2,237 research outputs found
Real-Time Analysis of Correlations Between On-Body Sensor Nodes
The topology of a body sensor network has, until recently, often been overlooked; either because the layout of the network is deemed to be sufficiently static (âwe always know well enough where sensors areâ), we always know exactly where the nodes are or because the location of the sensor is not inherently required (âas long as the node stays where it is, we do not need its location, just its dataâ). We argue in this paper that, especially as the sensor nodes become more numerous and densely interconnected, an analysis on the correlations between the data streams can be valuable for a variety of purposes. Two systems illustrate how a mapping of the networkâs sensor data to a topology of the sensor nodesâ correlations can be applied to reveal more about the physical structure of body sensor networks
The Impact of Health Reform on Health System Spending
Examines the 2010 healthcare reform law's impact on national health expenditures, through new coverage, savings in public programs, insurance exchanges, and health system modernization; the federal budget; Medicare; and premiums for private coverage
Anticipatory Effects on Lower Extremity Neuromechanics During a Cutting Task
Context: Continued research into the mechanism of noncontact anterior cruciate ligament injury helps to improve clinical interventions and injury-prevention strategies. A better understanding of the effects of anticipation on landing neuromechanics may benefit training interventions.
Objective: To determine the effects of anticipation on lower extremity neuromechanics during a single-legged land-and-cut task.
Design: Controlled laboratory study.
Setting: University biomechanics laboratory.
Participants: Eighteen female National Collegiate Athletic Association Division I collegiate soccer players (age = 19.7 ± 0.8 years, height = 167.3 ± 6.0 cm, mass = 66.1 ± 2.1 kg).
Intervention(s): Participants performed a single-legged land-and-cut task under anticipated and unanticipated conditions.
Main Outcome Measure(s): Three-dimensional initial contact angles, peak joint angles, and peak internal joint moments and peak vertical ground reaction forces and sagittal-plane energy absorption of the 3 lower extremity joints; muscle activation of selected hip- and knee-joint muscles.
Results: Unanticipated cuts resulted in less knee flexion at initial contact and greater ankle toe-in displacement. Unanticipated cuts were also characterized by greater internal hip-abductor and external-rotator moments and smaller internal knee-extensor and external-rotator moments. Muscle-activation profiles during unanticipated cuts were associated with greater activation of the gluteus maximus during the precontact and landing phases.
Conclusions: Performing a cutting task under unanticipated conditions changed lower extremity neuromechanics compared with anticipated conditions. Most of the observed changes in lower extremity neuromechanics indicated the adoption of a hip-focused strategy during the unanticipated condition
Spinal and Supraspinal Motor Control Predictors of Rate of Torque Development
During explosive movements and potentially injurious situations, the ability to rapidly generate torque is critical. Previous research has suggested that different phases of rate of torque development (RTD) are differentiately controlled. However, the extent to which supraspinal and spinal mechanisms predict RTD at different time intervals is unknown. RTD of the plantarflexors across various phases of contraction (i.e., 0â25, 0â50, 0â100, 0â150, 0â200, and 0â250âms) was measured in 37 participants. The following predictor variables were also measured: (a) gain of the resting soleus H-reflex recruitment curve; (b) gain of the resting homonymous post-activation depression recruitment curve; (c) gain of the GABAergic presynaptic inhibition recruitment curve; (d) the level of postsynaptic recurrent inhibition at rest; (e) level of supraspinal drive assessed by measuring V waves; and (f) the gain of the resting soleus M wave. Stepwise regression analyses were used to determine which variables significantly predicted allometrically scaled RTD. The analyses indicated that supraspinal drive was the dominant predictor of RTD across all phases. Additionally, recurrent inhibition predicted RTD in all of the time intervals except 0â150âms. These results demonstrate the importance of supraspinal drive and recurrent inhibition to RTD
Fat Fisher Zeroes
We show that it is possible to determine the locus of Fisher zeroes in the
thermodynamic limit for the Ising model on planar (``fat'') phi4 random graphs
and their dual quadrangulations by matching up the real part of the high and
low temperature branches of the expression for the free energy. The form of
this expression for the free energy also means that series expansion results
for the zeroes may be obtained with rather less effort than might appear
necessary at first sight by simply reverting the series expansion of a function
g(z) which appears in the solution and taking a logarithm.
