Effects of an attention demanding task on dynamic stability during treadmill walking

<p>Abstract</p> <p>Background</p> <p>People exhibit increased difficulty balancing when they perform secondary attention-distracting tasks while walking. However, a previous study by Grabiner and Troy (<it>J. Neuroengineering Rehabil</it>., 2005) found that young healthy subjects performing a concurrent Stroop task while walking on a motorized treadmill exhibited <it>decreased </it>step width variability. However, measures of variability do not directly quantify how a system responds to perturbations. This study re-analyzed data from Grabiner and Troy 2005 to determine if performing the concurrent Stroop task directly affected the dynamic stability of walking in these same subjects.</p> <p>Methods</p> <p>Thirteen healthy volunteers walked on a motorized treadmill at their self-selected constant speed for 10 minutes both while performing the Stroop test and during undisturbed walking. This Stroop test consisted of projecting images of the name of one color, printed in text of a different color, onto a wall and asking subjects to verbally identify the color of the text. Three-dimensional motions of a marker attached to the base of the neck (C5/T1) were recorded. Marker velocities were calculated over 3 equal intervals of 200 sec each in each direction. Mean variability was calculated for each time series as the average standard deviation across all strides. Both "local" and "orbital" dynamic stability were quantified for each time series using previously established methods. These measures directly quantify how quickly small perturbations grow or decay, either continuously in real time (local) or discretely from one cycle to the next (orbital). Differences between Stroop and Control trials were evaluated using a 2-factor repeated measures ANOVA.</p> <p>Results</p> <p>Mean variability of trunk movements was significantly reduced during the Stroop tests compared to normal walking. Conversely, local and orbital stability results were mixed: some measures showed slight increases, while others showed slight decreases. In many cases, different subjects responded differently to the Stroop test. While some of our comparisons reached statistical significance, many did not. In general, measures of variability and dynamic stability reflected different properties of walking dynamics, consistent with previous findings.</p> <p>Conclusion</p> <p>These findings demonstrate that the decreased movement variability associated with the Stroop task did <it>not </it>translate to greater dynamic stability.</p

Performance-Based Planning: Perspectives from the United States, Australia, and New Zealand

This article examines the application of performance-based planning at the local level in the United States, Australia, and New Zealand. A review of the literature finds that there have been few evaluations of performance-based planning, despite its being used by many governments. The authors provide a comparative review of the experiences of various jurisdictions in implementing this form of zoning and present observations on its relative strengths and weaknesses. Findings suggest that many of the jurisdictions that adopted performance-based planning subsequently abandoned it because of the heavy administrative burden required, and where performance methods survived, they were typically hybridized with traditional zoning. If performance-based approaches continue to be used, there is a need to better understand the administrative and implementation implications of this type of land use regulation

Biasing experiments on the ATF torsatron

Recent biasing experiments on tokamaks have been very successful in improving the global particle (H-mode-like) confinement resulting from the setup of an outward-pointing radial electric field at the edge. These experiments have been extended to the current-free Advanced Toroidal Facility (ATF), and initial biasing experiments have been carried out in electron-cyclotron-heated (ECH) plasmas. ATF has a torsatron configuration with {ell} = 2, 12 field periods (M = 12), a major radius R{sub 0} = 2.1 m, and an average plasma radius a = 0.27 m. The current-free magnetic configuration of ATF that is produced by external means has moderate shear; the rotational transform ({chi} = 1/q, where q is the safety factor) at the last closed flux surface (LCFS) is {chi} {approx} 1, which is about a factor of 3 higher than the central value. ECH plasmas are created at a magnetic field B = 0.95 T using a 53-GHz gyrotron source with heating power up to P {approximately} 400 kW. In these ECH plasmas, a representative line-averaged plasma density is {bar n}{sub e} {approximately} 5 {times} 10{sup 12} cm{sup {minus}3}, and the plasma stored energy W{sub p} {approx} 2 kJ. A pair of rail limiters, which are normally floating, one at the top and one at the bottom of the device, are biased at positive and negative potentials with respect to the vessel. 7 refs., 5 figs

Urban Sustainability: Integrating Ecology in City Design and Planning

Urban sustainability depends on ecosystem services and biodiversity which directly affects quality of urban life. At present, urbanization is having a drastic effect on the way human beings interact with the world around us. Urbanized environments tend to lessen the amount of habitat and increase habitat fragmentation. This important factor stresses the need for sound urban sustainability thinking as well as related urban planning and urban design processes. Adaptive urban knowhow is as the root of this chapter in which a number of exploratory concepts and notions are put forth with the intention of creating dialogue between ecosystem services and human well-being (i.e., through concerted ecological, economic, and social action). The chapter begins with a look at urban sustainability, explores sustainable urban strategies, considers a number of ideas under the umbrella of urban green infrastructure—reviewing a number of case examples—and concludes with background research in properly developing sustainable models and tools. Integrating ecology in city design and planning should support resilience orient development and highlight a synergetic, evolutionary form of multidisciplinary sustainability

Coronal Heating as Determined by the Solar Flare Frequency Distribution Obtained by Aggregating Case Studies

Flare frequency distributions represent a key approach to addressing one of the largest problems in solar and stellar physics: determining the mechanism that counter-intuitively heats coronae to temperatures that are orders of magnitude hotter than the corresponding photospheres. It is widely accepted that the magnetic field is responsible for the heating, but there are two competing mechanisms that could explain it: nanoflares or Alfv\'en waves. To date, neither can be directly observed. Nanoflares are, by definition, extremely small, but their aggregate energy release could represent a substantial heating mechanism, presuming they are sufficiently abundant. One way to test this presumption is via the flare frequency distribution, which describes how often flares of various energies occur. If the slope of the power law fitting the flare frequency distribution is above a critical threshold, $\alpha=2$ as established in prior literature, then there should be a sufficient abundance of nanoflares to explain coronal heating. We performed $>$600 case studies of solar flares, made possible by an unprecedented number of data analysts via three semesters of an undergraduate physics laboratory course. This allowed us to include two crucial, but nontrivial, analysis methods: pre-flare baseline subtraction and computation of the flare energy, which requires determining flare start and stop times. We aggregated the results of these analyses into a statistical study to determine that $\alpha = 1.63 \pm 0.03$. This is below the critical threshold, suggesting that Alfv\'en waves are an important driver of coronal heating.Comment: 1,002 authors, 14 pages, 4 figures, 3 tables, published by The Astrophysical Journal on 2023-05-09, volume 948, page 7