Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary

Between 34 and 15 million years (Myr) ago, when planetary temperatures were 3-4 degreesC warmer than at present and atmospheric CO2 concentrations were twice as high as today(1), the Antarctic ice sheets may have been unstable(2-7). Oxygen isotope records from deep-sea sediment cores suggest that during this time fluctuations in global temperatures and high-latitude continental ice volumes were influenced by orbital cycles(8-10). But it has hitherto not been possible to calibrate the inferred changes in ice volume with direct evidence for oscillations of the Antarctic ice sheets(11). Here we present sediment data from shallow marine cores in the western Ross Sea that exhibit well dated cyclic variations, and which link the extent of the East Antarctic ice sheet directly to orbital cycles during the Oligocene/Miocene transition (24.1-23.7 Myr ago). Three rapidly deposited glaci-marine sequences are constrained to a period of less than 450 kyr by our age model, suggesting that orbital influences at the frequencies of obliquity (40 kyr) and eccentricity (125 kyr) controlled the oscillations of the ice margin at that time. An erosional hiatus covering 250 kyr provides direct evidence for a major episode of global cooling and ice-sheet expansion about 23.7 Myr ago, which had previously been inferred from oxygen isotope data (Mil event(5)).

Nutritional strategies for the prevention of hypocalcaemia at calving for dairy cows in pasture-based systems

This review considers the current literature on the macro-mineral nutrition of the soon-to-calve, or transition, dairy cow. Calcium is the main focus, since milk fever (clinical hypocalcaemia) appears to be the most common mineral-related problem faced by the transition cow Australia-wide. The importance of minimising calcium intake and optimising the balance of the key dietary electrolytes, sodium, potassium, sulfate, and chloride, in the weeks before calving is highlighted. Excess dietary potassium can, in some situations, induce milk fever, perhaps even more effectively than excess calcium. Excess sodium remains under suspicion. In contrast, excess dietary chlorine and, to a lesser extent, sulfur can improve the ability of the cow to maintain calcium homeostasis. Diets that promote either a hypomagnesaemia or hyperphosphataemia have also the potential to precipitate milk fever at calving. Current prevention strategies focus on the use of forages with moderate to low levels of calcium, potassium, and sodium, and also rely on or utilise addition of chloride and sulfate in the form of 'anionic' feeds. Anionic salts are one example of an anionic feed. However, legitimate questions remain as to the effectiveness of anionic salts in pasture-feeding systems. The causes and prevention of milk fever are considered from the perspective of the variety of Australian feedbases. Impediments to the use of anionic feeds in Australia feeding systems are outlined. The potential for improving maternal reserves of calcium around calving to reduce the risk of milk fever is also discussed.

The developmental activities of elite ice hockey players

The purpose of this study was to analyze the development of four 20 year-old elite hockey players through an in-depth examination of their sporting activities. The theoretical framework of deliberate practice (Ericsson, Krampe, & Tesch-Römer, 1993) and the notion of deliberate play (Côté, 1999) served as the theoretical foundations. Interviews were conducted to provide a longitudinal and detailed account of each participant's involvement in various sporting activities. The interviewer asked questions about the conditions and sporting activities for each year of development. The data obtained were validated through independent interviews conducted with three parents of three different athletes. The results were consistent with Côté's (1999) three stages of development in sport: the sampling (age 6-12), specializing (age 13-15), and investment (age 16+) years.