Strong observational constraints on advection-dominated accretion in the cores of elliptical galaxies     

T. Di Matteo †  A. C. Fabian  M. J. Rees  C. L. Carilli  R. J. Ivison 《Monthly notices of the Royal Astronomical Society》1999,305(3):492-504

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GRB 990123: reverse and internal shock flashes and late afterglow behaviour     

P. Mészáros  M. J. Rees 《Monthly notices of the Royal Astronomical Society》1999,306(3):L39-L43

The prompt ( t ≲0.16 d) light curve and initial 9th-magnitude optical flash from GRB 990123 can be attributed to a reverse external shock, or possibly to internal shocks. We discuss the time decay laws and spectral slopes expected under various dynamical regimes, and the constraints imposed on the model by the observations, arguing that they provide strongly suggestive evidence for features beyond those in the simple standard model. The longer term afterglow behaviour is discussed in the context of the forward shock, and it is argued that, if the steepening after 3 d is due to a jet geometry, this is likely to be a result of jet-edge effects, rather than sideways expansion.  相似文献   

Electron spin resonance (ESR) and thermal ionization mass spectrometric (TIMS) 230Th/234U dating of teeth in Middle Paleolithic layers at Amud Cave,Israel     

W. Jack Rink  H.P. Schwarcz  H.K. Lee  J. Rees‐Jones  R. Rabinovich  E. Hovers 《Geoarchaeology》2001,16(6):701-717

Electron spin resonance (ESR) dating and thermal ionization mass spectrometric ²³⁰Th/²³⁴U dating was conducted on six teeth from the prehistoric site of Amud Cave. By combining the ESR and ²³⁰Th/²³⁴U analyses, we obtained burial ages for teeth in various layers of the site. Layer B₁/6–7, from which the Amud I Neanderthal skeleton was recovered, is dated to 53 ± 8 ka. Layer B₂/8, which yielded other important human remains including the Amud 7 skeleton, gives a mean burial age of 61 ± 9 ka. One tooth from the lowest layer (B₄) yielded a date of 70 ± 11 ka, but another tooth from this layer gave an 113 ± 18 ka. Despite this discrepancy, these ages agree with previously published TL ages on heated flints for the corresponding layers. This agreement between ESR on tooth enamel and TL on burned flint is also seen at all other sites studied with both methods in Israel. © 2001 John Wiley & Sons, Inc.  相似文献   

Three-dimensional heat,moisture and air transfer in unsaturated soils     

H. R. Thomas  S. W. Rees  N. J. Sloper 《国际地质力学数值与分析法杂志》1998,22(2):75-95

A new three-dimensional numerical model of coupled heat, moisture and air transfer in unsaturated soil is presented. In particular, the model accommodates moisture transfer in the form of liquid and vapour flow and heat transfer arising from conduction, convection and latent heat of vaporization. The bulk flow of dry air and the movement of air in a dissolved state are also included. The theoretical basis of the model, the finite element solution of the spatial terms and finite difference solution of the temporal terms are briefly presented. Attention is focused on the verification of the new numerical solution. This is achieved via comparisons with independent solutions of heat, moisture and air transfer in an unsaturated soil. The physical problem considered includes the highly non-linear hydraulic properties of sand. Thermal conductivity is also included as a function of soil moisture content. Excellent correlation of results is shown thus providing confidence in the new model. The new model is also applied to a number of test cases which illustrate the need for the development of a model which can fully include three-dimensional behaviour. In particular, three applications are presented each increasing in complexity. The first application illustrates three-dimensional heat transfer. This particular application is verified against existing commercial finite element software. Subsequent applications serve to illustrate how the coupled processes of heat moisture and air transfer combine to yield three-dimensional problems even within a simple geometric domain. Visualization of three-dimensional results is also addressed. © 1998 by John Wiley & Sons, Ltd.  相似文献   

Ichnology and sedimentology of aeolian and shallow-marine interactions in the Permian Unayzah Group of central Saudi Arabia: Towards a mechanism for infaunal colonization of coastal dune fields and erg margins     

Camilo A. Polo  John Melvin  Nigel P. Hooker  Andrew J. Rees  Murray K. Gingras  S. George Pemberton 《Sedimentology》2020,67(4):1797-1843

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The nature of scour development and scour protection at offshore windfarm foundations   总被引：1，自引：0，他引：1  

Whitehouse RJ  Harris JM  Sutherland J  Rees J 《Marine pollution bulletin》2011,62(1):73-88

Analysis and interpretation of monitoring data for the seabed bathymetry local to offshore windfarm foundations has shown how the scour develops in time and highlighted variations between sites with different seabed sediment characteristics, i.e. sands and clays. Results from European offshore windfarms have generated a unique dataset for comparison with previously published data. Where surficial sediment is underlain by a marine clay the scour (to date) has been limited, whilst those with unconstrained depths of sandy sediments show scour as deep as 1.38 times the monopile diameter. Scour protection has been installed at some sites for structural stability of the foundation or for cable protection. The flow interaction with the protection causes edge scour or secondary scour in the seabed around the protection. In some cases this scour is deeper than the unprotected case. The analysis has resulted in an improved evidence base for scour in the marine environment.  相似文献   

