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  • 1
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    Paleomagnetism and biostratigraphy of sediments from Southern Ocean ODP Site 744 (southern Kerguelen Plateau): Implications for early-to-middle Miocene climate in Antarctica (2014)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: New paleomagnetic results from lower-to-middle Miocene samples from Ocean Drilling Program (ODP) Holes 744A and 744B, cored during ODP Leg 119 on the southern Kerguelen Plateau (Indian Ocean sector; Southern Ocean), provide a chronostratigraphic framework for an existing and under-utilized paleoclimate archive during a key period of Antarctic climate and ice sheet evolution. Site 744 is strategically positioned for high-latitude paleoceanographic and paleoclimatic studies because it lies within the southern domain of the Antarctic Circumpolar Current (ACC) and in proximity to the large and active Lambert Glacier-Amery Ice Shelf drainage system of the East Antarctic Ice Sheet. Magnetostratigraphic results were reported previously for this site, but technical difficulties and limited sampling prevented confident correlation of the magnetic polarity record with the geomagnetic polarity timescale. Our results, which are constrained by new semi-quantitative analyses of diatom assemblages and radiolarian first and last appearance events that are evaluated within a regional Southern Ocean biostratigraphic dataset through Constrained Optimization (CONOP) model runs, permit significant refinement of previous age models for the lower-to-middle Miocene sequence recovered at Site 744 (spanning the interval from ~ 21 to 13.7 Ma). An extended record of sediment accumulation, with average sedimentation rates of ~ 0.7–0.9 cm/kyr, is interrupted by a series of hiatuses in the middle Miocene. These disruptions in sediment supply, or erosional events, could mark a local response of north–south fluctuations in the location and/or strength of the Antarctic Circumpolar Current during transient glacial events within the Mid-Miocene Climate Optimum (MMCO; ~ 17 to 14.45 Ma). With the enhanced age control provided by this study, combined with a refined chronostratigraphy for the underlying upper Eocene to Oligocene strata, Site 744 becomes a good candidate for future high-resolution stable isotope and microfossil paleoecological work, which will further elucidate the late Paleogene and early Neogene paleoenvironmental history of the Southern Ocean.
    Description: Published
    Description: 434 – 454
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Antarctica ; Paleoclimate ; Miocene ; Diatom biostratigraphy ; Paleomagnetism ; CONOP ; 03. Hydrosphere::03.01. General::03.01.06. Paleoceanography and paleoclimatology ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Field reconnaissance geologic mapping of the Columbia Hills, Mars, based on Mars Exploration Rover Spirit and MRO HiRISE observations (2011)
    Wiley
    Details
    Publication Date: 2011-07-07
    Description: Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in terrain units mapped using orbital Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (MRO HiRISE) image data. Examination of several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic units may be identified and correlated across significant areas on the ground, and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread epiclastic materials, mobile fines, and fall deposits, the selective exhumation of deep and well-preserved geologic units has exposed undisturbed outcrops, stratigraphic sections, and structural information much as they are preserved and exposed on Earth. A rich geologic record awaits skilled future field investigators on Mars. The correlation of ground observations and orbital images enables construction of a corresponding geologic reconnaissance map. Most of the outcrops visited are interpreted to be pyroclastic, impactite, and epiclastic deposits overlying an unexposed substrate, probably related to a modified Gusev crater central peak. Fluids have altered chemistry and mineralogy of these protoliths in degrees that vary substantially within the same map unit. Examination of the rocks exposed above and below the major unconformity between the plains lavas and the Columbia Hills directly confirms the general conclusion from remote sensing in previous studies over past years that the early history of Mars was a time of more intense deposition and modification of the surface. Although the availability of fluids and the chemical and mineral activity declined from this early period, significant later volcanism and fluid convection enabled additional, if localized, chemical activity.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Late Holocene Sea-Level Variability and Atlantic Meridional Overturning Circulation (2014)
    Wiley
    Details
    Publication Date: 2014-06-03
    Description: Pre-20th century sea-level (SL) variability remains poorly understood due to limits of tide gauge records, low temporal resolution of tidal marsh records, and regional anomalies caused by dynamic ocean processes, notably multidecadal changes in Atlantic Meridional Overturning Circulation (AMOC). We examined SL and AMOC variability along the eastern United States over the last 2000 years, using a SL curve constructed from proxy SST records from Chesapeake Bay, and 20 th century SL-sea-surface temperature (SST) relations derived from tide gauges and instrumental SST. The SL curve shows multidecadal-scale variability (20–30 yr) during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA), as well as the 20 th century. During these SL oscillations, short-term rates ranged from 2 to 4 mm yr −1 , roughly similar to those of the last few decades. These oscillations likely represent internal modes of climate variability related to AMOC variability and originating at high latitudes, although the exact mechanisms remain unclear. Results imply that dynamic ocean changes, in addition to thermosteric, glacio-eustatic or glacio-isostatic processes are an inherent part of SL variability in coastal regions, even during millennial-scale climate oscillations such as the MCA and LIA, and should be factored into efforts that use tide gauges and tidal marsh sediments to understand global sea-level rise.
