Galaxy groups in the 2dF Galaxy Redshift Survey: the number density of groups     

V. R. Eke  Carlton M. Baugh  Shaun Cole  Carlos S. Frenk  Julio F. Navarro † 《Monthly notices of the Royal Astronomical Society》2006,370(3):1147-1158

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Substructure analysis of selected low-richness 2dFGRS clusters of galaxies     

William S. Burgett  Michael M. Vick  David S. Davis  Matthew Colless  Roberto De Propris  Ivan Baldry  Carlton Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Chris Collins  Warrick Couch  Nicholas Cross  Gavin Dalton  Simon Driver  George Efstathiou  Richard Ellis  Carlos S. Frenk  Karl Glazebrook  Edward Hawkins  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  John A. Peacock  Will Percival  Bruce Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,352(2):605-654

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The properties of spiral galaxies: confronting hierarchical galaxy formation models with observations     

Eric F. Bell  Carlton M. Baugh  Shaun Cole  Carlos S. Frenk  Cedric G. Lacey 《Monthly notices of the Royal Astronomical Society》2003,343(2):367-384

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A latest Pleistocene and Holocene glacial history and paleoclimate reconstruction at Three Sisters and Broken Top Volcanoes, Oregon, U.S.A.     

Shaun A. Marcott  Andrew G. Fountain  Peter J. Sniffen 《Quaternary Research》2009,71(2):181-189

At least three sets of moraines mark distinct glacial stands since the last glacial maximum (LGM) in the Three Sisters region of the Oregon Cascade Range. The oldest stand predates 8.1 ka (defined here as post-LGM), followed by a second between ∼ 2 and 8 ka (Neoglacial) and a third from the Little Ice Age (LIA) advance of the last 300 years. The post-LGM equilibrium line altitudes were 260 ± 100 m lower than that of modern glaciers, requiring 23 ± 9% increased winter snowfall and 1.4 ± 0.5°C cooler summer temperatures than at present. The LIA advance had equilibrium line altitudes 110 ± 40 m lower than at present, implying 10 ± 4% greater winter snowfall and 0.6 ± 0.2°C cooler summer temperatures.  相似文献   

The Evolution of Sunspot Magnetic Fields Associated with a Solar Flare     

Sophie A. Murray  D. Shaun Bloomfield  Peter T. Gallagher 《Solar physics》2012,277(1):45-57

Solar flares occur due to the sudden release of energy stored in active-region magnetic fields. To date, the precursors to flaring are still not fully understood, although there is evidence that flaring is related to changes in the topology or complexity of an active-region’s magnetic field. Here, the evolution of the magnetic field in active region NOAA 10953 was examined using Hinode/SOT-SP data over a period of 12 hours leading up to and after a GOES B1.0 flare. A number of magnetic-field properties and low-order aspects of magnetic-field topology were extracted from two flux regions that exhibited increased Ca ii H emission during the flare. Pre-flare increases in vertical field strength, vertical current density, and inclination angle of ≈ 8° toward the vertical were observed in flux elements surrounding the primary sunspot. The vertical field strength and current density subsequently decreased in the post-flare state, with the inclination becoming more horizontal by ≈ 7°. This behavior of the field vector may provide a physical basis for future flare-forecasting efforts.  相似文献   

The statistical properties of Λ cold dark matter halo formation     

Shaun Cole  John Helly  Carlos S. Frenk  Hannah Parkinson 《Monthly notices of the Royal Astronomical Society》2008,383(2):546-556

We present a comparison of the statistical properties of dark matter halo merger trees extracted from the Millennium Simulation with Extended Press–Schechter (EPS) formalism and the related galform Monte Carlo method for generating ensembles of merger trees. The volume, mass resolution and output frequency make the Millennium Simulation a unique resource for the study of the hierarchical growth of structure. We construct the merger trees of present-day friends-of-friends groups and calculate a variety of statistics that quantify the masses of their progenitors as a function of redshift, accretion rates, and the redshift distribution of their most recent major merger. We also look in the forward direction and quantify the present-day mass distribution of haloes into which high-redshift progenitors of a specific mass become incorporated. We find that the EPS formalism and its Monte Carlo extension capture the qualitative behaviour of all these statistics, but as redshift increases they systematically underestimate the masses of the most massive progenitors. This shortcoming is worst for the Monte Carlo algorithm. We present a fitting function to a scaled version of the progenitor mass distribution and show how it can be used to make more accurate predictions of both progenitor and final halo mass distributions.  相似文献   

New Lines: Critical GIS and the Trouble of the Map by Matthew W. Wilson University of Minnesota Press,Minneapolis, MN, 2017, 224 pp. $25.00 (paper), ISBN 978‐0‐8166‐9853‐0; $100.00 (cloth), ISBN 978‐0‐81669852‐3     

Chen‐Chieh Feng  Shaun Lin  James D. Sidaway 《Transactions in GIS》2019,23(1):158-161

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Compound‐Specific Isotope Analyses to Assess TCE Biodegradation in a Fractured Dolomitic Aquifer          下载免费PDF全文

