Metallic particles in astronomy     

F. Hoyle  N. C. Wickramasinghe 《Astrophysics and Space Science》1988,147(2):245-256

We discuss some implications of iron whiskers condensing in supernova ejecta and being expelled into interstellar and intergalactic space. The supposition that the universal microwave background is a relic from an early hot state of the Universe is shown to be not as secure as is commonly supposed.  相似文献   

Distances to Cepheid open clusters via optical and K-band imaging     

Fiona Hoyle  Tom Shanks  N. R. Tanvir 《Monthly notices of the Royal Astronomical Society》2003,345(1):269-291

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Future dark energy constraints from measurements of quasar parallax: Gaia, SIM and beyond     

Fiona Ding  Rupert A. C. Croft 《Monthly notices of the Royal Astronomical Society》2009,397(4):1739-1747

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An Integrated 2.5–12.5 μm Emission Spectrum of Naturally-Occurring Aromatic Molecules     

N.C. Wickramasinghe  F. Hoyle  T. Al-Jubory 《Astrophysics and Space Science》1999,268(1-3):317-320

The expected emission features from an ensemble of naturally-occurring aromatic molecules is shown to be in satisfactory agreement with the emission properties of `PAH molecules' associated with planetary nebulae. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The Astonishing Redness of Kuiper-Belt Objects     

N.C. Wickramasinghe  F. Hoyle 《Astrophysics and Space Science》1999,268(1-3):369-372

The recently reported extreme redness of a class of Kuiper-belt objects could be yet another indirect indication of extraterrestrial microbiology in the outer solar system. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The Case Against Graphite Particles in Interstellar Space     

N.C. Wickramasinghe  A.N. Wickramasinghe  F. Hoyle 《Astrophysics and Space Science》1999,268(1-3):289-292

Graphite flakes are excluded as a major component of interstellar grains because their ultraviolet extinction peaks occur at wavelengths longward of 2700 Å. Mie calculations for spherical graphite particles are shown to have no physical or astronomical relevance.  相似文献   

Primitive Grain Clumps and Organic Compounds in Carbonaceous Chondrites     

F. Hoyle  N.C. Wickramasinghe 《Astrophysics and Space Science》1999,268(1-3):129-132

Refractory interstellar grains acquire tarry polymeric coatings in dense protostellar molecular clouds. Collisions between polymer-coated grains lead to the formation of micron sized grain clumps that are subsequently expelled into the diffuse interstellar medium. Such grains could contain the building blocks of life such as amino acids in their interiors protected from dissociative ultraviolet radiation. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A Unified Model for The 3.28 μ Emission and The 2200 Å Interstellar Extinction Feature     

F. Hoyle  N.C. Wickramasinghe 《Astrophysics and Space Science》1999,268(1-3):305-310

The 3.28 μm feature observed in the diffuse galactic emission and the 2200 Å interstellar extinction feature must have a common source. This requirement rules out graphitic-type PAH molecules such as coronone and tends to favour naturally occurring bi-cyclic ring structures typified by quinoline and its derivatives.  相似文献   

Ice fracturing during jökulhlaups: implications for englacial floodwater routing and outlet development     

Matthew J. Roberts  Andrew J. Russell  Fiona S. Tweed   skar Knudsen 《地球表面变化过程与地形》2000,25(13):1429-1446

Theoretical studies of glacial outburst floods (jökulhlaups) assume that: (i) intraglacial floodwater is transported efficiently in isolated conduits; (ii) intraglacial conduit enlargement operates proportionally to increasing discharge; (iii) floodwater exits glaciers through pre‐existing ice‐marginal outlets; and (iv) the morphology and positioning of outlets remains fixed during flooding. Direct field observations, together with historical jökulhlaup accounts, confirm that these theoretical assumptions are not always correct. This paper presents new evidence for spatial and temporal changes in intraglacial floodwater routing during jökulhlaups; secondly, it identifies and explains the mechanisms controlling the position and morphology of supraglacial jökulhlaup outlets; and finally, it presents a conceptual model of the controls on supraglacial outbursts. Field observations are presented from two Icelandic glaciers, Skeiðarárjökull and Sólheimajökull. Video footage and aerial photographs, taken before, during and after the Skeiðarárjökull jökulhlaup and immediately after the Sólheimajökull jökulhlaup, reveal changes in floodwater routing and the positioning and morphology of outlets. Field observations confirm that glaciers cannot transmit floodwater as efficiently as previously assumed. Rapid increases in jökulhlaup discharge generate basal hydraulic pressures in excess of ice overburden. Under these circumstances, floodwater can be forced through the surface of glaciers, leading to the development of a range of supraglacial outlets. The rate of increase in hydraulic pressure strongly influences the type of supraglacial outlet that can develop. Steady increases in basal hydraulic pressure can retro‐feed pre‐existing englacial drainage, whereas transient increases in pressure can generate hydraulic fracturing. The position and morphology of supraglacial outlets provide important controls on the spatial and temporal impact of flooding. The development of supraglacial jökulhlaup outlets provides a new mechanism for rapid englacial debris entrainment. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Climatic signals in lacustrine deposits of the Upper Yacoraite Formation,Western Argentina: Evidence from clay minerals,analcime, dolomite and fibrous calcite     

João Paulo B. Gomes  Rodrigo B. Bunevich  Sandra N. Tonietto  Daisy B. Alves  Julice F. Santos  Fiona F. Whitaker 《Sedimentology》2020,67(5):2282-2309

Authigenic clays are an important control on reservoir quality in lacustrine carbonates but remain challenging to predict. Lacustrine depositional systems respond to climatic variations in rainfall, surface runoff and groundwater input, and evaporation, and result in rapid and frequent changes in lake volume; this is expressed through changing water depth and shoreline position. In the upper portion of the Early Palaeocene Yacoraite Formation of the Salta Basin in Argentina, extensive lacustrine deposits were deposited during the sag phase of rifting. Prior high-resolution stratigraphic studies have suggested that climatic factors control microbial carbonate sequences within a ‘balanced fill’ lake, with variation in the lake level having a major influence on facies association changes. This study characterizes the evolution of facies and mineralogy within the Yacoraite Formation, focusing on the distribution of clay minerals, making a link between the high, medium and low-frequency sequence stratigraphic cycles. The low-frequency transgressive hemicycle of the upper portion of the Yacoraite Formation is comprised of abundant siliciclastic facies, suggesting a wetter period. Microbialites occurring in this interval are coarse-grained and agglutinated. Detrital clay minerals such as illite and chlorite and associated siliciclastic sediments were input to the lake during high-frequency transgressive periods. During high-frequency regressive hemicycles, sedimentation was dominated by carbonate facies with Ca-rich dolomite and the authigenic clays are comprised of chlorite/smectite mixed-layers. By contrast, the low frequency regressive hemicycle records fine-grained agglutinated microbialite with horizons of fibrous calcite, more stoichiometric dolomite, barite and authigenic magnesian smectite. This indicates elevated ion concentrations in the lake under intense evaporation during an arid period. Understanding the conditions that are favourable for formation and preservation of authigenic clays within the lacustrine environment can improve understanding of reservoir quality in comparable economically important deposits.  相似文献