    Print ISSN: 0883-8305
    Electronic ISSN: 1944-9186
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    The true stellar parameters of the Kepler target list (2013)
    Oxford University Press
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    Publication Date: 2013-07-04
    Description: Using population synthesis tools we create a synthetic Kepler Input Catalogue (KIC) and subject it to the Kepler Stellar Classification Program (SCP) method for determining stellar parameters such as the effective temperature T eff and surface gravity g . We achieve a satisfactory match between the synthetic KIC and the real KIC in the log g versus log T eff diagram, while there is a significant difference between the actual physical stellar parameters and those derived by the SCP of the stars in the synthetic sample. We find a median difference T eff  = +500 K and ~log g  = –0.2 dex for main-sequence (MS) stars, and ~ T eff  = +50 K and log g  = –0.5 dex for giants, although there is a large variation across parameter space. For a MS star the median difference in g would equate to a ~3 per cent increase in stellar radius and a consequent ~3 per cent overestimate of the radius for any transiting exoplanet. We find no significant difference between T eff and log g for single stars and the primary star in a binary system. We also re-created the Kepler target selection method and found that the binary fraction is unchanged by the target selection. Binaries are selected in similar proportions to single star systems; the fraction of MS dwarfs in the sample increases from about 75 to 80 per cent, and the giant star fraction decreases from 25 to 20 per cent.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    PROSPECTS FOR DETECTING ASTEROSEISMIC BINARIES IN KEPLER DATA (2014)
    Institute of Physics
    Details
    Publication Date: 2014-03-04
    Print ISSN: 2041-8205
    Electronic ISSN: 2041-8213
    Topics: Physics
    Published by Institute of Physics
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  • 6
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    The true stellar parameters of the Kepler target list (2013)
    Oxford University Press
    Details
    Publication Date: 2013-06-03
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
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  • 7
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    An overview of forest management and change with respect to environmental protection in the UK (2004)
    Copernicus
    Details
    Publication Date: 2004-06-30
    Description: This paper overviews changes in forest management in the UK with respect to environmental protection. The evolution of policy is explained from historical and sustainability perspectives and covers developments in forest planning, accreditation, devolution and future challenges and opportunities. Keywords: forest management, best practice, sustainable forestry, environmental protection, land use change
    Print ISSN: 1027-5606
    Electronic ISSN: 1607-7938
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
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    A Design Tool for Liquid Rocket Engine Injectors (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A practical design tool which emphasizes the analysis of flowfields near the injector face of liquid rocket engines has been developed and used to simulate preliminary configurations of NASA's Fastrac and vortex engines. This computational design tool is sufficiently detailed to predict the interactive effects of injector element impingement angles and points and the momenta of the individual orifice flows and the combusting flow which results. In order to simulate a significant number of individual orifices, a homogeneous computational fluid dynamics model was developed. To describe sub- and supercritical liquid and vapor flows, the model utilized thermal and caloric equations of state which were valid over a wide range of pressures and temperatures. The model was constructed such that the local quality of the flow was determined directly. Since both the Fastrac and vortex engines utilize RP-1/LOX propellants, a simplified hydrocarbon combustion model was devised in order to accomplish three-dimensional, multiphase flow simulations. Such a model does not identify drops or their distribution, but it does allow the recirculating flow along the injector face and into the acoustic cavity and the film coolant flow to be accurately predicted.
    Keywords: Spacecraft Propulsion and Power
    Type: Joint Propulsion; Jul 17, 2000 - Jul 19, 2000; Huntsville, AL; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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