Functional assessment of a reference wetland set as a tool for science, management and restoration   总被引：1，自引：0，他引：1  

Stuart E. G. Findlay  Erik Kiviat  W. Charles Nieder  Elizabeth A. Blair 《Aquatic Sciences - Research Across Boundaries》2002,64(2):107-117

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Large N-S convergence at the northern edge of the Tibetan plateau? New Early Cretaceous paleomagnetic data from Hexi Corridor, NW China   总被引：1，自引：0，他引：1  

Yan Chen  Hanning WuVincent Courtillot  Stuart Gilder 《Earth and Planetary Science Letters》2002,201(2):293-307

Nine Early Cretaceous paleomagnetic sites have been collected in the Yumen area of the Hexi Corridor (NW China). Magnetic directions isolated at lower temperatures fail the fold test, and lie close to the geocentric axial dipole field direction before tilt correction. High temperature components are carried by magnetite and/or hematite, all with normal polarity, and pass the fold test. The average paleomagnetic pole from the nine sites is at λ=75.5°N, φ=169.9°E (A₉₅=7.7°). These results are consistent with those from other areas of the North China block (NCB), but significantly different from those from the Qaidam Basin on the southern side of the Qilian Mountains. They suggest that: (1) the Yumen region behaved as a rigid part of the NCB since at least the Early Cretaceous; (2) 740±500 km of north-south directed convergence has taken place between the NCB and Qaidam, within the Qilian Mountains and (3) extrusion of Qaidam was accompanied by a 23±5° relative rotation with respect to North China. This is larger than implied by the maximum left lateral slip on the Altyn Tagh fault system. The same data imply some 1000±800 km of Cenozoic motion between the Tarim and NCB blocks, which were so far believed to have formed a rigid entity since at least the Jurassic. One interpretation could be that all Tarim and Qaidam Cretaceous paleomagnetic samples from red beds, but not those from Yumen and the NCB, suffered significant inclination shallowing, as observed in Cenozoic red beds from Central Asia. So far, we do not find support for this possibility. Possible tectonic interpretations include: (1) the existence of a large, as yet uncharted, tectonic discontinuity between Tarim and the NCB in the vicinity of the desert corridor near 95-100°E longitude; (2) the occurrence of significant deformation within southwestern Tarim, to the north of Yingjisha where paleomagnetic sites were obtained, or (3) persistent clockwise rotation of Tarim with respect to the NCB, for at least 20 Ma, at the rate found for current block kinematics.  相似文献   

Flotation circuits for poorly floating coals     

Bruce A. Firth  Andrew R. Swanson  Stuart K. Nicol 《International Journal of Mineral Processing》1979,5(4):321-334

A number of flotation circuits for the recovery of a poorly floating coal were investigated by laboratory batch testing. Analysis of the size and ash distributions of the products and tailings showed that the circuits which would allow an equitable distribution of collector between the coarse and fine size fractions were superior. These circuits were two-stage reagent addition, reflotation of classified tailings and split feed flotation. The reflotation of classified tailings circuit not only gave the best metallurgical performance, it also was the least affected by pulp density variations and imperfect size classification.  相似文献   

Major and trace element relationships in granodiorites and granites from Australia and South Africa     

Peter Kolbe  Stuart Ross Taylor 《Contributions to Mineralogy and Petrology》1966,12(2):202-222

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The electrical conductivity of some hydrous and anhydrous molten silicates as a function of temperature and pressure     

John Satherley  Stuart I. Smedley 《Geochimica et cosmochimica acta》1985,49(3):769-777

Electrical conductivity of the following molten silicate systems (in mol%): 60SiO₂-40Na₂O; 65SiO₂-35Na₂O; 75SiO₂-25Na₂O; 78SiO₂-22Na₂O; 72SiO₂-24Na₂O-4CaO; 66SiO₂-19Na₂O-15H₂O; and an anhydrous and hydrous (4 wt% H₂O) Mt. Erebus lava, have been measured as a function of temperature (to 1000°C) and pressure (to 1.3 kbar). The anhydrous soda-rich melts have a positive pressure coefficient of conductivity to ~200 bars and beyond this pressure the pressure coefficient is small and negative. Addition of water lowers the conductivity and gives rise to a negative pressure coefficient at the highest temperatures. The conductivity of hydrous Mt. Erebus lava passed through a maximum with increasing temperature at constant pressure. These phenomena are interpreted in terms of explanations of similar phenomena found in molten salt and aqueous electrolyte solutions.  相似文献   

A geomagnetic variation study near the Highland Boundary Fault,Scotland     

D.C. Booth  W.F. Stuart 《Earth and Planetary Science Letters》1974,22(4):413-416

Geological effects on geomagnetic variation components are investigated, using a large-scale simple geological structure. Results show that short-period vertical variations in the range 20 sec–10 min can be sensitive to localised inland conductivity anomalies which only have a small effect on the horizontal field.  相似文献   

Reconstructing the historical changes in Daphnia mean size and planktivorous fish abundance in lakes from the size of Daphnia ephippia in the sediment   总被引：3，自引：0，他引：3  

