Micromorphological analysis of poly‐phase deformation associated with the transport and emplacement of glaciotectonic rafts at West Runton,north Norfolk,UK     

David P. Vaughan‐Hirsch  Emrys Phillips  Jonathan R. Lee  Jane K. Hart 《Boreas: An International Journal of Quaternary Research》2013,42(2):376-394

The ability of glaciers to detach and transport bedrock as glaciotectonic rafts is widely observed throughout Quaternary sections. However, the glaciological, hydrological and geological parameters controlling rafting are currently poorly constrained. There is a lack of structural and sedimentary evidence concerning rafting, and therefore the processes driving raft detachment, transport and emplacement are poorly understood. This paper contributes to our understanding by presenting a macro‐ and microstructural study of deformation associated with a chalk raft at West Runton, north Norfolk. Detailed thin‐section analysis reveals several discrete micro‐fabric orientations, representing poly‐phase deformation occurring during raft transport and emplacement. A four‐stage conceptual model for raft transport and emplacement is proposed, with deformation being partitioned into the relatively weaker Happisburgh Till member, the latter forming the host to the raft. Stage 1 is the main transport phase of the chalk raft, and was dominated by easterly (down‐ice) directed ductile shearing. During Stage 2 a narrow ductile shear zone within the Happisburgh Till member propagated upwards through the base of the raft, leading to the detachment of an elongate block of chalk. Attenuated lenses of diamicton in this shear zone possess kinematics recording an easterly directed sense of shear. As deformation progressed, during Stage 3, the detached block impinged on the ‘high‐strain’ zone wrapping the base of the raft, influencing the style of deformation partitioning and leading to localized, up‐ice‐directed kinematics. Stage 4 represents the final stages of raft emplacement, when the detachment zone at the base of the raft began to ‘lock‐up’. These results demonstrate the relative importance of the hydrological controls associated with raft transport and emplacement underneath an actively advancing glacier. Furthermore, the model represents an example of how micromorphological analysis can reveal detailed poly‐phase deformation histories in deformed glacial sediments.  相似文献   

A pilot study of the radio‐continuum emission from MASH planetary nebulae     

I.S. Boji i&#x;  Q.A. Parker  D.J. Frew  A.E. Vaughan  M.D. Filipovi&#x;  M.L.P. Gunawardhana 《Astronomische Nachrichten》2011,332(7):697-705

We report an Australia Telescope Compact Array (ATCA) radio‐continuum observations of 26 planetary nebulae (PNe) at wavelengths of 3 and 6 cm. This sample of 26 PNe were taken from the Macquarie/AAO/Strasbourg Hα PNe (MASH) catalogue and previous lists. We investigate radio detection quality including measured and derived parameters for all detected or marginally detected PNe from this combined sample. Some 11 objects from the observed sample have been successfully detected and parametrized. Except for one, all detected PNe have very low radio surface brightnesses. We use a statistical distance scale method to calculate distances and ionised masses of the detected objects. Nebulae from this sample are found tobe large (>0.2 pc in diameter) and highly diluted which indicates old age. For 21 PNe from this sample we list integrated Hα fluxes and interstellar extinction coefficients, either taken from the literature or derived here from the Balmer decrement and radio to Hα ratio methods. Finally, our detected fraction of the MASH pilot sample is relatively low compared to the non‐MASH sub‐sample. We conclude that future radio surveys of the MASH sample must involve deeper observations with better uv coverage in order to increase the fraction of detected objects and improve the quality of the derived parameters (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Photometric correction of Mercury's global color mosaic     

Deborah L. Domingue  Scott L. Murchie  Brett W. Denevi  Nancy L. Chabot  David T. Blewett  Nori R. Laslo  Robin M. Vaughan  Hong K. Kang  Michael K. Shepard 《Planetary and Space Science》2011,59(15):1873-1887

During the third flyby of Mercury by the MESSENGER spacecraft, a dedicated disk-integrated photometric sequence was acquired with the wide-angle multispectral camera to observe Mercury's global photometric behavior in 11 spectral filters over as broad a range of phase angle as possible within the geometric constraints of the flyby. Extraction of disk-integrated measurements from images acquired during this sequence required careful accounting for scattered light and residual background effects. The photometric model fit to these measurements is shown to fit observed radiances at phase angles below 110°, possibly except where both solar incidence and emission angles are high (>70°). The complexity of the scattered light at wavelengths greater than 828 nm contributes to a less accurate photometric correction at these wavelengths. The model is used to correct the global imaging data set acquired at a variety of geometries to a common geometry of incidence angle=30°, emission angle=0°, and phase angle=30°, yielding a relatively seamless mosaic. The results here will be used to correct image mosaics of Mercury acquired in orbit.  相似文献   

