Leisure, tourism and social change: Long, J.A. and Hecock, R.D. (eds) Edinburgh: Centre for Leisure Research, Dunfermline College of Physical Education, 1984. 223 pp. £12 hardback     

Lesley France 《Applied geography (Sevenoaks, England)》1985,5(4):363-364

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October 2003     

Katherine Stone  Orville Magoon  Billy Edge  Lesley Ewing 《Environmental Geology》2003,44(7):876-875

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Identifying when microbes biosilicify: The interconnected requirements of acidic pH, colloidal SiO₂ and exposed microbial surface     

Derek R. Amores  Lesley A. Warren   《Chemical Geology》2007,240(3-4):298-312

This study demonstrates discernible biosilicification of natural microbial mats through batch laboratory experiments. Identification of the geochemical requirements for this process to occur includes thermodynamically favorable, but sluggish silica reaction kinetics associated with acidic conditions, and the necessity for colloidal silica rather than dissolved silicic acid species. This study provides the first results to bridge the apparent literature discrepancy between widespread, in-situ observations of microbial silicification, and the inability to demonstrate a detectable microbial impact in this process under well-constrained laboratory conditions. We compared the silica scavenging abilities of three natural microbial mats collected from Yellowstone National Park (YNP) hotsprings, relative to those of both abiotic particle (TiO₂) and solution controls at constant, near-saturated aqueous silica concentrations, while experimental pH and temperature conditions were varied, using both dissolved and colloidal SiO₂ forms. We specifically evaluated three microbial mats sampled from YNP sites all exhibiting saturation with respect to amorphous SiO₂, but possessing variable pH and temperature conditions that should reflect differential kinetics (and therefore biological opportunity) relative to silica polymerization: (1) most biologically favorable, acidic-mesophile (AM: pH 3, T = 35 °C); (2) biologically possible, but less opportune, alkaline, mesophile (ALK-M: pH 8, T = 35 °C) and (3) unlikely to be biologically favorable, alkaline-thermophile (ALK-T: pH 8, T = 80 °C). Comparison of field and laboratory results substantiates the requirements for thermodynamically favorable, but kinetically slower SiO₂ polymerization conditions. Results show that acidic moderate temperature conditions were required for an observable biosilicification impact. Moreover, they also identified for the first time, the necessity specifically for colloidal silica forms which are surface bound under acidic pH conditions, to distinguish discernible biosilicification compared to mineral particle controls. Results also highlight the important influence of mat surface characteristics in this process, specifically the extent of live, non-mineralized, exposed biological mat surface. Greater colloidal SiO₂ scavenging abilities are associated with non-mineralized microbial mat surfaces than with mineral particle surfaces or microbial mat surfaces encrusted with authigenic silica. These results are the first to demonstrate that biosilicification can be a microbially mediated, discernible geobiological process, shedding new light on the longstanding argument in the literature, and opening the door for more sensitive evaluation of this phenomenon in natural systems.  相似文献   

Phytoplankton densities and growth of Mytilus edulis in an Alaskan artificial upwelling system     

Paul  A. J.; Paul  J. M.; Neve  R. A. 《ICES Journal of Marine Science》1978,38(1):100-104

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Diffusion of osmium in pyrrhotite and pyrite: implications for closure of the Re–Os isotopic system     

James M. Brenan  Daniele J. Cherniak  Lesley A. Rose 《Earth and Planetary Science Letters》2000,180(3-4):399-413

In order to better constrain the extent to which common sulfide minerals will retain their osmium isotopic composition subsequent to crystallization, we have conducted experiments to quantify the diffusion behavior of osmium in pyrite and pyrrhotite. Experiments consisted of either (1) isothermal soaking of diffusion couples consisting of natural pyrite or pyrrhotite crystals packed against powdered Os-bearing Fe-sulfide or (2) ‘relaxation’ of initially high near-surface osmium concentrations produced in the latter experiments (pyrite only). Osmium penetration into samples was characterized by depth profiling using Rutherford backscattering spectroscopy (RBS) (pyrite) or electron microprobe analyses across sectioned run products (pyrrhotite). Results of the first type of diffusion experiment involving pyrite show only limited osmium penetration into sample surfaces, with the extent of penetration uncorrelated with run duration. Images of pyrite samples using atomic force microscopy show roughening of initially smooth surfaces as a consequence of step formation and suggest that osmium incorporation into the near-surface occurred by solute uptake during step growth and not by volume diffusion. Prolonged (1000⁺ h) ‘relaxation’ experiments revealed no additional osmium penetration into pyrite surfaces and based on the depth resolution for RBS, a maximum diffusion coefficient of 2.5×10⁻²³ m²/s at 500°C was calculated. Experiments involving pyrrhotite over the temperature range of 950–1100°C showed extensive osmium uptake and osmium concentration gradients that conform with Fickian diffusion behavior. We found that pyrrhotite Fe/S could be varied by changes in the composition of the starting material and osmium source and over the range of Fe/S produced in experiments (molar Fe/S=0.83–0.90), we observed no systematic variation in the osmium diffusion coefficient. Diffusion coefficients measured parallel to the a crystallographic axis were on average 1.4× higher than values measured parallel to c and regression of the c-axis data yielded the Arrhenius relation:The application of these diffusion data to simple models of diffusive exchange during static or polythermal time–temperature histories is used to assess the conditions under which radiogenic osmium will be retained. During isothermal annealing, calculations indicate that the cores of millimeter-sized spherical pyrrhotite crystals undergoing diffusive exchange with an external osmium reservoir will have their initial compositions perturbed in ≤0.5 Ma at temperatures exceeding 400°C. Pyrite undergoing the same process at 500°C requires in excess of 10 Ma before crystal cores are affected. The relatively short ‘core retention’ time-scales for pyrrhotite indicates that this mineral may be prone to isotopic resetting following relatively brief crustal thermal events, thus possibly accounting for the scatter that commonly occurs in Re–Os isochrons generated from massive sulfide samples. Calculated closure temperatures (T_c) for osmium exchange in pyrrhotite yielded values of 300–400°C for grain sizes ranging from 10 to 1000 μm. These values of T_c are similar to those calculated for Ar retention in biotite, and considerably lower than for Sr in apatite and plagioclase, for example. Such low closure temperatures for pyrrhotite suggest this mineral will date the final stage in the cooling of a magmatic system and possibly be susceptible to open system osmium exchange in the presence of late-stage hydrothermal fluids. This latter result infers that caution be applied when interpreting elevated initial osmium isotopic ratios as a product of crustal assimilation at the magmatic stage.  相似文献   

