased attention can be a confounding factor underlying results. Long-term studies are needed to establish the clinical value of the S-VS. PMID:16674823

Selective Breeding and Short-Term Access to a Running Wheel Alter Stride Characteristics in House Mice.

PubMed

Claghorn, Gerald C; Thompson, Zoe; Kay, Jarren C; Ordonez, Genesis; Hampton, Thomas G; Garland, Theodore

Postural and kinematic aspects of running may have evolved to support high runner (HR) mice to run approximately threefold farther than control mice. Mice from four replicate HR lines selectively bred for high levels of voluntary wheel running show many differences in locomotor behavior and morphology as compared with four nonselected control (C) lines. We hypothesized that HR mice would show stride alterations that have coadapted with locomotor behavior, morphology, and physiology. More specifically, we predicted that HR mice would have stride characteristics that differed from those of C mice in ways that parallel some of the adaptations seen in highly cursorial animals. For example, we predicted that limbs of HR mice would swing closer to the parasagittal plane, resulting in a two-dimensional measurement of narrowed stance width. We also expected that some differences between HR and C mice might be amplified by 6 d of wheel access, as is used to select breeders each generation. We used the DigiGait Imaging System (Mouse Specifics) to capture high-speed videos in ventral view as mice ran on a motorized treadmill across a range of speeds and then to automatically calculate several aspects of strides. Young adults of both sexes were tested both before and after 6 d of wheel access. Stride length, stride frequency, stance width, stance time, brake time, propel time, swing time, duty factor, and paw contact area were analyzed using a nested analysis of covariance, with body mass as a covariate. As expected, body mass and treadmill speed affected nearly every analyzed metric. Six days of wheel access also affected nearly every measure, indicating pervasive training effects, in both HR and C mice. As predicted, stance width was significantly narrower in HR than C mice. Paw contact area and duty factor were significantly greater in minimuscle individuals (subset of HR mice with 50%-reduced hind limb muscle mass) than in normal-muscled HR or C mice. We conclude that stride characteristics of house mice are adaptable in response to both selective breeding and changes in daily locomotor behavior (activity levels) that occur during as few as 6 d. These results have important implications for understanding the evolution and coadaptation of locomotor behavior and performance.

Association between stride time fractality and gait adaptability during unperturbed and asymmetric walking.

PubMed

Ducharme, Scott W; Liddy, Joshua J; Haddad, Jeffrey M; Busa, Michael A; Claxton, Laura J; van Emmerik, Richard E A

2018-04-01

Human locomotion is an inherently complex activity that requires the coordination and control of neurophysiological and biomechanical degrees of freedom across various spatiotemporal scales. Locomotor patterns must constantly be altered in the face of changing environmental or task demands, such as heterogeneous terrains or obstacles. Variability in stride times occurring at short time scales (e.g., 5-10 strides) is statistically correlated to larger fluctuations occurring over longer time scales (e.g., 50-100 strides). This relationship, known as fractal dynamics, is thought to represent the adaptive capacity of the locomotor system. However, this has not been tested empirically. Thus, the purpose of this study was to determine if stride time fractality during steady state walking associated with the ability of individuals to adapt their gait patterns when locomotor speed and symmetry are altered. Fifteen healthy adults walked on a split-belt treadmill at preferred speed, half of preferred speed, and with one leg at preferred speed and the other at half speed (2:1 ratio asymmetric walking). The asymmetric belt speed condition induced gait asymmetries that required adaptation of locomotor patterns. The slow speed manipulation was chosen in order to determine the impact of gait speed on stride time fractal dynamics. Detrended fluctuation analysis was used to quantify the correlation structure, i.e., fractality, of stride times. Cross-correlation analysis was used to measure the deviation from intended anti-phasing between legs as a measure of gait adaptation. Results revealed no association between unperturbed walking fractal dynamics and gait adaptability performance. However, there was a quadratic relationship between perturbed, asymmetric walking fractal dynamics and adaptive performance during split-belt walking, whereby individuals who exhibited fractal scaling exponents that deviated from 1/f performed the poorest. Compared to steady state preferred walking speed, fractal dynamics increased closer to 1/f when participants were exposed to asymmetric walking. These findings suggest there may not be a relationship between unperturbed preferred or slow speed walking fractal dynamics and gait adaptability. However, the emergent relationship between asymmetric walking fractal dynamics and limb phase adaptation may represent a functional reorganization of the locomotor system (i.e., improved interactivity between degrees of freedom within the system) to be better suited to attenuate externally generated perturbations at various spatiotemporal scales. Copyright © 2018 Elsevier B.V. All rights reserved.

Severe Cutaneous Adverse Reactions: The Pharmacogenomics from Research to Clinical Implementation

PubMed Central

Su, Shih-Chi; Hung, Shuen-Iu; Fan, Wen-Lang; Dao, Ro-Lan; Chung, Wen-Hung

2016-01-01

Severe cutaneous adverse reactions (SCARs), previously thought to be idiosyncratic or unpredictable, are a deadly form of adverse drug reactions with skin manifestations. Current pharmacogenomic studies of SCARs have made important strides, as the prevention of SCARs, to some extent, appears attainable with the identification of genetic variants for genes encoding drug-metabolizing enzymes and human leukocyte antigens (HLAs). Despite the improvement of incidence, a treatment guideline for this devastating condition is still unavailable, highlighting the inadequacy of contemporary accepted therapeutic interventions. As such, prompt withdrawal of causative drugs is believed to be a priority of patient management. In this review, we discuss recent cutting-edge findings concerning the discovery of biomarkers for SCARs and their clinical utilities in the better prediction and early diagnosis of this disease. The knowledge compiled herein provides clues for future investigations on deciphering additional genetic markers for SCARs and the design of clinical trials for the prospective identification of subjects at genetic risk for this condition, ultimately personalizing the medicine. PMID:27854302

Kick, Glide, Pole! Cross-Country Skiing Fun (Part II)

ERIC Educational Resources Information Center

Duoos, Bridget A.

2012-01-01

Part I of Kick, Glide, Pole! Cross-Country Skiing Fun, which was published in last issue, discussed how to select cross-country ski equipment, dress for the activity and the biomechanics of the diagonal stride. Part II focuses on teaching the diagonal stride technique and begins with a progression of indoor activities. Incorporating this fun,…

Effect of starting point formation on the crystallization of amorphous silicon films by flash lamp annealing

NASA Astrophysics Data System (ADS)

Sato, Daiki; Ohdaira, Keisuke

2018-04-01

We succeed in the crystallization of hydrogenated amorphous silicon (a-Si:H) films by flash lamp annealing (FLA) at a low fluence by intentionally creating starting points for the trigger of explosive crystallization (EC). We confirm that a partly thick a-Si part can induce the crystallization of a-Si films. A periodic wavy structure is observed on the surface of polycrystalline silicon (poly-Si) on and near the thick parts, which is a clear indication of the emergence of EC. Creating partly thick a-Si parts can thus be effective for the control of the starting point of crystallization by FLA and can realize the crystallization of a-Si with high reproducibility. We also compare the effects of creating thick parts at the center and along the edge of the substrates, and a thick part along the edge of the substrates leads to the initiation of crystallization at a lower fluence.

Process Development for Automated Solar Cell and Module Production. Task 4: Automated Array Assembly

NASA Technical Reports Server (NTRS)

1979-01-01

A baseline sequence for the manufacture of solar cell modules was specified. Starting with silicon wafers, the process goes through damage etching, texture etching, junction formation, plasma edge etch, aluminum back surface field formation, and screen printed metallization to produce finished solar cells. The cells were then series connected on a ribbon and bonded into a finished glass tedlar module. A number of steps required additional developmental effort to verify technical and economic feasibility. These steps include texture etching, plasma edge etch, aluminum back surface field formation, array layup and interconnect, and module edge sealing and framing.

Implementation of sobel method to detect the seed rubber plant leaves

NASA Astrophysics Data System (ADS)

Suyanto; Munte, J.

2018-03-01

This research was conducted to develop a system that can identify and recognize the type of rubber tree based on the pattern of leaves of the plant. The steps research are started with the identification of the image data acquisition, image processing, image edge detection and identification method template matching. Edge detection is using Sobel edge detection. Pattern recognition would detect image as input and compared with other images in a database called templates. Experiments carried out in one phase, identification of the leaf edge, using a rubber plant leaf image 14 are superior and 5 for each type of test images (clones) of the plant. From the experimental results obtained by the recognition rate of 91.79%.

Shedding light on walking in the dark: the effects of reduced lighting on the gait of older adults with a higher-level gait disorder and controls.

PubMed

Kesler, Anat; Leibovich, Gregory; Herman, Talia; Gruendlinger, Leor; Giladi, Nir; Hausdorff, Jeffrey M

2005-08-28

To study the effects of reduced lighting on the gait of older adults with a high level gait disorder (HLGD) and to compare their response to that of healthy elderly controls. 22 patients with a HLGD and 20 age-matched healthy controls were studied under usual lighting conditions (1000 lumens) and in near darkness (5 lumens). Gait speed and gait dynamics were measured under both conditions. Cognitive function, co-morbidities, depressive symptoms, and vision were also evaluated. Under usual lighting conditions, patients walked more slowly, with reduced swing times, and increased stride-to-stride variability, compared to controls. When walking under near darkness conditions, both groups slowed their gait. All other measures of gait were not affected by lighting in the controls. In contrast, patients further reduced their swing times and increased their stride-to-stride variability, both stride time variability and swing time variability. The unique response of the patients was not explained by vision, mental status, co-morbidities, or the values of walking under usual lighting conditions. Walking with reduced lighting does not affect the gait of healthy elderly subjects, except for a reduction in speed. On the other hand, the gait of older adults with a HLGD becomes more variable and unsteady when they walk in near darkness, despite adapting a slow and cautious gait. Further work is needed to identify the causes of the maladaptive response among patients with a HLGD and the potential connection between this behavior and the increased fall risk observed in these patients.

Overcoming the limitations of the Harmonic Ratio for the reliable assessment of gait symmetry.

PubMed

Pasciuto, Ilaria; Bergamini, Elena; Iosa, Marco; Vannozzi, Giuseppe; Cappozzo, Aurelio

2017-02-28

The Harmonic Ratio (HR) is an index based on the spectral analysis of lower trunk accelerations that is commonly used to assess the quality of gait. However, it presents several issues concerning reliability and interpretability. As a consequence, the literature provides very different values albeit corresponding to the same populations. In the present work, an improved harmonic ratio (iHR) was defined, relating the power of the intrinsic harmonics (i.e. associated with the symmetric component of gait) to the total power of the signal for each stride, leading to a normalised index ranging from 0 to 100%. The effect of the considered number of harmonics and strides on the estimate of both HR and iHR was assessed. The gait of three groups of volunteers was investigated: young healthy adults, elderly women and male trans-femoral amputees. Both HR and iHR were able to discriminate gait deviations from the gait of young healthy adults. Moreover, iHR proved to be more robust with respect to the number of considered harmonics and strides, and to exhibit a lower inter-stride variability. Additionally, using a normalised index as iHR led to a more straightforward interpretation and improved comparability. The importance of standardised conditions for the index evaluation was unveiled, and, in order to enhance the future comparability of the index, the following guidelines were presented: considering at least 20 harmonics and 20 strides; expressing the acceleration components in a repeatable, anatomical, local system of reference; and evaluating the iHR index, rather than the traditional HR. Copyright © 2017 Elsevier Ltd. All rights reserved.

Parkinson's disease (PD) with dementia and falls is improved by AChEI? A preliminary study report.

PubMed

Lauretani, Fulvio; Galuppo, Laura; Costantino, Cosimo; Ticinesi, Andrea; Ceda, Gianpaolo; Ruffini, Livio; Nardelli, Anna; Maggio, Marcello

2016-06-01

Advanced PD is often associated with cognitive impairment and frequent falls. We describe a suggestive case report of PD associated with mild cognitive impairment (MCI) and falls. The aim of our study was to test alteration in balance potentially related to use of acetylcholinesterase inhibitor (AchEI). We address this hypothesis after keeping the patient in stable dosage of dopamine agonist. We describe an initial pharmacological management in a 78-year-old man affected by Parkinson disease (PD) associated with mild cognitive impairment (MCI) and history of falls. The diagnosis of PD was also confirmed by SPECT with DATSCAN, after CT-brain exclusion of potential other causes of the symptoms. Cognitive and motor performances of the patient were initially evaluated by Mini Mental Examination State Examination (MMSE), Short Physical Performance Battery (SPPB) and Romberg test. We also recorded gait parameters using an accelerometer, while balance and stability were assessed by stabilometric platform with open and closed eyes. We repeated cognitive and motor tests and gait and balance evaluation after stable dosage of dopamine agonist before and after introduction of AchEI. After starting dopamine agonist therapy, there was a significant improvement in gait parameters (speed, stride/min, stride length, swing duration, and decrease in gait cycle duration and rolling duration). When stable dosage of dopamine agonist was reached, AchEI was introduced obtaining not only a significant improvement of cognitive performance, but also a significant positive change in balance. We hypothesize that AchEI could improve stability, balance and postural instability in addition to cognitive performance in PD with MCI and balance deficits.

Metabolic Cost of Stride Rate, Resistance, and Combined Use of Arms and Legs on the Elliptical Trainer

ERIC Educational Resources Information Center

Mier, Constance M.; Feito, Yuri

2006-01-01

We measured the effects of stride rate, resistance, and combined arm-leg use on energy expenditure during elliptical trainer exercise and assessed the accuracy of the manufacturer's energy expenditure calculations. Twenty-six men and women (M age = 29 years, SD = 8; M body weight = 73.0 kg, SD = 15.2) participated. Twenty-two participants…

Evaluation of the microsoft kinect skeletal versus depth data analysis for timed-up and go and figure of 8 walk tests.

PubMed

Hotrabhavananda, Benjamin; Mishra, Anup K; Skubic, Marjorie; Hotrabhavananda, Nijaporn; Abbott, Carmen

2016-08-01

We compared the performance of the Kinect skeletal data with the Kinect depth data in capturing different gait parameters during the Timed-up and Go Test (TUG) and Figure of 8 Walk Test (F8W). The gait parameters considered were stride length, stride time, and walking speed for the TUG, and number of steps and completion time for the F8W. A marker-based Vicon motion capture system was used for the ground-truth measurements. Five healthy participants were recruited for the experiment and were asked to perform three trials of each task. Results show that depth data analysis yields stride length and stride time measures with significantly low percentile errors as compared to the skeletal data analysis. However, the skeletal and depth data performed similar with less than 3% of absolute mean percentile error in determining the walking speed for the TUG and both parameters of F8W. The results show potential capabilities of Kinect depth data analysis in computing many gait parameters, whereas, the Kinect skeletal data can also be used for walking speed in TUG and F8W gait parameters.

The behavioral assessment and alleviation of pain associated with castration in beef calves treated with flunixin meglumine and caudal lidocaine epidural anesthesia with epinephrine

PubMed Central

Currah, Jan M.; Hendrick, Steven H.; Stookey, Joseph M.

2009-01-01

The objectives of this study were 1) to determine the effects of flunixin megulmine in combination with caudal epidural anesthesia as a postoperative analgesic in beef calves following surgical castration, and 2) to consider stride length and pedometry as potential behavioral assessment tools for detecting postcastration pain. Surgical castration was performed in 101 beef calves randomly assigned to 3 treatment subgroups: 1) castration without anesthesia (SURG); 2) castration following lidocaine with epinephrine caudal epidural anesthesia (SURG + EPI); 3) castration following lidocaine with epinephrine caudal epidural anesthesia and flunixin meglumine (SURG + EPI + F). Several outcomes, including pedometer counts, changes in stride length, subjective visual assessment of pain, instantaneous scan sampling of the calves’ postoperative activities, and the amount of movement and vocalization during the castration procedure, were measured to identify and quantify pain. The results indicated that stride length and the number of steps taken by calves after castration appear to be good measures of pain. Significant differences found between treatment groups for stride length and visual assessments suggest that flunixin meglumine can be considered to provide visible pain relief up to 8 hours postcastration. PMID:19436444

The behavioral assessment and alleviation of pain associated with castration in beef calves treated with flunixin meglumine and caudal lidocaine epidural anesthesia with epinephrine.

PubMed

Currah, Jan M; Hendrick, Steven H; Stookey, Joseph M

2009-04-01

The objectives of this study were 1) to determine the effects of flunixin megulmine in combination with caudal epidural anesthesia as a postoperative analgesic in beef calves following surgical castration, and 2) to consider stride length and pedometry as potential behavioral assessment tools for detecting postcastration pain. Surgical castration was performed in 101 beef calves randomly assigned to 3 treatment subgroups: 1) castration without anesthesia (SURG); 2) castration following lidocaine with epinephrine caudal epidural anesthesia (SURG + EPI); 3) castration following lidocaine with epinephrine caudal epidural anesthesia and flunixin meglumine (SURG + EPI + F). Several outcomes, including pedometer counts, changes in stride length, subjective visual assessment of pain, instantaneous scan sampling of the calves' postoperative activities, and the amount of movement and vocalization during the castration procedure, were measured to identify and quantify pain. The results indicated that stride length and the number of steps taken by calves after castration appear to be good measures of pain. Significant differences found between treatment groups for stride length and visual assessments suggest that flunixin meglumine can be considered to provide visible pain relief up to 8 hours postcastration.

Gait variability in community dwelling adults with Alzheimer disease.

PubMed

Webster, Kate E; Merory, John R; Wittwer, Joanne E

2006-01-01

Studies have shown that measures of gait variability are associated with falling in older adults. However, few studies have measured gait variability in people with Alzheimer disease, despite the high incidence of falls in Alzheimer disease. The purpose of this study was to compare gait variability of community-dwelling older adults with Alzheimer disease and control subjects at various walking speeds. Ten subjects with mild-moderate Alzheimer disease and ten matched control subjects underwent gait analysis using an electronic walkway. Participants were required to walk at self-selected slow, preferred, and fast speeds. Stride length and step width variability were determined using the coefficient of variation. Results showed that stride length variability was significantly greater in the Alzheimer disease group compared with the control group at all speeds. In both groups, increases in walking speed were significantly correlated with decreases in stride length variability. Step width variability was significantly reduced in the Alzheimer disease group compared with the control group at slow speed only. In conclusion, there is an increase in stride length variability in Alzheimer disease at all walking speeds that may contribute to the increased incidence of falls in Alzheimer disease.

China's postgraduate education practices and its academic impact on publishing: is it proportional?

PubMed

Zhu, Yuan; Zhang, Chun-jie; Hu, Cheng-liang

2014-12-01

Though postgraduate education started before the founding of new China in 1949, it was not until the implementation of the policy reform and the opening-up in 1978 that China's postgraduate productivity began to take off. Since the introduction of Regulations of the People's Republic of China on Academic Degrees in 1981, the number of graduate students enrolled each year has increased 50 times since 1978. China is now the second largest producer of publications indexed by the database of Science Citation Index (SCI) (Web of Science™, Thomson Reuters), which reflects great strides being made in the postgraduate education. In this paper, we discuss the relationship between the increasingly high enrollments of graduate students and the quantity (the number) and quality (the academic impact and the originality) of their publications, to see whether there is a correlation.

X-Ray Optics: Past, Present, and Future

NASA Technical Reports Server (NTRS)

Zhang, William W.

2010-01-01

X-ray astronomy started with a small collimated proportional counter atop a rocket in the early 1960s. It was immediately recognized that focusing X-ray optics would drastically improve both source location accuracy and source detection sensitivity. In the past 5 decades, X-ray astronomy has made significant strides in achieving better angular resolution, large photon collection area, and better spectral and timing resolutions, culminating in the three currently operating X-ray observatories: Chandra, XMM/Newton, and Suzaku. In this talk I will give a brief history of X-ray optics, concentrating on the characteristics of the optics of these three observatories. Then I will discuss current X-ray mirror technologies being developed in several institutions. I will end with a discussion of the optics for the International X-ray Observatory that I have been developing at Goddard Space Flight Center.

Mechanical energy storage device for hip disarticulation

NASA Technical Reports Server (NTRS)

Vallotton, W. C. (Inventor)

1977-01-01

An artificial leg including a trunk socket, a thigh section hingedly coupled to the trunk socket, a leg section hingedly coupled to the thigh section and a foot section hingedly coupled to the leg section is outlined. A mechanical energy storage device is operatively associated with the artificial leg for storage and release of energy during the normal walking stride of the user. Energy is stored in the mechanical energy storage device during a weight-bearing phase of the walking stride when the user's weight is on the artificial leg. Energy is released during a phase of the normal walking stride, when the user's weight is removed from the artificial leg. The stored energy is released from the energy storage device to pivot the thigh section forwardly about the hinged coupling to the trunk socket.

Kinematic constraints associated with the acquisition of overarm throwing part I: step and trunk actions.

PubMed

Stodden, David F; Langendorfer, Stephen J; Fleisig, Glenn S; Andrews, James R

2006-12-01

The purposes of this study were to: (a) examine differences within specific kinematic variables and ball velocity associated with developmental component levels of step and trunk action (Roberton & Halverson, 1984), and (b) if the differences in kinematic variables were significantly associated with the differences in component levels, determine potential kinematic constraints associated with skilled throwing acquisition. Results indicated stride length (69.3 %) and time from stride foot contact to ball release (39. 7%) provided substantial contributions to ball velocity (p < .001). All trunk kinematic measures increased significantly with increasing component levels (p < .001). Results suggest that trunk linear and rotational velocities, degree of trunk tilt, time from stride foot contact to ball release, and ball velocity represented potential control parameters and, therefore, constraints on overarm throwing acquisition.

Evaluating the approach run of class F11 visually impaired athletes in triple and long jumps.

PubMed

Theodorou, Apostolos; Skordilis, Emmanouil

2012-04-01

The present study examined stride pattern characteristics of Class F11 visually impaired long jumpers and triple jumpers. Athletes demonstrated initial ascending footfall variability followed by descending variability, on the second (long jumpers) and third (triple jumpers) stride prior to take-off, at a mean distance of 6.26 m (long jumpers) and 7.36 m (triple jumpers) from the take-off board. Toe-board-distance variability reached a maximum value of 0.36 m and 0.38 m for the long and triple jump, respectively. Last stride toe-board-distance variability was 0.29 m (long jump) and 0.25 m (triple jump). Class F11 visually impaired athletes exhibit regulation of goal-directed gait analogous to that of non-visually impaired athletes.

Contour Tracking with a Spatio-Temporal Intensity Moment.

PubMed

Demi, Marcello

2016-06-01

Standard edge detection operators such as the Laplacian of Gaussian and the gradient of Gaussian can be used to track contours in image sequences. When using edge operators, a contour, which is determined on a frame of the sequence, is simply used as a starting contour to locate the nearest contour on the subsequent frame. However, the strategy used to look for the nearest edge points may not work when tracking contours of non isolated gray level discontinuities. In these cases, strategies derived from the optical flow equation, which look for similar gray level distributions, appear to be more appropriate since these can work with a lower frame rate than that needed for strategies based on pure edge detection operators. However, an optical flow strategy tends to propagate the localization errors through the sequence and an additional edge detection procedure is essential to compensate for such a drawback. In this paper a spatio-temporal intensity moment is proposed which integrates the two basic functions of edge detection and tracking.

Generation algorithm of craniofacial structure contour in cephalometric images

NASA Astrophysics Data System (ADS)

Mondal, Tanmoy; Jain, Ashish; Sardana, H. K.

2010-02-01

Anatomical structure tracing on cephalograms is a significant way to obtain cephalometric analysis. Computerized cephalometric analysis involves both manual and automatic approaches. The manual approach is limited in accuracy and repeatability. In this paper we have attempted to develop and test a novel method for automatic localization of craniofacial structure based on the detected edges on the region of interest. According to the grey scale feature at the different region of the cephalometric images, an algorithm for obtaining tissue contour is put forward. Using edge detection with specific threshold an improved bidirectional contour tracing approach is proposed by an interactive selection of the starting edge pixels, the tracking process searches repetitively for an edge pixel at the neighborhood of previously searched edge pixel to segment images, and then craniofacial structures are obtained. The effectiveness of the algorithm is demonstrated by the preliminary experimental results obtained with the proposed method.

Synthetic biology in the UK - An outline of plans and progress.

PubMed

Clarke, L J; Kitney, R I

2016-12-01

Synthetic biology is capable of delivering new solutions to key challenges spanning the bioeconomy, both nationally and internationally. Recognising this significant potential and the associated need to facilitate its translation and commercialisation the UK government commissioned the production of a national Synthetic Biology Roadmap in 2011, and subsequently provided crucial support to assist its implementation. Critical infrastructural investments have been made, and important strides made towards the development of an effectively connected community of practitioners and interest groups. A number of Synthetic Biology Research Centres, DNA Synthesis Foundries, a Centre for Doctoral Training, and an Innovation Knowledge Centre have been established, creating a nationally distributed and integrated network of complementary facilities and expertise. The UK Synthetic Biology Leadership Council published a UK Synthetic Biology Strategic Plan in 2016, increasing focus on the processes of translation and commercialisation. Over 50 start-ups, SMEs and larger companies are actively engaged in synthetic biology in the UK, and inward investments are starting to flow. Together these initiatives provide an important foundation for stimulating innovation, actively contributing to international research and development partnerships, and helping deliver useful benefits from synthetic biology in response to local and global needs and challenges.

Extraction of edge-based and region-based features for object recognition

NASA Astrophysics Data System (ADS)

Coutts, Benjamin; Ravi, Srinivas; Hu, Gongzhu; Shrikhande, Neelima

1993-08-01

One of the central problems of computer vision is object recognition. A catalogue of model objects is described as a set of features such as edges and surfaces. The same features are extracted from the scene and matched against the models for object recognition. Edges and surfaces extracted from the scenes are often noisy and imperfect. In this paper algorithms are described for improving low level edge and surface features. Existing edge extraction algorithms are applied to the intensity image to obtain edge features. Initial edges are traced by following directions of the current contour. These are improved by using corresponding depth and intensity information for decision making at branch points. Surface fitting routines are applied to the range image to obtain planar surface patches. An algorithm of region growing is developed that starts with a coarse segmentation and uses quadric surface fitting to iteratively merge adjacent regions into quadric surfaces based on approximate orthogonal distance regression. Surface information obtained is returned to the edge extraction routine to detect and remove fake edges. This process repeats until no more merging or edge improvement can take place. Both synthetic (with Gaussian noise) and real images containing multiple object scenes have been tested using the merging criteria. Results appeared quite encouraging.

Fourier-based integration of quasi-periodic gait accelerations for drift-free displacement estimation using inertial sensors.

PubMed

Sabatini, Angelo Maria; Ligorio, Gabriele; Mannini, Andrea

2015-11-23

In biomechanical studies Optical Motion Capture Systems (OMCS) are considered the gold standard for determining the orientation and the position (pose) of an object in a global reference frame. However, the use of OMCS can be difficult, which has prompted research on alternative sensing technologies, such as body-worn inertial sensors. We developed a drift-free method to estimate the three-dimensional (3D) displacement of a body part during cyclical motions using body-worn inertial sensors. We performed the Fourier analysis of the stride-by-stride estimates of the linear acceleration, which were obtained by transposing the specific forces measured by the tri-axial accelerometer into the global frame using a quaternion-based orientation estimation algorithm and detecting when each stride began using a gait-segmentation algorithm. The time integration was performed analytically using the Fourier series coefficients; the inverse Fourier series was then taken for reconstructing the displacement over each single stride. The displacement traces were concatenated and spline-interpolated to obtain the entire trace. The method was applied to estimate the motion of the lower trunk of healthy subjects that walked on a treadmill and it was validated using OMCS reference 3D displacement data; different approaches were tested for transposing the measured specific force into the global frame, segmenting the gait and performing time integration (numerically and analytically). The width of the limits of agreements were computed between each tested method and the OMCS reference method for each anatomical direction: Medio-Lateral (ML), VerTical (VT) and Antero-Posterior (AP); using the proposed method, it was observed that the vertical component of displacement (VT) was within ±4 mm (±1.96 standard deviation) of OMCS data and each component of horizontal displacement (ML and AP) was within ±9 mm of OMCS data. Fourier harmonic analysis was applied to model stride-by-stride linear accelerations during walking and to perform their analytical integration. Our results showed that analytical integration based on Fourier series coefficients was a useful approach to accurately estimate 3D displacement from noisy acceleration data.

Softer, higher-friction flooring improves gait of cows with and without sole ulcers.

PubMed

Flower, F C; de Passillé, A M; Weary, D M; Sanderson, D J; Rushen, J

2007-03-01

We studied dairy cows (n = 30) walking on concrete and on a soft, high-friction composite rubber surface to examine how flooring influenced gait and how this differed for cows with hoof lesions. Cows had hooves trimmed 9 wk after the trial and were classified as either with or without sole ulcers. Video recordings of the cows while walking were digitized using motion analysis software to calculate stride variables (length, height, overlap, duration, proportion of triple support, and speed). Gait was scored by a subjective scoring system (1 = sound to 5 = severely lame) and by a continuous visual analog scale for each of 7 gait attributes. Cows with sole ulcers walking on a composite rubber surface had longer strides (156.9 +/- 2.6 vs. 149.6 +/- 2.6 cm), higher stride heights (9.7 +/- 0.3 vs. 8.8 +/- 0.3 cm), more stride overlap (0.4 +/- 2.0 vs. -4.3 +/- 2.0 cm), shorter periods of triple support (3 legs in ground contact; 68.6 +/- 2.0 vs. 73.8 +/- 2.0%), walked faster (1.22 +/- 0.04 vs. 1.17 +/- 0.04 m/s) and had lower overall gait scores (2.9 +/- 0.1 vs. 3.1 +/- 0.1), better tracking-up (19 +/- 2 vs. 24 +/- 2), better joint flexion (29 +/- 2 vs. 33 +/- 2), more symmetric steps (31 +/- 3 vs. 36 +/- 3), and less reluctance to bear weight on their legs (12 +/- 2 vs. 16 +/- 2) compared with walking on concrete. Similar results were found for cows without sole ulcers. Most of the subjective gait measures could distinguish between cows with and without sole ulcers, but this was not the case for kinematic measures other than stride height. Cows with higher gait scores (more severe lameness) showed the greatest improvement in stride length (r = -0.51), triple support (r = 0.59), swing duration (r = -0.44), overall gait score (r = 0.46), and reluctance to bear weight (r = 0.66) when walking on the rubber surface compared with cows with lower gait scores. These results indicate that rubber flooring provides a more secure footing and is more comfortable to walk on, especially for lame cattle.

Gait-cycle characteristics and running economy in elite Eritrean and European runners.

PubMed

Santos-Concejero, Jordan; Oliván, Jesús; Maté-Muñoz, José L; Muniesa, Carlos; Montil, Marta; Tucker, Ross; Lucia, Alejandro

2015-04-01

This study aimed to determine whether biomechanical characteristics such as ground-contact time, swing time, and stride length and frequency contribute to the exceptional running economy of East African runners. Seventeen elite long-distance runners (9 Eritrean, 8 European) performed an incremental maximal running test and 3 submaximal running bouts at 17, 19, and 21 km/h. During the tests, gas-exchange parameters were measured to determine maximal oxygen uptake (VO2max) and running economy (RE). In addition, ground-contact time, swing time, stride length, and stride frequency were measured. The European runners had higher VO2max values than the Eritrean runners (77.2 ± 5.2 vs 73.5 ± 6.0 mL · kg-1 · min-1, P = .011, effect sizes [ES] = 0.65), although Eritrean runners were more economical at 19 km/h (191.4 ± 10.4 vs 205.9 ± 13.3 mL · kg-1 · min-1, P = .026, ES = 1.21). There were no differences between groups for ground-contact time, swing time, stride length, or stride frequency at any speed. Swing time was associated with running economy at 21 km/h in the Eritrean runners (r = .71, P = .033), but no other significant association was found between RE and biomechanical variables. Finally, best 10-km performance was significantly correlated with RE (r = -.57; P = .013). Eritrean runners have superior RE compared with elite European runners. This appears to offset their inferior VO2max. However, the current data suggest that their better RE does not have a biomechanical basis. Other factors, not measured in the current study, may contribute to this RE advantage.

Partial body weight support treadmill training speed influences paretic and non-paretic leg muscle activation, stride characteristics, and ratings of perceived exertion during acute stroke rehabilitation.

PubMed

Burnfield, Judith M; Buster, Thad W; Goldman, Amy J; Corbridge, Laura M; Harper-Hanigan, Kellee

2016-06-01

Intensive task-specific training is promoted as one approach for facilitating neural plastic brain changes and associated motor behavior gains following neurologic injury. Partial body weight support treadmill training (PBWSTT), is one task-specific approach frequently used to improve walking during the acute period of stroke recovery (<1month post infarct). However, only limited data have been published regarding the relationship between training parameters and physiologic demands during this early recovery phase. To examine the impact of four walking speeds on stride characteristics, lower extremity muscle demands (both paretic and non-paretic), Borg ratings of perceived exertion (RPE), and blood pressure. A prospective, repeated measures design was used. Ten inpatients post unilateral stroke participated. Following three familiarization sessions, participants engaged in PBWSTT at four predetermined speeds (0.5, 1.0, 1.5 and 2.0mph) while bilateral electromyographic and stride characteristic data were recorded. RPE was evaluated immediately following each trial. Stride length, cadence, and paretic single limb support increased with faster walking speeds (p⩽0.001), while non-paretic single limb support remained nearly constant. Faster walking resulted in greater peak and mean muscle activation in the paretic medial hamstrings, vastus lateralis and medial gastrocnemius, and non-paretic medial gastrocnemius (p⩽0.001). RPE also was greatest at the fastest compared to two slowest speeds (p<0.05). During the acute phase of stroke recovery, PBWSTT at the fastest speed (2.0mph) promoted practice of a more optimal gait pattern with greater intensity of effort as evidenced by the longer stride length, increased between-limb symmetry, greater muscle activation, and higher RPE compared to training at the slowest speeds. Copyright © 2016 Elsevier B.V. All rights reserved.

Disturbances of automatic gait control mechanisms in higher level gait disorder.

PubMed

Danoudis, Mary; Ganesvaran, Ganga; Iansek, Robert

2016-07-01

The underlying mechanisms responsible for the gait changes in frontal gait disorder (FGD), a form of higher level gait disorders, are poorly understood. We investigated the relationship between stride length and cadence (SLCrel) in people with FGD (n=15) in comparison to healthy older adults (n=21) to improve our understanding of the changes to gait in FGD. Gait data was captured using an electronic walkway system as participants walked at five self-selected speed conditions: preferred, very slow, slow, fast and very fast. Linear regression was used to determine the strength of the relationship (R(2)), slope and intercept. In the FGD group 9 participants had a strong SLCrel (linear group) (R(2)>0.8) and 6 a weak relationship (R(2)<0.8) (nonlinear group). The linear FGD group did not differ to healthy control for slope (p>0.05) but did have a lower intercept (p<0.001). The linear FGD group modulated gait speed by adjusting stride length and cadence similar to controls whereas the nonlinear FGD participants adjusted stride length but not cadence similar to controls. The non-linear FGD group had greater disturbance to their gait, poorer postural control and greater fear of falling compared to the linear FGD group. Investigation of the SLCrel resulted in new insights into the underlying mechanisms responsible for the gait changes found in FGD. The findings suggest stride length regulation was disrupted in milder FGD but as the disorder worsened, cadence control also became disordered resulting in a break down in the relationship between stride length and cadence. Copyright © 2016 Elsevier B.V. All rights reserved.

Cumulative loads increase at the knee joint with slow-speed running compared to faster running: a biomechanical study.

PubMed

Petersen, Jesper; Sørensen, Henrik; Nielsen, Rasmus Østergaard

2015-04-01

Biomechanical cross-sectional study. To investigate the hypothesis that the cumulative load at the knee during running increases as running speed decreases. The knee joint load per stride decreases as running speed decreases. However, by decreasing running speed, the number of strides per given distance is increased. Running a given distance at a slower speed may increase the cumulative load at the knee joint compared with running the same distance at a higher speed, hence increasing the risk of running-related injuries in the knee. Kinematic and ground reaction force data were collected from 16 recreational runners, during steady-state running with a rearfoot strike pattern at 3 different speeds (mean ± SD): 8.02 ± 0.17 km/h, 11.79 ± 0.21 km/h, and 15.78 ± 0.22 km/h. The cumulative load (cumulative impulse) over a 1000-m distance was calculated at the knee joint on the basis of a standard 3-D inverse-dynamics approach. Based on a 1000-m running distance, the cumulative load at the knee was significantly higher at a slow running speed than at a high running speed (relative difference, 80%). The mean load per stride at the knee increased significantly across all biomechanical parameters, except impulse, following an increase in running speed. Slow-speed running decreases knee joint loads per stride and increases the cumulative load at the knee joint for a given running distance compared to faster running. The primary reason for the increase in cumulative load at slower speeds is an increase in number of strides needed to cover the same distance.

Validation of a commercial inertial sensor system for spatiotemporal gait measurements in children.

PubMed

Lanovaz, Joel L; Oates, Alison R; Treen, Tanner T; Unger, Janelle; Musselman, Kristin E

2017-01-01

Although inertial sensor systems are becoming a popular tool for gait analysis in both healthy and pathological adult populations, there are currently no data on the validity of these systems for use with children. The purpose of this study was to validate spatiotemporal data from a commercial inertial sensor system (MobilityLab) in typically-developing children. Data from 10 children (5 males; 3.0-8.3 years, mean=5.1) were collected simultaneously from MobilityLab and 3D motion capture during gait at self-selected and fast walking speeds. Spatiotemporal parameters were compared between the two methods using a Bland-Altman method. The results indicate that, while the temporal gait measurements were similar between the two systems, MobilityLab demonstrated a consistent bias with respect to measurement of the spatial data (stride length). This error is likely due to differences in relative leg length and gait characteristics in children compared to the MobilityLab adult reference population used to develop the stride length algorithm. A regression-based equation was developed based on the current data to correct the MobilityLab stride length output. The correction was based on leg length, stride time, and shank range-of-motion, each of which were independently associated with stride length. Once the correction was applied, all of the spatiotemporal parameters evaluated showed good agreement. The results of this study indicate that MobilityLab is a valid tool for gait analysis in typically-developing children. Further research is needed to determine the efficacy of this system for use in children suffering from pathologies that impact gait mechanics. Copyright © 2016 Elsevier B.V. All rights reserved.

Gait parameter risk factors for falls under simple and dual task conditions in cognitively impaired older people.

PubMed

Taylor, Morag E; Delbaere, Kim; Mikolaizak, A Stefanie; Lord, Stephen R; Close, Jacqueline C T

2013-01-01

Impaired gait may contribute to the increased rate of falls in cognitively impaired older people. We investigated whether gait under simple and dual task conditions could predict falls in this group. The study sample consisted of 64 community dwelling older people with mild to moderate cognitive impairment. Participants walked at their preferred speed under three conditions: (a) simple walking, (b) walking while carrying a glass of water and (c) walking while counting backwards from 30. Spatiotemporal gait parameters were measured using the GAITRite(®) mat. Falls were recorded prospectively for 12months with the assistance of carers. Twenty-two (35%) people fell two or more times in the 12month follow-up period. There was a significant main effect of gait condition and a significant main effect of faller status for mean value measures (velocity, stride length, double support time and stride width) and for variability measures (swing time variability and stride length variability). Examination of individual gait parameters indicated that the multiple fallers walked more slowly, had shorter stride length, spent longer time in double support, had a wider support width and showed more variability in stride length and swing time (p<0.05). There was no significant interaction between gait condition and faller status for any of the gait variables. In conclusion, dual task activities adversely affect gait in cognitively impaired older people. Multiple fallers performed worse in each gait condition but the addition of a functional or cognitive secondary task provided no added benefit in discriminating fallers from non-fallers with cognitive impairment. Copyright © 2012 Elsevier B.V. All rights reserved.

Variability of segment coordination using a vector coding technique: Reliability analysis for treadmill walking and running.

PubMed

Hafer, Jocelyn F; Boyer, Katherine A

2017-01-01

Coordination variability (CV) quantifies the variety of movement patterns an individual uses during a task and may provide a measure of the flexibility of that individual's motor system. While there is growing popularity of segment CV as a marker of motor system health or adaptability, it is not known how many strides of data are needed to reliably calculate CV. This study aimed to determine the number of strides needed to reliably calculate CV in treadmill walking and running, and to compare CV between walking and running in a healthy population. Ten healthy young adults walked and ran at preferred speeds on a treadmill and a modified vector coding technique was used to calculate CV for the following segment couples: pelvis frontal plane vs. thigh frontal plane, thigh sagittal plane vs. shank sagittal plane, thigh sagittal plane vs. shank transverse plane, and shank transverse plane vs. rearfoot frontal plane. CV for each coupling of interest was calculated for 2-15 strides for each participant and gait type. Mean CV was calculated across the entire gait cycle and, separately, for 4 phases of the gait cycle. For running and walking 8 and 10 strides, respectively, were sufficient to obtain a reliable CV estimate. CV was significantly different between walking and running for the thigh vs. shank couple comparisons. These results suggest that 10 strides of treadmill data are needed to reliably calculate CV for walking and running. Additionally, the differences in CV between walking and running suggest that the role of knee (i.e., inter-thigh- shank) control may differ between these forms of locomotion. Copyright © 2016 Elsevier B.V. All rights reserved.

Delaunay based algorithm for finding polygonal voids in planar point sets

NASA Astrophysics Data System (ADS)

Alonso, R.; Ojeda, J.; Hitschfeld, N.; Hervías, C.; Campusano, L. E.

2018-01-01

This paper presents a new algorithm to find under-dense regions called voids inside a 2D point set. The algorithm starts from terminal-edges (local longest-edges) in a Delaunay triangulation and builds the largest possible low density terminal-edge regions around them. A terminal-edge region can represent either an entire void or part of a void (subvoid). Using artificial data sets, the case of voids that are detected as several adjacent subvoids is analyzed and four subvoid joining criteria are proposed and evaluated. Since this work is inspired on searches of a more robust, effective and efficient algorithm to find 3D cosmological voids the evaluation of the joining criteria considers this context. However, the design of the algorithm permits its adaption to the requirements of any similar application.

An exploratory clustering approach for extracting stride parameters from tracking collars on free-ranging wild animals.

PubMed

Dewhirst, Oliver P; Roskilly, Kyle; Hubel, Tatjana Y; Jordan, Neil R; Golabek, Krystyna A; McNutt, J Weldon; Wilson, Alan M

2017-02-01

Changes in stride frequency and length with speed are key parameters in animal locomotion research. They are commonly measured in a laboratory on a treadmill or by filming trained captive animals. Here, we show that a clustering approach can be used to extract these variables from data collected by a tracking collar containing a GPS module and tri-axis accelerometers and gyroscopes. The method enables stride parameters to be measured during free-ranging locomotion in natural habitats. As it does not require labelled data, it is particularly suitable for use with difficult to observe animals. The method was tested on large data sets collected from collars on free-ranging lions and African wild dogs and validated using a domestic dog. © 2017. Published by The Company of Biologists Ltd.

Hip adductor muscle function in forward skating.

PubMed

Chang, Ryan; Turcotte, Rene; Pearsall, David

2009-09-01

Adductor strain injuries are prevalent in ice hockey. It has long been speculated that adductor muscular strains may be caused by repeated eccentric contractions which decelerate the leg during a stride. The purpose of this study was to investigate the relationship of skating speed with muscle activity and lower limb kinematics, with a particular focus on the role of the hip adductors. Seven collegiate ice hockey players consented to participate. Surface electromyography (EMG) and kinematics of the lower extremities were measured at three skating velocities 3.33 m/s (slow), 5.00 m/s (medium) and 6.66 m/s (fast). The adductor magnus muscle exhibited disproportionately larger increases in peak muscle activation and significantly prolonged activation with increased speed. Stride rate and stride length also increased significantly with skating velocity, in contrast, hip, knee and ankle total ranges of motion did not. To accommodate for the increased stride rate with higher skating speeds, the rate of hip abduction increased significantly in concert with activations of adductor magnus indicating a substantial eccentric contraction. In conclusion, these findings highlight the functional importance of the adductor muscle group and hip abduction-adduction in skating performance as well as indirectly support the notion that groin strain injury potential increases with skating speed.

Impact of SCBA size and fatigue from different firefighting work cycles on firefighter gait.

PubMed

Kesler, Richard M; Bradley, Faith F; Deetjen, Grace S; Angelini, Michael J; Petrucci, Matthew N; Rosengren, Karl S; Horn, Gavin P; Hsiao-Wecksler, Elizabeth T

2018-04-04

Risk of slips, trips and falls in firefighters maybe influenced by the firefighter's equipment and duration of firefighting. This study examined the impact of a four self-contained breathing apparatus (SCBA) three SCBA of increasing size and a prototype design and three work cycles one bout (1B), two bouts with a five-minute break (2B) and two bouts back-to-back (BB) on gait in 30 firefighters. Five gait parameters (double support time, single support time, stride length, step width and stride velocity) were examined pre- and post-firefighting activity. The two largest SCBA resulted in longer double support times relative to the smallest SCBA. Multiple bouts of firefighting activity resulted in increased single and double support time and decreased stride length, step width and stride velocity. These results suggest that with larger SCBA or longer durations of activity, firefighters may adopt more conservative gait patterns to minimise fall risk. Practitioner Summary: The effects of four self-contained breathing apparatus (SCBA) and three work cycles on five gait parameters were examined pre- and post-firefighting activity. Both SCBA size and work cycle affected gait. The two largest SCBA resulted in longer double support times. Multiple bouts of activity resulted in more conservative gait patterns.

Generalization of improved step length symmetry from treadmill to overground walking in persons with stroke and hemiparesis†

PubMed Central

Savin, Douglas N.; Morton, Susanne M.; Whitall, Jill

2013-01-01

Objectives Determine whether adaptation to a swing phase perturbation during gait transferred from treadmill to overground walking, the rate of overground deadaptation, and whether overground aftereffects improved step length asymmetry in persons with hemiparetic stroke and gait asymmetry. Methods Ten participants with stroke and hemiparesis and 10 controls walked overground on an instrumented gait mat, adapted gait to a swing phase perturbation on a treadmill, then walked overground on the gait mat again. Outcome measures, primary: overground step length symmetry, rates of treadmill step length symmetry adaptation and overground step length symmetry deadaptation; secondary: overground gait velocity, stride length, and stride cycle duration. Results Step length symmetry aftereffects generalized to overground walking and adapted at a similar rate on the treadmill in both groups. Aftereffects decayed at a slower rate overground in participants with stroke and temporarily improved overground step length asymmetry. Both groups’ overground gait velocity increased post adaptation due to increased stride length and decreased stride duration. Conclusions Stroke and hemiparesis do not impair generalization of step length symmetry changes from adapted treadmill to overground walking, but prolong overground aftereffects. Significance Motor adaptation during treadmill walking may be an effective treatment for improving overground gait asymmetries post-stroke. PMID:24286858

A new look at the Dynamic Similarity Hypothesis: the importance of swing phase.

PubMed

Raichlen, David A; Pontzer, Herman; Shapiro, Liza J

2013-01-01

The Dynamic Similarity Hypothesis (DSH) suggests that when animals of different size walk at similar Froude numbers (equal ratios of inertial and gravitational forces) they will use similar size-corrected gaits. This application of similarity theory to animal biomechanics has contributed to fundamental insights in the mechanics and evolution of a diverse set of locomotor systems. However, despite its popularity, many mammals fail to walk with dynamically similar stride lengths, a key element of gait that determines spontaneous speed and energy costs. Here, we show that the applicability of the DSH is dependent on the inertial forces examined. In general, the inertial forces are thought to be the centripetal force of the inverted pendulum model of stance phase, determined by the length of the limb. If instead we model inertial forces as the centripetal force of the limb acting as a suspended pendulum during swing phase (determined by limb center of mass position), the DSH for stride length variation is fully supported. Thus, the DSH shows that inter-specific differences in spatial kinematics are tied to the evolution of limb mass distribution patterns. Selection may act on morphology to produce a given stride length, or alternatively, stride length may be a "spandrel" of selection acting on limb mass distribution.

ScienceCast 107: An Early Start for Noctilucent Clouds

NASA Image and Video Library

2013-06-07

Glowing electric-blue at the edge of space, noctilucent clouds have surprised researchers by appearing early this year. The unexpected apparition hints at a change in the "teleconnections" of Earth's atmosphere.

Making strides in women’s mental health care delivery in rural Ethiopia: demographics of a female outpatient psychiatric cohort at Jimma University Specialized Hospital (2006–2008)

PubMed Central

Chemali, Zeina N; Borba, Christina PC; Henderson, Tanya E; Tesfaye, Markos

2013-01-01

This paper presents the delivery of mental health care to a sample of women living in Jimma, rural Ethiopia, and their access to mental health services. A total of 226 psychiatric charts were reviewed for women seen at Jimma University Specialized Hospital. The mental health charts included documentation ranging from one paragraph to a full note. No psychiatric chart recorded medication status, detailed substance abuse history, or a history of violence. Rendering appropriate mental health care for women requires concerted efforts by multiple stake holders. Using our results, we advance concrete and practical suggestions for improving women’s mental health in rural Ethiopia. We point out that the health care system needs to be responsive, allowing for change starting with gender rights, so that rural women have access to basic mental health services. PMID:23901297

Theoretical considerations on maximum running speeds for large and small animals.

PubMed

Fuentes, Mauricio A

2016-02-07

Mechanical equations for fast running speeds are presented and analyzed. One of the equations and its associated model predict that animals tend to experience larger mechanical stresses in their limbs (muscles, tendons and bones) as a result of larger stride lengths, suggesting a structural restriction entailing the existence of an absolute maximum possible stride length. The consequence for big animals is that an increasingly larger body mass implies decreasing maximal speeds, given that the stride frequency generally decreases for increasingly larger animals. Another restriction, acting on small animals, is discussed only in preliminary terms, but it seems safe to assume from previous studies that for a given range of body masses of small animals, those which are bigger are faster. The difference between speed scaling trends for large and small animals implies the existence of a range of intermediate body masses corresponding to the fastest animals. Copyright © 2015 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bosler, Peter Andrew; Roesler, Erika Louise; Taylor, Mark A.

