10 resultados para radiocarbon dating

em Deakin Research Online - Australia


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Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences.

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In this article we address how a contemporary adaptation of the 'speed dating' model was used for educational purposes with two cohorts of social work students. We outline the dimensions of 'speed dating' as a contemporary social phenomenon, then address how this model relates specifically to groupwork process, and can be used to facilitate social work student learning. The curriculum for two classroom group activities using the 'speed dating' model are outlined, the first to develop university level study skills, the second for debriefing field placement learning experiences. Finally we examine why the 'speed dating' metaphor was successful in provoking a playful yet constructively creative space for students to engage in groupwork process.

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As published in the final reports by the College of Wooster and Sydney University, the dating and analysis of the excavated remains of the three churches and their associated finds at Pella, Jordan, display some puzzling aspects. This paper argues that, in these reports, two of the churches appear to have been dated up to a century later than they should have been, while the suggested date for the third now appears too early. This article examines the problem in the context of a new architectural and theological typology of churches in the East Mediterranean from the 4th to 6th centuries AD.

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This thesis explored the relative utility of evolutionary and ecological theories to understand under which conditions children in non-biological families are most at risk of childmaltreatment.  The study revealed that single-mothers have complex needs and stressors, which may increase their vulnerability and impact on decisions made in selection of partners.

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Human activities in coastal areas frequently cause loss of benthic macrophytes (e.g. seagrasses) and concomitant increases in microalgal production through eutrophication. Whether such changes translate into shifts in the composition of sediment detritus is largely unknown, yet such changes could impact the role these ecosystems play in sequestrating CO 2. We reconstructed the sedimentary records of cores taken from two sites within Botany Bay, Sydney - the site of European settlement of Australia - to look for human-induced changes in dominant sources of detritus in this estuary. Cores covered a period from the present day back to the middle Holocene (~6000 years) according to 210Pb profiles and radiocarbon ( 14C) dating. Depositional histories at both sites could not be characterized by a linear sedimentation rate; sedimentation rates in the last 30-50 years were considerably higher than during the rest of the Holocene. C : N ratios declined and began to exhibit a microalgal source signature from around the time of European settlement, which could be explained by increased nutrient flows into the Bay caused by anthropogenic activity. Analysis of stable isotopic ratios of 12C/ 13C showed that the relative contribution of seagrass and C 3 terrestrial plants (mangroves, saltmarsh) to detritus declined around the time of rapid industrial expansion (~1950s), coinciding with an increase in the contribution of microalgal sources. We conclude that the relative contribution of microalgae to detritus has increased within Botany Bay, and that this shift is the sign of increased industrialization and concomitant eutrophication. Given the lower carbon burial efficiencies of microalgae (~0.1%) relative to seagrasses and C 3 terrestrial plants (up to 10%), such changes represent a substantial weakening of the carbon sink potential of Botany Bay - this occurrence is likely to be common to human-impacted estuaries, and has consequences for the role these systems play in helping to mitigate climate change. © 2011 Blackwell Publishing Ltd.

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In 2007, I asked for a show of hands of people who ‘might consider online dating as a way of finding a partner’. Not a single hand went up and the lecture theatre was stony silent. The same question, some five years later resulted in a significant show of hands and a buzz of chatter. Something had changed and perceptions around online dating had shifted. Nielsen Research last year found most Australians (51 per cent) had either tried online dating or would consider doing so. RSVP and eHarmony claim to have 2 million members and more than 4 million people have apparently joined RSVP since it was launched 17 years ago. Online dating is experiencing significant growth in Asia as well, with the number of new web services (some, like ‘Muslima’, are tightly focused) growing exponentially. Online dating is a global phenomenon. This paper will use current media studies research literature and data from conversations with university students in Australia and Indonesia to explore how the changing world of online dating is helping/hindering young people as they shape and develop identity, represent themselves in the virtual world and ultimately, how they find love on line.

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Communication, Digital Media and Everyday Life uses stories to explain the journey from ‘new media in communication’ to ‘digital media is communication’ and provide students with a thorough introduction to communication and media theory and practice. It recognises that for generations Y and Z, ‘digital media’ is now embedded into most aspects of everyday life and integrated into contemporary communication as much as speaking, reading and writing.