19 resultados para winds

em Deakin Research Online - Australia


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The giant crab Pseudocarcinus gigas occurs along the continental shelf break of southern Australia. During the summer alongshore winds cause cooler water to upwell onto the shelf, and the crabs move from deeper water onto the shelf where there is more food. The combination of a preferred thermal niche and a depth-stratified food supply defines the favorable foraging environments that enhance the growth of P. gigas. Climate change is expected to cause a southerly shift of the austral subtropical high-pressure belt, and modelers have predicted more upwelling-favorable winds. The associated increase in the circulation of cooler water across the shelf is likely to provide P. gigas with an increased access to benthic food resources and their growth rate may increase in some regions.

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Eocene ocean currents and prevailing winds correlate with over-water dispersals of terrestrial mammals from Africa to Madagascar. Since the Early Miocene (about 23 Ma), these currents flowed in the reverse direction, from the Indian Ocean towards Africa. The Comoro Islands are equidistant between Africa and Madagascar and support an endemic land vertebrate fauna that shares recent ancestry predominantly with Madagascar. We examined whether gene flow in two Miniopterus bat species endemic to the Comoros and Madagascar correlates with the direction of current winds, using uni- and bi-parentally inherited markers with different evolutionary rates. Coalescence-based analyses of mitochondrial matrilines support a Pleistocene (approximately 180 000 years ago) colonization event from Madagascar west to the Comoros (distance: 300 km) in the predicted direction. However, nuclear microsatellites show that more recent gene flow is restricted to a few individuals flying against the wind, from Grande Comore to Anjouan (distance: 80 km).

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We are witnessing the beginnings of what could well be significant change in Myanmar. Elections in November 2010 were quickly followed by the release of opposition leader Aung San Suu Kyi, then by the resignation of Senior-General Than Shwe, dissolution of the State Peace and Development Council (SPDC), the opening of parliament, and the inauguration of Thein Sein as President on 30th March 2011. Thein Sein's inauguration speech called for national reconciliation and an end to corruption, promised a more market-oriented economy, and vowed to create employment opportunities. He also pledged to develop the health and education sectors in cooperation with international organisations, and to alleviate poverty. While some fear this may only be rhetoric, a growing number of indications suggest that major political and economic reform may indeed be getting underway. This paper traces these recent developments and the possibility of significantly improved international development cooperation in Myanmar, particularly as it affects the prospects of poverty alleviation efforts and cooperation with Western INGO and multilateral agencies. It analyses the implications of this reform on international development assistance and cooperation from the perspectives of humanitarian needs, international relations theory, development theory, and political philosophy.

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Experiments were carried out on an intermittent estuary during its closed (summer) and open (winter) states to identify the physical processes responsible for vertical mixing across the halocline, and to quantify vertical fluxes of oxygen and salt between water layers. During the blocked phase a two-layer structure was observed, with a brackish surface layer overlying old seawater. Within a deep basin the wind-driven turbulent mixing was consistent with the measured surface-layer turbulent dissipation, but the dissipation in the bottom layer appeared to be driven by internal seiching. In the shallow regions of the estuary vertical fluxes of dissolved oxygen were indicative of oxygen demand by respiration and remineralization of organic material in bottom water and sediments. During the estuary's open phase a three-layer structure was observed, having a fresh, river-derived surface layer, a middle layer of new seawater, and a bottom layer of old seawater. In the shallower regions surface-layer turbulent diffusion was consistent with the strong, gusty winds experienced at the time. The dissolved oxygen of the incoming seawater decreased to very low values by the time it reached the upstream deep basin as a result of the low cross-pycnocline oxygen flux being unable to compensate for the oxygen utilization. At least 50 % of the cross-pycnocline salt fluxes in the shallow reaches of the open estuary are suggested to be driven by Holmboe instabilities.

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Cetacean strandings elicit much community and scientific interest, but few quantitative analyses have successfully identified environmental correlates to these phenomena. Data spanning 1920–2002, involving a total of 639 stranding events and 39 taxa groups from southeast Australia, were found to demonstrate a clear 11–13- year periodicity in the number of events through time. These data positively correlated with the regional persistence of both zonal (westerly) and meridional (southerly) winds, reflecting general long-term and large-scale shifts in sea-level pressure gradients. Periods of persistent zonal and meridional winds result in colder and presumably nutrient-rich waters being driven closer to southern Australia, resulting in increased biological activity in the water column during the spring months. These observations suggest that large-scale climatic events provide a powerful distal influence on the propensity for whales to strand in this region. These patterns provide a powerful quantitative framework for testing hypotheses regarding environmental links to strandings and provide managers with a potential predictive tool to prepare for years of peak stranding activity.

