Contribution of Trunk Rotation and Abdominal Muscles to Sprint Kayak Performance.

Over the past two decades the importance of trunk contribution to sporting performance has been highlighted through the expanse of literature concerning core stability and strength. However, the role of trunk motion and the abdominal muscles are yet to be established during sprint kayak performance. The purpose of this study was to determine the associations among trunk rotation, kayak velocity, and abdominal muscle activity during on-water sprint kayaking. Eight international paddlers completed five 150 m sprint trials. During each trial peak muscle activation (peak root-mean-squared electromyogram) of the latissimus dorsi, rectus abdominus, external obliques and rectus femoris for ipsilateral (stroke side) and contralateral (opposite side) were recorded as the paddler passed through a 5-m calibrated volume, in conjunction with upper and lower trunk rotation and kayak velocity. Results indicated a significant strong negative relationship between lower trunk rotation and peak velocity (r = -0.684, p < 0.05). Furthermore, a significant strong positive relationship (p < 0.05) with mean velocity was identified for the contralateral rectus abdominus and multiple significant associations between the rectus femoris, rectus abdominus and external obliques during the paddle stroke. Findings indicate that limiting the rotation of the lower trunk will increase both the peak and the mean velocity, with the rectus abdominus, external oblique and rectus femoris combining to assist in this process. Training should therefore focus on developing the strength of these muscle groups to enhance performance. [Abstract copyright: Copyright: © Academy of Physical Education in Katowice.

Prospectus, January 22, 1976

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Formation of hollow carbon nanoshells from thiol stabilised silver nanoparticles via heat treatment

Uniform, less 10 nm sized, hollow carbon nano-shells (HCNS) have been prepared via a single-step, thermal treatment of alkanethiol stabilised Ag nanoparticles (TS-AgNP). Direct evidence for the formation of spherical HCNS from TS-AgNP is provided by in situ MEMS heating on Si3N4 supports within a TEM, and ex situ thermal processing of TS-AgNP on carbon nanotube supports. A mechanism is proposed for the thermally driven, templated formation of HCNS from the TS-AgNP stabilising layer, with Ag catalysing the graphitisation of carbon in advance of thermally induced AgNP template removal. This facile processing route provides for excellent size control of the HCNS product via appropriate AgNP template selection. However, a rapid rate of heating was found to be crucial for the formation of well-defined HCNS, whilst a slow heating rate gave a much more disrupted product, comprising predominantly lacy carbon with decreased levels of graphitic ordering, reflecting a competition between the thermal transformation of the TS-layer and the rate of removal of the AgNP template

Tight Temporal Consistency of Coral Mass Spawning at the Flower Garden Banks, Gulf of Mexico, from 1997-2003

Mass spawning by the hard corals of the Flower Garden Banks National Marine Sanctuary has been studied for over a decade. In this report we present observations by a single set of experienced observers on spawning events extending over seven years, on spawning activity, lack of activity and coordination within and between species. This compilation shows that the spawning times of each species are extremely consistent during major events, with onset and hiatus often predictable to within seven minutes, and in some species to within two minutes. In addition to the extraordinary degree of temporal regulation, the other striking feature of the spawning schedule is the uniqueness of most spawning windows. With the exception of Diploria strigosa, each of the major spawning species—Colpophyllia natans, Montrastraea cavernosa, M. annularis, M. faveolata, M. franksi and Stephanocoenia intersepta—has a unique window of time in which it and no other coral species releases gametes. Spawning times for the 2005-2008 seasons are predicted based on these findings

Safety Sufficiency for NextGen: Assessment of Selected Existing Safety Methods, Tools, Processes, and Regulations

