Chandra imaging of the complex X-ray core of the Perseus cluster     

A. C. Fabian  J. S. Sanders  S. Ettori  G. B. Taylor  S. W. Allen  C. S. Crawford  K. Iwasawa  R. M. Johnstone  P. M. Ogle 《Monthly notices of the Royal Astronomical Society》2000,318(4):L65-L68

We report subarcsec-resolution X-ray imaging of the core of the Perseus cluster around the galaxy NGC 1275 with the Chandra X-ray Observatory . The ROSAT -discovered holes associated with the radio lobes have X-ray bright rims which are cooler than the surrounding gas and not a result of shocks. The holes themselves may contain some hotter gas. We map strong photoelectric absorption across the northern lobe and rim owing to a small infalling irregular galaxy, known as the high-velocity system. Two outer holes, one of which was previously known, are identified with recently found spurs of low-frequency radio emission. The spiral appearance of the X-ray cooler gas and the outer optical parts of NGC 1275 may be due to angular momentum in the cooling flow.  相似文献   

The seismic anomaly beneath Iceland extends down to the mantle transition zone and no deeper   总被引：8，自引：0，他引：8  

G. R. Foulger  M. J. Pritchard  B. R. Julian  J. R. Evans  R. M. Allen  G. Nolet  W. J. Morgan  B. H. Bergsson  P. Erlendsson  S. Jakobsdóttir  S. Ragnarsson  R. Stefansson  K. Vogfjörd 《Geophysical Journal International》2000,142(3):F1-F5

A 3-D teleseismic tomography image of the upper mantle beneath Iceland of unprecedented resolution reveals a subvertical low wave speed anomaly that is cylindrical in the upper 250 km but tabular below this. Such a morphological transition is expected towards the bottom of a buoyant upwelling. Our observations thus suggest that magmatism at the Iceland hotspot is fed by flow rising from the mantle transition zone. This result contributes to the ongoing debate about whether the upper and lower mantles convect separately or as one. The image also suggests that material flows outwards from Iceland along the Reykjanes Ridge in the upper 200 km, but is blocked in the upper 150 km beneath the Tjornes Fracture Zone. This provides direct observational support for the theory that fracture zones dam lateral flow along ridges.  相似文献   

Fluorescent molecular hydrogen in the Eagle nebula     

L. E. Allen  M. G. Burton  S. D. Ryder  M. C. B. Ashley  J. W. V. Storey 《Monthly notices of the Royal Astronomical Society》1999,304(1):98-108

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Wide Binaries among High-Velocity and Metal-Poor Stars     

Christine Allen  M.A. Herrera  A. Poveda 《Astrophysics and Space Science》1999,265(1-4):233-234

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Rehabilitation of Saline Wetland, Olympics 2000 Site, Sydney (Australia)—II: Saltmarsh Transplantation Trials and Application     

M. D. Burchett  C. Allen  A. Pulkownik  G. Macfarlane 《Marine pollution bulletin》1999,37(8-12):526-534

The New South Wales Olympic Co-ordination Authority, which is responsible for the redevelopment of the site for the Olympic Games 2000, Sydney, is committed to the rehabilitation of the remnant ecosystems remaining on the site. This paper describes a 3-year saltmarsh transplantation project, and resulting management approaches for the rehabilitation of other saline wetland areas on the site. Two series of cuttings (spring and autumn) were made, including three dominant species and three species rare in Sydney. It was found that all the species could be propagated without difficulty, but field survival and growth were much higher for the spring series than the autumn one. Measurement was also made of the colonisation of mangrove and saltmarsh species that occurred at the site over the course of the trials. New understandings of estuarine wetland colonisation have emerged, and the information has been used to develop methods of transplantation for other parts of the Olympic site, and to define management needs for monitoring success.  相似文献   

A second review of the international status of engineering geology — encompassing hydrogeology, environmental geology and the applied geosciences     

Allen W. Hatheway  George M. Reeves   《Engineering Geology》1999,53(3-4):259-296

Engineering geology, in 1996, worldwide, was experiencing considerable turmoil due to the uncertain nature of national economies and the general situation of inadequate funds to meet the demands of failing of the national infrastructures that serve citizens. Aside from the previously war-damaged cities of Western Europe, new public service systems of transportation and utilities elsewhere often lagged well behind growth.

It will be some time before international aid and civil engineering contracts are initiated for anything other than humanitarian and basic emergency aid work in these areas.