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This report presents the results of an analysis of three years of tide and meteorological data aimed at delineating the influences of atmospheric pressure, waves, onshore winds and longshore winds on coastal sea levels West of Port Phillip Bay, Victoria« The data was used to develop predictive and hindcasting techniques for meteorological tides on the Otway Coast, using statistical methods, an empirical method and a mathematical model. The nature and magnitude of contributions of the various components of the meteorological tide, and the general variability of monthly and seasonal variations were also studied. It was found that meteorological tides on the Otway Coast can account for significant sea level changes, with the main factors being wind and atmospheric pressure. The wind component of the meteorological tide was found to be approximately twice the pressure component, and longshore winds were found to be more significant than onshore winds for wind setup on the Otway Coast. The meteorological tide models developed enable estimates of wind setup and atmospheric pressure setup on the Otway Coast to be readily computed using data from synoptic charts. The wave setup component could not be separated from the meteorological tide and is included in the wind setup component. The results of the investigation are relevant to the design and maintenance of coastal engineering works, and point to the need for the establishment and operation of coastal management schemes on the Otway Coast.

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The Afro–Siberian Red Knot subspecies, Calidris canutus canutus, winters mainly on Banc d’Arguin, Mauritania, West Africa. An International Wader Study Group project carried out in 1979 suggested that during northward migration Red Knots cover their migration between the wintering grounds and the Siberian breeding grounds in two long-distance non-stop flights, stopping only in the Wadden Sea in Schleswig-Holstein, Germany. Each year Red Knots also visit staging sites along the French Atlantic coast in addition to the German Wadden Sea. Ever since 1979, the French staging sites have been counted on a regular basis and here we present the count data from these 30 years. In some years more than 20% of the population used the French Atlantic coast as a staging site, but numbers are highly variable from one year to the next. We suggest that high numbers in France might occur when birds have to stop short of the Wadden Sea because of head-winds and/or a lack of tail-winds en route from West Africa.

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Numerous animals move vast distances through media with stochastic dynamic properties. Avian migrants must cope with variable wind speeds and directions en route, which potentially jeopardize fine-tuned migration routes and itineraries. We show how unpredictable winds affect flight times and the use of an intermediate staging site by red knots (Calidris canutus canutus) migrating from west Africa to the central north Siberian breeding areas via the German Wadden Sea. A dynamic migration model incorporating wind conditions during flight shows that flight durations between Mauritania and the Wadden Sea vary between 2 and 8 days. The number of birds counted at the only known intermediate staging site on the French Atlantic coast was strongly positively correlated with simulated flight times. In addition, particularly light-weight birds occurred at this location. These independent results support the idea that stochastic wind conditions are the main driver of the use of this intermediate stopover site as an emergency staging area. Because of the ubiquity of stochastically varying media, we expect such emergency habitats to exist in many other migratory systems, both airborne and oceanic. Our model provides a tool to quantify the effect of winds and currents en route.

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An understanding of pinniped haulout behaviour can provide information on how animals interact with their environment, their foraging strategies and the behaviour of their prey. For Weddell seals Leptonychotes weddelli, knowledge of haulout patterns and the environmental drivers of haulout is comprehensive for the austral spring and summer, but is poorly described outside this period. Pinniped behaviour is commonly examined using satellite telemetry; however, it is unclear whether the behavioural state of the seal can itself influence data acquisition. We examined haulout behaviour of female Weddell seals in eastern Antarctica over 3 winters (March to August, 2006–2008) using satellite-linked data loggers. Haulout behaviour followed a diel cycle with predominantly nocturnal haulouts. The environmental variables wind speed and temperature were influential on haulout, with seals tending to haul out more in lower winds and at higher temperatures. Haulout duration decreased across the winter, as did the number of satellite uplinks, suggesting that haulout duration played a role in data acquisition. There was no evidence of a decline in tag condition over this period, indicating that the decrease in uplinks was primarily the result of the winter behaviour of the seals. Overall, the number of haulout locations in the data set was over-represented, with more uplinks per hour occurring when the seals were hauled out than when they were at sea. For Weddell seals and other ice seals, tracking data that include haulout locations can bias spatial representations of foraging behaviour (e.g. haulout sites may be mistaken for regions of area-restricted search).

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Backgound Birch pollen allergens have been implicated as asthma triggers; however, pollen grains are too large to reach the lower airways where asthmatic reactions occur. Respirable-sized particles containing birch pollen allergens have been detected in air filters, especially after rainfall but the source of these particles has remained speculative.

Objective To determine the processes by which birch pollen allergens become airborne particles of respirable size with the potential to contribute to airways inflammation.

