The 2dF-SDSS LRG and QSO Survey: evolution of the clustering of luminous red galaxies since z= 0.6     

David A. Wake  Ravi K. Sheth  Robert C. Nichol  Carlton M. Baugh  Joss Bland-Hawthorn  Matthew Colless  Warrick J. Couch  Scott M. Croom  Roberto De Propris  Michael J. Drinkwater  Alastair C. Edge  Jon Loveday  Tsz Yan Lam  Kevin A. Pimbblet  Isaac G. Roseboom  Nicholas P. Ross  Donald P. Schneider  Tom Shanks  Robert G. Sharp 《Monthly notices of the Royal Astronomical Society》2008,387(3):1045-1062

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Geochemistry and hydrology of perched groundwater springs: assessing elevated uranium concentrations at Pigeon Spring relative to nearby Pigeon Mine,Arizona (USA)     

Kimberly R. Beisner  Nicholas V. Paretti  Fred D. Tillman  David L. Naftz  Donald J. Bills  Katie Walton-Day  Tanya J. Gallegos 《Hydrogeology Journal》2017,25(2):539-556

The processes that affect water chemistry as the water flows from recharge areas through breccia-pipe uranium deposits in the Grand Canyon region of the southwestern United States are not well understood. Pigeon Spring had elevated uranium in 1982 (44 μg/L), compared to other perched springs (2.7–18 μg/L), prior to mining operations at the nearby Pigeon Mine. Perched groundwater springs in an area around the Pigeon Mine were sampled between 2009 and 2015 and compared with material from the Pigeon Mine to better understand the geochemistry and hydrology of the area. Two general groups of perched groundwater springs were identified from this study; one group is characterized by calcium sulfate type water, low uranium activity ratio ²³⁴U/²³⁸U (UAR) values, and a mixture of water with some component of modern water, and the other group by calcium-magnesium sulfate type water, higher UAR values, and radiocarbon ages indicating recharge on the order of several thousand years ago. Multivariate statistical principal components analysis of Pigeon Mine and spring samples indicate Cu, Pb, As, Mn, and Cd concentrations distinguished mining-related leachates from perched groundwater springs. The groundwater potentiometric surface indicates that perched groundwater at Pigeon Mine would likely flow toward the northwest away from Pigeon Spring. The geochemical analysis of the water, sediment and rock samples collected from the Snake Gulch area indicate that the elevated uranium at Pigeon Spring is likely related to a natural source of uranium upgradient from the spring and not likely related to the Pigeon Mine.  相似文献   

Linking the Abundance of Estuarine Fish and Crustaceans in Nearshore Waters to Shoreline Hardening and Land Cover     

Matthew S. Kornis  Denise Breitburg  Richard Balouskus  Donna M. Bilkovic  Lori A. Davias  Steve Giordano  Keira Heggie  Anson H. Hines  John M. Jacobs  Thomas E. Jordan  Ryan S. King  Christopher J. Patrick  Rochelle D. Seitz  Heather Soulen  Timothy E. Targett  Donald E. Weller  Dennis F. Whigham  Jim UphoffJr 《Estuaries and Coasts》2017,40(5):1464-1486

Human alteration of land cover (e.g., urban and agricultural land use) and shoreline hardening (e.g., bulkheading and rip rap revetment) are intensifying due to increasing human populations and sea level rise. Fishes and crustaceans that are ecologically and economically valuable to coastal systems may be affected by these changes, but direct links between these stressors and faunal populations have been elusive at large spatial scales. We examined nearshore abundance patterns of 15 common taxa across gradients of urban and agricultural land cover as well as wetland and hardened shoreline in tributary subestuaries of the Chesapeake Bay and Delaware Coastal Bays. We used a comprehensive landscape-scale study design that included 587 sites in 39 subestuaries. Our analyses indicate shoreline hardening has predominantly negative effects on estuarine fauna in water directly adjacent to the hardened shoreline and at the larger system-scale as cumulative hardened shoreline increased in the subestuary. In contrast, abundances of 12 of 15 species increased with the proportion of shoreline comprised of wetlands. Abundances of several species were also significantly related to watershed cropland cover, submerged aquatic vegetation, and total nitrogen, suggesting land-use-mediated effects on prey and refuge habitat. Specifically, abundances of four bottom-oriented species were negatively related to cropland cover, which is correlated with elevated nitrogen and reduced submerged and wetland vegetation in the receiving subestuary. These empirical relationships raise important considerations for conservation and management strategies in coastal environments.  相似文献   

