• Invasive plants and pollination of Alaskan berry species: integrating ecology and education

      Spellman, Katie Villano; Mulder, Christa; Wagner, Diane; McGuire, A. David; Conner, Laura; Carlson, Matthew (2015-05)
      A rapidly changing climate and human disturbance patterns have accelerated the spread of invasive plants species in Alaska. Non-native plant invasions can disrupt pollinator services to native plants and have the potential to impact the pollination and fruit set in berry species important for subsistence harvest. My dissertation aims to address the dual need for greater understanding of the impacts of invasive plants on pollination of berry species in boreal ecosystems and the need for research on education strategies that best prepare Alaskans to respond to the issue. I integrate an ecological field experiment, a citizen science program where data is used to validate phenology models derived from heraium data, and an invasive plants education experiment testing the effects of a metacognitive learning intervention to provide multiple perspectives that inform the management of invasive plants in Alaska. The ecological field experiment found that invasive Melilotus albus acts as a magnet species for pollinators, which increased seed production in Vaccinium vitis-idaea, slightly decreased pollination in Rhododendron groenlandicum, and had no detectable interactions with Vaccinium uliginosum. The impact M. albus had on R. groenlandicum changed with distance from the invasive plant patch, but the impact on V. vitis-idaea did not. Using data from a statewide citizen science program monitoring the phenology of these species, I found that herbarium-based phenology models were valid for assessing relative shifts in phenology of these species across Alaska. Employing the research on M. albus and the berry species as a test case, I found that students who received the metacognitive learning intervention show long-term improvement in metacognitive skills compared to students in the control group, but that the groups did not differ in their ability to apply resilience thinking skills to the environmental problem-solving. I synthesized social-ecological resilience and education research to investigate how citizen science and metacognitive learning could contribute to the capacity of Alaskans to respond to social-ecological change. Together, the ecology and education research presented here provide diverse perspectives on how to best manage and build the human capacity to manage M. albus near subsistence plant species.
    • Inversion of focal mechanism data for the directions of stress near Redoubt Volcano, Alaska

      Sánchez-Aguilar, John Jairo; McNutt, Stephen R.; Christensen, Douglas H.; Gardner, James E.; Moran, Seth C.; Wyss, Max (2000-12)
    • Investigating A Yup'Ik Immersion Program: What Determines Success?

      Green, Jean Renee; Coles-Ritchie, Marilee (2010)
      This research stems from my connectedness to a particular village, which will be referred to as Naparyaraq1. Unlike the majority of research on Alaska Native language issues, which primarily are from the point of view from an outsider, this research is unique in that my role as a community member has allows me an insider perspective of our Yup'ik Immersion Program. When dealing with Indigenous language issues, it is important that the impetus for change and improvements come from the local people. The primary goal of the Naparyaraq Immersion Program resulted from the communities desire to create change Community members wanted to keep the Yup'ik language alive. Growing up in Naparyaraq and my familiarity with the language issues has also driven me to be a personal participant in this change. Using focus groups, interviews, classroom observations, and field notes, the main goal of this Master's thesis is to inform the teachers and school community of the Naparyaraq Yup'ik Immersion Program in order to continue to help make improvements. Some of the issues which are addressed in this research include information related to: language use, success, training, language use at home, support, success, quality staff, assessment, need for teacher collaboration, and curriculum. 1Naparyaraq is a pseudonym. All names and places in the thesis are pseudonyms.
    • Investigating ancient bison migration in Alaska: a bottom up approach using isotopes

