The 2dF-SDSS LRG and QSO Survey: the LRG 2-point correlation function and redshift-space distortions     

Nicholas P. Ross  J. da Ângela  T. Shanks  David A. Wake  Russell D. Cannon  A. C. Edge  R. C. Nichol  P. J. Outram  Matthew Colless  Warrick J. Couch  Scott M. Croom  Roberto De Propris  Michael J. Drinkwater  Daniel J. Eisenstein  Jon Loveday  Kevin A. Pimbblet  Isaac G. Roseboom  Donald P. Schneider  Robert G. Sharp  P. M. Weilbacher 《Monthly notices of the Royal Astronomical Society》2007,381(2):573-588

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Evolution of a periglacial landscape in the Late Devensian: environments and palaeobotany of the Mepal area,Cambridgeshire, England     

R. G. West  R. G. O. Burton  R. Andrew  M. E. Pettit 《第四纪科学杂志》2002,17(1):31-50

The landscape evolution of the Mepal area from Late Devensian Block Fen Terrace times to the beginning of the Flandrian, a period of ca. 8000 radiocarbon years, is reconstructed. Stratigraphy is based on borehole transects and single boreholes, centred on a depression between the Block Fen Terrace and the Isle of Ely. Within the depression is a Devensian late‐glacial sequence, with the Windermere Interstadial represented by radiocarbon‐dated organic sediments. Pollen and plant macroscopic remains of the late‐glacial sediments are analysed. Plant communities with Betula developed in the interstadial. Before and after the interstadial there is much reworked pollen in the inorganic sediments, derived from local pre‐Devensian Pleistocene sediments, including temperate Ipswichian Stage sediments, and from mass‐wasting of the local Jurassic bedrock. Periods of such mass‐movement occur before and after the deposition of the late‐glacial lake sediments. Deposition of aeolian sediment occurs later than the main period of mass movement, but before the Windermere Interstadial. The relationship of the aeolian sediments in time and space to permafrost, indicated by local contraction polygons and cracks, is discussed. Solifluction diverted the flow of the River Great Ouse from a northeast direction in Block Fen Terrace times to a southwest direction as a channel developed to the west of the Chatteris–March ‘island’. This led to a drainage divide in Flandrian times. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

The Ratio Method of Estimating Water Resistivity and TDS from Resistivity Logs     

Donald G. Jorgensen 《Ground water》1996,34(3):519-522

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Chandra and his students at Yerkes Observatory     

Donald E. Osterbrock 《Journal of Astrophysics and Astronomy》1996,17(3-4):233-268

S. Chandrasekhar’s interactions with graduate students in his more than a quarter century at Yerkes Observatory are described. His graduate teaching, Ph.D. thesis students, colloquia and colloquium series, and seminar series were all important aspects of this side of his scientific research career. His managing editorship ofThe Astrophysical Journal, his one experience in observational astrophysics, a second paper he wrote describing some of the early observational work at Yerkes Observatory, and a third on “the case for astronomy” are all discussed. A famous myth about one of his courses is corrected, and the circumstances under which the “S. Candlestickmaker” parody was written are recounted. Chandra’s computers, recruited in the Williams Bay community, are mentioned. A complete or nearly complete table of all the thesis students who received their Ph.D. degrees under his supervision, at Yerkes and on the campus in Chicago up through his last one in Astronomy and Astrophysics in 1973, is presented, with references to their published thesis papers.  相似文献   

Brachinites: Igneous rocks from a differentiated asteroid     

David W. Mittlefehldt  Donald D. Bogard  John L. Berkley  Daniel H. Garrison 《Meteoritics & planetary science》2003,38(11):1601-1625

