Partly obscured accretion disc model to explain shifted broad Balmer emission lines of active galactic nuclei     

Xue-Guang Zhang  Deborah Dultzin  Ting-Gui Wang  Guinevere Kauffmann 《Monthly notices of the Royal Astronomical Society》2009,397(3):1510-1520

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Architecture of the Oman–UAE ophiolite: evidence for a multi-phase magmatic history     

K. M. Goodenough  M. T. Styles  D. Schofield  R. J. Thomas  Q. C. Crowley  R. M. Lilly  J. McKervey  D. Stephenson  J. N. Carney 《Arabian Journal of Geosciences》2010,3(4):439-458

The Oman–United Arab Emirates ophiolite is the world’s largest ophiolite. It is divided into 12 separate fault-bounded blocks, of which the northern three lie wholly or partly in the United Arab Emirates. Extensive mapping has shown that the United Arab Emirates blocks contain mantle and crustal sections which correspond to the classic ‘Penrose conference’ ophiolite definition but which are cut by a voluminous later magmatic sequence including ultramafic, mafic and felsic components. Samples from the later magmatic sequence are dated at 96.4?±?0.3, 95.74?±?0.3 and 95.2?±?0.3 Ma; the early crustal section, which has not been dated directly, is thus constrained to be older than c. 96.4 Ma. Petrological evidence shows that the early crustal section formed at a spreading ridge, but the later magmatic sequence was formed from hydrous magmas that produced different mineral crystallisation sequences to normal mid-ocean ridge basalt (MORB). Mineral and whole-rock geochemical analyses show that the early crustal rocks are chemically similar to MORB, but the later magmatic sequence has chemical features typically found in supra-subduction zone (SSZ) settings. The ophiolite in the United Arab Emirates thus preserves clear evidence for two stages of magmatism, an early episode formed at a spreading centre and a later episode associated with the onset of subduction. Similar two-stage magmatism has been recognised in the Oman sector, but the United Arab Emirates contains the most voluminous SSZ magmatism yet described from this ophiolite.  相似文献   

Analysis and simulated diagenesis of kerogen in a Recent bottom mud from Mono Lake,California: a comparison with selected ancient kerogens     

Deborah S. Sklarew 《Geochimica et cosmochimica acta》1979,43(12):1949-1958

The insoluble organic matter, or kerogen, in a Recent bottom mud (<1000yr old) from Mono Lake, California, has been analyzed by vacuum pyrolysis-GC-MS and compared with the kerogen from several Precambrian rocks, including the Belingwe and Transvaal stromatolites. The Mono Lake kerogen consists mainly of cyclic and acyclic aliphatic components with lesser amounts of aromatics present. It is less aromatic and more susceptible to thermal degradation than the Precambrian kerogens, and its products show a much greater diversity especially among the unsaturated aliphatics and the heteroatomic components. The presence of these compounds, most notably 2,5-dimethylfuran, in the Mono Lake kerogen indicates a relatively rapid formation and incorporation into a young kerogen and suggests that their presence in the Precambrian kerogens, such as the Belingwe stromatolite, may be consistent with an ancient biological origin.In simulated diagenesis experiments the Recent mud was heated at 150°C for 3 months or 225°C for 8 months. The former was insufficient to affect the kerogen pyrolysis products. The latter, however, caused a large decrease in the heteroatomic components and a slight increase in the abundance of n-alkanes relative to that of the cyclic and branched alkanes. This suggests that the presence of some of these components in Precambrian rocks should be consistent with a high degree of preservation of these rocks, as appears to be the case for the Belingwe and Transvaal stromatolites.  相似文献   

A Probabilistic Displacement-based Vulnerability Assessment Procedure for Earthquake Loss Estimation   总被引：8，自引：3，他引：5  

Helen?Crowley  Rui?PinhoEmail author  Julian?J.?Bommer 《Bulletin of Earthquake Engineering》2004,2(2):173-219

Earthquake loss estimation studies require predictions to be made of the proportion of a building class falling within discrete damage bands from a specified earthquake demand. These predictions should be made using methods that incorporate both computational efficiency and accuracy such that studies on regional or national levels can be effectively carried out, even when the triggering of multiple earthquake scenarios, as opposed to the use of probabilistic hazard maps and uniform hazard spectra, is employed to realistically assess seismic demand and its consequences on the built environment. Earthquake actions should be represented by a parameter that shows good correlation to damage and that accounts for the relationship between the frequency content of the ground motion and the fundamental period of the building; hence recent proposals to use displacement response spectra. A rational method is proposed herein that defines the capacity of a building class by relating its deformation potential to its fundamental period of vibration at different limit states and comparing this with a displacement response spectrum. The uncertainty in the geometrical, material and limit state properties of a building class is considered and the first-order reliability method, FORM, is used to produce an approximate joint probability density function (JPDF) of displacement capacity and period. The JPDF of capacity may be used in conjunction with the lognormal cumulative distribution function of demand in the classical reliability formula to calculate the probability of failing a given limit state. Vulnerability curves may be produced which, although not directly used in the methodology, serve to illustrate the conceptual soundness of the method and make comparisons with other methods.  相似文献   