      Funck, Juliette Marie; Wooller, Matthew; Druckenmiller, Patrick; Hundertmark, Kris; Ruether, Joshua (2020-05)
      Once abundant in the Arctic, bison (Bison bison) declined almost to extinction in the North but have subsequently been reintroduced into Alaska. The predecessors of these modern bison were the ancient steppe bison (Bison priscus), which were abundant throughout the Northern Hemisphere before their extinction during the Holocene. This thesis investigates the ecology and landscape-use of both the present-day wood bison (Bison bison athabascae) and the ancient steppe bison in Alaska using stable isotopes, among other methods. The stable carbon and nitrogen isotope compositions of animal tissues are traditionally used to investigate diet. However, this thesis uses the isotope composition of tail hairs from present day wood bison as a proxy for their nutritional stress. Nutritional stress of some wood bison appears to be influenced not only by food shortage during hard seasons, but also due to long-distance mobility. This insight provides a key to understanding the challenges of reintroduction of the species into Alaska today, and can also be applied to understand the nutritional stress and cost of dispersal by ancient animals. Whereas the mobility of present-day bison can be tracked using sophisticated satellite tracking technologies, studies of the paleo-mobility of ancient bison rely on isotopic markers such as strontium and oxygen isotope ratios preserved in their teeth. To aid this approach using isotopic geolocation, this thesis creates a map of bioavailable strontium modeled and based on strontium isotope composition of present-day rodent teeth from across Alaska. It then compares this map, together with an existing oxygen isotope map of precipitation in Alaska, with the strontium and oxygen isotopes preserved in a suite of ancient bison from Northern Alaska. This comparison brings to light some of the major habitation regions used by Bison on the North Slope of Alaska over the last ~50,000 years. Finally, these findings subsequently contribute to a detailed paleoecological investigation of a mostly articulated and complete ancient steppe bison found on the North Slope of Alaska. This final study reveals the life-history of an individual bison that dispersed from the coastal plain to the foothills of the Brooks Range early in his life, and shows that the trip was nutritionally costly. This information is combined with a suite of other paleoecological methods to provide a vivid life history of this ancient bison. We introduce new methodologies for studying these ancient animals that seek to bridge the gap between how we study present-day and the past.
    • Investigating marine particle distributions and processes using in situ optical imaging in the Gulf of Alaska

      Turner, Jessica S.; McDonnell, Andrew; Johnson, Mark; Islas, Ana Aguilar (2015-12)
      The Gulf of Alaska is a seasonally productive ecosystem surrounded by glaciated coastal mountains with high precipitation. With a combination of high biological production, inputs of suspended sediments from glacial runoff, and contrasting nutrient regimes in offshore and shelf environments, there is a great need to study particle cycling in this region. I measured the concentrations and size distributions of large marine particles (0.06-27 mm) during four cruises in 2014 and 2015 using the Underwater Vision Profiler (UVP). The UVP produces high resolution depth profiles of particle concentrations and size distributions throughout the water column, while generating individual images of objects >500 μm including marine snow particles and mesozooplankton. The objectives of this study were to 1) describe spatial variability in particle concentrations and size distributions, and 2) use that variability to identify driving processes. I hypothesized that UVP particle concentrations and size distributions would follow patterns in chlorophyll a concentrations. Results did not support this hypothesis. Instead, a major contrast between shelf and offshore particle concentrations and sizes was observed. Total concentrations of particles increased with proximity to glacial and fluvial inputs. Over the shelf, particle concentrations on the order of 1000-10,000/L were 1-2 orders of magnitude greater than offshore concentrations on the order of 100/L. Driving processes over the shelf included terrigenous inputs from land, resuspension of bottom sediments, and advective transport of those inputs along and across the shelf. Offshore, biological processes were drivers of spatial variability in particle concentration and size. High quantities of terrigenous sediments could have implications for enhanced particle flux due to ballasting effects and for offshore transport of particulate phase iron to the central iron-limited gyre. The dominance of resuspended material in shelf processes will inform the location of future studies of the biological pump in the coastal Gulf of Alaska. This work highlights the importance of continental margins in global biogeochemical processes.
    • Investigating The Retention Of Bright And Dark Ejecta From Small Rayed Craters On Mars

