Submillimetre photometry of X-ray absorbed quasi-stellar objects: their formation and evolutionary status     

J. A. Stevens  M. J. Page  R. J. Ivison  F. J. Carrera  J. P. D. Mittaz  Ian Smail  I. M. MHardy 《Monthly notices of the Royal Astronomical Society》2005,360(2):610-618

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A submillimetre imaging polarimeter at the James Clerk Maxwell Telescope     

J. S. Greaves  W. S. Holland  T. Jenness  A. Chrysostomou  D. S. Berry  A. G. Murray  M. Tamura  E. I. Robson  P. A. R. Ade  R. Nartallo  J. A. Stevens  M. Momose  J.-I. Morino  G. Moriarty-Schieven  F. Gannaway  C. V. Haynes 《Monthly notices of the Royal Astronomical Society》2003,340(2):353-361

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The nature of X-ray selected extremely red objects     

J. A. Stevens  M. J. Page  R. J. Ivison  Ian Smail  I. Lehmann  G. Hasinger  G. Szokoly 《Monthly notices of the Royal Astronomical Society》2003,342(1):249-258

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Discovery of a precessing jet nozzle in BL Lacertae     

A. M. Stirling  T. V. Cawthorne  J. A. Stevens  S. G. Jorstad  A. P. Marscher  M. L. Lister  J. L. Gómez  P. S. Smith  I. Agudo  D. C. Gabuzda  E. I. Robson  W. K. Gear 《Monthly notices of the Royal Astronomical Society》2003,341(2):405-422

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Theoretical X-ray line profiles from colliding wind binaries   总被引：1，自引：0，他引：1  

David B. Henley  Ian R. Stevens  Julian M. Pittard 《Monthly notices of the Royal Astronomical Society》2003,346(3):773-786

We present theoretical X-ray line profiles from a range of model colliding wind systems. In particular, we investigate the effects of varying the stellar mass-loss rates, the wind speeds and the viewing orientation. We find that a wide range of theoretical line profile shapes is possible, varying with orbital inclination and phase. At or near conjunction, the lines have approximately Gaussian profiles, with small widths  (HWHM ∼ 0.1 v _∞)  and definite blueshifts or redshifts (depending on whether the star with the weaker wind is in front or behind). When the system is viewed at quadrature, the lines are generally much broader  (HWHM ∼ v _∞)  , flat-topped and unshifted. Local absorption can have a major effect on the observed profiles – in systems with mass-loss rates of a few times  10⁻⁶ M_⊙ yr⁻¹  the lower energy lines  ( E  ≲ 1 keV)  are particularly affected. This generally results in blueward-skewed profiles, especially when the system is viewed through the dense wind of the primary. The orbital variation of the linewidths and shifts is reduced in a low-inclination binary. The extreme case is a binary with   i = 0°  , for which we would expect no line profile variation.  相似文献   

The Northern HIPASS catalogue – data presentation, completeness and reliability measures     

O. I. Wong  E. V. Ryan-Weber  D. A. Garcia-Appadoo  R. L. Webster  L. Staveley-Smith  M. A. Zwaan  M. J. Meyer  D. G. Barnes  V. A. Kilborn  R. Bhathal  W. J. G. de Blok  M. J. Disney  M. T. Doyle  M. J. Drinkwater  R. D. Ekers  K. C. Freeman  B. K. Gibson  S. Gurovich  J. Harnett  P. A. Henning  H. Jerjen  M. J. Kesteven  P. M. Knezek  B. S. Koribalski  S. Mader  M. Marquarding  R. F. Minchin  J. O'Brien  M. E. Putman  S. D. Ryder  E. M. Sadler  J. Stevens  I. M. Stewart  F. Stootman  M. Waugh 《Monthly notices of the Royal Astronomical Society》2006,371(4):1855-1864

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Using aquaplanets to understand the robust responses of comprehensive climate models to forcing   总被引：1，自引：0，他引：1  