Changes in North Sea macrofauna communities and species distribution between 1986 and 2000     

Ingrid KrönckeHenning Reiss  Jacqueline D. EggletonJohn Aldridge  Magda J.N. BergmanSabine Cochrane  Johan A. CraeymeerschSteven Degraer  Nicolas DesroyJean-Marie Dewarumez  Gerard C.A. DuineveldKarel Essink  Hans HillewaertMarc S.S. Lavaleye  Andreas MollStefan Nehring  Richard NewellEivind Oug  Thomas PohlmannEike Rachor  Mike RobertsonHeye Rumohr  Michaela SchratzbergerRebecca Smith  Edward Vanden Berghe  Jan van DalfsenGert van Hoey  Magda VincxWouter Willems  Hubert L. Rees 《Estuarine, Coastal and Shelf Science》2011,94(1):1-15

The North Sea Benthos Project 2000 was initiated as a follow-up to the 1986 ICES North Sea Benthos Survey with the major aim to identify changes in the macrofauna species distribution and community structure in the North Sea and their likely causes.The results showed that the large-scale spatial distribution of macrofauna communities in the North Sea hardly changed between 1986 and 2000, with the main divisions at the 50 m and 100 m depth contours. Water temperature and salinity as well as wave exposure, tidal stress and primary production were influential environmental factors on a large (North Sea-wide) spatial scale.The increase in abundance and regional changes in distribution of various species with a southern distribution in the North Sea in 2000 were largely associated with an increase in sea surface temperature, primary production and, thus, food supply. This can be most likely related to the North Sea hydro-climate change in the late 1980s influenced by the variability in the North Atlantic Oscillation (NAO). Only one cold-temperate species decreased in abundance in 2000 at most of the stations. Indications for newly established populations of offshore non-native species were not found.Differences in macrofauna community structure on localised spatial scales were predominantly found north of the 50 m depth contour off the British coast along the Flamborough Head Front towards the Dogger Bank, off the coast of Jutland and at the Frisian Front. These changes were most likely attributed to stronger frontal systems in 2000 caused by the increased inflow of Atlantic water masses in relation to the hydro-climate change in the late 1980s.  相似文献   

Shifting post production patterns: exploring changes in New Zealand's seafood processing industry     

Stringer C  Simmons G  Rees E 《New Zealand geographer》2011,67(3):161-173

This paper examines the changing nature of New Zealand's seafood companies' production practices. The past 15 years has seen the offshore outsourcing of post-harvest fish gain unprecedented momentum. The growth in offshore processing is a further stage in an increasingly globalised fisheries value chain. Fish is head and gutted, frozen and then transported to processing sites in China where it is thawed, value-added processed and refrozen for export to the original sourcing country or third country markets. Reasons advanced by the industry for this shift in production practices include quota reductions, increasing production costs and the sale of trawlers.  相似文献   

Limits from rapid TeV variability of Mrk 421     

Celotti  Fabian  & Rees 《Monthly notices of the Royal Astronomical Society》1998,293(3):239-242

The extreme variability event in the TeV emission of Mrk 421, recently reported by the Whipple team, imposes the tightest limits on the typical size of the TeV emitting regions in active galactic nuclei (AGN). We examine the consequences that this imposes on the bulk Lorentz factor of the emitting plasma and on the radiation fields present in the central region of this active nucleus. No strong evidence is found for extreme Lorentz factors. However, energetics arguments suggest that any accretion in Mrk 421 has to take place at low rates, compatible with an advection-dominated regime.  相似文献   

Geomorphometric analysis of a rocky coastline: an example from Hornsund,Svalbard     

Zuzanna M. Swirad  W. Gareth Rees 《International journal of geographical information science》2013,27(9):1694-1717

We describe a method to extract a number of quantitative morphometric characteristics of a rocky coastline. The algorithm, which is implemented in the free open-source software GNU Octave, takes as its input an ordered set of coordinate pairs defining the coastline. It finds vertices of specific angularity at two different levels, first approximating convex features (headlands) and then looking for local maxima (embayment edges) in their vicinity. It extracts numerical parameters for each embayment delimited by the former points, including basic geometric parameters (e.g. area, depth and width) and coefficients expressing shapes of embayments (e.g. form factor, coefficient of asymmetry and compactness). These we adapted from morphometric studies of other geomorphic features. Complex headlands and random sectors of the coastline which are delimited by embayment edges are automatically removed. The method was developed and tested on Hornsund in Svalbard, where 20 headlands, 28 embayment edges and 20 embayments were identified, but could be adapted to a wide range of coastal situations. We consider a range of possible applications of the methods, including to the classification of coastlines, change detection and identifying controls on their morphologies, and we discuss the choice of optimum parameters for the algorithm.  相似文献