Acute Effects Of The Mid-thigh Power Clean On The Advanced Tennis Serve

Post-activation potentiation (PAP) is a phenomenon in which athletic performance is acutely enhanced after a muscle contraction (evoked or voluntary). Most studies have examined isometric maximal voluntary contraction and heavy resistance exercise as PAP inducing protocols, but minimal research exists analyzing Olympic lifting exercises. The purpose of this study was to investigate the acute PAP response of mid-thigh power clean on the tennis serve among NCAA Division I male tennis players. Tennis players (n=6) who were current roster members performed 5 tennis serves before and 4 min after one set of 5 repetitions of the mid-thigh power clean exercise at 60% 1RM. Performance was evaluated by measuring (pre and post) peak velocity [F (1, 57)=1.456, p=.232], peak power [F (1, 57)= 0.799, p=.375], total power output [F (1, 57) = 0.748, p=.391], impulse [F (1, 58) = 3.163, p=.081], and rate of force development [F (1, 58) = 0.531, p=.469]. There were no significant differences in any of the outcomes indicating there was no evidence of a PAP. Further research is needed to study the possible applicability of Olympic lifting to induce PAP effects on tennis players. It appears that the effective application of PAP inducing exercises appears to be highly individualized. Thus, the use of PAP complexes in tennis athletes should consider both the absolute and relative strength of each athlete in conjunction with the length of the rest period when attempting to optimize the PAP response using an Olympic lifting exercise

Absorption in quantum electrodynamics cavities in terms of a quantum jump operator

We describe the absorption by the walls of a quantum electrodynamics cavity as a process during which the elementary excitations (photons) of an internal mode of the cavity exit by tunneling through the cavity walls. We estimate by classical methods the survival time of a photon inside the cavity and the quality factor of its mirrors

IRIS Observations of Spicules and Structures Near the Solar Limb

We have analyzed IRIS spectral and slit-jaw observations of a quiet region near the South Pole. In this article we present an overview of the observations, the corrections, and the absolute calibration of the intensity. We focus on the average profiles of strong (Mg ii h and k, C ii and Si iv), as well as of weak spectral lines in the near ultraviolet (NUV) and the far ultraviolet (FUV), including the Mg ii triplet, thus probing the solar atmosphere from the low chromosphere to the transition region. We give the radial variation of bulk spectral parameters as well as line ratios and turbulent velocities. We present measurements of the formation height in lines and in the NUV continuum, from which we find a linear relationship between the position of the limb and the intensity scale height. We also find that low forming lines, such as the Mg ii triplet, show no temporal variations above the limb associated with spicules, suggesting that such lines are formed in a homogeneous atmospheric layer and, possibly, that spicules are formed above the height of 2 arc sec. We discuss the spatio-temporal structure near the limb from images of intensity as a function of position and time. In these images, we identify p-mode oscillations in the cores of lines formed at low heights above the photosphere, slow moving bright features in O i and fast moving bright features in C ii. Finally, we compare the Mg ii k and h line profiles, together with intensity values of the Balmer lines from the literature, with computations from the PROM57Mg non-LTE model developed at the Institut d'Astrophysique Spatiale and estimated values of the physical parameters. We obtain electron temperatures in the range of $\sim8000$ K at small heights to $\sim20000$ K at large heights, electron densities from $1.1 \times 10^{11}$ to $4 \times 10^{10}$ cm$^{-3}$ and a turbulent velocity of $\sim24$km/s.Comment: Accepted for publication in Solar Physic

Optical determination and identification of organic shells around nanoparticles: application to silver nanoparticles

We present a simple method to prove the presence of an organic shell around silver nanoparticles. This method is based on the comparison between optical extinction measurements of isolated nanoparticles and Mie calculations predicting the expected wavelength of the Localized Surface Plasmon Resonance of the nanoparticles with and without the presence of an organic layer. This method was applied to silver nanoparticles which seemed to be well protected from oxidation. Further experimental characterization via Surface Enhanced Raman Spectroscopy (SERS) measurements allowed to identify this protective shell as ethylene glycol. Combining LSPR and SERS measurements could thus give proof of both presence and identification for other plasmonic nanoparticles surrounded by organic shells

Nonlinear viscous damping and tuned mass damper design for occupant comfort in flexible tall buildings subjected to wind loading

