8,286 research outputs found

    Investigation of Metal and Organic Contaminant Distributions and Sedimentation Rates in Backwater Lakes along the Illinois River

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    Systematic sub-sampling of sediment cores in sections of uniform thickness is necessary in order to evaluate historic changes in sediment quality, to determine the vertical extent of contamination, and to measure sedimentation rates. With these objectives in mind, fourteen sediment cores were collected during March 2002 using the Illinois State Water Survey vibracorer. Concentrations of metals and total organic carbon were measured using standard techniques. Concentrations of chlorinated pesticides, phenolic compounds, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) were measured by gas chromatography/mass spectrometry (GC-MS). The concentrations of chlorinated pesticides, phenolic compounds and polychlorinated biphenyls (PCBs) were below the method detection limit in all sediment samples analyzed. However, there was a wide range in concentrations of polycyclic aromatic hydrocarbons (PAHs) which were detected in all sediment samples. Also, a wide range of metal concentrations was noted in the sediments evaluated. Lower concentrations of metals were found in the upper 0.5 m of sediment but concentrations were elevated at depths ranging from 1.0 m to 1.5 m. Sedimentation rates were estimated using cesium-137 radiometric dating on 14 vibracores. Sedimentation rates range from < 0.1 to 1.9 cm/yr, with an average of 0.9 cm/yr. These rates are comparable to those reported in previous studies.Illinois Sustainable Technology Centerpublished or submitted for publicationis peer reviewe

    Mobilizing Public Will For Social Change

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    Examines the theory and strategies of "public will" campaigns and offers tangible criteria for their evaluation. It provides a rich inventory of strategies for use in mobilizing the public will through an integration of models of agenda building, social problem construction, issues management, social movements, media advocacy, and social capital. In addition, the paper provides cases and examples of public will campaigns directed at various social problems, along with criteria for evaluating these campaigns at various stages of a social problem's life cycle

    The Domestication and Migration of Zea mays L. in Association with Holocene Climatic Variance

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    Maize is known to have originated in Mesoamerica from which it spread north and south, adapting to many varied climatic and environmental conditions. This study details the origin of the species Zea mays L. The teosinte hypothesis and the concepts of seasonality and scheduling are employed to discuss the domestication of maize by means of human selection. This information is used to highlight the basic circumstances necessary for maize agriculture to be adopted by a human population. Furthermore, climate is examined through the minimum and ideal environmental conditions needed for the successful growth of maize. Environmental cues play a profound role in the phenotypic characteristics a species exhibits; therefore Holocene climactic events are examined in areas with extensive evidence of maize domestication. The minimum requirements for maize growth are compared against the actual conditions during periods of significant climatic change (Little Ice Age, Medieval Warm Period, etc.). Through comparing the ideal versus realized conditions over time, a model for the diffusion of maize from Mesoamerica into North America, with a particular focus on the Southwest and Ohio Valley, is developed

    Measuring situation awareness in complex systems: Comparison of measures study

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    Situation Awareness (SA) is a distinct critical commodity for teams working in complex industrial systems and its measurement is a key provision in system, procedural and training design efforts. This article describes a study that was undertaken in order to compare three different SA measures (a freeze probe recall approach, a post trial subjective rating approach and a critical incident interview technique) when used to assess participant SA during a military planning task. The results indicate that only the freeze probe recall method produced a statistically significant correlation with performance on the planning task and also that there was no significant correlation between the three methods, which suggests that they were effectively measuring different things during the trials. In conclusion, the findings, whilst raising doubts over the validity of post trial subjective rating and interview-based approaches, offer validation evidence for the use of freeze probe recall approaches to measure SA. The findings are subsequently discussed with regard to their implications for the future measurement of SA in complex collaborative systems

    3D printing dimensional calibration shape: Clebsch Cubic

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    3D printing and other layer manufacturing processes are challenged by dimensional accuracy. Several techniques are used to validate and calibrate dimensional accuracy through the complete building envelope. The validation process involves the growing and measuring of a shape with known parameters. The measured result is compared with the intended digital model. Processes with the risk of deformation after time or post processing may find this technique beneficial. We propose to use objects from algebraic geometry as test shapes. A cubic surface is given as the zero set of a 3rd degree polynomial with 3 variables. A class of cubics in real 3D space contains exactly 27 real lines. We provide a library for the computer algebra system Singular which, from 6 given points in the plane, constructs a cubic and the lines on it. A surface shape derived from a cubic offers simplicity to the dimensional comparison process, in that the straight lines and many other features can be analytically determined and easily measured using non-digital equipment. For example, the surface contains so-called Eckardt points, in each of which three of the lines intersect, and also other intersection points of pairs of lines. Distances between these intersection points can easily be measured, since the points are connected by straight lines. At all intersection points of lines, angles can be verified. Hence, many features distributed over the build volume are known analytically, and can be used for the validation process. Due to the thin shape geometry the material required to produce an algebraic surface is minimal. This paper is the first in a series that proposes the process chain to first define a cubic with a configuration of lines in a given print volume and then to develop the point cloud for the final manufacturing. Simple measuring techniques are recommended.Comment: 8 pages, 1 figure, 1 tabl

    High-frequency ultrasonic speckle velocimetry in sheared complex fluids

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    High-frequency ultrasonic pulses at 36 MHz are used to measure velocity profiles in a complex fluid sheared in the Couette geometry. Our technique is based on time-domain cross-correlation of ultrasonic speckle signals backscattered by the moving medium. Post-processing of acoustic data allows us to record a velocity profile in 0.02--2 s with a spatial resolution of 40 μ\mum over 1 mm. After a careful calibration using a Newtonian suspension, the technique is applied to a sheared lyotropic lamellar phase seeded with polystyrene spheres of diameter 3--10 μ\mum. Time-averaged velocity profiles reveal the existence of inhomogeneous flows, with both wall slip and shear bands, in the vicinity of a shear-induced ``layering'' transition. Slow transient regimes and/or temporal fluctuations can also be resolved and exhibit complex spatio-temporal flow behaviors with sometimes more than two shear bands.Comment: 15 pages, 18 figures, submitted to Eur. Phys. J. A

    Information requirements for supersonic transport operation Final report

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    Effects of meteorological parameters and instrument errors on vertical flight performance of supersonic transport

    RECORDS OF THE SUBANTARCTIC FUR SEAL ARCTOCEPHALUS TROPICALIS FROM RODRIGUES AND MAURITIUS, INDIAN OCEAN

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    A juvenile Subantarctic fur seal Arctocephalus tropicalis was recorded on the Indian Ocean island of Rodrigues and two were seen on Mauritius. These records are at least 2 500 km from the closest breeding colony (Amsterdam Island) and are the most easterly by some 1 800 km of all previous records of vagrants of this species.Afr. J. mar. Sci. 25: 403–40
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