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排序方式: 共有1375条查询结果,搜索用时 15 毫秒
31.
http://www.sciencedirect.com/science/article/pii/S1674987114001601   总被引:1,自引:2,他引:1  
Data from a migmatised metapelite raft enclosed within charnockite provide quantitative constraints on the pressure-temperature-time[P-T-t) evolution of the Nagercoil Block at the southernmost tip of peninsular India.An inferred peak metamorphic assemblage of garnet,K-feldspar.sillimanite,plagioclase,magnetite,ilmenite,spinel and melt is consistent with peak metamorphic pressures of 6-8 kbar and temperatures in excess of 900℃.Subsequent growth of cordierite and biotite record high-temperature retrograde decompression to around 5 kbar and 800 C.SHRIMP U-Pb dating of magmatic zircon cores suggests that the sedimentary protoliths were in part derived from felsic igneous rocks with Palaeoproterozoic crystallisation ages.New growth of metamorphic zircon on the rims of detrital grains constrains the onset of melt crystallisation,and the minimum age of the metamorphic peak,to around560 Ma.The data suggest two stages of monazite growth.The first generation of REE-enriched monazite grew during partial melting along the prograde path at around 570 Ma via the incongruent breakdown of apatite.Relatively REE-depleted rims,which have a pronounced negative europium anomaly,grew during melt crystallisation along the retrograde path at around 535 Ma.Our data show the rocks remained at suprasolidus temperatures for at least 35 million years and probably much longer,supporting a long-lived high-grade metamorphic history.The metamorphic conditions,timing and duration of the implied clockwise P-T-t path are similar to that previously established for other regions in peninsular India during the Ediacaran to Cambrian assembly of that part of the Gondwanan supercontinent.  相似文献   
32.
This study represents the first detailed investigation of platinum-group elements (PGEs) in road-deposited sediment (RDS) in Hawaii, USA. Thirty-three sample locations, in two urban watersheds in Honolulu, Oahu, Hawaii were sampled. The <63 μm fraction of RDS was digested with aqua regia, followed by matrix separation with Dowex AG50-X8 cation exchange resin. PGEs were analyzed with inductively coupled plasma-mass spectrometry (ICP-MS) equipped with a desolvating nebulizer. Concentrations of Rh, Pd and Pt in residential streets reached 64, 105 and 506 ng/g, respectively. Maximum enrichment ratios, computed as RDS concentrations relative to baseline values, exceeded 400, indicating a significant anthropogenic signal with the sequence Rh > Pt > Pd. Iridium concentrations were uniformly low <1 ng/g, and enrichment ratios support a geogenic source. Significant interelement PGE correlations (Pd–Pt–Rh), combined with the magnitude of PGE pair-wise ratios (Pt/Pd, Pt/Rh and Pd/Rh), and relative percentages comparable to European RDS and roadside soil in Indiana, USA all suggest an automobile source. Attrition of PGE-loaded automobile catalytic converters and subsequent loss to the environment by exhaust emissions explains the significant environmental signal of PGEs in road environments of Hawaii. Further PGE work is required to quantify urban transport paths as PGEs are known to bioaccumulate, cause cellular damage and may have detrimental human health effects.  相似文献   
33.
New Zealand fur seals in the Kaikoura region breed near a town with expanding tourist and fishing industries and commonly come ashore entangled in nets and plastic debris. However, the rate at which entanglement occurs was previously unknown. A decade of Department of Conservation seal callout data was analysed to determine the level of entanglement in the region and the most common debris type. Monitoring of adult female fur seals released from entanglement provided information on the potential for serious wounds to heal and survivorship of released individuals. Entanglement rates of pinnipeds in Kaikoura are some of the highest reported world-wide (average range: 0.6-2.8%) with green trawl net (42%), and plastic strapping tape (31%) together contributing the most to debris types. Nearly half of the reported entangled seals are successfully released (43%) and post-release monitoring shows that with appropriate intervention the chance of an individual surviving even with a significant entanglement wound is high. Our study demonstrates that while entanglement in the region is high, a successful intervention protocol may help reduce the potential for entanglement-related mortality in the region.  相似文献   
34.