Methods Branches with attached male catkins were harvested and placed in a controlled emission chamber. Filtered dry air was passed through the chamber until the anthers opened, then they were humidified for 5 h and air-dried again. Flowers were disturbed by wind generated from a small electric fan. Released particles were counted, measured and collected for immuno-labelling and high-resolution microscopy.

Results Birch pollen remains on the dehisced anther and can rupture in high humidity and moisture. Fresh pollen takes as long as 3 h to rupture in water. Drying winds released an aerosol of particles from catkins. These were fragments of pollen cytoplasm that ranged in size from 30 nm to 4 μm and contained Bet v 1 allergens.

Conclusion When highly allergenic birch trees are flowering and exposed to moisture followed by drying winds they can produce particulate aerosols containing pollen allergens. These particles are small enough to deposit in the peripheral airways and have the potential to induce an inflammatory response.

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Background: Investigations into the occurrence and health effects of yeast-like fungi in the outdoor air in the US have been limited. We sought to identify a respirable-sized fungus common in the Pasadena air, locate a major source for the emissions and investigate its relevance to allergic disease. Methods: Yeast-like fungi sampled from the environment were isolated, microscopically examined and sequenced. Pasadena allergy patients were skin tested with commercially available fungal extracts. Patient serum was immunoanalyzed for specific IgE reactivity. Nearby vegetation was analyzed in a controlled emission chamber to find a major source for the aerosols. Results: Hyaline unicellular conidia comprised up to 90% (41,250 m<sup>-3</sup> of air) of total fungal counts and generally peaked at night and during periods of rainfall and ensuing winds throughout the fall and winter. Flowers were determined to be a major source of the emissions. The cellular and colonial morphology of isolates were consistent with Aureobasidium species. The sequence of the D1/D2 region of the 26S ribosomal subunit of isolates from flowers showed identity to two strains of Aureohasidium pullulans (black yeast). Seventeen percent (16/94) of atopic individuals had positive skin testing with A. pullulans extract. Patient sera gE identified several high molecular weight allergens in Aureobasidium extracts. Conclusions: Respirable-sized conidia of A. pullulans are emitted from flowers and form high concentrations in the air. They are associated with immediate reactivity on skin tests, bind to patient sera IgE, and might be relevant in allergic upper and lower airway diseases.

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Pollen allergy has been found in 80–90% of childhood asthmatics and 40–50% of adult-onset asthmatics. Despite the high prevalence of atopy in asthmatics, a causal relationship between the allergic response and asthma has not been clearly established. Pollen grains are too large to penetrate the small airways where asthma occurs. Yet pollen cytoplasmic fragments are respirable and are likely correlated with the asthmatic response in allergic asthmatics. In this review, we outline the mechanism of pollen fragmentation and possible pathophysiology of pollen fragment-induced asthma. Pollen grains rupture within the male flowers and emit cytoplasmic debris when winds or other disturbances disperse the pollen. Peak levels of grass and birch pollen allergens in the atmosphere correlated with the occurrence of moist weather conditions during the flowering period. Thunderstorm asthma epidemics may be triggered by grass pollen rupture in the atmosphere and the entrainment of respirable-sized particles in the outflows of air masses at ground level. Pollen contains nicotinamide adenine dinucleotide phosphate (reduced) oxidases and bioactive lipid mediators which likely contribute to the inflammatory response. Several studies have examined synergistic effects and enhanced immune response from interaction in the atmosphere, or from co-deposition in the airways, of pollen allergens, endogenous pro-inflammatory agents, and the particulate and gaseous fraction of combustion products. Pollen and fungal fragments also contain compounds that can suppress reactive oxidants and quench free radicals. It is important to know more about how these substances interact to potentially enhance, or even ameliorate, allergic asthma.

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This article is a study of the attitudes of Australian government ministers and officials towards the decolonisation of the Pacific island colonial territories in the decade from 1962 to 1972. It argues that the Australian state was very slow to recognise and understand that the winds of change would also sweep through the South Pacific and see the emergence of many new island nations by 1980.

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Recent severe hurricanes in the Caribbean and south-east United States have had devastating socio-economic effects, and there is a pressing need to learn how animals are impacted by such events. We serendipitously deployed a multi-channel data logger onto a hawksbill turtle (Eretmochelys imbricata) during the breeding season in 1998 and logged various aspects of her behaviour before, during and after passage of hurricane Georges. As Georges passed by, the turtle made shorter dives, became more active and spent less time at the surface between dives compared with its baseline, non-storm activity. However, after passage of the hurricane the turtle quickly resumed its pre-hurricane behaviour and nested successfully a few days later. These results show that, in this case, the hurricane had a minor impact on the submerged animal presumably because of the dampening effect of depth on high winds over water.