Capitalism, masculinity and whiteness in the dialectical landscape: The case of Tarzan and the Tycoon     

Deborah Dixon  John Grimes 《GeoJournal》2004,59(4):265-275

The intent of this paper is to explore how ‘reel’ and ‘real’ landscapes can be rendered dialectic. The analysis focuses on the filming of Tarzan's Secret Treasure (1941) at the wildlife preserve of Wakulla Springs in Florida, which was administered by the financial tycoon Ed Ball. Using Mitchell's recent commentaries on ‘good’ and ‘bad’ dialectics as our entry point, we offer two readings of this cinematic process. The first renders the on and off screen Wakulla Springs as ideological fodder, serving to valorise capital, masculinity and whiteness. The second reading addresses how this place has been actively constructed from discourses pertaining to class, gender and race, such that Wakulla exists as a series of fully relational spaces within diverse contexts, both ‘real’ and ‘reel’. In structuring our analysis in this manner, we hope to make clear why it does indeed matter for film geographers to acknowledge the conceptual presumptions brought to bear in the framing of the real and the reel as objects of analysis. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

A Regionally Based Energy End‐Use Strategy: Case Studies from Centre County,Pennsylvania*     

Deborah Feder 《The Professional geographer》2004,56(2):185-200

The production and use of fossil fuels and nonrenewable electricity creates many forms of environmental degradation. To reduce degradation, this research suggests an energy strategy based on energy end‐use analysis and regional geography. Energy end‐use analysis and regional geography are used to match renewable energy resources with site‐specific, end‐use needs. Fieldwork conducted within Centre County, Pennsylvania, demonstrates that small‐scale solar, wind, and micro‐hydropower resources could displace a proportion of household electricity use. Such an approach meets energy end‐use needs, while conserving fossil fuels and reducing environmental degradation.  相似文献   

The Consumer Society and the Postmodern City by David B Clarke     

Deborah Leslie 《Area》2006,38(2):221-222

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Using logistic regression to merge mineral resource databases     

Deborah J. Shields  Stella W. Todd 《Natural Resources Research》1998,7(1):53-61

The purpose of this project was to develop and test a methodology for determining the likelihood that mineral resource location records from two nationwide mineral resource information databases represent the same site. The long-term goal is to create a comprehensive database by merging the Mineral Resource Data System (MRDS) of the U.S. Geological Survey, and the Mineral Availability System/Mineral Industry Location System (MAS/MILS) of the U.S. Bureau of Mines (now part of the Geological Survey). Part of that process involves linking records for the same site from each database. Match probabilities were estimated using a logistic regression of mineral resource location attributes, derived from known matched (cross-referenced) and known unmatched randomly sampled mineral site pairs from within the conterminous United States (n=10,000). Model accuracy was assessed using a randomly sampled test dataset, not used in logistic model development (n=4,000). Probability distributions were similar between the development and test datasets. The overall agreement beyond chance was good for the test data set using the kappa statistic. Classification accuracy was 89.6% for known matched site pairs and 84.0% for known unmatched site pairs based on a probability threshold of 0.50 for a match. Distributions of attributes were similar between the development and test datasets. This classification method is a viable approach for estimating match probabilities between database records.  相似文献   

A natural resource damage assessment model for coastal and marine environments     

Thomas A. Grigalunas  James J. Opaluch  Deborah French  Mark Reed  Dean Knauss 《GeoJournal》1988,16(3):315-321

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Late Pleistocene variations in Antarctic sea ice II: effect of interhemispheric deep-ocean heat exchange     

Thomas J Crowley  Claire L Parkinson 《Climate Dynamics》1988,3(2):93-103

Variations in production rates of warm North Atlantic Deep Water (NADW) have been proposed as a mechanism for linking climate fluctuations in the northern and southern hemispheres during the Pleistocene. We have tested this hypothesis by examining the sensitivity of a thermodynamic/dynamic model for Antarctic sea ice to changes in vertical ocean heat flux and comparing the simulations with modified CLIMAP sea-ice maps for 18 000 B.P. Results suggest that changes in NADW production rates, and the consequent changes in the vertical ocean heat flux in the Antarctic, can only account for about 20%–30% of the overall variance in Antarctic sea-ice extent. This conclusion has been validated against an independent geological data set involving a time series of sea-surface temperatures from the subantarctic. The latter comparison suggests that, although the overall influence of NADW is relatively minor, the linkage may be much more significant at the 41 000-year obliquity period. Despite some limitations in the models and geological data, we conclude that NADW variations may have played only a modest role in causing late Pleistocene climate change in the high latitudes of the southern hemisphere. Our conclusion is consistent with calculations by Manabe and Broccoli (1985) suggesting that atmospheric CO₂ changes may be more important for linking the two hemispheres.  相似文献