Strength, jumping, and change of direction speed asymmetries are not associated with athletic performance in elite academy soccer players

The aims of the present study were twofold: 1) to measure inter-limb asymmetries from a battery of fitness tests in youth soccer players and, 2) determine the association between asymmetry and measures of athletic performance. Sixteen elite youth soccer players (14.7 ± 0.2 years) performed a single leg Abalakov test (ABK), change of direction (COD) test over 10 m (5 + 5) and 20 m (10 + 10), and an iso-inertial power test. Subjects also performed 10 m, 20 m and 30 m sprints and a bilateral countermovement jump (CMJ), which were correlated with all ABK, COD and iso-inertial asymmetry scores. A one-way repeated measures ANOVA showed significant differences between inter-limb asymmetry scores across multiple tests (p 0.05) between the different inter-limb asymmetry scores, and between asymmetry scores and athletic performance. These findings show the test-specific nature of asymmetries in youth soccer players, with the iso-inertial power test being the most sensitive in detecting asymmetry. Moreover, the results obtained suggest that inherent asymmetry in young soccer players did not negatively impact their performance

The Shocks To Crude Oil Production. Nonparametric Stationarity Analysis For 20 OPEC And Non-OPEC Countries

The stochastic properties of crude oil production have been examined in the literature from different perspectives, with partly non-coincident conclusions depending on model specification. In this paper the nature of the shocks affecting crude oil production is analyzed for a panel of 20 OPEC and non-OPEC countries with reference to the period from January 1973 to December 2015. We rely on a novel nonparametric panel stationarity testing approach which offers the advantage of not requiring model specification of the trend functions for the series in the panel. Our analysis detects strong evidence of non-stationarity, both globally and group-wise for the OPEC and non-OPEC countries. A case-by-case study reveals that stationarity is rejected for 8 out of the countries under study (namely, Algeria, Canada, China, Iran, Mexico, Nigeria, Qatar, and the US) for which shocks would thus have permanent effects, with stationarity being relatively more frequent among OPEC members

The Shocks To Crude Oil Production. Nonparametric Stationarity Analysis For 20 OPEC And Non-OPEC Countries

The stochastic properties of crude oil production have been examined in the literature from different perspectives, with partly non-coincident conclusions depending on model specification. In this paper the nature of the shocks affecting crude oil production is analyzed for a panel of 20 OPEC and non-OPEC countries with reference to the period from January 1973 to December 2015. We rely on a novel nonparametric panel stationarity testing approach which offers the advantage of not requiring model specification of the trend functions for the series in the panel. Our analysis detects strong evidence of non-stationarity, both globally and group-wise for the OPEC and non-OPEC countries. A case-by-case study reveals that stationarity is rejected for 8 out of the countries under study (namely, Algeria, Canada, China, Iran, Mexico, Nigeria, Qatar, and the US) for which shocks would thus have permanent effects, with stationarity being relatively more frequent among OPEC members

Effects of livestock pressure and vegetation cover on the spatial and temporal structure of soil microarthropod communities in Iberian rangelands

Forests, including their soils, play an important role since they represent a large reservoir of biodiversity. Current studies show that the diversity of soil fauna provides multiple ecosystem functions and services across biomes. However, anthropogenic practices often pose a threat to soil fauna because of changes in land use and soil mismanagement. In these terms, rangelands in the southwest of Spain present several problems of soil degradation related to livestock activity and soil erosion, the intensity of which compromises the soil fauna's functions in the ecosystem. Therefore, the aim of this study is to evaluate the response of community metrics and the spatial distribution of soil microarthropods to livestock activity and vegetation in such ecosystems. A photo interpretation analysis of an experimental catchment used as a study area was developed to identify and classify the intensity of livestock pressure. A total of 150 soil samples were collected throughout 2018. Soil biological (CO2 efflux) and physical-chemical parameters (pH, bulk density, organic matter, and water contents), and such meteorological variables as precipitation, temperature, and evapotranspiration were considered as variables affecting the composition of microarthropod communities in terms of taxa diversity, abundances, and their adaptation to soil environment (evaluated by QBS-ar index). Results showed higher abundance of microarthropods and higher adaptation to soil environment outside the influence of trees rather than beneath tree canopies. Moreover, the classification of livestock pressure revealed by the photo interpretation analysis showed low correlations with community structure, as well as with the occurrence of well-adapted microarthropod groups that were found less frequently in areas with evidence of intense livestock activity. Furthermore, abundances and adaptations followed different spatial patterns. Due to future climate changes and increasing anthropogenic pressure, it is necessary to continue the study of soil fauna communities to determine their degree of sensitivity to such changes

Hybrid photonic crystal lasers

Energy efficient Wavelength Division Multiplexing (WDM) is the key to satisfying the future bandwidth requirements of datacentres. As the silicon photonics platform is regarded the only technology able to meet the required power and cost efficiency levels, the development of silicon photonics compatible narrow linewidth lasers is now crucial. We discuss the requirements for such laser systems and report the experimental demonstration of a compact uncooled external-cavity mW-class laser architecture with a tunable Si Photonic Crystal resonant reflector, suitable for direct Frequency Modulation.Postprin