Kinematic Effects of Stride Length Perturbations on System COM Horizontal Velocity During Locomotion

PURPOSE: To investigate the kinematic effect on the systems’ center of mass horizontal velocity in response to stride length perturbations. METHODS: Twelve healthy adults (23.1±7.71 yrs; 1.69±0.1 m; 66.82±12.6 kg; leg length 894.7±66.1 mm) performed 5 trials of preferred speed walking (PW) and running (PR)followed by 5 stride length perturbations based on percentages of leg length (60%, 80%, 100%, 120% and 140%). 3D kinematic analysis was completed using a 12-camera infrared motion capture system (Vicon, 200hz). Dependent variables computer for each condition included: center of mass horizontal velocity at the highest vertical position (COMHVhi) and at the lowest vertical position (COMHVlo). Statistical analysis included correlation matrices across levels of perturbation for each dependent variable (α=.05). RESULTS: COMHVhi demonstrated significant correlations with greater than 50% shared variance for PR vs 100% (r=.742), 60% vs 80% (r=.824), 60% vs 100% (r=.748), 60% vs 120% (r=.709), 80% vs 100% (r=.896), 100% vs 120% (r=.887), and 100% vs 140% (r=.728), and 120% vs 140% (r=.895). COMHVlo demonstrated significant correlations with greater than 50% shared variance for PR vs 100% (r=.753), PW vs 80% (r=.794), 60% vs 80% (r=.814), 60% vs 100% (r=.735), 60% vs 120% (r=.748), 80% vs 100% (r=.902), 80% vs 120% (r=.751), 100% vs 120% (r=.892), and 120% vs 140% (r=.710). DISCUSSION: Results suggest PR and PW have a greater relationship to stride length less than or equal to leg length, and thus extending stride length begins to diminish mechanical efficiency. It is a well-established mechanical relationship that horizontal velocity is a product of stride length and stride rate. Study results suggest that increases in stride length beyond 100% of leg length may be less than optimal mechanically. CONCLUSION: Stride lengths greater than 100% leg length during walking may be inefficient, perhaps owing to changes in lower extremity stiffness

Step Length Perturbations Alter Variations in Center of Mass Horizontal Velocity

PURPOSE: The purpose of the study was to investigate the effects of SL perturbations on system COM forward velocity (vx) during walking gait. METHODS: Eight healthy adults (23.5±3.6 yrs; 1.72±0.18 m; 73.11±15.29 kg) performed 5 trials of preferred speed walking (PW) and running (PR) followed by 5 stride length perturbations based on percentages of leg length (LL: 60%, 80%, 100%, 120% and 140%). 3D kinematic analysis was completed using a 12-camera infrared motion capture system (Vicon MX T40-S, 200Hz). Data filtering and interpolation included a low pass, 4th order Butterworth filter (cutoff frequency 15Hz) and cubic (3rd order spline). Maximum and minimum system COMvx comparisons were made independently among stride conditions using one-way repeated measures ANOVA and Bonferroni post-hoc contrasts. Change in system COMvx across gait stride were evaluated using one-way repeated measures ANOVA and Bonferroni post-hoc contrasts (α=0.05). RESULTS: Differences in maximum COMvx were detected among stride conditions (F[1.847,59.105]=339.458, pdetected among stride conditions (F[2.118,65.666] =130.951, pdetected significantly greater ΔCOMvx at 140% LL, and significantly less ΔCOMvx at 60% LL (p≤.005). DISCUSSION: Differences in maximum COMvx were detected among stride conditions (F[1.847,59.105]=339.458,

Individual and combined impact of hypoxia and acute inorganic nitrate ingestion on autonomic thermoregulatory responses to the cold [Abstract]

No description supplie

Imaging protoplanets: observing transition disks with non-redundant masking

Transition disks, protoplanetary disks with inner clearings, are promising objects in which to directly image forming planets. The high contrast imaging technique of non-redundant masking is well posed to detect planetary mass companions at several to tens of AU in nearby transition disks. We present non-redundant masking observations of the T Cha and LkCa 15 transition disks, both of which host posited sub-stellar mass companions. However, due to a loss of information intrinsic to the technique, observations of extended sources (e.g. scattered light from disks) can be misinterpreted as moving companions. We discuss tests to distinguish between these two scenarios, with applications to the T Cha and LkCa 15 observations. We argue that a static, forward-scattering disk can explain the T Cha data, while LkCa 15 is best explained by multiple orbiting companions.Comment: SPIE conference proceedin

Independent and combined impact of hypoxia and acute inorganic nitrate ingestion on thermoregulatory responses to the cold