The ocean geoid can be inferred from the topography of the mean sea surface. Satellite altimeters transmit radar pulses and determine the return traveltime to measure sea-surface height. The ERS-1 altimeter stacks 51 consecutive radar reflections on board the satellite to a single waveform. Tracking the time shift of the waveform gives an estimate of the distance to the sea surface. We retrack the ERS-1 radar traveltimes using a model that is focused on the leading edge of the waveforms. While earlier methods regarded adjacent waveforms as independent statistical events, we invert a whole sequence of waveforms simultaneously for a spline geoid solution. Smoothness is controlled by spectral constraints on the spline coefficients. Our geoid solutions have an average spectral density equal to the expected power spectrum of the true geoid. The coherence of repeat track solutions indicates a spatial resolution of 31  km, as compared to 41  km resolution for the ERS-1 Ocean Product. While the resolution of the latter deteriorates to 47  km for wave heights above 2  m, our geoid solution maintains its resolution of 31  km for rough sea. Retracking altimeter waveform data and constraining the solution by a spectral model leads to a realistic geoid solution with significantly improved along-track resolution.  相似文献   
35.
Employment and Socio-spatial Relations in Australia's Cultural Economy   总被引:1,自引:0,他引:1  
This paper examines the significance and contribution of Australian 'creative' industry activities in light of recent debates on the emergence of the 'cultural economy of cities'. First, census employment data and business location counts are used to illustrate patterns of metropolitan primacy and concentration in the cultural industries both across states and in Sydney. Second, the specificities of the locations of cultural production, and the links between cultural industry activities and wider urban-regional change are explored in more detail. A set of observations of urban-regional change is used to demonstrate how the notion of 'cultural economy' should include complex interactions between the material activities of consumers and producers, and the discursive worlds of image makers and place marketers. Urban renewal, housing market pressures and intra-regional migration all mediate Australian experiences of the 'cultural economy'. Such interactions, in addition to key quantitative data on employment and business activity, suggest important policy considerations.  相似文献   
36.
This paper continues recent discussions on the (geo)politics of the production of academic knowledges, in relation to the recent rise of narratives of 'the creative economy'. Creativity and the 'creative industries' are increasingly common components of urban economic development discourse, especially following the release of a set of key books – most notably Charles Landry's The Creative City (2000), and Richard Florida's The Rise of the Creative Class (2002) – that have become popular among economic development planners and cultural policy makers. This paper focuses on the traffic of these books, and their authors, beyond the Anglo-American core. It also briefly discusses policy discourses interpreted from these texts. It is principally, though, a critique of the ways in which academic knowledges circulate, stemming from theorization of academics as creative producers, and of knowledge production as part of the creative economy. The article seeks to critique the means by which particular northern economic knowledges become normative, framed as universal and 'global', and are distributed and absorbed via intellectual 'scenes' and an academic 'celebrity' circuit.  相似文献   
37.