Many countries in the western hemisphere, eastern Europe, the former Soviet Union and developing nations in particular are still in need of basic water and sewage services as well as repair and replacement of old existing systems. Continued partisan warfare in the Balkan states of Albania, Bosnia, Croatia and Serbia forecast the eventual need for redevelopment. Rumblings of broad-scale economic problems in Far-Eastern economies did little to make overseas contract opportunities in these areas very attractive.

Large consulting firms were challenged by an increasing number of individual and small practices who are prepared to operate on 1970's rates and prices for services and government and industry was taking advantage of that situation. More and more individuals were offering services in engineering geology and associated engineering fields and there was a sense of not having enough work to go around. Hence, price competition was again being promoted. Consequently in both Europe and the Americas, the variability of competence was enlarging and a significant amount of so-called ‘professional ’ work was lacking in overall quality. This was especially evident in ‘Environmental’ areas of work.

This begs the question: ‘Is not engineering geology, or any other aspect of applied geosciences, not environmental in nature and essence, fundamentally and in entirety?’

Environmental restoration demands were still being made by governments, but the pressure to complete such work was being relaxed on account of economics. Our clients were asking for more service at lower fees. Clients were still largely unwilling to openly acknowledge that less money spent on competent engineering geologic consultation means that more risk should be accepted by the owner or operator of projects.  相似文献   

Bioremediation in Fractured Rock: 1. Modeling to Inform Design,Monitoring, and Expectations          下载免费PDF全文

Claire R. Tiedeman  Allen M. Shapiro  Paul A. Hsieh  Thomas E. Imbrigiotta  Daniel J. Goode  Pierre J. Lacombe  Mary F. DeFlaun  Scott R. Drew  Carole D. Johnson  John H. Williams  Gary P. Curtis 《Ground water》2018,56(2):300-316

Field characterization of a trichloroethene (TCE) source area in fractured mudstones produced a detailed understanding of the geology, contaminant distribution in fractures and the rock matrix, and hydraulic and transport properties. Groundwater flow and chemical transport modeling that synthesized the field characterization information proved critical for designing bioremediation of the source area. The planned bioremediation involved injecting emulsified vegetable oil and bacteria to enhance the naturally occurring biodegradation of TCE. The flow and transport modeling showed that injection will spread amendments widely over a zone of lower‐permeability fractures, with long residence times expected because of small velocities after injection and sorption of emulsified vegetable oil onto solids. Amendments transported out of this zone will be diluted by groundwater flux from other areas, limiting bioremediation effectiveness downgradient. At nearby pumping wells, further dilution is expected to make bioremediation effects undetectable in the pumped water. The results emphasize that in fracture‐dominated flow regimes, the extent of injected amendments cannot be conceptualized using simple homogeneous models of groundwater flow commonly adopted to design injections in unconsolidated porous media (e.g., radial diverging or dipole flow regimes). Instead, it is important to synthesize site characterization information using a groundwater flow model that includes discrete features representing high‐ and low‐permeability fractures. This type of model accounts for the highly heterogeneous hydraulic conductivity and groundwater fluxes in fractured‐rock aquifers, and facilitates designing injection strategies that target specific volumes of the aquifer and maximize the distribution of amendments over these volumes.  相似文献   

Bioremediation in Fractured Rock: 2. Mobilization of Chloroethene Compounds from the Rock Matrix          下载免费PDF全文

Allen M. Shapiro  Claire R. Tiedeman  Thomas E. Imbrigiotta  Daniel J. Goode  Paul A. Hsieh  Pierre J. Lacombe  Mary F. DeFlaun  Scott R. Drew  Gary P. Curtis 《Ground water》2018,56(2):317-336

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欧洲大西洋及北海南部海岸全新世泥滩沼泽沉积序列     

AlienJRL  李杨帆 《海洋地质前沿》2004,20(5):6-8

1全新世记录Godwin(1943)早期对广泛分布于欧洲西北部海岸中一晚全新世夹层泥炭的观测表明,上述因子和过程(包括一些区域的显著性)已完成对整个研究区相似地层序列的塑造。仅在主要的潮沟和海岸离岸砂坝发育处或相对海平面下降的稳定期的结果有明显的偏差。  相似文献   

Large-scale mines and local-level politics: between New Caledonia and Papua New Guinea     

Matthew Allen 《The Australian geographer》2019,50(4):547-549

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