Randy L. Stotler  Shaun K. Frape  Walter A. Illman 《Ground water》2017,55(1):88-99

The potential for trichloroethene (TCE) biodegradation in a fractured dolomite aquifer at a former chemical disposal site in Smithville, Ontario, Canada, is assessed using chemical analysis and TCE and cis‐DCE compound‐specific isotope analysis of carbon and chlorine collected over a 16‐month period. Groundwater redox conditions change from suboxic to much more reducing environments within and around the plume, indicating that oxidation of organic contaminants and degradation products is occurring at the study site. TCE and cis‐DCE were observed in 13 of 14 wells sampled. VC, ethene, and/or ethane were also observed in ten wells, indicating that partial/full dechlorination has occurred. Chlorine isotopic values (δ³⁷Cl) range between 1.39 to 4.69‰ SMOC for TCE, and 3.57 to 13.86‰ SMOC for cis‐DCE. Carbon isotopic values range between ?28.9 and ?20.7‰ VPDB for TCE, and ?26.5 and ?11.8‰ VPDB for cis‐DCE. In most wells, isotopic values remained steady over the 15‐month study. Isotopic enrichment from TCE to cis‐DCE varied between 0 and 13‰ for carbon and 1 and 4‰ for chlorine. Calculated chlorine‐carbon isotopic enrichment ratios (?_Cl/?_C) were 0.18 for TCE and 0.69 for cis‐DCE. Combined, isotopic and chemical data indicate very little dechlorination is occurring near the source zone, but suggest bacterially mediated degradation is occurring closer to the edges of the plume.  相似文献   

Solar Flare Prediction Using Advanced Feature Extraction, Machine Learning, and Feature Selection   总被引：2，自引：0，他引：2  

Omar W. Ahmed  Rami Qahwaji  Tufan Colak  Paul A. Higgins  Peter T. Gallagher  D. Shaun Bloomfield 《Solar physics》2013,283(1):157-175

Novel machine-learning and feature-selection algorithms have been developed to study: i) the flare-prediction-capability of magnetic feature (MF) properties generated by the recently developed Solar Monitor Active Region Tracker (SMART); ii) SMART’s MF properties that are most significantly related to flare occurrence. Spatiotemporal association algorithms are developed to associate MFs with flares from April 1996 to December 2010 in order to differentiate flaring and non-flaring MFs and enable the application of machine-learning and feature-selection algorithms. A machine-learning algorithm is applied to the associated datasets to determine the flare-prediction-capability of all 21 SMART MF properties. The prediction performance is assessed using standard forecast-verification measures and compared with the prediction measures of one of the standard technologies for flare-prediction that is also based on machine-learning: Automated Solar Activity Prediction (ASAP). The comparison shows that the combination of SMART MFs with machine-learning has the potential to achieve more accurate flare-prediction than ASAP. Feature-selection algorithms are then applied to determine the MF properties that are most related to flare occurrence. It is found that a reduced set of six MF properties can achieve a similar degree of prediction accuracy as the full set of 21 SMART MF properties.  相似文献   

Clues from Current High CO2 Environments on the Effects of Ocean Acidification on CaCO3 Preservation     

Andreas J. Andersson  Nicholas R. Bates  Marlene A. Jeffries  Kyra Freeman  Charles Davidson  Shaun Stringer  Evan Betzler  Fred T. Mackenzie 《Aquatic Geochemistry》2013,19(5-6):353-369

Acidification of surface seawater owing to anthropogenic activities has raised serious concerns on its consequences for marine calcifying organisms and ecosystems. To acquire knowledge concerning the future consequences of ocean acidification (OA), researchers have relied on incubation experiments with organisms exposed to future seawater conditions, numerical models, evidence from the geological record, and recently, observations from aquatic environments exposed to naturally high CO₂ and low pH, e.g., owing to volcanic CO₂ vents, upwelling, and groundwater input. In the present study, we briefly evaluate the distribution of dissolved CO₂–carbonic acid parameters at (1) two locations in the Pacific and the Atlantic Ocean as a function of depth, (2) a mangrove environment in Bermuda, (3) a seasonally stratified body of water in a semi-enclosed sound in Bermuda, and (4) in temporarily isolated tide pools in Southern California. We demonstrate that current in situ conditions of seawater pCO₂, pH, and CaCO₃ saturation state (Ω) in these environments are similar or even exceed the anticipated changes to these parameters in the open ocean over the next century as a result of OA. The observed differences between the Pacific and Atlantic Oceans with respect to seawater CO₂–carbonic acid chemistry, preservation of CaCO₃ minerals, and the occurrence and distribution of deep-sea marine calcifiers, support the hypothesized negative effects of OA on the production and preservation of CaCO₃ in surface seawater. Clues provided from shallow near-shore environments in Bermuda and Southern California support these predictions, but also highlight that many marine calcifiers already experience relatively high seawater pCO₂ and low pH conditions.  相似文献