We describe results from a 57-member ensemble of transient climate change simulations, featuring simultaneous perturbations to 54 parameters in the atmosphere, ocean, sulphur cycle and terrestrial ecosystem components of an earth system model (ESM). These emissions-driven simulations are compared against the CMIP3 multi-model ensemble of physical climate system models, used extensively to inform previous assessments of regional climate change, and also against emissions-driven simulations from ESMs contributed to the CMIP5 archive. Members of our earth system perturbed parameter ensemble (ESPPE) are competitive with CMIP3 and CMIP5 models in their simulations of historical climate. In particular, they perform reasonably well in comparison with HadGEM2-ES, a more sophisticated and expensive earth system model contributed to CMIP5. The ESPPE therefore provides a computationally cost-effective tool to explore interactions between earth system processes. In response to a non-intervention emissions scenario, the ESPPE simulates distributions of future regional temperature change characterised by wide ranges, and warm shifts, compared to those of CMIP3 models. These differences partly reflect the uncertain influence of global carbon cycle feedbacks in the ESPPE. In addition, the regional effects of interactions between different earth system feedbacks, particularly involving physical and ecosystem processes, shift and widen the ESPPE spread in normalised patterns of surface temperature and precipitation change in many regions. Significant differences from CMIP3 also arise from the use of parametric perturbations (rather than a multimodel ensemble) to represent model uncertainties, and this is also the case when ESPPE results are compared against parallel emissions-driven simulations from CMIP5 ESMs. When driven by an aggressive mitigation scenario, the ESPPE and HadGEM2-ES reveal significant but uncertain impacts in limiting temperature increases during the second half of the twenty-first century. Emissions-driven simulations create scope for development of errors in properties that were previously prescribed in coupled ocean–atmosphere models, such as historical CO2 concentrations and vegetation distributions. In this context, historical intra-ensemble variations in the airborne fraction of CO2 emissions, and in summer soil moisture in northern hemisphere continental regions, are shown to be potentially useful constraints, subject to uncertainties in the relevant observations. Our results suggest that future climate-related risks can be assessed more comprehensively by updating projection methodologies to support formal combination of emissions-driven perturbed parameter and multi-model earth system model simulations with suitable observational constraints. This would provide scenarios underpinned by a more complete representation of the chain of uncertainties from anthropogenic emissions to future climate outcomes.  相似文献   
38.
Vulnerability of Aboriginal health systems in Canada to climate change   总被引:1,自引:0,他引:1  
Climate change has been identified as potentially the biggest health threat of the 21st century. Canada in general has a well developed public health system and low burden of health which will moderate vulnerability. However, there is significant heterogeneity in health outcomes, and health inequality is particularly pronounced among Aboriginal Canadians. Intervention is needed to prevent, prepare for, and manage climate change effects on Aboriginal health but is constrained by a limited understanding of vulnerability and its determinants. Despite limited research on climate change and Aboriginal health, however, there is a well established literature on Aboriginal health outcomes, determinants, and trends in Canada; characteristics that will determine vulnerability to climate change. In this paper we systematically review this literature, using a vulnerability framework to identify the broad level factors constraining adaptive capacity and increasing sensitivity to climate change. Determinants identified include: poverty, technological capacity constraints, socio-political values and inequality, institutional capacity challenges, and information deficit. The magnitude and nature of these determinants will be distributed unevenly within and between Aboriginal populations necessitating place-based and regional level studies to examine how these broad factors will affect vulnerability at lower levels. The study also supports the need for collaboration across all sectors and levels of government, open and meaningful dialogue between policy makers, scientists, health professionals, and Aboriginal communities, and capacity building at a local level, to plan for climate change. Ultimately, however, efforts to reduce the vulnerability of Aboriginal Canadians to climate change and intervene to prevent, reduce, and manage climate-sensitive health outcomes, will fail unless the broader determinants of socio-economic and health inequality are addressed.  相似文献   
39.
40.
Subsurface deformation is a driver for river path selection when deformation rates become comparable to the autogenic mobility rate of rivers. Here we combine geomorphology, soil and sediment facies analyses, and geophysical data of the Late Quaternary sediments of the central Garo-Rajmahal Gap in Northwest Bengal to link subsurface deformation with surface processes. We show variable sedimentation characteristics, from slow rates (<0.8 mm/year) in the Tista megafan at the foot of the Himalaya to nondeposition at the exposed surface of the Barind Tract to the south, enabling the development of mature soils. Combined subsidence in the Tista fan and uplift of the Barind Tract are consistent with a N-S flexural response of the Indian plate to loading of the Himalaya Mountains given a low value of elastic thickness (15–25 km). Provenance analysis based on bulk strontium concentration suggests a dispersal of sediment consistent with this flexural deformation—in particular the abandonment of the Barind Tract by a Pleistocene Brahmaputra River and the current extents of the Tista megafan lobes. Overall, these results highlight the control by deeply rooted deformation patterns on the routing of sediment by large rivers in foreland settings.  相似文献   
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