A Study of the Coronal Non-thermal Velocity in Polar Regions During the Rise from Solar Minimum to Solar Maximum in Cycle 24     

L. Harra  D. Baker  S. J. Edwards  H. Hara  R. Howe  L. van Driel-Gesztelyi 《Solar physics》2015,290(11):3203-3220

  相似文献   

The Humber Estuary, Eastern England: Strategic planning of flood defences and habitats     

Edwards AM  Winn PS 《Marine pollution bulletin》2006,53(1-4):165-174

The Humber Estuary Shoreline Management Plan provides a long-term strategy for investment in sustainable defences to reduce the risk to people and property from flooding in part of Eastern England. In addition to the estuary's economic importance with its ports, industry and the third of a million people living on its floodplain, the Humber is of outstanding value for wildlife and its historic environment. The plan has to meet the needs of these activities and take account of rising sea level. It is based on extensive technical studies and modelling. The realignment of some embankments is being examined so that the creation of intertidal habitat will offset losses from coastal squeeze, increase the stability for some lengths of embankment and reduce extreme high flood levels in the tidal rivers. The 80 ha Paull Holme Strays managed realignment wetland was completed in the summer of 2003 and work is in progress on another at Alkborough. Other such realignment will be developed as part of the implementation of the long term strategy.  相似文献   

Holocene climate change and carbon cycling in a groundwater-fed, boreal forest lake: Dune Lake, Alaska     

Bruce P. Finney  Nancy H. Bigelow  Valerie A. Barber  Mary E. Edwards 《Journal of Paleolimnology》2012,47(1):43-54

We compared cladoceran assemblages in modern and pre-industrial sediments from cores taken in 48 softwater lakes located in four main regions of Nova Scotia (Canada) to evaluate the impacts of acidification and other recent environmental stressors. Lakes in Kejimkujik National Park showed significant increases in Holopedium relative abundances and significant decreases in Alona and other chydorids since pre-industrial times, which appear to be related to declines in pH and calcium (Ca) concentrations caused by acidic deposition. Lakes in Bridgewater also showed a significant decrease in Alona, as well as a significant increase in macrothricid (Acantholeberis and Ophryoxus) taxa that cannot be explained by declines in pH, although declines in [Ca] have been recorded. Lakes in Yarmouth did not show any significant regional changes in major cladoceran species groups. Still, pre-industrial assemblages in these lakes significantly differed from modern assemblages, with assemblage changes being lake-specific and likely related to interactions between local and regional stressors acting on individual lakes. Finally, lakes in Cape Breton Highlands National Park, located on the taiga plateau, have received historically lower levels of sulphate deposition relative to other regions in the province, and recorded a significant decrease in Alona similar to Bridgewater lakes. The province-wide decrease in Alona across different acid deposition rates suggests that limnological changes related to climate warming may be responsible. Overall, this study shows that acidification history is an important predictor of cladoceran assemblage changes since pre-industrial times in Nova Scotia lakes, although multiple stressors result in complex Cladocera responses in some regions.  相似文献   

Rescue palaeontology     

Dee Edwards  Dave Williams 《Geology Today》2011,27(2):65-69

A technique for replicating large rock outcrops has been developed so that casts of these surfaces can be archived in their present stage of preservation. Researchers can then study these casts in the laboratory under optimum lighting conditions, sometimes revealing new fossil evidence, while students and members of the public can be shown geological features that might otherwise be inaccessible to them.  相似文献   

Separating climatic and possible human impacts in the early Holocene: biotic response around the time of the 8200 cal. yr BP event     

Kevin J. Edwards  Peter G. Langdon  Heather Sugden 《第四纪科学杂志》2007,22(1):77-84

The early Holocene is characterised by rapid climate change events, which in the North Atlantic region are often associated with changes in thermohaline circulation. Superimposed on this in northwest Europe is localised evidence for human impact on the landscape, although separating climatic and anthropogenic mechanisms for environmental change is often difficult. Biotic and sedimentological evidence from a lacustrine sequence from the Inner Hebrides, Scotland, shows a considerable reduction in inferred local woodland centred upon 8250 cal. yr BP. These data correlate precisely with a distinctive rise in the charcoal:pollen ratio and hence suggest a possible Mesolithic human impact upon the vegetation around this time. A quantitative temperature reconstruction from chironomid analyses from the same sequence, supported by sedimentological data, indicates that the fall in arboreal pollen taxa occurred as climate warmed significantly during the early Holocene. This warming was followed by a significant cold event, with mean July temperatures reduced by 2°C, that lasted for at least 320 years ca. 7790–7470 cal. yr BP. Woodland recovered during this phase suggesting that the vegetation during the 8250 cal. yr BP interval was likely to have been responding to human activity, and not climate, and hence it is possible at specific sites to separate the influence of these key drivers of environmental change. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Microbial response to surface microtopography: the role of metabolism in localized mineral dissolution     