      Calef, Fred J., Iii; Herrick, Robert R. (2010)
      Impact cratering is one of the principal geologic processes operating throughout the solar system. On Mars, small rayed impact craters (SRC) form continuously and randomly on the surface. Ejecta retention, the timespan and ability of excavated ejecta to remain in place around a crater rim, records a lineage of recent surface processes. However, the timescales under which small rayed craters are produced and their origin, whether terrestrial or cosmic, plays an important role in further investigating surface processes and possible recent climate variations. By examining thousands of randomly chosen panchromatic images from the Mars Orbiter Camera Narrow Angle (MOCNA) camera, a population of 630 SRC was catalogued across three equatorial and two polar regions on Mars. The survey of MOCNA images also revealed intriguing Enigmatic Linear Features (ELFs) in the northern hemisphere of Mars, which a short side study revealed to be a unique form of dust-devil track. From statistically examining several physical parameters, dust deposition and periglacial erosion were found to be the major factors affecting ejecta retention for the SRC. SRC morphology revealed ejecta retention sequences that followed four stages of ejecta retention from the initial impact to eventual erasure from the surface. By reconstructing the current cratering rate from estimates of atmospheric filtering, it was possible to calculate the ejecta retention age across Mars. In general, SRC ejecta are retained on the surface for <100 ka. Based on ejecta morphology and retention age estimates, a possible shift from depositional to erosional processes just south of the Martian equator is suspected to have occurred within this timeframe.
    • Investigation and development of a mathematical model for the oxidation of cyanide in the INCO SO₂/O₂ process

      Oleson, James L. (2003-12)
      The purpose of this study was to develop a mathematical model to describe the oxidation of cyanide with SO₂ as proposed in the INCO process. This research employed a direct method for measuring the change in cyanide concentration with respect to time as affected by varying concentrations of SO₂ and copper and pH. This model may be applicable in determining optimum conditions in a process well known and used in the mining industry.
    • An investigation into the cold heavy oil production with sand process using synthetic cores and designed experiments

      Narayan, Arya; Awoleke, Obadare; Ahmadi, Mohabbat; Hanks, Catherine; Liu, Jenny (2016-05)
      This study deals with the development of a methodology for making low compressive strength cores used in an experimental investigation of the Cold Heavy Oil Production with Sand (CHOPS) process. An experimental setup was designed and built to investigate the effect of rock compressive strength as well as flow parameters, such as oil viscosity, net and total confining pressure, and injection rate, on core permeability. The approach was to optimize the value of a response variable by changing the values of the affecting factors. Sand blends were prepared by varying the ratios of aggregate, cementing material and water to prepare synthetic cores. An experimental unit was built to simulate wormhole propagation during the CHOPS process, where oil, at an ambient temperature, was injected into 2-inch × 4-inch cores at varying rates of 0.5–10 ml/min under differential confining pressures of 500 and 1000 psia. The pressure drop across the core was monitored and recorded throughout the process. When non-swelling clay is used as a cementing material compared with actual cement to make synthetic core, the compressive strength of the samples falls dramatically by 64%. Two factors were considered in the coreflood experiments: Oil Viscosity (370 and 690 cp) and Injection Rates (0.5 and 3 ml/min) at a net confining pressure of 500 psia, below the compressive strength of the core. It is hypothesized that injecting oil of different viscosities at different rates affects the internal structure of the core in different ways (there is fluid-rock interaction) and thus, at lower pore volumes of injection, the permeability of the core for high viscosity oil is almost 11.2% greater than for low viscosity oil. Also, design of experiment approach was used and regression model was developed for permeability of core based on values recorded at specific pore volumes injected for different injection rates and oil viscosities. It was found that at a constant confining pressure for all rates and at lower pore volumes injected, 99.8% of the variance in permeability can be explained by oil viscosity, injection rate and their interaction. At higher pore volumes injected, the variance in permeability that can be explained by oil viscosity, the injection rate and their interaction is only 40.63%.
    • An investigation into the effectiveness of simulation-extrapolation for correcting measurement error-induced bias in multilevel models

