An analysis and comparison of observed Pleistocene South Carolina (USA) shoreline elevations with predicted elevations derived from Marine Oxygen Isotope Stages     

William Richardson Doar III  Christopher George St. Clement Kendall 《Quaternary Research》2014

Geological maps of South Carolina, covering > 6800 km², confirm the existence of eight preserved Pleistocene shorelines above current sea level: Marietta (+ 42.6 m), Wicomico (+ 27.4 m), Penholoway (+ 21.3 m), Ladson (+ 17.4 m), Ten Mile Hill (+ 10.7 m), Pamlico (+ 6.7 m), Princess Anne (+ 5.2 m), and Silver Bluff (+ 3 m). Current geochronologic data suggest that these eight shorelines correlate with Marine Oxygen Isotope Stages (MIS) as follows: Marietta—older than MIS 77; Wicomico—MIS 55–45; Penholoway—MIS 19 or 17; Ladson—MIS 11; Ten Mile Hill—MIS 7; Pamlico—MIS 5; Princess Anne—MIS 5; and Silver Bluff—MIS 5 or 3. Except for the MIS 5e Pamlico, and possibly the MIS 11 Ladson, the South Carolina elevations are higher than predicted by isotope proxy-based reconstructions. The < 4 m of total relief from the Pamlico to the Silver Bluff shoreline in South Carolina, for which other reconstructions suggest an expected relief of ~ 80 m, illustrates the lack of match. Our results suggest that processes affecting either post-depositional changes in shoreline elevations or the creation of proxy sea-level estimates must be considered before using paleo sea-level position on continental margins.  相似文献   

Observations on the crystal structures of lueshite     

Roger H. Mitchell  Peter C. Burns  Kevin S. Knight  Christopher J. Howard  Anton R. Chakhmouradian 《Physics and Chemistry of Minerals》2014,41(6):393-401

Laboratory powder XRD patterns of the perovskite-group mineral lueshite from the type locality (Lueshe, Kivu, DRC) and pure NaNbO₃ demonstrate that lueshite does not adopt the same space group (Pbma; #57) as the synthetic compound. The crystal structures of lueshite (2 samples) from Lueshe, Mont Saint-Hilaire (Quebec, Canada) and Sallanlatvi (Kola, Russia) have been determined by single-crystal CCD X-ray diffraction. These room temperature X-ray data for all single-crystal samples can be satisfactorily refined in the orthorhombic space group Pbnm (#62). Cell dimensions, atomic coordinates of the atoms, bond lengths and octahedron tilt angles are given for four crystals. Conventional neutron diffraction patterns for Lueshe lueshite recorded over the temperature range 11–1,000 K confirm that lueshite does not adopt space group Pbma within these temperatures. Neutron diffraction indicates no phase changes on cooling from room temperature to 11 K. None of these neutron diffraction data give satisfactorily refinements but suggest that this is the space group Pbnm. Time-of-flight neutron diffraction patterns for Lueshe lueshite recorded from room temperature to 700 °C demonstrate phase transitions above 550 °C from Cmcm through P4/mbm to \(Pm\overline{3} m\) above 650 °C. Cell dimensions and atomic coordinates of the atoms are given for the three high-temperature phases. The room temperature to 400 °C structures cannot be satisfactorily resolved, and it is suggested that the lueshite at room temperature consists of domains of pinned metastable phases with orthorhombic and/or monoclinic structures. However, the sequence of high-temperature phase transitions observed is similar to those determined for synthetic NaTaO₃, suggesting that the equilibrated room temperature structure of lueshite is orthorhombic Pbnm.  相似文献   

Geoarchaeology,Climate Change,and Sustainability. Antony G. Brown,Laura S. Basell,and Karl W. Butzer (Eds.). 2011. Special Paper 476. Geological Society of America,Boulder, CO. 194 pp., ISBN: 978‐0‐8137‐2476‐8, $80 (paperback).     

Christopher L. Hill 《Geoarchaeology》2014,29(2):175-177

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A Comprehensive Framework for Intrinsic OpenStreetMap Quality Analysis   总被引：5，自引：2，他引：3  

Christopher Barron  Pascal Neis  Alexander Zipf 《Transactions in GIS》2014,18(6):877-895

OpenStreetMap (OSM) is one of the most popular examples of a Volunteered Geographic Information (VGI) project. In the past years it has become a serious alternative source for geodata. Since the quality of OSM data can vary strongly, different aspects have been investigated in several scientific studies. In most cases the data is compared with commercial or administrative datasets which, however, are not always accessible due to the lack of availability, contradictory licensing restrictions or high procurement costs. In this investigation a framework containing more than 25 methods and indicators is presented, allowing OSM quality assessments based solely on the data's history. Without the usage of a reference data set, approximate statements on OSM data quality are possible. For this purpose existing methods are taken up, developed further, and integrated into an extensible open source framework. This enables arbitrarily repeatable intrinsic OSM quality analyses for any part of the world.  相似文献   