This article discusses the problem of identifying extreme climate events such as intense storms within large climate data sets. The basic storm detection algorithm is reviewed, which splits the problem into two parts: a spatial search followed by a temporal correlation problem. Two specific implementations of the spatial search algorithm are compared. The commonly used grid point search algorithm is reviewed, and a new algorithm called Stride Search is introduced. Stride Search is designed to work at all latitudes, while grid point searches may fail in polar regions. Results from the two algorithms are compared for the application of tropicalmore » cyclone detection, and shown to produce similar results for the same set of storm identification criteria. The time required for both algorithms to search the same data set is compared. Furthermore, Stride Search's ability to search extreme latitudes is demonstrated for the case of polar low detection.« less

Multidirectional walk test in individuals with Parkinson's disease: a validity study.

PubMed

Bryant, Mon S; Workman, Craig D; Jackson, George R

2015-03-01

Gait parameters of forward, backward, and sideways walk were studied when the participants walked overground in four directions at their self-selected speed and were compared with walking in the four directions on an instrumented GAITRite walkway. Intraclass correlation coefficients between the overground walk test measures and the instrumented walkway measures of gait speed, cadence, and stride length for the forward walk were 0.85, 0.88, and 0.87, respectively. For the backward walk, the coefficients were 0.91 for gait speed, 0.75 for cadence, and 0.93 for stride length. For the sideways walk, the coefficients were 0.92 for gait speed, 0.93 for cadence, and 0.94 for stride length. Gait parameters of forward, backward, and sideways walk obtained by the overground walk test had excellent agreement with those obtained by the instrumented walkway. The quick timed test provided quantitative data for gait evaluation and was valid for clinical use.

Is child walking conditioned by gender? Surface EMG patterns in female and male children.

PubMed

Di Nardo, Francesco; Laureati, Giulio; Strazza, Annachiara; Mengarelli, Alessandro; Burattini, Laura; Agostini, Valentina; Nascimbeni, Alberto; Knaflitz, Marco; Fioretti, Sandro

2017-03-01

EMG-based differences between females and males during walking are generally acknowledged in adults. Aim of the study was the quantification of possible gender differences in myoelectric activity of gastrocnemius lateralis (GL) and tibialis anterior (TA) during walking in school-age children. Gender-related comparison with adults was also provided to get possible novel insight in maturation of gait. To this aim, Statistical gait analysis, a recent methodology performing a statistical characterization of gait by averaging spatial-temporal and surface-EMG-based parameters over hundreds of strides, was performed in100 healthy school-age children (C-group) and in 33 healthy young adults (YA-group). On average, 301±110 consecutive strides were analyzed for each subject. In C-group, no significant differences (p>0.05) were observed between females and males in GL and TA, considering mean onset/offset instants of activation and occurrence frequency. Stratifying the C-group for age, small differences between females and males in occurrence frequency of GL arose in oldest children. In YA-group, females showed a significant propensity for a more complex recruitment of TA and GL (higher number of activations during gait cycle, quantified by occurrence frequency) compared to males. These outcomes suggest that gender-related differences in sEMG parameters do not characterize the recruitment of GL and TA during child walking in early years (6-8 years), start occurring when adolescence is approaching (10-12 years), and are acknowledged in both ankle muscles only in adults. Present findings seem to support previous studies on maturation of gait which indicate adolescence as the time-range where gait is completing its maturation path. Copyright © 2017 Elsevier B.V. All rights reserved.

Interaction of gusts with forest edges

NASA Astrophysics Data System (ADS)

Ruck, Bodo; Tischmacher, Michael

2012-05-01

Experimental investigations in an atmospheric boundary layer wind tunnel were carried out in order to study the interaction of gusts with forest edges. Summarizing the state of knowledge in the field of forest damages generated by extreme storms, there is a strong indication that in many cases, windthrow of trees starts near the forest edge from where it spreads into the stand. The high-transient interaction between gusts and (porous) forest edges produce unsteady flow phenomena not known so far. From a fluid mechanical point of view, the flow type resembles a forward-facing porous step flow, which is significantly influenced by the characteristics of the oncoming atmospheric boundary layer flow and the shape and `porous properties' of the forest edge. The paper reports systematic investigations on the interaction of artificially generated gusts and forest edge models in an atmospheric boundary layer wind tunnel. The experimental investigations were carried out with a laser-based time-resolved PIV-system and high speed photography. Different flow phenomena like gust streching, vortex formation, Kelvin-Helmholtz instabilities or wake production of turbulence could be measured or visualized contributing to the understanding of the complex flow perfomance over the forest edge.

The role of intrinsic muscle mechanics in the neuromuscular control of stable running in the guinea fowl

PubMed Central

Daley, Monica A; Voloshina, Alexandra; Biewener, Andrew A

2009-01-01

Here we investigate the interplay between intrinsic mechanical and neural factors in muscle contractile performance during running, which has been less studied than during walking. We report in vivo recordings of the gastrocnemius muscle of the guinea fowl (Numida meleagris), during the response and recovery from an unexpected drop in terrain. Previous studies on leg and joint mechanics following this perturbation suggested that distal leg extensor muscles play a key role in stabilisation. Here, we test this through direct recordings of gastrocnemius fascicle length (using sonomicrometry), muscle–tendon force (using buckle transducers), and activity (using indwelling EMG). Muscle recordings were analysed from the stride just before to the second stride following the perturbation. The gastrocnemius exhibits altered force and work output in the perturbed and first recovery strides. Muscle work correlates strongly with leg posture at the time of ground contact. When the leg is more extended in the drop step, net gastrocnemius work decreases (−5.2 J kg−1versus control), and when the leg is more flexed in the step back up, it increases (+9.8 J kg−1versus control). The muscle's work output is inherently stabilising because it pushes the body back toward its pre-perturbation (level running) speed and leg posture. Gastrocnemius length and force return to level running means by the second stride following the perturbation. EMG intensity differs significantly from level running only in the first recovery stride following the perturbation, not within the perturbed stride. The findings suggest that intrinsic mechanical factors contribute substantially to the initial changes in muscle force and work. The statistical results suggest that a history-dependent effect, shortening deactivation, may be an important factor in the intrinsic mechanical changes, in addition to instantaneous force–velocity and force–length effects. This finding suggests the potential need to incorporate history-dependent muscle properties into neuromechanical simulations of running, particularly if high muscle strains are involved and stability characteristics are important. Future work should test whether a Hill or modified Hill type model provides adequate prediction in such conditions. Interpreted in light of previous studies on walking, the findings support the concept of speed-dependent roles of reflex feedback. PMID:19359369

[Research progress of needles with knife-edge for carotid cardiac syndrome].

PubMed

Tan, Lingqiong; Zhao, Yanling

2015-04-01

According to topographic anatomy, pathogenesis and by retrieving, summarizing and analyzing literature regarding needle-knife and needles with knife-edge for carotid cardiac syndrome, it is found out that clinical misdiagnosis rate of carotid cardiac syndrome is considerably high. Needle-knife and needles with knife-edge could significantly improve the clinical symptoms of carotid cardiac syndrome, showing characteristic and advantage in treatment, but it is deficient in technique standard and efficacy criteria that should be united and authoritative. Researches regarding pathogenesis of carotid cardiac syndrome are not systematic. Clinical observation regarding long-term efficacy and relapse of needle-knife and needles with knife-edge treatment is rare. It is believed that the awareness on carotid cardiac syndrome should be increased to reduce misdiagnosis; scientific and standardized technique standard and efficacy criteria should be established; systematic and comprehensive researches regarding mechanism of needle-knife and needles with knife-edge for carotid cardiac syndrome should be launched; besides, clinical discussion regarding its long-term efficacy should start to provide a better clinical guideline.

Underwater bipedal locomotion by octopuses in disguise.

PubMed

Huffard, Christine L; Boneka, Farnis; Full, Robert J

2005-03-25

Here we report bipedal movement with a hydrostatic skeleton. Two species of octopus walk on two alternating arms using a rolling gait and appear to use the remaining six arms for camouflage. Octopus marginatus resembles a coconut, and Octopus (Abdopus) aculeatus, a clump of floating algae. Using underwater video, we analyzed the kinematics of their strides. Each arm was on the sand for more than half of the stride, qualifying this behavior as a form of walking.

Cognitive and motor dual task gait training improve dual task gait performance after stroke - A randomized controlled pilot trial.

PubMed

Liu, Yan-Ci; Yang, Yea-Ru; Tsai, Yun-An; Wang, Ray-Yau

2017-06-22

This study investigated effects of cognitive and motor dual task gait training on dual task gait performance in stroke. Participants (n = 28) were randomly assigned to cognitive dual task gait training (CDTT), motor dual task gait training (MDTT), or conventional physical therapy (CPT) group. Participants in CDTT or MDTT group practiced the cognitive or motor tasks respectively during walking. Participants in CPT group received strengthening, balance, and gait training. The intervention was 30 min/session, 3 sessions/week for 4 weeks. Three test conditions to evaluate the training effects were single walking, walking while performing cognitive task (serial subtraction), and walking while performing motor task (tray-carrying). Parameters included gait speed, dual task cost of gait speed (DTC-speed), cadence, stride time, and stride length. After CDTT, cognitive-motor dual task gait performance (stride length and DTC-speed) was improved (p = 0.021; p = 0.015). After MDTT, motor dual task gait performance (gait speed, stride length, and DTC-speed) was improved (p = 0.008; p = 0.008; p = 0.008 respectively). It seems that CDTT improved cognitive dual task gait performance and MDTT improved motor dual task gait performance although such improvements did not reach significant group difference. Therefore, different types of dual task gait training can be adopted to enhance different dual task gait performance in stroke.

Most suitable mother wavelet for the analysis of fractal properties of stride interval time series via the average wavelet coefficient

PubMed Central

Zhang, Zhenwei; VanSwearingen, Jessie; Brach, Jennifer S.; Perera, Subashan

2016-01-01

Human gait is a complex interaction of many nonlinear systems and stride intervals exhibit self-similarity over long time scales that can be modeled as a fractal process. The scaling exponent represents the fractal degree and can be interpreted as a biomarker of relative diseases. The previous study showed that the average wavelet method provides the most accurate results to estimate this scaling exponent when applied to stride interval time series. The purpose of this paper is to determine the most suitable mother wavelet for the average wavelet method. This paper presents a comparative numerical analysis of sixteen mother wavelets using simulated and real fractal signals. Simulated fractal signals were generated under varying signal lengths and scaling exponents that indicate a range of physiologically conceivable fractal signals. The five candidates were chosen due to their good performance on the mean square error test for both short and long signals. Next, we comparatively analyzed these five mother wavelets for physiologically relevant stride time series lengths. Our analysis showed that the symlet 2 mother wavelet provides a low mean square error and low variance for long time intervals and relatively low errors for short signal lengths. It can be considered as the most suitable mother function without the burden of considering the signal length. PMID:27960102

A pediatric correlational study of stride interval dynamics, energy expenditure and activity level.

PubMed

Ellis, Denine; Sejdic, Ervin; Zabjek, Karl; Chau, Tom

2014-08-01

The strength of time-dependent correlations known as stride interval (SI) dynamics has been proposed as an indicator of neurologically healthy gait. Most recently, it has been hypothesized that these dynamics may be necessary for gait efficiency although the supporting evidence to date is scant. The current study examines over-ground SI dynamics, and their relationship with the cost of walking and physical activity levels in neurologically healthy children aged nine to 15 years. Twenty participants completed a single experimental session consisting of three phases: 10 min resting, 15 min walking and 10 min recovery. The scaling exponent (α) was used to characterize SI dynamics while net energy cost was measured using a portable metabolic cart, and physical activity levels were determined based on a 7-day recall questionnaire. No significant linear relationships were found between a and the net energy cost measures (r < .07; p > .25) or between α and physical activity levels (r = .01, p = .62). However, there was a marked reduction in the variance of α as activity levels increased. Over-ground stride dynamics do not appear to directly reflect energy conservation of gait in neurologically healthy youth. However, the reduction in the variance of α with increasing physical activity suggests a potential exercise-moderated convergence toward a level of stride interval persistence for able-bodied youth reported in the literature. This latter finding warrants further investigation.

An on-ice measurement approach to analyse the biomechanics of ice hockey skating.

PubMed

Buckeridge, Erica; LeVangie, Marc C; Stetter, Bernd; Nigg, Sandro R; Nigg, Benno M

2015-01-01

Skating is a fundamental movement in ice hockey; however little research has been conducted within the field of hockey skating biomechanics due to the difficulties of on-ice data collection. In this study a novel on-ice measurement approach was tested for reliability, and subsequently implemented to investigate the forward skating technique, as well as technique differences across skill levels. Nine high caliber (High) and nine low caliber (Low) hockey players performed 30 m forward skating trials. A 3D accelerometer was mounted to the right skate for the purpose of stride detection, with the 2nd and 6th strides defined as acceleration and steady-state, respectively. The activity of five lower extremity muscles was recorded using surface electromyography. Biaxial electro-goniometers were used to quantify hip and knee angles, and in-skate plantar force was measured using instrumented insoles. Reliability was assessed with the coefficient of multiple correlation, which demonstrated moderate (r>0.65) to excellent (r>0.95) scores across selected measured variables. Greater plantar-flexor muscle activity and hip extension were evident during acceleration strides, while steady state strides exhibited greater knee extensor activity and hip abduction range of motion (p<0.05). High caliber exhibited greater hip range of motion and forefoot force application (p<0.05). The successful implementation of this on-ice mobile measurement approach offers potential for athlete monitoring, biofeedback and training advice.

An On-Ice Measurement Approach to Analyse the Biomechanics of Ice Hockey Skating

PubMed Central

Buckeridge, Erica; LeVangie, Marc C.; Stetter, Bernd; Nigg, Sandro R.; Nigg, Benno M.

2015-01-01

Skating is a fundamental movement in ice hockey; however little research has been conducted within the field of hockey skating biomechanics due to the difficulties of on-ice data collection. In this study a novel on-ice measurement approach was tested for reliability, and subsequently implemented to investigate the forward skating technique, as well as technique differences across skill levels. Nine high caliber (High) and nine low caliber (Low) hockey players performed 30m forward skating trials. A 3D accelerometer was mounted to the right skate for the purpose of stride detection, with the 2nd and 6th strides defined as acceleration and steady-state, respectively. The activity of five lower extremity muscles was recorded using surface electromyography. Biaxial electro-goniometers were used to quantify hip and knee angles, and in-skate plantar force was measured using instrumented insoles. Reliability was assessed with the coefficient of multiple correlation, which demonstrated moderate (r>0.65) to excellent (r>0.95) scores across selected measured variables. Greater plantar-flexor muscle activity and hip extension were evident during acceleration strides, while steady state strides exhibited greater knee extensor activity and hip abduction range of motion (p<0.05). High caliber exhibited greater hip range of motion and forefoot force application (p<0.05). The successful implementation of this on-ice mobile measurement approach offers potential for athlete monitoring, biofeedback and training advice. PMID:25973775

Stride-related rein tension patterns in walk and trot in the ridden horse.

PubMed

Egenvall, Agneta; Roepstorff, Lars; Eisersiö, Marie; Rhodin, Marie; van Weeren, René

2015-12-30

The use of tack (equipment such as saddles and reins) and especially of bits because of rein tension resulting in pressure in the mouth is questioned because of welfare concerns. We hypothesised that rein tension patterns in walk and trot reflect general gait kinematics, but are also determined by individual horse and rider effects. Six professional riders rode three familiar horses in walk and trot. Horses were equipped with rein tension meters logged by inertial measurement unit technique. Left and right rein tension data were synchronized with the gait. Stride split data (0-100 %) were analysed using mixed models technique to elucidate the left/right rein and stride percentage interaction, in relation to the exercises performed. In walk, rein tension was highest at hindlimb stance. Rein tension was highest in the suspension phase at trot, and lowest during the stance phase. In rising trot there was a significant difference between the two midstance phases, but not in sitting trot. When turning in trot there was a significant statistical association with the gait pattern with the tension being highest in the inside rein when the horse was on the outer fore-inner hindlimb diagonal. Substantial between-rider variation was demonstrated in walk and trot and between-horse variation in walk. Biphasic rein tensions patterns during the stride were found mainly in trot.

Differences in stride between healthy ostriches (Struthio camelus) and those affected by tibiotarsal rotation.

PubMed

Cooper, R G

2007-03-01

Twenty healthy ostriches (ten cocks and ten hens), and twenty birds with tibiotarsal rotation (nine cocks and 11 hens) (14 months old) were isolated, hooded and weighed. A run (50 m x 2.5 m) was divided into sections marked 5 m, 10 m, 15 m and 20 m. Time taken for each bird to pass these points was recorded and speed computed. The degree of tibiotarsal rotation in the right foot was mean +/- SEM, 156 +/- 2.69 degrees. Comparisons between left and right foot length in healthy birds showed no significant differences. Foot length was significantly lower in tibiotarsal rotation (P = 0.03). The right foot in tibiotarsal rotation was significantly shorter than the left foot. The number of strides per each 5 m division were significantly (P < 0.05) greater in tibiotarsal rotation by comparison with healthy birds. At 20 m, healthy cocks had more strides than hens. The stride length in hens was significantly (P < 0.05) greater than cocks at 5, 10 and 15 m, respectively, but lower throughout in tibiotarsal rotation (P = 0.001). The speed of hens was significantly (P < 0.05) greater than cocks. Tibiotarsal rotation resulted in significantly (P < 0.05) reduced speeds. Hens may be able to escape danger faster than cocks. The occurrence of tibiotarsal rotation necessitates consideration of genetics, management, sex, nutrition and growth rates.

Effect on Oxygen Cost of Transport from 8-Weeks of Progressive Training with Barefoot Running.

PubMed

Tam, N; Tucker, R; Astephen Wilson, J L; Santos-Concejero, J

2015-11-01

Popular interest in barefoot running has emerged as a result of its alleged performance and injury prevention benefits. Oxygen cost of transport (COT) improvements from barefoot running, however, remains equivocal. The aim of this study was to determine the influence of an 8-week progressive barefoot training program on COT and associated spatiotemporal variables. 15 male runners participated in this study. Variables such as oxygen uptake, biomechanical and spatiotemporal characteristics of gait, including ground contact (GC) and swing time; stride length and frequency and ankle plantar-dorsiflexion were measured pre- and post-intervention. The COT did not differ between barefoot and shod running either pre- or post-training. Improved barefoot COT (p<0.05) but not shod was found between pre- and post-training. Biomechanical differences between barefoot and shod conditions persisted over the training period. A decrease in barefoot COT was associated with a decrease in GC time (p=0.003, r=0.688) and a small increase in stride frequency (p=0.030; r=0.569). Ground contact time and stride frequency, previously associated with COT, only partly contribute (32% - Stride frequency and 47% - GC time) to a decrease in COT after barefoot training. Thus other physiological and biomechanical variables must influence the improvement in COT after a barefoot training intervention. © Georg Thieme Verlag KG Stuttgart · New York.

Dual-tasks and walking fast: relationship to extra-pyramidal signs in advanced Alzheimer disease.

PubMed

Camicioli, Richard; Bouchard, Thomas; Licis, Lisa

2006-10-25

Extra-pyramidal signs (EPS) and cadence predicted falls risk in patients with advanced Alzheimer disease (AD). Dual task performance predicts falls with variable success. Dual-task performance and walking fast were examined in advanced AD patients with EPS (EPS+, >3 modified Unified Parkinson's Disease Rating Scale [UPDRS] signs) or without EPS (EPS-, three or less UPDRS signs). Demographics, mental and functional status, behavioral impairment, EPS, and quantitative gait measures (GaitRite) were determined. The effects of an automatic dual-task (simple counting) and of walking fast on spatial and temporal gait characteristics were compared between EPS+ and EPS- subjects using a repeated measures design. Cadence decreased, while stride time, swing time and variability in swing time increased with the dual task. Results were insignificant after adjusting for secondary task performance. With walking fast, speed, cadence and stride length increased while stride time, swing time and double support time decreased. Although EPS+ subjects were slower and had decreased stride length, dual task and walking fast effects did not differ from EPS- subjects. Patient characteristics, the type of secondary task and the specific gait measures examined vary in the literature. In this moderately to severely demented population, EPS did not affect "unconscious" (dual task) or "conscious" (walking fast) gait modulation. Given their high falls risk, and retained ability to modulate walking, EPS+ AD patients may be ideal candidates for interventions aimed at preventing falls.

Non-linear dynamics of human locomotion: effects of rhythmic auditory cueing on local dynamic stability.

PubMed

Terrier, Philippe; Dériaz, Olivier

2013-01-01

It has been observed that times series of gait parameters [stride length (SL), stride time (ST), and stride speed (SS)], exhibit long-term persistence and fractal-like properties. Synchronizing steps with rhythmic auditory stimuli modifies the persistent fluctuation pattern to anti-persistence. Another non-linear method estimates the degree of resilience of gait control to small perturbations, i.e., the local dynamic stability (LDS). The method makes use of the maximal Lyapunov exponent, which estimates how fast a non-linear system embedded in a reconstructed state space (attractor) diverges after an infinitesimal perturbation. We propose to use an instrumented treadmill to simultaneously measure basic gait parameters (time series of SL, ST, and SS from which the statistical persistence among consecutive strides can be assessed), and the trajectory of the center of pressure (from which the LDS can be estimated). In 20 healthy participants, the response to rhythmic auditory cueing (RAC) of LDS and of statistical persistence [assessed with detrended fluctuation analysis (DFA)] was compared. By analyzing the divergence curves, we observed that long-term LDS (computed as the reverse of the average logarithmic rate of divergence between the 4th and the 10th strides downstream from nearest neighbors in the reconstructed attractor) was strongly enhanced (relative change +73%). That is likely the indication of a more dampened dynamics. The change in short-term LDS (divergence over one step) was smaller (+3%). DFA results (scaling exponents) confirmed an anti-persistent pattern in ST, SL, and SS. Long-term LDS (but not short-term LDS) and scaling exponents exhibited a significant correlation between them (r = 0.7). Both phenomena probably result from the more conscious/voluntary gait control that is required by RAC. We suggest that LDS and statistical persistence should be used to evaluate the efficiency of cueing therapy in patients with neurological gait disorders.

Pendular motion in the brachiation of captive Lagothrix and Ateles.

PubMed

Turnquist, J E; Schmitt, D; Rose, M D; Cant, J G

1999-01-01

Pendular motion during brachiation of captive Lagothrix lagothricha lugens and Ateles fusciceps robustus was analyzed to demonstrate similarities, and differences, between these two closely related large bodied atelines. This is the first captive study of the kinematics of brachiation in Lagothrix. Videorecordings of one adult male of each species were made in a specially designed cage constructed at the DuMond Conservancy/Monkey Jungle, Miami, FL. Java software (Jandel Scientific Inc., San Rafael, CA) was used for frame-by-frame kinematic analysis of individual strides/steps. Results demonstrate that the sequence of hand and tail contacts differ significantly between the two species with Lagothrix using a new tail hold with every hand hold, while Ateles generally utilizes a new tail hold with only every other hand hold. Stride length and stride frequency, even after adjusting for limb length, also differ significantly between the two species. Lagothrix brachiation utilizes short, choppy strides with quick hand holds, while Ateles uses long, fluid strides with longer hand holds. During brachiation not only is Lagothrix's body significantly less horizontal than that of Ateles but also, within Ateles, there are significant differences between steps depending on tail use. Because of the unique nature of tail use in Ateles, many aspects of body positioning in Lagothrix more closely resemble Ateles steps without a simultaneous tail hold rather than those with one. Overall pendulum length in Lagothrix is shorter than in Ateles. Tail use in Ateles has a significant effect on maximum pendulum length during a step. Although neither species achieves the extreme pendulum effect and long period of free-flight of hylobatids in fast ricochetal brachiation, in captivity both consistently demonstrate effective brachiation with brief periods of free-flight and pendular motion. Morphological similarities between ateline brachiators and hylobatids are fewer and less pronounced in Lagothrix than in Ateles. This study demonstrates that Lagothrix brachiation is also less hylobatid-like than that of Ateles.

Kinematic scaling of locomotion by hydrostatic animals: ontogeny of peristaltic crawling by the earthworm lumbricus terrestris

PubMed

Quillin

1999-03-01

This study examined the relationship between ontogenetic increase in body size and the kinematics of peristaltic locomotion by the earthworm Lumbricus terrestris, a soft-bodied organism supported by a hydrostatic skeleton. Whereas the motions of most vertebrates and arthropods are based primarily on the changes in the joint angles between rigid body segments, the motions of soft-bodied organisms with hydrostatic skeletons are based primarily on the changes in dimensions of the deformable body segments themselves. The overall kinematics of peristaltic crawling and the dynamic shape changes of individual earthworm segments were measured for individuals ranging in body mass (mb) by almost three orders of magnitude (0.012-8.5 g). Preferred crawling speed varied both within and among individuals: earthworms crawled faster primarily by taking longer strides, but also by taking more strides per unit time and by decreasing duty factor. On average, larger worms crawled at a greater absolute speed than smaller worms (U p2finity mb0.33) and did so by taking slightly longer strides (l p2finity mb0.41, where l is stride length) than expected by geometric similarity, using slightly lower stride frequencies (f p2finity mb-0.07) and the same duty factor (df p2finity mb-0.03). Circumferential and longitudinal body wall strains were generally independent of body mass, while strain rates changed little as a function of body mass. Given the extent of kinematic variation within and among earthworms, the crawling of earthworms of different sizes can be considered to show kinematic similarity when the kinematic variables are normalized by body length. Since the motions of peristaltic organisms are based primarily on changes in the dimensions of the deformable body wall, the scaling of the material properties of the body wall is probably an especially important determinant of the scaling of the kinematics of locomotion.

Influence of custom-made and prefabricated insoles before and after an intense run

PubMed Central

2017-01-01

Each time the foot contacts the ground during running there is a rapid deceleration that results in a shock wave that is transmitted from the foot to the head. The fatigue of the musculoskeletal system during running may decrease the ability of the body to absorb those shock waves and increase the risk of injury. Insoles are commonly prescribed to prevent injuries, and both custom-made and prefabricated insoles have been observed to reduce shock accelerations during running. However, no study to date has included a direct comparison of their behaviour measured over the same group of athletes, and therefore great controversy still exists regarding their effectiveness in reducing impact loading during running. The aim of the study was to analyse the acute differences in stride and shock parameters while running on a treadmill with custom-made and prefabricated insoles. Stride parameters (stride length, stride rate) and shock acceleration parameters (head and tibial peak acceleration, shock magnitude, acceleration rate, and shock attenuation) were measured using two triaxial accelerometers in 38 runners at 3.33 m/s before and after a 15-min intense run while using the sock liner of the shoe (control condition), prefabricated insoles and custom-made insoles. No differences in shock accelerations were found between the custom-made and the control insoles. The prefabricated insoles increased the head acceleration rate (post-fatigue, p = 0.029) compared to the control condition. The custom-made reduced tibial (pre-fatigue, p = 0.041) and head acceleration rates (pre-fatigue and post-fatigue, p = 0.01 and p = 0.046) compared to the prefabricated insoles. Neither the stride nor the acceleration parameters were modified as a result of the intense run. In the present study, the acute use of insoles (custom-made, prefabricated) did not reduce shock accelerations compared to the control insoles. Therefore, their effectiveness at protecting against injuries associated with elevated accelerations is not supported and remains unclear. PMID:28245273

Assessing Stride Variables and Vertical Stiffness with GPS-Embedded Accelerometers: Preliminary Insights for the Monitoring of Neuromuscular Fatigue on the Field

PubMed Central

Buchheit, Martin; Gray, Andrew; Morin, Jean-Benoit

2015-01-01

The aim of the present study was to examine the ability of a GPS-imbedded accelerometer to assess stride variables and vertical stiffness (K), which are directly related to neuromuscular fatigue during field-based high-intensity runs. The ability to detect stride imbalances was also examined. A team sport player performed a series of 30-s runs on an instrumented treadmill (6 runs at 10, 17 and 24 km·h-1) with or without his right ankle taped (aimed at creating a stride imbalance), while wearing on his back a commercially-available GPS unit with an embedded 100-Hz tri-axial accelerometer. Contact (CT) and flying (FT) time, and K were computed from both treadmill and accelerometers (Athletic Data Innovations) data. The agreement between treadmill (criterion measure) and accelerometer-derived data was examined. We also compared the ability of the different systems to detect the stride imbalance. Biases were small (CT and K) and moderate (FT). The typical error of the estimate was trivial (CT), small (K) and moderate (FT), with nearly perfect (CT and K) and large (FT) correlations for treadmill vs. accelerometer. The tape induced very large increase in the right - left foot ∆ in CT, FT and K measured by the treadmill. The tape effect on CT and K ∆ measured with the accelerometers were also very large, but of lower magnitude than with the treadmill. The tape effect on accelerometer-derived ∆ FT was unclear. Present data highlight the potential of a GPS-embedded accelerometer to assess CT and K during ground running. Key points GPS-embedded tri-axial accelerometers may be used to assess contact time and vertical stiffness during ground running. These preliminary results open new perspective for the field monitoring of neuromuscular fatigue and performance in run-based sports PMID:26664264

Design and experimental observation of valley-Hall edge states in diatomic-graphene-like elastic waveguides

NASA Astrophysics Data System (ADS)

Zhu, Hongfei; Liu, Ting-Wei; Semperlotti, Fabio

2018-05-01

We report on the design and experimental validation of a two-dimensional phononic elastic waveguide exhibiting topological valley-Hall edge states. The lattice structure of the waveguide is inspired by diatomic graphene, and it is imprinted in an initially flat plate by means of geometric indentations. The indentations are distributed according to a hexagonal lattice structure which guarantees the existence of Dirac dispersion at the boundary of the Brillouin zone. Starting from this basic material, domain walls capable of supporting edge states can be obtained by contrasting waveguides having broken space-inversion symmetry (SIS) achieved by using local resonant elements. Our theoretical study shows that such material maps into the acoustic analog of the quantum valley-Hall effect, while numerical and experimental results confirm the existence of protected edge states traveling along the walls of topologically distinct domains.

Fabrication and Testing of a Leading-Edge-Shaped Heat Pipe

NASA Technical Reports Server (NTRS)

Glass, David E.; Merrigan, Michael A.; Sena, J. Tom; Reid, Robert S.

1998-01-01

The development of a refractory-composite/heat-pipe-cooled leading edge has evolved from the design stage to the fabrication and testing of a full size, leading-edge-shaped heat pipe. The heat pipe had a 'D-shaped' cross section and was fabricated from arc cast Mo-4lRe. An artery was included in the wick. Several issues were resolved with the fabrication of the sharp leading edge radius heat pipe. The heat pipe was tested in a vacuum chamber at Los Alamos National Laboratory using induction heating and was started up from the frozen state several times. However, design temperatures and heat fluxes were not obtained due to premature failure of the heat pipe resulting from electrical discharge between the induction heating apparatus and the heat pipe. Though a testing anomaly caused premature failure of the heat pipe, successful startup and operation of the heat pipe was demonstrated.

Method and System for Determining Relative Displacement and Heading for Navigation

NASA Technical Reports Server (NTRS)

Sheikh, Suneel Ismail (Inventor); Pines, Darryll J. (Inventor); Conroy, Joseph Kim (Inventor); Spiridonov, Timofey N. (Inventor)

2015-01-01

A system and method for determining a location of a mobile object is provided. The system determines the location of the mobile object by determining distances between a plurality of sensors provided on a first and second movable parts of the mobile object. A stride length, heading, and separation distance between the first and second movable parts are computed based on the determined distances and the location of the mobile object is determined based on the computed stride length, heading, and separation distance.

Improvement in Body Image, Perceived Health, and Health-Related Self-Efficacy Among People With Serious Mental Illness: The STRIDE Study.

PubMed

Yarborough, Bobbi Jo H; Leo, Michael C; Yarborough, Micah T; Stumbo, Scott; Janoff, Shannon L; Perrin, Nancy A; Green, Carla A

2016-03-01

The authors examined secondary outcomes of STRIDE, a randomized controlled trial that tested a weight-loss and lifestyle intervention for individuals taking antipsychotic medications. Hierarchical linear regression was used to explore the effects of the intervention and weight change at follow-up (six, 12, and 24 months) on body image, perceived health, and health-related self-efficacy. Participants were 200 adults who were overweight and taking antipsychotic agents. Weight change × study arm interaction was associated with significant improvement in body image from baseline to six months. From baseline to 12 months, body image scores of intervention participants improved by 1.7 points more compared with scores of control participants; greater weight loss was associated with more improvement. Between baseline and 24 months, greater weight loss was associated with improvements in body image, perceived health, and health-related self-efficacy. Participation in STRIDE improved body image, and losing weight improved perceived health and health-related self-efficacy.

Does external walking environment affect gait patterns?

PubMed

Patterson, Matthew R; Whelan, Darragh; Reginatto, Brenda; Caprani, Niamh; Walsh, Lorcan; Smeaton, Alan F; Inomata, Akihiro; Caulfield, Brian

2014-01-01

The objective of this work is to develop an understanding of the relationship between mobility metrics obtained outside of the clinic or laboratory and the context of the external environment. Ten subjects walked with an inertial sensor on each shank and a wearable camera around their neck. They were taken on a thirty minute walk in which they mobilized over the following conditions; normal path, busy hallway, rough ground, blind folded and on a hill. Stride time, stride time variability, stance time and peak shank rotation rate during swing were calculated using previously published algorithms. Stride time was significantly different between several of the conditions. Technological advances mean that gait variables can now be captured as patients go about their daily lives. The results of this study show that the external environment has a significant impact on the quality of gait metrics. Thus, context of external walking environment is an important consideration when analyzing ambulatory gait metrics from the unsupervised home and community setting.

Lagrangian analysis of the laminar flat plate boundary layer

NASA Astrophysics Data System (ADS)

Gabr, Mohammad

2016-10-01

The flow properties at the leading edge of a flat plate represent a singularity to the Blasius laminar boundary layer equations; by applying the Lagrangian approach, the leading edge velocity profiles of the laminar boundary layer over a flat plate are studied. Experimental observations as well as the theoretical analysis show an exact Gaussian distribution curve as the original starting profile of the laminar flow. Comparisons between the Blasius solution and the Gaussian curve solution are carried out providing a new insight into the physics of the laminar flow.

Design at the Edge of the World: The Birth of American Air Intelligence in the China, Burma, India, and the Pacific Theaters during World War II

DTIC Science & Technology

2017-06-01

retaliatory strikes against Takao Harbor in Formosa, a pre - designated target in the event of war. As Eubank began to prepare his force, he found the target... DESIGN AT THE EDGE OF THE WORLD: THE BIRTH OF AMERICAN AIR INTELLIGENCE IN THE CHINA, BURMA, INDIA, AND THE PACIFIC THEATERS DURING WORLD WAR...At the start of World War II, American air intelligence was immature and the organization and design of intelligence often differed significantly

Volcanic ash clouds; a continuing threat to international aviation

USGS Publications Warehouse

Scarone, H.

1987-01-01

Suddenly, an acrid odour began to pervade the aircraft, an eerie bluish glow lit up the edges of the wings, and in the cockpit the familiar hum of static started to break up the high-frequency communications. Then it happened.

Exceptional running and turning performance in a mite.

PubMed

Rubin, Samuel; Young, Maria Ho-Yan; Wright, Jonathan C; Whitaker, Dwight L; Ahn, Anna N

2016-03-01

The Southern California endemic mite Paratarsotomus macropalpis was filmed in the field on a concrete substrate and in the lab to analyze stride frequency, gait and running speed under different temperature conditions and during turning. At ground temperatures ranging from 45 to 60 °C, mites ran at a mean relative speed of 192.4 ± 2.1 body lengths (BL) s(-1), exceeding the highest previously documented value for a land animal by 12.5%. Stride frequencies were also exceptionally high (up to 135 Hz), and increased with substrate temperature. Juveniles exhibited higher relative speeds than adults and possess proportionally longer legs, which allow for greater relative stride lengths. Although mites accelerated and decelerated rapidly during straight running (7.2 ± 1.2 and -10.1 ± 2.1 m s(-2), respectively), the forces involved were comparable to those found in other animals. Paratarsotomus macropalpis employs an alternating tetrapod gait during steady running. Shallow turns were accomplished by a simple asymmetry in stride length. During tight turns, mites pivoted around the tarsus of the inside third leg (L3), which thus behaved like a grappling hook. Pivot turns were characterized by a 42% decrease in turning radius and a 40% increase in angular velocity compared with non-pivot turns. The joint angle amplitudes of the inner L2 and L3 were negligible during a pivot turn. While exceptional, running speeds in P. macropalpis approximate values predicted from inter-specific scaling relationships. © 2016. Published by The Company of Biologists Ltd.

Ambulatory estimation of foot placement during walking using inertial sensors.

PubMed

Martin Schepers, H; van Asseldonk, Edwin H F; Baten, Chris T M; Veltink, Peter H

2010-12-01

This study proposes a method to assess foot placement during walking using an ambulatory measurement system consisting of orthopaedic sandals equipped with force/moment sensors and inertial sensors (accelerometers and gyroscopes). Two parameters, lateral foot placement (LFP) and stride length (SL), were estimated for each foot separately during walking with eyes open (EO), and with eyes closed (EC) to analyze if the ambulatory system was able to discriminate between different walking conditions. For validation, the ambulatory measurement system was compared to a reference optical position measurement system (Optotrak). LFP and SL were obtained by integration of inertial sensor signals. To reduce the drift caused by integration, LFP and SL were defined with respect to an average walking path using a predefined number of strides. By varying this number of strides, it was shown that LFP and SL could be best estimated using three consecutive strides. LFP and SL estimated from the instrumented shoe signals and with the reference system showed good correspondence as indicated by the RMS difference between both measurement systems being 6.5 ± 1.0 mm (mean ± standard deviation) for LFP, and 34.1 ± 2.7 mm for SL. Additionally, a statistical analysis revealed that the ambulatory system was able to discriminate between the EO and EC condition, like the reference system. It is concluded that the ambulatory measurement system was able to reliably estimate foot placement during walking. Copyright © 2010 Elsevier Ltd. All rights reserved.

An attempt to detect lameness in galloping horses by use of body-mounted inertial sensors.

PubMed

Lopes, Marco A F; Dearo, Antonio C O; Lee, Allen; Reed, Shannon K; Kramer, Joanne; Pai, P Frank; Yonezawa, Yoshiharu; Maki, Hiromitchi; Morgan, Terry L; Wilson, David A; Keegan, Kevin G

2016-10-01

OBJECTIVE To evaluate head, pelvic, and limb movement to detect lameness in galloping horses. ANIMALS 12 Thoroughbreds. PROCEDURES Movement data were collected with inertial sensors mounted on the head, pelvis, and limbs of horses trotting and galloping in a straight line before and after induction of forelimb and hind limb lameness by use of sole pressure. Successful induction of lameness was determined by measurement of asymmetric vertical head and pelvic movement during trotting. Differences in gallop strides before and after induction of lameness were evaluated with paired-sample statistical analysis and neural network training and testing. Variables included maximum, minimum, range, and time indices of vertical head and pelvic acceleration, head rotation in the sagittal plane, pelvic rotation in the frontal plane, limb contact intervals, stride durations, and limb lead preference. Difference between median standardized gallop strides for each limb lead before and after induction of lameness was calculated as the sum of squared differences at each time index and assessed with a 2-way ANOVA. RESULTS Head and pelvic acceleration and rotation, limb timing, stride duration measurements, and limb lead preference during galloping were not significantly different before and after induction of lameness in the forelimb or hind limb. Differences between limb leads before induction of lameness were similar to or greater than differences within limb leads before and after lameness induction. CONCLUSIONS AND CLINICAL RELEVANCE Galloping horses maintained asymmetry of head, pelvic, and limb motion between limb leads that was unrelated to lameness.

Signals from the ventrolateral thalamus to the motor cortex during locomotion

PubMed Central

Marlinski, Vladimir; Nilaweera, Wijitha U.; Zelenin, Pavel V.; Sirota, Mikhail G.

2012-01-01

The activity of the motor cortex during locomotion is profoundly modulated in the rhythm of strides. The source of modulation is not known. In this study we examined the activity of one of the major sources of afferent input to the motor cortex, the ventrolateral thalamus (VL). Experiments were conducted in chronically implanted cats with an extracellular single-neuron recording technique. VL neurons projecting to the motor cortex were identified by antidromic responses. During locomotion, the activity of 92% of neurons was modulated in the rhythm of strides; 67% of cells discharged one activity burst per stride, a pattern typical for the motor cortex. The characteristics of these discharges in most VL neurons appeared to be well suited to contribute to the locomotion-related activity of the motor cortex. In addition to simple locomotion, we examined VL activity during walking on a horizontal ladder, a task that requires vision for correct foot placement. Upon transition from simple to ladder locomotion, the activity of most VL neurons exhibited the same changes that have been reported for the motor cortex, i.e., an increase in the strength of stride-related modulation and shortening of the discharge duration. Five modes of integration of simple and ladder locomotion-related information were recognized in the VL. We suggest that, in addition to contributing to the locomotion-related activity in the motor cortex during simple locomotion, the VL integrates and transmits signals needed for correct foot placement on a complex terrain to the motor cortex. PMID:21994259

Fractal analyses reveal independent complexity and predictability of gait

PubMed Central

Dierick, Frédéric; Nivard, Anne-Laure

2017-01-01

Locomotion is a natural task that has been assessed for decades and used as a proxy to highlight impairments of various origins. So far, most studies adopted classical linear analyses of spatio-temporal gait parameters. Here, we use more advanced, yet not less practical, non-linear techniques to analyse gait time series of healthy subjects. We aimed at finding more sensitive indexes related to spatio-temporal gait parameters than those previously used, with the hope to better identify abnormal locomotion. We analysed large-scale stride interval time series and mean step width in 34 participants while altering walking direction (forward vs. backward walking) and with or without galvanic vestibular stimulation. The Hurst exponent α and the Minkowski fractal dimension D were computed and interpreted as indexes expressing predictability and complexity of stride interval time series, respectively. These holistic indexes can easily be interpreted in the framework of optimal movement complexity. We show that α and D accurately capture stride interval changes in function of the experimental condition. Walking forward exhibited maximal complexity (D) and hence, adaptability. In contrast, walking backward and/or stimulation of the vestibular system decreased D. Furthermore, walking backward increased predictability (α) through a more stereotyped pattern of the stride interval and galvanic vestibular stimulation reduced predictability. The present study demonstrates the complementary power of the Hurst exponent and the fractal dimension to improve walking classification. Our developments may have immediate applications in rehabilitation, diagnosis, and classification procedures. PMID:29182659

The Ergogenic Effect of Elastic Therapeutic Tape on Stride and Step Length in Fatigued Runners

PubMed Central

Ward, John; Sorrels, Kenneth; Coats, Jesse; Pourmoghaddam, Amir; Moskop, JoAnn; Ueckert, Kate; Glass, Amanda

2014-01-01

Objective The purpose of this study was to determine if elastic therapeutic tape placed on anterior lower limbs would affect stride and step length in fatigued runners’ gait. Methods Forty-two healthy participants were equally divided into a kinesiology tape group (Rocktape) and a no-tape control group. Participants in both groups underwent a baseline running gait test at 6 mph without tape. After this, participants engaged in an exhaustive lower body fatigue protocol until they reached maximal volitional exhaustion. Participants were then randomized to 1 of 2 interventions: (1) Experimental group, which had kinesiology tape placed under tension on the anterior aspect of their lower limbs bilaterally from the upper thigh to just below the patella, or (2) Control group, which did not receive taping. All participants then engaged in a similar 6-mph running gait postanalysis. Participant’s gait was analyzed for 90 seconds during each test iteration. Researchers used a 2-way repeated-measures analysis of variance considering fatigue (prefatigue, postfatigue) and group (tape, no-tape) as subject factors. Results After the fatigue protocol, the no-tape group demonstrated a significant decrease in step length of 14.2 mm (P = .041) and stride length of 29.4 mm (P = .043). The kinesiology tape group did not demonstrate a significant decline in these gait parameters. Conclusions In this preliminary study, placing elastic therapeutic tape over the anterior lower limbs demonstrated short-term preservation of runner step length and stride length in a fatigued state. PMID:25435835

Good agreement between smart device and inertial sensor-based gait parameters during a 6-min walk.

PubMed

Proessl, F; Swanson, C W; Rudroff, T; Fling, B W; Tracy, B L

2018-05-28

Traditional laboratory-based kinetic and kinematic gait analyses are expensive, time-intensive, and impractical for clinical settings. Inertial sensors have gained popularity in gait analysis research and more recently smart devices have been employed to provide quantification of gait. However, no study to date has investigated the agreement between smart device and inertial sensor-based gait parameters during prolonged walking. Compare spatiotemporal gait metrics measured with a smart device versus previously validated inertial sensors. Twenty neurologically healthy young adults (7 women; age: 25.0 ± 3.7 years; BMI: 23.4 ± 2.9 kg/m 2 ) performed a 6-min walk test (6MWT) wearing inertial sensors and smart devices to record stride duration, stride length, cadence, and gait speed. Pearson correlations were used to assess associations between spatiotemporal measures from the two devices and agreement between the two methods was assessed with Bland-Altman plots and limits of agreement. All spatiotemporal gait metrics (stride duration, cadence, stride length and gait speed) showed strong (r>0.9) associations and good agreement between the two devices. Smart devices are capable of accurately reflecting many of the spatiotemporal gait metrics of inertial sensors. As the smart devices also accurately reflected individual leg output, future studies may apply this analytical strategy to clinical populations, to identify hallmarks of disability status and disease progression in a more ecologically valid environment. Copyright © 2018. Published by Elsevier B.V.

The hindlimb in walking horses: 1. Kinematics and ground reaction forces.

PubMed

Hodson, E; Clayton, H M; Lanovaz, J L

2001-01-01

The objective was to study associations between kinematics and ground reaction forces in the hindlimb of walking horses. Video (60 Hz) and force (2000 Hz) data were gathered for 8 strides from each of 5 sound horses during the walk. Sagittal plane kinematics were measured concurrently with the vertical and longitudinal ground reaction forces. The hindlimb showed rapid loading and braking in the initial 10% stride. The stifle, tarsal and coffin joints flexed and the fetlock joint extended during this period of rapid loading. The vertical ground reaction force showed 2 peaks separated by a dip; this pattern was similar to the fetlock joint angle-time graph. Peaks in the longitudinal ground reaction force did not appear to correspond with kinematic events. Total braking impulse was equal to total propulsive impulse over the entire stride. Flexion and extension of the hip were responsible for protraction and retraction of the entire limb. Maximal protraction occurred shortly before the end of swing and maximal retraction occurred during breakover. During the middle part of stance the tarsal joint extended slowly, while the stifle began to flex when the limb was retracted beyond the midstance position at 28% stride. Flexion cycles of the stifle and tarsal joints were well coordinated during the swing phase to raise the distal limb as it was protracted. The results demonstrate a relationship between limb kinematics and vertical limb loading in the hindlimbs of sound horses. Future studies will elucidate the alterations in response to lameness.

Ground reaction forces of Olympic and World Championship race walkers.

PubMed

Hanley, Brian; Bissas, Athanassios

2016-01-01

Race walking is an Olympic event where no visible loss of contact should occur and the knee must be straightened until midstance. The purpose of this study was to analyse ground reaction forces of world-class race walkers and associate them with key spatiotemporal variables. Nineteen athletes race walked along an indoor track and made contact with two force plates (1000 Hz) while being filmed using high-speed videography (100 Hz). Race walking speed was correlated with flight time (r = .46, p = .049) and flight distance (r = .69, p = .001). The knee's movement from hyperextension to flexion during late stance meant the vertical push-off force that followed midstance was smaller than the earlier loading peak (p < .001), resulting in a flattened profile. Athletes with narrower stride widths experienced reduced peak braking forces (r = .49, p = .046), peak propulsive forces (r = .54, p = .027), peak medial forces (r = .63, p = .007) and peak vertical push-off forces (r = .60, p = .011). Lower fluctuations in speed during stance were associated with higher stride frequencies (r = .69, p = .001), and highlighted the importance of avoiding too much braking in early stance. The flattened trajectory and consequential decrease in vertical propulsion might help the race walker avoid visible loss of contact (although non-visible flight times were useful in increasing stride length), while a narrow stride width was important in reducing peak forces in all three directions and could improve movement efficiency.

Linear variability of gait according to socioeconomic status in elderly

PubMed Central

2016-01-01

Aim: To evaluate the linear variability of comfortable gait according to socioeconomic status in community-dwelling elderly. Method: For this cross-sectional observational study 63 self- functioning elderly were categorized according to the socioeconomic level on medium-low (n= 33, age 69.0 ± 5.0 years) and medium-high (n= 30, age 71.0 ± 6.0 years). Each participant was asked to perform comfortable gait speed for 3 min on an 40 meters elliptical circuit, recording in video five strides which were transformed into frames, determining the minimum foot clearance, maximum foot clearance and stride length. The intra-group linear variability was calculated by the coefficient of variation in percent. Results: The trajectory parameters variability is not different according to socioeconomic status with a 30% (range= 15-55%) for the minimum foot clearance and 6% (range= 3-8%) in maximum foot clearance. Meanwhile, the stride length consistently was more variable in the medium-low socioeconomic status for the overall sample (p= 0.004), female (p= 0.041) and male gender (p= 0.007), with values near 4% ​​(range = 2.5-5.0%) in the medium-low and 2% (range = 1.5-3.5%) in the medium-high. Conclusions: The intra-group linear variability is consistently higher and within reference parameters for stride length during comfortable gait for elderly belonging to medium-low socioeconomic status. This might be indicative of greater complexity and consequent motor adaptability. PMID:27546931

Investigation into seed collection practices and shrub manipulations to improve sustainable seed yield in wildland stands of bitterbrush (Purshia tridentata)

Treesearch

F. Leland Roberts

2007-01-01

The Great Basin is a series of unique ecosystems. Starting at the western edge of the Sierra Nevada mountain range in California it stretches east to the Wasatch Mountains of Utah. In the north it starts in central Oregon and Idaho and stretches south through out most of Nevada. In all the Great Basin is found in five states of the western U.S. The Great Basin supports...