During wind events, tall buildings may exhibit floor accelerations levels that compromise occupant comfort. The use of energy dissipating devices to reduce peak floor accelerations is a sound strategy to improve building performance. The estimation of mean peak floor accelerations of a steel-frame building subjected to random wind forces and the design procedure of supplemental nonlinear viscous dampers to improve occupant comfort in one-year recurrence wind events are described in this paper. A stochastic wind load model is developed to estimate acceleration performance; drag, lift and torsional moments at each story are defined as random stationary processes by the definition of their cross-spectral density matrix. Wind tunnel results and computational fluid dynamic analyses are used to fine-tune the stochastic load models. Reduced-order structural models of the tower are developed to estimate the frequency response function from floor loadings to floor accelerations at corners points of the buildings. Statistical linearization is used to estimate the performance of the buildings with non-linear viscous dampers installed in different configurations. Floor acceleration reductions achieved with supplemental viscous dampers and a tuned mass damper are evaluated to comply with occupant performance standards.Publicado en: Mecánica Computacional vol. XXXV, no. 12Facultad de Ingenierí

Nonlinear viscous damping and tuned mass damper design for occupant comfort in flexible tall buildings subjected to wind loading

During wind events, tall buildings may exhibit floor accelerations levels that compromise occupant comfort. The use of energy dissipating devices to reduce peak floor accelerations is a sound strategy to improve building performance. The estimation of mean peak floor accelerations of a steel-frame building subjected to random wind forces and the design procedure of supplemental nonlinear viscous dampers to improve occupant comfort in one-year recurrence wind events are described in this paper. A stochastic wind load model is developed to estimate acceleration performance; drag, lift and torsional moments at each story are defined as random stationary processes by the definition of their cross-spectral density matrix. Wind tunnel results and computational fluid dynamic analyses are used to fine-tune the stochastic load models. Reduced-order structural models of the tower are developed to estimate the frequency response function from floor loadings to floor accelerations at corners points of the buildings. Statistical linearization is used to estimate the performance of the buildings with non-linear viscous dampers installed in different configurations. Floor acceleration reductions achieved with supplemental viscous dampers and a tuned mass damper are evaluated to comply with occupant performance standards.Publicado en: Mecánica Computacional vol. XXXV, no. 12Facultad de Ingenierí

Spatial multi-criteria decision analysis to predict suitability for African swine fever endemicity in Africa

Background African swine fever (ASF) is endemic in several countries of Africa and may pose a risk to all pig producing areas on the continent. Official ASF reporting is often rare and there remains limited awareness of the continent-wide distribution of the disease. In the absence of accurate ASF outbreak data and few quantitative studies on the epidemiology of the disease in Africa, we used spatial multi-criteria decision analysis (MCDA) to derive predictions of the continental distribution of suitability for ASF persistence in domestic pig populations as part of sylvatic or domestic transmission cycles. In order to incorporate the uncertainty in the relative importance of different criteria in defining suitability, we modelled decisions within the MCDA framework using a stochastic approach. The predictive performance of suitability estimates was assessed via a partial ROC analysis using ASF outbreak data reported to the OIE since 2005. Results Outputs from the spatial MCDA indicate that large areas of sub-Saharan Africa may be suitable for ASF persistence as part of either domestic or sylvatic transmission cycles. Areas with high suitability for pig to pig transmission (‘domestic cycles’) were estimated to occur throughout sub-Saharan Africa, whilst areas with high suitability for introduction from wildlife reservoirs (‘sylvatic cycles’) were found predominantly in East, Central and Southern Africa. Based on average AUC ratios from the partial ROC analysis, the predictive ability of suitability estimates for domestic cycles alone was considerably higher than suitability estimates for sylvatic cycles alone, or domestic and sylvatic cycles in combination. Conclusions This study provides the first standardised estimates of the distribution of suitability for ASF transmission associated with domestic and sylvatic cycles in Africa. We provide further evidence for the utility of knowledge-driven risk mapping in animal health, particularly in data-sparse environments.</p

On the Effect of Adjacent Sector Multiple Access Interference on Space Time Spreading Systems

Space Time Spreading systems are proposed as a method to enhance communications between the Base Station (BS) and Mobile Station (MS) by using multiple transmit antennas at the Base Station. This provides a form of transmit diversity when there are more than one transmitting antennas. Space Time Spreading systems have been shown to be efficient in their use of the limited number of orthogonal spreading sequences and to provide a diversity gain, which in the case of two transmitter antennas at the BS and one receiving antenna at the MS, is of order two. The paper looks at the effect of unsynchronized adjacent cell interference caused by scatterers causing the target MS to experience Multiple Access Interference (MAI) due to misaligned orthogonal codes from adjacent sectors in a sectorised cell (with 120 degree sectorisation). The study finds that adjacent MAI does adversely influence the Bit Error Rate (BER) of the target MS