THE 3-D KINEMATIC ANALYSIS OF DIFFERENT TENNIS SERVE

The key to success for a good tennis player is to be able to take the advantages of serving and keep the serve. The world's professional tennis players in front of the world rankings, most have very excellent serve skills. Two different footwork techniques in tennis serve used by most professional tennis players are the foot-up and foot-back serve technique. Most researchers investigated the differences between these footwork techniques using 2-D kinematics data (Elliott et al, 1983). However, little evidence has demonstrated that which serve technique is better (Bylak et al, 1998) or if a difference exists between foot-up and foot-back technique using 3-D analysis (Elliott et al, 1996). The purposes of this study were to investgate the differences in 3-D kinematics between the foot-up and foot-back tennis serve techniques

EFFECTS OF STEP LENGTH ON THE BIOMECHANICS OF LOWER LIMBS DURING ELLIPTICAL EXERCISE

Elliptical exercise (EE) has been developed as a low-impact aerobic exercise modality with increased popularity in fitness training and clinical applications over the last decade. During EE, the feet are constrained by pedals to follow an elliptical trajectory, with the possibility of producing disadvantageous joint loads and potential musculoskeletal overuse injuries (Lu et al., 2007). Therefore, proper selection of step length during EE may be helpful for the reduction of these disadvantageous joint loads. The purpose of the study was to study the effects of three different step lengths on biomechanics of the lower limbs during EE

Divergence and Shannon information in genomes

Shannon information (SI) and its special case, divergence, are defined for a DNA sequence in terms of probabilities of chemical words in the sequence and are computed for a set of complete genomes highly diverse in length and composition. We find the following: SI (but not divergence) is inversely proportional to sequence length for a random sequence but is length-independent for genomes; the genomic SI is always greater and, for shorter words and longer sequences, hundreds to thousands times greater than the SI in a random sequence whose length and composition match those of the genome; genomic SIs appear to have word-length dependent universal values. The universality is inferred to be an evolution footprint of a universal mode for genome growth.Comment: 4 pages, 3 tables, 2 figure

STEP HEIGHT EFFECTS ON LOWER LIMB BIOMECHANICS AND BODY CENTRE OF MASS MOTION DURING ELLIPTICAL EXERCISE

Elliptical exercise (EE) has been shown to be beneficial for the development and maintenance of cardiorespiratory fitness. Despite these benefits, the feet are constrained by pedals to follow an elliptical trajectory, with the possibility of producing disadvantageous joint loads, body instability and potential musculoskeletal overuse injuries (Lu et al., 2007). Proper selection of step height during EE may help reduce these disadvantageous joint loads and instability. The purpose of the study was to study the effects of step height on the lower limb biomechanics and associated body center of mass (COM) motion during EE

An Econometric Analysis of ETF and ETF Futures in Financial and Energy Markets Using Generated Regressors

It is well known that that there is an intrinsic link between the financial and energy sectors, which can be analyzed through their spillover effects, which are measures of how the shocks to returns in different assets affect each other’s subsequent volatility in both spot and futures markets. Financial derivatives, which are not only highly representative of the underlying indices but can also be traded on both the spot and futures markets, include Exchange Traded Funds (ETFs), which is a tradable spot index whose aim is to replicate the return of an underlying benchmark index. When ETF futures are not available to examine spillover effects, “generated regressors” may be used to construct both Financial ETF futures and Energy ETF futures. The purpose of the paper is to investigate the co-volatility spillovers within and across the US energy and financial sectors in both spot and futures markets, by using “generated regressors” and a multivariate conditional volatility model, namely Diagonal BEKK. The daily data used are from 1998/12/23 to 2016/4/22. The data set is analyzed in its entirety, and also subdivided into three subset time periods. The empirical results show there is a significant relationship between the Financial ETF and Energy ETF in the spot and futures markets. Therefore, financial and energy ETFs are suitable for constructing a financial portfolio from an optimal risk management perspective, and also for dynamic hedging purposes

Association of Secondhand Smoke Exposure with Pediatric Invasive Bacterial Disease and Bacterial Carriage: A Systematic Review and Meta-analysis

Background: A number of epidemiologic studies have observed an association between secondhand smoke (SHS) exposure and pediatric invasive bacterial disease (IBD) but the evidence has not been systematically reviewed. We carried out a systematic review and meta-analysis of SHS exposure and two outcomes, IBD and pharyngeal carriage of bacteria, for Neisseria meningitidis (N. meningitidis), Haemophilus influenzae type B (Hib), and Streptococcus pneumoniae (S. pneumoniae). Methods and Findings: Two independent reviewers searched Medline, EMBASE, and selected other databases, and screened articles for inclusion and exclusion criteria. We identified 30 case-control studies on SHS and IBD, and 12 crosssectional studies on SHS and bacterial carriage. Weighted summary odd ratios (ORs) were calculated for each outcome and for studies with specific design and quality characteristics. Tests for heterogeneity and publication bias were performed. Compared with those unexposed to SHS, summary OR for SHS exposure was 2.02 (95% confidence interval [CI] 1.52–2.69) for invasive meningococcal disease, 1.21 (95% CI 0.69–2.14) for invasive pneumococcal disease, and 1.22 (95% CI 0.93–1.62) for invasive Hib disease. For pharyngeal carriage, summary OR was 1.68 (95% CI, 1.19–2.36) for N. meningitidis, 1.66 (95% CI 1.33–2.07) for S. pneumoniae, and 0.96 (95% CI 0.48–1.95) for Hib. The association between SHS exposure and invasive meningococcal and Hib diseases was consistent regardless of outcome definitions, age groups, study designs, and publication year. The effect estimates were larger in studies among children younger than 6 years of age for all three IBDs, and in studies with the more rigorous laboratory-confirmed diagnosis for invasive meningococcal disease (summary OR 3.24; 95% CI 1.72–6.13). Conclusions: When considered together with evidence from direct smoking and biological mechanisms, our systematic review and meta-analysis indicates that SHS exposure may be associated with invasive meningococcal disease. The epidemiologic evidence is currently insufficient to show an association between SHS and invasive Hib disease or pneumococcal disease. Because the burden of IBD is highest in developing countries where SHS is increasing, there is a need for high-quality studies to confirm these results, and for interventions to reduce exposure of children to SHS