Re-analysis of polarization in the γ-ray flux of GRB 021206     

Robert E. Rutledge  Derek B. Fox 《Monthly notices of the Royal Astronomical Society》2004,350(4):1288-1300

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Search for millisecond periodicities in type I X-ray bursts of the Rapid Burster     

D. W. Fox  W. H. G. Lewin  R. E. Rutledge  E. H. Morgan  R. Guerriero  L. Bildsten  M. van der Klis  J. van Paradijs  †  C. B. Moore  T. Dotani  K. Asai 《Monthly notices of the Royal Astronomical Society》2001,321(4):776-782

We have searched the rising portion of type I X-ray bursts observed from the Rapid Burster with the Rossi X-ray Timing Explorer for the presence of periodicities. The 95 per cent confidence upper limit on the average rms variation of near coherent pulsations with a width of ≲1 Hz (in 60–2048 Hz) during the first second of the bursts is <8.8 per cent. We find a possible detection (>98 per cent significance) at 306.5 Hz.  相似文献   

The theoretical polarisation from the obliquely rotating envelopes of single stars     

G. K. Fox 《Astrophysics and Space Science》1992,187(2):219-239

The polarimetric variability of stars possessing an obliquely rotating envelope is investigated in the optically thin, single electron scattering approximation. It is shown that in the point light source treatment, one is unable to distinguish between polarimetric variability occurring due to rotation about a body axis and (binary) orbital motion. Nor is it possible, from the polarimetric variability, to infer the physical geometry of the obliquely rotating envelope.It is shown that polarimetric discrimination between envelope geometries is possible (to some extent) when the light source is considered to be finite in extent, due to the possible occultation of some of the scatteres, resulting in polarimetric variability that cannot be explained by the canonical point light source models.In this paper, we consider, as illustrative examples of the effects of scatterer occultation, two diametrically opposite spots and an obliquely rotating, near planar, disc. Finally, an account is made of the spectroscopic variability of the two geometries considered, which again indicate that geometry discrimination is possible.  相似文献   

The environments of hyperluminous infrared galaxies at 0.44 < z < 1.55     

D. Farrah  J. Geach  M. Fox  S. Serjeant  S. Oliver  A. Verma  A. Kaviani  M. Rowan-Robinson 《Monthly notices of the Royal Astronomical Society》2004,349(2):518-526

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Submillimetre observations of the Hubble Deep Field and Flanking Fields     

S. Serjeant  J. S. Dunlop  R. G. Mann  M. Rowan-Robinson  D. Hughes  A. Efstathiou  A. Blain  M. Fox  R. J. Ivison  T. Jenness  A. Lawrence  M. Longair  S. Oliver  J. A. Peacock 《Monthly notices of the Royal Astronomical Society》2003,344(3):887-904

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High-Resolution Integrated Transport Model for Studying Surface Water–Groundwater Interaction     

Tabea Broecker  Vahid Sobhi Gollo  Aryeh Fox  Jörg Lewandowski  Gunnar Nützmann  Shai Arnon  Reinhard Hinkelmann 《Ground water》2021,59(4):488-502

Transport processes that lead to exchange of mass between surface water and groundwater play a significant role for the ecological functioning of aquatic systems, for hydrological processes and for biogeochemical transformations. In this study, we present a novel integral modeling approach for flow and transport at the sediment–water interface. The model allows us to simultaneously simulate turbulent surface and subsurface flow and transport with the same conceptual approach. For this purpose, a conservative transport equation was implemented to an existing approach that uses an extended version of the Navier–Stokes equations. Based on previous flume studies which investigated the spreading of a dye tracer under neutral, losing and gaining flow conditions the new solver is validated. Tracer distributions of the experiments are in close agreement with the simulations. The simulated flow paths are significantly affected by in- and outflowing groundwater flow. The highest velocities within the sediment are found for losing condition, which leads to shorter residence times compared to neutral and gaining conditions. The largest extent of the hyporheic exchange flow is observed under neutral condition. The new solver can be used for further examinations of cases that are not suitable for the conventional coupled models, for example, if Reynolds numbers are larger than 10. Moreover, results gained with the integral solver provide high-resolution information on pressure and velocity distributions at the rippled streambed, which can be used to improve flow predictions. This includes the extent of hyporheic exchange under varying ambient groundwater flow conditions.  相似文献   

Leaching evaluation of cement stabilisation / solidification treated kaolin clay     

U.E. John  I. Jefferson  D.I. Boardman  G.S. Ghataora  C.D. Hills 《Engineering Geology》2011,(4):315

