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NSF-EPSCoR Undergraduate Research Awards |
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Abstracts |
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2006 Summer Award Recipients (UNLV) |
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Determinacy of Three-Player games
Determinacy of two-player infinite games of perfect information with definable payoff sets is well-known. Determinacy fails for such three-player games, but holds for such games having two open payoff sets and satisfying certain conditions. We investigate three-player games, having a payoff set which is a countable intersection of open sets. |
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Cristine Alvarez Working with: Dr. Derrick DuBose Mathematics |
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Thermal Structure Studies of ZnO in the Temperature Range 0 - 120 C ZnO is an important material widely used in various applications ranging from electronic to medical. For example, nanocrystals of ZnO offer superior optical properties over the bulk material due to quantum confinement effects. In addition, ZnO nanocrystals or quantum dots (QD) have potential applications in UV lasers, solid state spinel batteries, and fabricating nanolasers. From previous studies, it has been found that grain size significantly influences the physical and chemical properties of structures, such as ZnO nanowires, needles, and rods. For this reason, the structure of nanocrystalline and bulk polycrystalline ZnO was examined in the temperature range of 0 – 120 C (273 – 393 K) using X-ray diffraction. However, over this temperature range, no phase transition was observed. |
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Jason Baker Working with: Dr. Andrew Cornelius Physics |
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The Role of PFOS on Immunological Cell Types and Mechanisms of Immunosuppression
Perfluorinated hydrocarbons are synthetic compounds that have been manufactured over 50 years and are currently used throughout industry in semiconductors for computers and other electrical equipment, stain and water repellents, paper food wrappings, firefighting foams, shampoos, carpet spot cleaners, pharmaceuticals, and pesticides. Some of perfluorinated compounds are extremely resistant to environmental degradation processes and metabolism. These compounds are bioaccumulative and persistent in both the environment and in the body. The primary perfluorinated hydrocarbons detected in serum samples is perfluorooctane sulfonate (PFOS), which has a half-life of about 8.7 years. Studies have shown that this group of compounds exhibits a unique toxicokinetic profile as they are not sequestered in adipose tissue, but rather circulate in the enterohepatic system. In adult animal models they cause a variety of effects including peroxisomal proliferation, hepatomegaly, altered steroidogenesis, thyroid hormone modulation, and immunotoxicity. Recent studies have identified that low-level, gestational exposure to PFOS manifests as suppression of humoral antibody responses apparent in adult male mice. Considering the toxicological effects of perfluorinated hydrocarbons (i.e., PFOS), this study examined the effects of PFOS in white leghorn hatchlings on various developmental parameters and aspects of the immune system, including antibody responses, lymphocyte proliferation, PHA-skin test responses, and plasma lysozyme activity following in ovo exposure. Gestation day (GD) 0 eggs were injected with either safflower oil or PFOS in safflower oil at 1, 2.5 or 5 mg/kg egg weight, and the chicks were grown to past hatch day (PHD) 14. Following in ovo exposure chicks exhibited increased liver and spleen weights at all treatment levels and at the 5 mg/kg treatment, body length (crown-rump length) was increased compared to control. For all three treatment groups, plasma IgG titers were increased as was lysozyme activity while no effect was seen in the cell mediated response in the PHA skin test. This is the first study to assess developmental and immune modulation following PFOS exposure in an avian species. This data indicates that immune alterations can occur in birds following in ovo exposure to environmentally relevant concentrations of PFOS and demonstrates the need for further research on the effects of perfluorinated compounds on immune function. |
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Jennifer Berger Working with: Dr. Deborah Keil Clinical Lab Science |
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The Effects of Varying CO2 Levels on Syntrichia caninervis Syntrichia caninervis is a bryophyte that is native to certain desert landscapes especially to southern Nevada. This specie of moss reacts differently after prolonged exposure to varying CO2 levels in the form of either decreased or increased biochemical activity. These biochemical activities are presented through protonemal and apical growth as well as regenerant shoot emergence. To determine the extent to which various CO2 levels affect Syntrichia caninervis, shoots collected from regions of likewise varying CO2 levels [ambient at 380 ppm and elevated at 550 ppm], at the Nevada Test Site Desert FACE Facility, were grown in growth chambers with two different CO2 concentrations. The first growth chamber held ambient CO2 at 380 ppm while the second chamber held an elevated CO2 level at 550 ppm. The shoots were grown for twenty-five days and regularly examined for signs of growth and development. Half of the shoots collected at ambient CO2 and grown at elevated CO2 chambers started showing visual signs of growth on day 17, while the other half grown in ambient CO2 showed signs of growth until day 14. Half of the shoots collected at a site with an elevated CO2 levels and then grown in ambient CO2 level conditions began showing signs of growth on day 17. The other half grown in elevated CO2 level began showing signs of growth on day 10. |
