Ice sheets and Late Quaternary environmental change by M. J. Siegert,John Wiley and Sons Ltd,Chichester, 2001. No of pages: 231. ISBN 0 471 98569 4 (paperback); 0 471 98570 8 (hardback).     

Neil Glasser 《Geological Journal》2003,38(2):188-189

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Simple Resistivity Probe System for Real-Time Monitoring of Injected Reagents     

David Stevenson  Felipe Solano  Yunxiao Wei  Neil R. Thomson  James F. Barker  J. F. Devlin 《Ground Water Monitoring & Remediation》2020,40(4):54-66

In situ treatment usually requires contact between an injected reagent and target contaminant to realize mass removal from source zones and plumes. Despite significant site characterization efforts, unknown heterogeneities that exist at all spatial scales often hinder prediction of the distribution of injected reagents. To provide remediation practitioners with additional information on the distribution of injected reagents, a prototype real-time monitoring probe was designed and tested. This new probe comprises a two-wire resistivity circuit, hence the designation dipole resistivity probe (DRP). The low-cost DRPs were built to be attached as arrays to a central stalk, and installed by direct-push techniques. An installed network of multilevel DRPs can be used to detect the arrival, persistence, and relative concentration of a high-conductivity reagent solution in real-time across a zone of interest. Static cell and sandbox experiments were conducted to test and refine the DRP design before field testing. Static cell experimental results indicated that the DRP was sensitive to solution electrical conductivity (EC), and that the probe response and EC relationship is nonlinear and dependent on the fixed resistor used. The choice of fixed resistor can be adjusted to optimize the DRP response over a critical EC range of interest. Under dynamic conditions in the sandbox, the DRP was able to reproduce breakthrough profiles collected by a commercial EC sensor. The results from two field studies demonstrated the utility of the DRPs to generate information regarding the arrival and persistence of reagents in an efficient and cost-effective manner. The first field study used a network of DRPs to monitor the land application of a sodium sulfate solution, and the second field study employed DRPs to monitor the distribution and longevity of a persulfate solution. While additional field testing is warranted, the results presented are encouraging and suggest that this low-cost system can be used to improve our understanding of the detailed migration of injected reagents in treatment zones.  相似文献   

Reflections from the Editor-in-Chief of Groundwater Monitoring & Remediation     

Neil R. Thomson 《Ground Water Monitoring & Remediation》2020,40(4):15-18

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The Effects of Hermit Crabs
on Hydractiniid Hydroids The effects of hermit crabs on hydractiniid hydroids     

David H. Van Winkle  Krista Longnecker  & Neil W. Blackstone 《Marine Ecology》2000,21(1):55-67

Abstract. Hermit crab shells are often encrusted with diverse communities of epibionts. To explore the effects of hermit crabs on the interactions of these encrusting species, two species of hydractiniid hydroids, Hydractinia symbiolongicarpus and Podocoryna carnea , were examined in the presence and absence of Pagurus longicarpus hermit crabs. Colonies growing on Littorina littorea snail shells with hermit crab hosts were compared to those growing on shells without crabs. These experiments suggest that hermit crabs variably affect colony polyp number, colony morphology and the outcome of interspecific competition, according to the size and number of crabs; other factors include water temperature, food availability and hydroid clonal genotype. In order to allow image analysis of perturbations of colony morphology, hydroids were grown on glass surfaces both exposed and unexposed to hermit crabs. Relative to colonies growing on unexposed surfaces, colonies growing on exposed surfaces exhibited larger within-colony patches, thus decreasing the total encrusted surface area and polyp number of colonies. Further, on glass surfaces, hermit crabs accelerated the time to the resolution of interspecific competition ( i.e. , the overgrowth of one colony by the other). While a number of factors may contribute to the relative abundance of these encrusting species, under most circumstances P. longicarpus have large effects on hydractiniid hydroids. Mechanisms underlying these effects likely include hydrodynamics and mechanical disturbance.  相似文献   

Water and salt balance modelling to predict the effects of land-use changes in forested catchments. 2. coupled model of water and salt balances     

Murugesu Sivapalan  Neil R. Viney  John K. Ruprecht 《水文研究》1996,10(3):413-428

A long-term salt balance model is coupled with the small catchment water balance model presented in Part 1 of this series of papers. The salt balance model was designed as a simple robust, conceptually based model of the fundamental salt fluxes and stores in forested and cleared catchments. The model has four interdependent stores representing salt storage in the unsaturated zone, the deep permanent saturated groundwater system, the near-stream perched groundwater system and in a ‘salt bulge’ just above the permanent water-table. The model has performed well in simulations carried out on Salmon and Wights, two small experimental catchments in south-west Western Australia. When applied to Wights catchment the salt balance model was able to predict the stream salinities prior to clearing of native forests, and the increased salinities after the clearing.  相似文献   

Lower carboniferous (Dinantian) stratigraphy and structure in the Kingscourt Outlier,Ireland     

Peter Strogen  Ian D. Somerville  Neil A. H. Pickard  Gareth li. Jones 《Geological Journal》1995,30(1):1-23