Abstract— We have done petrologic studies of brachinites Allan Hills (ALH) 84025, Elephant Moraine (EET) 99402, and EET 99407; bulk geochemical studies of EET 99402 and EET 99407; Ar‐Ar studies of Brachina and EET 99402; and a Xe isotopic study of Brachina. Textural, mineral compositional, and bulk compositional evidence show that EET 99402 and EET 99407 are paired. ALH 84025, EET 99402, and EET 99407 have igneous textures. Petrofabric analyses of ALH 84025 and EET 99407 demonstrate the presence of lineations and probable foliations of olivine grains that support formation as igneous cumulates. Mineral minor element chemistry and bulk rock incompatible lithophile element contents of the brachinites are distinct from those of acapulcoitelodranite clan meteorites, a suite of high‐grade metamorphic rocks and anatectic residues. The differences demonstrate a higher blocking temperature of equilibration for the brachinites and that cumulus plagioclase is present in EET 99402, EET 99407, and probably ALH 84025, thus indicating an igneous origin. Brachinites are differentiated, ultramafic achondrites, and are not part of a suite of primitive achondrites. We infer that their parent asteroid is a differentiated body. Brachina has an excess of ¹²⁹Xe correlated with reactor‐produced ¹²⁸Xe, demonstrating that short‐lived ¹²⁹I was present at the time of formation. This, plus literature data, attests to early formation of the brachinites, within a few Ma of the formation of chondrites. Ar‐Ar age data show that Brachina and EET 99407 were degassed about 4.13 Ga ago, possibly by a common impact event. EET 99402 and EET 99407 show petrographic evidence for shock, including possible conversion of plagioclase to maskelynite followed by devitrification. Brachina is unshocked, making a direct association between the Ar‐Ar age and textures ambiguous.  相似文献   

Improving Cascadia subduction zone residents’ tsunami preparedness: quasi-experimental evaluation of an evacuation brochure     

Lindell  Michael K.  Jung  Meen Chel  Prater  Carla S.  House  Donald H. 《Natural Hazards》2022,114(1):849-881

Natural Hazards - This study surveyed 227 residents in three US Pacific Coast communities that are vulnerable to a Cascadia subduction zone tsunami. In the Brochure condition, information was...  相似文献   

Land Use and Salinity Drive Changes in SAV Abundance and Community Composition     

Christopher J. Patrick  Donald E. Weller  Robert J. Orth  David J. Wilcox  Michael P. Hannam 《Estuaries and Coasts》2018,41(1):85-100

Conserving and restoring submerged aquatic vegetation (SAV) are key management goals for estuaries worldwide because SAV integrates many aspects of water quality and provides a wide range of ecosystem services. Management strategies are typically focused on aggregated abundance of several SAV species, because species cannot be easily distinguished in remotely sensed data. Human land use and shoreline alteration have been shown to negatively impact SAV abundance, but the effects have varied with study, spatial scale, and location. The differences in reported effects may be partly due to the focus on abundance, which overlooks within-community and among-community dynamics that generate total SAV abundance. We analyzed long-term SAV aerial survey data (1984–2009) and ground observations of community composition (1984–2012) in subestuaries of Chesapeake Bay to integrate variations in abundance with differences in community composition. We identified five communities (mixed freshwater, milfoil-Zannichellia, mixed mesohaline, Zannichellia, and Ruppia-Zostera). Temporal variations in SAV abundance were more strongly related to community identity than to terrestrial stressors, and responses to stressors differed among communities and among species. In one fifth of the subestuaries, the community identity changed during the study, and the probability of such a change was positively related to the prevalence of riprapped shoreline in the subestuary. Mixed freshwater communities had the highest rates of recovery, and this may have been driven by Hydrilla verticillata, which was the single best predictor of SAV recovery rate. Additional species-specific and community-specific research will likely yield better understanding of the factors affecting community identity and SAV abundance, more accurate predictive models, and more effective management strategies.  相似文献   

Effects of Local Watershed Land Use on Water Quality in Mid-Atlantic Coastal Bays and Subestuaries of the Chesapeake Bay     

Thomas E. Jordan  Donald E. Weller  Carey E. Pelc 《Estuaries and Coasts》2018,41(1):38-53

