https://doi.org/10.33697/ajur.2004.012
https://doi.org/10.33697/ajur.2004.013
Author(s):
C.C. Chancey
Affiliation:
American Journal of Undergraduate Research, University of Northern Iowa, Cedar Falls, Iowa 50614-0150 USA
Analysis of the Merden Lake Esker, Stearns County, Minnesota: A New Interpretation
https://doi.org/10.33697/ajur.2004.014
Author(s):
Aaron C. Hirsch and Larry E. Davis
Affiliation:
Division of Natural Sciences, College of St. Benedict / St. John’s University, Collegeville, Minnesota 56321 USA
ABSTRACT:
A gravel pit in south central Stearns County, Minnesota exposes sand and gravel of the Merden Lake esker which is thought to have been deposited by a subglacial stream associated with the Wisconsinan-aged Superior Lobe of the Laurentide ice sheet. An analysis of these sediments was conducted from samples collected through a vertical trench on an east-facing exposure of the gravel pit. A total of 12 distinct stratigraphic horizons were recognized. Each horizon was described in terms of overall color, grain size, and lithology, carbonate content, and sedimentary structures. A total of 436 clasts (>3 cm) were collected for lithology studies. Trench samples were collected across each horizon for grain size sieve analysis. Clasts were dominated by basalt (37.6%), granite (28.2%), gabbro (14.5%), quartzite (6.2%), diorite (3.5%), mica schist (3%), and andesite (1%). Minor components consisted of pisolitic claystone, shale, sandstone, limestone, dolostone, ironstone, bauxite, quartz, agate, and amethyst. The sedimentology provides an overall color of yellowish-orange to brown. Many of the large clasts (>5 cm) contained a rind of calcareous-cemented course sand. Several large (18-35 cm) armored clay balls were collected from the basal horizon. Grain size ranged from boulders (up to 37 cm in diameter) to clays. Average cobble size was 10.48 cm. The dominant grain size through the trench was 1-2 mm. Sedimentary structures included graded beds, minor cross bedding, and imbrication. Superior Lobe lithologies are dominated by red volcanics and sedimentary rocks from the Middle Proterozoic Keeweenawan Superior Group and have an overall brown to reddish-gray appearance. Rainy (Wadena) Lobe lithologies are dominated by Precambrian igneous and metamorphic rocks from southwest Ontario and northwest Minnesota and have an overall yellowish to yellow-brown appearance. Sedimentological analysis of the Merden Lake esker indicates its characteristics are more consistent with subglacial stream deposition within the Pierz Sublobe of the Rainy Lobe of the Laurentide ice sheet.
Numerical Investigation of a Class of Nonlinear Schrödinger Equations
https://doi.org/10.33697/ajur.2004.015
Author(s):
Christopher Ventura
Affiliation:
Pacific University, 2043 College Way, Forest Grove, Oregon 97116
ABSTRACT:
This paper numerically investigates the space-localized spherically symmetric, stationary, and singularity-free solutions of the Nonlinear Schrödinger equation when the nonlinearity is a step function. Previously no-node solutions have been obtained analytically. Here, it is shown that localized stationary solutions with one node and two nodes also exist.
Interactions among Land, Water, and Vegetation in Shoreline Arthropod Communities
https://doi.org/10.33697/ajur.2004.016
Author(s):
Randall D. Willoughby and Wendy B. Anderson
Affiliation:
Department of Biology, Drury University, 900 N. Benton Avenue, Springfield, Missouri 65802 USA
ABSTRACT:
We investigated the distribution and abundance of terrestrial spiders as a function of their distance from a body of water and the structure of vegetation that would provide suitable habitat. We hypothesized that spiders would prefer to be located near the water to catch abundant aquatic emergent insects. In Montana along the Upper Missouri River, and in Missouri at various locations around Table Rock Lake, transect lines were run from the water’s edge to 25 meters inland. At five-meter intervals, in one square meter plots, the number of spiders, number of prey and type, and vegetation type and structure were recorded. In both Montana and Missouri, spider distribution was more strongly associated with available vegetation structure than with distance from shore. This suggests that, although prey availability may be important for predator distribution, suitable habitat is as strong or stronger a determinant for web building spiders.
Application of Green Chemistry: A Miniaturized Procedure for Analysis of Dissolved Phosphate
https://doi.org/10.33697/ajur.2004.017
Author(s):
Nadia Kamal and Clay Runck
Affiliation:
Department of Biological Sciences, Benedictine University, 5700 College Road, Lisle, Illinois 60532 USA
ABSTRACT:
The objective of this study was to determine if the volume of sample used for analysis of soluble reactive phosphate (SRP) could be reduced from 100 mL (as per a widely used standardized procedure) to 50 or 10 mL to reduce the amount of hazardous waste generated from routine analysis of SRP in water samples from rivers, streams, and ponds in an urbanized landscape, in accordance with the principles of “green chemistry” and the Pollution Prevention Act of 1990. The ascorbic acid-molybdate blue method of Murphy and Riley (1962) was used to determine the concentration of SRP in water samples collected from the East Branch of the DuPage River and from two ponds on the campus of Benedictine University. Mean concentration of SRP determined using a 10 mL sample volume of DuPage River water (x = 1,051 μg PO4-P/L) was significantly greater than the 100 and 50 mL sample volumes, which were not significantly different from each other (x = 1,002 μg PO4-P/L); however, the difference in SRP concentration between 10 mL and 100 and 50 mL sample volumes was only 5%. There was no significant effect of sample volume on SRP concentration for slough or storm water pond samples, but these two pond systems had a low SRP concentration (<3 μg PO4-P/L). The relationship between absorbance and SRP concentration in the ascorbic acid-molybdate blue method was examined between 0 and 2,000 μg PO4-P/L; absorbance was asymptotic between 500 and 2,000 μg PO4-P/L. The results of this study show that the sample volume for analysis of SRP in DuPage River water with the ascorbic acid-molybdate blue method can be reduced by 50% (i.e., reduced from 100 mL to 50 mL) without loss of accuracy, but that samples must be diluted to reduce the concentration of SRP to within the limits of the procedure. The reduction in sample volume represents a substantial reduction in the volume of hazardous waste that is generated, and the overall cost per sample, for routine analysis of SRP in the DuPage River.
Improvements in Latent Semantic Analysis
https://doi.org/10.33697/ajur.2004.018
Author(s):
Ryan Lloyd and Cheri Shakiban
Affiliation:
Department of Mathematics, University of St. Thomas, St. Paul, Minnesota 55105-1079 USA
ABSTRACT:
This paper proposes and examines modifications for the method of Latent Semantic Analysis (LSA). Several new local and global weight functions, along with normalization routines, are disclosed. Changes in the general structure of LSA are discussed. An application of LSA, in which the method is used to filter advertisements in e-mail, proves the worthiness of the advancements.