Logging of 55 recent boreholes, together with remapping, has resulted in a fundamental reassessment of the stratigraphy and sedimentology of the Dinantian Kingscourt Outlier. Despite the present isolated position of the outlier within the Longford-Down Massif, the Kingscourt rocks are an integral part of the Dublin Basin succession. The newly defined Ardagh Platform marks the most northerly limit to basinal sedimentation in the Dinantian Dublin Basin. The Courceyan is a typical but thinner, north Dublin Basin succession with two new formal units: the Rockfield Sandstone Member and the Kilbride Formation. The latter, a coarse-grained, well washed limestone of latest Courceyan to early Chadian (late Tournaisian) age is the shallow water equivalent of the Feltrim Formation (Waulsortian facies), which is absent in the outlier. The Courceyan interval in the north of the outlier is markedly attenuated. In the succeeding Chadian-Brigantian interval basinal facies predominate in the south, but on the Ardagh Platform an almost complete coeval Viséan shallow water sequence is found. A new platform unit (Deer Park Formation) of latest Asbian to Brigantian age is defined in the Ardagh area. The Dee Member (Chadian) is newly defined for the lower part of the basinal Tober Colleen Formation and the Altmush Shale Member is formally defined for the upper part of the Loughshinny Formation. Two major structures dominate the Kingscourt Outlier: the NE-SW trending Moynalty Syncline in the south and the N-S trending Kingscourt Fault. Both are Hercynian structures, but probably represent reactivated Caledonide basement-controlled structures. Dinantian syn-depositional faulting is indicated in both the Courceyan (‘Kingscourt Sag’) and Chadian-Asbian. The latter period of faulting in the Ardagh area separates platform facies in the north from basinal facies to the south. In the late Asbian, platform facies with carbonate build-ups prograded south into the basin as far south as Nobber, but in the latest Asbian to Brigantian, basinal facies extended northwards over the collapsed platform margin.  相似文献   

Hydrodynamic characteristics of a lunate shape oscillating propulsor     

Pengfei Liu  Neil Bose   《Ocean Engineering》1999,26(6):325

Research was conducted to study the hydrodynamic efficiency of a foil with aft-swept wing tips. A potential flow based time domain panel method was formulated to predict the performance of a lunate and rectangular foil in large amplitude, unsteady motion. Skin drag was approximated and boundary layer growth and separation were also estimated. Hydrodynamic efficiency was evaluated in terms of propulsive efficiency and thrust coefficient of the foil. Results are presented for a lunate shaped planform and for a rectangular foil. Predictions show that the lunate shaped planform has a substantially higher propulsive efficiency (13% higher) than the rectangular foil under heavy load conditions when the feathering parameter is zero, throughout a range of reduced frequencies (0.2 to 1.8). Under a medium load condition, however, the rectangular foil gave a higher propulsive efficiency at reduced frequencies less than 0.5 and the same efficiency value at a reduced frequency of 1.8. For a practical range of reduced frequencies between 0.5 and 1.0, the lunate tail gave higher propulsive efficiency. The lunate planform gave a lower thrust coefficient at a heavy load and higher thrust at a medium load condition than the rectangular planform for all reduced frequencies.  相似文献   

Impact of global change on the biogeochemistry and ecology of an Arctic freshwater system   总被引：2，自引：0，他引：2  

John E. Hobbie  Bruce J. Peterson  Neil Bettez  Linda Deegan  W. John O'Brien  George W. Kling  George W. Kipphut  William B. Bowden  Anne E. Hershey 《Polar research》1999,18(2):207-214

Lakes and streams in the foothills near Tookik Lake, Alaska, at 68°N have been studied since 1975 to predict physical, chemical and biological impacts of future global change. Experimental manipulations include whole lake and continuous stream fertilization as well as removal and addition of predators (copepods, lake trout, grayling, sculpin). Based on our evidence the following scenario is likely. Warming thaws the upper layers of permafrost and streams and lakes become enriched with phosphorus. Streams respond quickly with higher production of diatoms but animal grazers keep biomass changes to a minimum. Fish productivity also increases. If phosphorus levels are too high, mosses become the dominant primary producer and sequester all of the nutrients. Growth of Arctic grayling under the present conditions only occurs in summers with higher than average stream flow. The present population would be stressed by warmer temperatures. When higher phosphorus levels reach lakes and cause slight europhication, the number of trophic levels will increase, especially within the microbial food web. Warmer lake temperatures increase stratification and, combined with eutrophication, could decrease oxygen in the hypolimnion. Oxygen levels will also decrease in winter under the ice cover. Eventually this habitat change will eliminate the lake trout, a top predator. Removal of lake trout results in a striking increase in abundance and productivity of smaller fish, including small lake trout, and the emergence of burbot as an alternate top predator. Large species of zooplankton will become virtually extinct.  相似文献   

Soil Vacuum Extraction of Perchloroethylene from the Borden Aquifer   总被引：1，自引：0，他引：1  

Neil R. Thomson  David J. Flynn 《Ground water》2000,38(5):673-688

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Autumn MIST Meeting     

Neil Arnold 《Astronomy& Geophysics》2000,41(1):1.29-1.30

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