The effect of shape anisotropy on TRM direction   总被引：1，自引：0，他引：1  

Robert S. Coe 《Geophysical Journal International》1979,56(2):369-383

  相似文献   

A horizontal tectonic regime in the Archaean of Greenland and its implications for early crustal thickening — a comment     

B. Chadwick  K. Coe 《Precambrian Research》1975,2(4):397-400

  相似文献   

Optical follow-up of new Small Magellanic Cloud wing Be/X-ray binaries     

M. P. E. Schurch  M. J. Coe  K. E. McGowan  V. A. McBride  D. A. H. Buckley  J. L. Galache  R. H. D. Corbet  M. Still  P. Vaisanen  A. Kniazev  K. Nordsieck 《Monthly notices of the Royal Astronomical Society》2007,381(4):1561-1568

We investigate the optical counterparts of recently discovered Be/X-ray binaries in the Small Magellanic Cloud (SMC). In total four sources, SXP101, SXP700, SXP348 and SXP65.8 were detected during the Chandra survey of the wing of the SMC. SXP700 and SXP65.8 were previously unknown. Many optical ground-based telescopes have been utilized in the optical follow-up, providing coverage in both the red and blue bands. This has led to the classification of all of the counterparts as Be stars and confirms that three lie within the Galactic spectral distribution of known Be/X-ray binaries. SXP101 lies outside this distribution and is the latest spectral type known. Monitoring of the Hα emission line suggests that all the sources barring SXP700 have highly variable circumstellar discs, possibly a result of their comparatively short orbital periods. Phase-resolved X-ray spectroscopy has also been performed on SXP65.8, revealing that the emission is indeed harder during the passage of the X-ray beam through the line of sight.  相似文献   

The impact of anoxia on pelagic macrofauna during the Toarcian Oceanic Anoxic Event (Early Jurassic)     

Bryony A. Caswell  Angela L. Coe 《Proceedings of the Geologists' Association. Geologists' Association》2014

Extreme environmental change during the Toarcian Oceanic Anoxic Event had widespread impacts on marine biota. This study provides new evidence, from the Yorkshire coast sections, UK, that the event was associated with periods of elevated fish and ammonite mortality. Using a synthesis of pelagic macrofaunal changes, benthic macrofaunal data and geochemical proxies we show that there are stratigraphical correlations between: (1) pelagic macrofaunal ranges and abundance, (2) benthic macrofaunal abundance, and (3) geochemical proxies that indicate deoxygenation. We identify eight stratigraphical intervals of differing character. Results suggest two major phases of relatively persistent deoxygenation with photic zone euxinia. The cyclostratigraphic timescale indicates that each phase lasted at least tens of thousands of years. Belemnite migration during the event probably resulted from increased seawater temperatures and low food supply similar to that observed for many marine taxa, including squid, within the present-day oceans.  相似文献   

X-ray bright sources in the Chandra Small Magellanic Cloud Wing Survey – detection of two new pulsars     

K. E. McGowan  M. J. Coe  M. Schurch  V. A. McBride  J. L. Galache  W. R. T. Edge  R. H. D. Corbet  S. Laycock  A. Udalski  D. A. H. Buckley 《Monthly notices of the Royal Astronomical Society》2007,376(2):759-770

We investigate the X-ray and optical properties of a sample of X-ray bright sources from the Small Magellanic Cloud (SMC) Wing Survey. We have detected two new pulsars with pulse periods of 65.8 s (CXOU J010712.6−723533) and 700 s (CXOU J010206.6−714115), and present observations of two previously known pulsars RX J0057.3−7325 (SXP101) and SAX J0103.2−7209 (SXP348). Our analysis has led to three new optical identifications for the detected pulsars. We find long-term optical periods for two of the pulsars, CXOU J010206.6−714115 and SXP101, of 267 and 21.9 d, respectively. Spectral analysis of a subset of the sample shows that the pulsars have harder spectra than the other sources detected. By employing a quantile-based colour–colour analysis we are able to separate the detected pulsars from the rest of the sample. Using archival catalogues we have been able to identify counterparts for the majority of the sources in our sample. Combining this with our results from the temporal analysis of the Chandra data and archival optical data, the X-ray spectral analysis, and by determining the X-ray to optical flux ratios we present preliminary classifications for the sources. In addition to the four detected pulsars, our sample includes two candidate foreground stars, 12 probable active galactic nuclei, and five unclassified sources.  相似文献   

