15th Denman Undergraduate Research Forum (2010)

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    Spatial and Temporal Variations of Water Quality in a Recently Urbanized Watershed in Central Ohio
    (2010-05-12) Volk, John; Lyons, Berry
    Hellbranch Run drains land near Columbus, Ohio that was subject to rapid conversion from agricultural to urban land use during the 1990s. The stream is a tributary to Big Darby Creek, a national scenic river that is valued for its biological diversity and health. Headwater areas in the Hellbranch Run watershed have been channelized, and the stream’s water quality is threatened from nutrient enrichment caused by agricultural runoff. In recent decades, State and private organizations have funded and implemented stream remediation within the Hellbranch Run watershed. The objective of this study was to synthesize historically measured flow and solute concentrations to identify trends in loading of select water quality constituents to Big Darby Creek and also investigate spatial and seasonal variations of water quality within the Hellbranch Run watershed. Water samples were collected from four sites within the Hellbranch Run watershed, bimonthly for one year (Nov. 2009 to Nov. 2010) for n=84 samples. Sites represent headwater areas with differing land use. Sampling involved filtering, measuring temperature, pH, and conductivity in situ and laboratory analyses of water samples were for total suspended solids (TSS), dissolved major ions, and major nutrients: nitrate + nitrite-(N), ammonium-N, total dissolved N, phosphate and total dissolved P (TDP) concentrations. Results show N, TDP and Cl- having high concentrations: N median 1.4 mg/L (~0.0 – 4.3 mg/L), TDP median 398 ug/L (67 – 1,773 ug/L), and Cl- median 99.5 mg/L (40.3 – 873.7 mg/L). Geographic information systems were used to investigate changes in land cover within the watershed from 1992–2006. The watershed of Clover Groff Ditch one of two major tributaries to Hellbranch Run, underwent substantial conversion from agricultural land to urban and showed a corresponding decrease in major nutrient and ion concentrations relative to other headwater areas in the Hellbranch Run watershed. Hamilton Ditch, the other major tributary that largely drains agricultural land, had the highest concentrations of all nutrients and major ions. Seasonal shifts exhibited a strong control on N with highest concentrations in the winter and lowest in the summer. TSS concentrations were highest immediately downstream of the two ditches. Historical flow and measured dissolved N, TP (unfiltered), Cl-, and TSS were used to estimate daily loads using the USGS computer program LOADEST. The resulting time series showed a decreasing trend in N between water years 1993 and 2010, which could be related to urbanization and stream remediation efforts that occurred over the time period.
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    Interactions of Heart Rate Variability and Gender on Cognitive Performance
    (2010-05-12) Williams, DeWayne; Plaskett, Sean; Thayer, Julian
    The study of reaction time to attention evoking stimuli is one to the oldest, yet consistently used paradigms in cognitive psychology. One variation of this paradigm is the Simon Effect task, during which individuals must respond to a stimuli that is consistent (congruent) or inconsistent (incongruent) with positioning. Interestingly, research has suggested that an index of cardiovascular health and flexibility (Heart Rate Variability|HRV) may predict performance on cognitive tasks such as the Simon Effect. This work suggests that communication between the heart and brain may serve much more complex functions than just heart rate regulation. In the present study we sought to support this notion using this attentional task. We predicted that individuals with higher resting HRV would show better performance on the cognitive task. Continuous heart rate data was collected using an exercise heart rate monitor (i.e. Polar watch) from 18 participants who completed a resting baseline period during which they sat quietly in a laboratory room, the Simon Task, and a recovery period. HRV was calculated for the baseline period of each participant; reaction times were computed for congruent/incongruent trials of the Simon Task. Means were compared using a factorial Analysis of Variance, First obtaining the median value for resting HRV and classified participants as either High HRV or Low HRV at baseline based on their position above or below the median; second, looking for potential gender differences in task performance. Analyses revealed a significant interaction between gender and HRV groups; males with High baseline HRV displayed slower mean reaction times whereas High HRV females exhibited faster reaction times. This pattern was reversed in the Low HRV groups for both genders. Our findings are partially consistent with previous research and further suggest that gender may be an important factor in using HRV as a predictor of cognitive performance.
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    Diffusion of spins in a strongly spatially varying local magnetic field
    (2010-05-12) Labanowski, Dominic; Hammel, Chris
    In recent years, the field of spintronics has gained immense interest in the research community. In conventional computing, data is encoded by turning electrical signals on and off; with spintronics, data is encoded with electron spin, allowing for new electronic devices that can move more data at reduced voltages. To further this field, an understanding of spin behavior at the local level is necessary. In my group, magnetic force detection experiments are being used to understand these local phenomena. In these experiments, a micro-magnetic probe couples to the spins generated in a gallium arsenide sample. The sample in these experiments is a 2 micron thick n-GaAs (3e16 cm-3 Si doped) epitaxial membrane. Spins were injected into the membrane over a 10 micron region using standard optical pumping techniques. My presentation focuses on numerical analysis of the spin diffusion equation to better understand the effects of the local magnetic field generated by the probe tip. These simulations provide spatial maps of spin polarization. They also provide information concerning the procession of the spins about an external transverse magnetic field. These were simulated for the conditions experienced by the sample in the experiment. A key result is that the presence of localized, strongly inhomogeneous magnetic fields leads to spatial features in the spin distribution smaller than the injection spot size. These changes in the spatial maps and spin precession due to an external magnetic field as a function of the magnetic tip position can help obtain information regarding spin diffusion, precession, and relaxation with enhanced spatial resolution. The strong field gradients produced by local spin features can also increase the signal in magnetic force microscopy of the sample.
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    Utilizing Doppler Ultrasound to Detect Blood Flow within the Median Nerve
    (2010-05-12) Zale, Kathryn; Evans, Kevin
    Ultrasound technologists are at an increased risk for developing work-related musculoskeletal disorders, such as carpal tunnel syndrome (CTS). CTS is characterized by inflammation of the median nerve within the carpal tunnel and a literature review supports that hypervascularization is seen within the nerve sheath. Currently, only invasive procedures such as nerve conduction testing and dynamic contrast magnetic resonance imaging are utilized in diagnosing CTS. This feasibility study was the first of its kind to detect and quantify arteriole blood flow within the median nerve with spectral and power Doppler ultrasound. Five ultrasound technologists had their wrists scanned with a hand carried ultrasound unit over a 10-week period both before and after scanning neonatal heads. The results showed the qualitative measure of blood flow with color Doppler was consistently seen on each scanning session, whereas the quantitative measure with spectral Doppler was obtained only half of the time. The pre and post measures of peak systolic (PS) velocity and end diastolic (ED) velocity were not statistically significant, but showed very low blood flow on average - PS = 4.36 cm/s and ED = 0.76 cm/s. While these measures were not consistently obtained, this study proved acquiring quantitative blood flow within the median nerve with spectral Doppler ultrasound is feasible. There were many limitations of this study and key among these was the short evaluation, nested inside a larger work day. This was a feasibility study; therefore a more rigorous controlled study is needed to find the true sensitivity of spectral Doppler ultrasound to quantify blood flow in the median nerve. A longitudinal and comprehensive data collection is needed that reflects the entire work load. Therefore, this research underlines the importance of understanding the related physiology and technique to find a noninvasive alternative in diagnosing CTS.