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- Genre: Masters Thesis
Description
Conceptual change has been a large part of science education research for several decades due to the fact that it allows teachers to think about what students' preconceptions are and how to change these to the correct scientific conceptions. To have students change their preconceptions teachers need to allow students to confront what they think they know in the presence of the phenomena. Students then collect and analyze evidence pertaining to the phenomena. The goal in the end is for students to reorganize their concepts and change or correct their preconceptions, so that they hold more accurate scientific conceptions. The purpose of this study was to investigate how students' conceptions of the Earth's surface, specifically weathering and erosion, change using the conceptual change framework to guide the instructional decisions. The subjects of the study were a class of 25 seventh grade students. This class received a three-week unit on weathering and erosion that was structured using the conceptual change framework set by Posner, Strike, Hewson, and Gertzog (1982). This framework starts by looking at students' misconceptions, then uses scientific data that students collect to confront their misconceptions. The changes in students' conceptions were measured by a pre concept sketch and post concept sketch. The results of this study showed that the conceptual change framework can modify students' preconceptions of weathering and erosion to correct scientific conceptions. There was statistical significant difference between students' pre concept sketches and post concept sketches scores. After examining the concept sketches, differences were found in how students' concepts had changed from pre to post concept sketch. Further research needs to be done with conceptual change and the geosciences to see if conceptual change is an effective method to use to teach students about the geosciences.
ContributorsTillman, Ashley (Author) / Luft, Julie (Thesis advisor) / Middleton, James (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2011
Description
Drylands (arid and semi-arid grassland ecosystems) cover about 40% of the Earth's surface and support over 40% of the human population, most of which is in emerging economies. Human development of drylands leads to topsoil loss, and over the last 160 years, woody plants have encroached on drylands, both of which have implications for maintaining soil viability. Understanding the spatial variability in erosion and soil organic carbon and total nitrogen under varying geomorphic and biotic forcing in drylands is therefore of paramount importance. This study focuses on how two plants, palo verde (Parkinsonia microphylla, nitrogen-fixing) and jojoba (Simmondsia chinensis, non-nitrogen fixing), affect sediment transport and soil organic carbon and total nitrogen pools in a dryland environment north of Phoenix, Arizona. Bulk samples were systematically collected from the top 10 cm of soil in twelve catenae to control for the existence and type of plants, location to canopy (sub- or intercanopy, up- or downslope), aspect, and distance from the divide. Samples were measured for soil organic carbon and total nitrogen and an unmanned aerial system-derived digital elevation map of the field site was created for spatial analysis. A subset of the samples was measured for the short-lived isotopes 137Cs and 210Pbex, which serve as proxy erosion rates. Erosional soils were found to have less organic carbon and total nitrogen than depositional soils. There were clear differences in the data between the two plant types: jojoba catenae had higher short-lived isotope activity, lower carbon and nitrogen, and smaller canopies than those of palo verde, suggesting lower erosion rates and nutrient contributions from jojoba plants. This research quantifies the importance of biota on influencing hillslope and soil dynamics in a semi-arid field site in central AZ and finishes with a discussion on the global implications for soil sustainability.
ContributorsAlter, Samuel (Author) / Heimsath, Arjun M (Thesis advisor) / Throop, Heather L (Committee member) / Walker, Ian J (Committee member) / Arizona State University (Publisher)
Created2018
Description
The morphology of mountainous areas is strongly influenced by stream bed incision rates, but most studies of landscape evolution consider erosion at basin scales or larger. The research here attempts to understand the smaller-scale mechanics of erosion on exposed bedrock channels in the conceptual framework of an established saltation-abrasion model by Sklar and Dietrich [2004]. The recirculating flume used in this experiment allows independent control of bed slope, water discharge rate, sediment flux, and sediment grain size – all factors often bundled together in simple models of river incision and typically cross-correlated in natural settings. This study investigates the mechanics of erosion on exposed bedrock channels caused by abrasion of transported particles. Of particular interest are saltating particles, as well as sediment near the threshold between saltation and suspension - sediment vigorously transported but with significant interaction with the bed. The size of these erosive tools are varied over an order of magnitude in mean grain diameter, including a sand of D¬50 = 0.56 mm, and three gravel sizes of 3.39, 4.63, and 5.88 mm. Special consideration was taken to prevent any flow conditions that created a persistent alluvial cover. The erodible concrete substrate is fully exposed at all times during experiments reported here. Rates of erosion into the concrete substrate (a bedrock proxy) were measured by comparing topographic data before and after each experimental run, made possible by a precision laser mounted on a high speed computer-controlled cart. The experimental flume was able to produce flow discharge as high as 75 liters per second, sediment fluxes (of many varieties) up to 215 grams per second, and bed slopes up to 10%. I find a general positive correlation is found between erosion rate and bed slope, shear stress, grain size, and sediment flux.
ContributorsAdams, Mark (Author) / Whipple, Kelin (Thesis advisor) / Heimsath, Arjun (Committee member) / Schmeeckle, Mark (Committee member) / Arizona State University (Publisher)
Created2016
Description
Vinegar is gaining popularity as a natural and proven treatment for common diseases and conditions ranging from high blood pressure to diabetes. While the evidence to support the benefits of vinegar is growing, few studies have considered possible negative consequences. One concern relates to the effect of vinegar on saliva pH and dental erosion. The aim of this study is to explore this relationship as well as unsubstantiated claims that vinegar, although acidic, has an alkalizing effect on the overall body, specifically looking at its effect on resting saliva pH. Healthy adults aged 18-45 were recruited for this trial. Twenty-two participants completed this eight-week, parallel-arm, randomized, double blinded study that looked at the effect that regular consumption of red wine vinegar (two tablespoons taken two times per day before a meal) had on resting salivary pH and dental erosion compared to a control (low dosage vinegar pill taken two times a day before a meal). Resting saliva pH was measured at home using the pH20H application and pH strips at week 0 and 8 of the trial. Erosion was noted using the Basic Erosive Wear Examination (BEWE) by a registered dental hygienist at week 1 and 8 of trial. Results indicate no mean difference in resting salivary pH in either treatment group after eight weeks (p value, 0.49). However, there was a statistical significant mean difference in dental erosion between the VIN and CON group (p value, 0.05). Statistical significance in dental erosion, typically a gradual process, in just eight weeks is a significant finding and warrants concern about long time use of vinegar and dental health. Further exploration into this relationship is needed.
ContributorsAnderson, Summer Lynn (Author) / Johnston, Carol (Thesis advisor) / Whisner, Corrie (Committee member) / Alexon, Christy (Committee member) / Arizona State University (Publisher)
Created2019