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241.
242.
Most workflow systems that support data provenance primarily focus on tracing lineage of data. Data provenance by data lineage provides the derivation history of data including information about services and input data that contributed to the creation of a data product. We show that tracing lineage by means of full backward chaining not only enables users to share, discover and reuse the data, but also supports scientific data processing through storage, retrieval and (re)processing of digitized scientific data. In this paper, we present Astro-WISE, a distributed system for processing, analyzing and disseminating wide field imaging astronomical data. We show how Astro-WISE traces lineage of data and how it facilitates data processing, retrieval, storage and archiving. Particularly we show how it solves issues related to the changing data items typical for the scientific environment, such as physical changes in calibrations, our insight in these changes and improved methods for deriving results. 相似文献
243.
by Tom Clemo Warren Barrash Edward C. Reboulet Timothy C. Johnson Carsten Leven 《Ground water》2009,47(4):515-525
This paper describes a combined field, laboratory, and numerical study of electromagnetic borehole flowmeter measurements acquired without the use of a packer or skirt to block bypass flow around the flowmeter. The most significant finding is that inflow through the wellbore screen changes the ratio of flow through the flowmeter to wellbore flow. Experiments reveal up to a factor of two differences in this ratio for conditions with and without inflow through the wellbore screen. Standard practice is to assume the ratio is constant. A numerical model has been developed to simulate the effect of inflow on the flowmeter. The model is formulated using momentum conservation within the borehole and around the flowmeter. The model is embedded in the MODFLOW-2000 ground water flow code. 相似文献
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245.
This paper describes and analyses a hillslope–channel slope failure event that occurred at Wet Swine Gill, Lake District, northern England. This comprised a hillslope slide (180 m3, c. 203 ± 36 t), which coupled with the adjacent stream, resulting in a channelized debris flow and fluvial flood. The timing of the event is constrained between January and March 2002. The hillslope failure occurred in response to a rainfall/snowmelt trigger, on ground recently disturbed by a heather moorland fire and modified by artificial drainage. Slide and flow dynamics are estimated using reconstructed velocity and discharge values along the sediment transfer path. There is a rapid downstream reduction in both maximum velocity, from 9·8 to 1·3 m s?1; and maximum discharge, ranging from 33·5 to 2·4 m3 s?1. A volumetric sediment budget quantified a high degree of coupling between the hillslope and immediate channel (~92%: 167 m3), but virtually all of the sediment was retained in the first‐order tributary channel. Approximately 44% (81 m3) of the slide volume was retained in the run‐up deposit, and termination of the debris flow prior to the main river meant that the remainder did not discharge into the fluvial system downstream. These results suggest poor transmission of sediment to the main river at the time of the event, but importantly an increase in available material for post‐event sediment transfer processes within the small upland tributary. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
246.
Brenda Moraska Lafrancois Suzanne Magdalene D. Kent Johnson 《Journal of Paleolimnology》2009,41(4):603-622
Long-term water quality monitoring data from two riverine lakes in the Upper Mississippi River basin, Lakes St. Croix and
Pepin, were analyzed to compare the long-term average water quality conditions and land use distributions, water quality trends
and loads at lake inlets and outlets, trends from long-term versus short-term monitoring records, and the ability of paleolimnological
cores to accurately infer lake water quality conditions. During the 1976–2004 period, the long-term average concentrations
of nutrients, suspended solids, and chlorophyll-a were consistently lower at the Lake St. Croix inlet versus the Lake Pepin inlet, which drains a greater proportion of urban
and agricultural runoff. Despite these differences, nutrient trends were similar at the inlets to both lakes; reductions in
total phosphorus and ammonium concentrations were attributed to improvements in point source technologies, whereas increasing
nitrate concentrations were attributed to both point source changes and nonpoint source increases. Despite improvements in
several water quality variables, nitrate concentrations are increasing in both lakes, sediment trends indicate persistent
nonpoint source inputs to Lake Pepin, and current total phosphorus concentrations remain well above pre-1950s levels in both
lakes. Since urban development and agriculture are increasing in the Lake St. Croix and Lake Pepin Watersheds, continued point
source regulation and additional nonpoint source control efforts will be needed to further improve water quality in these
lakes. The 1976–2004 trends for most water quality variables were similar at inlet versus outlet sites on Lake St. Croix.
