Analysis of Step-Velocity-Dependent Concentration of Magnesium in GaN Based on Burton−Cabrera−Frank Theory and Step-Edge Segregation Model

Based on Burton−Cabrera−Frank theory and the step-edge segregation model, we analyzed the reported difference in the sheet concentration of doped magnesium under naturally formed surface stripes on homo-epitaxially grown layers on a freestanding GaN substrate misoriented from a c-plane by 0.3°. By assuming the step height being equal to the peak-to-valley height of the surface stripes, we considered the growth steps on gently and sharply sloped surfaces to be supplied, respectively, from mixed dislocations and the misorientation from the c-plane. The step-velocity dependence of the magnesium concentration was reproduced with the reported magnesium diffusivity of 3×10−14 cm2s−1.

Step-To-Step Kinematic Validation Between an Inertial Measurement Unit (IMU) 3D System, a Combined Laser+IMU System and Force Plates During a 50 M Sprint in a Cohort of Sprinters

The purpose was to compare step-by-step kinematics measured using force plates (criterion), an IMU only and a combined laser IMU system in well-trained sprinters. Fourteen male experienced sprinters performed a 50-m sprint. Step-by-step kinematics were measured by 50 force plates and compared with an IMU-3D motion capture system and a combined laser+IMU system attached to each foot. Results showed that step kinematics (step velocity, length, contact and flight times) were different when measured with the IMU-3D system, compared with force plates, while the laser+IMU system, showed in general the same kinematics as measured with force plates without a systematic bias. Based upon the findings it can be concluded that the laser+IMU system is as accurate in measuring step-by-step kinematics as the force plate system. At the moment, the IMU-3D system is only accurate in measuring stride patterns (temporal parameters); it is not accurate enough to measure step lengths (spatial) and velocities due to the inaccuracies in step length, especially at high velocities. It is suggested that this laser+IMU system is valid and accurate, which can be used easily in training and competition to obtain step-by step kinematics and give direct feedback of this information during training and competition.

Comparison of development of step-kinematics of assisted 60 m sprints with different pulling forces between experienced male and female sprinters

The purpose of this study was to compare step-by-step kinematics of normal and assisted 60 m sprints with different loads in experienced sprinters. Step-by-step kinematics were measured using inertial measuring units (IMU) integrated with a 3-axis gyroscope and a laser gun in 24 national level male and female sprinters during a normal 60 m sprint and sprints with a 3, 4, and 5 kg pulling force. The main findings were that using increasing assisted loads resulted in faster 60 m times, as a result of higher step velocity mainly caused by longer step lengths in both genders and by shorter contact times in women. Men had longer step lengths, longer contact times, and shorter flight times than women. However, the assisted loads had a greater effect on women than on men, as shown by their larger decrease in sprint times. These time differences in gender were the result of more and longer duration increases in maximal step velocity with increasing assisted loads for women (70–80% of distance) than men (65–70% of distance). This was mainly caused by shorter contact times, and by more increased step lengths in women compared to men. In terms of practical application, it is notable that employing this approach, when using assisted loads can help athletes to reach higher step velocities and hold this for longer, which may be a training impulse to move the speed barrier upwards.

The effect of fatigue on kinematics and kinetics of basketball dribbling with changes of direction

Basketball dribbling is one of the key elements in basketball game. There is a lack of studies investigating the effect of fatigue on kinematics and kinetics in basketball dribbling. There are two primary aims of this study: (1) to explore the effect of fatigue on kinematics and kinetics in dribbling with the change of directions; (2) to determine the effect of fatigue on dribbling speed. Fourteen Croatian senior male basketball players, not power forwards or centers (age: 21.16±3.43 years; body height: 188.81±6.88 cm; body mass: 87.81±6.06 kg; body fat: 13.34±3.52%) participated in the study. Each player performed two types of change of direction (COD) while dribbling: front COD and spin move in the non-fatigued and then in the fatigued state. Xsens suit and Novel insoles were used to measure the kinematic and kinetic parameters. In terms of the front COD, the results of this study demonstrated that the maximum angular velocity in the knee (p=.028) and wrist joint (p=.007) as well as maximum force (p=.004) significantly decreased in the fatigued state. In terms of the spin move, the results showed that there were significant differences in pelvis velocity (p=.000), the maximum angular velocity in the knee joint (p=.020), and the first step velocity (p=0.010) between the fatigued and non-fatigued states. No significant difference was found in the pelvis position, minimum angle in the knee joint and maximum force. Importantly, dribbling speed significantly decreased in the fatigued state (p=.002). The findings of this study suggest that coaching staff should design appropriate training programs to optimize players’ ability to resist fatigue when dribbling under real game speed conditions.