Nutrient inputs have degraded estuaries worldwide. We investigated the sources and effects of nutrient inputs by comparing water quality at shallow (< 2m deep) nearshore (within 200 m) locations in a total of 49 Chesapeake subestuaries and Mid-Atlantic coastal bays with differing local watershed land use. During July–October, concentrations of total nitrogen (TN), dissolved ammonium, dissolved inorganic N (DIN), and chlorophyll a were positively correlated with the percentages of cropland and developed land in the local watersheds. TN, DIN, and nitrate were positively correlated with the ratio of watershed area to subestuary area. Total phosphorus (TP) and dissolved phosphate increased with cropland but were not affected by developed land. The relationships among N, P, chlorophyll a, and land use suggest N limitation of chlorophyll a production from July–October. We compared our measurements inside the subestuaries to measurements by the Chesapeake Bay Program in adjacent estuarine waters outside the subestuaries. TP and dissolved inorganic P concentrations inside the subestuaries correlated with concentrations outside the subestuaries. However, water quality inside the subestuaries generally differed from that in adjacent estuarine waters. The concentration of nitrate was lower inside the subestuaries, while the concentrations of other forms of N, TP, and chlorophyll a were higher. This suggests that shallow nearshore waters inside the subestuaries import nitrate while exporting other forms of N as well as TP and chlorophyll a. The importance of local land use and the distinct biogeochemistry of shallow waters should be considered in managing coastal systems.  相似文献   

Impacts of Coastal Land Use and Shoreline Armoring on Estuarine Ecosystems: an Introduction to a Special Issue     

Diann J. Prosser  Thomas E. Jordan  Jessica L. Nagel  Rochelle D. Seitz  Donald E. Weller  Dennis F. Whigham 《Estuaries and Coasts》2018,41(1):2-18

The nearshore land-water interface is an important ecological zone that faces anthropogenic pressure from development in coastal regions throughout the world. Coastal waters and estuaries like Chesapeake Bay receive and process land discharges loaded with anthropogenic nutrients and other pollutants that cause eutrophication, hypoxia, and other damage to shallow-water ecosystems. In addition, shorelines are increasingly armored with bulkhead (seawall), riprap, and other structures to protect human infrastructure against the threats of sea-level rise, storm surge, and erosion. Armoring can further influence estuarine and nearshore marine ecosystem functions by degrading water quality, spreading invasive species, and destroying ecologically valuable habitat. These detrimental effects on ecosystem function have ramifications for ecologically and economically important flora and fauna. This special issue of Estuaries and Coasts explores the interacting effects of coastal land use and shoreline armoring on estuarine and coastal marine ecosystems. The majority of papers focus on the Chesapeake Bay region, USA, where 50 major tributaries and an extensive watershed (~ 167,000 km²), provide an ideal model to examine the impacts of human activities at scales ranging from the local shoreline to the entire watershed. The papers consider the influence of watershed land use and natural versus armored shorelines on ecosystem properties and processes as well as on key natural resources.  相似文献   

Ion Implants as Matrix‐Appropriate Calibrators for Geochemical Ion Probe Analyses          下载免费PDF全文

Donald S. Burnett  Amy J.G. Jurewicz  Dorothy S. Woolum  Jianhua Wang  Julie M. Paque  Larry R. Nittler  Kevin D. McKeegan  Munir Humayun  Richard Hervig  Veronika S. Heber  Yunbin Guan 《Geostandards and Geoanalytical Research》2015,39(3):265-276

Ion microprobe elemental and isotopic determinations can be precise but difficult to quantify. Error is introduced when the reference material and the sample to be analysed have different compositions. Mitigation of such ‘matrix effects’ is possible using ion implants. If a compositionally homogeneous reference material is available which is ‘matrix‐appropriate’ (i.e., close in major element composition to the sample to be analysed, but having an unknown concentration of the element, E, to be determined) then ion implantation can be used to introduce a known amount of an E isotope, calibrating the E concentration and producing a matrix‐appropriate calibrator. Nominal implant fluences (ions cm^?2) are inaccurate by amounts up to approximately 30%. However, ion implantation gives uniform fluences over large areas; thus, it is possible to ‘co‐implant’ an additional reference material of any bulk composition having known amounts of E, independently calibrating the implant fluence. Isotope ratio measurement standards can be produced by implanting two different isotopes, but permil level precision requires postimplant calibration of the implant isotopic ratio. Examples discussed include (a) standardising Li in melilite; (b) calibrating a ²⁵Mg implant fluence using NIST SRM 617 glass and (c) using Si co‐implanted with ²⁵Mg alongside NIST SRM 617 to produce a calibrated measurement of Mg in Si.  相似文献