Physical activity, motor competence and movement and gait quality: A principal component analysis

ObjectiveWhile novel analytical methods have been used to examine movement behaviours, to date, no studies have examined whether a frequency-based measure, such a spectral purity, is useful in explaining key facets of human movement. The aim of this study was to investigate movement and gait quality, physical activity and motor competence using principal component analysis.MethodsSixty-five children (38 boys, 4.3 ± 0.7y, 1.04 ± 0.05 m, 17.8 ± 3.2 kg, BMI; 16.2 ± 1.9 kg∙m2) took part in this study. Measures included accelerometer-derived physical activity and movement quality (spectral purity), motor competence (Movement Assessment Battery for Children 2nd edition; MABC2), height, weight and waist circumference. All data were subjected to a principal component analysis, and the internal consistency of resultant components were assessed using Cronbach's alpha.ResultsTwo principal components, with excellent internal consistency (Cronbach α >0.9) were found; the 1st principal component, termed “movement component”, contained spectral purity, traffic light MABC2 score, fine motor% and gross motor% (α = 0.93); the 2nd principal component, termed “anthropometric component”, contained weight, BMI, BMI% and body fat% (α = 0.91).ConclusionThe results of the present study demonstrate that accelerometric analyses can be used to assess motor competence in an automated manner, and that spectral purity is a meaningful, indicative, metric related to children's movement quality

Profiling Movement Quality Characteristics of Children (9-11y) During Recess

Introduction. Frequency spectrum characteristics derived from raw accelerometry, such as spectral purity, have the potential to reveal detailed information about children’s movement quality, but remain unexplored in children’s physical activity. The aim of this study was to investigate and profile children’s recess physical activity and movement quality using a novel analytical approach. Materials and Methods. A powered sample of twenty-four children (18 boys) (10.5±0.6y, 1.44±0.09m, 39.6±9.5kg, body mass index; 18.8±3.1 kg.m2) wore an ankle-mounted accelerometer during school recess, for one school-week. Hierarchical clustering, Spearman’s rho and the Mann-Whitney U test were used to assess relationships between characteristics, and to assess inter-day differences. Results. There were no significant inter-day differences found for overall activity (P>0.05), yet significant differences were found for spectral purity derived movement quality (P 0.05), sin embargo, se encontraron diferencias significativas para la calidad del movimiento derivado de la pureza espectral (P <0.001). La actividad global se agrupó jerárquicamente y se correlacionó positivamente con la pureza espectral (P <0,05). Discusión. Este es el primer estudio que informa la pureza espectral de la calidad del movimiento derivado de la actividad física de los niños, en un entorno no controlado y nuestros resultados destacan el potencial para la investigación futura

Dirac-like Plasmons in Honeycomb Lattices of Metallic Nanoparticles

Copyright © 2013 American Physical SocietyWe consider a two-dimensional honeycomb lattice of metallic nanoparticles, each supporting a localized surface plasmon, and study the quantum properties of the collective plasmons resulting from the near-field dipolar interaction between the nanoparticles. We analytically investigate the dispersion, the effective Hamiltonian, and the eigenstates of the collective plasmons for an arbitrary orientation of the individual dipole moments. When the polarization points close to the normal to the plane, the spectrum presents Dirac cones, similar to those present in the electronic band structure of graphene. We derive the effective Dirac Hamiltonian for the collective plasmons and show that the corresponding spinor eigenstates represent Dirac-like massless bosonic excitations that present similar effects to electrons in graphene, such as a nontrivial Berry phase and the absence of backscattering off smooth inhomogeneities. We further discuss how one can manipulate the Dirac points in the Brillouin zone and open a gap in the collective plasmon dispersion by modifying the polarization of the localized surface plasmons, paving the way for a fully tunable plasmonic analogue of graphene

Calibration of the APEX Model to Simulate Management Practice Effects on Runoff, Sediment, and Phosphorus Loss

Process-based computer models have been proposed as a tool to generate data for Phosphorus (P) Index assessment and development. Although models are commonly used to simulate P loss from agriculture using managements that are different from the calibration data, this use of models has not been fully tested. The objective of this study is to determine if the Agricultural Policy Environmental eXtender (APEX) model can accurately simulate runoff, sediment, total P, and dissolved P loss from 0.4 to 1.5 ha of agricultural fields with managements that are different from the calibration data. The APEX model was calibrated with field-scale data from eight different managements at two locations (management-specific models). The calibrated models were then validated, either with the same management used for calibration or with different managements. Location models were also developed by calibrating APEX with data from all managements. The management-specific models resulted in satisfactory performance when used to simulate runoff, total P, and dissolved P within their respective systems, with r2 \u3e 0.50, Nash– Sutcliffe efficiency \u3e 0.30, and percent bias within ±35% for runoff and ±70% for total and dissolved P. When applied outside the calibration management, the management-specific models only met the minimum performance criteria in one-third of the tests. The location models had better model performance when applied across all managements compared with management-specific models. Our results suggest that models only be applied within the managements used for calibration and that data be included from multiple management systems for calibration when using models to assess management effects on P loss or evaluate P Indices