Boundary conditions and formation of pure spin currents in magnetic field

NASA Astrophysics Data System (ADS)

Eliashvili, Merab; Tsitsishvili, George

2017-09-01

Schrödinger equation for an electron confined to a two-dimensional strip is considered in the presence of homogeneous orthogonal magnetic field. Since the system has edges, the eigenvalue problem is supplied by the boundary conditions (BC) aimed in preventing the leakage of matter away across the edges. In the case of spinless electrons the Dirichlet and Neumann BC are considered. The Dirichlet BC result in the existence of charge carrying edge states. For the Neumann BC each separate edge comprises two counterflow sub-currents which precisely cancel out each other provided the system is populated by electrons up to certain Fermi level. Cancelation of electric current is a good starting point for developing the spin-effects. In this scope we reconsider the problem for a spinning electron with Rashba coupling. The Neumann BC are replaced by Robin BC. Again, the two counterflow electric sub-currents cancel out each other for a separate edge, while the spin current survives thus modeling what is known as pure spin current - spin flow without charge flow.

Effect of supersonic molecular-beam injection on edge fluctuation and particle transport in Heliotron J

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zang, L., E-mail: l-zang@center.iae.kyoto-u.ac.jp; Kasajima, K.; Hashimoto, K.

Edge fluctuation in a supersonic molecular-beam injection (SMBI) fueled plasma has been measured using an electrostatic probe array. After SMBI, the plasma stored energy (W{sub p}) temporarily decreased then started to increase. The local plasma fluctuation and fluctuation induced particle transport before and after SMBI have been analyzed. In a short duration (∼4 ms) just after SMBI, the density fluctuation of broad-band low frequency increased, and the probability density function (PDF) changed from a nearly Gaussian to a positively skewed non-Gaussian one. This suggests that intermittent structures were produced due to SMBI. Also the fluctuation induced particle transport was greatly enhancedmore » during this short duration. About 4 ms after SMBI, the low frequency broad-band density fluctuation decreased, and the PDF returned to a nearly Gaussian shape. Also the fluctuation induced particle transport was reduced. Compared with conventional gas puff, W{sub p} degradation window is very short due to the short injection period of SMBI. After this short degradation window, fluctuation induced particle transport was reduced and W{sub p} started the climbing phase. Therefore, the short period of the influence to the edge fluctuation might be an advantage of this novel fueling technique. On the other hand, although their roles are not identified at present, coherent MHD modes are also suppressed as well by the application of SMBI. These MHD modes are thought to be de-exited due to a sudden change of the edge density and/or excitation conditions.« less

Pairing Symmetry Transitions in the Even-Denominator FQHE System

NASA Astrophysics Data System (ADS)

Nomura, Kentaro; Yoshioka, Daijiro

2001-12-01

Transitions from a paired quantum Hall state to another quantum Hall state in bilayer systems are discussed in the framework of the edge theory. Starting from the edge theory for the Haldane Rezayi state, it is shown that the charging effect of a bilayer system which breaks the SU(2) symmetry of the pseudospin shifts the central charge and the conformal dimensions of the fermionic fields which describe the pseudospin sector in the edge theory. This corresponds to the transition from the Haldane Rezayi state to Halperin's 331 state, or from a singlet d-wave to a triplet p-wave ABM type paired state in the composite fermion picture. Considering interlayer tunneling, the tunneling rate-capacitance phase diagram for the ν=5/2 paired bilayer system is discussed.

Semi-analytical model for a static sheath including a weakly collisional presheath

NASA Astrophysics Data System (ADS)

Shirafuji, Tatsuru; Denpoh, Kazuki

2018-06-01

A semi-analytical static sheath (SASS) model can provide a spatial potential profile on a biased surface with microstructures, which can be used for predicting ion trajectories on the surface. However, two- or three-dimensional SASS models require a search procedure for a sheath edge equipotential profile, at which ions have the Bohm velocity, as the starting positions for calculating ion trajectories. This procedure can be troublesome when surface microstructures have complex structures. This difficulty is due to the fact that the SASS model cannot handle a presheath region. In this work, we propose a modified SASS model that can handle a presheath region. By using the modified SASS model, ion trajectories can be calculated from edges with arbitrary geometry without searching for the equipotential profile corresponding to sheath edges.

Anti-dementia drugs and changes in gait: a pre-post quasi-experimental pilot study.

PubMed

Beauchet, Olivier; Launay, Cyrille P; Allali, Gazan; Watfa, Gilles; Gallouj, Karim; Herrmann, François R; Annweiler, Cédric

2013-11-21

Anti-dementia drugs may improve gait performance. No comparison between acetylcholinesterase inhibitors (CEIs) and memantine-related changes in gait variability has been reported. The objectives of this study were to 1) quantify and compare the mean values and coefficients of variation (CoV) of stride time in demented patients with Alzheimer's disease and related disorders (ADRD) before and after the use of CEIs or memantine, and in age- and gender-matched controls patients with ADRD using no anti-dementia drugs; and 2) to determine whether changes in CoV of stride time differed between CEIs or memantine. A total of 120 demented patients with mild-to-moderate ADRD were prospectively included in this pre-post quasi-experimental study with two intervention groups (43 patients taking CEIs, and 41 taking memantine) and a control group (36 age- and gender matched patients without any anti-dementia drugs). CoV of stride time and walking speed were measured with GAITRite® system while usual walking at steady state. Age, gender, number of drugs daily taken, use of psychoactive drugs, body mass index and time between the two visits were also recorded. There was no difference between groups for the time between baseline and follow-up assessments (232.9 ± 103.7 days for patients without anti-dementia drugs, 220.0 ± 67.5 days for patients with CEIs, 186.7 ± 96.2 days for patients with memantine, P = 0.062). Patients with memantine had a lower (i.e., better) CoV of stride time at follow-up assessment compared to those with CEIs (4.2 ± 2.4% versus 5.8 ± 4.2%, P = 0.010). Patients with memantine had a greater decrease in CoV of stride time compared to those with CEIs (-1.90% versus 0.93%, P = 0.010) and mixed-effects linear regressions showed that this decrease was specifically explained by memantine (P = 0.028). Our results showed that patients with ADRD and treated with memantine, but not those with CEIs, decreased their gait variability, and thus improved their gait safety (Trial registration number: NCT01315704).

Turbulence induced radial transport of toroidal momentum in boundary plasma of EAST tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, N.; Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031; Yan, N., E-mail: yanning@ipp.ac.cn

Turbulence induced toroidal momentum transport in boundary plasma is investigated in H-mode discharge using Langmuir-Mach probes on EAST. The Reynolds stress is found to drive an inward toroidal momentum transport, while the outflow of particles convects the toroidal momentum outwards in the edge plasma. The Reynolds stress driven momentum transport dominates over the passive momentum transport carried by particle flux, which potentially provides a momentum source for the edge plasma. The outflow of particles delivers a momentum flux into the scrape-off layer (SOL) region, contributing as a momentum source for the SOL flows. At the L-H transitions, the outward momentummore » transport suddenly decreases due to the suppression of edge turbulence and associated particle transport. The SOL flows start to decelerate as plasma entering into H-mode. The contributions from turbulent Reynolds stress and particle transport for the toroidal momentum transport are identified. These results shed lights on the understanding of edge plasma accelerating at L-H transitions.« less

Strongly reduced Ehrlich-Schwoebel barriers at the Cu (111) stepped surface with In and Pb surfactants

NASA Astrophysics Data System (ADS)

Hao, Jialei; Zhang, Lixin

2018-01-01

A surfactant can modify the properties of the surface and induce different mode of epitaxy growth. The atomistic mechanism is not fully understood yet. In this first-principles study, taking Cu homoepitaxy along (111) direction as an example, we show that the distribution of the surfactant atoms on the surface is the key. For In and Pb, they prefer to locate at the step edges and remain isolated. Once the growth is started, the distribution can be further modified by Cu adatoms. The uniquely decorated step edges have much lowered Ehrlich-Schwoebel (ES) barriers than that of the clean edges, thus the two dimensional growth on Cu (111) surface is promoted significantly. On the other hand, for Rh, Ir, and Au, these atoms are not favored at the step edges. The ES barriers can't be affected and these metals are not surfactants. The result is very helpful for searching of the optimal surfactants in metal homoepitaxy.

Anomalous - viscosity current drive

DOEpatents

Stix, Thomas H.; Ono, Masayuki

1988-01-01

An apparatus and method for maintaining a steady-state current in a toroidal magnetically confined plasma. An electric current is generated in an edge region at or near the outermost good magnetic surface of the toroidal plasma. The edge current is generated in a direction parallel to the flow of current in the main plasma and such that its current density is greater than the average density of the main plasma current. The current flow in the edge region is maintained in a direction parallel to the main current for a period of one or two of its characteristic decay times. Current from the edge region will penetrate radially into the plasma and augment the main plasma current through the mechanism of anomalous viscosity. In another aspect of the invention, current flow driven between a cathode and an anode is used to establish a start-up plasma current. The plasma-current channel is magnetically detached from the electrodes, leaving a plasma magnetically insulated from contact with any material obstructions including the cathode and anode.

Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot

PubMed Central

Jayaram, Kaushik; Full, Robert J.

2016-01-01

Jointed exoskeletons permit rapid appendage-driven locomotion but retain the soft-bodied, shape-changing ability to explore confined environments. We challenged cockroaches with horizontal crevices smaller than a quarter of their standing body height. Cockroaches rapidly traversed crevices in 300–800 ms by compressing their body 40–60%. High-speed videography revealed crevice negotiation to be a complex, discontinuous maneuver. After traversing horizontal crevices to enter a vertically confined space, cockroaches crawled at velocities approaching 60 cm⋅s−1, despite body compression and postural changes. Running velocity, stride length, and stride period only decreased at the smallest crevice height (4 mm), whereas slipping and the probability of zigzag paths increased. To explain confined-space running performance limits, we altered ceiling and ground friction. Increased ceiling friction decreased velocity by decreasing stride length and increasing slipping. Increased ground friction resulted in velocity and stride length attaining a maximum at intermediate friction levels. These data support a model of an unexplored mode of locomotion—“body-friction legged crawling” with body drag, friction-dominated leg thrust, but no media flow as in air, water, or sand. To define the limits of body compression in confined spaces, we conducted dynamic compressive cycle tests on living animals. Exoskeletal strength allowed cockroaches to withstand forces 300 times body weight when traversing the smallest crevices and up to nearly 900 times body weight without injury. Cockroach exoskeletons provided biological inspiration for the manufacture of an origami-style, soft, legged robot that can locomote rapidly in both open and confined spaces. PMID:26858443

Scaling of avian bipedal locomotion reveals independent effects of body mass and leg posture on gait.

PubMed

Daley, Monica A; Birn-Jeffery, Aleksandra

2018-05-22

Birds provide an interesting opportunity to study the relationships between body size, limb morphology and bipedal locomotor function. Birds are ecologically diverse and span a large range of body size and limb proportions, yet all use their hindlimbs for bipedal terrestrial locomotion, for at least some part of their life history. Here, we review the scaling of avian striding bipedal gaits to explore how body mass and leg morphology influence walking and running. We collate literature data from 21 species, spanning a 2500× range in body mass from painted quail to ostriches. Using dynamic similarity theory to interpret scaling trends, we find evidence for independent effects of body mass, leg length and leg posture on gait. We find no evidence for scaling of duty factor with body size, suggesting that vertical forces scale with dynamic similarity. However, at dynamically similar speeds, large birds use relatively shorter stride lengths and higher stride frequencies compared with small birds. We also find that birds with long legs for their mass, such as the white stork and red-legged seriema, use longer strides and lower swing frequencies, consistent with the influence of high limb inertia on gait. We discuss the observed scaling of avian bipedal gait in relation to mechanical demands for force, work and power relative to muscle actuator capacity, muscle activation costs related to leg cycling frequency, and considerations of stability and agility. Many opportunities remain for future work to investigate how morphology influences gait dynamics among birds specialized for different habitats and locomotor behaviors. © 2018. Published by The Company of Biologists Ltd.

Use of harmonic ratios to examine the effect of cueing strategies on gait stability in persons with Parkinson's disease.

PubMed

Lowry, Kristin A; Carrel, Andrew J; McIlrath, Jessica M; Smiley-Oyen, Ann L

2010-04-01

To determine if gait stability, as measured by harmonic ratios (HRs) derived from trunk accelerations, is improved during 3 amplitude-based cueing strategies (visual cues, lines on the floor 20% longer than preferred step length; verbal cues, experimenter saying "big step" every third; cognitive cues, participants think "big step") in people with Parkinson's disease. Gait analysis with a triaxial accelerometer. University research laboratory. A volunteer sample of persons with Parkinson's disease (N=7) (Hoehn and Yahr stages 2-3). Not applicable Gait stability was quantified by anterior-posterior (AP), vertical, and mediolateral (ML) HRs; higher ratios indicated improved gait stability. Spatiotemporal parameters assessed were walking speed, stride length, cadence, and the coefficient of variation for stride time. Of the amplitude-based cues, verbal and cognitive resulted in the largest improvements in the AP HR (P=.018) with a trend in the vertical HR as well as the largest improvements in both stride length and velocity. None of the cues positively affected stability in the ML direction. Descriptively, all participants increased speed and stride length, but only those in Hoehn and Yahr stage 2 (not Hoehn and Yahr stage 3) showed improvements in HRs. Cueing for "big steps" is effective for improving gait stability in the AP direction with modest improvements in the vertical direction, but it is not effective in the ML direction. These data support the use of trunk acceleration measures in assessing the efficacy of common therapeutic interventions. Copyright 2010 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Gait characteristics and spatio-temporal variables of climbing in bonobos (Pan paniscus).

PubMed

Schoonaert, Kirsten; D'Août, Kristiaan; Samuel, Diana; Talloen, Willem; Nauwelaerts, Sandra; Kivell, Tracy L; Aerts, Peter

2016-11-01

Although much is known about the terrestrial locomotion of great apes, their arboreal locomotion has been studied less extensively. This study investigates arboreal locomotion in bonobos (Pan paniscus), focusing on the gait characteristics and spatio-temporal variables associated with locomotion on a pole. These features are compared across different substrate inclinations (0°, 30°, 45°, 60°, and 90°), and horizontal quadrupedal walking is compared between an arboreal and a terrestrial substrate. Our results show greater variation in footfall patterns with increasing incline, resulting in more lateral gait sequences. During climbing on arboreal inclines, smaller steps and strides but higher stride frequencies and duty factors are found compared to horizontal arboreal walking. This may facilitate better balance control and dynamic stability on the arboreal substrate. We found no gradual change in spatio-temporal variables with increasing incline; instead, the results for all inclines were clustered together. Bonobos take larger strides at lower stride frequencies and lower duty factors on a horizontal arboreal substrate than on a flat terrestrial substrate. We suggest that these changes are the result of the better grip of the grasping feet on an arboreal substrate. Speed modulation of the spatio-temporal variables is similar across substrate inclinations and between substrate types, suggesting a comparable underlying motor control. Finally, we contrast these variables of arboreal inclined climbing with those of terrestrial bipedal locomotion, and briefly discuss the results with respect to the origin of habitual bipedalism. Am. J. Primatol. 78:1165-1177, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Accelerometric comparison of the locomotor pattern of horses sedated with xylazine hydrochloride, detomidine hydrochloride, or romifidine hydrochloride.

PubMed

López-Sanromán, F Javier; Holmbak-Petersen, Ronald; Varela, Marta; del Alamo, Ana M; Santiago, Isabel

2013-06-01

To evaluate the duration of effects on movement patterns of horses after sedation with equipotent doses of xylazine hydrochloride, detomidine hydrochloride, or romifidine hydrochloride and determine whether accelerometry can be used to quantify differences among drug treatments. 6 healthy horses. Each horse was injected IV with saline (0.9% NaCl) solution (10 mL), xylazine diluted in saline solution (0.5 mg/kg), detomidine diluted in saline solution (0.01 mg/kg), or romifidine diluted in saline solution (0.04 mg/kg) in random order. A triaxial accelerometric device was used for gait assessment 15 minutes before and 5, 15, 30, 45, 60, 75, 90, 105, and 120 minutes after each treatment. Eight variables were calculated, including speed, stride frequency, stride length, regularity, dorsoventral power, propulsive power, mediolateral power, and total power; the force of acceleration and 3 components of power were then calculated. Significant differences were evident in stride frequency and regularity between treatments with saline solution and each α2-adrenoceptor agonist drug; in speed, dorsoventral power, propulsive power, total power, and force values between treatments with saline solution and detomidine or romifidine; and in mediolateral power between treatments with saline solution and detomidine. Stride length did not differ among treatments. Accelerometric evaluation of horses administered α2-adrenoceptor agonist drugs revealed more prolonged sedative effects of romifidine, compared with effects of xylazine or detomidine. Accelerometry could be useful in assessing the effects of other sedatives and analgesics. Accelerometric data may be helpful in drug selection for situations in which a horse's balance and coordination are important.

Strategy quantification using body worn inertial sensors in a reactive agility task.

PubMed

Eke, Chika U; Cain, Stephen M; Stirling, Leia A

2017-11-07

Agility performance is often evaluated using time-based metrics, which provide little information about which factors aid or limit success. The objective of this study was to better understand agility strategy by identifying biomechanical metrics that were sensitive to performance speed, which were calculated with data from an array of body-worn inertial sensors. Five metrics were defined (normalized number of foot contacts, stride length variance, arm swing variance, mean normalized stride frequency, and number of body rotations) that corresponded to agility terms defined by experts working in athletic, clinical, and military environments. Eighteen participants donned 13 sensors to complete a reactive agility task, which involved navigating a set of cones in response to a vocal cue. Participants were grouped into fast, medium, and slow performance based on their completion time. Participants in the fast group had the smallest number of foot contacts (normalizing by height), highest stride length variance (normalizing by height), highest forearm angular velocity variance, and highest stride frequency (normalizing by height). The number of body rotations was not sensitive to speed and may have been determined by hand and foot dominance while completing the agility task. The results of this study have the potential to inform the development of a composite agility score constructed from the list of significant metrics. By quantifying the agility terms previously defined by expert evaluators through an agility score, this study can assist in strategy development for training and rehabilitation across athletic, clinical, and military domains. Copyright © 2017 Elsevier Ltd. All rights reserved.

Gait dynamics in Pisa syndrome and Camptocormia: The role of stride length and hip kinematics.

PubMed

Tramonti, C; Di Martino, S; Unti, E; Frosini, D; Bonuccelli, U; Rossi, B; Ceravolo, R; Chisari, C

2017-09-01

This is an observational cross-sectional study evaluating gait dynamics in patients with Parkinson's Disease (PD) and severe postural deformities, PD without axial deviations and healthy subjects. Ten PS individuals with Pisa syndrome (PS) and nine subjects with Camptocormia (CC) performed 3-D Gait Analysis and were evaluated with walking and balance scales. Correlations with clinical and functional scales were investigated. Spatio-temporal and kinematic data were compared to ten PD subjects without postural deformities (PP) and ten healthy matched individuals (CG). Data obtained showed decreased walking velocity, stride and step length in PP, PS and CC groups compared to controls. The correlation analysis showed that stride and step length were associated with reduced functional abilities and disease severity in PS and CC groups. Kinematic data revealed marked reduction in range of movements (ROMs) at all lower-extremity joints in PS group. While, in CC group the main differences were pronounced in hip and knee joints. PS and CC groups presented a more pronounced reduction in hip articular excursion compared to PP subjects, revealing an increased hip flexion pattern during gait cycle. Moreover, the increased hip and knee flexion pattern adversely affected functional performance during walking tests. Results obtained provide evidence that step length, along with stride length, can be proposed as simple and clear indicators of disease severity and reduced functional abilities. The reduction of ROMs at hip joint represented an important mechanism contributing to decreased walking velocity, balance impairment and reduced gait performance in PD patients with postural deformities. Copyright © 2017 Elsevier B.V. All rights reserved.

Factors Influencing Obstacle Crossing Performance in Patients with Parkinson's Disease

PubMed Central

Liao, Ying-Yi; Yang, Yea-Ru; Wu, Yih-Ru; Wang, Ray-Yau

2014-01-01

Background Tripping over obstacles is the major cause of falls in community-dwelling patients with Parkinson's disease (PD). Understanding the factors associated with the obstacle crossing behavior may help to develop possible training programs for crossing performance. This study aimed to identify the relationships and important factors determining obstacle crossing performance in patients with PD. Methods Forty-two idiopathic patients with PD (Hoehn and Yahr stages I to III) participated in this study. Obstacle crossing performance was recorded by the Liberty system, a three-dimensional motion capture device. Maximal isometric strength of the lower extremity was measured by a handheld dynamometer. Dynamic balance and sensory integration ability were assessed using the Balance Master system. Movement velocity (MV), maximal excursion (ME), and directional control (DC) were obtained during the limits of stability test to quantify dynamic balance. The sum of sensory organization test (SOT) scores was used to quantify sensory organization ability. Results Both crossing stride length and stride velocity correlated significantly with lower extremity muscle strength, dynamic balance control (forward and sideward), and sum of SOT scores. From the regression model, forward DC and ankle dorsiflexor strength were identified as two major determinants for crossing performance (R2 = .37 to.41 for the crossing stride length, R2 = .43 to.44 for the crossing stride velocity). Conclusions Lower extremity muscle strength, dynamic balance control and sensory integration ability significantly influence obstacle crossing performance. We suggest an emphasis on muscle strengthening exercises (especially ankle dorsiflexors), balance training (especially forward DC), and sensory integration training to improve obstacle crossing performance in patients with PD. PMID:24454723

The adaptation of limb kinematics to increasing walking speeds in freely moving mice 129/Sv and C57BL/6.

PubMed

Serradj, Nadjet; Jamon, Marc

2009-07-19

The kinematics of locomotion was analyzed in two strains of great importance for the creation of mutated mice (C56BL/6 and 129/Sv). Different behavioral situations were used to trigger sequences of movement covering the whole range of velocities in the mice, and the variations of kinematic parameters were analyzed in relation with velocity. Both stride frequency and stride length contributed to the moving speed, but stride frequency was found to be the main contributor to the speed increase. A trot-gallop transition was detected at speed about 70 cm/s, in relation with a sharp shift in limb coordination. The results of this study were consistent with pieces of information previously published concerning the gait analyses of other strains, and provided an integrative view of the basic motor pattern of mice. On the other hand some qualitative differences were found in the movement characteristics of the two strains. The stride frequency showed a higher contribution to speed in 129/Sv than in C57BL/6. In addition, 129/Sv showed a phase shift in the forelimb and hindlimb, and a different position of the foot during the stance time that revealed a different gait and body position during walking. Overall, 129/Sv moved at a slower speed than C57BL/6 in any behavioral situation. This difference was related to a basal lower level of motor activity. The possibility that an alteration in the dopamine circuit was responsible for the different movement pattern in 129/Sv is discussed.

Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot.

PubMed

Jayaram, Kaushik; Full, Robert J

2016-02-23

Jointed exoskeletons permit rapid appendage-driven locomotion but retain the soft-bodied, shape-changing ability to explore confined environments. We challenged cockroaches with horizontal crevices smaller than a quarter of their standing body height. Cockroaches rapidly traversed crevices in 300-800 ms by compressing their body 40-60%. High-speed videography revealed crevice negotiation to be a complex, discontinuous maneuver. After traversing horizontal crevices to enter a vertically confined space, cockroaches crawled at velocities approaching 60 cm⋅s(-1), despite body compression and postural changes. Running velocity, stride length, and stride period only decreased at the smallest crevice height (4 mm), whereas slipping and the probability of zigzag paths increased. To explain confined-space running performance limits, we altered ceiling and ground friction. Increased ceiling friction decreased velocity by decreasing stride length and increasing slipping. Increased ground friction resulted in velocity and stride length attaining a maximum at intermediate friction levels. These data support a model of an unexplored mode of locomotion--"body-friction legged crawling" with body drag, friction-dominated leg thrust, but no media flow as in air, water, or sand. To define the limits of body compression in confined spaces, we conducted dynamic compressive cycle tests on living animals. Exoskeletal strength allowed cockroaches to withstand forces 300 times body weight when traversing the smallest crevices and up to nearly 900 times body weight without injury. Cockroach exoskeletons provided biological inspiration for the manufacture of an origami-style, soft, legged robot that can locomote rapidly in both open and confined spaces.

Reliability of segmental accelerations measured using a new wireless gait analysis system.

PubMed

Kavanagh, Justin J; Morrison, Steven; James, Daniel A; Barrett, Rod

2006-01-01

The purpose of this study was to determine the inter- and intra-examiner reliability, and stride-to-stride reliability, of an accelerometer-based gait analysis system which measured 3D accelerations of the upper and lower body during self-selected slow, preferred and fast walking speeds. Eight subjects attended two testing sessions in which accelerometers were attached to the head, neck, lower trunk, and right shank. In the initial testing session, two different examiners attached the accelerometers and performed the same testing procedures. A single examiner repeated the procedure in a subsequent testing session. All data were collected using a new wireless gait analysis system, which features near real-time data transmission via a Bluetooth network. Reliability for each testing condition (4 locations, 3 directions, 3 speeds) was quantified using a waveform similarity statistic known as the coefficient of multiple determination (CMD). CMD's ranged from 0.60 to 0.98 across all test conditions and were not significantly different for inter-examiner (0.86), intra-examiner (0.87), and stride-to-stride reliability (0.86). The highest repeatability for the effect of location, direction and walking speed were for the shank segment (0.94), the vertical direction (0.91) and the fast walking speed (0.91), respectively. Overall, these results indicate that a high degree of waveform repeatability was obtained using a new gait system under test-retest conditions involving single and dual examiners. Furthermore, differences in acceleration waveform repeatability associated with the reapplication of accelerometers were small in relation to normal motor variability.

Stride dynamics, gait variability and prospective falls risk in active community dwelling older women.

PubMed

Paterson, Kade; Hill, Keith; Lythgo, Noel

2011-02-01

Measures of walking instability such as stride dynamics and gait variability have been shown to identify future fallers in older adult populations with gait limitations or mobility disorders. This study investigated whether measures of walking instability can predict future fallers (over a prospective 12 month period) in a group of healthy and active older women. Ninety-seven healthy active women aged between 55 and 90 years walked for 7 min around a continuous walking circuit. Gait data recorded by a GAITRite(®) walkway and foot-mounted accelerometers were used to calculate measures of stride dynamics and gait variability. The participant's physical function and balance were assessed. Fall incidence was monitored over the following 12 months. Inter-limb differences (p≤0.04) in stride dynamics were found for fallers (one or more falls) aged over 70 years, and multiple fallers (two or more falls) aged over 55 years, but not in non-fallers or a combined group of single and non-fallers. No group differences were found in the measures of physical function, balance or gait, including variability. Additionally, no gait variable predicted falls. Reduced coordination of inter-limb dynamics was found in active healthy older fallers and multiple fallers despite no difference in other measures of intrinsic falls risk. Evaluating inter-limb dynamics may be a clinically sensitive technique to detect early gait instability and falls risk in high functioning older adults, prior to change in other measures of physical function, balance and gait. Copyright © 2010 Elsevier B.V. All rights reserved.

Influence of shear cutting parameters on the fatigue behavior of a dual-phase steel

NASA Astrophysics Data System (ADS)

Paetzold, I.; Dittmann, F.; Feistle, M.; Golle, R.; Haefele, P.; Hoffmann, H.; Volk, W.

2017-09-01

The influence of the edge condition of car body and chassis components made of steel sheet on fatigue behavior under dynamic loading presents a major challenge for automotive manufacturers and suppliers. The calculated lifetime is based on material data determined by the fatigue testing of specimens with polished edges. Prototype components are often manufactured by milling or laser cutting, whereby in practice, the series components are produced by shear cutting due to its cost-efficiency. Since the fatigue crack in such components usually starts from a shear cut edge, the calculated and experimental determined lifetime will vary due to the different conditions at the shear cut edges. Therefore, the material data determined with polished edges can result in a non-conservative component design. The aim of this study is to understand the relationship between the shear cutting process and the fatigue behavior of a dual-phase steel sheet. The geometry of the shear cut edge as well as the depth and degree of work hardening in the shear affected zone can be adjusted by using specific shear cutting parameters, such as die clearance and cutting edge radius. Stress-controlled fatigue tests of unnotched specimens were carried out to compare the fatigue behavior of different edge conditions. By evaluating the results of the fatigue experiments, influential shear cutting parameters on fatigue behavior were identified. It was possible to assess investigated shear cutting strategies regarding the fatigue behavior of a high-strength steel DP800.

Investigating the interaction of x-ray free electron laser radiation with grating structure.

PubMed

Gaudin, Jérôme; Ozkan, Cigdem; Chalupský, Jaromír; Bajt, Saša; Burian, Tomáš; Vyšín, Ludek; Coppola, Nicola; Farahani, Shafagh Dastjani; Chapman, Henry N; Galasso, Germano; Hájková, Vera; Harmand, Marion; Juha, Libor; Jurek, Marek; Loch, Rolf A; Möller, Stefan; Nagasono, Mitsuru; Störmer, Michael; Sinn, Harald; Saksl, Karel; Sobierajski, Ryszard; Schulz, Joachim; Sovak, Pavol; Toleikis, Sven; Tiedtke, Kai; Tschentscher, Thomas; Krzywinski, Jacek

2012-08-01

The interaction of free electron laser pulses with grating structure is investigated using 4.6±0.1 nm radiation at the FLASH facility in Hamburg. For fluences above 63.7±8.7 mJ/cm2, the interaction triggers a damage process starting at the edge of the grating structure as evidenced by optical and atomic force microscopy. Simulations based on solution of the Helmholtz equation demonstrate an enhancement of the electric field intensity distribution at the edge of the grating structure. A procedure is finally deduced to evaluate damage threshold.

Lattice spin models for non-Abelian chiral spin liquids

DOE PAGES

Lecheminant, P.; Tsvelik, A. M.

2017-04-26

Here, we suggest a class of two-dimensional lattice spin Hamiltonians describing non-Abelian SU(2) chiral spin liquids—spin analogs of fractional non-Abelian quantum Hall states—with gapped bulk and gapless chiral edge excitations described by the SU(2) n Wess-Zumino-Novikov-Witten conformal field theory. The models are constructed from an array of generalized spin-n/2 ladders with multi-spin-exchange interactions which are coupled by isolated spins. Such models allow a controllable analytic treatment starting from the one-dimensional limit and are characterized by a bulk gap and non-Abelian SU(2) n gapless edge excitations.

Three-dimensional kinematics of the lower limbs during forward ice hockey skating.

PubMed

Upjohn, Tegan; Turcotte, René; Pearsall, David J; Loh, Jonathan

2008-05-01

The objectives of the study were to describe lower limb kinematics in three dimensions during the forward skating stride in hockey players and to contrast skating techniques between low- and high-calibre skaters. Participant motions were recorded with four synchronized digital video cameras while wearing reflective marker triads on the thighs, shanks, and skates. Participants skated on a specialized treadmill with a polyethylene slat bed at a self-selected speed for 1 min. Each participant completed three 1-min skating trials separated by 5 min of rest. Joint and limb segment angles were calculated within the local (anatomical) and global reference planes. Similar gross movement patterns and stride rates were observed; however, high-calibre participants showed a greater range and rate of joint motion in both the sagittal and frontal planes, contributing to greater stride length for high-calibre players. Furthermore, consequent postural differences led to greater lateral excursion during the power stroke in high-calibre skaters. In conclusion, specific kinematic differences in both joint and limb segment angle movement patterns were observed between low- and high-calibre skaters.

The Effects of Walking Workstations on Biomechanical Performance.

PubMed

Grindle, Daniel M; Baker, Lauren; Furr, Mike; Puterio, Tim; Knarr, Brian; Higginson, Jill

2018-04-03

Prolonged sitting has been associated with negative health effects. Walking workstations have become increasingly popular in the workplace. There is a lack of research on the biomechanical effect of walking workstations. This study analyzed whether walking while working alters normal gait patterns. Nine participants completed four walking trials at 2.4 km·h -1 and 4.0 km·h -1 : baseline walking condition, walking while performing a math task, a reading task, and a typing task. Biomechanical data were collected using standard motion capture procedures. The first maximum vertical ground reaction force, stride width, stride length, minimum toe clearance, peak swing hip abduction and flexion angles, peak swing and stance ankle dorsiflexion and knee flexion angles were analyzed. Differences between conditions were evaluated using analysis of variance tests with Bonferroni correction (p ≤ 0.05). Stride width decreased during the reading task at both speeds. Although other parameters exhibited significant differences when multitasking, these changes were within the normal range of gait variability. It appears that for short periods, walking workstations do not negatively impact gait in healthy young adults.

Control of voluntary and optogenetically perturbed locomotion by spike rate and timing of neurons of the mouse cerebellar nuclei

PubMed Central

Sarnaik, Rashmi

2018-01-01

Neurons of the cerebellar nuclei (CbN), which generate cerebellar output, are inhibited by Purkinje cells. With extracellular recordings during voluntary locomotion in head-fixed mice, we tested how the rate and coherence of inhibition influence CbN cell firing and well-practiced movements. Firing rates of Purkinje and CbN cells were modulated systematically through the stride cycle (~200–300 ms). Optogenetically stimulating ChR2-expressing Purkinje cells with light steps or trains evoked either asynchronous or synchronous inhibition of CbN cells. Steps slowed CbN firing. Trains suppressed CbN cell firing less effectively, but consistently altered millisecond-scale spike timing. Steps or trains that perturbed stride-related modulation of CbN cell firing rates correlated well with irregularities of movement, suggesting that ongoing locomotion is sensitive to alterations in modulated CbN cell firing. Unperturbed locomotion continued more often during trains than steps, however, suggesting that stride-related modulation of CbN spiking is less readily disrupted by synchronous than asynchronous inhibition. PMID:29659351

Reference data for normal subjects obtained with an accelerometric device.

PubMed

Auvinet, Bernard; Berrut, Gilles; Touzard, Claude; Moutel, Laurent; Collet, Nadine; Chaleil, Denis; Barrey, Eric

2002-10-01

We collected gait analysis data for 282 healthy adults and elderly people (144 women and 138 men aged 20-98) using an accelerometric device, whose reproducibility (intra-tester and inter-testers) has been validated for gait studies. The subjects walked at their own speed along a corridor (40 m). Stride frequency (SF) (after correction for height), step symmetry (Sym), stride regularity (Reg), and vertical harmonic (slope) were all independent of age or gender. The median-lateral harmonic (slope) (MSH) was influenced by gender, but not by age. Other variables (walking speed, stride length (SL), cranial-caudal activity and raw accelerations at heel contact, mid-stance and initial push-off) were dependent on gender and age. They were higher in men than in women, and began to decrease during the sixth decade in men and the seventh decade in women. The raw acceleration at foot flat was independent of gender but was influenced by age. This accelerometric device is easy to use and requires no specialized equipment and could be used to analyze walking in clinical practice.

Gait analysis in demented subjects: Interests and perspectives

PubMed Central

Beauchet, Olivier; Allali, Gilles; Berrut, Gilles; Hommet, Caroline; Dubost, Véronique; Assal, Frédéric

2008-01-01

Gait disorders are more prevalent in dementia than in normal aging and are related to the severity of cognitive decline. Dementia-related gait changes (DRGC) mainly include decrease in walking speed provoked by a decrease in stride length and an increase in support phase. More recently, dual-task related changes in gait were found in Alzheimer’s disease (AD) and non-Alzheimer dementia, even at an early stage. An increase in stride-to-stride variability while usual walking and dual-tasking has been shown to be more specific and sensitive than any change in mean value in subjects with dementia. Those data show that DRGC are not only associated to motor disorders but also to problem with central processing of information and highlight that dysfunction of temporal and frontal lobe may in part explain gait impairment among demented subjects. Gait assessment, and more particularly dual-task analysis, is therefore crucial in early diagnosis of dementia and/or related syndromes in the elderly. Moreover, dual-task disturbances could be a specific marker of falling at a pre-dementia stage. PMID:18728766

Replica Exchange Simulations of the Thermodynamics of Aβ Fibril Growth

PubMed Central

Takeda, Takako; Klimov, Dmitri K.

2009-01-01

Abstract Replica exchange molecular dynamics and an all-atom implicit solvent model are used to probe the thermodynamics of deposition of Alzheimer's Aβ monomers on preformed amyloid fibrils. Consistent with the experiments, two deposition stages have been identified. The docking stage occurs over a wide temperature range, starting with the formation of the first peptide-fibril interactions at 500 K. Docking is completed when a peptide fully adsorbs on the fibril edge at the temperature of 380 K. The docking transition appears to be continuous, and occurs without free energy barriers or intermediates. During docking, incoming Aβ monomer adopts a disordered structure on the fibril edge. The locking stage occurs at the temperature of ≈360 K and is characterized by the rugged free energy landscape. Locking takes place when incoming Aβ peptide forms a parallel β-sheet structure on the fibril edge. Because the β-sheets formed by locked Aβ peptides are typically off-registry, the structure of the locked phase differs from the structure of the fibril interior. The study also reports that binding affinities of two distinct fibril edges with respect to incoming Aβ peptides are different. The peptides bound to the concave edge have significantly lower free energy compared to those bound on the convex edge. Comparison with the available experimental data is discussed. PMID:19167295

Formation of a vortex at the edge of a plate

NASA Technical Reports Server (NTRS)

Anton, Leo

1956-01-01

The flow about the plate of infinite width may be represented as a potential flow with discontinuity surfaces which extend from the plate edges. For prescribed form and vortex distribution of the discontinuity surfaces, the velocity field may be calculated by means of a conformal representation. One condition is that the velocity at the plate edges must be finite. However, it is not sufficient for determination of the form and vortex distribution of the surface. However, on the basis of a similitude requirement one succeeds in finding a solution of this problem for the plate of infinite width which is correct for the very beginning of the motion of the fluid. Starting from this solution, the further development of the vortex distribution and shape of the surface are observed in the case of a plate of finite width.

Integration of uncooled scraper elements and its diagnostics into Wendelstein 7-X

DOE PAGES

Fellinger, Joris; Loesser, Doug; Neilson, Hutch; ...

2017-08-08

The modular stellarator Wendelstein 7-X in Greifswald (Germany) successfully started operation in 2015 with short pulse limiter plasmas. In 2017, the next operation phase (OP) OP1.2 will start once 10 uncooled test divertor units (TDU) with graphite armor will be installed. The TDUs allow for plasma pulses of 10 s with 8 MW heating. OP2, allowing for steady state operation, is planned for 2020 after the TDUs will be replaced by 10 water cooled CFC armored divertors. Due to the development of plasma currents like bootstrap currents in long pulse plasmas in OP2, the plasma could hit the edge ofmore » the divertor targets which has a reduced cooling capacity compared to the central part of the target tiles. To prevent overloading of these edges, a so-called scraper element can be positioned in front of the divertor, intersecting those strike lines that would otherwise hit the divertor edges. As a result, these edges are protected but as a drawback the pumping efficiency of neutrals is also reduced. As a test an uncooled scraper element with graphite tiles will be placed in two out of ten half modules in OP1.2. A decision to install ten water cooled scraper elements for OP2 is pending on the results of this test in OP1.2. To monitor the impact of the scraper element on the plasma, Langmuir probes are integrated in the plasma facing surface, and a neutral gas manometer measures the neutral density directly behind the plasma facing surface. Moreover, IR and VIS cameras observe the plasma facing surface and thermocouples monitor the temperatures of the graphite tiles and underlying support structure. This paper describes the integration of the scraper element and its diagnostics in Wendelstein 7-X.« less

Learning Lakota

ERIC Educational Resources Information Center

Kilman, Carrie

2006-01-01

Todd County, South Dakota, is synonymous with the Lakota Rosebud Reservation. It stretches across the state's south-central edge, bordered on one side by the better known Pine Ridge Reservation, where the American Indian Movement got its start, and on another side by Nebraska. Until the 1970s, generations of Indian children were forced from their…

Getting Started in Multimedia Training: Cutting or Bleeding Edge?

ERIC Educational Resources Information Center

Anderson, Vicki; Sleezer, Catherine M.

1995-01-01

Defines multimedia, explores uses of multimedia training, and discusses the effects and challenges of adding multimedia such as graphics, photographs, full motion video, sound effects, or CD-ROMs to existing training methods. Offers planning tips, and suggests software and hardware tools to help set up multimedia training programs. (JMV)

Static Stretching Alters Neuromuscular Function and Pacing Strategy, but Not Performance during a 3-Km Running Time-Trial

PubMed Central

Damasceno, Mayara V.; Duarte, Marcos; Pasqua, Leonardo A.; Lima-Silva, Adriano E.; MacIntosh, Brian R.; Bertuzzi, Rômulo

2014-01-01

Purpose Previous studies report that static stretching (SS) impairs running economy. Assuming that pacing strategy relies on rate of energy use, this study aimed to determine whether SS would modify pacing strategy and performance in a 3-km running time-trial. Methods Eleven recreational distance runners performed a) a constant-speed running test without previous SS and a maximal incremental treadmill test; b) an anthropometric assessment and a constant-speed running test with previous SS; c) a 3-km time-trial familiarization on an outdoor 400-m track; d and e) two 3-km time-trials, one with SS (experimental situation) and another without (control situation) previous static stretching. The order of the sessions d and e were randomized in a counterbalanced fashion. Sit-and-reach and drop jump tests were performed before the 3-km running time-trial in the control situation and before and after stretching exercises in the SS. Running economy, stride parameters, and electromyographic activity (EMG) of vastus medialis (VM), biceps femoris (BF) and gastrocnemius medialis (GA) were measured during the constant-speed tests. Results The overall running time did not change with condition (SS 11:35±00:31 s; control 11:28±00:41 s, p = 0.304), but the first 100 m was completed at a significantly lower velocity after SS. Surprisingly, SS did not modify the running economy, but the iEMG for the BF (+22.6%, p = 0.031), stride duration (+2.1%, p = 0.053) and range of motion (+11.1%, p = 0.0001) were significantly modified. Drop jump height decreased following SS (−9.2%, p = 0.001). Conclusion Static stretch impaired neuromuscular function, resulting in a slow start during a 3-km running time-trial, thus demonstrating the fundamental role of the neuromuscular system in the self-selected speed during the initial phase of the race. PMID:24905918

Walking-adaptability assessments with the Interactive Walkway: Between-systems agreement and sensitivity to task and subject variations.

PubMed

Geerse, Daphne J; Coolen, Bert H; Roerdink, Melvyn

2017-05-01

The ability to adapt walking to environmental circumstances is an important aspect of walking, yet difficult to assess. The Interactive Walkway was developed to assess walking adaptability by augmenting a multi-Kinect-v2 10-m walkway with gait-dependent visual context (stepping targets, obstacles) using real-time processed markerless full-body kinematics. In this study we determined Interactive Walkway's usability for walking-adaptability assessments in terms of between-systems agreement and sensitivity to task and subject variations. Under varying task constraints, 21 healthy subjects performed obstacle-avoidance, sudden-stops-and-starts and goal-directed-stepping tasks. Various continuous walking-adaptability outcome measures were concurrently determined with the Interactive Walkway and a gold-standard motion-registration system: available response time, obstacle-avoidance and sudden-stop margins, step length, stepping accuracy and walking speed. The same holds for dichotomous classifications of success and failure for obstacle-avoidance and sudden-stops tasks and performed short-stride versus long-stride obstacle-avoidance strategies. Continuous walking-adaptability outcome measures generally agreed well between systems (high intraclass correlation coefficients for absolute agreement, low biases and narrow limits of agreement) and were highly sensitive to task and subject variations. Success and failure ratings varied with available response times and obstacle types and agreed between systems for 85-96% of the trials while obstacle-avoidance strategies were always classified correctly. We conclude that Interactive Walkway walking-adaptability outcome measures are reliable and sensitive to task and subject variations, even in high-functioning subjects. We therefore deem Interactive Walkway walking-adaptability assessments usable for obtaining an objective and more task-specific examination of one's ability to walk, which may be feasible for both high-functioning and fragile populations since walking adaptability can be assessed at various levels of difficulty. Copyright © 2017 Elsevier B.V. All rights reserved.

Frequency of and risk factors associated with catastrophic musculoskeletal injuries in Quarter Horses at two Midwestern racetracks: 67 cases (2000-2011).

PubMed

Beisser, Andrea; McClure, Scott; Rezabek, Grant; Soring, Keith H; Wang, Chong

2014-11-15

To determine the incidence and anatomic location of and potential risk factors for catastrophic musculoskeletal injuries (CMIs) in racing Quarter Horses. Retrospective matched case-control study. 67 racing Quarter Horse racehorses euthanized because of CMIs and 134 matched controls. Data for Quarter Horses that sustained CMIs and the total number of race starts for each year were obtained from 2 Midwestern racing jurisdictions from 2000 through 2011. Information for each horse with a CMI and for 2 randomly selected control horses that ran in the same race but did not incur a CMI were obtained from race records, past performance reports, and video analysis. There were 61,797 race starts and 82 CMIs from 2000 through 2011 at the 2 racetracks studied, for an overall CMI incidence of 1.33 CMIs/1,000 starts. Sixty-seven horses with CMIs for which complete data were available and 134 matched control horses were included in the study. There was no difference in the incidence of CMIs between the 2 racetracks or over the years studied. The right forelimb was injured in 38 of the 67 (56.7%) horses. Injures to the carpus (24/67 [35.8%]) and metacarpophalangeal joint (fetlock joint; 23/67 [34.3%]) occurred most frequently. Case-control data indicated that the horses with a CMI had fewer starts, were more likely to have stumbled at the break, had a more erratic stride, were fatigued, and trailed in the race, compared with matched controls from the same races. Irrespective of race distance, most of the horses (47/67 [70.1%]) were injured after or within 10 yards before the finish line. The results of the present study may aid in the identification of racing Quarter Horses at risk for CMIs. The cluster of injuries near the finish line provides a specific focus for future research into methods of injury prevention in this population of racehorses.

Instrumented gait analysis: a measure of gait improvement by a wheeled walker in hospitalized geriatric patients.

PubMed

Schülein, Samuel; Barth, Jens; Rampp, Alexander; Rupprecht, Roland; Eskofier, Björn M; Winkler, Jürgen; Gaßmann, Karl-Günter; Klucken, Jochen

2017-02-27

In an increasing aging society, reduced mobility is one of the most important factors limiting activities of daily living and overall quality of life. The ability to walk independently contributes to the mobility, but is increasingly restricted by numerous diseases that impair gait and balance. The aim of this cross-sectional observation study was to examine whether spatio-temporal gait parameters derived from mobile instrumented gait analysis can be used to measure the gait stabilizing effects of a wheeled walker (WW) and whether these gait parameters may serve as surrogate marker in hospitalized patients with multifactorial gait and balance impairment. One hundred six patients (ages 68-95) wearing inertial sensor equipped shoes passed an instrumented walkway with and without gait support from a WW. The walkway assessed the risk of falling associated gait parameters velocity, swing time, stride length, stride time- and double support time variability. Inertial sensor-equipped shoes measured heel strike and toe off angles, and foot clearance. The use of a WW improved the risk of spatio-temporal parameters velocity, swing time, stride length and the sagittal plane associated parameters heel strike and toe off angles in all patients. First-time users (FTUs) showed similar gait parameter improvement patterns as frequent WW users (FUs). However, FUs with higher levels of gait impairment improved more in velocity, stride length and toe off angle compared to the FTUs. The impact of a WW can be quantified objectively by instrumented gait assessment. Thus, objective gait parameters may serve as surrogate markers for the use of walking aids in patients with gait and balance impairments.

Three-Dimensional Kinematic Gait Analysis of Doberman Pinschers with and without Cervical Spondylomyelopathy

PubMed Central

Foss, K.; da Costa, R.C.; Moore, S.

2014-01-01

Background The optimal treatment of cervical spondylomyelopathy (CSM) is controversial, with the owner’s and clinician’s perception of gait improvement often being used as outcome measures. These methods are subjective and suffer from observer bias. Objectives To establish kinematic gait parameters utilizing digital motion capture in normal Doberman Pinschers and compare them with CSM-affected Dobermans. Animals Nineteen Doberman Pinschers; 10 clinically normal and 9 with CSM. Methods All dogs were enrolled prospectively and fitted with a Lycra® body suit, and motion capture was performed and used to reconstruct a 3-D stick diagram representation of each dog based on 32 reflective markers, from which several parameters were measured. These included stride duration, length, and height; maximal and minimal spinal angles; elbow and stifle flexion and extension; and maximum and minimum distances between the thoracic and pelvic limbs. A random-effects linear regression model was used to compare parameters between groups. Results Significant differences between groups included smaller minimum (mean = 116 mm; P = .024) and maximum (mean = 184 mm; P = .001) distance between the thoracic limbs in CSM-affected dogs. Additionally, thoracic limb stride duration was also smaller (P = .009) in CSM-affected dogs (mean = 0.7 seconds) when compared with normal dogs (mean = 0.8 seconds). In the pelvic limbs, the average stifle flexion (mean = 100°; P = .048) and extension (mean = 136°; P = .009), as well as number of strides (mean = 2.7 strides; P = .033) were different between groups. Conclusions and Clinical Importance Our findings suggest that computerized gait analysis reveals more consistent kinematic differences in the thoracic limbs, which can be used as future objective outcome measures. PMID:23194100

Textured insoles reduce vertical loading rate and increase subjective plantar sensation in overground running.