      Custer, Christopher (2015-04)
      This paper is an investigation into correcting the bias introduced by measurement errors into multilevel models. The proposed method for this correction is simulation-extrapolation (SIMEX). The paper begins with a detailed discussion of measurement error and its effects on parameter estimation. We then describe the simulation-extrapolation method and how it corrects for the bias introduced by the measurement error. Multilevel models and their corresponding parameters are also defined before performing a simulation. The simulation involves estimating the multilevel model parameters using our true explanatory variables, the observed measurement error variables, and two different SIMEX techniques. The estimates obtained from our true explanatory values were used as a baseline for comparing the effectiveness of the SIMEX method for correcting bias. From these results, we were able to determine that the SIMEX was very effective in correcting the bias in estimates of the fixed effects parameters and often provided estimates that were not significantly different than those from the estimates derived using the true explanatory variables. The simulation also suggested that the SIMEX approach was effective in correcting bias for the random slope variance estimates, but not for the random intercept variance estimates. Using the simulation results as a guideline, we then applied the SIMEX approach to an orthodontics dataset to illustrate the application of SIMEX to real data.
    • Investigation of a tensile cycloidal rotor and cam cyclic pitching mechanism

      Elfering, Kelsey H. (2012-08)
      A cycloidal rotor is characterized by an airfoil span parallel to the axis of rotation. A tensile cycloidal rotor places the airfoils under tensile forces only, thereby attempting to utilize the inertial forces on the rotor to minimize airfoil deflection and overall weight. A prototype rotor was built that meets the micro air vehicle (MAV) size constraint of 15.24 centimeters (6 inches). A new cam path design was used as a pitching mechanism, which reduced overall design weight and mechanical power requirements, and allowed for curved flat plate airfoils and angled airfoil structural supports. The cycloidal rotor was designed to pitch on both sides of the airfoils in an effort to reduce the axial force that was previously observed in mechanisms that pitch straight airfoils using an offset four bar linkage on only one side. The radial and axial strains were measured to determine the forces on the rotor, and compared well with a finite element simulation. The power-to-thrust ratio increased with RPM, which is in contradiction with theoretical rotor predictions. This indicated there are likely inefficiencies due to friction, which is supported by the measured non-zero power requirement at zero RPM.
    • Investigation Of Auroral Hiss Observations On The Ground: Application To Remote Sensing Of Auroral Magnetosphere

      Harikumar, Jayashree; Sonwalkar, Vikas; Hawkins, Joseph; Sentman, Davis; Olson, John (2001)
      Observed both on the ground at high latitudes and on spacecraft in the auroral zone, auroral hiss (AH) emissions (~1 kHz to ~1 MHz) are intense electromagnetic emissions emitted from the auroral region. Standard whistler mode propagation theory in a smooth magnetosphere predicts that AH generated at large wave-normal angles along the auroral field lines by Cerenkov resonance cannot penetrate to the ground. This thesis presents a new mechanism of AH propagation to the ground in which presence of density depletions along the field lines in the auroral zone and meter-scale density irregularities at altitudes <5000 km at high latitude permits the AH propagation to the ground. In the proposed mechanism AH generated at high altitudes (>5000--20,000 km) propagates to lower altitudes (<3000--5000 km) in two modes, the ducted mode and the non-ducted mode, with large wave-normal angles. At altitudes <5000 km meter-scale irregularities scatter the hiss into electrostatic waves with large wave-normal angles that are reflected into the magnetosphere and electromagnetic waves with small wave-normal angles that can penetrate to the ground. The AH propagation model proposed in this thesis also explains the spectral characteristics of AH including the upper and lower frequency cutoffs, the dispersion of AH, the location of ionospheric exit points of AH with respect to visible aurora, and the 2--5 orders of magnitude difference in the power spectral density ratio measured on satellites versus ground. The new understanding of AH permits the determination of AH source region, energetic electron parallel resonance energy, and cold plasma electron concentrations along field lines. Analysis of AH spectra, recorded at South Pole (July 09, 1996 0005 UT), using the model developed in this thesis shows that: (a) AH source region altitude for frequencies 7--9 kHz should be >16,000 km while for frequencies 12--20 kHz it should be <8000 km, (b) parallel resonance energy of the energetic electrons generating the frequencies should be <1 keV, and (c) cold plasma electron concentration along the field line Lambda = 79� should be ~100 el cm-3 at 12,740 km altitude.
    • Investigation of CO₂ sequestration options for Alaskan North Slope with emphasis on enhanced oil recovery

