Twisted accretion curtains in the intermediate polar FO Aquarii     

P. A. Evans  Coel Hellier  Gavin Ramsay  Mark Cropper 《Monthly notices of the Royal Astronomical Society》2004,349(2):715-721

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Galileo Photopolarimetry of Jupiter at 678.5 nm     

C.J. BraakJ.F. de Haan  J.W. Hovenier  L.D. Travis 《Icarus》2002,157(2):401-418

Brightness and linear polarization measurements at 678.5 nm for four south-north strips of Jupiter are studied. These measurements were obtained in 1997 by the Galileo photopolarimeter/radiometer. The observed brightness exhibits latitudinal variations consistent with the belt/zone structure of Jupiter. The observed degree of linear polarization is small at low latitudes and increases steeply toward higher latitudes. No clear correlations were observed between the degree of linear polarization and the brightness. The observed direction of polarization changes from approximately parallel to the local scattering plane at low latitudes to perpendicular at higher latitudes. For our studies, we used atmospheric models that include a haze layer above a cloud layer. Parameterized scattering matrices were employed for the haze and cloud particles. On a pixel-wise basis, the haze optical thickness and the single-scattering albedo of the cloud particles were derived from the observed brightness and degree of linear polarization; results were accepted only if they were compatible with the observed direction of polarization. Using atmospheric parameter values obtained from Pioneer 10 and 11 photopolarimetry for the South Tropical Zone and the north component of the South Equatorial Belt, this analysis yielded acceptable results for very few pixels, particularly at small phase angles. However, for almost all pixels, acceptable results were found when the parameterized scattering matrix of the cloud particles was adjusted to produce more negative polarization for single scattering of unpolarized light, especially at large scattering angles, similar to some laboratory measurements of ammonia ice crystals. Using this adjusted model, it was found that the derived latitudinal variation of the single-scattering albedo of the cloud particles is consistent with the belt/zone structure, and that the haze optical thickness steeply increases toward higher latitudes.  相似文献   

Effect of Bioremediation on the Microbial Community in Oiled Mangrove Sediments   总被引：10，自引：0，他引：10  

Michelle A Ramsay  Richard P.J Swannell  Warren A Shipton  Norman C Duke  Russell T Hill   《Marine pollution bulletin》2000,41(7-12):413-419

Bioremediation was conducted in the field on a mature Rhizophora stylosa mangrove stand on land to be reclaimed near Fisherman’s Landing Wharf, Gladstone Australia. Gippsland crude oil was added to six large plots (>40 m²) and three plots were left untreated as controls. Bioremediation was used to treat three oiled plots and the remaining three were maintained as oiled only plots. The bioremediation strategy consisted of actively aerating the sediment and adding a slow-release fertilizer in order to promote oil biodegradation by indigenous micro-organisms. Oil addition stimulated the numbers of alkane-degrading bacteria slightly to levels of 10⁴–10⁵/g sediment. Bioremediation of the oiled sediment had a marked effect on the alkane-degrading population, increasing the population size by three orders of magnitude from 10⁵ to 10⁸ cells/g of sediment. An effect of bioremediation on the growth of aromatic-degraders was detected with numbers of aromatic-degraders increasing from 10⁴ to 10⁶ cells/g of sediment. Active aeration and nutrient addition significantly stimulated the growth of hydrocarbon-degraders in oiled mangrove sediment in the field.  相似文献   

Detection of the optical counterpart of the proposed double degenerate polar RX J1914+24     

Gavin Ramsay  Mark Cropper  Kinwah Wu  K. O. Mason  Pasi Hakala 《Monthly notices of the Royal Astronomical Society》2000,311(1):75-84

We have detected the optical counterpart of the proposed double degenerate polar RX J1914+24. The I -band light curve is modulated on the 9.5-min period seen in X-rays. There is no evidence for any other periods. No significant modulation is seen in J . The infrared colours of RX J1914+24 are not consistent with a main-sequence dwarf secondary star. Our ASCA spectrum of RX J1914+24 is typical of a heavily absorbed polar and our ASCA light curve also shows only the 9.5-min period. We find that the folded I band and X-ray light curves are out of phase. We attribute the I -band flux to the irradiated face of the donor star. The long-term X-ray light curve shows a variation in the observed flux of up to an order of magnitude. These observations strengthen the view that RX J1914+24 is indeed the first double degenerate polar to be detected. In this light, we discuss the synchronizing mechanisms in such a close binary and other system parameters.  相似文献   

Anomalous bathymetry, 3D edge driven convection, and dynamic topography at the western Atlantic passive margin     

Travis Ramsay  Russell Pysklywec 《Journal of Geodynamics》2011,52(1):45-56

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Two-temperature accretion flows in magnetic cataclysmic variables: structures of post-shock emission regions and X-ray spectroscopy     

Curtis J. Saxton  Kinwah Wu  Mark Cropper  Gavin Ramsay 《Monthly notices of the Royal Astronomical Society》2005,360(3):1091-1104