PubMed

Wilkinson, Michael; Ewen, Alistair; Caplan, Nicholas; O'leary, David; Smith, Neil; Stoneham, Richard; Saxby, Lee

2018-05-01

The effect of textured insoles on kinetics and kinematics of overground running was assessed. 16 male injury-free-recreational runners attended a single visit (age 23 ± 5 yrs; stature 1.78 ± 0.06 m; mass 72.6 ± 9.2 kg). Overground 15-m runs were completed in flat, canvas plimsolls both with and without textured insoles at self-selected velocity on an indoor track in an order that was balanced among participants. Average vertical loading rate and peak vertical force (F peak ) were captured by force platforms. Video footage was digitised for sagittal plane hip, knee and ankle angles at foot strike and mid stance. Velocity, stride rate and length and contact and flight time were determined. Subjectively rated plantar sensation was recorded by visual scale. 95% confidence intervals estimated mean differences. Smallest worthwhile change in loading rate was defined as standardised reduction of 0.54 from a previous comparison of injured versus non-injured runners. Loading rate decreased (-25 to -9.3 BW s -1 ; 60% likely beneficial reduction) and plantar sensation was increased (46-58 mm) with the insole. F peak (-0.1 to 0.14 BW) and velocity (-0.02 to 0.06 m s -1 ) were similar. Stride length, flight and contact time were lower (-0.13 to -0.01 m; -0.02 to-0.01 s; -0.016 to -0.006 s) and stride rate was higher (0.01-0.07 steps s -1 ) with insoles. Textured insoles elicited an acute, meaningful decrease in vertical loading rate in short distance, overground running and were associated with subjectively increased plantar sensation. Reduced vertical loading rate could be explained by altered stride characteristics.

Is There an Economical Running Technique? A Review of Modifiable Biomechanical Factors Affecting Running Economy.

PubMed

Moore, Isabel S

2016-06-01

Running economy (RE) has a strong relationship with running performance, and modifiable running biomechanics are a determining factor of RE. The purposes of this review were to (1) examine the intrinsic and extrinsic modifiable biomechanical factors affecting RE; (2) assess training-induced changes in RE and running biomechanics; (3) evaluate whether an economical running technique can be recommended and; (4) discuss potential areas for future research. Based on current evidence, the intrinsic factors that appeared beneficial for RE were using a preferred stride length range, which allows for stride length deviations up to 3 % shorter than preferred stride length; lower vertical oscillation; greater leg stiffness; low lower limb moment of inertia; less leg extension at toe-off; larger stride angles; alignment of the ground reaction force and leg axis during propulsion; maintaining arm swing; low thigh antagonist-agonist muscular coactivation; and low activation of lower limb muscles during propulsion. Extrinsic factors associated with a better RE were a firm, compliant shoe-surface interaction and being barefoot or wearing lightweight shoes. Several other modifiable biomechanical factors presented inconsistent relationships with RE. Running biomechanics during ground contact appeared to play an important role, specifically those during propulsion. Therefore, this phase has the strongest direct links with RE. Recurring methodological problems exist within the literature, such as cross-comparisons, assessing variables in isolation, and acute to short-term interventions. Therefore, recommending a general economical running technique should be approached with caution. Future work should focus on interdisciplinary longitudinal investigations combining RE, kinematics, kinetics, and neuromuscular and anatomical aspects, as well as applying a synergistic approach to understanding the role of kinetics.

3D gait assessment in young and elderly subjects using foot-worn inertial sensors.

PubMed

Mariani, Benoit; Hoskovec, Constanze; Rochat, Stephane; Büla, Christophe; Penders, Julien; Aminian, Kamiar

2010-11-16

This study describes the validation of a new wearable system for assessment of 3D spatial parameters of gait. The new method is based on the detection of temporal parameters, coupled to optimized fusion and de-drifted integration of inertial signals. Composed of two wirelesses inertial modules attached on feet, the system provides stride length, stride velocity, foot clearance, and turning angle parameters at each gait cycle, based on the computation of 3D foot kinematics. Accuracy and precision of the proposed system were compared to an optical motion capture system as reference. Its repeatability across measurements (test-retest reliability) was also evaluated. Measurements were performed in 10 young (mean age 26.1±2.8 years) and 10 elderly volunteers (mean age 71.6±4.6 years) who were asked to perform U-shaped and 8-shaped walking trials, and then a 6-min walking test (6MWT). A total of 974 gait cycles were used to compare gait parameters with the reference system. Mean accuracy±precision was 1.5±6.8cm for stride length, 1.4±5.6cm/s for stride velocity, 1.9±2.0cm for foot clearance, and 1.6±6.1° for turning angle. Difference in gait performance was observed between young and elderly volunteers during the 6MWT particularly in foot clearance. The proposed method allows to analyze various aspects of gait, including turns, gait initiation and termination, or inter-cycle variability. The system is lightweight, easy to wear and use, and suitable for clinical application requiring objective evaluation of gait outside of the lab environment. Copyright © 2010 Elsevier Ltd. All rights reserved.

Functional implications of muscle co-contraction during gait in advanced age.

PubMed

Lo, Justine; Lo, On-Yee; Olson, Erin A; Habtemariam, Daniel; Iloputaife, Ikechukwu; Gagnon, Margaret M; Manor, Brad; Lipsitz, Lewis A

2017-03-01

Older adults often exhibit high levels of lower extremity muscle co-contraction, which may be the cause or effect of age-related impairments in gait and associated falls. Normal gait requires intact executive function and thus can be slowed by challenging executive resources available to the neuromuscular system through the performance of a dual task. We therefore investigated associations between lower limb co-contraction and gait characteristics under normal and dual task conditions in healthy older adults (85.4±5.9years). We hypothesized that greater co-contraction is associated with slower gait speed during dual task conditions that stress executive and attentional abilities. Co-contraction was quantified during different phases of the gait cycle using surface electromyography (EMG) signals obtained from the anterior tibialis and lateral gastrocnemius while walking at preferred speed during normal and dual task conditions. Variables included the time difference to complete the Trail Making Test A and B (ΔTMT) and gait measures during normal or dual task walking. Higher co-contraction levels during the swing phase of both normal and dual task walking were associated with longer ΔTMT (normal: R 2 =0.25, p=0.02; dual task: R 2 =0.27, p=0.01). Co-contraction was associated with gait measures during dual task walking only; greater co-contraction levels during stride and stance were associated with slower gait speed (stride: R 2 =0.38, p=0.04; stance: R 2 =0.38, p=0.04), and greater co-contraction during stride was associated with longer stride time (R 2 =0.16, p=0.03). Our results suggest that relatively high lower limb co-contraction may explain some of the mobility impairments associated with the conduct of executive tasks in older adults. Copyright © 2017 Elsevier B.V. All rights reserved.

An Automatic Gait Feature Extraction Method for Identifying Gait Asymmetry Using Wearable Sensors

PubMed Central

Vassallo, Michael

2018-01-01

This paper aims to assess the use of Inertial Measurement Unit (IMU) sensors to identify gait asymmetry by extracting automatic gait features. We design and develop an android app to collect real time synchronous IMU data from legs. The results from our method are validated using a Qualisys Motion Capture System. The data are collected from 10 young and 10 older subjects. Each performed a trial in a straight corridor comprising 15 strides of normal walking, a turn around and another 15 strides. We analyse the data for total distance, total time, total velocity, stride, step, cadence, step ratio, stance, and swing. The accuracy of detecting the stride number using the proposed method is 100% for young and 92.67% for older subjects. The accuracy of estimating travelled distance using the proposed method for young subjects is 97.73% and 98.82% for right and left legs; and for the older, is 88.71% and 89.88% for right and left legs. The average travelled distance is 37.77 (95% CI ± 3.57) meters for young subjects and is 22.50 (95% CI ± 2.34) meters for older subjects. The average travelled time for young subjects is 51.85 (95% CI ± 3.08) seconds and for older subjects is 84.02 (95% CI ± 9.98) seconds. The results show that wearable sensors can be used for identifying gait asymmetry without the requirement and expense of an elaborate laboratory setup. This can serve as a tool in diagnosing gait abnormalities in individuals and opens the possibilities for home based self-gait asymmetry assessment. PMID:29495299

Together We STRIDE: A quasi-experimental trial testing the effectiveness of a multi-level obesity intervention for Hispanic children in rural communities.

PubMed

Ko, Linda K; Rillamas-Sun, Eileen; Bishop, Sonia; Cisneros, Oralia; Holte, Sarah; Thompson, Beti

2018-04-01

Hispanic children are disproportionally overweight and obese compared to their non-Hispanic white counterparts in the US. Community-wide, multi-level interventions have been successful to promote healthier nutrition, increased physical activity (PA), and weight loss. Using community-based participatory approach (CBPR) that engages community members in rural Hispanic communities is a promising way to promote behavior change, and ultimately weight loss among Hispanic children. Led by a community-academic partnership, the Together We STRIDE (Strategizing Together Relevant Interventions for Diet and Exercise) aims to test the effectiveness of a community-wide, multi-level intervention to promote healthier diets, increased PA, and weight loss among Hispanic children. The Together We STRIDE is a parallel quasi-experimental trial with a goal of recruiting 900 children aged 8-12 years nested within two communities (one intervention and one comparison). Children will be recruited from their respective elementary schools. Components of the 2-year multi-level intervention include comic books (individual-level), multi-generational nutrition and PA classes (family-level), teacher-led PA breaks and media literacy education (school-level), family nights, a farmer's market and a community PA event (known as ciclovia) at the community-level. Children from the comparison community will receive two newsletters. Height and weight measures will be collected from children in both communities at three time points (baseline, 6-months, and 18-months). The Together We STRIDE study aims to promote healthier diet and increased PA to produce healthy weight among Hispanic children. The use of CBPR approach and the engagement of the community will springboard strategies for intervention' sustainability. Clinical Trials Registration Number: NCT02982759 Retrospectively registered. Copyright © 2018 Elsevier Inc. All rights reserved.

Analysis of spastic gait in cervical myelopathy: Linking compression ratio to spatiotemporal and pedobarographic parameters.

PubMed

Nagai, Taro; Takahashi, Yasuhito; Endo, Kenji; Ikegami, Ryo; Ueno, Ryuichi; Yamamoto, Kengo

2018-01-01

Gait dysfunction associated with spasticity and hyperreflexia is a primary symptom in patients with compression of cervical spinal cord. The objective of this study was to link maximum compression ratio (CR) to spatiotemporal/pedobarographic parameters. Quantitative gait analysis was performed by using a pedobarograph in 75 elderly males with a wide range of cervical compression severity. CR values were characterized on T1-weighted magnetic resonance imaging (MRI). Statistical significances in gait analysis parameters (speed, cadence, stride length, step with, and toe-out angle) were evaluated among different CR groups by the non-parametric Kruskal-Wallis test followed by the Mann-Whitney U test using Bonferroni correction. The Spearman test was performed to verify correlations between CR and gait parameters. The Kruskal-Wallis test revealed significant decline in gait speed and stride length and significant increase in toe-out angle with progression of cervical compression myelopathy. The post-hoc Mann-Whitney U test showed significant differences in these parameters between the control group (0.45

METABOLIC SYNDROME AND DAILY AMBULATION IN CHILDREN, ADOLESCENTS, AND YOUNG ADULTS

PubMed Central

Gardner, Andrew W.; Parker, Donald E.; Krishnan, Sowmya; Chalmers, Laura J.

2012-01-01

Purposes To compare daily ambulatory measures in children, adolescents, and young adults with and without metabolic syndrome, and to assess which metabolic syndrome components, demographic measures, and body composition measures are associated with daily ambulatory measures. Methods Two-hundred fifty subjects between the ages of 10 and 30 years were assessed on metabolic syndrome components, demographic and clinical measures, body fat percentage, and daily ambulatory strides, durations, and cadences during seven consecutive days. Forty-five of the 250 subjects had metabolic syndrome, as defined by the International Diabetes Federation. Results Subjects with metabolic syndrome ambulated at a slower daily average cadence than those without metabolic syndrome (13.6 ± 2.2 strides/min vs. 14.9 ± 3.2 strides/min; p=0.012), and they had slower cadences for continuous durations of 60 minutes (p=0.006), 30 minutes (p=0.005), 20 minutes (p=0.003), 5 minutes (p=0.002), and 1 minute (p=0.001). However, the total amount of time spent ambulating each day was not different (p=0.077). After adjustment for metabolic syndrome status, average cadence is linearly associated with body fat percentage (p<0.001) and fat mass (p<0.01). Group difference in average cadence was no longer significant after adjusting for body fat percentage (p=0.683) and fat mass (p=0.973). Conclusion Children, adolescents, and young adults with metabolic syndrome ambulate more slowly and take fewer strides throughout the day than those without metabolic syndrome, even though the total amount of time spent ambulating is not different. Furthermore, the detrimental influence of metabolic syndrome on ambulatory cadence is primarily a function of body fatness. PMID:22811038

Gait symmetry and regularity in transfemoral amputees assessed by trunk accelerations

PubMed Central

2010-01-01

Background The aim of this study was to evaluate a method based on a single accelerometer for the assessment of gait symmetry and regularity in subjects wearing lower limb prostheses. Methods Ten transfemoral amputees and ten healthy control subjects were studied. For the purpose of this study, subjects wore a triaxial accelerometer on their thorax, and foot insoles. Subjects were asked to walk straight ahead for 70 m at their natural speed, and at a lower and faster speed. Indices of step and stride regularity (Ad1 and Ad2, respectively) were obtained by the autocorrelation coefficients computed from the three acceleration components. Step and stride durations were calculated from the plantar pressure data and were used to compute two reference indices (SI1 and SI2) for step and stride regularity. Results Regression analysis showed that both Ad1 well correlates with SI1 (R2 up to 0.74), and Ad2 well correlates with SI2 (R2 up to 0.52). A ROC analysis showed that Ad1 and Ad2 has generally a good sensitivity and specificity in classifying amputee's walking trial, as having a normal or a pathologic step or stride regularity as defined by means of the reference indices SI1 and SI2. In particular, the antero-posterior component of Ad1 and the vertical component of Ad2 had a sensitivity of 90.6% and 87.2%, and a specificity of 92.3% and 81.8%, respectively. Conclusions The use of a simple accelerometer, whose components can be analyzed by the autocorrelation function method, is adequate for the assessment of gait symmetry and regularity in transfemoral amputees. PMID:20085653

Functional Role of the Front and Back Legs During a Track Start with Special Reference to an Inverted Pendulum Model in College Swimmers.

PubMed

Ikeda, Yusuke; Ichikawa, Hiroshi; Nara, Rio; Baba, Yasuhiro; Shimoyama, Yoshimitsu; Kubo, Yasuyuki

2016-10-01

This study investigated factors that determine the velocity of the center of mass (CM) and flight distance from a track start to devise effective technical and physical training methods. Nine male and 5 female competitive swimmers participated in this study. Kinematics and ground reaction forces of the front and back legs were recorded using a video camera and force plates. The track start was modeled as an inverted pendulum system including a compliant leg, connecting the CM and front edge of the starting block. The increase in the horizontal velocity of the CM immediately after the start signal was closely correlated with the rotational component of the inverted pendulum. This rotational component at hands-off was significantly correlated with the average vertical force of the back plate from the start signal to hands-off (r = .967, P < .001). The flight distance / height was significantly correlated with the average vertical force of the front plate from the back foot-off to front foot-off (r = .783, P < .01). The results indicate that the legs on the starting block in the track start play a different role in the behavior of the inverted pendulum.

Chiral Luttinger liquids and a generalized Luttinger's theorem in fractional quantum Hall edges via finite-entanglement scaling

NASA Astrophysics Data System (ADS)

Varjas, Daniel; Zaletel, Michael; Moore, Joel

2014-03-01

We use bosonic field theories and the infinite system density matrix renormalization group (iDMRG) method to study infinite strips of fractional quantum Hall (FQH) states starting from microscopic Hamiltonians. Finite-entanglement scaling allows us to accurately measure chiral central charge, edge mode exponents and momenta without finite-size errors. We analyze states in the first and second level of the standard hierarchy and compare our results to predictions of the chiral Luttinger liquid (χLL) theory. The results confirm the universality of scaling exponents in chiral edges and demonstrate that renormalization is subject to universal relations in the non-chiral case. We prove a generalized Luttinger's theorem involving all singularities in the momentum-resolved density, which naturally arises when mapping Landau levels on a cylinder to a fermion chain and deepens our understanding of non-Fermi liquids in 1D.

Chiral Luttinger liquids and a generalized Luttinger theorem in fractional quantum Hall edges via finite-entanglement scaling

NASA Astrophysics Data System (ADS)

Varjas, Dániel; Zaletel, Michael P.; Moore, Joel E.

2013-10-01

We use bosonic field theories and the infinite system density matrix renormalization group method to study infinite strips of fractional quantum Hall states starting from microscopic Hamiltonians. Finite-entanglement scaling allows us to accurately measure chiral central charge, edge-mode exponents, and momenta without finite-size errors. We analyze states in the first and second levels of the standard hierarchy and compare our results to predictions of the chiral Luttinger liquid theory. The results confirm the universality of scaling exponents in chiral edges and demonstrate that renormalization is subject to universal relations in the nonchiral case. We prove a generalized Luttinger theorem involving all singularities in the momentum-resolved density, which naturally arises when mapping Landau levels on a cylinder to a fermion chain and deepens our understanding of non-Fermi liquids in one dimension.

Joint detection of anatomical points on surface meshes and color images for visual registration of 3D dental models

NASA Astrophysics Data System (ADS)

Destrez, Raphaël.; Albouy-Kissi, Benjamin; Treuillet, Sylvie; Lucas, Yves

2015-04-01

Computer aided planning for orthodontic treatment requires knowing occlusion of separately scanned dental casts. A visual guided registration is conducted starting by extracting corresponding features in both photographs and 3D scans. To achieve this, dental neck and occlusion surface are firstly extracted by image segmentation and 3D curvature analysis. Then, an iterative registration process is conducted during which feature positions are refined, guided by previously found anatomic edges. The occlusal edge image detection is improved by an original algorithm which follows Canny's poorly detected edges using a priori knowledge of tooth shapes. Finally, the influence of feature extraction and position optimization is evaluated in terms of the quality of the induced registration. Best combination of feature detection and optimization leads to a positioning average error of 1.10 mm and 2.03°.

INS/EKF-based stride length, height and direction intent detection for walking assistance robots.

PubMed

Brescianini, Dario; Jung, Jun-Young; Jang, In-Hun; Park, Hyun Sub; Riener, Robert

2011-01-01

We propose an algorithm used to obtain the information on stride length, height difference, and direction based on user's intent during walking. For exoskeleton robots used to assist paraplegic patients' walking, this information is used to generate gait patterns by themselves in on-line. To obtain this information, we attach an inertial measurement unit(IMU) on crutches and apply an extended kalman filter-based error correction method to reduce the phenomena of drift due to bias of the IMU. The proposed method is verifed in real walking scenarios including walking, climbing up-stairs, and changing direction of walking with normal. © 2011 IEEE

Automated mapping of pharmacy orders from two electronic health record systems to RxNorm within the STRIDE clinical data warehouse.

PubMed

Hernandez, Penni; Podchiyska, Tanya; Weber, Susan; Ferris, Todd; Lowe, Henry

2009-11-14

The Stanford Translational Research Integrated Database Environment (STRIDE) clinical data warehouse integrates medication information from two Stanford hospitals that use different drug representation systems. To merge this pharmacy data into a single, standards-based model supporting research we developed an algorithm to map HL7 pharmacy orders to RxNorm concepts. A formal evaluation of this algorithm on 1.5 million pharmacy orders showed that the system could accurately assign pharmacy orders in over 96% of cases. This paper describes the algorithm and discusses some of the causes of failures in mapping to RxNorm.

Kinematic and kinetic comparison of barefoot and shod running in mid/forefoot and rearfoot strike runners.

PubMed

Thompson, M A; Lee, S S; Seegmiller, J; McGowan, C P

2015-05-01

Barefoot running has been associated with decreased stride length and switching from a rearfoot strike (RFS) pattern to a mid/forefoot strike (M/FFS) pattern. However, some individuals naturally contact the ground on their mid/forefoot, even when wearing cushioned running shoes. The purpose of this study was to determine if the mechanics of barefoot running by natural shod RFS runners differed from natural shod M/FFS runners. Twenty habitually shod runners (ten natural M/FFS and ten natural RFS) participated in this study. Three-dimensional motion analysis and ground reaction force data were captured as subjects ran at their preferred running speed in both barefoot and shod conditions. M/FFS experienced only a decrease in stride length when switching from shod to barefoot running. Whereas, when switching from shod to barefoot running, RFS individuals experienced a decrease in stride length, switched to a plantarflexed position at ground contact and saw reduced impact peak magnitudes. These results suggest that when barefoot, the RFS group ran similar to the M/FFS group running barefoot or shod. Copyright © 2015 Elsevier B.V. All rights reserved.

Can anti-gravity running improve performance to the same degree as over-ground running?

PubMed

Brennan, Christopher T; Jenkins, David G; Osborne, Mark A; Oyewale, Michael; Kelly, Vincent G

2018-03-11

This study examined the changes in running performance, maximal blood lactate concentrations and running kinematics between 85%BM anti-gravity (AG) running and normal over-ground (OG) running over an 8-week training period. Fifteen elite male developmental cricketers were assigned to either the AG or over-ground (CON) running group. The AG group (n = 7) ran twice a week on an AG treadmill and once per week over-ground. The CON group (n = 8) completed all sessions OG on grass. Both AG and OG training resulted in similar improvements in time trial and shuttle run performance. Maximal running performance showed moderate differences between the groups, however the AG condition resulted in less improvement. Large differences in maximal blood lactate concentrations existed with OG running resulting in greater improvements in blood lactate concentrations measured during maximal running. Moderate increases in stride length paired with moderate decreases in stride rate also resulted from AG training. The use of AG training to supplement regular OG training for performance should be used cautiously, as extended use over long periods of time could lead to altered stride mechanics and reduced blood lactate.

Tiger beetles pursue prey using a proportional control law with a delay of one half-stride.

PubMed

Haselsteiner, Andreas F; Gilbert, Cole; Wang, Z Jane

2014-06-06

Tiger beetles are fast diurnal predators capable of chasing prey under closed-loop visual guidance. We investigated this control system using statistical analyses of high-speed digital recordings of beetles chasing a moving prey dummy in a laboratory arena. Correlation analyses reveal that the beetle uses a proportional control law in which the angular position of the prey relative to the beetle's body axis drives the beetle's angular velocity with a delay of about 28 ms. The proportionality coefficient or system gain, 12 s(-1), is just below critical damping. Pursuit simulations using the derived control law predict angular orientation during pursuits with a residual error of about 7°. This is of the same order of magnitude as the oscillation imposed by the beetle's alternating tripod gait, which was not factored into the control law. The system delay of 28 ms equals a half-stride period, i.e. the time between the touch down of alternating tripods. Based on these results, we propose a physical interpretation of the observed control law: to turn towards its prey, the beetle on average exerts a sideways force proportional to the angular position of the prey measured a half-stride earlier.

Cinematographical analysis of javelin throwing techniques of decathletes.

PubMed Central

Kunz, H.; Kaufmann, D. A.

1983-01-01

Th purpose of this study was to analyse by correlational methods the biomechanical factors involved in achieving the maximal distance thrown in the javelin event. Twelve Swiss decathletes and two world class javelin specialists were filmed by a high speed (102 fps) 16 mm camera throwing a total of 20 trials. The co-ordinates of the resulting cyclograms were processed by a computer programme and the results submitted to correlational analysis. The highest correlation was 0.76 between velocity at release and distance thrown. Other negative correlations were found between distance thrown and angle of the javelin with the horizontal (0.52) and distance thrown and throwing hand to contralateral foot distance during the last strides (0.67). Javelin specialists, who had longer throws than decathletes (mean = 79.03 m versus 54.29 m), had a smaller difference between the angle of attack and angle of release. The results suggest that in order to attain maximal distance thrown the javelin thrower should achieve positive acceleration during the running approach, effective thrusting with th right leg on the penultimate stride and carry the javelin during the last strides at the optimal angle of release (32 to 36 degrees). Images p200-a p200-b PMID:6652405

Intelligent person identification system using stereo camera-based height and stride estimation

NASA Astrophysics Data System (ADS)

Ko, Jung-Hwan; Jang, Jae-Hun; Kim, Eun-Soo

2005-05-01

In this paper, a stereo camera-based intelligent person identification system is suggested. In the proposed method, face area of the moving target person is extracted from the left image of the input steros image pair by using a threshold value of YCbCr color model and by carrying out correlation between the face area segmented from this threshold value of YCbCr color model and the right input image, the location coordinates of the target face can be acquired, and then these values are used to control the pan/tilt system through the modified PID-based recursive controller. Also, by using the geometric parameters between the target face and the stereo camera system, the vertical distance between the target and stereo camera system can be calculated through a triangulation method. Using this calculated vertical distance and the angles of the pan and tilt, the target's real position data in the world space can be acquired and from them its height and stride values can be finally extracted. Some experiments with video images for 16 moving persons show that a person could be identified with these extracted height and stride parameters.

Using an electrohydraulic ankle foot orthosis to study modifications in feedforward control during locomotor adaptation to force fields applied in stance

PubMed Central

Noel, Martin; Fortin, Karine; Bouyer, Laurent J

2009-01-01

Background Adapting to external forces during walking has been proposed as a tool to improve locomotion after central nervous system injury. However, sensorimotor integration during walking varies according to the timing in the gait cycle, suggesting that adaptation may also depend on gait phases. In this study, an ElectroHydraulic AFO (EHO) was used to apply forces specifically during mid-stance and push-off to evaluate if feedforward movement control can be adapted in these 2 gait phases. Methods Eleven healthy subjects walked on a treadmill before (3 min), during (5 min) and after (5 min) exposure to 2 force fields applied by the EHO (mid-stance/push-off; ~10 Nm, towards dorsiflexion). To evaluate modifications in feedforward control, strides with no force field ('catch strides') were unexpectedly inserted during the force field walking period. Results When initially exposed to a mid-stance force field (FF20%), subjects showed a significant increase in ankle dorsiflexion velocity. Catches applied early into the FF20% were similar to baseline (P > 0.99). Subjects gradually adapted by returning ankle velocity to baseline over ~50 strides. Catches applied thereafter showed decreased ankle velocity where the force field was normally applied, indicating the presence of feedforward adaptation. When initially exposed to a push-off force field (FF50%), plantarflexion velocity was reduced in the zone of force field application. No adaptation occurred over the 5 min exposure. Catch strides kinematics remained similar to control at all times, suggesting no feedforward adaptation. As a control, force fields assisting plantarflexion (-3.5 to -9.5 Nm) were applied and increased ankle plantarflexion during push-off, confirming that the lack of kinematic changes during FF50% catch strides were not simply due to a large ankle impedance. Conclusion Together these results show that ankle exoskeletons such as the EHO can be used to study phase-specific adaptive control of the ankle during locomotion. Our data suggest that, for short duration exposure, a feedforward modification in torque output occurs during mid-stance but not during push-off. These findings are important for the design of novel rehabilitation methods, as they suggest that the ability to use resistive force fields for training may depend on targeted gait phases. PMID:19493356

Using an electrohydraulic ankle foot orthosis to study modifications in feedforward control during locomotor adaptation to force fields applied in stance.

PubMed

Noel, Martin; Fortin, Karine; Bouyer, Laurent J

2009-06-03

Adapting to external forces during walking has been proposed as a tool to improve locomotion after central nervous system injury. However, sensorimotor integration during walking varies according to the timing in the gait cycle, suggesting that adaptation may also depend on gait phases. In this study, an ElectroHydraulic AFO (EHO) was used to apply forces specifically during mid-stance and push-off to evaluate if feedforward movement control can be adapted in these 2 gait phases. Eleven healthy subjects walked on a treadmill before (3 min), during (5 min) and after (5 min) exposure to 2 force fields applied by the EHO (mid-stance/push-off; approximately 10 Nm, towards dorsiflexion). To evaluate modifications in feedforward control, strides with no force field ('catch strides') were unexpectedly inserted during the force field walking period. When initially exposed to a mid-stance force field (FF 20%), subjects showed a significant increase in ankle dorsiflexion velocity. Catches applied early into the FF 20% were similar to baseline (P > 0.99). Subjects gradually adapted by returning ankle velocity to baseline over approximately 50 strides. Catches applied thereafter showed decreased ankle velocity where the force field was normally applied, indicating the presence of feedforward adaptation. When initially exposed to a push-off force field (FF 50%), plantarflexion velocity was reduced in the zone of force field application. No adaptation occurred over the 5 min exposure. Catch strides kinematics remained similar to control at all times, suggesting no feedforward adaptation. As a control, force fields assisting plantarflexion (-3.5 to -9.5 Nm) were applied and increased ankle plantarflexion during push-off, confirming that the lack of kinematic changes during FF 50% catch strides were not simply due to a large ankle impedance. Together these results show that ankle exoskeletons such as the EHO can be used to study phase-specific adaptive control of the ankle during locomotion. Our data suggest that, for short duration exposure, a feedforward modification in torque output occurs during mid-stance but not during push-off. These findings are important for the design of novel rehabilitation methods, as they suggest that the ability to use resistive force fields for training may depend on targeted gait phases.

Scaling analysis of the non-Abelian quasiparticle tunneling in [Formula: see text] FQH states.

PubMed

Li, Qi; Jiang, Na; Wan, Xin; Hu, Zi-Xiang

2018-06-27

Quasiparticle tunneling between two counter propagating edges through point contacts could provide information on its statistics. Previous study of the short distance tunneling displays a scaling behavior, especially in the conformal limit with zero tunneling distance. The scaling exponents for the non-Abelian quasiparticle tunneling exhibit some non-trivial behaviors. In this work, we revisit the quasiparticle tunneling amplitudes and their scaling behavior in a full range of the tunneling distance by putting the electrons on the surface of a cylinder. The edge-edge distance can be smoothly tuned by varying the aspect ratio for a finite size cylinder. We analyze the scaling behavior of the quasiparticles for the Read-Rezayi [Formula: see text] states for [Formula: see text] and 4 both in the short and long tunneling distance region. The finite size scaling analysis automatically gives us a critical length scale where the anomalous correction appears. We demonstrate this length scale is related to the size of the quasiparticle at which the backscattering between two counter propagating edges starts to be significant.

Assessment of a 3-D boundary layer code to predict heat transfer and flow losses in a turbine

NASA Technical Reports Server (NTRS)

Anderson, O. L.

1984-01-01

Zonal concepts are utilized to delineate regions of application of three-dimensional boundary layer (DBL) theory. The zonal approach requires three distinct analyses. A modified version of the 3-DBL code named TABLET is used to analyze the boundary layer flow. This modified code solves the finite difference form of the compressible 3-DBL equations in a nonorthogonal surface coordinate system which includes coriolis forces produced by coordinate rotation. These equations are solved using an efficient, implicit, fully coupled finite difference procedure. The nonorthogonal surface coordinate system is calculated using a general analysis based on the transfinite mapping of Gordon which is valid for any arbitrary surface. Experimental data is used to determine the boundary layer edge conditions. The boundary layer edge conditions are determined by integrating the boundary layer edge equations, which are the Euler equations at the edge of the boundary layer, using the known experimental wall pressure distribution. Starting solutions along the inflow boundaries are estimated by solving the appropriate limiting form of the 3-DBL equations.

Properties of the spindle-to-cusp transition in extensional capsule dynamics

NASA Astrophysics Data System (ADS)

Dodson, W. R., III; Dimitrakopoulos, P.

2014-05-01

Our earlier letter (Dodson W. R. III and Dimitrakopoulos P., Phys. Rev. Lett., 101 (2008) 208102) revealed that a (strain-hardening) Skalak capsule in a planar extensional Stokes flow develops for stability reasons steady-state shapes whose edges from spindled become cusped with increasing flow rate owing to a transition of the edge tensions from tensile to compressive. A bifurcation in the steady-state shapes was also found (i.e. existence of both spindled and cusped edges for a range of high flow rates) by implementing different transient processes, owing to the different evolution of the membrane tensions. In this paper we show that the bifurcation range is wider at higher viscosity ratio (owing to the lower transient membrane tensions accompanied the slower capsule deformation starting from the quiescent capsule shape), while it contracts and eventually disappears as the viscosity ratio decreases. The spindle-to-cusp transition is shown to represent a self-similar finite-time singularity formation which for real capsules with very small but finite thickness is expected to be an apparent singularity, i.e. formation of very large (but finite) positive and negative edge curvatures.

An Edge-Based Method for the Incompressible Navier-Stokes Equations on Polygonal Meshes

NASA Astrophysics Data System (ADS)

Wright, Jeffrey A.; Smith, Richard W.

2001-05-01

A pressure-based method is presented for discretizing the unsteady incompressible Navier-Stokes equations using hybrid unstructured meshes. The edge-based data structure and assembly procedure adopted lead naturally to a strictly conservative discretization, which is valid for meshes composed of n-sided polygons. Particular attention is given to the construction of a pressure-velocity coupling procedure which is supported by edge data, resulting in a relatively simple numerical method that is consistent with the boundary and initial conditions required by the incompressible Navier-Stokes equations. Edge formulas are presented for assembling the momentum equations, which are based on an upwind-biased linear reconstruction of the velocity field. Similar formulas are presented for assembling the pressure equation. The method is demonstrated to be second-order accurate in space and time for two Navier-Stokes problems admitting an exact solution. Results for several other well-known problems are also presented, including lid-driven cavity flow, impulsively started cylinder flow, and unsteady vortex shedding from a circular cylinder. Although the method is by construction minimalist, it is shown to be accurate and robust for the problems considered.

Racing for an Early Edge

ERIC Educational Resources Information Center

McNeil, Michele

2009-01-01

States jockey for position as the U.S. Education Department readies billions of dollars in "Race to the Top" awards--the stimulus program's grand prize. Even before they've finished spending their first block of federal stimulus aid, states are getting a head start in a national "race to the top" for better public education,…

Extending the Classroom: Transforming a School through Experiential Education

ERIC Educational Resources Information Center

Mierke, Sara

2013-01-01

Even the most traditional independent schools have a starting point for expanding or integrating experiential education. Hawken was founded in 1915 as an alternative to existing traditional private education options for boys in Cleveland. James A. Hawken, a progressive New York educator, founded the school in a small house on the edge of…

Relevancy in Problem Solving: A Computational Framework

ERIC Educational Resources Information Center

Kwisthout, Johan

2012-01-01

When computer scientists discuss the computational complexity of, for example, finding the shortest path from building A to building B in some town or city, their starting point typically is a formal description of the problem at hand, e.g., a graph with weights on every edge where buildings correspond to vertices, routes between buildings to…

Patterns in the Waves

NASA Astrophysics Data System (ADS)

Coco, G.; Guza, R. T.; Garnier, R.; Lomonaco, P.; Lopez De San Roman Blanco, B.; Dalrymple, R. A.; Xu, M.

2014-12-01

Edge waves, gravity waves trapped close to the shoreline by refraction, can in some cases form a standing wave pattern with alongshore periodic sequence of high and low runup. Nonlinear mechanisms for generation of edge waves by monochromatic waves incident on a planar beach from deep water have been elaborated theoretically and in the lab. Edge waves have been long considered a potential source for alongshore periodic morphological patterns in the swash (e.g., beach cusps), and edge-wave based predictions of cusp spacing compare qualitatively well with many field observations. We will discuss the extension of lab observations and numerical modeling to include incident waves with significant frequency and directional bandwidth. Laboratory experiments were performed at the Cantabria Coastal and Ocean Basin. The large rectangular basin (25 m cross-shore by 32 m alongshore) was heavily instrumented, had reflective sidewalls, and a steep concrete beach (slope 1:5) with a constant depth (1m) section between the wavemaker and beach. With monochromatic, normally incident waves we observed the expected, previously described subharmonic observations. Edge wave vertical heights at the shoreline reached 80cm, and edge wave uprushes exceeded the sloping beach freeboard. When frequency and frequency-directional spread are increased, the excited edge wave character changes substantially. In some cases, subharmonic excitation is suppressed completely. In other cases, edge waves are excited intermittently and unpredictably. The spatially and temporally steady forcing required for strong, persistent subharmonic instability is lacking with even modestly spread (direction and frequency) incident waves. An SPH numerical model is capable of reproducing aspects of the observations. It seems unlikely to us that subhamonic edge waves alone are responsible for most cusp formation on natural beaches. The steady incident wave forcing needed to initiate subharmonic growth, and to maintain subharmonics long enough to build cups, are abundantly present with an incident plane wave, but lacking in many natural settings. Although subharmonic edge waves can potentially start the initial spacing, positive feedback between flow and morphology are likely critical to cusp growth.

Heat treatment effect on the electronic and magnetic structures of nanographene sheets investigated through electron spectroscopy and conductance measurements.

PubMed

Takashiro, Jun-ichi; Kudo, Yasuhiko; Kaneko, Satoshi; Takai, Kazuyuki; Ishii, Takafumi; Kyotani, Takashi; Enoki, Toshiaki; Kiguchi, Manabu

2014-04-28

The heat treatment effect on the electronic and magnetic structures of a disordered network of nanographene sheets has been investigated by in situ measurements of X-ray photoemission spectroscopy, near-edge X-ray absorption fine structure (NEXAFS), and electrical conductance, together with temperature-programmed desorption measurements. Oxygen-containing functional groups bonded to nanographene edges in the pristine sample are almost completely decomposed under heat treatment up to 1300-1500 K, resulting in the formation of edges primarily terminated by hydrogen. The removal of the oxygen-containing groups enhances the conductance owing to the decrease in the electron transport barriers between nanographene sheets. Heat treatment above 1500 K removes also the hydrogen atoms from the edges, promoting the successive fusion of nanographene sheets at the expense of edges. The decrease in the π* peak width in NEXAFS indicates the progress of the fusion reaction, that is, the extension of the π-conjugation, which agrees with the increase in the orbital susceptibility previously reported. The fusion leads to the formation of local π/sp(2) bridges between nanographene sheets and brings about an insulator-to-metal transition at 1500-1600 K, at which the bridge network becomes infinite. As for the magnetism, the intensity of the edge state peak in NEXAFS, which corresponds to the number of the spin-polarized edge states, decreases above 1500 K, though the effective edge-state spin density per edge state starts decreasing at approximately 200 K lower than the temperature of the edge state peak change. This disagreement indicates the development of antiferromagnetic short range ordering as a precursor of a spin glass state near the insulator-metal transition, at which the random network of inter-nanographene-sheet exchange interactions strengthened with the formation of the π/sp(2) bridges becomes infinite.

Epilepsy

MedlinePlus

... made great strides in detecting patterns of abnormal electrical activity in the brain that cause epileptic seizures. A technology to measure brain activity, called electroencephalography (EEG), became ...

Image analysis by integration of disparate information

NASA Technical Reports Server (NTRS)

Lemoigne, Jacqueline

1993-01-01

Image analysis often starts with some preliminary segmentation which provides a representation of the scene needed for further interpretation. Segmentation can be performed in several ways, which are categorized as pixel based, edge-based, and region-based. Each of these approaches are affected differently by various factors, and the final result may be improved by integrating several or all of these methods, thus taking advantage of their complementary nature. In this paper, we propose an approach that integrates pixel-based and edge-based results by utilizing an iterative relaxation technique. This approach has been implemented on a massively parallel computer and tested on some remotely sensed imagery from the Landsat-Thematic Mapper (TM) sensor.

Encountering Ehrenberg: tracing the development of psychoanalytic therapy at the intimate edge.

PubMed

Laidlaw, Christine; Heusser, Shelley

2014-01-01

This article illustrates the thinking-through processes and clinical applications of D.B. Ehrenberg's ideas within the therapeutic situation. During the last four decades, Ehrenberg has articulated that the psychoanalytic relationship is at its most compelling when it evolves at "the intimate edge" of the therapist's self and that of the patient. She invites us to explore and process the relational dynamics of the therapeutic dyad within the consulting room. In tribute to Ehrenberg's work, we reflect on two individuals closed up in their self-reliance, who start to break open to their desires for intimacy when their therapist opens up his own self within the uniquely meaningful space co-created in the analytic therapy.

Acoustic and Perceptual Effects of Left-Right Laryngeal Asymmetries Based on Computational Modeling

ERIC Educational Resources Information Center

Samlan, Robin A.; Story, Brad H.; Lotto, Andrew J.; Bunton, Kate

2014-01-01

Purpose: Computational modeling was used to examine the consequences of 5 different laryngeal asymmetries on acoustic and perceptual measures of vocal function. Method: A kinematic vocal fold model was used to impose 5 laryngeal asymmetries: adduction, edge bulging, nodal point ratio, amplitude of vibration, and starting phase. Thirty /a/ and /?/…

Experiment with Holistic Rural Development in Northeast India: Early Results and Challenges

ERIC Educational Resources Information Center

Sarma, Alaka; Mukhtar, Mazin

2017-01-01

Akshar Forum, an experimental livelihood school in the semi-rural village of Pamohi, Assam, in Northeast India, tests cutting-edge methods in education in the context of underserved communities and rural development programs. Started in 2015, the school links 42 children and their parents to the vast knowledge resources of the Internet to teach…

Internet2 and Libraries: Serving Your Communities at the Speed of Light

ERIC Educational Resources Information Center

Werle, James; Fox, Louis

2007-01-01

Formed in 1996, Internet2 is a not-for-profit advanced network consortium led by the U.S. research and higher education community. Its goals are to provide leading-edge network capabilities and to facilitate the development, deployment, and use of revolutionary Internet technologies. Starting with 34 universities, Internet2 has grown to more than…

Harlem. ArtsEdge Curricula, Lessons and Activities.

ERIC Educational Resources Information Center

John F. Kennedy Center for the Performing Arts, Washington, DC.

This curriculum unit for Grades 3-4 (adaptable for higher or lower grades) introduces students to Harlem, starting with black migration from Africa and from the American South to the North, to the Harlem Renaissance (including jazz musicians, visual artists, writers, and poets), and on to aspects of daily Harlem life (then and now), such as family…

The motivation for very early intervention for infants at high risk for autism spectrum disorders.

PubMed

Webb, Sara Jane; Jones, Emily J H; Kelly, Jean; Dawson, Geraldine

2014-02-01

The first Autism Research Matrix (IACC, 2003) listed the identification of behavioural and biological markers of risk for autism as a top priority. This emphasis was based on the hypothesis that intervention with infants at-risk, at an early age when the brain is developing and before core autism symptoms have emerged, could significantly alter the developmental trajectory of children at risk for the disorder and impact long-range outcome. Research has provided support for specific models of early autism intervention (e.g., Early Start Denver Model) for improving outcomes in young children with autism, based on both behavioural and brain activity measures. Although great strides have been made in ability to identify risk markers for autism in younger infant/toddler samples, how and when to intervene during the prodromal state remains a critical question. Emerging evidence suggests that abnormal brain circuitry in autism precedes altered social behaviours; thus, an intervention designed to promote early social engagement and reciprocity potentially could steer brain development back toward the normal trajectory and remit or reduce the expression of symptoms.

Restoration of gait by functional electrical stimulation in paraplegic patients: a modified programme of treatment.

PubMed

Malezic, M; Hesse, S

1995-03-01

Restoration of standing and of gait by functional electrical stimulation in clinically complete paraplegic patients was modified in the course of treatment and in the stimulation parameters. By substituting an initial cyclic muscle strengthening with an active stimulated standing, four patients with T3-11 lesions started walking with electrical stimulation in 10-17 days. They walked without ankle-foot orthoses. With a satisfactory stride length of 0.75-0.97 m, their gait velocity ranged from very slow to that of a leisurely healthy gait. Already established stimulation of the quadriceps muscles for standing and of the peroneal nerves for lower limb flexion during the swing phase of gait was applied. Diminished limb flexion after several weeks was restored by an increase of the stimulation frequency of the peroneal nerve from 20 to 60 Hz. EMG and kinesiological measurements displayed an improved direct response of the ankle as well as of the reflex mediated hip, knee and ankle flexion response. At the same time stimulation frequency was reduced to 16 Hz for the quadriceps muscles in order to reduce fatigue.

New Horizons and New Strategies in Arms Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, J. editor

In the last ten years, since the break-up of the Soviet Union, remarkable progress in arms control and disarmament has occurred. The Nuclear Non-Proliferation Treaty (NPT), the completion of the Comprehensive Test Ban Treaty (CTBT), and the Chemical Weapons Treaty (CWC) are indicative of the great strides made in the non- proliferation arena. Simultaneously, the Intermediate Nuclear Forces Treaty (INF), the Conventional Forces Treaty in Europe (CFE), and the Strategic Arms Reduction Treaties (START), all associated with US-Soviet Union (now Russia) relations have assisted in redefining European relations and the security landscape. Finally, it now appears that progress is inmore » the offing in developing enhanced compliance measures for the Biological and Toxin Weapons Convention (BTWC). In sum, all of these achievements have set the stage for the next round of arms control activities, which may lead to a much broader, and perhaps more diffused multilateral agenda. In this new and somewhat unpredictable international setting, arms control and disarmament issues will require solutions that are both more creative and innovative than heretofore.« less

NASA's Kilopower Reactor Development and the Path to Higher Power Missions

NASA Technical Reports Server (NTRS)

Gibson, Marc A.; Oleson, Steven R.; Poston, David I.; McClure, Patrick

2017-01-01

The development of NASAs Kilopower fission reactor is taking large strides toward flight development with several successful tests completed during its technology demonstration trials. The Kilopower reactors are designed to provide 1-10 kW of electrical power to a spacecraft which could be used for additional science instruments as well as the ability to power electric propulsion systems. Power rich nuclear missions have been excluded from NASA proposals because of the lack of radioisotope fuel and the absence of a flight qualified fission system. NASA has partnered with the Department of Energy's National Nuclear Security Administration to develop the Kilopower reactor using existing facilities and infrastructure to determine if the design is ready for flight development. The 3-year Kilopower project started in 2015 with a challenging goal of building and testing a full-scale flight prototypic nuclear reactor by the end of 2017. As the date approaches, the engineering team shares information on the progress of the technology as well as the enabling capabilities it provides for science and human exploration.

NASA's Kilopower Reactor Development and the Path to Higher Power Missions

NASA Technical Reports Server (NTRS)

Gibson, Marc A.; Oleson, Steven R.; Poston, Dave I.; McClure, Patrick

2017-01-01

The development of NASA's Kilopower fission reactor is taking large strides toward flight development with several successful tests completed during its technology demonstration trials. The Kilopower reactors are designed to provide 1-10 kW of electrical power to a spacecraft which could be used for additional science instruments as well as the ability to power electric propulsion systems. Power rich nuclear missions have been excluded from NASA proposals because of the lack of radioisotope fuel and the absence of a flight qualified fission system. NASA has partnered with the Department of Energy's National Nuclear Security Administration to develop the Kilopower reactor using existing facilities and infrastructure to determine if the design is ready for flight development. The 3-year Kilopower project started in 2015 with a challenging goal of building and testing a full-scale flight prototypic nuclear reactor by the end of 2017. As the date approaches, the engineering team shares information on the progress of the technology as well as the enabling capabilities it provides for science and human exploration.

Effects of a capacitive-resistive electric transfer therapy on physiological and biomechanical parameters in recreational runners: A randomized controlled crossover trial.

PubMed

Duñabeitia, Iratxe; Arrieta, Haritz; Torres-Unda, Jon; Gil, Javier; Santos-Concejero, Jordan; Gil, Susana M; Irazusta, Jon; Bidaurrazaga-Letona, Iraia

2018-05-26

This study compared the effects of a capacitive-resistive electric transfer therapy (Tecar) and passive rest on physiological and biomechanical parameters in recreational runners when performed shortly after an exhausting training session. Randomized controlled crossover trial. University biomechanical research laboratory. Fourteen trained male runners MAIN OUTCOME MEASURES: Physiological (running economy, oxygen uptake, respiratory exchange ratio, ventilation, heart rate, blood lactate concentration) and biomechanical (step length; stride angle, height, frequency, and contact time; swing time; contact phase; support phase; push-off phase) parameters were measured during two incremental treadmill running tests performed two days apart after an exhaustive training session. When running at 14 km/h and 16 km/h, the Tecar treatment group presented greater increases in stride length (p < 0.001), angle (p < 0.05) and height (p < 0.001) between the first and second tests than the control group and, accordingly, greater decreases in stride frequency (p < 0.05). Physiological parameters were similar between groups. The present study suggests that a Tecar therapy intervention enhances biomechanical parameters in recreational runners after an exhaustive training session more than passive rest, generating a more efficient running pattern without affecting selected physiological parameters. Copyright © 2018 Elsevier Ltd. All rights reserved.

Gait Parameter Adjustments for Walking on a Treadmill at Preferred, Slower, and Faster Speeds in Older Adults with Down Syndrome

PubMed Central

Smith, Beth A.; Kubo, Masayoshi; Ulrich, Beverly D.

2012-01-01

The combined effects of ligamentous laxity, hypotonia, and decrements associated with aging lead to stability-enhancing foot placement adaptations during routine overground walking at a younger age in adults with Down syndrome (DS) compared to their peers with typical development (TD). Our purpose here was to examine real-time adaptations in older adults with DS by testing their responses to walking on a treadmill at their preferred speed and at speeds slower and faster than preferred. We found that older adults with DS were able to adapt their gait to slower and faster than preferred treadmill speeds; however, they maintained their stability-enhancing foot placements at all speeds compared to their peers with TD. All adults adapted their gait patterns similarly in response to faster and slower than preferred treadmill-walking speeds. They increased stride frequency and stride length, maintained step width, and decreased percent stance as treadmill speed increased. Older adults with DS, however, adjusted their stride frequencies significantly less than their peers with TD. Our results show that older adults with DS have the capacity to adapt their gait parameters in response to different walking speeds while also supporting the need for intervention to increase gait stability. PMID:22693497

Biomechanics of youth windmill softball pitching.

PubMed

Werner, Sherry L; Guido, John A; McNeice, Ryan P; Richardson, Jasper L; Delude, Neil A; Stewart, Gregory W

2005-04-01

Limited research attention has been paid to the potentially harmful windmill softball pitch. No information is available regarding lower extremity kinetics in softball pitching. The stresses on the throwing arm of youth windmill pitchers are clinically significant and similar to those found for college softball pitchers. Descriptive laboratory study. Three-dimensional, high-speed (240-Hz) video and stride foot force plate (1200 Hz) data were collected on fastballs from 53 youth softball pitchers. Kinematic parameters related to pitching mechanics and resultant kinetics on the throwing-arm elbow and shoulder joints were calculated. Kinetic parameters were compared to those reported for baseball pitchers. Elbow and shoulder joint loads were similar to those found for baseball pitchers and college softball pitchers. Shoulder distraction stress averaged 94% body weight for the youth pitchers. Stride foot ground reaction force patterns were not similar to those reported for baseball pitchers. Vertical and braking force components under the stride foot were in excess of body weight. Excessive distraction stress and joint torques at the throwing-arm elbow and shoulder are similar to those found in baseball pitchers, which suggests that windmill softball pitchers are at risk for overuse injuries. Normative information regarding upper and lower extremity kinematics and kinetics for 12- to 19-year-old softball pitchers has been established.