Trends at Lake Pepin inlet versus outlet sites were less similar, but data availability limited the comparison to the 1993–2003
period. While the truncated data record highlighted short-term trends in both lakes, the full data record was most useful
for exploring general patterns in water quality. Length of monitoring record affected our ability to detect trends at the
inlets to both lakes, and altered the magnitude of detected trends. During the two decades of the 1980s and 1990s, paleolimnological
estimates of retained phosphorus loads were similar to those estimated from recent water quality monitoring. These similarities
support the use of paleolimnological approaches to infer past water quality conditions in Lakes St. Croix and Pepin.
This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this
special issue of the Journal of Paleolimnology. D. R. Engstrom served as guest editor of the special issue. 相似文献
247.
Hong Luo Paul Dahlen Paul C. Johnson Tom Peargin Todd Creamer 《Ground Water Monitoring & Remediation》2009,29(1):81-91
Data requirements for assessing the significance of the soil vapor intrusion pathway are evolving, and the collection and interpretation of subslab and near-slab soil-gas samples are under discussion. The potential for different assessment paradigms for aerobically biodegradable and recalcitrant chemicals is also frequently debated. In this work, the soil-gas distribution beneath and around a slab-on-grade building overlying shallow (0.5 to >1.5 m below ground surface) petroleum hydrocarbon–impacted coarse alluvial soils was studied. The study spanned about 12 months, including the sampling of soil-gas hydrocarbon and oxygen concentrations, subslab soil vs. building pressure differentials and included weather conditions. Three-dimensional soil-gas concentration "snapshots" using samples from 79 soil-gas sampling points are presented here. Significant spatial variability was observed with hydrocarbon and oxygen concentrations ranging from about <0.01 to 200 mg/L and 0 to 21% v/v, respectively. The presence of oxygen and the depth to petroleum-impacted soils appeared to be the dominant factors in controlling the soil-gas distribution; the depletion of hydrocarbons over short lateral and vertical distances (<2 m) was observed in the well-oxygenated regions. Composition data suggest preferential biodegradation of lighter compounds at some points, as reflected in the ratio of the masses of chemicals eluting on the gas chromatography between methane and pentane (C1 and C5) and all others after pentane (>C5). 相似文献
248.
249.
A. Arukwe R. Male L. Johnson K. Peck-Miller T. Collier A. Goksyr 《Marine environmental research》2000,50(1-5)
New cellular and molecular tools are enabling researchers to study the basic mechanisms of action of natural reproductive hormones, and of endocrine disrupters, including xenoestrogens. Zonagenesis is defined by the hepatic synthesis of the eggshell Zona radiata proteins (Zrp), their secretion and transport in the blood and their uptake by maturing oocytes. Zrps are comprised of three-to-four protein monomers in the 50–60 kDa MW range and show structural similarity to proteins of the Zona pellucida; an extracellular envelope that lies immediately outside the plasma membrane in the eggs of placental mammals. We studied the xenoestrogen-induced elevation in hepatic mRNA and plasma levels of Zrp and vitellogenin (Vtg) in several fish species. Eggshell Zrp protein and mRNA was induced in juvenile salmon by exposure to nonylphenol (NP: given singly or in combination with other xenoestrogens/xenobiotics). In English sole (Pleuronectes vetulus), Zrp was induced in the plasma of mature female, E2- and NP-treated male fish. We are currently using salmon cDNA probes to study estrogen-receptor, Zrp and Vtg mRNA expression in English sole treated with E2- and NP. Validation in a semi-field experiment showed that effluent from an oil refinery treatment plant caused a dose-dependent induction of Zrp and Vtg in juvenile salmon. However, a component corresponding to Zrp-β was more responsive than Zrp-α and Zrp-γ and also more than Vtg. Zrp seem to be a sensitive complement to Vtg analysis, and appear to be a more ecologically significant biomarker of estrogenicity. 相似文献
250.
There has been considerable recent concern over the amount of vegetation clearance in the wet tropics of northern Australia. This paper reports on the results of a case study undertaken in the lower Herbert River catchment in north-east Queensland, which utilised remote sensing and Geographic Information Systems (GIS) to assess both spatial and temporal changes in land cover since European settlement in the mid-nineteenth century. We demonstrate that since European settlement there has been a substantial reduction in the area of Melaleuca, rainforest, and eucalyptus-dominated land-cover patterns. We also provide a range of quantitative measures to show that the landscape diversity, integrity and quality of these ecosystems have also declined between the 1860s and 1996. We conclude that reform is required at policy, planning and enterprise levels if the ecological, economic and social values of these systems are to be maintained in the future. 相似文献