Quantifying impacts of forecast uncertainties on predicted storm surges     

Donald T. Resio  Nancy J. Powell  Mary A. Cialone  Himangshu S. Das  Joannes J. Westerink 《Natural Hazards》2017,88(3):1423-1449

In this paper, we propose a framework for quantifying risks, including (1) the effects of forecast errors, (2) the ability to resolve critical grid features that are important to accurate site-specific forecasts, and (3) a framework that can move us toward performance-based/cost-based decisions, within an extremely fast execution time. A key element presently lacking in previous studies is the interrelationship between the effects of combined random errors and bias in numerical weather prediction (NWP) models and bias and random errors in surge models. This approach examines the number of degrees of freedom in present forecasts and develops an equation for the quantification of these types of errors within a unified system, given the number of degrees of freedom in the NWP forecasts. It is shown that the methodology can be used to provide information on the forecasts and along with the combined uncertainty due to all of the individual contributions. A potential important benefit from studies using this approach would be the ability to estimate financial and other trade-offs between higher-cost “rapid” evacuation methods and lower-cost “slower” evacuation methods. Analyses here show that uncertainty inherent in these decisions depends strongly on forecast time and geographic location. Methods based on sets of surge maxima do not capture this uncertainty and would be difficult to use for this purpose. In particular, it is shown that surge model bias can play a dominant role in distorting the forecast probabilities.  相似文献   

Pengelly's legacy reconsidered: a GIS approach to spatial analysis of palaeontological and archaeological collections from Kents Cavern, England     

Sorin Mihai  Donald A. McFarlane 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(3):319-325

Tens of thousands of palaeontological and archaeological remains were collected by William Pengelly during 19th century excavations of Kents Cavern, but are now widely dispersed between museums. This has previously precluded spatial analysis. We have now assembled available museum records into a single database, and, using our previously-reconstructed Pengelly excavation map as a base, we have been able to exploit the unique Pengelly location code to set up a GIS mapping system. This allows, for the first time, the analysis of spatial patterns. In addition, the GIS serves to highlight potential problems of recording or curation in the original data. Here we report on the construction of the GIS system and its first use in the analysis of spatial distribution of bear remains. The maps demonstrate that Ursus deningeri entered the cave through a now-sealed High Level Chamber entrance at the back of the cave in the middle Pleistocene, whereas Ursus arctos accessed the cave in the late Pleistocene through the now-sealed Northeast Gallery entrance. The denning areas are reconstructed as Labyrinth/Bear's Den for U. deningeri and Vestibule/Great Chamber for U. arctos. Considerable post-mortem re-distribution of the remains of both species is indicated.  相似文献   

Aggregation Methodology for the Circum-Arctic Resource Appraisal   总被引：1，自引：0，他引：1  

John H. Schuenemeyer  Donald L. Gautier 《Mathematical Geosciences》2010,42(5):583-594

This paper presents a methodology that intends to aggregate the results of a recent assessment of undiscovered conventional oil and gas resources of the Arctic by the U.S. Geological Survey. The assessment occurred in 48 geologically defined regions called assessment units. The methodology includes using assessor specified pair-wise correlations as the basis to construct a correlation matrix. Sampling from this matrix generates more realistic uncertainty estimates of aggregated resources than if assumptions of total independence or total dependence are made. The latter two assumptions result in overly narrow or overly broad estimates. Aggregation results for resources in regions north of the Arctic Circle are presented.  相似文献   

A Simple Model for the Vertical Transport of Reactive Species in the Convective Atmospheric Boundary Layer     

Leif Kristensen  Donald H. Lenschow  David Gurarie  Niels Otto Jensen 《Boundary-Layer Meteorology》2010,134(2):195-221