      Patil, Santosh Bramhadev (2006-08)
      Carbon dioxide (CO₂), the main component of greenhouse gases, is released into the atmosphere primarily by combustion of fossil fuels like coal and oil. Due to a conspicuous lack of any CO₂ sequestration studies for Alaskan North Slope (ANS), the study of CO₂ sequestration options will open new avenues for CO₂ disposal options, such as viscous oil reservoirs and coal seams, on the ANS. This study focuses on the investigation of CO₂ storage options by screening ANS oil pools amenable to enhanced oil recovery, evaluating phase behavior of viscous oil and CO₂ mixture, and simulating enhanced oil recovery by CO₂ flooding, and migration of CO₂ in saline aquifer. Phase behavior studies revealed that CO₂ gas was partially miscible with West Sak, at the pressure closer to the reservoir pressure. Compositional simulation of CO₂ flooding for a five-spot West Sak reservoir pattern showed an increase in percent recovery with an increase in pore volume injected, but at the expense of an early breakthrough. Sensitivity analysis of CO₂ flooding project was found to be strongly dependent on the variables such as oil price and discount rate. Investigation of supercritical CO₂ injection in saline formation didn't increase temperature in the permafrost region.
    • An investigation of environmental variables affecting concentrations of polycyclic aromatic hydrocarbons in eastern Alaska

      Howe, Timothy S. (2000-05)
      Analytical methods for determining polycyclic aromatic hydrocarbon (PAH) concentrations in spruce needles were developed and evaluated. Concentrations of four PAHs (phenanthrene, anthracene, fluoranthene and pyrene) were determined in spruce needles collected near Eastern Alaska roadways. These needle concentrations were used to develop multivariate models that described the influence of climate and geographical variables on concentrations. These variables included latitude, longitude, radial distance from urban site, elevation, temperature, precipitation, ecosystem type, tree species, non-volatile extractable content of needles, and forest fire impact. The models show that three possible sources of PAHs exist in eastern Alaska, urban sites (Fairbanks, Anchorage and Valdez), ocean air, and forest fires. Distribution of PAHs away from these sources is strongly correlated with elevation. The general trend shows that PAH concentrations increase as elevation and proximity to sources decrease.
    • Investigation of North Pacific sea ice anomalies in the context of atmospheric and oceanic variability

      Tivy, Adrienne (2001-08)
      This study investigates the main mode of variability in North Pacific sea ice and examines the relationship between sea ice concentration and northern hemispheric climate variability for the period 1968-1997. Through empirical orthogonal function (EOF) analysis, correlations, and composite analysis, it was found that the seesaw pattern (first EOF of wintertime sea ice concentrations) between ice concentrations in the Bering Sea and the Sea of Okhotsk, generally used to characterize North Pacific sea ice, does not adequately address variability in the Sea of Okhotsk. Relationships between the sea ice dipole and the large-scale circulation were investigated and were found to change with the 1977 and 1989 regime shifts in the North Pacific climate. Before 1977 the sea ice dipole is strongly related to tropical variability while after 1977 the dipole is more strongly related to mid-latitude variability.
    • Investigation of novel secondary metabolites of colophospermum mopane

      Englund, Brian Michael (2005-05)
      Labdanes are a large and important class of diterpenes. Colophospermum mopane seems to be a source of 'primitive' 9, 13-epoxylabdanes. The structures of these compounds are 'missing links' in the biogenesis of 9, 13-epoxylabdanes. This research reports a new compound extracted from the seeds of C. mopane. The structures of this compound has been completely elucidated by NMR spectroscopy, and the stereochemistry of the compound supports predictions based on biosynthetic arguments. Furthermore, this thesis also corrects NMR assignments previously reported by another group.
    • Investigation of phase behavior and reservoir fluid properties in support of enhanced oil recovery of Alaska North Slope (ANS) viscous oils