Erik Jeppesen  Jens Peder Jensen  Susanne Amsinck  Frank Landkildehus  Torben Lauridsen  Stuart F. Mitchell 《Journal of Paleolimnology》2002,27(1):133-143

The zooplankton community structure in lakes is highly influenced by size-selective predation by fish, with small zooplankton species dominating at high predation pressure. Remains of cladocerans are preserved in the sediment and may be used to trace historical changes in fish predation. We determined how contemporary data on planktivorous fish were related to the size of Daphnia ephippia (dorsal length) in the surface sediment (0-1 cm) of 52 mainly shallow lakes with contrasting densities of fish and nutrients (TP: 0.002-0.60 mg P l^-1). Density of fish expressed as catch per unit effort, in terms of numbers in multiple mesh-sized gill nets (CPUE_n), decreased significantly with increasing mean size of ephippia. The relationship was improved by adding TP as an independent variable, now explaining 90% of the variation in CPUE_n on the full data set covering lakes in Denmark, Greenland and New Zealand, and 78% if only data on Danish lakes were used. CPUE by weight of planktivorous fish and mean weight of Daphnia in the pelagial during summer were also related to ephippial size. By including contemporary data on established relationships between the sizes of egg-bearing female Daphnia and ephippia, we inferred changes in the CPUE_n, mean size of ephippia-bearing Daphnia and summer mean body weight of Daphnia from ephippial size in four lakes during the past 1-2 centuries. In a hypertrophic lake subject to periodic fish kills, Daphnia mean body weight was high and CPUE_n was low compared with those in two eutrophic lakes, while CPUE_n was low and Daphnia body weight was high in the least eutrophic, clearwater lake. Estimated CPUE_n and Daphnia mean weight in the surface sediment of these four lakes corresponded well with contemporary data. Only small changes in ephippial size with time were observed in the clearwater lake and in one of the lakes that had suffered early eutrophication, while major changes occurred in the two other lakes that had been subjected to a major increase in nutrient input or fish kills. We conclude that Daphnia ephippia preserved in the surface sediments of lakes may be a useful and efficient method to quantify the present-day abundance of planktivorous fish and Daphnia mean size. The method is particularly valid in surveys aimed to give a general picture of the fish stock and the ecological state in a set of lakes in a region rather than a precise estimate for a single lake. Though some evidence is provided, more work is needed to evaluate whether the equations are valid for hind-casting in down-core palaeoecological studies.  相似文献   

Measuring Flume Surfaces for Hydraulics Research Using a Kodak DCS460     

Jim H. Chandler  Koji Shiono  Ponnambalam Rameshwaren  & Stuart N. Lane 《The Photogrammetric Record》2001,17(97):39-61

A critical problem in hydraulics research is accurate measurement of fluvially worked sediments, both in the field and in scaled representations of field situations in laboratory flumes. Such measurement must provide information on individual grain characteristics, and their organisation into structures referred to as bedforms. Existing measurement approaches are based upon mechanical or laser profiling devices, which are both expensive and take considerable time to acquire data, particularly where information is required at very high densities. This paper demonstrates how conventional automated terrain model extraction software, combined with image acquisition using a Kodak DCS460 digital camera, has been effective in generating digital elevation models of complex bed morphology. This has reduced time spent collecting data in the flume and has allowed data collection at much higher spatial and temporal densities. Application of the method is illustrated by research carried out at Hydraulics Research Wallingford. Issues discussed include configuration of photographs and control coordinates; appropriate camera calibration methods; stability of inner orientation of the Kodak DCS460; and accuracies obtained. Comparisons with independent check data reveal that accuracies of ±2.5mm have been achieved using a camera-to-object distance of 4.2 m.  相似文献   

AGRICULTURAL CHEMICAL NEWS     

Stuart Cohen 《Ground Water Monitoring & Remediation》1991,11(3):87-88

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Sea surface wind stress and drag coefficients: The hexos results   总被引：17，自引：1，他引：17  

Stuart D. Smith  Robert J. Anderson  Wiebe A. Oost  C. Kraan  Nico Maat  Janice De Cosmo  Kristina B. Katsaros  Kenneth L. Davidson  Karl Bumke  Lutz Hasse  Helen M. Chadwick 《Boundary-Layer Meteorology》1992,60(1-2):109-142

Turbulent fluxes have been measured in the atmospheric surface layer from a boom extending upwind from the Dutch offshore research platform Meetpost Noordwijk (MPN) during HEXMAX (Humidity Exchange over the Sea Main Experiment) in October–November, 1986. We started out to study eddy flux of water vapour, but discrepancies among simultaneous measurements made with three different anemometers led us to develop methods to correct eddy correlation measurements of wind stress for flow distortion by nearby objects. We then found excellent agreement among the corrected wind stress data sets from the three anemometers on the MPN boom and with eddy correlation measurements from a mast on a tripod. Inertial-dissipation techniques gave reliable estimates of wind stress from turbulence spectra, both at MPN and at a nearby ship. The data cover a range of wave ages and the results yield new insights into the variation of sea surface wind stress with sea state; two alternative formulas are given for the nondimensional surface roughness as a function of wave age.  相似文献