Unlike regular 2D lattices where numerous unphysical critical points exist
with non-standard exponents, the Ising model on planar phi4 graphs displays
only the physical transition at c = exp (- 2 beta) = 1/4 and a mirror
transition at c=-1/4 both with KPZ/DDK exponents (alpha = -1, beta = 1/2, gamma
= 2). The relation between the phi4 locus and that of the dual quadrangulations
is akin to that between the (regular) triangular and honeycomb lattices since
there is no self-duality.Comment: 12 pages + 6 eps figure
The Association of Dorsiflexion Flexibility on Knee Kinematics and Kinetics during a Drop Vertical Jump in Healthy Female Athletes
Purpose
While previous studies have examined the association between ankle dorsiflexion flexibility and deleterious landing postures, it is not currently known how landing kinetics are influenced by ankle dorsiflexion flexibility. The purpose of this study was to examine whether ankle dorsiflexion flexibility was associated with landing kinematics and kinetics that have been shown to increase the risk of anterior cruciate ligament (ACL) injury in female athletes.
Methods
Twenty-three female collegiate soccer players participated in a preseason screening that included the assessment of ankle dorsiflexion flexibility and lower-body kinematics and kinetics during a drop vertical jump task.
Results
The results demonstrated that females with less ankle dorsiflexion flexibility exhibited greater peak knee abduction moments (r = â.442), greater peak knee abduction angles (r = .355), and less peak knee flexion angles (r = .385) during landing. The range of dorsiflexion flexibility for the current study was between 9° and 23° (mean = 15.0°; SD 3.9°).
Conclusion
Dorsiflexion flexibility may serve as a useful clinical measure to predict poor landing postures and external forces that have been associated with increased knee injury risk. Rehabilitation specialists can provide interventions aimed at improving dorsiflexion flexibility in order to ameliorate the impact of this modifiable factor on deleterious landing kinematics and kinetics in female athletes
Nucleation rates from small scale atomistic simulations and transition state theory
The evaluation of nucleation rates from molecular dynamics trajectories is
hampered by the slow nucleation time scale and impact of finite size effects.
Here, we show that accurate nucleation rates can be obtained in a very general
fashion relying only on the free energy barrier, transition state theory (TST),
and a simple dynamical correction for diffusive recrossing. In this setup, the
time scale problem is overcome by using enhanced sampling methods, in casu
metadynamics, whereas the impact of finite size effects can be naturally
circumvented by reconstructing the free energy surface from an appropriate
ensemble. Approximations from classical nucleation theory are avoided. We
demonstrate the accuracy of the approach by calculating macroscopic rates of
droplet nucleation from argon vapor, spanning sixteen orders of magnitude and
in excellent agreement with literature results, all from simulations of very
small (512 atom) systems
Hip External Rotator Strength Is Associated With Better Dynamic Control of the Lower Extremity During Landing Tasks
Hip external rotator strength is associated with better dynamic control of the lower extremity during landing tasks. J Strength Cond Res 30(1): 282â291, 2016âThe purpose of this study was to determine the association between hip strength and lower extremity kinematics and kinetics during unanticipated single-leg landing and cutting tasks in collegiate female soccer players. Twenty-three National Collegiate Athletic Association division I female soccer players were recruited for strength testing and biomechanical analysis. Maximal isometric hip abduction and external rotation strength were measured using a hand-held dynamometer and expressed as muscle torque (force Ă femoral length) and normalized to body weight. Three-dimensional lower extremity kinematics and kinetics were assessed with motion analysis and force plates, and an inverse dynamics approach was used to calculate net internal joint moments that were normalized to body weight. Greater hip external rotator strength was significantly associated with greater peak hip external rotation moments (r = 0.47; p = 0.021), greater peak knee internal rotation moments (r = 0.41; p = 0.048), greater hip frontal plane excursion (r = 0.49; p = 0.017), and less knee transverse plane excursion (r = -0.56; p = 0.004) during unanticipated single-leg landing and cutting tasks. In addition, a statistical trend was detected between hip external rotator strength and peak hip frontal plane moments (r = 0.39; p = 0.06). The results suggest that females with greater hip external rotator strength demonstrate better dynamic control of the lower extremity during unanticipated single-leg landing and cutting tasks and provide further support for the link between hip strength and lower extremity landing mechanics
Comparing soil boundaries delineated by digital analysis of multispectral scanner data from high and low spatial resolution systems
The author has identified the following significant results. Computer-aided analysis techniques used with aircraft MSS data showed that the spatial resolution was sufficient to recognize each soil mapping unit of the test site. Some difficulties occurred where different soil series were intricately mixed, and this mixture showed as a separate spectral mapping unit, or where the difference between two soils depended on the depth of silty surface material. Analysis of LANDSAT data with computer-aided techniques showed that it was not possible to find spectrally homogeneous soil features of the seven soil series on the 40 ha test site on the digital display or on a picture print map. Cluster techniques could be used on an extended test area to group spectrally similar data points into cluster classes
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