      Alurkar, Kaustubh D. (2007-12)
      Declining light oil production on Alaska North Slope (ANS) has attracted oil producers to develop viscous oil resources of ANS that range between 20 to 25 billion barrels. These oils are viscous, flow sluggishly in the formations, and are difficult to transport through unconsolidated formations and are hard to produce by conventional methods. Viscous oil recovery entails neatly designed enhanced oil recovery processes and the success of these processes is critically dependent on accurate knowledge of phase behavior and fluid properties of these oils under variety of pressure and temperature conditions. An experimental study was conducted to quantify the phase behavior and physical properties of viscous oils from ANS. The oil samples were compositionally characterized by simulated distillation technique, constant composition expansion and differential liberation tests were conducted on these samples. Experimentally studied phase behavior and reservoir fluid properties were modeled by using the Peng-Robinson Equation-of-State (EOS). The Peng-Robinson EOS was tuned with experimental data to predict the phase behavior, accurately. Widely used corresponding state viscosity model predictions deteriorate when applied to heavy oil systems due to use of ultra-light methane as a reference compound. Therefore, a semi empirical approach (Lindeloff model) was adopted for modeling the viscosity behavior. Viscosity behavior of degassed ANS viscous oils was correlated to their temperature and molecular weight. Integration of this correlation into the Lindeloff model resulted in accurate viscosity predictions for viscous oils under reservoir conditions.
    • An investigation of soil-plant and plant-animal mineral nutrition landscapes of agricultural areas in the Fairbanks and Delta Junction regions of Interior Alaska

      Andrews, Robin N. (2004-05)
      I attempted to identify biologically limiting minerals and assess mineral variability by collecting soil and plant samples in June, July, and August from 14 bromegrass fields and adjacent woodlands, in the Fairbanks and Delta Junction regions. Soil extractable P, K, Ca, Mg, Al, B, Cd, Co, Cr, Cu, Fe, Mn, Pb, Zn, NO⁻³ and NH⁴ as well as pH and organic matter content were measured at three depths. Bromus inermis, Calamagrostis canadensis, Epilobium angustifolium and Salix alaxensis were analyzed for N, P, K, S, Ca, Mg, Al, B, Cd, Cu, Fe, Mn, and Zn. Plant sample variability was assessed by species, date, and location. Mineral content of plants and soils among locations was highly variable with proximate sites showing little similarity. Local differences seemed more important than regional variation in determining soil and plant mineral abundances. Plant mineral content was highly affected by species, date, and location. With the exception of magnesium, plant mineral content was generally not correlated with extractable soil minerals. In most cases, organic matter content and pH were generally not correlated with plant mineral content. Plants, in these regions, may be limited by sulfur, magnesium, and boron availability. High levels of manganese and cadmium in some plant species and low levels of copper and possibly zinc in late season forages may negatively affect herbivores.
    • Investigation of strongly ducted infrasonic dispersion using a vertical eigenfunction expansion of the Helmholtz equation in a modal broad band acoustic propagation code

      Edon, Robert Alexander; Olson, John V.; Fee, David E.; Szuberla, Curt A. (2015-12)
      This study investigates an infrasound propagation model created by the National Center for Physical Acoustics (NCPA) which is applied to atmospheric data with a strong temperature inversion in the lower atmosphere. This temperature inversion is believed to be the primary cause of a dispersed infrasonic signal recorded by an infrasound sensor array located on the Southern California coast in August, 2012. The received signal is characterized by initial low frequency content followed by a high frequency content tail. It is shown the NCPA model is hindered by limited atmospheric data and no ground truth for the source function which generated the received signal. The results of the NCPA model are shown to not reproduce the recorded signal and provide inconclusive evidence for infrasonic dispersion.
    • Investigation Of The Allosteric Modulators Desformylflustrabromine And 4-(2-Hydroxyethyl)-1-Piperazineethanesulfonic Acid (Hepes) Interactions On Nicotinic Acetylcholine Receptors