Sustainable land management often requires redevelopment of existing and often contaminated Brownfield sites over use of Greenfield or agricultural land. Stabilisation / solidification (S/S) offer a viable remediation option with particular suitability in treating heavy metal contaminants. However, uncertainties over long-term durability and previously cheap landfill disposal costs resulted in limited use in many countries. There is a need to characterise treated material and assess components containment and release, to improve S/S confidence and inform remedial design, using the evaluation of the leaching controlling mechanisms. To improve understanding of key features that will enable improvements to such designs, this paper presents an evaluation of leaching for CEM II stabilised kaolin, using the leaching behaviour of 4 main components—aluminium, silicon, calcium and sulphur. Results show no detrimental implications on chemical durability due to kaolin degradation with hydration under induced alkalinity, with increased formation of stable cementitious minerals. Availabilities for components show that aluminium and silicon had minimal leachability compared to total content, whilst calcium and sulphur show almost total leaching availability. Decreasing calcium and silicon leachability under natural chemical conditions with increased hydration duration supports the increased formation of stable cementitious products with time, using the products of kaolin dissociation.  相似文献   

Recent progress on geologic time ontologies and considerations for future works   总被引：2，自引：1，他引：1  

Xiaogang Ma  Peter Fox 《Earth Science Informatics》2013,6(1):31-46

Semantic Web technologies bring innovative ideas to computer applications in geoscience. As an essential part of the Semantic Web, ontologies are increasingly discussed in the geoscience community, in which geologic time scale is one of the topics that have received the most discussion and practices. This paper aims to carry out a review of the recent progress on geologic time ontologies, discuss further improvements, and make recommendations for other geoscience ontology works. Several models and ontologies of geologic time scale are collected and analyzed. Items such as ontology evaluation, ontology mapping, ontology governance, ontology delivery and multilingual labels are discussed for advancing the geologic time ontologies. We hope the discussion can be useful for other geoscience ontology works, and we also make a few further recommendations, such as referring to an ontology spectrum in ontology creation, collaborative working to improve interoperability, and balancing expressivity, implementability and maintainability to achieve better applications of ontologies.  相似文献   

Mt. Suhora M dwarf survey - Detection of eight short-period variable stars     

L. Fox Machado  A.S. Baran  M. WiniarskiJ. Krzesiński  M. Dró?dz 《New Astronomy》2012,17(2):65-72

The Mt. Suhora M dwarf survey searching for pulsations in low mass main sequence stars has acquired CCD photometry of 46 M dwarf stars during the first year of the project (Baran et al., 2011). As a by-product of this search hundreds field stars have been checked for variability. This paper presents our initial result of a search for periodic variables in field stars observed in the course of the survey. On the basis of the periodicity and the shape of the light curves, eight new variables has been detected, among which five are δ Scuti stars and three likely RR Lyrae stars. Although variation in one of the stars has been previously detected, it was classified incorrectly. To support our classification, in August 2010, we performed spectroscopic observations to derive spectral types and luminosity classes for all eight variable stars.  相似文献   

Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range,USA     

A. Jefferson  S.L. Lewis  S.T. Lancaster 《地球表面变化过程与地形》2010,35(7):803-816

Young basalt terrains offer an exceptional opportunity to study landscape and hydrologic evolution through time, since the age of the landscape itself can be determined by dating lava flows. These constructional terrains are also highly permeable, allowing one to examine timescales and process of geomorphic evolution as they relate to the partitioning of hydrologic flowpaths between surface and sub‐surface flow. The western slopes of the Cascade Range in Oregon, USA are composed of a thick sequence of lava flows ranging from Holocene to Oligocene in age, and the landscape receives abundant precipitation of between 2000 and 3500 mm per year. On Holocene and late Pleistocene lava landscapes, groundwater systems transmit most of the recharge to large springs (≥0·85 m³ s^?1) with very steady hydrographs. In watersheds >1 million years old, springs are absent, and well‐developed drainage networks fed by shallow subsurface stormflow produce flashy hydrographs. Drainage density slowly increases with time in this basalt landscape, requiring a million years to double in density. Progressive hillslope steepening and fluvial incision also occur on this timescale. Springs and groundwater‐fed streams transport little sediment and hence are largely ineffective in incising river valleys, so fluvial landscape dissection appears to occur only after springs are replaced by shallow subsurface stormflow as the dominant streamflow generation mechanism. It is proposed that landscape evolution in basalt terrains is constrained by the time required for permeability to be reduced sufficiently for surface flow to replace groundwater flow. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献