We have developed a simple, steady-state, one-dimensional second-order closure model to obtain continuous profiles of turbulent fluxes and mean concentrations of non-conserved scalars in a convective boundary layer without shear. As a basic tool we first set up a model for conserved species with standard parameterizations. This leads to formulations for profiles of the turbulent diffusivity and the ratio of temperature-scalar covariance to the flux of the passive scalar. The model is then extended to solving, in terms of profiles of mean concentrations and fluxes, the NO _x –O₃ triad problem. The chemical reactions involve one first-order reaction, the destruction of NO₂ with decay time τ, and one second-order reaction, the destruction of NO and O₃ with the reaction constant k. Since the fluxes of the sum concentrations of NO _x = NO + NO₂ and O₃ + NO₂ turn out to be constant throughout the boundary layer, the problem reduces to solving two differential equations for the concentration and the flux of NO₂. The boundary conditions are the three surface fluxes and the fluxes at the top of the boundary layer, the last obtained from the entrainment velocity, and the concentration differences between the free troposphere and the top of the boundary layer. The equations are solved in a dimensionless form by using 1/(kτ) as the concentration unit, the depth h of the boundary layer as the length unit, the convective velocity scale w _* as the velocity unit, and the surface temperature flux divided by w _* as the temperature unit. Special care has been devoted to the inclusion of the scalar–scalar covariance between the concentrations of O₃ and NO. Sample calculations show that the fluxes of the reactive species deviate significantly from those of non-reactive species. Further, the diffusivities, defined by minus the flux divided by the concentration gradient may become negative for reactive species in contrast to those of non-reactive species, which in the present model are never negative.  相似文献   

Supercooled diopside melt: confirmation of temperature-dependent expansivity using container-based dilatometry     

Joachim Gottsmann  Donald B. Dingwell 《Contributions to Mineralogy and Petrology》2000,139(2):127-135

The expansivity of supercooled diopside liquid has been determined using techniques of container-based dilatometry. Two thermal strategies have been employed, one in which the sample is brought to volumetric equilibrium by long-duration dwells at low temperatures (817 °C) and one in which scanning dilatometry of the sample has been performed at somewhat higher temperatures (890–913 °C). The results of both experiments yield a supercooled liquid expansivity for diopside liquid in the temperature range of 817–913 °C of 84.4 ± 2.8 × 10⁻⁴ cm³/mol K. The expansivity is 65% higher than that obtained for diopside melt obtained at superliquidus temperatures using the double bob Archimedean method. Combined fitting of the new low temperature, volume–temperature data from the present study and the superliquidus data from the literature has been performed. The combined fit yields the following equations for the volume–temperature relationship of diopside liquid (T=temperature in °C): The standard error of the fit using both equations reproduces the volume–temperature data for diopside liquid within experimental error. This result reconciles the disparate values of expansivity measured at low temperatures in the supercooled state and at superliquidus temperatures and confirms the temperature-dependence of the expansivity of diopside liquid. Comparison with previous low temperature estimates of melt volume and expansivity are discussed in light of these new results. Received: 18 November 1999 / Accepted: 24 January 2000  相似文献   

First steps in the enclosure of the oceans: The origins of Truman's proclamation on the resources of the continental shelf, 28 September 1945     

Donald Cameron Watt 《Marine Policy》1979,3(3):211-224

The movement to establish coastalstate jurisdiction over a distance of 200 miles has its origins in President Truman's proclamation of September 1945 on the resources of the continental shelf and ‘certain high seas fisheries’. The author analyses the processes and motives which led to the proclamation, the US justification of its revolutionary policy statements, the reactions of other nations (in particular the warning of the UK and the parallel declaration of Mexico), and the subsequent assessment of the consequences of the action in the USA.  相似文献   

Solar rotation studies using sunspot data (1967–1974)     

Donald F. Neidig 《Solar physics》1980,66(2):205-211

The solar rotation rate during 1967–1974 was measured from photographic observations of sunspots. The rates derived from isolated single spots and from bipolar groups were 14.38 ±0.02 and 14.71±0.05 deg per day equatorial sidereal, respectively. Year-to-year fluctuations in the bipolar group rates correlate with fluctuations in the Mt. Wilson spectroscopic rotation rates, while the isolated single spots show smaller, uncorrelated variations. A possible explanation for the fluctuations in the bipolar rates is year-to-year changes in the separation rates of the bipolar groups, rather than changes in the global solar rotation rate. The latter interpretation requires caution because (1) the sunspot rotation rates were derived from a limited amount of data (one month per year), and (2) the rotation rates were reduced to equatorial values assuming a differential rotation law {ie205-01}.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献