Automated Stage Discrimination of Parkinson’s Disease

Background: Treatment plans for Parkinson’s disease (PD) are based on a disease stage scale, which is generally determined using a manual, observational procedure. Automated, sensor-based discrimination saves labor and costs in clinical settings and may offer augmented stage determination accuracy. Previous automated devices were either cumbersome or costly and were not suitable for individuals who cannot walk without support.Methods: Since 2017, a device has been available that successfully detects PD and operates for people who cannot walk without support. In the present study, the suitability of this device for automated discrimination of PD stages was tested. The device consists of a walking frame fitted with sensors to simultaneously support walking and monitor patient gait. Sixty-five PD patients in Hoehn and Yahr (HY) stages 1 to 4 and 24 healthy controls were subjected to supported Timed Up and Go (TUG) tests, while using the walking frame. The walking trajectory, velocity, acceleration and force were recorded by the device throughout the tests. These physical parameters were converted into symptomatic spatiotemporal quantities that are conventionally used in PD gait assessment.Results: An analysis of variance (ANOVA) test extended by a confidence interval (CI) analysis indicated statistically significant separability between HY stages for the following spatiotemporal quantities: TUG time (p < 0.001), straight line walking time (p < 0.001), turning time (p < 0.001), and step count (p < 0.001). A negative correlation was obtained for mean step velocity (p < 0.001) and mean step length (p < 0.001). Moreover, correlations were established between these, as well as additional spatiotemporal quantities, and disease duration, L-dihydroxyphenylalanine-(L-DOPA) dose, motor fluctuation, dyskinesia and the mobile part of the Unified Parkinson Disease Rating Scale (UPDRS).Conclusions: We have proven that stage discrimination of PD can be automated, even to patients who cannot support themselves. A similar method might be successfully applied to other gait disorders.

Vestibular Test Results of a Patient with Cerebral Microangiopathy and Idiopathic Thrombocytopenia

Background Cerebral microangiopathy (CM) is a general term for small ischemic changes related to small blood vessels in the brain. Immune thrombocytopenia (ITP) is a rare acquired autoimmune disease that is characterized by low platelet count and increased risk of hemorrhage. We describe vestibular testing completed on a 64-year-old patient with CM and ITP presenting with complaints of general instability and listing while walking, decreased stability in dark environments, and blurred vision with head movement. Results indicated a severe loss of horizontal semicircular canal function bilaterally with a somatosensory-dependent pattern of postural instability. Purpose This case emphasizes the importance of vestibular testing to determine the level of involvement of the vestibular system in the patient's symptomatology with known CM. Due to the increased risk of severe injury in those with ITP and the unknown effects this may have on the vestibular and balance systems, what is known about the pathophysiology of ITP and possible implications are reviewed. Research Design Case report. Data Collection and Analysis Previous audiological and medical records were obtained. Vestibular testing included videonystagmography; video head impulse test (vHIT); rotational chair including sinusoidal harmonic acceleration (SHA), step velocity, SHA with fixation, and visual vestibular SHA; computerized dynamic posturography battery including sensory organization test (SOT), motor control test, and adaptation test. Results Audiological evaluation indicated a mild to moderately severe sensorineural hearing loss bilaterally. Ocular motor evaluation results indicated abnormal “cog-wheel” like tracings in smooth pursuit, hypometric saccades with abnormally increased latencies and reduced optokinetic gain. The patient also demonstrated apogeotropic nystagmus during head/body right and head/body left positions when fixation was denied. Bilateral bithermal calorics indicated a bilateral hypofunction. Horizontal vHIT results indicated reduced gain bilaterally. SHA results confirmed significant gain reductions at all frequencies tested and step velocity results indicated reduced gain and reduced time constants during all prerotary and postrotary measures. SOT results indicated a somatosensory-dependent pattern (i.e., reduced equilibrium index scores and falls in conditions 4, 5, and 6). Conclusions These findings emphasize the importance of comprehensive vestibular evaluations of patients with CM, ITP, and complaints of instability. Identification and quantification of residual peripheral vestibular function as well as central system involvement can provide significant information pertinent to falls risk reduction and vestibular rehabilitation strategies, outcomes, and goals.

Importance of Footwear Outsole Rigidity in Improving Spatiotemporal Parameters in Patients with Diabetes and Previous Forefoot Ulcerations

We aimed to identify if any differences existed in spatiotemporal parameters during gait among different densities of rocker soles in patients with a history of neuropathic ulcerations and the differences in comfort between shoe conditions. This study was a cross-sectional study of 24 patients with diabetes and a history of neuropathic diabetic foot ulcers (DFUs). Spatiotemporal parameters (duration of stance phase (ms), stride length (cm), and step velocity (m/s)) were analyzed in barefoot, semirigid outsole, and rigid outsole footwear conditions. A dynamic pressure measurement system (Footscan® system, RSscan International, Olen, Belgium) was used to assess shoe conditions. We also analyzed differences in comfort between the shoe conditions using a visual analog scale. A Wilcoxon test for paired samples was used to assess gait differences. Result showed that a rigid outsole causes changes in the subphases of the stance phase (p < 0.001; Cohen d = 0.6) compared to a semirigid outsole. Stride length (p < 0.001; Cohen d = 0.66) and step velocity were significantly longer (p < 0.001; Cohen d = 2.03) with the use of rigid outsole footwear. A rigid rocker sole reduces the time of the stance phase, in addition to increasing the stride length and velocity of step in patients with a previous history of DFUs.