Climate change risks to US infrastructure: impacts on roads,bridges, coastal development,and urban drainage     

James E. Neumann  Jason Price  Paul Chinowsky  Leonard Wright  Lindsay Ludwig  Richard Streeter  Russell Jones  Joel B. Smith  William Perkins  Lesley Jantarasami  Jeremy Martinich 《Climatic change》2015,131(1):97-109

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Algal blooms and climate anomalies in north‐east New Zealand,August ‐December 1992     

Lesley L. Rhodes  Allison J. Haywood  W. J. Ballantine  A. Lincoln MacKenzie 《新西兰海洋与淡水研究杂志》2013,47(4):419-430

A raphidophyte‐dominated phytoplankton bloom extended discontinuously along the northeastern coastline of New Zealand, from Bream Tail, north of Leigh, to the western coast of the Coromandel Peninsula from late August until December 1992. The bloom was associated with an “El‐Niño” phase of the Southern Oscillation, resulting in unusually cold sea temperatures. The dominant bloom species in the north was Fibrocapsa japonica and in the south Heterosigma akashiwo. Associated species included the coccolithophorid Gephyrocapsa oceanica and the naked form of the silicoflagellate Dictyocha speculum. By December, numbers of the armoured form of D. speculum had increased, as those of raphidophytes and coccolithophorids declined. Bioassays to test for shellfish biotoxins were negative and Artemia salina bioassays, indicators of ichthyotoxicity, were negative except for Heterosigma akashiwo cultures, isolated from Coromandel water samples.  相似文献   

Diversifying Ethnicity in Australia's Population and Environment Debates   总被引：1，自引：0，他引：1  

Natascha Klocker  Lesley Head 《The Australian geographer》2013,44(1):41-62

Population–environment debates in Australia are at an impasse. While the ability of this continent to sustain more migrants has attracted persistent scrutiny, nuanced explorations of diverse migrant cultures and their engagements with Australian landscapes have scarcely begun. Yet as we face the challenges of a climate changing world we would undoubtedly benefit from the most varied knowledges we can muster. This paper brings together three arenas of environmental debate circulating in Australia—the immigration/carrying capacity debate, comparisons between Indigenous and Anglo-European modes of environmental interaction, and research on household sustainability dilemmas—to demonstrate the exclusionary tendencies of each. We then attempt to reorient them in productive ways, by attending to the complexity of environmental sustainability in a context of immense ethnic diversity. Attentiveness to ethnic diversity offers three important insights: (1) Anglo-European Australian understandings of nature and environmentalism are culturally specific, but other perspectives are possible; (2) tensions can arise when ethnic differences in environmental attitude or practice come into contact; and (3) cultural environmental research offers scope to identify ethnically diverse vernacular sustainability practices that should be supported. Each of these threads requires attention in a context where population–environment debates often overlook cultural complexity, and readily spiral into strident anti-immigration sentiments.  相似文献   

Consistent scale-dependency of future increases in hourly extreme precipitation in two convection-permitting climate models     

Helsen  Samuel  van Lipzig  Nicole P. M.  Demuzere  Matthias  Vanden Broucke  Sam  Caluwaerts  Steven  De Cruz  Lesley  De Troch  Rozemien  Hamdi  Rafiq  Termonia  Piet  Van Schaeybroeck  Bert  Wouters  Hendrik 《Climate Dynamics》2020,54(3):1267-1280

Climate Dynamics - Convection-permitting models (CPMs) have been proven successful in simulating extreme precipitation statistics. However, when such models are used to study climate change,...  相似文献   

Assembling Birrarung Wilam: a case study of Indigenous public artwork in the city     

Julia Flaster  Lesley Head 《The Australian geographer》2020,51(1):19-34

ABSTRACT

Indigenous public artworks in Australian urban spaces have challenged assumptions of Indigenous absence from the city. This paper examines the construction of Birrarung Wilam, in central Melbourne, in the period 2005–2008. We use archival documents and semi-structured interviews to analyse the collaborations between Indigenous and non-Indigenous participants in a project sponsored by the city. We show the particular mediating contribution of ‘fabricators’: a group of commissioned workers and tradespeople with material-specific expertise. Person to person encounters occurred through the modules of project management, with limited scope for long-term engagement. Despite being embedded in formal state-based recognition, Birrarung Wilam asserts Indigenous self-recognition through the renewal and adaptation of Indigenous material practices and traditions and the refusal to provide straightforward interpretive materials at the site. The study provides support for arguments that challenge a simple binary of co-option and resistance in interpreting such public art practice.  相似文献