A Kinematic Analysis of Fundamental Movement Skills

Abstract Fundamental movement skills are considered the basic building blocks for movement and provide the foundation for specialized and sport-specific movement skills required for participation in a variety of physical activities. However, kinematic analyses of fundamental movement has not been performed. The aims of this study were to, (1) characterise the relationship between facets of fundamental movement and, (2) characterise the relationship between overall integrated acceleration and three-dimensional kinematic variables whilst performing fundamental movement skills. Eleven participants (10±0.8y, 1.41±0.07m, 33.4±8.6kg, body mass index; 16.4±3.1 kg·m2) took part in this study, had anthropometric variables recorded and performed a series of fundamental movement tasks, whilst wearing a tri-axial accelerometer and were recorded using a three-dimensional motion capture system. Maximum shoulder external rotation (°) and maximum shoulder internal rotation velocity (°.s−1) (r=0.86, p&lt;0.001), mediolateral centre of mass range (cm) and centre of mass coefficient of variation (%) (r=0.83, p&lt;0.001), maximum stride angle (°) in the jog and walk (r=0.74, p=0.01) and maximum sprint stride angle and maximum shoulder internal rotation velocity (°.s−1) (r=0.67, p&lt;0.02) were significantly correlated. Maximum sprint stride angle (hip: r=0.96, p&lt;0.001, ankle: r=0.97, p&lt;0.001) and maximum internal rotation velocity (ankle: r=0.6, p=0.05) were significantly correlated to overall integrated acceleration. Overall integrated acceleration was comparable between participants (CV: 10.5), whereas three-dimensional variables varied by up to 65%. Although overall integrated acceleration was comparable between participants, three-dimensional variables were much more varied. Indicating that although overall activity may be correspondent, the characteristics of a child’s movement may be highly varied.</jats:p

Mass of the Southern Black Hole in NGC 6240 from Laser Guide Star Adaptive Optics

NGC 6240 is a pair of colliding disk galaxies, each with a black hole in its core. We have used laser guide star adaptive optics on the Keck II telescope to obtain high-resolution ($\sim 0.06$") near-infrared integral-field spectra of the region surrounding the supermassive black hole in the south nucleus of this galaxy merger. We use the K-band CO absorption bandheads to trace stellar kinematics. We obtain a spatial resolution of about 20 pc and thus directly resolve the sphere of gravitational influence of the massive black hole. We explore two different methods to measure the black hole mass. Using a Jeans Axisymmetric Multi-Gaussian mass model, we investigate the limit that a relaxed mass distribution produces all of the measured velocity dispersion, and find an upper limit on the black hole mass at 2.0 \pm 0.2 \times 10^9 M_{\sun}. When assuming the young stars whose spectra we observe remain in a thin disk, we compare Keplerian velocity fields to the measured two-dimensional velocity field measured and fit for a mass profile containing a black hole point mass plus a radially-varying spherical component, which suggests a lower limit for the black hole mass of 8.7 \pm 0.3 \times 10^8 M_{\sun}. Our measurements of the stellar velocity dispersion place this AGN within the scatter of the $M_{BH}$-$\sigma_{*}$ relation. As NGC 6240 is a merging system, this may indicate that the relation is preserved during a merger at least until the final coalescence of the two nuclei.Comment: 10 pages, 12 figures; accepted to Ap

Objective profiling of varied human motion based on normative assessment of magnetometer time series data

Objective: To quantify varied human motion and obtain an objective assessment of relative performance across a cohort. Approach: A wrist-worn magnetometer was used to record and quantify the complex motion patterns of 55 children aged 10-12 years old, generated during a fundamental movement skills programme. Sensor-based quantification of the physical activity used dynamic time warping of the magnetometer time series data for pairs of children. Pairwise comparison across the whole cohort produced a similarity matrix of all child to child correlations. Normative assessment scores were based on the Euclidean distance between n participants within an n-1 multi-variate space, created from multi-dimensional scaling of the similarity matrix. The sensor-based scores were compared to the current standardised assessment which involves binary scoring of technique, outcome and time components by trained assessors. Main Results: Visualisation of the relative performance using the first three axes of the multi-dimensional matrix, shows a 'performance sphere' in which children sit on concentric shells of increasing radius as performance deteriorates. Good agreement between standard and sensor scores is found, with Spearman rank correlation coefficients of the overall activity score in the range of 0.62-0.71 for different cohorts and a kappa statistic of 0.34 for categorisation of all 55 children into lower, middle, upper tertile and top 5% bands. Significance: By using multi-dimensional analysis of similarity measures between participants rather than direct parameterisation of the physiological data, complex and varied patterns of physical motion can be quantified, allowing objective and robust profiling of relative function across participant groups