Effect of stride frequency on metabolic costs and rating of perceived exertion during walking in water.

PubMed

Masumoto, Kenji; Nishizaki, Yoshiko; Hamada, Ayako

2013-06-01

We investigated the effect of stride frequency (SF) on metabolic costs and rating of perceived exertion (RPE) during walking in water and on dry land. Eleven male subjects walked on a treadmill on dry land and on an underwater treadmill at their preferred SF (PSF) and walked at an SF which was lower and higher than the PSF (i.e., PSF ± 5, 10, and 15 strides min(-1)). Walking speed was kept constant at each subject's preferred walking speed in water and on dry land. Oxygen uptake, heart rate, RPE, PSF and preferred walking speeds were measured. Metabolic costs and RPE were significantly higher when walking at low and high SF conditions than when walking at the PSF condition both in water and on dry land (P<0.05). Additionally, the high SF condition produced significantly higher metabolic costs and RPE than the equivalent low SF condition during walking in water (P<0.01). Furthermore, metabolic costs, RPE, PSF, and the preferred walking speed were significantly lower in water than on dry land when walking at the PSF (P<0.05). These observations indicate that a change in SF influences metabolic costs and RPE during walking in water. Copyright © 2012 Elsevier B.V. All rights reserved.

Tiger beetles pursue prey using a proportional control law with a delay of one half-stride

PubMed Central

Haselsteiner, Andreas F.; Gilbert, Cole; Wang, Z. Jane

2014-01-01

Tiger beetles are fast diurnal predators capable of chasing prey under closed-loop visual guidance. We investigated this control system using statistical analyses of high-speed digital recordings of beetles chasing a moving prey dummy in a laboratory arena. Correlation analyses reveal that the beetle uses a proportional control law in which the angular position of the prey relative to the beetle's body axis drives the beetle's angular velocity with a delay of about 28 ms. The proportionality coefficient or system gain, 12 s−1, is just below critical damping. Pursuit simulations using the derived control law predict angular orientation during pursuits with a residual error of about 7°. This is of the same order of magnitude as the oscillation imposed by the beetle's alternating tripod gait, which was not factored into the control law. The system delay of 28 ms equals a half-stride period, i.e. the time between the touch down of alternating tripods. Based on these results, we propose a physical interpretation of the observed control law: to turn towards its prey, the beetle on average exerts a sideways force proportional to the angular position of the prey measured a half-stride earlier. PMID:24718454

Spatiotemporal Gait Characteristics Associated with Cognitive Impairment: A Multicenter Cross-Sectional Study, the Intercontinental "Gait, cOgnitiOn & Decline" Initiative.

PubMed

Beauchet, Olivier; Blumen, Helena M; Callisaya, Michele L; De Cock, Anne-Marie; Kressig, Reto W; Srikanth, Velandai; Steinmetz, Jean-Paul; Verghese, Joe; Allali, Gilles

2018-01-23

The study aims to determine the spatiotemporal gait parameters and/or their combination(s) that best differentiate between cognitively healthy individuals (CHI), patients with mild cognitive impairment (MCI) and those with mild and moderate dementia, regardless of the etiology of cognitive impairment. A total of 2099 participants (1015 CHI, 478 patients with MCI, 331 patients with mild dementia and 275 with moderate dementia) were selected from the intercontinental "Gait, cOgnitiOn & Decline" (GOOD) initiative, which merged different databases from seven cross-sectional studies. Mean values and coefficients of variation (CoV) of spatiotemporal gait parameters were recorded during usual walking with the GAITRite® system. The severity of cognitive impairment was associated with worse performance on all gait parameters. Stride velocity had the strongest association with cognitive impairment, regardless of cognitive status. High mean value and CoV of stride length characterized moderate dementia, whereas increased CoV of stride time was specific to MCI status. The findings support the existence of specific cognitive impairment-related gait disturbances with differences related to stages of cognitive impairment, which may be used to screen individuals with cognitive impairment. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Fetlock joint kinematics differ with age in Thoroughbred [was thoroughbred] racehorses.

PubMed

Butcher, Michael T; Ashley-Ross, M A

2002-05-01

Fetlock joint kinematics during galloping in 2-, 3-, 4-, and 5-year-old Thoroughbreds in race training were quantified to determine if differences due to age could account for the observation that 2-year old Thoroughbred racehorses incur a high number of injuries to the bones and soft tissues in the distal forelimbs during training and at the outset of racing. Twelve Thoroughbred racehorses were videotaped in the sagittal plane at 250 frames/s during their daily galloping workout on a 7/8 mile sand-surface training track. Four galloping strides were recorded for each horse and subsequently digitized to determine fetlock joint angles of the leading forelimb during the limb support period of a stride. Four kinematic variables were measured from each stride's angular profile: angle of fetlock joint dorsi-flexion at mid-stance, negative angular velocity, positive angular velocity and time from hoof impact to mid-stance phase of limb support. The 2-year old Thoroughbreds had significantly quicker rates of dorsi-flexion of their fetlock joints than 3- (p=0.01), 4- (p=0.01), and 5-year old (p<0.01) Thoroughbreds following impact of the leading forelimb during moderate galloping (avg. 14 m/s). Higher rates of dorsi-flexion in young Thoroughbreds may reflect immaturity (lack of stiffness) of the suspensory apparatus tissues.

Rhythmic auditory stimulation improves gait more than NDT/Bobath training in near-ambulatory patients early poststroke: a single-blind, randomized trial.

PubMed

Thaut, M H; Leins, A K; Rice, R R; Argstatter, H; Kenyon, G P; McIntosh, G C; Bolay, H V; Fetter, M

2007-01-01

The effectiveness of 2 different types of gait training in stroke rehabilitation, rhythmic auditory stimulation (RAS) versus neurodevelopmental therapy (NDT)/Bobath- based training, was compared in 2 groups of hemiparetic stroke patients over a 3-week period of daily training (RAS group, n = 43; NDT/Bobath group =35). Mean entry date into the study was 21.3 days poststroke for the RAS group and 22.3 days for the control group. Patients entered the study as soon as they were able to complete 5 stride cycles with handheld assistance. Patients were closely equated by age, gender, and lesion site. Motor function in both groups was pre-assessed by the Barthel Index and the Fugl-Meyer Scales. Pre- to posttest measures showed a significant improvement in the RAS group for velocity (P = .006), stride length (P = .0001), cadence (P = .0001) and symmetry (P = .0049) over the NDT/Bobath group. Effect sizes for RAS over NDT/Bobath training were 13.1 m/min for velocity, 0.18 m for stride length, and 19 steps/min for cadence. The data show that after 3 weeks of gait training, RAS is an effective therapeutic method to enhance gait training in hemiparetic stroke rehabilitation. Gains were significantly higher for RAS compared to NDT/Bobath training.

Using Plantar Electrical Stimulation to Improve Postural Balance and Plantar Sensation Among Patients With Diabetic Peripheral Neuropathy: A Randomized Double Blinded Study

PubMed Central

Najafi, Bijan; Talal, Talal K.; Grewal, Gurtej Singh; Menzies, Robert; Armstrong, David G.; Lavery, Lawrence A.

2017-01-01

Objective: People with diabetic peripheral neuropathy (DPN) often exhibit deteriorations in motor-performance mainly due to lack of plantar-sensation. The study explored effectiveness of plantar electrical-stimulation therapy to enhance motor-performance among people with DPN. Design and methods: Using a double-blinded model, 28 volunteers with DPN (age: 57.8 ± 10.2 years) were recruited and randomized to either intervention (IG: n = 17) or control (CG: n = 11) group. Both groups received identical plantar-stimulation devices for six weeks of daily use at home; however, only the IG devices were set to deliver stimulation. Balance (ankle, hip, and center of mass [COM] sway) and gait (stride velocity [SV], stride time [ST], stride length [SL], and cadence) were measured using validated wearable sensors. Outcomes were assessed at baseline and at six-week. Clinical assessment including vascular as measured by ankle-brachial-index (ABI) and plantar-sensation as quantified by vibratory plantar threshold (VPT) were also measured at baseline and six weeks. Results: No difference were observed between groups for baseline characteristics (P > .050). Posttherapy, ankle and COM sway with eyes open were significantly improved (P < .05, Cohen’s effect size d = 0.67-0.76) in the IG with no noticeable changes in CG. All gait parameters were significantly improved in the IG with highest effect size observed for cadence (d = 1.35, P = .000). Results revealed improvement in VPT (P = .004, d = 1.15) with significant correlation with stride velocity improvement (r = .56, P = .037). ABI was improved in the IG in particulate among those with ABI>1.20 (P = .041, d = 0.99) Conclusion: This study suggests that daily home use of plantar electrical-stimulation may be a practical means to enhance motor-performance and plantar-sensation in people with DPN. PMID:28627217

Entrainment to a real time fractal visual stimulus modulates fractal gait dynamics.

PubMed

Rhea, Christopher K; Kiefer, Adam W; D'Andrea, Susan E; Warren, William H; Aaron, Roy K

2014-08-01

Fractal patterns characterize healthy biological systems and are considered to reflect the ability of the system to adapt to varying environmental conditions. Previous research has shown that fractal patterns in gait are altered following natural aging or disease, and this has potential negative consequences for gait adaptability that can lead to increased risk of injury. However, the flexibility of a healthy neurological system to exhibit different fractal patterns in gait has yet to be explored, and this is a necessary step toward understanding human locomotor control. Fifteen participants walked for 15min on a treadmill, either in the absence of a visual stimulus or while they attempted to couple the timing of their gait with a visual metronome that exhibited a persistent fractal pattern (contained long-range correlations) or a random pattern (contained no long-range correlations). The stride-to-stride intervals of the participants were recorded via analog foot pressure switches and submitted to detrended fluctuation analysis (DFA) to determine if the fractal patterns during the visual metronome conditions differed from the baseline (no metronome) condition. DFA α in the baseline condition was 0.77±0.09. The fractal patterns in the stride-to-stride intervals were significantly altered when walking to the fractal metronome (DFA α=0.87±0.06) and to the random metronome (DFA α=0.61±0.10) (both p<.05 when compared to the baseline condition), indicating that a global change in gait dynamics was observed. A variety of strategies were identified at the local level with a cross-correlation analysis, indicating that local behavior did not account for the consistent global changes. Collectively, the results show that a gait dynamics can be shifted in a prescribed manner using a visual stimulus and the shift appears to be a global phenomenon. Copyright © 2014 Elsevier B.V. All rights reserved.

The use of body weight support on ground level: an alternative strategy for gait training of individuals with stroke.

PubMed

Sousa, Catarina O; Barela, José A; Prado-Medeiros, Christiane L; Salvini, Tania F; Barela, Ana M F

2009-12-01

Body weight support (BWS) systems on treadmill have been proposed as a strategy for gait training of subjects with stroke. Considering that ground level is the most common locomotion surface and that there is little information about individuals with stroke walking with BWS on ground level, it is important to investigate the use of BWS on ground level in these individuals as a possible alternative strategy for gait training. Thirteen individuals with chronic stroke (four women and nine men; mean age 54.46 years) were videotaped walking on ground level in three experimental conditions: with no harness, with harness bearing full body weight, and with harness bearing 30% of full body weight. Measurements were recorded for mean walking speed, cadence, stride length, stride speed, durations of initial and terminal double stance, single limb support, swing period, and range of motion of ankle, knee, and hip joints; and foot, shank, thigh, and trunk segments. The use of BWS system leads to changes in stride length and speed, but not in stance and swing period duration. Only the hip joint was influenced by the BWS system in the 30% BWS condition. Shank and thigh segments presented less range of motion in the 30% BWS condition than in the other conditions, and the trunk was held straighter in the 30% BWS condition than in the other conditions. Individuals with stroke using BWS system on ground level walked slower and with shorter stride length than with no harness. BWS also led to reduction of hip, shank, and thigh range of motion. However, this system did not change walking temporal organization and body side asymmetry of individuals with stroke. On the other hand, the BWS system enabled individuals with chronic stroke to walk safely and without physical assistance. In interventions, the physical therapist can watch and correct gait pattern in patients' performance without the need to provide physical assistance.

Objective assessment of gait in xylazine-induced ataxic horses.

PubMed

Nout-Lomas, Y S; Page, K M; Kang, H G; Aanstoos, M E; Greene, H M

2017-05-01

There is poor agreement between observers of equine neurological gait abnormalities using the modified Mayhew grading scale. To stimulate a dose-dependent ataxia in horses through xylazine administration and identify quantifiable relevant gait parameters. Balanced, randomised, 2-way crossover design. Eight horses were assessed before and after administration of xylazine (low dose and high dose). Gait analyses performed before and after xylazine administration included: 1) kinematic data collected on an equine high-speed treadmill (flat and 10% decline) and from accelerometers placed on head and sacrum; and 2) kinetic data collected on a force plate. All horses developed dose-dependent ataxia. Horses developed a dose-dependent increased stride time, stride length, and time of contact (P<0.0001), and a decreased stride frequency (P<0.0002) after administration of xylazine. Although pelvic acceleration increased in the mediolateral direction (P<0.05) in horses walked on the treadmill, this movement decreased when walking over ground after administration of xylazine (P<0.05). Furthermore, centre of pressure and path length indices changed significantly in horses following administration of xylazine (P<0.05). This study examined one breed of horse (Arabian), all of similar height and weight. Accelerometers were attached to skin, not bone; no correction was made for artefacts from skin displacement. The sedative drug effect is of certain duration, limiting the data collection period. Administration of xylazine induced a dose-dependent ataxia in horses and resulted in significant changes of gait parameters, pelvic accelerations, and stabilographic variables, some of which changed in a dose-dependent fashion. Some of the altered gait parameters in this model were probably a result of overall slowing down of the stride cycle secondary to the sedative effect. Continued efforts to discover and evaluate quantifiable gait parameters that are susceptible to change following development of clinical neurological disease in horses is warranted. © 2016 EVJ Ltd.

Changes in gait while backward counting in demented older adults with frontal lobe dysfunction.

PubMed

Allali, Gilles; Kressig, Reto W; Assal, Frédéric; Herrmann, François R; Dubost, Véronique; Beauchet, Olivier

2007-10-01

Gait disorders caused by dementia have been associated with frontal lobe dysfunction. Dual-tasking is used to explore the involvement of cortical level in gait control. It has been shown that dual-task induced gait changes that could be related to (1) the efficiency of executive function, (2) the level of difficulty involved in the walking-associated task, or (3) the articulo-motor components comprised in the walking-associated task. A better understanding of dual-task related changes in demented subjects with frontal lobe dysfunction could help us to clarify the role of the frontal lobe in motor gait control. To assess and compare the effects of two mental arithmetic tasks involving similar articulo-motor components but different level of difficulty on the mean values and coefficient of variation (CV) of stride time among demented older adults with impaired executive function. The mean values and coefficients of variation of stride time were measured using a GAITRite-System among 16 demented older adults with impaired executive function while walking with and without forward counting (FC) and backward counting (BC). The mean values and CV of stride time were significantly higher under both dual-task conditions than during a simple walking task (p<0.05). The change in CV of stride time during BC was significantly higher when compared with the change during FC (p=0.015), whereas the change in mean value was not significant (p=0.056). There was no difference between the dual-task and single task condition as far the number of enumerated figures were concerned (p=0.678 for FC and p=0.069 for BC), but significantly fewer figures were enumerated while BC compared with FC (p<0.001). BC provoked more changes in gait parameters than FC with major modification in gait variability related to an inappropriate focusing of attention. These findings suggest that the CV may be a suitable criterion for the assessment of gait control.

Effects of form-focused training on running biomechanics: A pilot randomized trial in untrained individuals

PubMed Central

Kumar, Deepak; McDermott, Kelly; Feng, Haojun; Goldman, Veronica; Luke, Anthony; Souza, Richard B; Hecht, Frederick M

2015-01-01

Objective To investigate the changes in running biomechanics after training in Form-Focused running using ChiRunning vs. Not-Form focused training and Self-Directed training in untrained individuals. Design Pilot study - Randomized controlled trial. Setting Research Institution with Tertiary Care Medical Center. Participants Seventeen subjects (9 males, 8 females) with pre-hypertension. Methods Twenty-two participants were randomized to three study arms but 17 completed the study. The study arms were: 1) group-based Form-Focused running using ChiRunning (enrolled, n =10; completed, n=7); 2) group-based conventional running (enrolled, n=6; completed, n=4); 3) self-directed training with educational materials (enrolled, n =6; completed, n=6). The training schedule was prescribed for 8 weeks with 4 weeks of follow-up. All subjects completed overground running motion analyses before and after training. Outcomes Ankle, knee, hip joint peak moments and powers; Average vertical loading rate (AVLR), impact peak, cadence, stride length, strike index, and stride reach. Paired T-tests were used to compare differences with-in groups over-time. Results Form-Focused group reduced their Stride Reach (P = .047) after the training but not the other groups. Form-Focused group showed a close to significant reduction in knee adduction moment (P = .051) and a reduction in the peak ankle eversion moment (P = .027). Self-Directed group showed an increase in the running speed, (P =.056) and increases in ankle and knee joint powers and moments. Conclusions There are differences in the changes in running biomechanics between individuals trained in running form that emphazies mid-foot strike, higher cadence, and shorter stride compared to those not trained in the thise technique. These differences may be associated with reduced lower extremity stress in individuals trained in this running form but future studies are needed to confirm these findings in larger samples. PMID:25633634

Use of a wireless, inertial sensor-based system to objectively evaluate flexion tests in the horse.

PubMed

Marshall, J F; Lund, D G; Voute, L C

2012-12-01

A wireless, inertial sensor-based system has previously been validated for evaluation of equine lameness. However, threshold values have not been determined for the assessment of responses to flexion tests. The aim of this investigation was to evaluate a sensor-based system for objective assessment of the response to flexion. Healthy adult horses (n = 17) in work were recruited prospectively. Horses were instrumented with sensors on the head (accelerometer), pelvis (accelerometer) and right forelimb (gyroscope), before trotting in a straight line (minimum 25 strides) for 2 consecutive trials. Sensors measured 1) vertical pelvic movement asymmetry (PMA) for both right and left hindlimb strides and 2) average difference in maximum and minimum pelvic height (PDMax and PDMin) between right and left hindlimb strides in millimetres. A hindlimb was randomly selected for proximal flexion (60 s), after which the horse trotted a minimum of 10 strides. Response to flexion was blindly assessed as negative or positive by an experienced observer. Changes in PMA, PDMax and PDMin between baseline and flexion examinations were calculated for each test. Statistical analysis consisted of a Pearson's product moment test and linear regression on baseline trials, Mann-Whitney rank sum test for effect of flexion and receiver operator curve (ROC) analysis of test parameters. There was a strong correlation between trials for PMA, PDMin and PDMax measurements (P < 0.001). A positive flexion test resulted in a significant increase in PMA (P = 0.021) and PDMax (P = 0.05) only. Receiver-operator curve analysis established cut-off values for change in PMA and PDMax of 0.068 and 4.47 mm, respectively (sensitivity = 0.71, specificity = 0.65) to indicate a positive response to flexion. A positive response to flexion resulted in significant changes to objective measurements of pelvic symmetry. Findings support the use of inertial sensor systems to objectively assess response to flexion tests. Further investigation is warranted to establish cut-off values for objective assessment of other diagnostic procedures.

Six-week transition to minimalist shoes improves running economy and time-trial performance.

PubMed

Fuller, Joel T; Thewlis, Dominic; Tsiros, Margarita D; Brown, Nicholas A T; Buckley, Jonathan D

2017-12-01

This study investigated if gradually introducing runners to minimalist shoes during training improved running economy and time-trial performance compared to training in conventional shoes. Changes in stride rate, stride length, footfall pattern and ankle plantar-flexor strength were also investigated. Randomised parallel intervention trial. 61 trained runners gradually increased the amount of running performed in either minimalist (n=31) or conventional (n=30) shoes during a six-week standardised training program. 5-km time-trial performance, running economy, ankle plantar-flexor strength, footfall pattern, stride rate and length were assessed in the allocated shoes at baseline and after training. Footfall pattern was determined from the time differential between rearfoot and forefoot (TD R-F ) pressure sensors. The minimalist shoe group improved time-trial performance (effect size (ES): 0.24; 95% confidence interval (CI): 0.01, 0.48; p=0.046) and running economy (ES 0.48; 95%CI: 0.22, 0.74; p<0.001) more than the conventional shoe group. There were no minimalist shoe training effects on ankle plantar-flexor concentric (ES: 0.11; 95%CI: -0.18, 0.41; p=0.45), isometric (ES: 0.23; 95%CI: -0.17, 0.64; p=0.25), or eccentric strength (ES: 0.24; 95%CI: -0.17, 0.65; p=0.24). Minimalist shoes caused large reductions in TD R-F (ES: 1.03; 95%CI: 0.65, 1.40; p<0.001) but only two runners changed to a forefoot footfall. Minimalist shoes had no effect on stride rate (ES: 0.04; 95%CI: -0.08, 0.16; p=0.53) or length (ES: 0.06; 95%CI: -0.06, 0.18; p=0.35). Gradually introducing minimalist shoes over a six-week training block is an effective method for improving running economy and performance in trained runners. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Efficacy of Code Optimization on Cache-based Processors

NASA Technical Reports Server (NTRS)

VanderWijngaart, Rob F.; Chancellor, Marisa K. (Technical Monitor)

1997-01-01

The current common wisdom in the U.S. is that the powerful, cost-effective supercomputers of tomorrow will be based on commodity (RISC) micro-processors with cache memories. Already, most distributed systems in the world use such hardware as building blocks. This shift away from vector supercomputers and towards cache-based systems has brought about a change in programming paradigm, even when ignoring issues of parallelism. Vector machines require inner-loop independence and regular, non-pathological memory strides (usually this means: non-power-of-two strides) to allow efficient vectorization of array operations. Cache-based systems require spatial and temporal locality of data, so that data once read from main memory and stored in high-speed cache memory is used optimally before being written back to main memory. This means that the most cache-friendly array operations are those that feature zero or unit stride, so that each unit of data read from main memory (a cache line) contains information for the next iteration in the loop. Moreover, loops ought to be 'fat', meaning that as many operations as possible are performed on cache data-provided instruction caches do not overflow and enough registers are available. If unit stride is not possible, for example because of some data dependency, then care must be taken to avoid pathological strides, just ads on vector computers. For cache-based systems the issues are more complex, due to the effects of associativity and of non-unit block (cache line) size. But there is more to the story. Most modern micro-processors are superscalar, which means that they can issue several (arithmetic) instructions per clock cycle, provided that there are enough independent instructions in the loop body. This is another argument for providing fat loop bodies. With these restrictions, it appears fairly straightforward to produce code that will run efficiently on any cache-based system. It can be argued that although some of the important computational algorithms employed at NASA Ames require different programming styles on vector machines and cache-based machines, respectively, neither architecture class appeared to be favored by particular algorithms in principle. Practice tells us that the situation is more complicated. This report presents observations and some analysis of performance tuning for cache-based systems. We point out several counterintuitive results that serve as a cautionary reminder that memory accesses are not the only factors that determine performance, and that within the class of cache-based systems, significant differences exist.

Growth dominates choice in network percolation

NASA Astrophysics Data System (ADS)

Vijayaraghavan, Vikram S.; Noël, Pierre-André; Waagen, Alex; D'Souza, Raissa M.

2013-09-01

The onset of large-scale connectivity in a network (i.e., percolation) often has a major impact on the function of the system. Traditionally, graph percolation is analyzed by adding edges to a fixed set of initially isolated nodes. Several years ago, it was shown that adding nodes as well as edges to the graph can yield an infinite order transition, which is much smoother than the traditional second-order transition. More recently, it was shown that adding edges via a competitive process to a fixed set of initially isolated nodes can lead to a delayed, extremely abrupt percolation transition with a significant jump in large but finite systems. Here we analyze a process that combines both node arrival and edge competition. If started from a small collection of seed nodes, we show that the impact of node arrival dominates: although we can significantly delay percolation, the transition is of infinite order. Thus, node arrival can mitigate the trade-off between delay and abruptness that is characteristic of explosive percolation transitions. This realization may inspire new design rules where network growth can temper the effects of delay, creating opportunities for network intervention and control.

The Edge Factor in Early Word Segmentation: Utterance-Level Prosody Enables Word Form Extraction by 6-Month-Olds

PubMed Central

Johnson, Elizabeth K.; Seidl, Amanda; Tyler, Michael D.

2014-01-01

Past research has shown that English learners begin segmenting words from speech by 7.5 months of age. However, more recent research has begun to show that, in some situations, infants may exhibit rudimentary segmentation capabilities at an earlier age. Here, we report on four perceptual experiments and a corpus analysis further investigating the initial emergence of segmentation capabilities. In Experiments 1 and 2, 6-month-olds were familiarized with passages containing target words located either utterance medially or at utterance edges. Only those infants familiarized with passages containing target words aligned with utterance edges exhibited evidence of segmentation. In Experiments 3 and 4, 6-month-olds recognized familiarized words when they were presented in a new acoustically distinct voice (male rather than female), but not when they were presented in a phonologically altered manner (missing the initial segment). Finally, we report corpus analyses examining how often different word types occur at utterance boundaries in different registers. Our findings suggest that edge-aligned words likely play a key role in infants’ early segmentation attempts, and also converge with recent reports suggesting that 6-month-olds’ have already started building a rudimentary lexicon. PMID:24421892

Toward Edge-Defined Holey Boron Nitride Nanosheets

NASA Technical Reports Server (NTRS)

Lin, Yi; Liao, Yunlong; Chen, Zhongfan; Connell, John W.

2015-01-01

"Holey" two-dimensional (2D) nanosheets with well-defined holy morphology and edge chemistry are highly desirable for applications such as energy storage, catalysis, sensing, transistors, and molecular transport/separation. For example, holey grapheme is currently under extensive investigation for energy storage applications because of the improvement in ion transport due to through the thickness pathways provided by the holes. Without the holes, the 2D materials have significant limitations for such applications in which efficient ion transport is important. As part of an effort to apply this approach to other 2D nanomaterials, a method to etch geometrically defined pits or holes on the basal plane surface of hexagonal boron nitride (h-BN) nanosheets has been developed. The etching, conducted via heating in ambient air using metal nanoparticles as catalysts, was facile, controllable, and scalable. Starting h-BN layered crystals were etched and subsequently exfoliated into boron nitride nanosheets (BNNSs). The as-etched and exfoliated h-BN nanosheets possessed defined pit and hole shapes that were comprised of regulated nanostructures at the edges. The current finding are the first step toward the bulk preparation of holey BNNSs with defined holes and edges.

Scaling analysis of the non-Abelian quasiparticle tunneling in Z}}_k FQH states

NASA Astrophysics Data System (ADS)

Li, Qi; Jiang, Na; Wan, Xin; Hu, Zi-Xiang

2018-06-01

Quasiparticle tunneling between two counter propagating edges through point contacts could provide information on its statistics. Previous study of the short distance tunneling displays a scaling behavior, especially in the conformal limit with zero tunneling distance. The scaling exponents for the non-Abelian quasiparticle tunneling exhibit some non-trivial behaviors. In this work, we revisit the quasiparticle tunneling amplitudes and their scaling behavior in a full range of the tunneling distance by putting the electrons on the surface of a cylinder. The edge–edge distance can be smoothly tuned by varying the aspect ratio for a finite size cylinder. We analyze the scaling behavior of the quasiparticles for the Read–Rezayi states for and 4 both in the short and long tunneling distance region. The finite size scaling analysis automatically gives us a critical length scale where the anomalous correction appears. We demonstrate this length scale is related to the size of the quasiparticle at which the backscattering between two counter propagating edges starts to be significant.

Fabrication and Testing of Mo-Re Heat Pipes Embedded in Carbon/Carbon

NASA Technical Reports Server (NTRS)

Glass, David E.; Merrigan, Michael A.; Sena, J. Tom

1998-01-01

Refractory-composite/heat-pipe-cooled wing an tail leading edges are being considered for use on hypersonic vehicles to limit maximum temperatures to values below material reuse limits and to eliminate the need to actively cool the leading edges. The development of a refractory-composite/heat-pipe-cooled leading edge has evolved from the design stage to the fabrication and testing of heat pipes embedded in carbon/carbon (C/C). A three-foot-long, molybdenum-rhenium heat pipe with a lithium working fluid was fabricated and tested at an operating temperature of 2460 F to verify the individual heat-pipe design. Following the fabrication of this heat pipe, three additional heat pipes were fabricated and embedded in C/C. The C/C heat-pipe test article was successfully tested using quartz lamps in a vacuum chamber in both a horizontal and vertical orientation. Start up and steady state data are presented for the C/C heat-pipe test article. Radiography and eddy current evaluations were performed on the test article.

Ab initio study of edge effect on relative motion of walls in carbon nanotubes

NASA Astrophysics Data System (ADS)

Popov, Andrey M.; Lebedeva, Irina V.; Knizhnik, Andrey A.; Lozovik, Yurii E.; Potapkin, Boris V.

2013-01-01

Interwall interaction energies of double-walled nanotubes with long inner and short outer walls are calculated as functions of coordinates describing relative rotation and displacement of the walls using van der Waals corrected density functional theory. The magnitude of corrugation and the shape of the potential energy relief are found to be very sensitive to changes of the shorter wall length at subnanometer scale and atomic structure of the edges if at least one of the walls is chiral. Threshold forces required to start relative motion of the short walls and temperatures at which the transition between diffusive and free motion of the short walls takes place are estimated. The edges are also shown to provide a considerable contribution to the barrier to relative rotation of commensurate nonchiral walls. For such walls, temperatures of orientational melting, i.e., the crossover from rotational diffusion to free relative rotation, are estimated. The possibility to produce nanotube-based bolt/nut pairs and nanobearings is discussed.

Off-axis mirror fabrication from spherical surfaces under mechanical stress

NASA Astrophysics Data System (ADS)

Izazaga-Pérez, R.; Aguirre-Aguirre, D.; Percino-Zacarías, M. E.; Granados-Agustín, Fermin-Salomon

2013-09-01

The preliminary results in the fabrication of off-axis optical surfaces are presented. The propose using the conventional polishing method and with the surface under mechanical stress at its edges. It starts fabricating a spherical surface using ZERODUR® optical glass with the conventional polishing method, the surface is deformed by applying tension and/or compression at the surface edges using a specially designed mechanical mount. To know the necessary deformation, the interferogram of the deformed surface is analyzed in real time with a ZYGO® Mark II Fizeau type interferometer, the mechanical stress is applied until obtain the inverse interferogram associated to the off-axis surface that we need to fabricate. Polishing process is carried out again until obtain a spherical surface, then mechanical stress in the edges are removed and compares the actual interferogram with the theoretical associated to the off-axis surface. To analyze the resulting interferograms of the surface we used the phase shifting analysis method by using a piezoelectric phase-shifter and Durango® interferometry software from Diffraction International™.

Topological edge states in ultra thin Bi(110) puckered crystal lattice

NASA Astrophysics Data System (ADS)

Wang, Baokai; Hsu, Chuanghan; Chang, Guoqing; Lin, Hsin; Bansil, Arun

We discuss the electronic structure of a 2-ML Bi(110) film with a crystal structure similar to that of black phosphorene. In the absence of Spin-Orbit coupling (SOC), the film is found to be a semimetal with two kinds of Dirac cones, which are classified by their locations in the Brillouin zone. All Dirac nodes are protected by crystal symmetry and carry non-zero winding numbers. When considering ribbons, along specific directions, projections of Dirac nodes serve as starting or ending points of edge bands depending on the sign of their carried winding number. After the inclusion of the SOC, all Dirac nodes are gapped out. Correspondingly, the edge states connecting Dirac nodes split and cross each other, and thus form a Dirac node at the boundary of the 1D Brillouin zone, which suggests that the system is a Quantum Spin Hall insulator. The nontrivial Quantum Spin Hall phase is also confirmed by counting the product of parities of the occupied bands at time-reversal invariant points.

SR high-speed K-edge subtraction angiography in the small animal (abstract)

NASA Astrophysics Data System (ADS)

Takeda, T.; Akisada, M.; Nakajima, T.; Anno, I.; Ueda, K.; Umetani, K.; Yamaguchi, C.

1989-07-01

To assess the ability of the high-speed K-edge energy subtraction system which was made at beamline 8C of Photon Factory, Tsukuba, we performed an animal experiment. Rabbits were used for the intravenous K-edge subtraction angiography. In this paper, the actual images of the artery obtained by this system, are demonstrated. The high-speed K-edge subtraction system consisted of movable silicon (111) monocrystals, II-ITV, and digital memory system. Image processing was performed by 68000-IP computer. The monochromatic x-ray beam size was 50×60 mm. Photon energy above and below iodine K edge was changed within 16 ms and 32 frames of images were obtained sequentially. The rabbits were anaesthetized by phenobarbital and a 5F catheter was inserted into inferior vena cava via the femoral vein. 1.5 ml/kg of contrast material (Conlaxin H) was injected at the rate of 0.5 ml/kg/s. TV images were obtained 3 s after the starting point of injection. By using this system, the clear K-edge subtracted images were obtained sequentially as a conventional DSA system. The quality of the images were better than that obtained by DSA. The dynamical blood flow was analyzed, and the best arterial image could be selected from the sequential images. The structures of aortic arch, common carotid arteries, right subclavian artery, and internal thoracic artery were obtained at the chest. Both common carotid arteries and vertebral arteries were recorded at the neck. The diameter of about 0.3-0.4 mm artery could be clearly revealed. The high-speed K-edge subtraction system demonstrates the very sharp arterial images clearly and dynamically.

Living on the Edges: Spatial Niche Occupation of Asian Citrus Psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), in Citrus Groves.

PubMed

Sétamou, Mamoudou; Bartels, David W

2015-01-01

The spatial niche occupation of the Asian citrus psyllid, Diaphorina citri Kuwayama, 1908, was evaluated to determine its field colonization and food resource exploitation strategies in citrus groves. Mature grapefruit and sweet orange groves were surveyed as part of an area-wide program in 2009-2010 to determine D. citri population densities and between-tree distribution. In both cultivars, significantly more psyllids were found on perimeter trees throughout the study period suggesting a strong edge effect in D. citri distribution in the groves. D. citri densities and infestation levels gradually declined from the edge to the center of grove. Higher numbers of D. citri were recorded on trees located on the east and south sides of the groves than those on the west and north sides. Citrus groves located at the outer edge of the study with at least one side non-surrounded to other citrus groves harbored significantly more D. citri than groves located within the block cluster and entirely surrounded by other groves. In detailed field studies during 2012, infestation of D. citri started from border trees in the grove where possibly one generation is completed before inner trees become infested. In addition, psyllid densities decreased significantly with increasing distance from the grove edge. Using the selection index, D citri exhibited a strong niche occupation preference for border trees.

Living on the Edges: Spatial Niche Occupation of Asian Citrus Psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), in Citrus Groves

PubMed Central

2015-01-01

The spatial niche occupation of the Asian citrus psyllid, Diaphorina citri Kuwayama, 1908, was evaluated to determine its field colonization and food resource exploitation strategies in citrus groves. Mature grapefruit and sweet orange groves were surveyed as part of an area-wide program in 2009–2010 to determine D. citri population densities and between-tree distribution. In both cultivars, significantly more psyllids were found on perimeter trees throughout the study period suggesting a strong edge effect in D. citri distribution in the groves. D. citri densities and infestation levels gradually declined from the edge to the center of grove. Higher numbers of D. citri were recorded on trees located on the east and south sides of the groves than those on the west and north sides. Citrus groves located at the outer edge of the study with at least one side non-surrounded to other citrus groves harbored significantly more D. citri than groves located within the block cluster and entirely surrounded by other groves. In detailed field studies during 2012, infestation of D. citri started from border trees in the grove where possibly one generation is completed before inner trees become infested. In addition, psyllid densities decreased significantly with increasing distance from the grove edge. Using the selection index, D citri exhibited a strong niche occupation preference for border trees. PMID:26193111

Investigation of the hydrogen fluxes in the plasma edge of W7-AS during H-mode discharges

NASA Astrophysics Data System (ADS)

Langer, U.; Taglauer, E.; Fischer, R.; W7-AS Team

2001-03-01

In the stellarator W7-AS the H-mode is characterized by an edge transport barrier which is localized within a few centimeters inside the separatrix. The corresponding L-H transition shows well-known features such as the steepening of the temperature and density profiles in the region of the separatrix. With a so-called sniffer probe the temporal development of the hydrogen and deuterium fluxes has been studied in the plasma edge during different H-mode discharges with deuterium gas puffing. Prior to the transition a significant reduction of the deuterium and also the hydrogen fluxes can be observed. This fact confirms the assumption that the steepening of the density profiles starts at the outermost edge of the plasma. Moreover, sniffer probe measurements in the plasma edge could therefore identify a precursor for the L-H transition. The analysis of the hydrogen neutral gases shows a distinct change of the hydrogen isotope ratio during the transition. This observation is in agreement with the change in the particle fluxes onto the targets and can also be seen in the reduced H α signals from the limiters. It is further demonstrated that significant improvement in the time resolution of the measured data can be obtained by deconvolution of the data with the apparatus function using Bayesian probability theory and the Maximum Entropy method with adaptive kernels.

Pseudoelastic Nitinol-Based Device for Relaxation of Spastic Elbow in Stroke Patients

NASA Astrophysics Data System (ADS)

Viscuso, S.; Pittaccio, S.; Caimmi, M.; Gasperini, G.; Pirovano, S.; Villa, E.; Besseghini, S.; Molteni, F.

2009-08-01

A compliant brace (EDGES) promoting spastic elbow relaxation was designed to investigate the potentialities of pseudoelastic NiTi in orthotics. By exploiting its peculiar characteristics, EDGES could improve elbow posture without constraining movements and thus avoiding any pain to the patient. A commercial Ni50.7-Ti49.3 alloy heat treated at 400 °C 1 h + WQ was selected for this application. A prototype of EDGES was assembled with two thermoplastic shells connected by polycentric hinges. Four 2-mm-diameter NiTi bars were encastred in the upper-arm shell and let slide along tubular fixtures on the forearm. Specially designed bending tests demonstrated suitable moment-angle characteristics. Two post-stroke subjects (aged 62 and 64, mild elbow flexors spasticity) wore EDGES for 1 week, at least 10 h a day. No additional treatment was applied during this period or the following week. A great improvement (20° ± 5°) of the resting position was observed in both patients as early as 3 h after starting the treatment. Acceptability was very good. A slight decrease in spasticity was also observed in both subjects. All the effects disappeared 1 week after discontinuation. EDGES appears to be a good alternative to traditional orthoses in terms of acceptability and effectiveness in improving posture, especially whenever short-term splinting is planned.

Dealing with Mental Health Issues on Campus Starts with Early Recognition and Intervention

ERIC Educational Resources Information Center

Futo, Jeff

2011-01-01

A fair number of students are not in the proper frame of mind to be "prepared" for their future beyond the academic world due to the stressors associated with higher education. Finances, relationships, mental health issues, and so on, all contribute to someone being pushed to the edge when combined with the pressures of papers, exams, and…

An Interview with Joel McIntosh: Reflections on Gifted Education and the History of "JOAA"

ERIC Educational Resources Information Center

Siegle, Del; McCoach, D. Betsy

2011-01-01

This article presents an interview with Joel McIntosh, the publisher at Prufrock Press, whose publications reach more than 50,000 individuals and libraries. McIntosh started Prufrock in 1988 with a vision of making a powerful difference in the lives of gifted and talented children by striving to provide quality materials and cutting-edge research…

To Improve Schools, Stop Guessing and Start Using Research

ERIC Educational Resources Information Center

Simmons, John

2011-01-01

The data are clear: Unless the nation can find a better way to accelerate improvement in the quality of education and implement it in the next 10 years, this nation will lose its competitive edge against other nations and another generation of children will be lost. Eighty percent of Illinois high school graduates are not capable of doing the…

Fires in the Mind: What Kids Can Tell Us about Motivation and Mastery

ERIC Educational Resources Information Center

Cushman, Kathleen

2010-01-01

Through the voices of students themselves, "Fires in the Mind" brings a game-changing question to teachers of adolescents: What does it take to get really good at something? Starting with what they already know and do well, teenagers from widely diverse backgrounds join a cutting-edge dialogue with adults about the development of mastery in and…

Aerodynamics of a translating comb-like plate inspired by a fairyfly wing

NASA Astrophysics Data System (ADS)

Lee, Seung Hun; Kim, Daegyoum

2017-08-01

Unlike the smooth wings of common insects or birds, micro-scale insects such as the fairyfly have a distinctive wing geometry, comprising a frame with several bristles. Motivated by this peculiar wing geometry, we experimentally investigated the flow structure of a translating comb-like wing for a wide range of gap size, angle of attack, and Reynolds number, Re = O(10) - O(103), and the correlation of these parameters with aerodynamic performance. The flow structures of a smooth plate without a gap and a comb-like plate are significantly different at high Reynolds number, while little difference was observed at the low Reynolds number of O(10). At low Reynolds number, shear layers that were generated at the edges of the tooth of the comb-like plate strongly diffuse and eventually block a gap. This gap blockage increases the effective surface area of the plate and alters the formation of leading-edge and trailing-edge vortices. As a result, the comb-like plate generates larger aerodynamic force per unit area than the smooth plate. In addition to a quasi-steady phase after the comb-like plate travels several chords, we also studied a starting phase of the shear layer development when the comb-like plate begins to translate from rest. While a plate with small gap size can generate aerodynamic force at the starting phase as effectively as at the quasi-steady phase, the aerodynamic force drops noticeably for a plate with a large gap because the diffusion of the developing shear layers is not enough to block the gap.

Kinematics gait disorder in men with fibromyalgia.

PubMed

Heredia-Jimenez, Jose M; Soto-Hermoso, Victor M

2014-01-01

The aim of this study was to assess the kinematics disorder of gait in men with fibromyalgia. We studied 12 male with fibromyalgia and 14 healthy men. Each participant of the study walked five trials along a 18.6-m walkway. Fibromyalgia patients completed a Spanish version of Fibromyalgia Impact Questionnaire. Significant differences between fibromyalgia and control groups were found in velocity, stride length, and cadence. Gait parameters of men affected by fibromyalgia were impaired when compared to those of healthy group due to bradykinesia. According to previous studies to assess gait variables in female patients, the male with fibromyalgia also showed lower values of velocity, cadence, and stride length than healthy group but not reported significant differences in swing, stance, single, or double support phase.

Gait characteristics over the course of a race in recreational marathon competitors.

PubMed

Bertram, John E A; Prebeau-Menezes, Leif; Szarko, Matthew J

2013-03-01

We analyzed gait and function of the supporting limb in participants of a marathon race at three stages: prerace, midrace (18 km), and near the end of the race (36 km). We confirmed that the most successful runners were able to maintain running speed for the duration of the race with little change in speed or gait. Speed slowed progressively during the race for those with slower race times, but stride frequency-stride length relationships remained normal for the speed they ran. These findings differ from most lab-based studies of fatigue, in which runners are forced to match a constant preset treadmill speed. Small changes in maximum ground force were seen in both slow- and fast-running participants as race end approached.

Using convolutional neural networks to estimate time-of-flight from PET detector waveforms

NASA Astrophysics Data System (ADS)

Berg, Eric; Cherry, Simon R.

2018-01-01

Although there have been impressive strides in detector development for time-of-flight positron emission tomography, most detectors still make use of simple signal processing methods to extract the time-of-flight information from the detector signals. In most cases, the timing pick-off for each waveform is computed using leading edge discrimination or constant fraction discrimination, as these were historically easily implemented with analog pulse processing electronics. However, now with the availability of fast waveform digitizers, there is opportunity to make use of more of the timing information contained in the coincident detector waveforms with advanced signal processing techniques. Here we describe the application of deep convolutional neural networks (CNNs), a type of machine learning, to estimate time-of-flight directly from the pair of digitized detector waveforms for a coincident event. One of the key features of this approach is the simplicity in obtaining ground-truth-labeled data needed to train the CNN: the true time-of-flight is determined from the difference in path length between the positron emission and each of the coincident detectors, which can be easily controlled experimentally. The experimental setup used here made use of two photomultiplier tube-based scintillation detectors, and a point source, stepped in 5 mm increments over a 15 cm range between the two detectors. The detector waveforms were digitized at 10 GS s-1 using a bench-top oscilloscope. The results shown here demonstrate that CNN-based time-of-flight estimation improves timing resolution by 20% compared to leading edge discrimination (231 ps versus 185 ps), and 23% compared to constant fraction discrimination (242 ps versus 185 ps). By comparing several different CNN architectures, we also showed that CNN depth (number of convolutional and fully connected layers) had the largest impact on timing resolution, while the exact network parameters, such as convolutional filter size and number of feature maps, had only a minor influence.

Forces and mechanical energy fluctuations during diagonal stride roller skiing; running on wheels?

PubMed

Kehler, Alyse L; Hajkova, Eliska; Holmberg, Hans-Christer; Kram, Rodger

2014-11-01

Mechanical energy can be conserved during terrestrial locomotion in two ways: the inverted pendulum mechanism for walking and the spring-mass mechanism for running. Here, we investigated whether diagonal stride cross-country roller skiing (DIA) utilizes similar mechanisms. Based on previous studies, we hypothesized that running and DIA would share similar phase relationships and magnitudes of kinetic energy (KE), and gravitational potential energy (GPE) fluctuations, indicating elastic energy storage and return, as if roller skiing is like 'running on wheels'. Experienced skiers (N=9) walked and ran at 1.25 and 3 m s(-1), respectively, and roller skied with DIA at both speeds on a level dual-belt treadmill that recorded perpendicular and parallel forces. We calculated the KE and GPE of the center of mass from the force recordings. As expected, the KE and GPE fluctuated with an out-of-phase pattern during walking and an in-phase pattern during running. Unlike walking, during DIA, the KE and GPE fluctuations were in phase, as they are in running. However, during the glide phase, KE was dissipated as frictional heat and could not be stored elastically in the tendons, as in running. Elastic energy storage and return epitomize running and thus we reject our hypothesis. Diagonal stride cross-country skiing is a biomechanically unique movement that only superficially resembles walking or running. © 2014. Published by The Company of Biologists Ltd.

Gait consistency over a 7-day interval in people with Parkinson's disease.

PubMed

Urquhart, D M; Morris, M E; Iansek, R

1999-06-01

To evaluate the consistency of temporal and spatial parameters of the walking pattern in subjects with idiopathic Parkinson's disease (PD) over a 7-day interval during the "on" phase of the levodopa medication cycle. Walking patterns were measured on a 12-meter walkway at the Kingston Gait Laboratory, Cheltenham, using a computerized stride analyzer. Sixteen subjects (7 women, 9 men) with PD recruited from the Movement Disorders Clinic at Kingston Centre. Speed of walking, stride length, cadence, and the percentage of the walking cycle spent in the double limb support phase of gait were measured, together with the level of disability as indexed by the modified Webster scale. Product-moment correlation coefficients and intraclass correlation coefficients (ICC 2,1) for repeat measures over a 7-day interval were high for speed (r = .90; ICC = .93), cadence (r = .90; ICC = .86), and stride length (r = 1.00; ICC = .97) and moderate for double limb support duration after removal of outliers (r = .75; ICC = .73); 95% confidence intervals for the change scores were within clinically acceptable limits for all variables. The mean modified Webster score was 11.4 on the first day and 10.1 7 days later. The gait pattern and level of disability in subjects with PD without severe motor fluctuations remained stable over a 1-week period when optimal medication prevailed.

Examination of print and telephone channels for physical activity promotion: Rationale, design, and baseline data from Project STRIDE.

PubMed

Marcus, Bess H; Napolitano, Melissa A; King, Abby C; Lewis, Beth A; Whiteley, Jessica A; Albrecht, Anna E; Parisi, Alfred F; Bock, Beth C; Pinto, Bernardine M; Sciamanna, Christopher A; Jakicic, John M; Papandonatos, George D

2007-01-01

Project STRIDE is a 4-year randomized controlled trial comparing two computer-based expert system guided intervention delivery channels (phone vs. print) for physical activity adoption and short-term maintenance among previously sedentary adults. Sedentary adults (n=239) were randomized to one of the following (1) telephone-based, individualized motivationally-tailored feedback; (2) print-based, individualized motivationally-tailored feedback; (3) contact-control delayed treatment group (received intervention after 12 months as control). This paper: (1) outlines the study design, rationale, and participant sample; and (2) describes relationships between baseline variables to better understand their influence on the efficacy of the intervention. Participants averaged 19.8+/-25.0 min of physical activity/week that was at least of moderate intensity, with no group differences. The average estimated VO(2) at 85% of maximum heart rate was 25.6 ml/kg/min. Body fat was 34.1% for women and 23.2% for men and the BMI of the sample averaged 28.5 kg/m(2). Project STRIDE examines non face-to-face approaches for promoting physical activity behavior. It has unique features including a direct comparison of an expert system guided intervention delivered via phone or print. Future analyses will examine the cost-effectiveness of the interventions and this will likely yield important information for policy-makers.

Exploring the feasibility and acceptability of sensor monitoring of gait and falls in the homes of persons with multiple sclerosis.

PubMed

Newland, Pamela; Wagner, Joanne M; Salter, Amber; Thomas, Florian P; Skubic, Marjorie; Rantz, Marilyn

2016-09-01

Gait parameters variability and falls are problems for persons with MS and have not been adequately captured in the home. Our goal was to explore the feasibility and acceptability of monitoring of gait and falls in the homes of persons with MS over a period of 30 days. To test the feasibility of measuring gait and falls for 30days in the home of persons with MS, spatiotemporal gait parameters stride length, stride time, and gait speed were compared. A 3D infrared depth imaging system has been developed to objectively measure gait and falls in the home environment. Participants also completed a 16-foot GaitRite electronic pathway walk to validate spatiotemporal parameters of gait (gait speed (cm/s), stride length (cm), and gait cycle time(s)) during the timed 25 foot walking test (T25FWT). We also documented barriers to feasibility of installing the in-home sensors for these participants. The results of the study suggest that the Kinect sensor may be used as an alternative device to measure gait for persons with MS, depending on the desired accuracy level. Ultimately, using in-home sensors to analyze gait parameters in real time is feasible and could lead to better analysis of gait in persons with MS. Copyright © 2016 Elsevier B.V. All rights reserved.