Purpose: This study assessed the impact of normobaric hypoxia and acute nitrate ingestion on shivering thermogenesis, cutaneous vascular control, and thermometrics in response to cold stress. Method: Eleven male volunteers underwent passive cooling at 10 °C air temperature across four conditions: (1) normoxia with placebo ingestion, (2) hypoxia (0.130 FiO2) with placebo ingestion, (3) normoxia with 13 mmol nitrate ingestion, and (4) hypoxia with nitrate ingestion. Physiological metrics were assessed as a rate of change over 45 min to determine heat loss, and at the point of shivering onset to determine the thermogenic thermoeffector threshold. Result: Independently, hypoxia expedited shivering onset time (p = 0.05) due to a faster cooling rate as opposed to a change in central thermoeffector thresholds. Specifically, compared to normoxia, hypoxia increased skin blood flow (p = 0.02), leading to an increased core-cooling rate (p = 0.04) and delta change in rectal temperature (p = 0.03) over 45 min, yet the same rectal temperature at shivering onset (p = 0.9). Independently, nitrate ingestion delayed shivering onset time (p = 0.01), mediated by a change in central thermoeffector thresholds, independent of changes in peripheral heat exchange. Specifically, compared to placebo ingestion, no difference was observed in skin blood flow (p = 0.5), core-cooling rate (p = 0.5), or delta change in rectal temperature (p = 0.7) over 45 min, while nitrate reduced rectal temperature at shivering onset (p = 0.04). No interaction was observed between hypoxia and nitrate ingestion. Conclusion: These data improve our understanding of how hypoxia and nitric oxide modulate cold thermoregulation

Applications of advanced metrology for understanding the effects of drying temperature in the lithium-ion battery electrode manufacturing process

The performance of lithium-ion batteries is determined by the architecture and properties of electrodes formed during manufacturing, particularly in the drying process when solvent is removed and the electrode structure is formed. Temperature is one of the most dominant parameters that influences the process, and therefore a comparison of temperature effects on both NMC622-based cathodes (PVDF-based binder) and graphite-based anodes (water-based binder) dried at RT, 60, 80, 100 and 120 °C has been undertaken. X-ray computed tomography showed that NMC622 particles concentrated at the surface of the cathode coating except when dried at 60 °C. However, anodes showed similar graphite distributions at all temperatures. The discharge capacities for the cathodes dried at 60, 80, 100 and 120 °C displayed the following trend: 60 °C < 80 °C < 100 °C < 120 °C as C-rate was increased which was consistent with the trends found in adhesion testing between 60 and 120 °C. Focused-ion beam scanning electrode microscopy and energy-dispersive X-ray spectroscopy suggested that the F-rich binder distribution was largely insensitive to temperature for cathodes. In contrast, conductivity enhancing fine carbon agglomerated on the upper surface of the active NMC particles in the cathode as temperature increased. The cathode dried at RT had the highest adhesion force of 0.015 N mm−1 and the best electrochemical rate performance. Conversely, drying temperature had no significant effect on the electrochemical performance of the anode, which was consistent with only a relatively small change in the adhesion, related to the use of lower adhesion water-based binders

Dendritic silver self-assembly in molten-carbonate membranes for efficient carbon dioxide capture

Membranes for CO2 capture should offer high permeant fluxes to keep membrane surface area small and material requirements low. Ag-supported, dual-phase, molten-carbonate membranes routinely demonstrate the highest CO2 fluxes in this class of membrane. However, using Ag as a support incurs high cost. Here, the non-equilibrium conditions of permeation were exploited to stimulate the self-assembly of a percolating, dendritic network of Ag from the molten carbonate. Multiple membrane support geometries and Ag incorporation methods were employed, demonstrating the generality of the approach, while X-ray micro-computed tomography confirmed that CO2 and O2 permeation stimulated self-assembly. We report the highest flux of Ag-supported molten-salt membranes to date (1.25 ml min−1 cm−2 at 650 °C) and ultrahigh permeability (9.4 × 10−11 mol m−1 s−1 Pa−1), surpassing the permeability requirement for economically-competitive post-combustion CO2 capture, all whilst reducing the membrane-volume-normalised demand for Ag by one order of magnitude

High contrast imaging at the LBT: the LEECH exoplanet imaging survey

In Spring 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began its $\sim$130-night campaign from the Large Binocular Telescope (LBT) atop Mt Graham, Arizona. This survey benefits from the many technological achievements of the LBT, including two 8.4-meter mirrors on a single fixed mount, dual adaptive secondary mirrors for high Strehl performance, and a cold beam combiner to dramatically reduce the telescope's overall background emissivity. LEECH neatly complements other high-contrast planet imaging efforts by observing stars at L' (3.8 $\mu$m), as opposed to the shorter wavelength near-infrared bands (1-2.4 $\mu$m) of other surveys. This portion of the spectrum offers deep mass sensitivity, especially around nearby adolescent ($\sim$0.1-1 Gyr) stars. LEECH's contrast is competitive with other extreme adaptive optics systems, while providing an alternative survey strategy. Additionally, LEECH is characterizing known exoplanetary systems with observations from 3-5$\mu$m in preparation for JWST.Comment: 12 pages, 5 figures. Proceedings of the SPIE, 9148-2

Cardigan: SDN distributed routing fabric going live at an Internet exchange

Software Defined Networking (SDN) is an active area for network research, with many organizations exploring the opportunities provided by the decoupling of network control from packet forwarding. However, questions remain over the operation of such systems in production. In order to build operational confidence, we built Cardigan -a distributed router using OpenFlow-and deployed it at a public Internet exchange. Cardigan applies a routing as a service abstraction to a RouteFlow controlled IP network in an effort to reduce operational complexity. The implementation and deployment efforts provide insights into the challenges involved with using these technologies, and suggests the viability of mixed device environments despite the limitations of early OpenFlow implementations