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Catherine Fernando Working with: Dr. Lloyd Stark Life Sciences |
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Characterization of minerals associated with gold deposition in Carlin deposits, Northern Nevada
Northern Nevada contains the second most productive gold district in the world, yet details of the origins of this district and the geochemical processes involved in its formation are not well understood. Existing sample suites were examined to identify ore zone sample transects that exhibited a wide range of gold concentrations. Transects were selected from three ore zones including the Screamer and North Betze ore zones in the Betze-Post deposit in the northern Carlin trend, and from N Zone in the Getchell deposit on the Getchell trend. Samples with gold assays ranging from very low (0.005 oz/ton) to very high (8.131 oz/ton) were evaluated using x-ray diffraction (XRD) analyses, exposure to 10% solution hydrochloric acid (HCl Fizz Test), geochemical analyses for both major elements and trace elements, and petrographic observations. The results of these analyses were used to 1) identify minerals, 2) quantify mineral composition, 3) determine the variation of mineralogy as a function of gold grade, 4) correlate elemental concentrations with mineralogy, and 5) use these data to contribute to an understanding of the impact of the ore-bearing fluids during the development of these prolific and economically significant ore systems. |
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Lora Griffin Working with: Dr. Jean Cline Geology |
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Does Loss of Transcription Factor NusA Affect Stationary Phase Mutagenesis in Bacillus subtilis?
Bacillus subtilis is a model of development and differentiation, undergoing such processes as sporulation, biofilm formation, and competence. Our laboratory previously demonstrated that non-growing B. subtilis cells undergo stationary phase mutagenesis when subjected to a non-lethal selective pressure, starvation for an amino acid. Stationary phase mutagenesis is an adaptive and genetically programmed response to stress, and may play a role in the development of pathogenicity and the formation of cancer. Our goal is to elucidate the genetic pathway(s) responsible for regulating this important process. Several gene products play a role in stationary phase mutagenesis in B. subtilis, including developmental regulators ComA and ComK, mismatch repair protein MutS, and error-prone DNA polymerase YqjH. Our laboratory has recently discovered that transcription repair coupled factor Mfd and elongation factor GreA, which directly modulate the activity of RNA Polymerase, are involved in stationary phase mutagenesis. In the absence of these proteins, the accumulation of revertants measured in our assay decreases dramatically. We hypothesize that the rate of transcription, which is altered in the absence of these factors, is correlated to the accumulation of mutations at transcribed alleles. The NusA elongation factor also modulates RNAP activity and stimulates pausing at hairpins as well as antitermination. Since Mfd, GreA and NusA modulate RNAP activity and affect transcription levels, elucidating the effects of a nusA genetic disruption on stationary phase mutagenesis would broaden our understanding of the role of transcription in this process. To this end, we are constructing a plasmid vector containing a non-polar nusA disruption, as well as an expression vector containing a complete copy of the nusA gene. These tools will allow us to create the nusA disruption in B. subtilis strain YB955 and to complement in trans.
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Dalia Hawwass Working with: Dr. Ronald Yasbin, Dr. Eduardo Robleto Life Sciences |
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Juan Plata Working with: Dr. Shizhi Qian Mechanical Engineering |
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Designing a Magnetically Actuated Micro-Pump for On-Chip Polymerase Chain Reaction Reactors
The Polymerase Chain Reaction (PCR) provides an extremely sensitive mean of amplifying small quantities of DNA; it has numerous uses in multiple fields. Most benchtop PCR reactors, maintain the sample stationary while the temperature is repetitively alternated from about 94oC, to approximately 55oC, and finally to 72oC. This process results in considerable thermal inertia, thus making it slow and energy-intensive. To overcome the problems associated with the stationary PCR, we aim to develop a continuous-flow on-chip PCR reactor in which the temperature of the three thermal zones is maintained fixed while the reagents are cycled continuously through these zones. A magnetically actuated micro-pump to continuously circulate the sample through the three thermal zones of the on-chip PCR is designed, constructed and tested. The on-chip PCR device consists of a toroidal microconduit connecting sample inlet and outlet microchannels. The closed-loop toroidal conduit must be filled with a mixture of reagents and biocompatible magnetic fluid without creating air bubbles with the aid of phase-change valves. Three heaters maintained respectively, at about 94oC, 55oC and 72oC are embedded beneath the microconduit. The continuous fluid motion is induced by rotating a magnet affixed to a micro rotor that is attached to a micromotor. The experimental results demonstrate that the pump successfully continuously circulate the sample in a closed loop which can be used for on-chip PCR reactors.