Lower limb mechanics during moderate high-heel jogging and running in different experienced wearers.

PubMed

Fu, Fengqin; Zhang, Yan; Shu, Yang; Ruan, Guoqing; Sun, Jianjun; Baker, Julien S; Gu, Yaodong

2016-08-01

The aim of this study is to investigate the differences in lower limb kinematics and kinetics between experienced (EW) and inexperienced (IEW) moderate high-heel wearers during jogging and running. Eleven experienced female wearers of moderate high-heel shoes and eleven matched controls participated in jogging and running tests. A Vicon motion analysis system was used to capture kinematic data and a Kistler force platform was used to collect ground reaction force (GRF). There were no significant differences in jogging and running speed respectively. Compared with IEW, EW adopted larger stride length (SL) with lower stride frequency (SF) at each corresponding speed. During running, EW enlarged SL significantly while IEW increased both SL and SF significantly. Kinematic data showed that IEW had generally larger joint range of motion (ROM) and peak angles during stance phase. Speed effect was not obvious within IEW. EW exhibited a significantly increased maximal vertical GRF (Fz2) and vertical average loading rate (VALR) during running, which was potentially caused by overlong stride. These suggest that both EW and IEW are at high risk of joint injuries when running on moderate high heels. For wearers who have to do some running on moderate high heels, it is crucial to control joint stability and balance SL and SF consciously. Copyright © 2016 Elsevier B.V. All rights reserved.

The Fence at the Edge of the Cliff: Approaching Family Policy in North America. Perspectives.

ERIC Educational Resources Information Center

Mirabelli, Alan

Noting that modern governments have a choice between a deliberate, coherent family policy and one of inconsistency and mischance, this paper presents the family policy of Quebec as a model of a coherent set of measures aimed explicitly at family well-being. This policy, started in the late 1980s, was put into place through the appointment of a…

Optical timing receiver for the NASA laser ranging system. Part 2: High precision time interval digitizer

NASA Technical Reports Server (NTRS)

Leskovar, B.; Turko, B.

1977-01-01

The development of a high precision time interval digitizer is described. The time digitizer is a 10 psec resolution stop watch covering a range of up to 340 msec. The measured time interval is determined as a separation between leading edges of a pair of pulses applied externally to the start input and the stop input of the digitizer. Employing an interpolation techniques and a 50 MHz high precision master oscillator, the equivalent of a 100 GHz clock frequency standard is achieved. Absolute accuracy and stability of the digitizer are determined by the external 50 MHz master oscillator, which serves as a standard time marker. The start and stop pulses are fast 1 nsec rise time signals, according to the Nuclear Instrument means of tunnel diode discriminators. Firing level of the discriminator define start and stop points between which the time interval is digitized.

Adaptation to the edge of chaos in a self-starting Kerr-lens mode-locked laser

NASA Astrophysics Data System (ADS)

Hsu, C. C.; Lin, J. H.; Hsieh, W. F.

2009-08-01

We experimentally and numerically demonstrated that self-focusing acts as a slow-varying control parameter that suppresses the transient chaos to reach a stable mode-locking (ML) state in a self-starting Kerr-lens mode-locked Ti:sapphire laser without external modulation and feedback control. Based on Fox-Li’s approach, including the self-focusing effect, the theoretical simulation reveals that the self-focusing effect is responsible for the self-adaptation. The self-adaptation occurs at the boundary between the chaotic and continuous output regions in which the laser system begins with a transient chaotic state with fractal correlation dimension, and then evolves with reducing dimension into the stable ML state.

Sacroiliitis

MedlinePlus

... an inflammation of one or both of your sacroiliac joints — situated where your lower spine and pelvis ... climbing Running Taking large strides Causes Causes for sacroiliac joint dysfunction include: Traumatic injury. A sudden impact, ...

Take Another Look at Ads

ERIC Educational Resources Information Center

McCafferty, John J.

1973-01-01

Presents an interview with former Federal Communications Commissioner, Lee Loevinger, who feels more people should recognize that the advertising field has made great strides in self-regulation in recent years. (RB)

Muscle Activation Patterns in Infants with Myelomeningocele Stepping on a Treadmill

PubMed Central

Sansom, Jennifer K.; Teulier, Caroline; Smith, Beth A.; Moerchen, Victoria; Muraszko, Karin; Ulrich, Beverly D.

2013-01-01

Purpose To characterize how infants with myelomeningocele (MMC) activate lower limb muscles over the first year of life, without practice, while stepping on a motorized treadmill. Methods Twelve infants with MMC were tested longitudinally at 1, 6, 12 months. Electromyography (EMG) was used to collect data from the tibialis anterior (TA), lateral gastrocnemius (LG), rectus femoris (RF), biceps femoris (BF). Results Across the first year, infants showed no EMG activity for ~50% of the stride cycle w/poor rhythmicity and timing of muscles, when activated. Single muscle activation predominated; agonist-antagonist co-activation was low. Probability of individual muscle activity across the stride decreased w/age. Conclusions Infants with MMC show high variability in timing and duration of muscle activity, few complex combinations, and very little change over time. PMID:23685739

[Descending control of quiet standing and walking: a plausible neurophysiological basis of falls in elderly people].

PubMed

Nakajima, Masashi

2011-03-01

Quiet standing and walking are generally considered to be an automatic process regulated by sensory feedback. In our report "Astasia without abasia due to peripheral neuropathy," which was published in 1994, we proposed that forced stepping in patients lacking the ankle torque is a compensatory motor control in order to maintain an upright posture. A statistical-biomechanics approach to the human postural control system has revealed open-loop (descending) control as well as closed-loop (feedback) control in quiet standing, and fractal dynamics in stride-to-stride fluctuations of walking. The descending control system of bipedal upright posture and gait may have a functional link to cognitive domains. Increasing dependence on the descending control system with aging may play a role in falls in elderly people.

Effects of homogeneous condensation in compressible flows: Ludwieg-tube experiments and simulations

NASA Astrophysics Data System (ADS)

Luo, Xisheng; Lamanna, Grazia; Holten, A. P. C.; van Dongen, M. E. H.

Effects of homogeneous nucleation and subsequent droplet growth in compressible flows in humid nitrogen are investigated numerically and experimentally. A Ludwieg tube is employed to produce expansion flows. Corresponding to different configurations, three types of experiment are carried out in such a tube. First, the phase transition in a strong unsteady expansion wave is investigated to demonstrate the mutual interaction between the unsteady flow and the condensation process and also the formation of condensation-induced shock waves. The role of condensation-induced shocks in the gradual transition from a frozen initial structure to an equilibrium structure is explained. Second, the condensing flow in a slender supersonic nozzle G2 is considered. Particular attention is given to condensation-induced oscillations and to the transition from symmetrical mode-1 oscillations to asymmetrical mode-2 oscillations in a starting nozzle flow, as first observed by Adam & Schnerr. The transition is also found numerically, but the amplitude, frequency and transition time are not yet well predicted. Third, a sharp-edged obstacle is placed in the tube to generate a starting vortex. Condensation in the vortex is found. Owing to the release of latent heat of condensation, an increase in the pressure and temperature in the vortex core is observed. Condensation-induced shock waves are found, for a sufficiently high initial saturation ratio, which interact with the starting vortex, resulting in a very complex flow. As time proceeds, a subsonic or transonic free jet is formed downstream of the sharp-edged obstacle, which becomes oscillatory for a relatively high main-flow velocity and for a sufficiently high humidity.

Numerical investigation of the self-starting of a vertical axis wind turbine

NASA Astrophysics Data System (ADS)

Tsai, Hsieh-Chen; Colonius, Tim

2014-11-01

The immersed boundary method is used to simulate the incompressible flow around two-dimensional airfoils at sub-scale Reynolds number in order to investigate the self-starting capability of a vertical-axis wind turbine (VAWT). By investigating a single blade fixed at various angle of attacks, the leading edge vortex (LEV) is shown to play an important role in the starting mechanism for both flat-plate and NACA 0018 blades. Depending on the angle of attack of the blade, as the LEV grows, the corresponding low pressure region results in a thrust in the tangential direction, which produces a positive torque to VAWT. Due to the characteristics of the blades, a NACA 0018 blade produces a larger thrust over a wider range of angle of attacks than a flat-plate blade. Therefore, a VAWT with NACA 0018 blades can self-start more easily than one with flat-plate blades. Moreover, by investigating the starting torque of three-bladed VAWTs fixed at various orientations, the optimal orientation that produces the largest torque to start both VAWTs is with a blade parallel to the flow and facing downstream. The simulations are also compared to results from companion water-tunnel experiments at Caltech. This project is supported by Caltech FLOWE center/Gordon and Betty Moore Foundation.

Difference Between Adolescent and Collegiate Baseball Pitchers in the Kinematics and Kinetics of the Lower Limbs and Trunk During Pitching Motion

PubMed Central

Kageyama, Masahiro; Sugiyama, Takashi; Kanehisa, Hiroaki; Maeda, Akira

2015-01-01

The purpose of this study was to clarify the differences between adolescent and collegiate baseball pitchers in the kinematic and kinetic profiles of the trunk and lower limbs during the pitching motion. The subjects were thirty-two adolescent baseball pitchers aged 12-15 years (APG) and thirty collegiate baseball pitchers aged 18-22 years (CPG). Three-dimensional motion analysis with a comprehensive lower-extremity model was used to evaluate kinematic and kinetic parameters during baseball pitching. The ground reaction forces (GRFs) of the pivot and stride legs during pitching were determined using two multicomponent force plates. The joint torques of hip, knee, and ankle were calculated by the inverse-dynamics computation of musculoskeletal human models using motion-capture data. To eliminate any effect of variation in body size, kinetic and GRFs data were normalized by dividing them by body mass. The velocity of a pitched ball was significantly higher (p < 0.01) in CPG (35.2 ± 1.9 m·s-1) than in the APG (30.7 ± 2.7 m·s-1). Most kinematic parameters for the lower limbs were similar between the CPG and the APG. Maximum Fy (toward the throwing direction) on the pivot leg and Fy and resultant forces on the stride leg at ball release were significantly greater in the CPG than in the APG (p < 0.05). Hip and knee joint torques on the lower limbs were significantly greater in the CPG than in the APG (p < 0.05). The present study indicates that the kinematics of lower limbs during baseball pitching are similar between adolescent and collegiate pitchers, but the momentum of the lower limbs during pitching is lower in adolescent pitchers than in collegiate ones, even when the difference in body mass is considered. Key points Collegiate baseball pitchers can generate the hip and knee joint torques on the pivot leg for accelerating the body forward. Collegiate baseball pitchers can generate the hip and knee joint torques to control/stabilize the stride leg in order to increase momentum on the stride leg during the arm acceleration phase. The kinematics of the lower limbs during baseball pitching are similar between adolescent and collegiate pitchers, but the momentum of the lower limbs during pitching is lower in adolescent pitchers than in collegiate ones, even when the difference in body mass is considered. Adolescent baseball pitchers cannot generate the hip and knee joint torques in the pivot and stride leg for transfer of the energy of trunk and the arm. PMID:25983571

Multi-species collapses at the warm edge of a warming sea

PubMed Central

Rilov, Gil

2016-01-01

Even during the current biodiversity crisis, reports on population collapses of highly abundant, non-harvested marine species were rare until very recently. This is starting to change, especially at the warm edge of species’ distributions where populations are more vulnerable to stress. The Levant basin is the southeastern edge of distribution of most Mediterranean species. Coastal water conditions are naturally extreme, and are fast warming, making it a potential hotspot for species collapses. Using multiple data sources, I found strong evidence for major, sustained, population collapses of two urchins, one large predatory gastropod and a reef-building gastropod. Furthermore, of 59 molluscan species once-described in the taxonomic literature as common on Levant reefs, 38 were not found in the present-day surveys, and there was a total domination of non-indigenous species in molluscan assemblages. Temperature trends indicate an exceptional warming of the coastal waters in the past three decades. Though speculative at this stage, the fast rise in SST may have helped pushing these invertebrates beyond their physiological tolerance limits leading to population collapses and possible extirpations. If so, these collapses may indicate the initiation of a multi-species range contraction at the Mediterranean southeastern edge that may spread westward with additional warming. PMID:27853237

Cockpit Window Edge Proximity Effects on Judgements of Horizon Vertical Displacement

NASA Technical Reports Server (NTRS)

Haines, R. F.

1984-01-01

To quantify the influence of a spatially fixed edge on vertical displacement threshold, twenty-four males (12 pilots, 12 non-pilots) were presented a series of forced choice, paired comparison trials in which a 32 deg arc wide, thin, luminous horizontal stimulus line moved smoothly downward through five angles from a common starting position within a three second-long period. The five angles were 1.4, 1.7, 2, 2.3, and 2.6 deg. Each angle was presented paired with itself and the other four angles in all combinations in random order. For each pair of trials the observer had to choose which trial possessed the largest displacement. A confidence response also was made. The independent variable was the angular separation between the lower edge of a stable 'window' aperture through which the stimulus was seen to move and the lowest position attained by the stimulus. It was found that vertical displacement accuracy is inversely related to the angle separating the stimulus and the fixed window edge (p = .05). In addition, there is a strong tendency for pilot confidence to be lower than that of non-pilots for each of the three angular separations. These results are discussed in erms of selected cockpit features and as they relate to how pilots judge changes in aircraft pitch attitude.

Overview of recent physics results from MAST

NASA Astrophysics Data System (ADS)

Kirk, A.; Adamek, J.; Akers, R. J.; Allan, S.; Appel, L.; Arese Lucini, F.; Barnes, M.; Barrett, T.; Ben Ayed, N.; Boeglin, W.; Bradley, J.; Browning, P. K.; Brunner, J.; Cahyna, P.; Cardnell, S.; Carr, M.; Casson, F.; Cecconello, M.; Challis, C.; Chapman, I. T.; Chapman, S.; Chorley, J.; Conroy, S.; Conway, N.; Cooper, W. A.; Cox, M.; Crocker, N.; Crowley, B.; Cunningham, G.; Danilov, A.; Darrow, D.; Dendy, R.; Dickinson, D.; Dorland, W.; Dudson, B.; Dunai, D.; Easy, L.; Elmore, S.; Evans, M.; Farley, T.; Fedorczak, N.; Field, A.; Fishpool, G.; Fitzgerald, I.; Fox, M.; Freethy, S.; Garzotti, L.; Ghim, Y. C.; Gi, K.; Gibson, K.; Gorelenkova, M.; Gracias, W.; Gurl, C.; Guttenfelder, W.; Ham, C.; Harrison, J.; Harting, D.; Havlickova, E.; Hawkes, N.; Hender, T.; Henderson, S.; Highcock, E.; Hillesheim, J.; Hnat, B.; Horacek, J.; Howard, J.; Howell, D.; Huang, B.; Imada, K.; Inomoto, M.; Imazawa, R.; Jones, O.; Kadowaki, K.; Kaye, S.; Keeling, D.; Klimek, I.; Kocan, M.; Kogan, L.; Komm, M.; Lai, W.; Leddy, J.; Leggate, H.; Hollocombe, J.; Lipschultz, B.; Lisgo, S.; Liu, Y. Q.; Lloyd, B.; Lomanowski, B.; Lukin, V.; Lupelli, I.; Maddison, G.; Madsen, J.; Mailloux, J.; Martin, R.; McArdle, G.; McClements, K.; McMillan, B.; Meakins, A.; Meyer, H.; Michael, C.; Militello, F.; Milnes, J.; Morris, A. W.; Motojima, G.; Muir, D.; Naylor, G.; Nielsen, A.; O'Brien, M.; O'Gorman, T.; O'Mullane, M.; Olsen, J.; Omotani, J.; Ono, Y.; Pamela, S.; Pangione, L.; Parra, F.; Patel, A.; Peebles, W.; Perez, R.; Pinches, S.; Piron, L.; Price, M.; Reinke, M.; Ricci, P.; Riva, F.; Roach, C.; Romanelli, M.; Ryan, D.; Saarelma, S.; Saveliev, A.; Scannell, R.; Schekochihin, A.; Sharapov, S.; Sharples, R.; Shevchenko, V.; Shinohara, K.; Silburn, S.; Simpson, J.; Stanier, A.; Storrs, J.; Summers, H.; Takase, Y.; Tamain, P.; Tanabe, H.; Tanaka, H.; Tani, K.; Taylor, D.; Thomas, D.; Thomas-Davies, N.; Thornton, A.; Turnyanskiy, M.; Valovic, M.; Vann, R.; Van Wyk, F.; Walkden, N.; Watanabe, T.; Wilson, H.; Wischmeier, M.; Yamada, T.; Young, J.; Zoletnik, S.; the MAST Team; the EUROfusion MST1 Team

2017-10-01

New results from MAST are presented that focus on validating models in order to extrapolate to future devices. Measurements during start-up experiments have shown how the bulk ion temperature rise scales with the square of the reconnecting field. During the current ramp-up, models are not able to correctly predict the current diffusion. Experiments have been performed looking at edge and core turbulence. At the edge, detailed studies have revealed how filament characteristics are responsible for determining the near and far scrape off layer density profiles. In the core the intrinsic rotation and electron scale turbulence have been measured. The role that the fast ion gradient has on redistributing fast ions through fishbone modes has led to a redesign of the neutral beam injector on MAST Upgrade. In H-mode the turbulence at the pedestal top has been shown to be consistent with being due to electron temperature gradient modes. A reconnection process appears to occur during edge localized modes (ELMs) and the number of filaments released determines the power profile at the divertor. Resonant magnetic perturbations can mitigate ELMs provided the edge peeling response is maximised and the core kink response minimised. The mitigation of intrinsic error fields with toroidal mode number n  >  1 has been shown to be important for plasma performance.

Brush seal bristle flexure and hard-rub characteristics

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1993-01-01

The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping', and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

Brush seal low surface speed hard-rub characteristics

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1993-01-01

The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping,' and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

Brush seal bristle flexure and hard-rub characteristics

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1992-01-01

The bristles of a 38.1-mm (1.5-in) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping,' and hot spots and streaks were found. With a smooth-plug rotor post-test leakage increased 30 percent over pretest leakage.

Brush seal bristle flexure and hard-rub characteristics

NASA Astrophysics Data System (ADS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1992-08-01

The bristles of a 38.1-mm (1.5-in) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping,' and hot spots and streaks were found. With a smooth-plug rotor post-test leakage increased 30 percent over pretest leakage.

Brush seal bristle flexure and hard-rub characteristics

NASA Astrophysics Data System (ADS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1993-10-01

The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping', and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

Brush seal low surface speed hard-rub characteristics

NASA Astrophysics Data System (ADS)

Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

1993-06-01

The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping,' and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

Leading-edge receptivity for blunt-nose bodies

NASA Technical Reports Server (NTRS)

Kerschen, Edward J.

1991-01-01

This research program investigates boundary-layer receptivity in the leading-edge region for bodies with blunt leading edges. Receptivity theory provides the link between the unsteady distrubance environment in the free stream and the initial amplitudes of the instability waves in the boundary layer. This is a critical problem which must be addressed in order to develop more accurate prediction methods for boundary-layer transition. The first phase of this project examines the effects of leading-edge bluntness and aerodynamic loading for low Mach number flows. In the second phase of the project, the investigation is extended to supersonic Mach numbers. Singular perturbation techniques are utilized to develop an asymptotic theory for high Reynolds numbers. In the first year, the asymptotic theory was developed for leading-edge receptivity in low Mach number flows. The case of a parabolic nose is considered. Substantial progress was made on the Navier-Sotkes computations. Analytical solutions for the steady and unsteady potential flow fields were incorporated into the code, greatly expanding the types of free-stream disturbances that can be considered while also significantly reducing the the computational requirements. The time-stepping algorithm was modified so that the potential flow perturbations induced by the unsteady pressure field are directly introduced throughout the computational domain, avoiding an artificial 'numerical diffusion' of these from the outer boundary. In addition, the start-up process was modified by introducing the transient Stokes wave solution into the downstream boundary conditions.

Seasonality and edge effect determine herbivory risk according to different plant association models.

PubMed

Miranda, M; Díaz, L; Sicilia, M; Cristóbal, I; Cassinello, J

2011-01-01

We report evidence of hierarchical resource selection by large herbivores and plant neighbouring effects in a Mediterranean ecosystem. Plant palatability was assessed according to herbivore foraging decisions. We hypothesize that under natural conditions large herbivores follow a hierarchical foraging pattern, starting at the landscape scale, and then selecting patches and individual plants. A between- and within-patch selection study was carried out in an area formed by scrubland and pasture patches, connected by habitat edges. With regard to between-patch selection, quality-dependent resource selection is reported: herbivores mainly consume pasture in spring and woody plants in winter. Within-patch selection was also observed in scrub habitats, influenced by season, relative patch palatability and edge effect. We defined a Proximity Index (PI) between palatable and unpalatable plants, which allowed verification of neighbouring effects. In spring, when the preferred food resource (i.e. herbs) is abundant, we observed that in habitat edges large herbivores basically select the relatively scarce palatable shrubs, whereas inside scrubland, unpalatable shrub consumption was related to increasing PI. In winter, a very different picture was observed; there was low consumption of palatable species surrounded by unpalatable species in habitat edges, where the latter were more abundant. These outcomes could be explained though different plant associations described in the literature. We conclude that optimal foraging theory provides a conceptual framework behind the observed interactions between plants and large herbivores in Mediterranean ecosystems. © 2010 German Botanical Society and The Royal Botanical Society of the Netherlands.

Timing discriminator using leading-edge extrapolation

DOEpatents

Gottschalk, Bernard

1983-01-01

A discriminator circuit to recover timing information from slow-rising pulses by means of an output trailing edge, a fixed time after the starting corner of the input pulse, which is nearly independent of risetime and threshold setting. This apparatus comprises means for comparing pulses with a threshold voltage; a capacitor to be charged at a certain rate when the input signal is one-third threshold voltage, and at a lower rate when the input signal is two-thirds threshold voltage; current-generating means for charging the capacitor; means for comparing voltage capacitor with a bias voltage; a flip-flop to be set when the input pulse reaches threshold voltage and reset when capacitor voltage reaches the bias voltage; and a clamping means for discharging the capacitor when the input signal returns below one-third threshold voltage.

Harmony as a convergence attractor that minimizes the energy expenditure and variability in physiological gait and the loss of harmony in cerebellar ataxia.

PubMed

Serrao, Mariano; Chini, Giorgia; Iosa, Marco; Casali, Carlo; Morone, Giovanni; Conte, Carmela; Bini, Fabiano; Marinozzi, Franco; Coppola, Gianluca; Pierelli, Francesco; Draicchio, Francesco; Ranavolo, Alberto

2017-10-01

The harmony of the human gait was recently found to be related to the golden ratio value (ϕ). The ratio between the duration of the stance and that of the swing phases of a gait cycle was in fact found to be close to ϕ, which implies that, because of the fractal property of autosimilarity of that number, the gait ratios stride/stance, stance/swing, swing/double support, were not significantly different from one another. We studied a group of patients with cerebellar ataxia to investigate how the differences between their gait ratios and the golden ratio are related to efficiency and stability of their gait, assessed by energy expenditure and stride-to-stride variability, respectively. The gait of 28 patients who were affected by degenerative cerebellar ataxia and of 28 healthy controls was studied using a stereophotogrammetric system. The above mentioned gait ratios, the energy expenditure estimated using the pelvis reconstructed method and the gait variability in terms of the stride length were computed, and their relationships were analyzed. Matching procedures have also been used to avoid multicollinearity biases. The gait ratio values of the patients were farther from the controls (and hence from ϕ), even in speed matched conditions (P=0.011, Cohen's D=0.76), but not when the variability and energy expenditure were matched between the two groups (Cohen's D=0.49). In patients with cerebellar ataxia, the farther the stance-swing ratio was from ϕ, the larger the total mechanical work (R 2 adj =0.64). Further, a significant positive correlation was observed between the difference of the gait ratio from the golden ratio and the severity of the disease (R=0.421, P=0.026). Harmony of gait appears to be a benchmark of physiological gait leading to physiological energy recovery and gait reliability. Neurorehabilitation of patients with ataxia might benefit from the restoration of harmony of their locomotor patterns. Copyright © 2017. Published by Elsevier Ltd.

Kinetic and temporospatial parameters in male and female cats walking over a pressure sensing walkway.

PubMed

Verdugo, Mirela R; Rahal, Sheila C; Agostinho, Felipe S; Govoni, Verônica M; Mamprim, Maria J; Monteiro, Frederico O B

2013-06-27

Several factors may influence kinetic data measurements, including body conformation and body mass. In addition, gender differences in gait pattern have been observed in healthy humans. Therefore, the aim of this study was to compare the kinetic and temporospatial parameters in clinically healthy male and female cats using a pressure-sensitive walkway. Eighteen crossbreed adult cats were divided into two groups: G1 had ten male cats (nine neutered) aged from 1 to 4 years and body mass 3.1-6.8 kg; G2 had eight spayed female cats, aged from 1 to 6 years and body mass 3.3-4.75 kg. The data from the first five valid trials were collected for each cat. A trial was considered valid if the cat maintained a velocity between 0.54-0.74 m/s and acceleration from -0.20 to 0.20 m/s2. The peak vertical force (PVF), vertical impulse (VI), gait cycle time, stance time, swing time, stride length, and percentage body weight distribution among the four limbs were determined. In addition, the lengths of each forelimb and each hind limb were measured using a tape with the animal standing. No significant differences were observed in each group in either the forelimbs or the hind limbs or between the left and right sides for any of the variables. For both groups, the PVF (%BW), the VI, and the percentage body weight distribution were higher at the forelimbs than the hind limbs. The stride length was larger for males; however, the other kinetic and temporospatial variables did not show any statistically significant differences between the groups. The lengths of the forelimbs and hind limbs were larger in the male cats. There was a significant moderate positive correlation between the stride length and the length of the limbs. In conclusion, the only difference observed between male and female cats was the stride length, and this was due to the greater body size of male cats. This difference did not affect other temporospatial or kinetics variables.

Is Moderate Intensity Cycling Sufficient to Induce Cardiorespiratory and Biomechanical Modifications of Subsequent Running?

PubMed

Walsh, Joel A; Dawber, James P; Lepers, Romuald; Brown, Marc; Stapley, Paul J

2017-04-01

Walsh, JA, Dawber, JP, Lepers, R, Brown, M, and Stapley, PJ. Is moderate intensity cycling sufficient to induce cardiorespiratory and biomechanical modifications of subsequent running? J Strength Cond Res 31(4): 1078-1086, 2017-This study sought to determine whether prior moderate intensity cycling is sufficient to influence the cardiorespiratory and biomechanical responses during subsequent running. Cardiorespiratory and biomechanical variables measured after moderate intensity cycling were compared with control running at the same intensity. Eight highly trained, competitive triathletes completed 2 separate exercise tests; (a) a 10-minute control run (no prior cycling) and, (b) a 30-minute transition run (TR) (preceded by 20-minute of variable cadence cycling, i.e., run versus cycle-run). Respiratory, breathing frequency (fb), heart rate (HR), cost of running (Cr), rate constant, stride length, and stride frequency variables were recorded, normalized, and quantified at the mean response time (MRT), third minute, 10th minute (steady state), and overall for the control run (CR) and TR. Cost of running increased (p ≤ 0.05) at all respective times during the TR. The V[Combining Dot Above]E/V[Combining Dot Above]CO2 and respiratory exchange ratio (RER) were significantly (p < 0.01) elevated at the MRT and 10th minute of the TR. Furthermore, overall mean increases were recorded for Cr, V[Combining Dot Above]E, V[Combining Dot Above]E/V[Combining Dot Above]CO2, RER, fb (p < 0.01), and HR (p ≤ 0.05) during the TR. Rate constant values for oxygen uptake were significantly different between CR and TR (0.48 ± 0.04 vs. 0.89 ± 0.15; p < 0.01). Stride length decreased across all recorded points during the TR (p ≤ 0.05) and stride frequency increased at the MRT and 3 minutes (p < 0.01). The findings suggest that at moderate intensity, prior cycling influences the cardiorespiratory response during subsequent running. Furthermore, prior cycling seems to have a sustained effect on the Cr during subsequent running.

Assessing edge cracking resistance in AHSS automotive parts by the Essential Work of Fracture methodology

NASA Astrophysics Data System (ADS)

Frómeta, D.; Tedesco, M.; Calvo, J.; Lara, A.; Molas, S.; Casellas, D.

2017-09-01

Lightweight designs and demanding safety requirements in automotive industry are increasingly promoting the use of Advanced High Strength Steel (AHSS) sheets. Such steels present higher strength (above 800 MPa) but lower ductility than conventional steels. Their great properties allow the reduction of the thickness of automobile structural components without compromising the safety, but also introduce new challenges to parts manufacturers. The fabrication of most cold formed components starts from shear cut blanks and, due to the lower ductility of AHSS, edge cracking problems can appear during forming operations, forcing the stop of the production and slowing down the industrial process. Forming Limit Diagrams (FLD) and FEM simulations are very useful tools to predict fracture problems in zones with high localized strain, but they are not able to predict edge cracking. It has been observed that the fracture toughness, measured through the Essential Work of Fracture (EWF) methodology, is a good indicator of the stretch flangeability in AHSS and can help to foresee this type of fractures. In this work, a serial production automotive component has been studied. The component showed cracks in some flanged edges when using a dual phase steel. It is shown that the conventional approach to explain formability, based on tensile tests and FLD, fails in the prediction of edge cracking. A new approach, based on fracture mechanics, help to solve the problem by selecting steel grades with higher fracture toughness, measured by means of EWF. Results confirmed that fracture toughness, in terms of EWF, can be readily used as a material parameter to rationalize cracking related problems and select AHSS with improved edge cracking resistance.

Greening the Golden Gate National Recreation Area

EPA Pesticide Factsheets

The Golden Gate National Recreation Area was recognized a 2016 Federal Green Challenge Award for making significant strides to reduce its carbon footprint with the goal of becoming a carbon neutral park.

Wisconsin High Schools Learn from New PISA Test: International Comparison Drives Efforts to Improve

ERIC Educational Resources Information Center

Borsuk, Alan J.

2015-01-01

This article explores Kettle Moraine High School's experience of participating in the PISA-based test, known in the U.S. as the OECD Test for Schools. The high school is located on the western edge of Milwaukee. Starting with a trial run in 2012 that involved more than 100 U.S. schools, the OECD Test for Schools has been offered to individual…

Infrared Sensor Readout Design

DTIC Science & Technology

1975-11-01

Line Replaceable Unit LT Level Translator MRT Minimum Resolvable Temperature MTF Modulation Transfer Function PC Printed Circuit SCCCD Surface...reduced, not only will the aliased noise increase, but signal aliasing will also start to occur. Atlbe display level this means that sharp edges could...converted from a quantity ol charge to a voltage- level shift by the action ol the precharge pulse that presets the potential on the output diode node to

Evaluation of an improved technique for lumen path definition and lumen segmentation of atherosclerotic vessels in CT angiography.

PubMed

van Velsen, Evert F S; Niessen, Wiro J; de Weert, Thomas T; de Monyé, Cécile; van der Lugt, Aad; Meijering, Erik; Stokking, Rik

2007-07-01

Vessel image analysis is crucial when considering therapeutical options for (cardio-) vascular diseases. Our method, VAMPIRE (Vascular Analysis using Multiscale Paths Inferred from Ridges and Edges), involves two parts: a user defines a start- and endpoint upon which a lumen path is automatically defined, and which is used for initialization; the automatic segmentation of the vessel lumen on computed tomographic angiography (CTA) images. Both parts are based on the detection of vessel-like structures by analyzing intensity, edge, and ridge information. A multi-observer evaluation study was performed to compare VAMPIRE with a conventional method on the CTA data of 15 patients with carotid artery stenosis. In addition to the start- and endpoint, the two radiologists required on average 2.5 (SD: 1.9) additional points to define a lumen path when using the conventional method, and 0.1 (SD: 0.3) when using VAMPIRE. The segmentation results were quantitatively evaluated using Similarity Indices, which were slightly lower between VAMPIRE and the two radiologists (respectively 0.90 and 0.88) compared with the Similarity Index between the radiologists (0.92). The evaluation shows that the improved definition of a lumen path requires minimal user interaction, and that using this path as initialization leads to good automatic lumen segmentation results.

Analysis of a swimmer's hand and forearm in impulsive start from rest using computational fluid dynamics in unsteady flow conditions.

PubMed

Samson, M; Monnet, T; Bernard, A; Lacouture, P; David, L

2018-01-23

The propulsive forces generated by the hands and arms of swimmers have so far been determined essentially by quasi-steady approaches. This study aims to quantify the temporal dependence of the hydrodynamic forces for a simple translation movement: an impulsive start from rest. The study, carried out in unsteady numerical simulation, couples the calculation of the lift and the drag on an expert swimmer hand-forearm model with visualizations of the flow and flow vortex structure analysis. The results of these simulations show that the hand and forearm hydrodynamic forces should be studied from an unsteady approach because the quasi-steady model is inadequate. It also appears that the delayed stall effect generates higher circulatory forces during a short translation at high angle of attack than forces calculated under steady state conditions. During this phase the hand force coefficients are approximately twice as large as those of the forearm. The total force coefficients are highest for angles of attack between 40° and 60°. For the same angle of attack, the forces produced when the leading edge is the thumb side are slightly greater than those produced when the leading edge is the little finger side. Copyright © 2017 Elsevier Ltd. All rights reserved.

An improved panel method for the solution of three-dimensional leading-edge vortex flows. Volume 1: Theory document

NASA Technical Reports Server (NTRS)

Johnson, F. T.; Lu, P.; Tinoco, E. N.

1980-01-01

An improved panel method for the solution of three dimensional flow and wing and wing-body combinations with leading edge vortex separation is presented. The method employs a three dimensional inviscid flow model in which the configuration, the rolled-up vortex sheets, and the wake are represented by quadratic doublet distributions. The strength of the singularity distribution as well as shape and position of the vortex spirals are computed in an iterative fashion starting with an assumed initial sheet geometry. The method calculates forces and moments as well as detail surface pressure distributions. Improvements include the implementation of improved panel numerics for the purpose of elimination the highly nonlinear effects of ring vortices around double panel edges, and the development of a least squares procedure for damping vortex sheet geometry update instabilities. A complete description of the method is included. A variety of cases generated by the computer program implementing the method are presented which verify the mathematical assumptions of the method and which compare computed results with experimental data to verify the underlying physical assumptions made by the method.

Local structural effects in Sr 3NiRhO 6 across magnetic transitions

DOE PAGES

Singh, Navneet; Khalid, S.; Bindu, R.

2016-04-06

Here, we investigate the temperature dependence of the structural parameters of quasi-one-dimensional Sr 3NiRhO 6 across the region of magnetic phase transitions using Ni K-edge and Sr K-edge x-ray absorption spectroscopy (XAS). The features in the x-ray absorption near-edge region are identified using multiple scattering calculations. The temperature-dependent extended x-ray absorption fine structure (EXAFS) studies show that the setting of the intra-chain super exchange interaction starts at ~200 K, which is well above the first transition temperature (45 K) revealed by magnetic susceptibility studies. The onset of the inter-chain super–super exchange interaction appears to be at ~125 K. Interestingly, themore » role played by direct exchange interaction between the Ni 3d and Rh 4d states in stabilising the magnetic interaction is less significant. The present results shed light on the generic features exhibited by isostructural compounds and may help in identifying the magnetic exchange pathways useful for understanding the unusual properties exhibited by such compounds.« less

Two-dimensional topological insulators with large bulk energy gap

NASA Astrophysics Data System (ADS)

Yang, Z. Q.; Jia, Jin-Feng; Qian, Dong

2016-11-01

Two-dimensional (2D) topological insulators (TIs, or quantum spin Hall insulators) are special insulators that possess bulk 2D electronic energy gap and time-reversal symmetry protected one-dimensional (1D) edge state. Carriers in the edge state have the property of spin-momentum locking, enabling dissipation-free conduction along the 1D edge. The existence of 2D TIs was confirmed by experiments in semiconductor quantum wells. However, the 2D bulk gaps in those quantum wells are extremely small, greatly limiting potential application in future electronics and spintronics. Despite this limitation, 2D TIs with a large bulk gap attracted plenty of interest. In this paper, recent progress in searching for TIs with a large bulk gap is reviewed briefly. We start by introducing some theoretical predictions of these new materials and then discuss some recent important achievements in crystal growth and characterization. Project supported by the National Natural Science Foundation of China (Grant Nos. U1632272, 11574201, and 11521404). D. Q. acknowledges support from the Changjiang Scholars Program, China and the Program for Professor of Special Appointment (Eastern Scholar), China.

Electronic and local atomistic structure of MgSiO3 glass under pressure: a study of X-ray Raman scattering at the silicon and magnesium L-edges

NASA Astrophysics Data System (ADS)

Fukui, Hiroshi; Hiraoka, Nozomu

2018-02-01

We applied X-ray Raman scattering technique to MgSiO3 glass, a precursor to magnesium silicate melts, with respect to magnesium and silicon under high-pressure conditions as well as some polycrystalline phases of MgSiO3 at ambient conditions. We also performed ab initio calculations to interpret the X-ray Raman spectra. Experimentally obtained silicon L-edge spectra indicate that the local environment around silicon started changing at pressure above 10 GPa, where the electronic structure of oxygen is known to change. In contrast, the shape of the magnesium L-edge spectrum changed below 10 GPa. This indicates that the magnesium sites in MgSiO3 glass first distort and that the local structure around magnesium shows a wide variation under pressure. The framework structure consisting of silicon and oxygen changed above 10 GPa, where the coordination number of silicon was more than four. Our results imply that 6-oxygen-coordinated silicon was formed above 20 GPa.

Fabrication of lithium/C-103 alloy heat pipes for sharp leading edge cooling

NASA Astrophysics Data System (ADS)

Ai, Bangcheng; Chen, Siyuan; Yu, Jijun; Lu, Qin; Han, Hantao; Hu, Longfei

2018-05-01

In this study, lithium/C-103 alloys heat pipes are proposed for sharp leading edge cooling. Three models of lithium/C-103 alloy heat pipes were fabricated. And their startup properties were tested by radiant heat tests and aerothermal tests. It is found that the startup temperature of lithium heat pipe was about 860 °C. At 1000 °C radiant heat tests, the operating temperature of lithium/C-103 alloy heat pipe is lower than 860 °C. Thus, startup failure occurs. At 1100 °C radiant heat tests and aerothermal tests, the operating temperature of lithium/C-103 alloy heat pipe is higher than 860 °C, and the heat pipe starts up successfully. The startup of lithium/C-103 alloy heat pipe decreases the leading edge temperature effectively, which endows itself good ablation resistance. After radiant heat tests and aerothermal tests, all the heat pipe models are severely oxidized because of the C-103 poor oxidation resistance. Therefore, protective coatings are required for further applications of lithium/C-103 alloy heat pipes.

Development and exploration of a new methodology for the fitting and analysis of XAS data.

PubMed

Delgado-Jaime, Mario Ulises; Kennepohl, Pierre

2010-01-01

A new data analysis methodology for X-ray absorption near-edge spectroscopy (XANES) is introduced and tested using several examples. The methodology has been implemented within the context of a new Matlab-based program discussed in a companion related article [Delgado-Jaime et al. (2010), J. Synchrotron Rad. 17, 132-137]. The approach makes use of a Monte Carlo search method to seek appropriate starting points for a fit model, allowing for the generation of a large number of independent fits with minimal user-induced bias. The applicability of this methodology is tested using various data sets on the Cl K-edge XAS data for tetragonal CuCl(4)(2-), a common reference compound used for calibration and covalency estimation in M-Cl bonds. A new background model function that effectively blends together background profiles with spectral features is an important component of the discussed methodology. The development of a robust evaluation function to fit multiple-edge data is discussed and the implications regarding standard approaches to data analysis are discussed and explored within these examples.

Development and exploration of a new methodology for the fitting and analysis of XAS data

PubMed Central

Delgado-Jaime, Mario Ulises; Kennepohl, Pierre

2010-01-01

A new data analysis methodology for X-ray absorption near-edge spectroscopy (XANES) is introduced and tested using several examples. The methodology has been implemented within the context of a new Matlab-based program discussed in a companion related article [Delgado-Jaime et al. (2010 ▶), J. Synchrotron Rad. 17, 132–137]. The approach makes use of a Monte Carlo search method to seek appropriate starting points for a fit model, allowing for the generation of a large number of independent fits with minimal user-induced bias. The applicability of this methodology is tested using various data sets on the Cl K-edge XAS data for tetragonal CuCl4 2−, a common reference compound used for calibration and covalency estimation in M—Cl bonds. A new background model function that effectively blends together background profiles with spectral features is an important component of the discussed methodology. The development of a robust evaluation function to fit multiple-edge data is discussed and the implications regarding standard approaches to data analysis are discussed and explored within these examples. PMID:20029120

Multiphase Oscillator Using Traveling Pulses Developed in a System of Transmission Lines with Regularly Spaced Resonant-tunneling Diodes

NASA Astrophysics Data System (ADS)

Narahara, Koichi

2017-06-01

A scheme is proposed for generating multiphase oscillatory signals in millimeter-wave frequencies based on the dynamics of a traveling pulse developed in a closed transmission line periodically loaded with resonant-tunneling diodes (RTDs) that is coupled with several straight RTD lines. When supplied with an appropriate voltage at the end of an RTD line, a pulse edge is shown to exhibit a spatially extended limit-cycle oscillation on the line. We consider the case where several RTD lines are connected halfway to a closed one at even intervals. In this case, the oscillatory edge developed in each straight RTD line is mutually synchronized such that a pulse-shaped rotary traveling wave develops on the closed RTD line. The oscillating edge on each straight line is also synchronized with the traveling pulse on the closed line, such that the leading edge of the traveling pulse on the closed line and the forward edge on the straight line pass the cross point simultaneously. As a result, when N L straight lines are connected to the closed line, the phase difference between two adjacent oscillatory edges becomes 2 π/ N L . On the other hand, the trailing edge of the traveling pulse at the cross point breaks the voltage wave on the straight line into two pieces, one of which travels forward to form a solitary wave and the other of which travels backward to reach the input end, where it is reflected and starts to travel forward and this forward moving edge is supposed to be synchronized with the leading edge of the traveling pulse. It means that a back-and-forth edge and a forward-moving solitary wave develop periodically on each straight line. Because the time required for the traveling pulse to go around the closed line must be coincident with the period of the edge oscillation on each straight line, a unique traveling pulse cannot synchronize with each oscillating edge when the cell size of the closed line becomes large, resulting in the development of multiple traveling pulses on the closed line. In this paper, the design criteria are discussed concerning the connecting point between the straight and closed lines, the number of straight lines, and the size of the closed line. In addition, we describe several measurement results that validate the essential properties of the traveling pulse and then show several results of full-wave analysis of a monolithically integrated RTD line.

Diagnosis and treatment of lumbosacral discospondylitis in a calf

PubMed Central

2011-01-01

Background The aim of this case report was to describe the clinical findings, treatment and outcome of lumbosacral discospondylitis in a calf. Case Presentation A 5.5-month-old calf was presented with difficulty in rising, a stiff and slightly ataxic gait in the hind limbs and a shortened stride. The lumbosacral region was severely painful on palpation. Radiographic examination confirmed lumbosacral discospondylitis. Medical treatment with stall rest was instituted over six weeks. Radiographic and ultrasonographic follow-up examinations showed lysis of the endplates initially, then collapse of the intervertebral space at the lumbosacral junction and progressive sclerosis in the periphery of the lytic zones. Four weeks after institution of treatment, the calf could rise normally and the general condition gradually had returned to normal. The calf was discharged after 6 weeks and was sound at 3.5 months clinical and radiographic follow up examination. Thereafter, it was kept on alpine pastures without problems and was pregnant 1 year after the last examination. Conclusions This report shows that recovery from lumbosacral discospondylitis is possible in heifers, provided that treatment is started before major neurologic deficits have developed and is continued for an extended period of time. PMID:21910913

Continuous relative phase variability during an exhaustive run in runners with a history of iliotibial band syndrome.

PubMed

Miller, Ross H; Meardon, Stacey A; Derrick, Timothy R; Gillette, Jason C

2008-08-01

Previous research has proposed that a lack of variability in lower extremity coupling during running is associated with pathology. The purpose of the study was to evaluate lower extremity coupling variability in runners with and without a history of iliotibial band syndrome (ITBS) during an exhaustive run. Sixteen runners ran to voluntary exhaustion on a motorized treadmill while a motion capture system recorded reflective marker locations. Eight runners had a history of ITBS. At the start and end of the run, continuous relative phase (CRP) angles and CRP variability between strides were calculated for key lower extremity kinematic couplings. The ITBS runners demonstrated less CRP variability than controls in several couplings between segments that have been associated with knee pain and ITBS symptoms, including tibia rotation-rearfoot motion and rearfoot motion-thigh ad/abduction, but more variability in knee flexion/extension-foot ad/abduction. The ITBS runners also demonstrated low variability at heel strike in coupling between rearfoot motion-tibia rotation. The results suggest that runners prone to ITBS use abnormal segmental coordination patterns, particular in couplings involving thigh ad/abduction and tibia internal/external rotation. Implications for variability in injury etiology are suggested.

Tribal Lands Cleanup and Spill Prevention Programs

EPA Pesticide Factsheets

EPA takes strides to prevent and cleanup contamination and contaminated sites located on or near Tribal lands. Our programs work hand-in-hand with tribes to ensure we protect their health and the environment.

Molecule by molecule, the physics and chemistry of life: SMB 2007.

PubMed

Block, Steven M; Larson, Matthew H; Greenleaf, William J; Herbert, Kristina M; Guydosh, Nicholas R; Anthony, Peter C

2007-04-01

Interdisciplinary work in the life sciences at the boundaries of biology, chemistry and physics is making enormous strides. This progress was showcased at the recent Single Molecule Biophysics conference.

Performance plan : fiscal year 2006-2007

DOT National Transportation Integrated Search

2006-01-01

The Federal Highway Administration (FHWA) Office of Research, Development, and Technology (RD&T) made signifi cant strides in enhancing mobility and developing solutions to many of the Nations most pressing highway transportation needs. This Perfo...

Physiological work performance in chronic low back disability: effects of a progressive activity program.

PubMed

Thomas, L K; Hislop, H J; Waters, R L

1980-04-01

Fifteen patients were tested before and after treatment in a multifaceted inpatient program for chronic low back pain to determine if a gradually progressive activity program affected gait performance and physiological capacity. Before treatment, all patients demonstrated decreased physiological conditioning by higher-than-expected values for oxygen consumption and heart rate and by lower-than-normal gait velocity, stride length, and cadence. After treatment, an increase in mean walking velocity of 19 meters/minute reflected parallel gains in cadence and stride length. Improved mechanical performance resulted in improved "energetics." Energy spent per unit of distance walked decreased by 18 percent after treatment, providing a useful measure of increased physiological efficiency. Results indicated that patients with chronic low back disability can derive significant conditioning effects from an exercise program based on general function.

Automated health alerts from Kinect-based in-home gait measurements.

PubMed

Stone, Erik E; Skubic, Marjorie; Back, Jessica

2014-01-01

A method for automatically generating alerts to clinicians in response to changes in in-home gait parameters is investigated. Kinect-based gait measurement systems were installed in apartments in a senior living facility. The systems continuously monitored the walking speed, stride time, and stride length of apartment residents. A framework for modeling uncertainty in the residents' gait parameter estimates, which is critical for robust change detection, is developed; along with an algorithm for detecting changes that may be clinically relevant. Three retrospective case studies, of individuals who had their gait monitored for periods ranging from 12 to 29 months, are presented to illustrate use of the alert method. Evidence suggests that clinicians could be alerted to health changes at an early stage, while they are still small and interventions may be most successful. Additional potential uses are also discussed.

Influence of patellofemoral bracing on pain, knee extensor torque, and gait function in females with patellofemoral pain.

PubMed

Powers, Christopher M; Doubleday, Kathryn L; Escudero, Carina

2008-01-01

Our purpose was to evaluate the effects of a patellofemoral brace on pain response, knee extensor torque production, and gait function in females with patellofemoral pain (PFP). Sixteen females between the ages of 14 and 46 with diagnosis of PFP participated. Knee extensor torque was measured by using a LIDO isokinetic dynamometer. Pain levels were documented by using the Visual Analog Pain Scale. Stride characteristics during the conditions of free walk, fast walk, ascend stairs, descend stairs, ascend ramp, and descend ramp were obtained with a stride analyzer unit. EMG activity of the vasti musculature was recorded by using indwelling, bipolar, wire electrodes. Knee joint motion was assessed by using a VICON motion analysis system. All testing was performed with and without the Bauerfeind Genutrain P3 patellofemoral brace. There were no significant differences in torque production, pain levels, and stride characteristics between braced and non-braced trials. In addition, there were no significant differences in mean vasti EMG between braced and non-braced trials. When averaged across all conditions, a small but statistically significant increase in knee flexion was found during the braced trials. Although the current study did not find significant improvements in the clinical measures evaluated, 8 of the 16 subjects did experience a decrease in knee pain. This finding suggests that certain patients with PFP may respond favorably to bracing, and criteria must be established to determine which patients would best benefit from such an intervention.

Comparative abilities of Microsoft Kinect and Vicon 3D motion capture for gait analysis.

