Quantifying the onset of the concentric phase of the force–time record during jumping

Thirteen college students performed a drop jump from height equal to their peak vertical jump, single leg jumps from the left and right legs, and a counter movement jump. Vertical ground reaction force (GRF) obtained via an AMTI force plate and video analysis of markers placed on the hip, knee, lateral malleolus, and fifth metatarsal were used to estimate reaction forces on the knee joint. One-way Repeated Measures ANOVA indicated no differences for knee joint reaction forces relative to body weight or peak GRF for any of the jumps (p \u3e 0.05). Average measures Intraclass Correlation Coefficients ranged from r = 0.90 to 0.97. Results indicate that peak GRF and knee joint reaction forces during the drop jump, counter movement jump, and single leg left and right leg jumps are reliable measures

THE EFFECTS OF A CLOTH WRAP IN STABILIZATION OF THE ANKLE

This study aimed to examine the effects of the cloth wrap in ankle stabilization, since there is limited research of cloth wrap ankle stabilization. Twenty subjects (13 female, 7 male) were utilized in this study. Three conditions were performed on each ankle ( Baseline, Wrapped, and Unwrapped). Results showed the only significant difference (p smaller than 0.01) found were the main effects for condition (Baseline vs. Wrapped, vs. Unwrapped). A significant interaction of condition by gender was also found (p=0.034). None of the other interactions were significant (p>0.05). It was concluded that the cloth wrap may have decreased the subject's proprioception. Females also stabilized out faster than males, possibly due to a lower center of gravity (COG)

Relaxation kinetics in two-dimensional structures

We have studied the approach to equilibrium of islands and pores in two dimensions. The two-regime scenario observed when islands evolve according to a set of particular rules, namely relaxation by steps at low temperature and smooth at high temperature, is generalized to a wide class of kinetic models and the two kinds of structures. Scaling laws for equilibration times are analytically derived and confirmed by kinetic Monte Carlo simulations.Comment: 6 pages, 7 figures, 1 tabl

Differential systems associated with tableaux over Lie algebras

We give an account of the construction of exterior differential systems based on the notion of tableaux over Lie algebras as developed in [Comm. Anal. Geom 14 (2006), 475-496; math.DG/0412169]. The definition of a tableau over a Lie algebra is revisited and extended in the light of the formalism of the Spencer cohomology; the question of involutiveness for the associated systems and their prolongations is addressed; examples are discussed.Comment: 16 pages; to appear in: "Symmetries and Overdetermined Systems of Partial Differential Equations" (M. Eastwood and W. Miller, Jr., eds.), IMA Volumes in Mathematics and Its Applications, Springer-Verlag, New Yor

Stability of mode-locked kinks in the ac driven and damped sine-Gordon lattice

Kink dynamics in the underdamped and strongly discrete sine-Gordon lattice that is driven by the oscillating force is studied. The investigation is focused mostly on the properties of the mode-locked states in the {\it overband} case, when the driving frequency lies above the linear band. With the help of Floquet theory it is demonstrated that the destabilizing of the mode-locked state happens either through the Hopf bifurcation or through the tangential bifurcation. It is also observed that in the overband case the standing mode-locked kink state maintains its stability for the bias amplitudes that are by the order of magnitude larger than the amplitudes in the low-frequency case.Comment: To appear in Springer Series on Wave Phenomena, special volume devoted to the LENCOS'12 conference; 6 figure

Experimental analysis and model validation of an opaque ventilated facade

Natural ventilation is a convenient way of reducing energy consumption in buildings. In this study an experimental module of an opaque ventilated façade (OVF) was built and tested for assessing its potential of supplying free ventilation and air preheating for the building. A numerical model was created and validated against the experimental data. The experimental results showed that the flow rates induced in the façade cavity were due to mixed driving forces: wind and buoyancy. Depending on the weather conditions one of them was the main driving force, or both were of the same order. When the wind force was the main driving force, higher flow rates were found. In these cases buoyancy acted as supporting driving force. When the wind speed was low and buoyancy prevailed lower flow rates were found. Air and surface temperatures were predicted by the numerical model with a better accuracy than flow and energy rates. The model predicts correctly the influence of the wind and buoyancy driving forces. The experimental OVF module showed potential for free ventilation and air preheating, although it depends on weather and geometrical variables. The use of the numerical model using the right parameters was found viable for analyzing the performance of an OVF

Mindful Parenting, Parenting Cognitions, and Parent-Youth Communication: Bidirectional Linkages and Mediational Processes

Objectives: Mindful parenting and parenting cognitions likely have important linkages to each other and to parent-child communication, but these linkages have not been tested. In this article, we test the bidirectional linkages between mindful parenting and parenting cognitions (sense of competence, parent-centered attributions) and the underlying mediational processes that link them to parent-child communication (parental solicitation and youth disclosure). Methods: Longitudinal, autoregressive cross-lagged models were run within a longitudinal sample of rural and suburban early adolescents and their mothers (n = 421; mean adolescent age = 12.14, 46% male, 73% white). Results: Significant bidirectional linkages were found between mindful parenting and parenting cognitions across Time 1 and Time 2. Greater mindful parenting at Time 1 was associated with more positive parenting cognitions (e.g., greater perceptions of parental competence and fewer negative parent-centered attributions or self-blame) at Time 2. More positive parenting cognitions at Time 1 were also associated with greater levels of mindful parenting at Time 2. Mindful parenting at Time 2 mediated the association between parenting cognitions (both parent-centered attributions and sense of competence) at Time 1 and parental solicitation at Time 3. Conclusions: Mindful parenting and parenting cognitions influence each other over time. Parenting cognitions can affect parental solicitation via increases in mindful parenting. The discussion focuses on potential underlying processes

Partially ordered models

We provide a formal definition and study the basic properties of partially ordered chains (POC). These systems were proposed to model textures in image processing and to represent independence relations between random variables in statistics (in the later case they are known as Bayesian networks). Our chains are a generalization of probabilistic cellular automata (PCA) and their theory has features intermediate between that of discrete-time processes and the theory of statistical mechanical lattice fields. Its proper definition is based on the notion of partially ordered specification (POS), in close analogy to the theory of Gibbs measure. This paper contains two types of results. First, we present the basic elements of the general theory of POCs: basic geometrical issues, definition in terms of conditional probability kernels, extremal decomposition, extremality and triviality, reconstruction starting from single-site kernels, relations between POM and Gibbs fields. Second, we prove three uniqueness criteria that correspond to the criteria known as bounded uniformity, Dobrushin and disagreement percolation in the theory of Gibbs measures.Comment: 54 pages, 11 figures, 6 simulations. Submited to Journal of Stat. Phy