A study of the long-term variability in radio emission of active galaxies     

M. J. Coe  S. R. Bowring  C. J. Hall  J. B. Stephen 《Astrophysics and Space Science》1983,91(1):35-41

A long-term study of 13 active galaxies has been carried out at 10.7 GHz over the period September 1980 to April 1982. The sources were observed at approximately monthly intervals and most of them were selected because they are also X-ray sources. The data obtained are used to measure their respective variabilities and to search for any correlations with other source parameters. No obvious relationship to radio or X-ray luminosity was found, though there does appear to be two distinct levels of radio variability for these sources and clear evidence of higher X-ray than radio variability.  相似文献   

Source attribution of urban smog episodes caused by coal combustion   总被引：1，自引：0，他引：1  

D. Mira-Salama  C. Grüning  N.R. Jensen  P. Cavalli  J.-P. Putaud  B.R. Larsen  F. Raes  H. Coe 《Atmospheric Research》2008,88(3-4):294-304

Stable weather conditions together with extensive use of coal combustion often lead to severe smog episodes in certain urban environments, especially in Eastern Europe. In order to identify the specific sources that cause the smog episodes in such environments, and to better understand the mixing state and atmospheric processing of aerosols, both single particle and bulk chemical characterization analysis of aerosols were performed in Krakow, Poland, during winter 2005.Real-time measurements of the bulk PM10 aerosol during a severe smog episode (PM10 mass > 400 µg m^− 3) showed a stable concentration of black carbon in the aerosol, and an increase in the sulphate and chlorine mass contributions towards the end of the episode. Chemical characterization of single particles further helped to identify residential coal burning as the main source that caused this severe smog episode, consisting of single particles with major signals for carbon with simultaneous absence of sulphate, chlorine and calcium. Particles from industrial coal combustion gained importance towards the end of that episode, after residential coal combustion was switched off, indicated by an increase of the percentage of sulphate and chlorine containing particles. Traffic was not a significant source during the severe smog episode. During a lighter smog episode, residential and industrial coal combustion was still predominant, with an increased contribution of traffic and processed/aged aerosols. On a clean day, particle classes containing nitrate were the most abundant. In addition, the aerosol was more internally mixed showing that there were more sources contributing to the total aerosol population.  相似文献   

Geomagnetic paleosecular variation at Hawaii around 3 Ma from a sequence of 107 lava flows at Kaena Point (Oahu)     

Carlo Laj  Herv Guillou  Nadia Szeremeta  Robert Coe 《Earth and Planetary Science Letters》1999,170(4):191-376

We have sampled a sequence of 107 lava flows in the Waianae series on Oahu, Hawaii, in two separate stretches. The first (51 flows) at Kaena Point extends from sea level to an altitude of 190 m, and the second (56 flows) follows the Satellite Tracking Station road from 218 m to 360 m above sea level. Thermal and af demagnetization yield very similar results, and reveal only normal polarities. K/Ar dating at five different horizons combined with the paleomagnetic results indicate that the sequence was emplaced entirely in the normal polarity interval between the Upper Mammoth and the Lower Kaena polarity transitions (3.22–3.11 Ma). Some of the flows are serially correlated. Filtering does not, however, drastically affect the final results. Inclinations are shallower than those expected from a centered dipole field. Although large (13°), the inclination anomaly is consistent with results from other sites at the same latitude. The scatter of the VGPs about the geographic pole is consistent with available data from other regions at similar latitudes. The scatter of the directions is also consistent with the predictions of recent statistical models of paleosecular variation. Therefore, these results do not support the hypothesis of a Pacific dipole window.  相似文献   