PubMed

Pfister, Alexandra; West, Alexandre M; Bronner, Shaw; Noah, Jack Adam

2014-07-01

Biomechanical analysis is a powerful tool in the evaluation of movement dysfunction in orthopaedic and neurologic populations. Three-dimensional (3D) motion capture systems are widely used, accurate systems, but are costly and not available in many clinical settings. The Microsoft Kinect™ has the potential to be used as an alternative low-cost motion analysis tool. The purpose of this study was to assess concurrent validity of the Kinect™ with Brekel Kinect software in comparison to Vicon Nexus during sagittal plane gait kinematics. Twenty healthy adults (nine male, 11 female) were tracked while walking and jogging at three velocities on a treadmill. Concurrent hip and knee peak flexion and extension and stride timing measurements were compared between Vicon and Kinect™. Although Kinect measurements were representative of normal gait, the Kinect™ generally under-estimated joint flexion and over-estimated extension. Kinect™ and Vicon hip angular displacement correlation was very low and error was large. Kinect™ knee measurements were somewhat better than hip, but were not consistent enough for clinical assessment. Correlation between Kinect™ and Vicon stride timing was high and error was fairly small. Variability in Kinect™ measurements was smallest at the slowest velocity. The Kinect™ has basic motion capture capabilities and with some minor adjustments will be an acceptable tool to measure stride timing, but sophisticated advances in software and hardware are necessary to improve Kinect™ sensitivity before it can be implemented for clinical use.

Gait cycle analysis: parameters sensitive for functional evaluation of peripheral nerve recovery in rat hind limbs.

PubMed

Rui, Jing; Runge, M Brett; Spinner, Robert J; Yaszemski, Michael J; Windebank, Anthony J; Wang, Huan

2014-10-01

Video-assisted gait kinetics analysis has been a sensitive method to assess rat sciatic nerve function after injury and repair. However, in conduit repair of sciatic nerve defects, previously reported kinematic measurements failed to be a sensitive indicator because of the inferior recovery and inevitable joint contracture. This study aimed to explore the role of physiotherapy in mitigating joint contracture and to seek motion analysis indices that can sensitively reflect motor function. Data were collected from 26 rats that underwent sciatic nerve transection and conduit repair. Regular postoperative physiotherapy was applied. Parameters regarding step length, phase duration, and ankle angle were acquired and analyzed from video recording of gait kinetics preoperatively and at regular postoperative intervals. Stride length ratio (step length of uninjured foot/step length of injured foot), percent swing of the normal paw (percentage of the total stride duration when the uninjured paw is in the air), propulsion angle (toe-off angle subtracted by midstance angle), and clearance angle (ankle angle change from toe off to midswing) decreased postoperatively comparing with baseline values. The gradual recovery of these measurements had a strong correlation with the post-nerve repair time course. Ankle joint contracture persisted despite rigorous physiotherapy. Parameters acquired from a 2-dimensional motion analysis system, that is, stride length ratio, percent swing of the normal paw, propulsion angle, and clearance angle, could sensitively reflect nerve function impairment and recovery in the rat sciatic nerve conduit repair model despite the existence of joint contractures.

Effects of Nordic walking and walking on spatiotemporal gait parameters and ground reaction force.

PubMed

Park, Seung Kyu; Yang, Dae Jung; Kang, Yang Hun; Kim, Je Ho; Uhm, Yo Han; Lee, Yong Seon

2015-09-01

[Purpose] The purpose of this study was to investigate the effects of Nordic walking and walking on spatiotemporal gait parameters and ground reaction force. [Subjects] The subjects of this study were 30 young adult males, who were divided into a Nordic walking group of 15 subjects and a walking group of 15 subjects. [Methods] To analyze the spatiotemporal parameters and ground reaction force during walking in the two groups, the six-camera Vicon MX motion analysis system was used. The subjects were asked to walk 12 meters using the more comfortable walking method for them between Nordic walking and walking. After they walked 12 meters more than 10 times, their most natural walking patterns were chosen three times and analyzed. To determine the pole for Nordic walking, each subject's height was multiplied by 0.68. We then measured the spatiotemporal gait parameters and ground reaction force. [Results] Compared with the walking group, the Nordic walking group showed an increase in cadence, stride length, and step length, and a decrease in stride time, step time, and vertical ground reaction force. [Conclusion] The results of this study indicate that Nordic walking increases the stride and can be considered as helping patients with diseases affecting their gait. This demonstrates that Nordic walking is more effective in improving functional capabilities by promoting effective energy use and reducing the lower limb load, because the weight of the upper and lower limbs is dispersed during Nordic walking.

Molecule by molecule, the physics and chemistry of life: SMB 2007

PubMed Central

Block, Steven M; Larson, Matthew H; Greenleaf, William J; Herbert, Kristina M; Guydosh, Nicholas R; Anthony, Peter C

2007-01-01

Interdisciplinary work in the life sciences at the boundaries of biology, chemistry and physics is making enormous strides. This progress was showcased at the recent Single Molecule Biophysics conference. PMID:17372599

78 FR 61358 - Mylan, Inc., Agila Specialties Global Pte. Limited, Agila Specialties Private Limited and Strides...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-03

... multiple sclerosis. Five firms currently supply the market for methotrexate sodium preservative- free... branded manufacturer. Once multiple generic suppliers enter a market, the branded drug manufacturer...

Method for contour extraction for object representation

DOEpatents

Skourikhine, Alexei N.; Prasad, Lakshman

2005-08-30

Contours are extracted for representing a pixelated object in a background pixel field. An object pixel is located that is the start of a new contour for the object and identifying that pixel as the first pixel of the new contour. A first contour point is then located on the mid-point of a transition edge of the first pixel. A tracing direction from the first contour point is determined for tracing the new contour. Contour points on mid-points of pixel transition edges are sequentially located along the tracing direction until the first contour point is again encountered to complete tracing the new contour. The new contour is then added to a list of extracted contours that represent the object. The contour extraction process associates regions and contours by labeling all the contours belonging to the same object with the same label.

Study of viscous flow about airfoils by the integro-differential method

NASA Technical Reports Server (NTRS)

Wu, J. C.; Sampath, S.

1975-01-01

An integro-differential method was used for numerically solving unsteady incompressible viscous flow problems. A computer program was prepared to solve the problem of an impulsively started 9% thick symmetric Joukowski airfoil at an angle of attack of 15 deg and a Reynolds number of 1000. Some of the results obtained for this problem were discussed and compared with related work completed previously. Two numerical procedures were used, an Alternating Direction Implicit (ADI) method and a Successive Line Relaxation (SLR) method. Generally, the ADI solution agrees well with the SLR solution and with previous results are stations away from the trailing edge. At the trailing edge station, the ADI solution differs substantially from previous results, while the vorticity profiles obtained from the SLR method there are in good qualitative agreement with previous results.

Timing discriminator using leading-edge extrapolation

DOEpatents

Gottschalk, B.

1981-07-30

A discriminator circuit to recover timing information from slow-rising pulses by means of an output trailing edge, a fixed time after the starting corner of the input pulse, which is nearly independent of risetime and threshold setting is described. This apparatus comprises means for comparing pulses with a threshold voltage; a capacitor to be charged at a certain rate when the input signal is one-third threshold voltage, and at a lower rate when the input signal is two-thirds threshold voltage; current-generating means for charging the capacitor; means for comparing voltage capacitor with a bias voltage; a flip-flop to be set when the input pulse reaches threshold voltage and reset when capacitor voltage reaches the bias voltage; and a clamping means for discharging the capacitor when the input signal returns below one-third threshold voltage.

Strontium Concentrations in Corrosion Products from Residential Drinking Water Distribution Systems

DTIC Science & Technology

2013-04-22

associated with iron corrosion products that, if disturbed, could increase Sr2+ concentrations above the 0.3 μg L -1 US EPA reporting threshold...water travels through and interacts with the DWDS infrastructure and associated corrosion products.7,8 Starting in 2013, reporting to the US EPA is...techniques, Sr2+ binding mechanisms within the corrosion products were examined using in situ micro X-ray adsorption near edge spectroscopy (μ- XANES

Iron L2,3-Edge X-ray Absorption and X-ray Magnetic Circular Dichroism Studies of Molecular Iron Complexes with Relevance to the FeMoco and FeVco Active Sites of Nitrogenase

PubMed Central

2017-01-01

Herein, a systematic study of a series of molecular iron model complexes has been carried out using Fe L2,3-edge X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopies. This series spans iron complexes of increasing complexity, starting from ferric and ferrous tetrachlorides ([FeCl4]−/2–), to ferric and ferrous tetrathiolates ([Fe(SR)4]−/2–), to diferric and mixed-valent iron–sulfur complexes [Fe2S2R4]2–/3–. This test set of compounds is used to evaluate the sensitivity of both Fe L2,3-edge XAS and XMCD spectroscopy to oxidation state and ligation changes. It is demonstrated that the energy shift and intensity of the L2,3-edge XAS spectra depends on both the oxidation state and covalency of the system; however, the quantitative information that can be extracted from these data is limited. On the other hand, analysis of the Fe XMCD shows distinct changes in the intensity at both L3 and L2 edges, depending on the oxidation state of the system. It is also demonstrated that the XMCD intensity is modulated by the covalency of the system. For mononuclear systems, the experimental data are correlated with atomic multiplet calculations in order to provide insights into the experimental observations. Finally, XMCD is applied to the tetranuclear heterometal–iron–sulfur clusters [MFe3S4]3+/2+ (M = Mo, V), which serve as structural analogues of the FeMoco and FeVco active sites of nitrogenase. It is demonstrated that the XMCD data can be utilized to obtain information on the oxidation state distribution in complex clusters that is not readily accessible for the Fe L2,3-edge XAS data alone. The advantages of XMCD relative to standard K-edge and L2,3-edge XAS are highlighted. This study provides an important foundation for future XMCD studies on complex (bio)inorganic systems. PMID:28653855

Survival probability of an edge Majorana in a one-dimensional p-wave superconducting chain under sudden quenching of parameters

NASA Astrophysics Data System (ADS)

Rajak, Atanu; Dutta, Amit

2014-04-01

We consider the temporal evolution of a zero-energy edge Majorana of a spinless p-wave superconducting chain following a sudden change of a parameter of the Hamiltonian. Starting from one of the topological phases that has an edge Majorana, the system is suddenly driven to the other topological phase or to the (topologically) trivial phases and to the quantum critical points (QCPs) separating these phases. The survival probability of the initial edge Majorana as a function of time is studied following the quench. Interestingly when the chain is quenched to the QCP, we find a nearly perfect oscillation of the survival probability, indicating that the Majorana travels back and forth between two ends, with a time period that scales with the system size. We also generalize to the situation when there is a next-nearest-neighbor hopping in a superconducting chain and there results in a pair of edge Majorana at each end of the chain in the topological phase. We show that the frequency of oscillation of the survival probability gets doubled in this case. We also perform an instantaneous quenching of the Hamiltonian (with two Majorana modes at each end of the chain) to an another Hamiltonian which has only one Majorana mode in equilibrium; the MSP shows oscillations as a function of time with a noticeable decay in the amplitude. On the other hand for a quenching which is reverse to the previous one, the MSP decays rapidly and stays close to zero with fluctuations in amplitude.

Increased electron temperature turbulence during suppression of edge localized mode by resonant magnetic perturbations in the DIII-D tokamak [Increased electron temperature turbulence during edge localized mode (ELM) suppression by resonant magnetic perturbations (RMPs) in the DIII-D tokamak

DOE PAGES

Sung, Choongki; Wang, G.; Rhodes, Terry L.; ...

2017-11-16

We report the first observation of increased edge electron temperature turbulence correlated with changes in gradients and the ELM suppression time which occurs after the application of resonant magnetic perturbations (RMP) on DIII-D H-mode plasmas. This increase (T ~ e/T e approximately doubles) occurs in the region extending from the top of the pedestal outward to the upper part of the edge steep gradient region. This is significant as it is consistent with increased turbulence driven transport potentially replacing some part of the edge localized mode (ELM) driven transport. However, temperature turbulence does not change with the initial RMP applicationmore » while ELMs are still present, indicating the turbulence changes are not causative in the development of ELM suppression or initial profile evolution with RMP – but rather a response to these effects. This temperature turbulence is broadband and long wavelength, k θρ s < 0.5, where k θ = poloidal wavenumber, ρ s = ion sound gyroradius. As has been reported previously, long wavelength density turbulence (k θρ s < 1.0) in the same location also increases after ELMs were suppressed by the RMP. Since the decrease of the density starts nearly immediately with RMP application, these results suggest that the so-called RMP “density pump-out” is not linked to these long wavelength turbulent transport changes. Comparison with linear stability analysis finds both consistencies and inconsistencies in this important region.« less

Coherence recovery mechanisms of quantum Hall edge states

NASA Astrophysics Data System (ADS)

Goremykina, Anna S.; Sukhorukov, Eugene V.

2018-03-01

This paper is motivated by an unexpected observation in a recent experiment [S. Tewari et al., Phys. Rev. B 93, 035420 (2016)., 10.1103/PhysRevB.93.035420], where a robust coherence recovery, starting from a certain energy, was detected for an electron injected into a quantum Hall edge at a filling factor of 2. After passing through a quantum dot, the electron then tunnels into the edge with a subsequent propagation towards a symmetric Mach-Zender interferometer (MZI). Afterwards, the visibility of Aharonov-Bohm (AB) oscillations is measured. An earlier study, based on the bosonization framework with a linear spectrum of the edge excitations, predicted a decay of the visibility with increasing energy. We associate this result with the destructive interference of the two quasiparticles (charge and neutral modes), formed at the edge out of the incoming electron wave packet (WP). However, in reality, it might be suppressed due to an imbalance between the quasiparticles, for instance, in the presence of dispersion and/or dissipation. This idea could also be explored further experimentally by applying a periodic potential to the arms of the MZI and thus creating the imbalance. Yet another possibility to restore phase coherence, also based on dispersion and dissipation, accounts for a drop in the energy density of the electron WP by the time it arrives at the interferometer, leading to a significantly smaller dephasing inside it. We then show that the energy density is defined by a parameter completely independent of the injected energy, which naturally explains the emergence of threshold energy in the experiment.

Increased electron temperature turbulence during suppression of edge localized mode by resonant magnetic perturbations in the DIII-D tokamak [Increased electron temperature turbulence during edge localized mode (ELM) suppression by resonant magnetic perturbations (RMPs) in the DIII-D tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sung, Choongki; Wang, G.; Rhodes, Terry L.

We report the first observation of increased edge electron temperature turbulence correlated with changes in gradients and the ELM suppression time which occurs after the application of resonant magnetic perturbations (RMP) on DIII-D H-mode plasmas. This increase (T ~ e/T e approximately doubles) occurs in the region extending from the top of the pedestal outward to the upper part of the edge steep gradient region. This is significant as it is consistent with increased turbulence driven transport potentially replacing some part of the edge localized mode (ELM) driven transport. However, temperature turbulence does not change with the initial RMP applicationmore » while ELMs are still present, indicating the turbulence changes are not causative in the development of ELM suppression or initial profile evolution with RMP – but rather a response to these effects. This temperature turbulence is broadband and long wavelength, k θρ s < 0.5, where k θ = poloidal wavenumber, ρ s = ion sound gyroradius. As has been reported previously, long wavelength density turbulence (k θρ s < 1.0) in the same location also increases after ELMs were suppressed by the RMP. Since the decrease of the density starts nearly immediately with RMP application, these results suggest that the so-called RMP “density pump-out” is not linked to these long wavelength turbulent transport changes. Comparison with linear stability analysis finds both consistencies and inconsistencies in this important region.« less

Learning about knowledge: A complex network approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fontoura Costa, Luciano da

2006-08-15

An approach to modeling knowledge acquisition in terms of walks along complex networks is described. Each subset of knowledge is represented as a node, and relations between such knowledge are expressed as edges. Two types of edges are considered, corresponding to free and conditional transitions. The latter case implies that a node can only be reached after visiting previously a set of nodes (the required conditions). The process of knowledge acquisition can then be simulated by considering the number of nodes visited as a single agent moves along the network, starting from its lowest layer. It is shown that hierarchicalmore » networks--i.e., networks composed of successive interconnected layers--are related to compositions of the prerequisite relationships between the nodes. In order to avoid deadlocks--i.e., unreachable nodes--the subnetwork in each layer is assumed to be a connected component. Several configurations of such hierarchical knowledge networks are simulated and the performance of the moving agent quantified in terms of the percentage of visited nodes after each movement. The Barabasi-Albert and random models are considered for the layer and interconnecting subnetworks. Although all subnetworks in each realization have the same number of nodes, several interconnectivities, defined by the average node degree of the interconnection networks, have been considered. Two visiting strategies are investigated: random choice among the existing edges and preferential choice to so far untracked edges. A series of interesting results are obtained, including the identification of a series of plateaus of knowledge stagnation in the case of the preferential movement strategy in the presence of conditional edges.« less

Determination of the ground state of an Au-supported FePc film based on the interpretation of Fe K - and L -edge x-ray magnetic circular dichroism measurements

NASA Astrophysics Data System (ADS)

Natoli, Calogero R.; Krüger, Peter; Bartolomé, Juan; Bartolomé, Fernando

2018-04-01

We determine the magnetic ground state of the FePc molecule on Au-supported thin films based on the observed values of orbital anisotropy and spectroscopic x-ray magnetic circular dichroism (XMCD) measurements at the Fe K and L edges. Starting from ab initio molecular orbital multiplet calculations for the isolated molecule, we diagonalize the spin-orbit interaction in the subspace spanned by the three lowest spin triplet states of 3A2 g and 3Eg symmetry in the presence of a saturating magnetic field at a polar angle θ with respect to the normal to the plane of the film, plus an external perturbation representing the effect of the molecules in the stack on the FePc molecule under consideration. We find that the orbital moment of the ground state strongly depends on the magnetic field direction in agreement with the sum rule analysis of the L23-edge XMCD data. We calculate integrals over the XMCD spectra at the Fe K and L23 edges as used in the sum rules and explicitly show that they agree with the expectation values of the orbital moment and effective spin moment of the ground state. On the basis of this analysis, we can rule out alternative candidates proposed in the literature.

Economic effects of access management techniques in North Carolina.

DOT National Transportation Integrated Search

2010-12-21

The NCDOT has made significant strides to reduce collisions and increase capacity along : strategic highway corridors across the state. Efforts have led to the implementation of many : different access management techniques along corridors, such as i...

Integrated urban systems modeling : designing a seamless, comprehensive approach to transportation planning.

DOT National Transportation Integrated Search

2009-01-01

Metropolitan planning agencies face increasingly complex issues in modeling interactions between the built environment and multimodal transportation systems. Although great strides have been made in simulating land use, travel demand, and traffic flo...

Learning, Play, and Your 8- to 12-Month-Old

MedlinePlus

... Staying Safe Videos for Educators Search English Español Learning, Play, and Your 8- to 12-Month-Old ... these next few months. What Is My Child Learning? Your little one will make great strides in ...

Development of pedestrian & bicycle transportation course modules.

DOT National Transportation Integrated Search

2014-05-01

According to a 2012 report by the Alliance for Biking and Walking, crashes involving bicyclists : and/or pedestrians account for almost 15% of all traffic crashes. The states that house STRIDE : consortium universities, including Florida, Alabama, Ge...

Prize for Industrial Applications of Physics Talk: Start-up Company (Ad)Ventures -- the Highs & Lows

NASA Astrophysics Data System (ADS)

Economou, Nicholas

2011-03-01

Each start-up company is a unique enterprise, with its own strengths, weaknesses, challenges and eventual outcome. However, there are many aspects common to all new technology companies, including the need for: 1. An innovative technology edge. 2. A solid product idea. 3. A team with experienced people in at least some of the key jobs. 4. Adequate initial funding to achieve some significant milestones. 5. Patient investors who can persevere through the inevitable hard times. 6. A liquidity/exit strategy clearly articulated from day one. The case studies of how other companies were started and developed can provide useful insights into what may lie ahead for the founders of a new company. Several examples from my own experience will be discussed. While they are all clearly different, there are common threads running through all of these stories. Some thoughts on what went right or wrong, and what could have been done better will be presented.

Effects of glycine on motor performance in rats after traumatic spinal cord injury.

PubMed

Gonzalez-Piña, Rigoberto; Nuño-Licona, Alberto

2007-01-01

It has been reported that glycine improves some functions lost after spinal cord injury (SCI). In order to assess the effects of glycine administration on motor performance after SCI, we used fifteen male Wistar rats distributed into three groups: sham (n = 3), spinal-cord injury (n = 6,) and spinal cord injury + glycine (n = 6). Motor performance was assessed using the beam-walking paradigm and footprint analysis. Results showed that for all animals with spinal-cord injury, scores in the beam-walking increased, which is an indication of increased motor deficit. In addition, footprint analysis showed a decrease in stride length and an increase in stride angle, additional indicators of motor deficit. These effects trended towards recovery after 8 weeks of recording and trended toward improvement by glycine administration; the effect was not significant. These results suggest that glycine replacement alone is not sufficient to improve the motor deficits that occur after SCI.

Development of independent locomotion in children with a severe visual impairment.

PubMed

Hallemans, Ann; Ortibus, Els; Truijen, Steven; Meire, Francoise

2011-01-01

Locomotion of children and adults with a visual impairment (ages 1-44, n = 28) was compared to that of age-related individuals with normal vision (n = 60). Participants walked barefoot at preferred speed while their gait was recorded by a Vicon(®) system. Walking speed, heading angle, step frequency, stride length, step width, stance phase duration and double support time were determined. Differences between groups, relationships with age and possible interaction effects were investigated. With increasing age overall improvements in gait parameters are observed. Differences between groups were a slower walking speed, a shorter stride length, a prolonged duration of stance and of double support in the individuals with a visual impairment. These may be considered either as adaptations to balance problems or as strategies to allow to foot to probe the ground. Copyright © 2011 Elsevier Ltd. All rights reserved.

Lower Limb Rehabilitation Using Patient Data

PubMed Central

Saadat, Mozafar

2016-01-01

The aim of this study is to investigate the performance of a 6-DoF parallel robot in tracking the movement of the foot trajectory of a paretic leg during a single stride. The foot trajectories of nine patients with a paretic leg including both males and females have been measured and analysed by a Vicon system in a gait laboratory. Based on kinematic and dynamic analysis of a 6-DoF UPS parallel robot, an algorithm was developed in MATLAB to calculate the length of the actuators and their required forces during all trajectories. The workspace and singularity points of the robot were then investigated in nine different cases. A 6-DoF UPS parallel robot prototype with high repeatability was designed and built in order to simulate a single stride. Results showed that the robot was capable of tracking all of the trajectories with the maximum position error of 1.2 mm. PMID:27721648

Balance and coordination training, but not endurance training, enhances synaptophysin and neurotrophin-3 immunoreactivity in the lumbar spinal cord after sciatic nerve crush.

PubMed

Bonetti, Leandro Viçosa; Ilha, Jocemar; Schneider, Ana Paula Krauthein; Barbosa, Silvia; Faccioni-Heuser, Maria Cristina

2016-04-01

Numerous rehabilitation treatments have been shown to be useful for peripheral and central restoration after (PNI). After sciatic nerve crush, we investigated 4 weeks of endurance training (ET) and balance and coordination training (BCT) with sciatic function index, hind-paw stride length, and spinal cord dorsal horn synaptophysin and neurotrophin-3 immunoreactivity. Our results demonstrated no significant differences between the non-trained (NT), ET, and BCT groups in sciatic functional index, and in stride-length analysis, but the ET showed higher values compared with the NT group. Synaptophysin immunoreactivity was higher in the BCT group compared with the NT group, and neurotrophin-3 immunoreactivity in the BCT group was greater compared with the other groups. BCT can positively affect spinal cord plasticity after a (PNI), and these modifications are important in the rehabilitation process. © 2015 Wiley Periodicals, Inc.

History of visual systems in the Systems Engineering Simulator

NASA Technical Reports Server (NTRS)

Christianson, David C.

1989-01-01

The Systems Engineering Simulator (SES) houses a variety of real-time computer generated visual systems. The earliest machine dates from the mid-1960's and is one of the first real-time graphics systems in the world. The latest acquisition is the state-of-the-art Evans and Sutherland CT6. Between the span of time from the mid-1960's to the late 1980's, tremendous strides have been made in the real-time graphics world. These strides include advances in both software and hardware engineering. The purpose is to explore the history of the development of these real-time computer generated image systems from the first machine to the present. Hardware advances as well as software algorithm changes are presented. This history is not only quite interesting but also provides us with a perspective with which we can look backward and forward.

Computing the variations in the self-similar properties of the various gait intervals in Parkinson disease patients.

PubMed

Manjeri Keloth, Sana; Arjunan, Sridhar P; Kumar, Dinesh

2017-07-01

This study has investigated the stride, swing, stance and double support intervals of gait for Parkinson's disease (PD) patients with different levels of severity. Self-similar properties of the gait signal were analyzed to investigate the changes in the gait pattern of the healthy and PD patients. To understand the self-similar property, detrended fluctuation analysis was performed. The analysis shows that the PD patients have less defined gait when compared to healthy. The study also shows that among the stance and swing phase of stride interval, the self-similarity is less for swing interval when compared to the stance interval of gait and decreases with the severity of gait. Also, PD patients show decreased self-similar patterns in double support interval of gait. This suggest that there are less rhythmic gait intervals and a sense of urgency to remain in support phase of gait by the PD patients.

Coarse-grained molecular dynamics modeling of the kinetics of lamellar BCP defect annealing

NASA Astrophysics Data System (ADS)

Peters, Andrew J.; Lawson, Richard A.; Nation, Benjamin D.; Ludovice, Peter J.; Henderson, Clifford L.

2015-03-01

Directed self-assembly of block copolymers (BCPs) is a process that has received great interest in the field of nanomanufacturing in the past decade, and great strides towards forming high quality aligned patterns have been made. But state of the art methods still yield defectivities orders of magnitude higher than is necessary in semi-conductor fabrication even though free energy calculations suggest that equilibrium defectivities are much lower than is necessary for economic semi-conductor fabrication. This disparity suggests that the main problem may lie in the kinetics of defect removal. This work uses a coarse-grained model to study the rates, pathways, and dependencies of healing a common defect to give insight into the fundamental processes that control defect healing and give guidance on optimal process conditions for BCP-DSA. It is found that infinitely thick films yield an exponential drop in defect heal rate above χN ~ 30. Below χN ~ 30, the rate of transport was similar to the rate at which the transition state was reached so that the overall rate changed only slightly. The energy barrier in periodic simulations increased with 0.31 χN on average. Thin film simulations show no change in rate associated with the energy barrier below χN ~ 50, and then show an increase in energy barrier scaling with 0.16χN. Thin film simulations always begin to heal at either the free interface or the BCP-underlayer interface where the increased A-B contact area associated with the transition state will be minimized, while the infinitely thick films must start healing in the bulk where the A-B contact area is increased. It is also found that cooperative chain movement is required for the defect to start healing.

Emergence of Complexity in Protein Functions and Metabolic Networks

NASA Technical Reports Server (NTRS)

Pohorille, Andzej

2009-01-01

In modern organisms proteins perform a majority of cellular functions, such as chemical catalysis, energy transduction and transport of material across cell walls. Although great strides have been made towards understanding protein evolution, a meaningful extrapolation from contemporary proteins to their earliest ancestors is virtually impossible. In an alternative approach, the origin of water-soluble proteins was probed through the synthesis of very large libraries of random amino acid sequences and subsequently subjecting them to in vitro evolution. In combination with computer modeling and simulations, these experiments allow us to address a number of fundamental questions about the origins of proteins. Can functionality emerge from random sequences of proteins? How did the initial repertoire of functional proteins diversify to facilitate new functions? Did this diversification proceed primarily through drawing novel functionalities from random sequences or through evolution of already existing proto-enzymes? Did protein evolution start from a pool of proteins defined by a frozen accident and other collections of proteins could start a different evolutionary pathway? Although we do not have definitive answers to these questions, important clues have been uncovered. Considerable progress has been also achieved in understanding the origins of membrane proteins. We will address this issue in the example of ion channels - proteins that mediate transport of ions across cell walls. Remarkably, despite overall complexity of these proteins in contemporary cells, their structural motifs are quite simple, with -helices being most common. By combining results of experimental and computer simulation studies on synthetic models and simple, natural channels, I will show that, even though architectures of membrane proteins are not nearly as diverse as those of water-soluble proteins, they are sufficiently flexible to adapt readily to the functional demands arising during evolution.

Quantitative Gait Markers and Incident Fall Risk in Older Adults

PubMed Central

Holtzer, Roee; Lipton, Richard B.; Wang, Cuiling

2009-01-01

Background Identifying quantitative gait markers of falls in older adults may improve diagnostic assessments and suggest novel intervention targets. Methods We studied 597 adults aged 70 and older (mean age 80.5 years, 62% women) enrolled in an aging study who received quantitative gait assessments at baseline. Association of speed and six other gait markers (cadence, stride length, swing, double support, stride length variability, and swing time variability) with incident fall rate was studied using generalized estimation equation procedures adjusted for age, sex, education, falls, chronic illnesses, medications, cognition, disability as well as traditional clinical tests of gait and balance. Results Over a mean follow-up period of 20 months, 226 (38%) of the 597 participants fell. Mean fall rate was 0.44 per person-year. Slower gait speed (risk ratio [RR] per 10 cm/s decrease 1.069, 95% confidence interval [CI] 1.001–1.142) was associated with higher risk of falls in the fully adjusted models. Among six other markers, worse performance on swing (RR 1.406, 95% CI 1.027–1.926), double-support phase (RR 1.165, 95% CI 1.026–1.321), swing time variability (RR 1.007, 95% CI 1.004–1.010), and stride length variability (RR 1.076, 95% CI 1.030–1.111) predicted fall risk. The associations remained significant even after accounting for cognitive impairment and disability. Conclusions Quantitative gait markers are independent predictors of falls in older adults. Gait speed and other markers, especially variability, should be further studied to improve current fall risk assessments and to develop new interventions. PMID:19349593

A comparative analysis of spectral exponent estimation techniques for 1/fβ processes with applications to the analysis of stride interval time series

PubMed Central

Schaefer, Alexander; Brach, Jennifer S.; Perera, Subashan; Sejdić, Ervin

2013-01-01

Background The time evolution and complex interactions of many nonlinear systems, such as in the human body, result in fractal types of parameter outcomes that exhibit self similarity over long time scales by a power law in the frequency spectrum S(f) = 1/fβ. The scaling exponent β is thus often interpreted as a “biomarker” of relative health and decline. New Method This paper presents a thorough comparative numerical analysis of fractal characterization techniques with specific consideration given to experimentally measured gait stride interval time series. The ideal fractal signals generated in the numerical analysis are constrained under varying lengths and biases indicative of a range of physiologically conceivable fractal signals. This analysis is to complement previous investigations of fractal characteristics in healthy and pathological gait stride interval time series, with which this study is compared. Results The results of our analysis showed that the averaged wavelet coefficient method consistently yielded the most accurate results. Comparison with Existing Methods: Class dependent methods proved to be unsuitable for physiological time series. Detrended fluctuation analysis as most prevailing method in the literature exhibited large estimation variances. Conclusions The comparative numerical analysis and experimental applications provide a thorough basis for determining an appropriate and robust method for measuring and comparing a physiologically meaningful biomarker, the spectral index β. In consideration of the constraints of application, we note the significant drawbacks of detrended fluctuation analysis and conclude that the averaged wavelet coefficient method can provide reasonable consistency and accuracy for characterizing these fractal time series. PMID:24200509

Fractal fluctuations in spatiotemporal variables when walking on a self-paced treadmill.

PubMed

Choi, Jin-Seung; Kang, Dong-Won; Seo, Jeong-Woo; Tack, Gye-Rae

2017-12-08

This study investigated the fractal dynamic properties of stride time (ST), stride length (SL) and stride speed (SS) during walking on a self-paced treadmill (STM) in which the belt speed is automatically controlled by the walking speed. Twelve healthy young subjects participated in the study. The subjects walked at their preferred walking speed under four conditions: STM, STM with a metronome (STM+met), fixed-speed (conventional) treadmill (FTM), and FTM with a metronome (FTM+met). To compare the fractal dynamics between conditions, the mean, variability, and fractal dynamics of ST, SL, and SS were compared. Moreover, the relationship among the variables was examined under each walking condition using three types of surrogates. The mean values of all variables did not differ between the two treadmills, and the variability of all variables was generally larger for STM than for FTM. The use of a metronome resulted in a decrease in variability in ST and SS for all conditions. The fractal dynamic characteristics of SS were maintained with STM, in contrast to FTM, and only the fractal dynamic characteristics of ST disappeared when using a metronome. In addition, the fractal dynamic patterns of the cross-correlated surrogate results were identical to those of all variables for the two treadmills. In terms of the fractal dynamic properties, STM walking was generally closer to overground walking than FTM walking. Although further research is needed, the present results will be useful in research on gait fractal dynamics and rehabilitation. Copyright © 2017 Elsevier Ltd. All rights reserved.

The hippocampus participates in the control of locomotion speed.

PubMed

López Ruiz, J R; Osuna Carrasco, L P; López Valenzuela, C L; Franco Rodríguez, N E; de la Torre Valdovinos, B; Jiménez Estrada, I; Dueñas Jiménez, J M; Dueñas Jiménez, S H

2015-12-17

The hippocampus role in sensory-motor integration remains unclear. In these experiments we study its function in the locomotor control. To establish the connection between the hippocampus and the locomotor system, electrical stimulation in the CA1 region was applied and EMG recordings were obtained. We also evaluated the hindlimbs and forelimbs kinematic patterns in rats with a penetrating injury (PI) in the hippocampus as well as in a cortex-injured group (CI), which served as control. After the PI, tamoxifen a selective estrogen receptor modulator (SERM) that has been described as a neuroprotector and antiinflammatory drug, or vehicle was administered. Electrical stimulation in the hippocampus produces muscle contractions in the contralateral triceps, when 6 Hz or 8 Hz pulse trains were applied. The penetrating injury in the hippocampus reduced the EMG amplitude after the electrical stimulation. At 7 DPI (days post-injury) we observed an increase in the strides speed in all four limbs of the non-treated group, decreasing the correlation percentage of the studied joints. After 15 DPI the strides speed in the non-treated returned to normal. These changes did not occur in the tamoxifen group nor in cortex-injured group. After 30 days, the nontreated group presented a reduction in the number of pyramidal cell layer neurons at the injury site, in comparison to the tam-treated group. The loss of neurons, may cause the interruption of the trisynaptic circuit and changes in the locomotion speed. Tamoxifen preserves the pyramidal neurons after the injury, probably resulting in the strides speed recovery. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

Effects of adding a virtual reality environment to different modes of treadmill walking.

PubMed

Sloot, L H; van der Krogt, M M; Harlaar, J

2014-03-01

Differences in gait between overground and treadmill walking are suggested to result from imposed treadmill speed and lack of visual flow. To counteract this effect, feedback-controlled treadmills that allow the subject to control the belt speed along with an immersive virtual reality (VR) have recently been developed. We studied the effect of adding a VR during both fixed speed (FS) and self-paced (SP) treadmill walking. Nineteen subjects walked on a dual-belt instrumented treadmill with a simple endless road projected on a 180° circular screen. A main effect of VR was found for hip flexion offset, peak hip extension, peak knee extension moment, knee flexion moment gain and ankle power during push off. A consistent interaction effect between VR and treadmill mode was found for 12 out of 30 parameters, although the differences were small and did not exceed 50% of the within subject stride variance. At FS, the VR seemed to slightly improve the walking pattern towards overground walking, with for example a 6.5mm increase in stride length. At SP, gait became slightly more cautious by adding a VR, with a 9.1mm decrease in stride length. Irrespective of treadmill mode, subjects rated walking with the VR as more similar to overground walking. In the context of clinical gait analysis, the effects of VR are too small to be relevant and are outweighed by the gains of adding a VR, such as a more stimulating experience and possibility of augmenting it by real-time feedback. Copyright © 2013 Elsevier B.V. All rights reserved.

High speed galloping in the cheetah (Acinonyx jubatus) and the racing greyhound (Canis familiaris): spatio-temporal and kinetic characteristics.

PubMed

Hudson, Penny E; Corr, Sandra A; Wilson, Alan M

2012-07-15

The cheetah and racing greyhound are of a similar size and gross morphology and yet the cheetah is able to achieve a far higher top speed. We compared the kinematics and kinetics of galloping in the cheetah and greyhound to investigate how the cheetah can attain such remarkable maximum speeds. This also presented an opportunity to investigate some of the potential limits to maximum running speed in quadrupeds, which remain poorly understood. By combining force plate and high speed video data of galloping cheetahs and greyhounds, we show how the cheetah uses a lower stride frequency/longer stride length than the greyhound at any given speed. In some trials, the cheetahs used swing times as low as those of the greyhounds (0.2 s) so the cheetah has scope to use higher stride frequencies (up to 4.0 Hz), which may contribute to it having a higher top speed that the greyhound. Weight distribution between the animal's limbs varied with increasing speed. At high speed, the hindlimbs support the majority of the animal's body weight, with the cheetah supporting 70% of its body weight on its hindlimbs at 18 m s(-1); however, the greyhound hindlimbs support just 62% of its body weight. Supporting a greater proportion of body weight on a particular limb is likely to reduce the risk of slipping during propulsive efforts. Our results demonstrate several features of galloping and highlight differences between the cheetah and greyhound that may account for the cheetah's faster maximum speeds.

Physiological and biomechanical responses while running with and without a stroller.

PubMed

Smith, J D; Smith, J D; Kinser, K B; Dugan, E; Reed, M

2005-09-01

This study examined the effects of pushing a jogging stroller on biomechanical and physiological variables. The hypothesis was that running with a stroller for 30 minutes would shorten stride length and increase physiological indices of exercise. this was a repeated measures design. participants were recruited from road races in the Dallas/Fort Worth, TX area. Graded exercise tests were performed in a laboratory setting, field tests were performed on a 400 m all-weather outdoor track. 5 males and 5 females were assessed. participants performed a graded exercise test and 2 field tests. The 1st field test involved running at 75% VO2max for 30 minutes without a stroller and the 2nd involved running at the same speed with the stroller. VO2, stride length, heart rate, lactate, ventilation, and RPE were evaluated. No differences for VO2 or stride length were evident. Heart rate (p=0.0001), lactate concentration (p=0.025), ventilation (p=0.009), and RPE (p=0.002) increased from 10 to 30 minutes while running with the stroller. Heart rate (p=0.002), lactate concentration (p=0.0001), ventilation (p=0.006), and RPE (p=0.001) were significantly higher while running with the stroller after 30 minutes compared to running without it. These results indicate that pushing a stroller affects some indices of exercise intensity while running. Gait does not change. These data do not support an association between stroller use during running and an increase risk of orthopedic injury. Further studies should examine these variables at lower intensities that are run by most recreational joggers.

Biomechanical and physiological comparison of barefoot and two shod conditions in experienced barefoot runners.

PubMed

Squadrone, R; Gallozzi, C

2009-03-01

The first aim of this study was to assess how changes in the mechanical characteristics of the foot/shoe-ground interface affect spatio-temporal variables, ground pressure distribution, sagittal plane kinematics, and running economy in 8 experienced barefoot runners. The second aim was to assess if a special lightweight shoe (Vibram Fivefingers) was effective in mimic the experience of barefoot running. By using an instrumented treadmill, barefoot running, running with the Fivefingers, and running with standard running shoe were compared, analyzing a large numbers of consecutive steps. Foot/shoe-ground interface pressure distribution, lower limb kinematics, V.O(2) and heart rate data were simultaneously collected. Compared to the standard shod condition when running barefoot the athletes landed in more plantarflexion at the ankle. This caused reduced impact forces and changes in stride kinematics. In particular, significantly shorter stride length and contact times and higher stride frequency were observed (P<0.05). Compared to standard shod condition, V.O(2) and peak impact forces were significantly lower with Fivefingers (P<0.05) and much closer to barefoot running. Lower limb kinematics with Fivefingers was similar to barefoot running with a foot position which was significantly more plantarflexed than in control shoe (P<0.05). The data of this study support the assumption that changes in the foot-ground interface led to changes in running pattern in a group of experienced barefoot runners. The Fivefingers model seems to be effective in imitating the barefoot conditions while providing a small amount of protection.

Ground reaction forces, kinematics, and muscle activations during the windmill softball pitch.

PubMed

Oliver, Gretchen D; Plummer, Hillary

2011-07-01

The aims of the present study were to examine quantitatively ground reaction forces, kinematics, and muscle activations during the windmill softball pitch, and to determine relationships between knee valgus and muscle activations, ball velocity and muscle activation as well as ball velocity and ground reaction forces. It was hypothesized that there would be an inverse relationship between degree of knee valgus and muscle activation, a direct relationship between ground reaction forces and ball velocity, and non-stride leg muscle activations and ball velocity. Ten female windmill softball pitchers (age 17.6 ± 3.47 years, stature 1.67 ± 0.07 m, weight 67.4 ± 12.2 kg) participated. Dependent variables were ball velocity, surface electromyographic (sEMG), kinematic, and kinetic data while the participant was the independent variable. Stride foot contact reported peak vertical forces of 179% body weight. There were positive relationships between ball velocity and ground reaction force (r = 0.758, n = 10, P = 0.029) as well as ball velocity and non-stride leg gluteus maximus (r = 0.851, n = 10, P = 0.007) and medius (r = 0.760, n = 10, P = 0.029) muscle activity, while there was no notable relationship between knee valgus and muscle activation. As the windmill softball pitcher increased ball velocity, her vertical ground reaction forces also increased. Proper conditioning of the lumbopelvic-hip complex, including the gluteals, is essential for injury prevention. From the data presented, it is evident that bilateral strength and conditioning of the gluteal muscle group is salient in the windmill softball pitch as an attempt to decrease incidence of injury.

Effect of trotting speed on kinematic variables measured by use of extremity-mounted inertial measurement units in nonlame horses performing controlled treadmill exercise.

PubMed

Cruz, Antonio M; Vidondo, Beatriz; Ramseyer, Alessandra A; Maninchedda, Ugo E

2018-02-01

OBJECTIVE To assess effects of speed on kinematic variables measured by use of extremity-mounted inertial measurement units (IMUs) in nonlame horses performing controlled exercise on a treadmill. ANIMALS 10 nonlame horses. PROCEDURES 6 IMUs were attached at predetermined locations on 10 nonlame Franches Montagnes horses. Data were collected in triplicate during trotting at 3.33 and 3.88 m/s on a high-speed treadmill. Thirty-three selected kinematic variables were analyzed. Repeated-measures ANOVA was used to assess the effect of speed. RESULTS Significant differences between the 2 speeds were detected for most temporal (11/14) and spatial (12/19) variables. The observed spatial and temporal changes would translate into a gait for the higher speed characterized by increased stride length, protraction and retraction, flexion and extension, mediolateral movement of the tibia, and symmetry, but with similar temporal variables and a reduction in stride duration. However, even though the tibia coronal range of motion was significantly different between speeds, the high degree of variability raised concerns about whether these changes were clinically relevant. For some variables, the lower trotting speed apparently was associated with more variability than was the higher trotting speed. CONCLUSIONS AND CLINICAL RELEVANCE At a higher trotting speed, horses moved in the same manner (eg, the temporal events investigated occurred at the same relative time within the stride). However, from a spatial perspective, horses moved with greater action of the segments evaluated. The detected changes in kinematic variables indicated that trotting speed should be controlled or kept constant during gait evaluation.

Research staff training in a multisite randomized clinical trial: Methods and recommendations from the Stimulant Reduction Intervention using Dosed Exercise (STRIDE) trial.

PubMed

Walker, Robrina; Morris, David W; Greer, Tracy L; Trivedi, Madhukar H

2014-01-01

Descriptions of and recommendations for meeting the challenges of training research staff for multisite studies are limited despite the recognized importance of training on trial outcomes. The STRIDE (STimulant Reduction Intervention using Dosed Exercise) study is a multisite randomized clinical trial that was conducted at nine addiction treatment programs across the United States within the National Drug Abuse Treatment Clinical Trials Network (CTN) and evaluated the addition of exercise to addiction treatment as usual (TAU), compared to health education added to TAU, for individuals with stimulant abuse or dependence. Research staff administered a variety of measures that required a range of interviewing, technical, and clinical skills. In order to address the absence of information on how research staff are trained for multisite clinical studies, the current manuscript describes the conceptual process of training and certifying research assistants for STRIDE. Training was conducted using a three-stage process to allow staff sufficient time for distributive learning, practice, and calibration leading up to implementation of this complex study. Training was successfully implemented with staff across nine sites. Staff demonstrated evidence of study and procedural knowledge via quizzes and skill demonstration on six measures requiring certification. Overall, while the majority of staff had little to no experience in the six measures, all research assistants demonstrated ability to correctly and reliably administer the measures throughout the study. Practical recommendations are provided for training research staff and are particularly applicable to the challenges encountered with large, multisite trials.

Comparison of transtibial amputee and non-amputee biomechanics during a common turning task.

PubMed

Segal, Ava D; Orendurff, Michael S; Czerniecki, Joseph M; Schoen, Jason; Klute, Glenn K

2011-01-01

The biomechanics of amputee turning gait has been minimally studied, in spite of its integral relationship with the more complex gait required for household or community ambulation. This study compares the biomechanics of unilateral transtibial amputees and non-amputees completing a common turning task. Full body gait analysis was completed for subjects walking at comparable self-selected speeds around a 1m radius circular path. Peak internal and external rotation moments of the hip, knee and ankle, mediolateral ground reaction impulse (ML GRI), peak effective limb length, and stride length were compared across conditions (non-amputee, amputee prosthetic limb, amputee sound limb). Amputees showed decreased internal rotation moments at the prosthetic limb hip and knee compared to non-amputees, perhaps as a protective mechanism to minimize stress on the residual limb. There was also an increase in amputee sound limb hip external rotation moment in early stance compared to non-amputees, which may be a compensation for the decrease in prosthetic limb internal rotation moment during late stance of the prior step. ML GRI was decreased for the amputee inside limb compared to non-amputee, possibly to minimize the body's acceleration in the direction of the turn. Amputees also exhibited a shorter inside limb stride length compared to non-amputees. Both decreased ML GRI and stride length indicate a COM that is more centered over the base of support, which may minimize the risk of falling. Finally, a longer effective limb length was found for the amputee inside limb turning, possibly due to excessive trunk shift. Published by Elsevier B.V.

Dribbling determinants in sub-elite youth soccer players.

PubMed

Zago, Matteo; Piovan, Andrea Gianluca; Annoni, Isabella; Ciprandi, Daniela; Iaia, F Marcello; Sforza, Chiarella

2016-01-01

Dribbling speed in soccer is considered critical to the outcome of the game and can assist in the talent identification process. However, little is known about the biomechanics of this skill. By means of a motion capture system, we aimed to quantitatively investigate the determinants of effective dribbling skill in a group of 10 Under-13 sub-elite players, divided by the median-split technique according to their dribbling test time (faster and slower groups). Foot-ball contacts cadence, centre of mass (CoM), ranges of motion (RoM), velocity and acceleration, as well as stride length, cadence and variability were computed. Hip and knee joint RoMs were also considered. Faster players, as compared to slower players, showed a 30% higher foot-ball cadence (3.0 ± 0.1 vs. 2.3 ± 0.2 contacts · s(-1), P < 0.01); reduced CoM mediolateral (0.91 ± 0.05 vs. 1.14 ± 0.16 m, P < 0.05) and vertical (0.19 ± 0.01 vs. 0.25 ± 0.03 m, P < 0.05) RoMs; higher right stride cadence (+20%, P < 0.05) with lower variability (P < 0.05); reduced hip and knee flexion RoMs (P < 0.05). In conclusion, faster players are able to run with the ball through a shorter path in a more economical way. To effectively develop dribbling skill, coaches are encouraged to design specific practices where high stride frequency and narrow run trajectories are required.

Identification of subgroups among fibromyalgia patients.

PubMed

Auvinet, B; Chaleil, D

2012-09-28

This paper presents some hypotheses concerning the identification of homogeneous subgroups among fibromyalgia (FM) patients in order to improve the management of the disease. It also reviews the available literature about this subject. Three methods for subgrouping are discussed according to clinical features, biomarkers, and gait analysis. Clinical subgrouping based on cluster analysis has been used for the identification of homogeneous subgroups of patients and, more recently, homogeneous clinical features. So far, longitudinal studies using clinical subgroups to direct treatment and predict outcome are still required. Biomarkers in FM, which is a neurobiological disease, are of promising interest, nevertheless currently, none of them can be used to subgroup FM patients. Due to the fact that cortical and subcortical mechanisms of gait control share some cognitive functions which are involved in FM, gait markers have been proposed to evaluate and to subgroup FM patients, in clinical settings. Three out of 4 core FM symptoms are linked to gait markers. Kinesia measured by means of cranio-caudal power is correlated to pain, and could be proposed to assess pain behavior (kinesiophobia). Stride frequency, which is linked to physical component, allows the identification of a hyperkinetic subgroup. Moreover, SF has been correlated to fatigue during the 6 minute walking test. Stride regularity, which expresses the unsteadiness of gait, is correlated to cognitive dysfunction in FM. Decreased stride regularity allows the recognition of a homogeneous subgroup characterized by an increased anxiety and depression, and decreased cognitive functions. These results need further studies to be validated and so used in the daily clinical practice.

Validity and sensitivity of the longitudinal asymmetry index to detect gait asymmetry using Microsoft Kinect data.

PubMed

Auvinet, E; Multon, F; Manning, V; Meunier, J; Cobb, J P

2017-01-01

Gait asymmetry information is a key point in disease screening and follow-up. Constant Relative Phase (CRP) has been used to quantify within-stride asymmetry index, which requires noise-free and accurate motion capture, which is difficult to obtain in clinical settings. This study explores a new index, the Longitudinal Asymmetry Index (ILong) which is derived using data from a low-cost depth camera (Kinect). ILong is based on depth images averaged over several gait cycles, rather than derived joint positions or angles. This study aims to evaluate (1) the validity of CRP computed with Kinect, (2) the validity and sensitivity of ILong for measuring gait asymmetry based solely on data provided by a depth camera, (3) the clinical applicability of a posteriorly mounted camera system to avoid occlusion caused by the standard front-fitted treadmill consoles and (4) the number of strides needed to reliably calculate ILong. The gait of 15 subjects was recorded concurrently with a marker-based system (MBS) and Kinect, and asymmetry was artificially reproduced by introducing a 5cm sole attached to one foot. CRP computed with Kinect was not reliable. ILong detected this disturbed gait reliably and could be computed from a posteriorly placed Kinect without loss of validity. A minimum of five strides was needed to achieve a correlation coefficient of 0.9 between standard MBS and low-cost depth camera based ILong. ILong provides a clinically pragmatic method for measuring gait asymmetry, with application for improved patient care through enhanced disease, screening, diagnosis and monitoring. Copyright © 2016. Published by Elsevier B.V.