Brian Medeiros  Bjorn Stevens  Sandrine Bony 《Climate Dynamics》2015,44(7-8):1957-1977

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Late Pleistocene loess‐palaeosol sequences in the Vojvodina region,north Serbia     

Slobodan B. Marković  Mark P. Bokhorst  Jef Vandenberghe  William D. McCoy  Eric A. Oches  Urlich Hambach  Tivadar Gaudenyi  Mladjen Jovanović  Ludwig Zöller  Thomas Stevens  Björn Machalett 《第四纪科学杂志》2008,23(1):73-84

Late Pleistocene loess‐palaeosol sequences are widespread in the Vojvodina region, with thicknesses reaching a maximum of about 20 m. Our investigations include more than 40 of these loess sections. Geochronology of the last glacial loess‐palaeosol sequences, based on luminescence dating and amino acid racemisation, provides correlations between Upper Pleistocene loess‐palaeosol sediments in Vojvodina and comparable deposits at other European localities. Sedimentary logs of magnetic susceptibility, grain‐size measurements and carbonate content, combined with malacological evidence, indicate two main relatively cold and arid phases during the last glacial period, related to intensive accumulation of loess units L1L1 and L1L2, as well as many brief episodes of dry and windy climatic conditions, suggesting a possible relationship with cold events recorded in the North Atlantic region. Generally, late Pleistocene climate in the region was dry and relatively warm, compared with glacial period sites in central Europe, and was characterised by sharp differences between glacial and interglacial modes. New data and interpretations presented in this study emphasise the significance of loess‐palaeosol sequences in Vojvodina for the reconstruction of the temporal and spatial evolution of late Pleistocene palaeoclimate in this part of Europe. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Nonlinear features in wave-resolving microwave radar observationsof ocean waves     

Stevens  C.L. Poulter  E.M. Smith  M.J. McGregor  J.A. 《Oceanic Engineering, IEEE Journal of》1999,24(4):470-480

Transformation of sea-surface Doppler microwave backscatter observations from the space-time domain to the wavenumber-frequency domain separates linear wave energy from nonlinear effects. Here observations and modeling are used to investigate the sources of these nonlinearities. Wave breaking and electromagnetic shadowing are examined with emphasis on their relative effects both inside and outside the region of the wavenumber-frequency spectrum associated with the linear dispersion equation. Shadowing significantly reduces the variance levels within the linear spectral region. In addition, shadowing is less directly related to changes in variance outside this region, i.e., that region associated with nonlinearity in the wave field. Wave breaking has less of an effect on the variance within the linear region than shadowing. However, the modeled wave breaking does have a greater tendency to increase variance levels at frequencies less than that of the linear wave field, for any given wavenumber. Aliasing and emphasis of crest backscatter are also explored to explain features seen in some wavenumber-frequency intensity images. Two-dimensional data allow the linear wave spectrum to be separated from nonlinear effects. This results in improved wave height spectrum estimation  相似文献   

Testing the influence of topography and material properties on catchment‐scale soil moisture patterns using remotely sensed vegetation patterns in a humid temperate catchment,northern Britain     

David Graham Milledge  Jeff Warburton  Stuart N. Lane  Carly J. Stevens 《水文研究》2013,27(8):1223-1237

In order to evaluate the relationship between the apparent complexity of hillslope soil moisture and the emergent patterns of catchment hydrological behaviour and water quality, we need fine‐resolution catchment‐wide data on soil moisture characteristics. This study proposes a methodology whereby vegetation patterns obtained from high‐resolution orthorectified aerial photographs are used as an indicator of soil moisture characteristics. This enables us to examine a set of hypotheses regarding what drives the spatial patterns of soil moisture at the catchment scale (material properties or topography). We find that the pattern of Juncus effusus vegetation is controlled largely by topography and mediated by the catchment's material properties. Characterizing topography using the topographic index adds value to the soil moisture predictions relative to slope or upslope contributing area (UCA). However, these predictions depart from the observed soil moisture patterns at very steep slopes or low UCAs. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献