Magnetostratigraphic correlation of the Oxfordian–Kimmeridgian boundary     

Piotr A. Przybylski  James G. Ogg  Andrzej Wierzbowski  Angela L. Coe  Mark W. Hounslow  John K. Wright  François Atrops  Erik Settles 《Earth and Planetary Science Letters》2010,289(1-2):256-272

A magnetic polarity pattern for Boreal and Sub-Boreal ammonite zones of the Upper Oxfordian to Lower Kimmeridgian was established and confirmed in four British sections, including the proposed Global Boundary Stratotype Section and Point (GSSP) on the Isle of Skye (Scotland) to define the base of the international Kimmeridgian Stage. A coeval pattern for Sub-Mediterranean ammonite zones was compiled from seven sections in Poland, one German section and multi-section composites from France and Spain. The mean paleopole for the European Craton (excluding Spain) at the Oxfordian–Kimmeridgian boundary is 74.2°N, 181.3°E (Α₉₅ = 3.8°). The common magnetic polarity scale enables inter-correlation of ammonite subzones among these three faunal provinces and to the marine magnetic-anomaly M-Sequence. The proposed GSSP at the base of the Pictonia baylei Zone is near the base of an extended interval dominated by reversed polarity, which is interpreted to be Chron M26r. This GSSP level projects to the lower to middle part of the Epipeltoceras bimammatum Subzone, which is the middle subzone of this E. bimammatum Zone in the Sub-Mediterranean standard zonation. In contrast, the traditional placement of the Oxfordian–Kimmeridgian boundary in that Sub-Mediterranean standard zonation (base of Sutneria platynota Zone) is at the base of Chron M25r, or nearly 1 million years younger.  相似文献   

Reconciling discrepant chronologies for the geomagnetic excursion in the Mono Basin,California: Insights from new 40Ar/39Ar dating experiments and a revised relative paleointensity correlation     

William S. Cassata  Brad S. Singer  Joseph C. Liddicoat  Robert S. Coe 《Quaternary Geochronology》2010,5(5):533-543

Lacustrine sediments of the Wilson Creek Formation in the Mono Basin, California, record a paleomagnetic field excursion constrained by ¹⁴C and ⁴⁰Ar/³⁹Ar geochronology to have occurred within the last 50 ka. However, ¹⁴C and ⁴⁰Ar/³⁹Ar ages are discordant, making it difficult to distinguish which of two possible excursions during this period, the Mono Lake or Laschamp, is recorded in the Mono Basin. New ⁴⁰Ar/³⁹Ar age determinations from sanidine, as well as the first biotite and obsidian ages, for three of the nineteen rhyolitic ashes intercalated with these sediments are presented and compared to previous ¹⁴C and ⁴⁰Ar/³⁹Ar data sets. Although the sanidine ages of the three ashes are stratigraphically consistent with each other and previously determined ⁴⁰Ar/³⁹Ar ages for other ashes in the Wilson Creek Formation, each is significantly older than ¹⁴C ages obtained from stratigraphically equivalent beds, relative paleointensity field correlations, oxygen isotope records, and glacial histories. These data indicate an absence of juvenile, eruptive crystals and most likely reflect the incorporation of crystals from older volcanic centers or underlying sediment. We examine the strengths and weaknesses of all available geochronologic data for the section exposed at Wilson Creek to arrive at an internally consistent set of age constraints. Using these constraints we propose two new relative paleointensity correlations for the section, both of which indicate that the excursion recorded in the Mono Basin occurred at ～30–34 ka on the Greenland Ice Sheet Project 2 (GISP2) ice core time scale.  相似文献