Reducing the metabolic cost of walking with an ankle exoskeleton: interaction between actuation timing and power.

PubMed

Galle, Samuel; Malcolm, Philippe; Collins, Steven Hartley; De Clercq, Dirk

2017-04-27

Powered ankle-foot exoskeletons can reduce the metabolic cost of human walking to below normal levels, but optimal assistance properties remain unclear. The purpose of this study was to test the effects of different assistance timing and power characteristics in an experiment with a tethered ankle-foot exoskeleton. Ten healthy female subjects walked on a treadmill with bilateral ankle-foot exoskeletons in 10 different assistance conditions. Artificial pneumatic muscles assisted plantarflexion during ankle push-off using one of four actuation onset timings (36, 42, 48 and 54% of the stride) and three power levels (average positive exoskeleton power over a stride, summed for both legs, of 0.2, 0.4 and 0.5 W∙kg -1 ). We compared metabolic rate, kinematics and electromyography (EMG) between conditions. Optimal assistance was achieved with an onset of 42% stride and average power of 0.4 W∙kg -1 , leading to 21% reduction in metabolic cost compared to walking with the exoskeleton deactivated and 12% reduction compared to normal walking without the exoskeleton. With suboptimal timing or power, the exoskeleton still reduced metabolic cost, but substantially less so. The relationship between timing, power and metabolic rate was well-characterized by a two-dimensional quadratic function. The assistive mechanisms leading to these improvements included reducing muscular activity in the ankle plantarflexors and assisting leg swing initiation. These results emphasize the importance of optimizing exoskeleton actuation properties when assisting or augmenting human locomotion. Our optimal assistance onset timing and average power levels could be used for other exoskeletons to improve assistance and resulting benefits.

Body stability and muscle and motor cortex activity during walking with wide stance

PubMed Central

Farrell, Brad J.; Bulgakova, Margarita A.; Beloozerova, Irina N.; Sirota, Mikhail G.

2014-01-01

Biomechanical and neural mechanisms of balance control during walking are still poorly understood. In this study, we examined the body dynamic stability, activity of limb muscles, and activity of motor cortex neurons [primarily pyramidal tract neurons (PTNs)] in the cat during unconstrained walking and walking with a wide base of support (wide-stance walking). By recording three-dimensional full-body kinematics we found for the first time that during unconstrained walking the cat is dynamically unstable in the forward direction during stride phases when only two diagonal limbs support the body. In contrast to standing, an increased lateral between-paw distance during walking dramatically decreased the cat's body dynamic stability in double-support phases and prompted the cat to spend more time in three-legged support phases. Muscles contributing to abduction-adduction actions had higher activity during stance, while flexor muscles had higher activity during swing of wide-stance walking. The overwhelming majority of neurons in layer V of the motor cortex, 82% and 83% in the forelimb and hindlimb representation areas, respectively, were active differently during wide-stance walking compared with unconstrained condition, most often by having a different depth of stride-related frequency modulation along with a different mean discharge rate and/or preferred activity phase. Upon transition from unconstrained to wide-stance walking, proximal limb-related neuronal groups subtly but statistically significantly shifted their activity toward the swing phase, the stride phase where most of body instability occurs during this task. The data suggest that the motor cortex participates in maintenance of body dynamic stability during locomotion. PMID:24790167

The Strategies to Reduce Injuries and Develop Confidence in Elders Intervention: Falls Risk Factor Assessment and Management, Patient Engagement, and Nurse Co-management.

PubMed

Reuben, David B; Gazarian, Priscilla; Alexander, Neil; Araujo, Katy; Baker, Dorothy; Bean, Jonathan F; Boult, Chad; Charpentier, Peter; Duncan, Pamela; Latham, Nancy; Leipzig, Rosanne M; Quintiliani, Lisa M; Storer, Thomas; McMahon, Siobhan

2017-12-01

In response to the epidemic of falls and serious falls-related injuries in older persons, in 2014, the Patient Centered Outcomes Research Institute (PCORI) and the National Institute on Aging funded a pragmatic trial, Strategies to Reduce Injuries and Develop confidence in Elders (STRIDE) to compare the effects of a multifactorial intervention with those of an enhanced usual care intervention. The STRIDE multifactorial intervention consists of five major components that registered nurses deliver in the role of falls care managers, co-managing fall risk in partnership with patients and their primary care providers (PCPs). The components include a standardized assessment of eight modifiable risk factors (medications; postural hypotension; feet and footwear; vision; vitamin D; osteoporosis; home safety; strength, gait, and balance impairment) and the use of protocols and algorithms to generate recommended management of risk factors; explanation of assessment results to the patient (and caregiver when appropriate) using basic motivational interviewing techniques to elicit patient priorities, preferences, and readiness to participate in treatments; co-creation of individualized falls care plans that patients' PCPs review, modify, and approve; implementation of the falls care plan; and ongoing monitoring of response, regularly scheduled re-assessments of fall risk, and revisions of the falls care plan. Custom-designed falls care management software facilitates risk factor assessment, the identification of recommended interventions, clinic note generation, and longitudinal care management. The trial testing the effectiveness of the STRIDE intervention is in progress, with results expected in late 2019. © 2017, Copyright the Authors Journal compilation © 2017, The American Geriatrics Society.

Gait assessment in mild cognitive impairment and Alzheimer's disease: the effect of dual-task challenges across the cognitive spectrum.

PubMed

Muir, Susan W; Speechley, Mark; Wells, Jennie; Borrie, Michael; Gopaul, Karen; Montero-Odasso, Manuel

2012-01-01

Gait impairment is a prominent falls risk factor and a prevalent feature among older adults with cognitive impairment. However, there is a lack of comparative studies on gait performance and fall risk covering the continuum from normal cognition through mild cognitive impairment (MCI) to Alzheimer's disease (AD). We evaluated gait performance and the response to dual-task challenges in older adults with AD, MCI and normal cognition without a history of falls. We hypothesized that, in older people without history of falls, gait performance will deteriorate across the cognitive spectrum with changes being more evident under dual-tasking. Gait was assessed using an electronic walkway under single and three dual-tasks conditions. Gait velocity and stride time variability were not significantly different between the three groups under the single-task condition. By contrast, significant differences of decreasing velocity (p<0.0001), increasing stride time (p=0.0057) and increasing stride time variability (p=0.0037) were found under dual-task testing for people with MCI and AD. Less automatic and more complex dual-task tests, such as naming animals and serial subtraction by sevens from 100, created the greatest deterioration of gait performance. Gait changes under dual-tasking for the MCI and AD groups were statistically different from the cognitively normal controls. Dual-task assessment exposed gait impairments not obvious under a single-task test condition and may facilitate falls risk identification in cognitively impaired persons without a history of falls. Copyright © 2011 Elsevier B.V. All rights reserved.

The private life of echidnas: using accelerometry and GPS to examine field biomechanics and assess the ecological impact of a widespread, semi-fossorial monotreme.

PubMed

Clemente, Christofer J; Cooper, Christine E; Withers, Philip C; Freakley, Craig; Singh, Surya; Terrill, Philip

2016-10-15

The short-beaked echidna (Tachyglossus aculeatus) is a monotreme and therefore provides a unique combination of phylogenetic history, morphological differentiation and ecological specialisation for a mammal. The echidna has a unique appendicular skeleton, a highly specialised myrmecophagous lifestyle and a mode of locomotion that is neither typically mammalian nor reptilian, but has aspects of both lineages. We therefore were interested in the interactions of locomotor biomechanics, ecology and movements for wild, free-living short-beaked echidnas. To assess locomotion in its complex natural environment, we attached both GPS and accelerometer loggers to the back of echidnas in both spring and summer. We found that the locomotor biomechanics of echidnas is unique, with lower stride length and stride frequency than reported for similar-sized mammals. Speed modulation is primarily accomplished through changes in stride frequency, with a mean of 1.39 Hz and a maximum of 2.31 Hz. Daily activity period was linked to ambient air temperature, which restricted daytime activity during the hotter summer months. Echidnas had longer activity periods and longer digging bouts in spring compared with summer. In summer, echidnas had higher walking speeds than in spring, perhaps because of the shorter time suitable for activity. Echidnas spent, on average, 12% of their time digging, which indicates their potential to excavate up to 204 m 3 of soil a year. This information highlights the important contribution towards ecosystem health, via bioturbation, of this widespread Australian monotreme. © 2016. Published by The Company of Biologists Ltd.

A comparative analysis of spectral exponent estimation techniques for 1/f(β) processes with applications to the analysis of stride interval time series.

PubMed

Schaefer, Alexander; Brach, Jennifer S; Perera, Subashan; Sejdić, Ervin

2014-01-30

The time evolution and complex interactions of many nonlinear systems, such as in the human body, result in fractal types of parameter outcomes that exhibit self similarity over long time scales by a power law in the frequency spectrum S(f)=1/f(β). The scaling exponent β is thus often interpreted as a "biomarker" of relative health and decline. This paper presents a thorough comparative numerical analysis of fractal characterization techniques with specific consideration given to experimentally measured gait stride interval time series. The ideal fractal signals generated in the numerical analysis are constrained under varying lengths and biases indicative of a range of physiologically conceivable fractal signals. This analysis is to complement previous investigations of fractal characteristics in healthy and pathological gait stride interval time series, with which this study is compared. The results of our analysis showed that the averaged wavelet coefficient method consistently yielded the most accurate results. Class dependent methods proved to be unsuitable for physiological time series. Detrended fluctuation analysis as most prevailing method in the literature exhibited large estimation variances. The comparative numerical analysis and experimental applications provide a thorough basis for determining an appropriate and robust method for measuring and comparing a physiologically meaningful biomarker, the spectral index β. In consideration of the constraints of application, we note the significant drawbacks of detrended fluctuation analysis and conclude that the averaged wavelet coefficient method can provide reasonable consistency and accuracy for characterizing these fractal time series. Copyright © 2013 Elsevier B.V. All rights reserved.

A Mindful Approach to Diabetes Self-Management Education and Support for Veterans.

PubMed

DiNardo, Monica; Saba, Shaddy; Greco, Carol M; Broyles, Lauren; Terhorst, Lauren; Chasens, Eileen R; Bair, Brandi; Charron-Prochownik, Denise; Cohen, Susan

2017-12-01

Purpose The purpose of this study is to determine feasibility, satisfaction, and preliminary effects of Mindful Stress Reduction in Diabetes Education (Mind-STRIDE), a mindfulness-based intervention for veterans. Methods The study used a single-group pretest-posttest repeated-measures design. The 90-minute Mind-STRIDE training, adapted from Mindfulness Based Stress Reduction (MBSR), was provided as the final component of a half-day diabetes self-management education class at a Veterans Affairs (VA) outpatient diabetes clinic. Following initial training, participants were asked to practice mindfulness at home for 10 minutes each day during the 3-month study. Study recruitment and retention were calculated as rates. Veteran and diabetes educator satisfaction were assessed by rating scales and open-ended comments. Psychosocial-behavioral and metabolic outcomes were assessed at baseline and 3 months after initial training. Bivariate correlations were performed to describe relationships between mindfulness and other outcome variables. Gain scores and Wilcoxon matched-pair signed rank tests were used to assess pre to post changes; Cohen's d was applied to estimate the magnitude of effects. Results Twenty-eight of 49 eligible veterans (57%) enrolled in the study. Of those, 11 veterans (39%) demonstrated participation in home practice, and 20 veterans (71%) completed the study. Overall, participants and diabetes educators were highly satisfied with the Mind-STRIDE intervention. Significant improvements were found in diabetes distress, diabetes self-efficacy, diabetes self-management behaviors, mindful-describing, and A1C. Conclusion Results suggest feasibility, satisfaction, and positive preliminary effects. Efficacy testing by randomized controlled trial with analysis of covariance structures is warranted.

THE EMERGENCE OF ECOLOGICAL ENGINEERING AS A DISCIPLINE

EPA Science Inventory

Pioneering efforts in the field of ecological engineering research and practice have proven to be tremendous strides toward establishing a new engineering discipline with a science base in ecology. Case studies, demonstrations and applications pertaining to restoration, rehabili...

Sidewalk Survey Implementation for the Southeast Region

DOT National Transportation Integrated Search

2017-06-01

With funding from GDOT and STRIDE, the team deployed the Online Sidewalk Assessment Survey to gather input on local sidewalk repair and maintenance preferences across a variety of community types in the southeast. The team targeted four major cities ...

CANCER RISK ASSESSMENT FOR 1,3 BUTADIENE: DATA INTEGRATION OPPORTUNITIES

EPA Science Inventory

The U.S. Environmental Protection Agency recently released its new Guidelines for Carcinogen Risk Assessment together with Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens. These new cancer guidelines benefit from the significant strides ...

AASHTO research : making strides for highway safety.

DOT National Transportation Integrated Search

2014-01-01

State DOTs are committed to using research and innovation to deliver more efficient and safer transportation systems. The projects on these pages are a few among many that exemplify the high return on transportation research investments. The State Pl...

A quantitative analysis of gait patterns in vestibular neuritis patients using gyroscope sensor and a continuous walking protocol

PubMed Central

2014-01-01

Background Locomotion involves an integration of vision, proprioception, and vestibular information. The parieto-insular vestibular cortex is known to affect the supra-spinal rhythm generators, and the vestibular system regulates anti-gravity muscle tone of the lower leg in the same side to maintain an upright posture through the extra-pyramidal track. To demonstrate the relationship between locomotion and vestibular function, we evaluated the differences in gait patterns between vestibular neuritis (VN) patients and normal subjects using a gyroscope sensor and long-way walking protocol. Methods Gyroscope sensors were attached to both shanks of healthy controls (n=10) and age-matched VN patients (n = 10). We then asked the participants to walk 88.8 m along a corridor. Through the summation of gait cycle data, we measured gait frequency (Hz), normalized angular velocity (NAV) of each axis for legs, maximum and minimum NAV, up-slope and down-slope of NAV in swing phase, stride-swing-stance time (s), and stance to stride ratio (%). Results The most dominant walking frequency in the VN group was not different compared to normal control. The NAVs of z-axis (pitch motion) were significantly larger than the others (x-, y-axis) and the values in VN patients tended to decrease in both legs and the difference of NAV between both group was significant in the ipsi-lesion side in the VN group only (p=0.03). Additionally, the gait velocity of these individuals was decreased relatively to controls (1.11 ± 0.120 and 0.84 ± 0.061 m/s in control and VN group respectively, p<0.01), which seems to be related to the significantly increased stance and stride time of the ipsi-lesion side. Moreover, in the VN group, the maximum NAV of the lesion side was less, and the minimum one was higher than control group. Furthermore, the down-slope and up-slope of NAV decreased on the impaired side. Conclusion The walking pattern of VN patients was highly phase-dependent, and NAV of pitch motion was significantly decreased in the ipsi-lesion side. The change of gait rhythm, stance and stride time, and maximum/minimum NAV of the ipsi-lesion side were characteristics of individuals with VN. PMID:24725764

A quantitative analysis of gait patterns in vestibular neuritis patients using gyroscope sensor and a continuous walking protocol.

PubMed

Kim, Soo Chan; Kim, Joo Yeon; Lee, Hwan Nyeong; Lee, Hwan Ho; Kwon, Jae Hwan; Kim, Nam Beom; Kim, Mi Joo; Hwang, Jong Hyun; Han, Gyu Cheol

2014-04-11

Locomotion involves an integration of vision, proprioception, and vestibular information. The parieto-insular vestibular cortex is known to affect the supra-spinal rhythm generators, and the vestibular system regulates anti-gravity muscle tone of the lower leg in the same side to maintain an upright posture through the extra-pyramidal track. To demonstrate the relationship between locomotion and vestibular function, we evaluated the differences in gait patterns between vestibular neuritis (VN) patients and normal subjects using a gyroscope sensor and long-way walking protocol. Gyroscope sensors were attached to both shanks of healthy controls (n=10) and age-matched VN patients (n = 10). We then asked the participants to walk 88.8 m along a corridor. Through the summation of gait cycle data, we measured gait frequency (Hz), normalized angular velocity (NAV) of each axis for legs, maximum and minimum NAV, up-slope and down-slope of NAV in swing phase, stride-swing-stance time (s), and stance to stride ratio (%). The most dominant walking frequency in the VN group was not different compared to normal control. The NAVs of z-axis (pitch motion) were significantly larger than the others (x-, y-axis) and the values in VN patients tended to decrease in both legs and the difference of NAV between both group was significant in the ipsi-lesion side in the VN group only (p=0.03). Additionally, the gait velocity of these individuals was decreased relatively to controls (1.11 ± 0.120 and 0.84 ± 0.061 m/s in control and VN group respectively, p<0.01), which seems to be related to the significantly increased stance and stride time of the ipsi-lesion side. Moreover, in the VN group, the maximum NAV of the lesion side was less, and the minimum one was higher than control group. Furthermore, the down-slope and up-slope of NAV decreased on the impaired side. The walking pattern of VN patients was highly phase-dependent, and NAV of pitch motion was significantly decreased in the ipsi-lesion side. The change of gait rhythm, stance and stride time, and maximum/minimum NAV of the ipsi-lesion side were characteristics of individuals with VN.

Single- and Dual-Task Balance Training Are Equally Effective in Youth

PubMed Central

Lüder, Benjamin; Kiss, Rainer; Granacher, Urs

2018-01-01

Due to maturation of the postural control system and secular declines in motor performance, adolescents experience deficits in postural control during standing and walking while concurrently performing cognitive interference tasks. Thus, adequately designed balance training programs may help to counteract these deficits. While the general effectiveness of youth balance training is well-documented, there is hardly any information available on the specific effects of single-task (ST) versus dual-task (DT) balance training. Therefore, the objectives of this study were (i) to examine static/dynamic balance performance under ST and DT conditions in adolescents and (ii) to study the effects of ST versus DT balance training on static/dynamic balance under ST and DT conditions in adolescents. Twenty-eight healthy girls and boys aged 12–13 years were randomly assigned to either 8 weeks of ST or DT balance training. Before and after training, postural sway and spatio-temporal gait parameters were registered under ST (standing/walking only) and DT conditions (standing/walking while concurrently performing an arithmetic task). At baseline, significantly slower gait speed (p < 0.001, d = 5.1), shorter stride length (p < 0.001, d = 4.8), and longer stride time (p < 0.001, d = 3.8) were found for DT compared to ST walking but not standing. Training resulted in significant pre–post decreases in DT costs for gait velocity (p < 0.001, d = 3.1), stride length (-45%, p < 0.001, d = 2.4), and stride time (-44%, p < 0.01, d = 1.9). Training did not induce any significant changes (p > 0.05, d = 0–0.1) in DT costs for all parameters of secondary task performance during standing and walking. Training produced significant pre–post increases (p = 0.001; d = 1.47) in secondary task performance while sitting. The observed increase was significantly greater for the ST training group (p = 0.04; d = 0.81). For standing, no significant changes were found over time irrespective of the experimental group. We conclude that adolescents showed impaired DT compared to ST walking but not standing. ST and DT balance training resulted in significant and similar changes in DT costs during walking. Thus, there appears to be no preference for either ST or DT balance training in adolescents. PMID:29928248

Single- and Dual-Task Balance Training Are Equally Effective in Youth.

PubMed

Lüder, Benjamin; Kiss, Rainer; Granacher, Urs

2018-01-01

Due to maturation of the postural control system and secular declines in motor performance, adolescents experience deficits in postural control during standing and walking while concurrently performing cognitive interference tasks. Thus, adequately designed balance training programs may help to counteract these deficits. While the general effectiveness of youth balance training is well-documented, there is hardly any information available on the specific effects of single-task (ST) versus dual-task (DT) balance training. Therefore, the objectives of this study were (i) to examine static/dynamic balance performance under ST and DT conditions in adolescents and (ii) to study the effects of ST versus DT balance training on static/dynamic balance under ST and DT conditions in adolescents. Twenty-eight healthy girls and boys aged 12-13 years were randomly assigned to either 8 weeks of ST or DT balance training. Before and after training, postural sway and spatio-temporal gait parameters were registered under ST (standing/walking only) and DT conditions (standing/walking while concurrently performing an arithmetic task). At baseline, significantly slower gait speed ( p < 0.001, d = 5.1), shorter stride length ( p < 0.001, d = 4.8), and longer stride time ( p < 0.001, d = 3.8) were found for DT compared to ST walking but not standing. Training resulted in significant pre-post decreases in DT costs for gait velocity ( p < 0.001, d = 3.1), stride length (-45%, p < 0.001, d = 2.4), and stride time (-44%, p < 0.01, d = 1.9). Training did not induce any significant changes ( p > 0.05, d = 0-0.1) in DT costs for all parameters of secondary task performance during standing and walking. Training produced significant pre-post increases ( p = 0.001; d = 1.47) in secondary task performance while sitting. The observed increase was significantly greater for the ST training group ( p = 0.04; d = 0.81). For standing, no significant changes were found over time irrespective of the experimental group. We conclude that adolescents showed impaired DT compared to ST walking but not standing. ST and DT balance training resulted in significant and similar changes in DT costs during walking. Thus, there appears to be no preference for either ST or DT balance training in adolescents.

Kinematic and Kinetic Profiles of Trunk and Lower Limbs during Baseball Pitching in Collegiate Pitchers

PubMed Central

Kageyama, Masahiro; Sugiyama, Takashi; Takai, Yohei; Kanehisa, Hiroaki; Maeda, Akira

2014-01-01

The purpose of this study was to clarify differences in the kinematic and kinetic profiles of the trunk and lower extremities during baseball pitching in collegiate baseball pitchers, in relation to differences in the pitched ball velocity. The subjects were 30 collegiate baseball pitchers aged 18 to 22 yrs, who were assigned to high- (HG, 37.4 ± 0.8 m·s-1) and low-pitched-ball-velocity groups (LG, 33.3 ± 0.8 m·s-1). Three-dimensional motion analysis with a comprehensive lower-extremity model was used to evaluate kinematic and kinetic parameters during baseball pitching. The ground-reaction forces (GRF) of the pivot and stride legs during pitching were determined using two multicomponent force plates. The joint torques of hip, knee, and ankle were calculated using inverse-dynamics computation of a musculoskeletal human model. To eliminate any effect of variation in body size, kinetic and GRF data were normalized by dividing them by body mass. The maxima and minima of GRF (Fy, Fz, and resultant forces) on the pivot and stride leg were significantly greater in the HG than in the LG (p < 0.05). Furthermore, Fy, Fz, and resultant forces on the stride leg at maximum shoulder external rotation and ball release were significantly greater in the HG than in the LG (p < 0.05). The hip abduction, hip internal rotation and knee extension torques of the pivot leg and the hip adduction torque of the stride leg when it contacted the ground were significantly greater in the HG than in the LG (p < 0.05). These results indicate that, compared with low-ball-velocity pitchers, high-ball-velocity pitchers can generate greater momentum of the lower limbs during baseball pitching. Key points High-ball-velocity pitchers are characterized by greater momentum of the lower limbs during pitching motion. For high-pitched-ball velocity, stabilizing lower limbs during pitching plays an important role in order to increase the rotation and forward motion of the trunk. Computation of the lower-extremity kinetics and measurement of lower-extremity strength may help clarify the role of muscle strength in determining knee and hip function in baseball pitching. PMID:25435765

Static Frequency Converter System Installed and Tested

NASA Technical Reports Server (NTRS)

Brown, Donald P.; Sadhukhan, Debashis

2003-01-01

A new Static Frequency Converter (SFC) system has been installed and tested at the NASA Glenn Research Center s Central Air Equipment Building to provide consistent, reduced motor start times and improved reliability for the building s 14 large exhausters and compressors. The operational start times have been consistent around 2 min, 20 s per machine. This is at least a 3-min improvement (per machine) over the old variable-frequency motor generator sets. The SFC was designed and built by Asea Brown Boveri (ABB) and installed by Encompass Design Group (EDG) as part of a Construction of Facilities project managed by Glenn (Robert Scheidegger, project manager). The authors designed the Central Process Distributed Control Systems interface and control between the programmable logic controller, solid-state exciter, and switchgear, which was constructed by Gilcrest Electric.

Strength and Microstructure of Ceramics.

DTIC Science & Technology

1987-11-01

triangular slab. 12-mm edge length and 2-mm thickness. to produce crack 7 mm long. Starter notch length portantly. the strength plateau at small flaw sizes...however. a tapered the starter notch tip. "Pop-in" behavior of this kind is not uncom- geometry was used. width increasing in the direction of ultimate...mon in notched specimens, of course: in such cases the initial crack propagation. The main crack was started at a sawcut notch fracture response can be

Spectroscopic characteristics of carbon dots (C-dots) derived from carbon fibers and conversion to sulfur-bridged C-dots nanosheets.

PubMed

Vinci, John C; Ferrer, Ivonne M; Guterry, Nathan W; Colón, Verónica M; Destino, Joel F; Bright, Frank V; Colón, Luis A

2015-09-01

We synthesized sub-10 nm carbon nanoparticles (CNPs) consistent with photoluminescent carbon dots (C-dots) from carbon fiber starting material. The production of different C-dots fractions was monitored over seven days. During the course of the reaction, one fraction of C-dots species with relatively high photoluminescence was short-lived, emerging during the first hour of reaction but disappearing after one day of reaction. Isolation of this species during the first hour of the reaction was crucial to obtaining higher-luminescent C-dots species. When the reaction proceeded for one week, the appearance of larger nanostructures was observed over time, with lateral dimensions approaching 200 nm. The experimental evidence suggests that these larger species are formed from small C-dot nanoparticles bridged together by sulfur-based moieties between the C-dot edge groups, as if the C-dots polymerized by cross-linking the edge groups through sulfur bridges. Their size can be tailored by controlling the reaction time. Our results highlight the variety of CNP products, from sub-10 nm C-dots to ~200 nm sulfur-containing carbon nanostructures, that can be produced over time during the oxidation reaction of the graphenic starting material. Our work provides a clear understanding of when to stop the oxidation reaction during the top-down production of C-dots to obtain highly photoluminescent species or a target average particle size.

TH-A-BRF-04: Intra-Fraction Motion Characterization for Early Stage Rectal Cancer Using Cine-MRI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleijnen, J; Asselen, B; Burbach, M

2014-06-15

Purpose: To investigate the intra-fraction motion in patients with early stage rectal cancer using cine-MRI. Methods: Sixteen patient diagnosed with early stage rectal cancer underwent 1.5 T MR imaging prior to each treatment fraction of their short course radiotherapy (n=76). During each scan session, three 2D sagittal cine-MRIs were performed: at the beginning (Start), after 9:30 minutes (Mid), and after 18 minutes (End). Each cine-MRI has a duration of one minute at 2Hz temporal resolution, resulting in a total of 3:48 hours of cine-MRI. Additionally, standard T2-weighted (T2w) imaging was performed. Clinical target volume (CTV) an tumor (GTV) were delineatedmore » on the T2w scan and transferred to the first time-point of each cine-MRI scan. Within each cine-MRI, the first frame was registered to the remaining frames of the scan, using a non-rigid B-spline registration. To investigate potential drifts, a similar registration was performed between the first frame of the Start and End scans.To evaluate the motion, the distances by which the edge pixels of the delineations move in anterior-posterior (AP) and cranial-caudal (CC) direction, were determined using the deformation field of the registrations. The distance which incorporated 95% of these edge pixels (dist95%) was determined within each cine-MRI, and between Start- End scans, respectively. Results: Within a cine-MRI, we observed an average dist95% for the CTV of 1.3mm/1.5mm (SD=0.7mm/0.6mm) and for the GTV of 1.2mm/1.5mm (SD=0.8mm/0.9mm), in respectively AP/CC. For the CTV motion between the Start and End scan, an average dist95% of 5.5mm/5.3mm (SD=3.1mm/2.5mm) was found, in respectively AP/CC. For the GTV motion, an average dist95% of 3.6mm/3.9mm (SD=2.2mm/2.5mm) was found in AP/CC, respectively. Conclusion: Although intra-fraction motion within a one minute cine-MRI is limited, substantial intra-fraction motion was observed within the 18 minute time period between the Start and End cine-MRI.« less

P-Finder: Reconstruction of Signaling Networks from Protein-Protein Interactions and GO Annotations.

PubMed

Young-Rae Cho; Yanan Xin; Speegle, Greg

2015-01-01

Because most complex genetic diseases are caused by defects of cell signaling, illuminating a signaling cascade is essential for understanding their mechanisms. We present three novel computational algorithms to reconstruct signaling networks between a starting protein and an ending protein using genome-wide protein-protein interaction (PPI) networks and gene ontology (GO) annotation data. A signaling network is represented as a directed acyclic graph in a merged form of multiple linear pathways. An advanced semantic similarity metric is applied for weighting PPIs as the preprocessing of all three methods. The first algorithm repeatedly extends the list of nodes based on path frequency towards an ending protein. The second algorithm repeatedly appends edges based on the occurrence of network motifs which indicate the link patterns more frequently appearing in a PPI network than in a random graph. The last algorithm uses the information propagation technique which iteratively updates edge orientations based on the path strength and merges the selected directed edges. Our experimental results demonstrate that the proposed algorithms achieve higher accuracy than previous methods when they are tested on well-studied pathways of S. cerevisiae. Furthermore, we introduce an interactive web application tool, called P-Finder, to visualize reconstructed signaling networks.

Unlocking the Mystery of Columbia's Tragic Accident Through Materials Characterization

NASA Technical Reports Server (NTRS)

Shah, Sandeep; Jerman, Gregory; Coston, James

2003-01-01

The wing and underbelly reconstruction of Space Shuttle Columbia took place at the Shuttle Landing Facility Hangar after the accident which destroyed STS-107. Fragments were placed on a grid according to their original location on the orbiter. Some Reinforced Carbon-Carbon (RCC) panels of the left wing leading edge and other parts from both leading edges were recovered and incorporated into the reconstruction. The recovered parts were tracked on a database according to a number and also tracked on a map of the orbiter. This viewgraph presentation describes the process of failure analysis undertaken by the Materials and Processes (M&P) Problem Resolution Team. The team started with factual observations about the accident, and identified highest level questions for it to answer in order to understand where on the orbiter failure occured, what component(s) failed, and what was the sequence of events. The finding of Columbia's MADS/OEX data recorder shifted the focus of the team's analysis to the left wing leading edge damage. The team placed particular attention on slag deposits on some of the RCC panels. The presentation lists analysis techniques, and lower level questions for the team to answer.

Features of owl wings that promote silent flight

PubMed Central

Weger, Matthias; Klaas, Michael; Schröder, Wolfgang

2017-01-01

Owls are an order of birds of prey that are known for the development of a silent flight. We review here the morphological adaptations of owls leading to silent flight and discuss also aerodynamic properties of owl wings. We start with early observations (until 2005), and then turn to recent advances. The large wings of these birds, resulting in low wing loading and a low aspect ratio, contribute to noise reduction by allowing slow flight. The serrations on the leading edge of the wing and the velvet-like surface have an effect on noise reduction and also lead to an improvement of aerodynamic performance. The fringes at the inner feather vanes reduce noise by gliding into the grooves at the lower wing surface that are formed by barb shafts. The fringed trailing edge of the wing has been shown to reduce trailing edge noise. These adaptations to silent flight have been an inspiration for biologists and engineers for the development of devices with reduced noise production. Today several biomimetic applications such as a serrated pantograph or a fringed ventilator are available. Finally, we discuss unresolved questions and possible future directions. PMID:28163870

Early rehabilitation treatment combined with equinovarus foot deformity surgical correction in stroke patients: safety and changes in gait parameters.

PubMed

Giannotti, Erika; Merlo, Andrea; Zerbinati, Paolo; Longhi, Maria; Prati, Paolo; Masiero, Stefano; Mazzoli, Davide

2016-06-01

Equinovarus foot deformity (EVFD) compromises several prerequisites of walking and increases the risk of falling. Guidelines on rehabilitation following EVFD surgery are missing in current literature. The aim of this study was to analyze safety and adherence to an early rehabilitation treatment characterized by immediate weight bearing with an ankle-foot orthosis (AFO) in hemiplegic patients after EVFD surgery and to describe gait changes after EVFD surgical correction combined with early rehabilitation treatment. Retrospective observational cohort study. Inpatient rehabilitation clinic. Forty-seven adult patients with hemiplegia consequent to ischemic or haemorrhagic stroke (L/R 20/27, age 56±15 years, time from lesion 6±5 years). A specific rehabilitation protocol with a non-articulated AFO, used to allow for immediate gait training, started one day after EVFD surgery. Gait analysis (GA) data before and one month after surgery were analyzed. The presence of differences in GA space-time parameters, in ankle dorsiflexion (DF) values and peaks at initial contact (DF at IC), during stance (DF at St) and swing (DF at Sw) were assessed by the Wilcoxon Test while the presence of correlations between pre- and post-operative values by Spearman's correlation coefficient. All patients completed the rehabilitation protocol and no clinical complications occurred in the sample. Ankle DF increased one month after surgery at all investigated gait phases (Wilcoxon Test, P<0.0001), becoming neutral at IC. Significant (P<0.05) variations were found for stride length, stride width, anterior step length of the affected side and for the duration of the double support phase of the contralateral side. The postsurgery ankle DF at St was found to be correlated (R=0.81, P<0.0001) with its pre-surgery value, thus being predictable. Weaker significant correlations were found for DF at Sw and DF at IC, where contribution from the dorsiflexor muscles is required in addition to calf muscle passive lengthening. An orthosis-assisted immediate rehabilitation associated with surgical procedure is safe and may be suitable to correct EVFD by restoring both the neutral heel foot-ground contact and the ankle DF peaks during stance and swing at one month from surgery. The proposed protocol is a safe and potentially useful rehabilitative approach after EVFD surgical correction in stroke patients.

Dynamical generation of Floquet Majorana flat bands in s-wave superconductors

NASA Astrophysics Data System (ADS)

Poudel, A.; Ortiz, G.; Viola, L.

2015-04-01

We present quantum control techniques to engineer flat bands of symmetry-protected Majorana edge modes in s-wave superconductors. Specifically, we show how periodic control may be employed for designing time-independent effective Hamiltonians, which support Floquet Majorana flat bands, starting from equilibrium conditions that are either topologically trivial or only support a Majorana pair per edge. In the first approach, a suitable modulation of the chemical potential simultaneously induces Majorana flat bands and dynamically activates a pre-existing chiral symmetry which is responsible for their protection. In the second approach, the application of effective parity kicks dynamically generates a desired chiral symmetry by suppressing chirality-breaking terms in the static Hamiltonian. Our results demonstrate how the use of time-dependent control enlarges the range of possibilities for realizing gapless topological superconductivity, potentially enabling access to topological states of matter that have no known equilibrium counterpart.

Reverse engineering the ancient ceramic technology based on X-ray fluorescence spectromicroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sciau, Philippe; Leon, Yoanna; Goudeau, Philippe

2011-07-06

We present results of X-ray fluorescence (XRF) microprobe analyses of ancient ceramic cross-sections aiming at deciphering the different firing protocols used for their production. Micro-focused XRF elemental mapping, Fe chemical mapping and Fe K-edge X-ray absorption near edge structure spectroscopy were performed on pre-sigillata ceramics from southern Gaul, and terra Sigillata vessels from Italy and southern Gaul. Pieces from the different workshops and regions showed significant difference in the starting clay material, clay conditioning and kiln firing condition. By contrast, sherds from the same workshop exhibited more subtle differences and possible misfirings. Understanding the precise firing conditions and protocols wouldmore » allow recreation of kilns for various productions. Furthermore, evolution and modification of kiln design would shed some light on how ancient potters devised solutions to diverse technological problems they encountered.« less

Toward deep blue nano hope diamonds: heavily boron-doped diamond nanoparticles.

PubMed

Heyer, Steffen; Janssen, Wiebke; Turner, Stuart; Lu, Ying-Gang; Yeap, Weng Siang; Verbeeck, Jo; Haenen, Ken; Krueger, Anke

2014-06-24

The production of boron-doped diamond nanoparticles enables the application of this material for a broad range of fields, such as electrochemistry, thermal management, and fundamental superconductivity research. Here we present the production of highly boron-doped diamond nanoparticles using boron-doped CVD diamond films as a starting material. In a multistep milling process followed by purification and surface oxidation we obtained diamond nanoparticles of 10-60 nm with a boron content of approximately 2.3 × 10(21) cm(-3). Aberration-corrected HRTEM reveals the presence of defects within individual diamond grains, as well as a very thin nondiamond carbon layer at the particle surface. The boron K-edge electron energy-loss near-edge fine structure demonstrates that the B atoms are tetrahedrally embedded into the diamond lattice. The boron-doped diamond nanoparticles have been used to nucleate growth of a boron-doped diamond film by CVD that does not contain an insulating seeding layer.

[Medicine at the "edge of chaos". Life, entropy and complexity].

PubMed

De Vito, Eduardo L

2016-01-01

The aim of this paper is to help physicians and health professionals, who constantly seek to improve their knowledge for the benefit of the ill, to incorporate new conceptual and methodological tools to understand the complexity inherent to the field of medicine. This article contains notions that are unfamiliar to these professionals and are intended to foster reflection and learning. It poses the need to define life from a thermodynamic point of view, linking it closely to complex systems, nonlinear dynamics and chaotic behavior, as well as to redefine conventional physiological control mechanisms based on the concept of homeostasis, and to travel the path that starts with the search for extraterrestrial life up to exposing medicine "near the edge of chaos". Complexity transcends the biological aspects; it includes a subjective and symbolic/social dimension. Viewing disease as a heterogeneous and multi-causal phenomenon can give rise to new approaches for the sick.

Sun Grant Initiative : great strides toward a sustainable and more energy-independent future

DOT National Transportation Integrated Search

2014-09-01

The Sun Grant Initiative publication, developed by the U.S. Department of Transportation, offers a glimpse of how the Sun Grant Initiative Centers are advancing alternative fuels research. Transportation plays a significant role in biofuels research,...

Taking flight with sensing equipment will deliver benefits across MDOT : research spotlight.

DOT National Transportation Integrated Search

2015-04-01

Recent strides in technology have opened the doors for using unmanned : aerial vehicles (UAVs, sometimes called drones) throughout MDOT. An : extensive study on the viability of UAVs instrumented with remote : sensors demonstrated a wide range of cos...

A Method of Strengthening Composite/Metal Joints

NASA Technical Reports Server (NTRS)

Polis, Daniel L.

2011-01-01

The term tape setback method denotes a method of designing and fabricating bonded joints between (1) box beams or other structural members made of laminated composite (matrix/ fiber) materials and (2) metal end fittings used to fasten these structural members to other structural members. The basic idea of the tape setback method is to mask the bonded interface between the metallic end fitting and composite member such that the bond does not extend out to the free edges of the composite member. The purpose served by the tape setback method is to strengthen the joints by decoupling stress concentrations from edge defects, which can cause premature failures. A related prior method that serves a similar purpose, involving the use of tapered adherends at the joints, can be too difficult and costly to be acceptable in some applications. The tape setback method offers an easier, less costly alternative. The structural members to which the method was originally applied were box beams in the form of composite tubes having flat faces with rounded corners. The end fittings were plugs made of a low-thermal- expansion nickel/iron alloy (see figure). In computational-simulation studies of tensile and compressive loading of members without tape setback, stresses were found to be concentrated at the free end edges of the composite tubes, and inspection of members that had been subjected to real tension and compression tests showed that cracks started at the free end edges. As applied to these members, the tape setback method makes them less vulnerable to initiation of failure at edge defects produced during fabrication. In real tension tests of comparable members without and with tape setback, the average mean tensile strength of the members with tape setback was found to be 1.9 times that of the members without tape setback.

Outreach/education interface for Cryosphere models using the Virtual Ice Sheet Laboratory

NASA Astrophysics Data System (ADS)

Larour, E. Y.; Halkides, D. J.; Romero, V.; Cheng, D. L.; Perez, G.

2014-12-01

In the past decade, great strides have been made in the development of models capable of projecting the future evolution of glaciers and the polar ice sheets in a changing climate. These models are now capable of replicating some of the trends apparent in satellite observations. However, because this field is just now maturing, very few efforts have been dedicated to adapting these capabilities to education. Technologies that have been used in outreach efforts in Atmospheric and Oceanic sciences still have not been extended to Cryospheric Science. We present a cutting-edge, technologically driven virtual laboratory, geared towards outreach and k-12 education, dedicated to the polar ice sheets on Antarctica and Greenland, and their role as major contributors to sea level rise in coming decades. VISL (Virtual Ice Sheet Laboratory) relies on state-of-the art Web GL rendering of polar ice sheets, Android/iPhone and web portability using Javascript, as well as C++ simulations (back-end) based on the Ice Sheet System Model, the NASA model for simulating the evolution of polar ice sheets. Using VISL, educators and students can have an immersive experience into the world of polar ice sheets, while at the same exercising the capabilities of a state-of-the-art climate model, all of it embedded into an education experience that follows the new STEM standards for education.This work was performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryosphere Science Program.

CSI 3.0: a web server for identifying secondary and super-secondary structure in proteins using NMR chemical shifts

PubMed Central

Hafsa, Noor E.; Arndt, David; Wishart, David S.

2015-01-01

The Chemical Shift Index or CSI 3.0 (http://csi3.wishartlab.com) is a web server designed to accurately identify the location of secondary and super-secondary structures in protein chains using only nuclear magnetic resonance (NMR) backbone chemical shifts and their corresponding protein sequence data. Unlike earlier versions of CSI, which only identified three types of secondary structure (helix, β-strand and coil), CSI 3.0 now identifies total of 11 types of secondary and super-secondary structures, including helices, β-strands, coil regions, five common β-turns (type I, II, I′, II′ and VIII), β hairpins as well as interior and edge β-strands. CSI 3.0 accepts experimental NMR chemical shift data in multiple formats (NMR Star 2.1, NMR Star 3.1 and SHIFTY) and generates colorful CSI plots (bar graphs) and secondary/super-secondary structure assignments. The output can be readily used as constraints for structure determination and refinement or the images may be used for presentations and publications. CSI 3.0 uses a pipeline of several well-tested, previously published programs to identify the secondary and super-secondary structures in protein chains. Comparisons with secondary and super-secondary structure assignments made via standard coordinate analysis programs such as DSSP, STRIDE and VADAR on high-resolution protein structures solved by X-ray and NMR show >90% agreement between those made with CSI 3.0. PMID:25979265

Aerodynamics and vortical structures in hovering fruitflies

NASA Astrophysics Data System (ADS)

Meng, Xue Guang; Sun, Mao

2015-03-01

We measure the wing kinematics and morphological parameters of seven freely hovering fruitflies and numerically compute the flows of the flapping wings. The computed mean lift approximately equals to the measured weight and the mean horizontal force is approximately zero, validating the computational model. Because of the very small relative velocity of the wing, the mean lift coefficient required to support the weight is rather large, around 1.8, and the Reynolds number of the wing is low, around 100. How such a large lift is produced at such a low Reynolds number is explained by combining the wing motion data, the computed vortical structures, and the theory of vorticity dynamics. It has been shown that two unsteady mechanisms are responsible for the high lift. One is referred as to "fast pitching-up rotation": at the start of an up- or downstroke when the wing has very small speed, it fast pitches down to a small angle of attack, and then, when its speed is higher, it fast pitches up to the angle it normally uses. When the wing pitches up while moving forward, large vorticity is produced and sheds at the trailing edge, and vorticity of opposite sign is produced near the leading edge and on the upper surface, resulting in a large time rate of change of the first moment of vorticity (or fluid impulse), hence a large aerodynamic force. The other is the well known "delayed stall" mechanism: in the mid-portion of the up- or downstroke the wing moves at large angle of attack (about 45 deg) and the leading-edge-vortex (LEV) moves with the wing; thus, the vortex ring, formed by the LEV, the tip vortices, and the starting vortex, expands in size continuously, producing a large time rate of change of fluid impulse or a large aerodynamic force.

Effect of radius of gyration on a wing rotating at low Reynolds number: A computational study

NASA Astrophysics Data System (ADS)

Tudball Smith, Daniel; Rockwell, Donald; Sheridan, John; Thompson, Mark

2017-06-01

This computational study analyzes the effect of variation of the radius of gyration (rg), expressed as the Rossby number Ro=rg/C , with C the chord, on the aerodynamics of a rotating wing at a Reynolds number of 1400. The wing is represented as an aspect-ratio-unity rectangular flat plate aligned at 45 ∘ . This plate is accelerated near impulsively to a constant rotational velocity and the flow is allowed to develop. Flow structures are analyzed and force coefficients evaluated. Trends in velocity field degradation with increasing Ro are consistent with previous experimental studies. At low Ro the flow structure generated initially is mostly retained with a strong laminar leading-edge vortex (LEV) and tip vortex (TV). As both Ro and travel distance increase, the flow structure degrades such that at high Ro it begins to resemble that of a translating wing. Additionally, the present study has shown the following. (i) At low Ro the LEV and TV structure is laminar and steady; as Ro increases this structure breaks down, and the location at which it breaks down shifts closer to the wing root. (ii) For moderate Ro of 1.4 and higher, the LEV is no longer steady but enters a shedding regime fed by the leading-edge shear layer. (iii) At the lowest Ro of 0.7 the lift force rises during start-up and then stabilizes, consistent with the flow structure being retained, while for higher Ro a force peak occurs after the initial acceleration is complete, followed by a reduction in lift which appears to correspond to shedding of excess leading-edge vorticity generated during start-up. (iv) All rotating wings produced greater lift than a translating wing, this increase varied from ˜65 % at the lowest Ro=0.7 down to ˜5 % for the highest Ro examined of 9.1.

Complex Pattern Formation from Current-Driven Dynamics of Single-Layer Homoepitaxial Islands on Crystalline Conducting Substrates

NASA Astrophysics Data System (ADS)

Kumar, Ashish; Dasgupta, Dwaipayan; Maroudas, Dimitrios

2017-07-01

We report a systematic study of complex pattern formation resulting from the driven dynamics of single-layer homoepitaxial islands on surfaces of face-centered-cubic (fcc) crystalline conducting substrates under the action of an externally applied electric field. The analysis is based on an experimentally validated nonlinear model of mass transport via island edge atomic diffusion, which also accounts for edge diffusional anisotropy. We analyze the morphological stability and simulate the field-driven evolution of rounded islands for an electric field oriented along the fast edge diffusion direction. For larger-than-critical island sizes on {110 } and {100 } fcc substrates, we show that multiple necking instabilities generate complex island patterns, including not-simply-connected void-containing islands mediated by sequences of breakup and coalescence events and distributed symmetrically with respect to the electric field direction. We analyze the dependence of the formed patterns on the original island size and on the duration of application of the external field. Starting from a single large rounded island, we characterize the evolution of the number of daughter islands and their average size and uniformity. The evolution of the average island size follows a universal power-law scaling relation, and the evolution of the total edge length of the islands in the complex pattern follows Kolmogorov-Johnson-Mehl-Avrami kinetics. Our study makes a strong case for the use of electric fields, as precisely controlled macroscopic forcing, toward surface patterning involving complex nanoscale features.

DOE Office of Scientific and Technical Information (OSTI.GOV)

OWEN,STEVEN J.

A method for decomposing a volume with a prescribed quadrilateral surface mesh, into a hexahedral-dominated mesh is proposed. With this method, known as Hex-Morphing (H-Morph), an initial tetrahedral mesh is provided. Tetrahedral are transformed and combined starting from the boundary and working towards the interior of the volume. The quadrilateral faces of the hexahedra are treated as internal surfaces, which can be recovered using constrained triangulation techniques. Implementation details of the edge and face recovery process are included. Examples and performance of the H-Morph algorithm are also presented.

Numerical Analysis of Flow-Induced Vibrations in Closed Side Branches

NASA Astrophysics Data System (ADS)

KníŽat, Branislav; Troják, Michal

2011-12-01

Vibrations occuring in closed side branches connected to a main pipe are a frequent problem during pipeline system operation. At the design stage of pipeline systems, this problem is sometimes overlooked or underestimated which can later lead to the shortening of the systems life cycle or may even cause injury. The aim of this paper is a numerical analysis of the start of self-induced vibrations on the edge of a closed side branch. Calculation conditions and obtained results are presented within.

Technical progress in silicon sheet growth under DOE/JPL FSA program, 1975-1986

NASA Technical Reports Server (NTRS)

Kalejs, J. P.

1986-01-01

The technical progress made in the Silicon Sheet Growth Program during its 11 years was reviewed. At present, in 1986, only two of the original 9 techniques have survived to the start-up, pilot-plant stage in industry. These two techniques are the edge-defined, film-fed growth (EFG) technique that produces closed shape polygons, and the WEB dendritic technique that produces single ribbons. Both the status and future concerns of the EFG and WEB techniques were discussed.

DARPA Agreement HR0011-06-1-0028 (Robert C. Byrd Institute for Advanced Flexible Manufacturing)

DTIC Science & Technology

2011-12-13

cutting edge design software, state-of-the-art computer labs, manufacturing staff expertise, training resources, as well as video-teleconference...started its own Design Works labs in an effort to provide manufacturers, entrepreneurs, students, machinists and engineers with access to a one-stop...shop and turn their ideas and talent into new products. From a concept drawn on a napkin or the back of an envelope to a 3D design to a working

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dvorak, John

I first stepped through the doorway of the Hawaiian Volcano Observatory in 1976, and I was impressed by what I saw: A dozen people working out of a stone-and-metal building perched at the edge of a high cliff with a spectacular view of a vast volcanic plain. Their primary purpose was to monitor the island's two active volcanoes, Kilauea and Mauna Loa. I joined them, working for six weeks as a volunteer and then, years later, as a staff scientist. That gave me several chances to ask how the observatory had started.