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Sarah Skaggs Working with: Dr. William Zamboni Nursing |
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The Effect of Oxygen on PMN Polarization and Adhesion of CD11b in Ischemia Reperfusion Injury Ischemia/reperfusion (IR) injury has been shown to cause the quantitative increase and polarization of the CD18/11b proteins on the surface of neutrophils (PMNs) and the consequential adhesion of the neutrophils to the endothelial lining of blood vessels. Hyperbaric oxygen therapy (HBO=100% O2 at 2.5 ATA) has proven effective in qualitatively decreasing the polarization and reducing the percent of adherent PMNs. The purpose of this study was to determine if the depolarization and decreased neutrophil adhesion is due to the 100% oxygen or the 2.5 ATA pressure during HBO. The gracilis muscle flap of male Wistar rats was isolated. The femoral artery and vein were clamped, initiating four hours of ischemia followed by fifteen minutes of reperfusion. The animals were divided into five groups: 1) Non-Ischemic control, 2) IR, 3) IR with HBO therapy, 4) IR with hyperoxia/normobaric therapy (100% O2 at RTP), and 5) IR with Normoxia/Hyperbaric therapy (8% O2 at 2.5 ATA). Plasma was obtained from whole blood drawn from the gracilis muscle directly. Normal PMNs were obtained from a separate donor animal with no intervention. In the adhesion assay, the PMNs reacted with activated plasma in the presence of an ICAM coated coverslip and the number of adherent neutrophils counted via light microscopy and expressed as percent adherent neutrophils (mean+SEM). For the polarization assay, normal neutrophils were exposed to activated plasma in the presence of ICAM, labeled with FITC-Anti-CD11b, and viewed via confocal microscopy. The first 20 single cells from each reaction were photographed, and the cell surface was analyzed as three equal areas. Mean fluorescent intensity (I) was used to determine polarization (I Area 1/(I Area 2 + I Area 3) > 1 è polarized PMN). Statistical analysis was by ANOVA and appropriate post hoc comparisons. A p<0.05 was considered significant. The control group demonstrated a normal neutrophil response of 0.8+0.1% neutrophil adhesion and 6.2+1.7% PMN polarization. The IR injuries with no HBO treatment showed a significant increase (p<0.01) to 16.7+2.2% adhesion and 43.9+12.1% polarization. When the IR injury was treated with HBO, a significant improvement (p<0.01) was seen in both the adhesion and polarization (1.6+0.4% and 4.1+2.5% respectively). When 100% O2 was administered at RTP, 15.0+2.0% of the PMNs adhered to the coverslip, and 35.0+4.2% of neutrophils were polarized (p<0.05 vs control and IR+HBO groups). Rats that were treated with 8% O2 at 2.5 ATA showed 19.5+3.9% PMN adhesion and 42.0 + 8.9% PMN polarization (p<0.01 vs control and IR+HBO groups). Based on the results of this study, it appears that HBO therapy is only effective in reducing CD18/11b protein polarization and neutrophil adhesion when 100% oxygen is administered at increased pressure. Neither the oxygen nor the pressure alone significantly decreases adhesion or polarization of CD18/11b.
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Amanda Souza Working with: Dr. Eduardo Robleto Dr. Brian Hedlund Dr. Helen Wing Life Sciences |
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Dissecting adaptation of Pseudomonas fluorescens to arid soils Pseudomonas fluorescens is a soil denizen and is used as a prokaryotic model to study adaptation to fluctuating environments. Overall goal of this experiment is to genetically dissect cellular processes that are important for Pseudomonas fluorescens to adapt to arid soils. I hypothesize that AdnA is important for growth in arid soil, however its effects are not due to the activation of genes affecting chemotaxis (movement toward or away from a chemical) or motility.
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Matthew Touton Working with: Dr. Rogger Rennels Chemistry |
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Thermochemical Hydrogen Production from Metal Oxides Since the 1950’s the scientific community has been trying to develop some method of capturing solar energy and utilizing it as a chemical fuel. With advances in technology and much trial and error, we are closer to realizing that goal. Coupling modern solar collecting technologies with REDOX chemistry can generate hydrogen, which can be used as a clean source of renewable energy. An interactive online database has been created to list and evaluate the known water splitting cycles. The evaluation process allows for the screening of cycles to select only the most viable cycles for further investigation. These top thermochemical cycles can be placed into five categories: Metal Oxide, Sulfuric Acid, Volatile Metal Oxides, Metal Sulfates, and one other “interesting” cycle. The scope of this presentation is to examine the high temperature step of the Cadmium Carbonate thermochemical cycle.