We use a two-temperature hydrodynamical formulation to determine the temperature and density structures of the post-shock accretion flows in magnetic cataclysmic variables (mCVs) and calculate the corresponding X-ray spectra. The effects of two-temperature flows are significant for systems with a massive white dwarf and a strong white-dwarf magnetic field. Our calculations show that two-temperature flows predict harder keV spectra than one-temperature flows for the same white-dwarf mass and magnetic field. This result is insensitive to whether the electrons and ions have equal temperature at the shock, but depends on the electron–ion exchange rate, relative to the rate of radiative loss along the flow. White-dwarf masses obtained by fitting the X-ray spectra of mCVs using hydrodynamic models including the two-temperature effects will be lower than those obtained using single-temperature models. The bias is more severe for systems with a massive white dwarf.  相似文献   

XMM–Newton EPIC observations of Her X-1     

Gavin Ramsay  Silvia Zane  Mario A. Jimenez-Garate  Jan-Willem den Herder  C. J. Hailey 《Monthly notices of the Royal Astronomical Society》2002,337(4):1185-1192

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Coupling thermodynamic modeling and high-resolution in situ LA-ICP-MS monazite geochronology: evidence for Barrovian metamorphism late in the Grenvillian history of southeastern Ontario     

Travis McCarron  Fred Gaidies  Christopher R. M. McFarlane  R. Michael Easton  Peter Jones 《Mineralogy and Petrology》2014,108(6):741-758

The Flinton Group is a greenschist to upper amphibolite facies package of metasediments in southeastern Ontario that was metamorphosed during the Ottawan Orogeny. Thermodynamic modeling of metapelitic mineral assemblages suggests an increase in peak conditions of metamorphism across the 40 km wide study area from 3.5 to 7.9 kbar and 540 to 715 °C. Garnet isopleth thermobarometry applied to the cores of compositionally zoned porphyroblasts reveals remarkably similar P-T conditions of initial crystallization at approximately 3.7–4.0 kbar and 512–520 °C, corresponding to a relatively high geothermal gradient of ca. 34–45 °C km^?1. It is inferred from modeling and reaction textures that metamorphism was along Barrovian P-T paths. Major and trace element zoning in garnet from one sample records a complex growth history as evidenced by major and trace element zoning and the distribution of xenotime, allanite and monazite inclusions. High-resolution (6 μm) LA-ICP-MS U-Pb geochronology performed on monazite in the rock matrix and included in the outer 150 μm of garnet rim-ward of a Y annulus revealed an age of 976?±?4 Ma. The age is interpreted to reflect monazite growth at the expense of allanite and apatite late in garnet’s growth history over the P-T interval 4.5–6.8 kbar and 540–640 °C. This new age estimate for near peak metamorphism fits well into the regional framework but is significantly younger than previously reported ages for Ottawan metamorphism. Based on microstructures this new age suggests that compressional tectonics were operating much later in the history of the Grenville of southeastern Ontario than previously thought.  相似文献   

Evaluation of Long‐Term Performance and Sustained Treatment at Enhanced Anaerobic Bioremediation Sites          下载免费PDF全文

Travis M. McGuire  David. T. Adamson  Michael S. Burcham  Philip B. Bedient  Charles J. Newell 《Ground Water Monitoring & Remediation》2016,36(2):32-44

This study evaluated the long‐term performance of enhanced anaerobic bioremediation (EAB) at chlorinated solvent sites to determine if sustained treatment processes were helping to prevent concentration rebound. A database of groundwater concentration versus time records was compiled for 34 sites, with at least 3 years of posttreatment monitoring data (median = 4.7 years, range = 3.0 to 11.7 years). Long‐term performance was evaluated based on order‐of‐magnitude (OoM) changes in parent compound concentrations during various monitoring periods. Results indicate that, relative to the pretreatment concentration, a median concentration reduction for all 34 sites of 1.0 OoM (90% reduction) was achieved by the end of the posttreatment monitoring period. No rebound was observed at 65% of the sites between the first year of posttreatment monitoring and the final year. During this posttreatment period, Mann‐Kendall trend analysis indicated that the concentration was stable or decreasing at 89% of the sites where a trend could be established (n = 27; 33% decreasing, 56% stable, 11% increasing). Statistical analysis indicates there is no evidence that the distribution of median concentration reductions after the first year of posttreatment monitoring was different than the distribution of median reductions 2 to 11 years later at the end of the monitoring period (p = 0.67). Similarly, statistical analysis indicates that there is no evidence that the distribution of median reductions for a larger set of sites (n = 84) with less than 3 years of posttreatment monitoring data (1.1 OoM; 92% reduction) was different than the distribution of median OoM reductions for the 34‐site dataset with longer monitoring periods (p = 0.80). This suggests that, at a typical site, a 3‐year monitoring period should be sufficient for evaluating performance. The results of this study indicate that, in the long term, after the end of active treatment, sustained treatment processes contribute to relatively modest concentration reductions but do mitigate rebound at the majority of EAB sites.  相似文献   

Managing coastal vulnerability     

Doug Ramsay 《New Zealand geographer》2008,64(2):170-171

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