      Daniello-Weltzen, Maegan M.; Schulte, Marvin K. (2011)
      Neuronal nicotinic acetylcholine receptors (nAChRs) are members of the Cys-loop super family of ligand gated ion channels. Dysregulation of nAChRs can lead to pathologies such as Alzheimer's disease, Parkinson's disease, Autism and nicotine addiction. Possible new therapeutic avenues are positive allosteric modulators (PAMs). The natural product desformylflustrabromine (dFBr), a tryptophan metabolite of the marine bryozoan Flustra foliacea, was found to be PAM of alpha4beta2 nAChR. Evaluation of our synthetic water soluble dFBr salt by two-electrode voltage clamp of Xenopus laevis oocytes expressing human nAChR confirmed that synthetic dFBr displayed similar properties as the natural product. Low concentrations of the synthetic dFBr enhanced ACh's efficacy on alpha4beta2 receptors. At higher dFBr concentrations, dFBr inhibited ACh potentiated responses. On alpha7 receptors, dFBr inhibited ACh induced currents. Further pharmacological characterization of dFBr revealed that dFBr was able to enhance partial agonist potencies and efficacies. Evaluation of dFBr on antagonists showed no effect on antagonist inhibition. The mechanisms of biphasic modulation (potentiation and inhibition) of dFBr on alpha4beta2 nAChR were also investigated. Enhanced efficacy of ACh induced currents by dFBr appeared to be accomplished by dFBr stabilization of the open receptor conformation by destabilization of the desensitized state. The inhibition of ACh potentiated currents by dFBr appeared to involve open-channel block. To better understand dFBr mechanisms, its putative binding site was examined. Alanine mutations were made in non-orthosteric clefts on the beta2+ and alpha4- faces. Results revealed residues located on these faces are involved in ACh induced conformational change of the receptor. In addition our data supports our hypothesis that allosteric modulation by dFBr interacts with residues located on the beta2+ and alpha4- faces. The new novel actions of (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) (HEPES) as a alpha4beta2 stoichiometric PAM was discovered and characterized. We showed that HEPES, a common buffering agent, potentiated the high ACh sensitivity alpha4beta2 receptor while only inhibiting the low ACh sensitivity alpha4beta2 receptor. Mutagenesis results suggested that residue beta2D217 is a critical residue in the HEPES binding site. Results from these studies will aid in the development of therapeutic ligands that will assist in the treatment of diseases where nAChRs are dysregulated.
    • Investigation of the friction and noise of automotive rubber belt

      Narravula, Vikram R. (2011-05)
      The objective of this research was to study the frictional properties of an automotive v-ribbed belt-pulley system. In order to evaluate the friction and noise, a new test setup was constructed. The assembly was run under various environmental and operational conditions and the results were quantified, studied, and compared among themselves. The environmental conditions included dry interface and wet interface, conducted at both room temperature (23°C) and cold temperature ( -20°C). Operational parameters varied during the experiment were wrap angle, load attached, and acceleration. Frictional forces and associated noises generated were recorded. Some of the results generated were compared with previous research work, and the setup was also used to generate new data for conditions not previously studied. Dry room temperature results show close correlation with previous research. The presence of water in liquid state in the interface induces larger adhesion as water film in the interface changes friction mechanisms in the rubber belt-pulley interface. The high stiction of wet friction can lead to stick-slip vibrations and squeal noise. The theoretical stiction model for wet belt-pulley interface is presented. The stiction-related noise test is conducted, and the result is used to identify the spectrum pattern. The belt friction under cold conditions is found to have a higher value than that in room temperature conditions. The belt noise under cold conditions is found to have much higher squeal frequency than that in room temperature conditions.