Absolute photometry of small main-belt asteroids in 2007–2009     

V. Chiorny  A. Galád  P. Pravec  P. Kušnirák  K. Hornoch  Š. Gajdoš  L. Kornoš  J. Világi  M. Husárik  Z. Kaňuchová  Z. Krišandová  D. Higgins  D.P. Pray  R. Durkee  R. Dyvig  V. Reddy  J. Oey  F. Marchis  R.D. Stephens 《Planetary and Space Science》2011,59(13):1482-1489

We present the results of absolute photometry – the absolute brightness H_V, the effective diameter, (B)VR color indices, composite light curves, period of rotation and amplitude of variations – of several small asteroids in the inner main-belt: 1344 Caubeta, 1401 Lavonne, 2947 Kippenhahn, 3913 Chemin, 3956 Caspar, 4375 Kiyomori, 4555 1987 QL, 5484 Inoda, 5985 1942 RJ, 6949 Zissell and main-belt asteroid 6867 Kuwano. The photometric observations of these objects were made in the period 2007–2009 as part of a project of photometric studies of small main-belt asteroids that involves a collaboration of a number of asteroid photometrists around the world.  相似文献   

Non-linear X-ray variability in X-ray binaries and active galaxies   总被引：2，自引：0，他引：2  

P. Uttley  I. M. MHardy  S. Vaughan 《Monthly notices of the Royal Astronomical Society》2005,359(1):345-362

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On characterizing the variability properties of X-ray light curves from active galaxies     

S. Vaughan  R. Edelson  R. S. Warwick  P. Uttley 《Monthly notices of the Royal Astronomical Society》2003,345(4):1271-1284

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Messing with nature? Exploring public perceptions of geoengineering in the UK     

Adam Corner  Karen Parkhill  Nick Pidgeon  Naomi E. Vaughan 《Global Environmental Change》2013,23(5):938-947

Anthropogenic influence on the climate – and possible societal responses to it – offers a unique window through which to examine the way people think about and relate to the natural world. This paper reports data from four, one-day deliberative workshops conducted with members of the UK public during early 2012. The workshops focused on geoengineering – the deliberate, large-scale manipulation of the planetary environment – as one of three possible responses to climate change (alongside mitigation and adaptation). Here, we explore one of the most pervasive and wide-ranging themes to emerge from the workshops: whether geoengineering represented an unprecedented human intervention into ‘nature’, and what the moral consequences of this might be. Using the concept of ‘messing with nature’ as an analytical lens, we explore public perceptions of geoengineering. We also reflect on why ‘messing with nature’ was such a focal point for debate and disagreement, and whether the prospect of geoengineering may reveal new dimensions to the way that people think about the natural world, and their relationship to it.  相似文献   

X-ray and optical variability of Seyfert 1 galaxies as observed with XMM–Newton     

R. Smith  S. Vaughan 《Monthly notices of the Royal Astronomical Society》2007,375(4):1479-1487

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The Cascadia megathrust earthquake of 1700 may have rejuvenated an isolated basalt volcano in western Canada: Age and petrographic evidence     

Michael D. Higgins 《Journal of Volcanology and Geothermal Research》2009,179(1-2):149-156

The basaltic Tseax flow is the product of one of only two eruptions in western Canada during the last thousand years. Reinterpretations of ¹⁴C and paleomagnetic data indicate that Tseax volcano last erupted between 1668 and 1714 CE. This date straddles that of the Cascadia megathrust earthquake of 26 January 1700, whose rupture lay 450 km to the south. Hence, the largest recent earthquake in northwest North America may have rejuvenated an existing magmatic system and produced this isolated flow. Although the flow is chemically uniform there are significant textural differences between the early and late parts of the flow. It is proposed that both magmatic components were contained within a steep conduit. Gas produced by degassing of magma in the lower part of the conduit ascended, heated magma in the upper part, coarsening plagioclase, and then continued to the surface along fissures. This stable configuration was disrupted by the Cascadia earthquake: dilatation widened the conduit and enabled both magmas to rise to the surface along existing fissures.  相似文献   

Rapid X-Ray Variability of Seyfert 1 Galaxies     

S. Vaughan  A. C. Fabian  K. Iwasawa 《Astrophysics and Space Science》2005,300(1-3):119-125

The rapid and seemingly random fluctuations in X-ray luminosity of Seyfert galaxies provided early support for the standard model in which Seyferts are powered by a supermassive black hole fed from an accretion disc. However, since EXOSAT there has been little opportunity to advance our understanding of the most rapid X-ray variability. Observations with XMM-Newton have changed this. We discuss some recent results obtained from XMM-Newton observations of Seyfert 1 galaxies. Particular attention will be given to the remarkable similarity found between the timing properties of Seyferts and black hole X-ray binaries, including the power spectrum and the cross spectrum (time delays and coherence), and their implications for the physical processes at work in Seyferts.  相似文献