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Rycel Uy Working with: Dr. Dong-Chan Lee Biochemistry |
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Asymmetric Bisphenazine Monomers for New Electron-deficient Conjugated Polymers In response to a growing scientific and economic interest in novel electron-deficient organic semiconductor materials for optoelectronic applications (such as solar cells, field-effect transistors, and light-emitting diodes), a synthetic route to asymmetric bisphenazine monomers for new electron-deficient conjugated polymers has been developed. The route involves eleven steps, all with good yields. Of particular interest is the synthesis of unprecedented asymmetric bisphenazine by simple sequential addition of two different diamines to a tetraketone without isolating the intermediate. The structures of these new compounds were characterized by nuclear magnetic resonance (NMR) spectroscopy and gas chromatography mass spectrometry (GC-MS). Continuing research will polymerize the asymmetric bisphenazine monomers for new electron-deficient conjugated polymers.
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Effects of global change on diversity of prokaryotic phosphate solubilizers in the Mojave Desert It is apparent that global change has affected every aspect of all ecosystems in the world. Arid and semi-arid ecosystems, such as the Mojave Desert, cover about 30% of the terrestrial earth and are therefore considerably important. These ecosystems are characterized by being very nutrient limited and extremely sensitive to environmental fluctuations. Here we examine how different global change scenarios affect prokaryotic phosphate solubilizers. We sampled plots under treatments of irrigation, added nitrogen and surface disturbance for their populations of prokaryotes as detected by dilution plating on media containing a source of insoluble phosphate for a calendar year. Thirteen isolates belonging to the Actinobacteria Streptomyces, Arthobacter, and Clavibacter numerically dominated in our plate assay. Treatments and time of sampling influenced abundance of bacterial species. Our results suggest that climate change affects levels of phosphate solubilizers and alters phosphorus balance in arid ecosystems.
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Adelbert Villoso Working with: Dr. Eduardo Robleto Dr. Brian Hedlund Dr. Helen Wing Life Sciences |
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Carrie Wong Working with: Dr. Allen Gibbs Dr. Deborah Hoshizaki Life Sciences |
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The Effects of Temperature on the Energetics of Metamorphosis in Drosophila Melanogaster In preparation for metamorphosis, the fruit fly Drosophila melanogaster undergoes numerous physical reconstructions within the pupal case, suggesting an increase in energy consumption in order to sustain these changes. However, metabolic rates during pupation actually decline approximately eighty percent during the first twenty-four hours after pupariation, then rise steadily shortly before eclosion at ninety-six hours. Thus, during a period of substantial physical transformation prior to metamorphosis, metabolic rates are remarkably low. Environmental factors, particularly temperature levels, impact developmental rate and final adult size of insects. Although the affects of temperature on the adult metabolic rates are known, the impact of temperature on developing pupae has not previously been studied. Therefore, we determined the metabolic rates of the pupae at selected time points throughout pupation using pupae reared at different incubation temperatures (18 ºC, 25 ºC, 29 ºC). We also investigated the possible energy substrates expended during pupation—primarily protein, carbohydrate, and triglyceride stores. A series of enzymatic digestion (for carbohydrate and triglyceride measurements) and dye attachment (for protein measurement) assays were utilized to measure the amount of substrate exhausted by the organism. The assays indicated that the pupae metabolized a combination of carbohydrates and triglycerides; however, proteins were not metabolized. Supported by NSF Grant EPS-0447416
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Paul Lawson Working with: Dr. Deborah Hoshizaki Life Sciences |
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Further investigation of whale and thorax missing genes in Drosophila melanogaster
This research will focus on two mutations that affect Drosophila melanogaster larvae to adult fly metamorphosis. The whale gene results in larvae that are significantly larger in size than wildtype larvae and die as aged larvae while the thorax missing gene results in pupae which appear to have the thorax missing. Flies that are heterozygote for the whale mutation are larger in size which is correlated with an increase in reproduction and higher survival in adverse conditions. This raises the question whether the whale mutation results in a heterozygote advantage for flies that carry one mutant whale allele. In addition, anecdotal evidence suggest that the lethality associated with the homozygous whale larvae is temperature sensitive, and animals raised at lower temperature survival to adulthood. We have further localized the whale gene to a small cytological region from 25C8 to 25D2 and the thorax missing gene lies in cytological region spanning 34D1-2 to 34E5. We have established a baseline growth pattern for the whale stock at 25°C. Further research will test the idea that whale mutation is temperature sensitive by comparing growth pattern at different temperatures and further define how whale and thorax missing function. Do they code for transcription factors, signaling molecules, etc. We are focusing on both of these genes because the both mutant alleles reside in cis on the second chromosome.
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