NextGen is a complex socio-technical system and, in many ways, it is expected to be more complex than the current system. It is vital to assess the safety impact of the NextGen elements (technologies, systems, and procedures) in a rigorous and systematic way and to ensure that they do not compromise safety. In this study, the NextGen elements in the form of Operational Improvements (OIs), Enablers, Research Activities, Development Activities, and Policy Issues were identified. The overall hazard situation in NextGen was outlined; a high-level hazard analysis was conducted with respect to multiple elements in a representative NextGen OI known as OI-0349 (Automation Support for Separation Management); and the hazards resulting from the highly dynamic complexity involved in an OI-0349 scenario were illustrated. A selected but representative set of the existing safety methods, tools, processes, and regulations was then reviewed and analyzed regarding whether they are sufficient to assess safety in the elements of that OI and ensure that safety will not be compromised and whether they might incur intolerably high costs

Invasion dynamics of Asian hornet, Vespa velutina (Hymenoptera: Vespidae) : a case study of a commune in south-west France

Asian hornet, Vespa velutina Lepeletier nests were discovered in 2007 in Andernos-les-Bains on the south-west coast of France, 3 years after the first reported sightings in France. The number of nests increased in the commune over the following 7 years, despite local authorities enacting a destruction policy. The nests existed in close proximity to one another leading to a high density of over 10 nests per square kilometre in urban areas. New information on the chosen habitat for nests is presented, and the differences between primary and secondary locations are evident, with primary nests mostly occupying buildings and man-made structures, while secondary nests were found on trees. Using Bayesian inference methods, we fit a basic model to the observational data, which allows us to estimate key demographic parameters. This model fit is highly informative for predicting V. velutina spread and colonisation of other at-risk regions, and suggests that local control has a limited impact on the spread of V. velutina once established within a region

Modelling of crack coalescence in 2024-T351 Al alloy friction stir welded joints

In the present work, FSW of 2024-T351 Al alloy is characterised in terms of weld residual stress and cyclic properties. A fatigue endurance of the FSW joint was also investigated and discussed. Critical areas for natural fatigue crack initiation in FSW are pinpointed. The fatigue mechanism in FSW is identified to follow a multiple crack coalescence nature. The numbers of cracks participate in coalescence and the resulting crack growth rate is governed by the distance between the crack tips from crack initiation to coalescence. The above represents a complex condition for modelling. During fatigue bending tests, surface crack initiation and growth were monitored by means of a plastic replication technique. Detailed analysis revealed that under that the FSW specimen failures in fatigue bending tests are mainly a process of crack growth with initiation from defects and oxide inclusions, causing subsurface crack formation. Multiple crack initiation sites were observed from different microstructural regimes in the non-uniform residual stress distribution across the weld. This indicates that failure is dominated by fatigue crack propagation from defects. Therefore mechanisms that include features such as defect size and residual stress were considered when applying crack growth analyses to lifetime predictions. Based on crack growth and characterisation of FSW joints, a modified version of the Hobson–Brown is adopted. The good correlation achieved between the experimental data and the model predictions is presented in this paper. Satisfactory predictions of FSW lifetimes are derived from the model

Population genetic isolation and limited connectivity in the purple finch (Haemorhous purpureus)

Sherpa Romeo green journal. Open access article. Creative Commons Attribution 3.0 Unported License (CC BY 3.0) appliesUsing a combination of mitochondrial and z- linked sequences, microsatellite data, and spatio- geographic modeling, we examined historical and contemporary factors influencing the population genetic structure of the purple finch (Haemorhous purpureus). Mitochondrial DNA data show the presence of two distinct groups corresponding to the two subspecies, H. p. purpureus and H. p. californicus. The two subspecies likely survived in separate refugia during the last glacial maximum, one on the Pacific Coast and one east of the Rocky Mountains, and now remain distinct lineages with little evidence of gene flow between them. Southwestern British Columbia is a notable exception, as subspecies mixing between central British Columbia and Vancouver Island populations suggests a possible contact zone in this region. Z- linked data support two mitochondrial groups; however, Coastal Oregon and central British Columbia sites show evidence of mixing. Contemporary population structure based on microsatellite data identified at least six genetic clusters: three H. p. purpureus clusters, two H. p. californicus clusters, and one mixed cluster, which likely resulted from high site fidelity and isolation by distance, combined with sexual selection on morphological characters reinforcing subspecies differences.Ye