Katrina J. Edwards  Andrew D. Rutenberg 《Chemical Geology》2001,180(1-4):19-32

We examine the role of microtopographical surface features on sulfide minerals in localizing and aligning bacterial adhesion. Experimental data shows strong correlation between bacterial cell alignment and principal crystallographic axes of pyrite (100 and 110). While bacteria often adhere to visible surface imperfections such as scratches, in many cases no associated surface features are visible. Additionally, the size of the surface imperfection does not unambiguously determine its effect in localizing and aligning bacterial cells. We theoretically model bacterial adhesion. We find that the depth of a surface feature such as a scratch is less important than its cross-sectional shape. Surface features that conform to the bacterial shape can strongly alter local bacterial adhesion energies, even with heights of only 10 nm. Hence, small local surface alterations due to bacterial metabolism could strongly affect local adhesion parameters, and may account for the observed bacterial distributions on mineral surfaces.  相似文献   

A large volume magnetic field free space for thermal demagnetization and other experiments in palaeomagnetism     

M. W. McElhinny  G. R. Luck  D. Edwards 《Pure and Applied Geophysics》1971,90(1):126-130

Summary Three orthogonal coil systems have been constructed within a cube of side 2.5 m to cancel the geomagnetic field to less than 1 gamma over a large volume. The north-south and vertical components are cancelled by systems of four square coils whilst a square Helmholtz pair cancels the east-west component. Cancellation to 1 part in 10⁵ (0.5 gamma in Canberra) is achieved within a sphere of diameter 35 cm, more than 20 times the field-free volume which could be obtained using conventional Helmholtz coils within the available space. Three fluxgate detectors monitor the residual field and their output, taken through a feedback circuit, allows compensation for field variations. The residual field can be maintained to less than 0.5 gamma over the working volume of about 22,000 cm³ during the critical part of a laboratory experiment.  相似文献   

Artificial watershed acidification on the Fernow Experimental Forest, USA     

M. B. Adams  P. J. Edwards  F. Wood  J. N. Kochenderfer 《Journal of Hydrology》1993,150(2-4):505-519

A whole-watershed manipulation project was begun on the Fernow Experimental Forest in West Virginia, USA, in 1987, with the objective of increasing understanding of the effects of acidic deposition on forest ecosystems. Two treatment watersheds (WS9 and WS3) and one control watershed (WS4) were included. Treatments were twice-ambient N and S deposition, applied via NH₄SO₄ fertilizer, with three applications per year. Three years of pretreatment data were collected and used for calibration. Stream water chemistry data collected during 3 years of treatment were evaluated. Stream water pH and electrical conductivity were not significantly affected by the elevated N and S inputs on either treatment watershed. On WS9, there were no statistically significant treatment effects on stream water export of Ca, SO₄, or NO₃. On WS3, however, stream export of both NO₃ and Ca have increased as a result of acidification treatments. The implications of these results are discussed. Research is continuing so that the processes involved may be elucidated. In addition, effects on vegetation, aquatic invertebrates and amphibians also are being evaluated.  相似文献   

Conductivity anomalies: lower crust or asthenosphere?     

R.N. Edwards  R.C. Bailey  G.D. Garland 《Physics of the Earth and Planetary Interiors》1981,25(3):263-272

The indication from surface measurements of a zone of relatively high conductivity (resistivity<200 ohm-m) at depths between 20 and 50 km has become so general over the Earth that regions without this zone can be considered anomalous. However, the depths indicated often span the lower crust and the uppermost mantle, so that before any effect can be definitely attributed to one or the other, the depth resolution in the electromagnetic measurements must be carefully considered. This paper applies the eigenvector decomposition of generalized linear inverse theory to soundings by Schlumberger resistivity, by magnetotellurics, by man-made electromagnetic fields formed by controlled current flow in grounded electric transmission lines, and by natural magnetic field variation studies to improve the bounds on depth, thickness and conductivity of a conductive layer. It is shown that many of the methods are capable of giving the depth to the top of a conductor with remarkable accuracy. Joint inversion of two or more of them offers an advantage in the separation of thickness and conductivity of both conductive and resistive layers. Natural geomagnetic field transfer functions, while accurately mapping the position of the edge of a conductor, do not provide the resolution of the other techniques, largely because the frequencies that can be practically measured at present are much too low.  相似文献   

The effect of slime coatings of the serpentine minerals,chrysotile and lizardite,on pentlandite flotation     

C.R. Edwards  W.B. Kipkie  G.E. Agar 《International Journal of Mineral Processing》1980,7(1):33-42

Serpentine minerals in the gangue often interfere with the concentration of nickel sulfide ores. The influence of slime coatings of the serpentine minerals chrysotile and lizardite on the flotation of unoxidized pentlandite has been studied. In addition to microflotation testing at pH 9 with potassium amyl xanthate collector, electrophoresis and scanning electron microscopy have been used. The formation of a slime coating was found to be directly related to the surface charges on the slime and the sulfide mineral. Chemical additives which modified the slime surface charge, such as carboxy methyl cellulose, dextrin, sodium pyrophosphate and sodium silicate, were shown to be effective in reducing the adverse influence of the slime on the flotation of pentlandite.  相似文献