Effects of prophylactic knee bracing on patellar tendon loading parameters during functional sports tasks in recreational athletes

Purpose This study investigated the efects of prophylactic knee bracing on patellar tendon loading parameters. Methods Twenty recreational athletes (10 male and 10 female) from diferent athletic disciplines performed run, cut and single leg hop movements under two conditions (prophylactic knee brace/no-brace). Lower extremity kinetics and kinematics were examined using a piezoelectric force plate and three-dimensional motion capture system. Patellar tendon loading was explored using a mathematical modelling approach, which accounted for co-contraction of the knee lexors. Tendon loading parameters were examined using 2 (brace) × 3 (movement) × 2 (sex) mixed ANOVAs. Results Tendon instantaneous load rate was signiicantly reduced in female athletes in the run (brace 289.14 BW/s no-brace 370.06 BW/s) and cut (brace 353.17 BW/s/no-brace 422.01 BW/s) conditions whilst wearing the brace. Conclusions Female athletes may be able to attenuate their risk from patellar tendinopathy during athletic movements, through utilization of knee bracing, although further prospective research into the prophylactic efects of knee bracing is required before this can be clinically substantiated

Characterization of synthetic jet resonant cavities

The scientific and technical literature about synthetic jet actuators includes a very wide field of applications such as flow control, heat transfer from limited-size surfaces, general enhancement of mixing between fluid currents, generation of micro-thrust for propulsion or attitude control. The overall design of the actuators needs practical modeling tools. The present work is aimed at characterizing the frequency response of a resonant cavity based synthetic jet actuator driven by a thin piezoelectric disk and represents an alternative contribution to the Persoons’s work [1]; in particular, it approaches the frequency response analysis from the same perspective of Sharma [2], who proposed a frequency-response model directly based on fluid dynamics equations, whereas Persoons [1] follows more directly the Gallas et al. [3] perspective based on the equivalent electric circuit approach. A lumped element mathematical model [4] of the operation of a synthetic jet actuator is both analytically and numerically investigated in order to obtain information about the frequency response of the device; the oscillating membrane is considered as a single-degree-of-freedom mechanical system, while the resonant cavity and orifice components are described by means of proper forms of the continuity and Bernoulli’s unsteady equations. The non-linear governing equations system has been numerically integrated in MATLAB environment. From the analytical viewpoint, it is found that the device behaves as a two-coupled oscillators system and, by solving the relevant eigenvalues problem, simply analytical formulas are given in order to predict the two modified peak frequencies, as functions of the uncoupled first-mode structural and Helmholtz resonance frequencies. The model is also validated through systematic experimental tests carried out on three devices having different mechanical and geometrical characteristics leading to an increasing coupling factor; it is found a very strict agreement between exit flow velocity measurements and numerical simulations for any tested device, for different supply voltages; moreover, the analytical formulas yield predictions in close agreement with numerical and experimental findings as well. References [1] Persoons, T., “General Reduced Order Model to Design and Operate Synthetic Jet Actuators", AIAA Journal, Vol. 50, No. 4, 2012, pp. 916-927. [2] Sharma, R. N., “Fluid Dynamics Based Analytical Model for Synthetic Jet Actuators,” AIAA Journal, Vol. 45, No. 8, Aug. 2007, pp. 1841-1847. [3] Gallas, Q., Holman, R., Nishida, T., Carroll, B., Sheplak, M., and Cattafesta, L., “Lumped Element Modeling of Piezoelectric-Driven Synthetic Jet Actuators,” AIAA Journal., Vol. 41, No. 2, 2003, pp. 240-247. [4] de Luca, L., Girfoglio, M., and Coppola, G., “Modeling and Experimental Validation of the Frequency Response of Synthetic Jet Actuators,” under revision for AIAA Journal, 2013

A Gr receptor is required for response to the sugar trehalose in taste neurons of Drosophila

We recently identified from the Drosophila genome database a large family of G protein-coupled receptor genes, the Gr genes, and predicted that they encode taste receptors on the basis of their structure and specificity of expression. The expression of Gr genes in gustatory neurons has subsequently been confirmed and 56 family members have been reported. Here we provide functional evidence that one Gr gene, Gr5a, encodes a taste receptor required for response to the sugar trehalose. In two different mutants that carry deletions in Gr5a, electrophysiological and behavioral responses to trehalose were diminished but the response to sucrose was unaffected. Transgenic rescue experiments showed that Gr5a confers response to trehalose. The results correlate a particular taste ligand with a Gr receptor and indicate a role for G protein-mediated signaling in the transduction of sweet taste in Drosophila