Buceando en la táctica como componente de la lógica interna de la natación. Mirada desde la Praxiología Motriz

¿Existe táctica en un deporte comotriz y psicomotriz como es la natación? La presente ponencia tiene como propósito hacer un aporte y divulgar algunas reflexiones que permitirán pensar, analizar y caracterizar a la natación desde la perspectiva de la Praxiología Motriz. Pensando a la natación como deporte, y en este sentido, podemos decir que "es una actividad competitiva, (...) individual, (...) reglada e institucionalizada" (Parlebas,1993) y que por ello, puede ser analizada como una práctica psicomotriz. Además, la natación posee la particularidad de que en su realización no se llevan a cabo interacciones motrices esenciales con otros, es decir, que integra un grupo de actividades motrices realizadas en solitario. Por lo tanto, un recorrido teórico por conceptos praxiológicos como la "comotricidad", la psicotricidad y la "lógica interna", (profundizando en la táctica), permiten diferenciar la natación, en sus diferentes manifestaciones (aguas abiertas, diferentes pruebas en pileta corta) con otros deportes, otorgándole una identidad propia, única, que la diferencia de los demás. Desde esta perspectiva, además de poder acercarme a las múltiples respuestas posibles de esa inquietud inicial, pretendo realizar un aporte en la acumulación de conocimiento específico de una temática que ha sido poco trabajada, y contribuir a la circulación de bibliografía -hasta ahora escasa-, brindándome la posibilidad de revisar y modificar mis prácticas permanentemente. Además estas consideraciones me permitirán realizar avances para laborar mi Tesis de Maestría en Deportes de la Universidad de La Plata

Impacts of passive warming chambers on soil parameters in Antarctica

Passive chambers are used to examine the impacts of summer warming in Antarctica but, so far, impacts occurring outside the growing season, or related to extreme temperatures, have not been reported, despite their potentially large biological significance. In this review, we synthesise and discuss the microclimate impacts of passive warming chambers (closed, ventilated and Open Top Chamber-OTC) commonly used in Antarctic terrestrial habitats, paying special attention to seasonal warming, during the growing season and outside, extreme temperatures and freeze-thaw events. Both temperature increases and decreases were recorded throughout the year. Closed chambers caused earlier spring soil thaw (8-28 days) while OTCs delayed soil thaw (3-13 days). Smaller closed chamber types recorded the largest temperature extremes (up to 20°C higher than ambient) and longest periods (up to 11 h) of above ambient extreme temperatures, and even OTCs had above ambient temperature extremes over up to 5 consecutive hours. The frequency of freeze-thaw events was reduced by ~25%. All chamber types experienced extreme temperature ranges that could negatively affect biological responses, while warming during winter could result in depletion of limited metabolic resources. The effects outside the growing season could be as important in driving biological responses as the mean summer warming. We make suggestions for improving season-specific warming simulations and propose that seasonal and changed temperature patterns achieved under climate manipulations should be recognised explicitly in descriptions of treatment effects.

Annual average Sr/Ca measurements from Porites lutea coral at Ha'afera Island, Tonga

In the South Pacific Convergence Zone (SPCZ), the variability in a sub-seasonally resolved microatoll Porites colony Sr/Ca record from Tonga and a previously published high-resolution record from Fiji are strongly influenced by sea surface temperature (SST) over the calibration period from 1981 to 2004 (R^2 = 0.67 - 0.68). However, the Sr/Ca-derived SST correlation to instrumental SST decreases back in time. The lower frequency secular trend (~1°C) and decadal-scale (~2 - 3°C) modes in Sr/Ca-derived SST are almost two times larger than that observed in instrumental SST. The coral Sr/Ca records suggest that local effects on SST generate larger amplitude variability than gridded SST products indicate. Reconstructed d18O of seawater (d18Osw) at these sites correlate with instrumental sea surface salinity (SSS; r = 0.64 - 0.67) but not local precipitation (r = -0.10 to - 0.22) demonstrating that the advection and mixing of different salinity water masses may be the predominant control on d18Osw in this region. The Sr/Ca records indicate SST warming over the last 100 years and appears to be related to the expansion of the western Pacific warm pool (WPWP) including an increasing rate of expansion in the last ~20 years. The reconstructed d18Osw over the last 100 years also shows surface water freshening across the SPCZ. The warming and freshening of the surface ocean in our study area suggests that the SPCZ has been shifting (expanding) southeast, possibly related to the southward shift and intensification of the South Pacific gyre over the last 50 years in response to strengthened westerly winds.