Fragmentation of massive protostellar discs     

Kaitlin M. Kratter  Christopher D. Matzner 《Monthly notices of the Royal Astronomical Society》2006,373(4):1563-1576

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The frequency of explosive volcanic eruptions in Southeast Asia     

Patrick L. Whelley  Christopher G. Newhall  Kyle E. Bradley 《Bulletin of Volcanology》2015,77(1):1-11

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A 24 h investigation of the hydrogeochemistry of baseflow and stormwater in an urban area impacted by mining: Butte,Montana     

Christopher H. Gammons  Christopher L. Shope  Terence E. Duaime 《水文研究》2005,19(14):2737-2753

Changes in water quality during a storm event were continuously monitored over a 24 h period at a single location along an urban stormwater drain in Butte, Montana. The Butte Metro Storm Drain (MSD) collects groundwater baseflow and stormwater draining Butte Hill, a densely populated site that has been severely impacted by 130 years of mining, milling, and smelting of copper‐rich, polymetallic mineral deposits. On the afternoon of 26 June 2002, a heavy thunderstorm caused streamflow in the MSD to increase 100‐fold, from 0·2 ft³ s⁻¹ to more than 20 ft³ s⁻¹. Hourly discharge and water quality data were collected before, during, and following the storm. The most significant finding was that the calculated loads (grams per hour) of both dissolved and particulate copper passing down the MSD increased more than 100‐fold in the first hour following the storm, and remained elevated over baseline conditions for the remainder of the study period. Other metals, such as zinc, cadmium, and manganese, showed a decrease in load from pre‐storm to post‐storm conditions. In addition to the large flush of copper, loads of soluble phosphorus increased during the storm, whereas dissolved oxygen dropped to low levels (<2 mg l⁻¹). These results show that infrequent storm events in Butte have the potential to generate large volumes of runoff that exceed Montana water quality standards for acute exposure of aquatic life to copper, as well as depressed levels of dissolved oxygen. This study has important implications to ongoing reclamation activities in the upper Clark Fork Superfund site, particularly with respect to management of storm flow, and may be applicable to other watersheds impacted by mining activities. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

A computationally efficient Doppler compensation system forunderwater acoustic communications     

Sharif  B.S. Neasham  J. Hinton  O.R. Adams  A.E. 《Oceanic Engineering, IEEE Journal of》2000,25(1):52-61

A Doppler compensation system is presented which is suitable for high-data-rate acoustic communication between rapidly moving platforms such as autonomous underwater vehicles. The proposed approach provides a generic preprocessor to conventional adaptive receiver structures with only a marginal increase in computational load and hardware cost. The preprocessor employs a novel Doppler estimation technique and efficient sample rate conversion to remove Doppler shift induced by platform velocity and acceleration. Performance predicted by simulation is compared to that of sea trials of a prototype communication system in the North Sea. Successful communication is demonstrated at 16 kbit/s with a transmitting platform moving at up to ±2.6 m/s  相似文献   

Mid-infrared polarisation and inferred magnetic field direction toward YSOs with outflow     

Christopher M. Wright 《Astrophysics and Space Science》2007,311(1-3):47-55

The position angle of mid-infrared polarisation can be directly related to the magnetic field direction projected onto the plane of the sky. Such observations, from both ground and space-based platforms, have been used to investigate the relation between the magnetic field and other “symmetry axes” associated with embedded young stars, such as the interstellar magnetic field, bipolar outflow and disk/toroid axes. Interpretation of the results in terms of hydromagnetic driving mechanisms of bipolar outflow is discussed.  相似文献   

Performances of multi-element multi-user detection strategies in ashallow-water acoustic network (SWAN)     

Hong Kwang Yeo Sharif  B.S. Adams  A.E. Hinton  O.R. 《Oceanic Engineering, IEEE Journal of》2001,26(4):604-611

A multi-element receiver strategy is proposed in this paper for a multi-user shallow-water acoustic network (SWAN). The base station receiver, equipped with prior knowledge of the synchronization and training sequences of all intended users, has the task of demodulating the received signals of each user independent of the presence of other users. The adopted receiver strategy enables robust communications through the challenging underwater environment which is limited by both environmental and system factors. The channel is characterized by inter-symbol interference due to multipath propagation and multiple access interference. In this paper, we propose a number of multi-user detection receiver structures employing adaptive decision feedback equalization and spatial diversity to mitigate the effect of these two types of interference. Computer simulations and experimental sea trials conducted in the North Sea in 1999 were used to test the receiver strategies' performance for a two user near far scenario. Amongst a number of strategies tested, the structure based on recursive successive interference cancellation demonstrated improved performance overall  相似文献