Analysis of Selected Mechanics of the Backward C - Cut Ice Skating Stride

The purpose of the study was to evaluate the contributlon of structural and performance variables to the skating velocity of ice hockey players performing the backward C-cut ice skating technique. Ten skilled male ice hockey players volunteered to participate in this study. Each was filmed during a maximum effort backward skating task. An overhead view of each trial was recorded at 100 Hz using a Locam 16 mm camera. Data were collected from film using an Altek AC 30 digitizer and micro-computer system. Fourteen structural and kinematic dependent variables were measured. In addition three kinematic characteristics of the forward skating patterns of the same subject sample were also recorded. A Pearson product-moment correlation analysis was used to look at the relationships between skating velocity and each of the other dependent variables. Also, correlations between selected backward and forward characteristics were computed. The mean backward skating velocity of the sample was 6.56 m/s which resulted from a mean cycle length of 4.53 m and a mean cycle rate of 1.5 cycles per second. Only minor differences were found between right and left stride lengths and times so it was concluded that the movement pattern is symmetrical from side to side. Correlation analysis indicated that velocity is significantly related to both cycle width (r = .80) and cycle length (r = .84). Cycle time was also significantly related to veloclty (r = -.70). Not surprisingly cycle length and rate were significantly related in a negative direction (r - -.91). In an attempt to determine whether backward skating ability is a unique skill, backward velocity was correlated with forward velocity. The result revealed that those who skate fastest backward also tend to skate fastest forward (r ..81). The velocity of the backward trials was about 80 % of that of forward skating trials. Based on the results of the study, it was concluded that there is a strong relationship between selected descriptive aspects of the backward skating movement and the criteria skating veloclty. In addition, it was concluded that a strong relationship exists between backward and forward ice skating ability

An eddy-stimulated hotspot for fixed nitrogen-loss from the Peru oxygen minimum zone

Fixed nitrogen (N) loss to biogenic N2 in intense oceanic O2 minimum zones (OMZ) accounts for a large fraction of the global N sink and is an essential control on the ocean's N budget. However, major uncertainties exist regarding microbial pathways as well as net impact on the magnitude of N-loss and the ocean's overall N budget. Here we report the discovery of a N-loss hotspot in the Peru OMZ associated with a coastally trapped mesoscale eddy that is marked by an extreme N deficit matched by biogenic N2 production, high NO2− levels, and the highest isotope enrichments observed so far in OMZ's for the residual NO3−. High sea surface chlorophyll (SSC) in seaward flowing streamers provides evidence for offshore eddy transport of highly productive, inshore water. Resulting pulses in the downward flux of particles likely stimulated heterotrophic dissimilatory NO3− reduction and subsequent production of biogenic N2. The associated temporal/spatial heterogeneity of N-loss, mediated by a local succession of microbial processes, may explain inconsistencies observed among prior studies. Similar transient enhancements of N-loss likely occur within all other major OMZ's exerting a major influence on global ocean N and N isotope budgets

Household networks and emergent territory: a GIS study of Chumash households, villages and rock-art in South-Central California

Elite households of the Californian Chumash have been studied in order to understand the development of Late Holocene hunter-gatherer alliance networks. Equally, models of what has been termed ‘tribelet territories’ have been used to describe land ownership within larger Californian concepts. Surprisingly little research has explicitly addressed issues of how such territories may have developed. In this article, we turn to DeLanda’s philosophy of social complexity to consider how Chumash households may have underpinned the development of tribelet territories and the political implications for their articulation with wider alliances. Importantly, utilizing Geographic Information Systems (GIS), we analyse potential mobility patterns in relation to households, villages and rock-art locales in a case from the Emigdiano Chumash. The results suggest that the painting of rock art was imbricated within processes of territorialization, and that the local placement of art reflects which villages were home to particularly high-status households

Investigating trophic ecology and dietary niche overlap among morphs of Lake Trout in Lake Superior

Four morphs of Lake Trout (Salvelinus namaycush, Walbaum 1792) have been identified in Lake Superior: leans, siscowets, humpers, and redfins. In this comprehensive study, the trophic ecology of Lake Trout morphs were characterized using stomach content, fatty acid, and stable isotope data. Stomach content results indicated a predominately piscivorous diet for leans, siscowets, and redfins, whereas humper diets were comprised of 50% fish and 50% Mysis by mass. Humper and siscowets were most similar in their dietary fatty acid profiles, whereas redfins had the most distinct dietary fatty acid profile. Results from stable isotope analysis revealed some among-morph differences along a pelagic-profundal consumption gradient (34S), but there were no significant differences in trophic position (15N) or basal carbon sources among morphs (13C). Using the recently developed nicheROVER software package, 4-dimensional trophic niches for each morph were quantified using stable isotope ratios (δ13C, δ15N, and δ34S) and fatty acid profiles (30 dietary fatty acids, condensed to one axis). Humpers had the largest 4-dimensional niche regions of all four morphs, and redfins had the smallest. Pairwise probability of overlap among morphs in these four-dimensional niche regions was determined to be < 50% in most cases. Overall, stomach content results indicate that humpers diets were more planktivorous than the other morphs, consistent with previous research. Results of the niche overlap analysis suggests some degree of generalist feeding for all morphs. Better characterization of seasonal variation in diet using tracers that reflect more recent feeding (e.g., fatty acids, stomach contents, and/or stable isotope analyses performed on tissues that turnover more quickly than muscle) are needed to further elucidate among-morph differences and similarities in diet and trophic ecology