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Undergraduate Research Opportunities Program

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Office of Undergraduate Education

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Publication Search Results

Now showing 1 - 10 of 116

Development of an in vitro technique for examining catch bond behavior of integrin receptors

(Georgia Institute of Technology, 2010-12-20) Stanley, Brandon T.

Previous research has shown catch bonds to be critical as bond lifetime regulators between integrin receptors and ligands. These adhesive mechanisms prolong the bond lifetimes of specific molecules with an increasing applied force. Characterizing catch bond behavior may be helpful in explaining how the body regulates the activity of white blood cells. These cells must flow freely, but attach to injury sites within blood vessels. To analyze catch bond behavior in groups of receptors, we plan to develop a technique to examine the catch-bond behavior of groups of α5β1 integrin molecules. A chimeric α5β1 integrin-Fc molecule, which presents the integrin binding domain at one end of the molecule and the human Fc portion of an antibody at the other end, will be used as the bead-bound receptor while fibronectin and various mutations of the molecule will be used as the surface-bound ligand. This experimental platform will allow the analysis of catch-bond behavior in a well-defined cell-free model system.
Amorphous silicon and carbon nanotube-based photovoltaics

(Georgia Institute of Technology, 2010-12-20) Nguyen, Justin J.

In this study, the possibilities of creating an effective amorphous silicon (a-Si) based photovoltaic (PV) cell supported by a 3D carbon nanotube (CNT) structure are investigated. Vertically aligned carbon nanotubes (VACNTs) provide a significant advantage increasing photon dwell time in photovoltaic materials via light trapping at off-normal angles to the sun. By creating a 3D array, CNTs allow for the use of less and therefore cheaper PV material, particularly a-Si. This study examines and presents the creation of such a novel PV cell through thermally-enhanced chemical vapor deposition (TECVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques. The 3D a-Si PV cell that is presented consists of a single junction p-i-n photodiode less than 350 nm in total width that absorbs photons just above the 1.7 eV energy level. A close examination of the growth and morphology of a-Si and nanocrystalline silicon (nc-Si) thin films on CNTs is also presented and studied, with discussion stemming from the results of scanning electron microscopy (SEM), optical microscopy, atomic force microscopy (AFM), Raman spectroscopy, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectrophotometry, and current-voltage measurements.
Native parasite combating an invasive species: an oomycete vs. Echinogammarus ischnus

(Georgia Institute of Technology, 2010-12-20) van Rensburg, Karla

In the context of invasions in ecology, parasites can play an important role in mediating the outcomes of competition between the native and invasive species. For example, a native parasite in the upper St. Lawrence River area has been found infecting both native and non-native gammarid amphipods, Gammarus fasciatus and Echinogammarus ischnus, respectively. Usually when the non-native species invades an area, the native amphipod is rapidly replaced by the non-native species. However, in this specific region the native amphipod was not replaced by the non-native species, and the non-native species was observed to be infected by a parasite. To determine infection rates in the native and non-native hosts, DNA was extracted from both species of amphipods and specific primers for the 18S rRNA gene were created to generate quantitative analysis of the incidence of the parasite in the amphipods. These data indicate that the effect of the parasite on the native and non-native amphipods could be the mechanism preventing the dominance of the non-native species in this specific area for the past ten years, since the parasite was found to infect the non-native amphipod more frequently and at a higher level than the native amphipod.
Designing a character avatar model for the Mermaids MMO

(Georgia Institute of Technology, 2010-12-20) Ead, Samer Omar

This paper describes the technique formed for the creation of an efficient, simply rigged, customizable mermaid avatar model for the Mermaids massively multiplayer online game (MMOG). Our goal was to improve the in game customization of the player s 3D mermaid model, while maintaining rendering efficiency. We devised a procedure that utilizes the iterative nature of design without sacrificing the scientific and technical aspects of the project. Our procedure begins by a method known as Partitioning where we break down the model s body into distinct sub-models. During development, this partitioning allowed us to focus on smaller concise areas of interest, whereas during game-play this change granted the player greater strands of customization freedom. Since the model relied on a skeleton for its animations, it s partitioning required Skeletal Reformations to reassess the control scheme of the rig over the sub-models. In this method, individual sub-skeletons were designed to provide increased local control over their respective sub-models in contrast to the global control that the previous rig allowed. The sub-skeletons were then joined together forming a combined and complete skeletal rig for the mermaid model. We iterated through the previous methods refining their procedures in efforts of Balancing Customizability with Efficiency , which in turn provided us with the results of our novel technique. Our technique utilizes innovative methods that localize skeletal control over respective sub-models in a novel way, which allows increased customizability with limited costs to efficiency.
The effect of a pathogen on the population dynamics and reproductive method of Asplanchna girodi

(Georgia Institute of Technology, 2010-12-20) Reynolds, Abigial Nicole

Studies show that the abundance of Asplanchna girodi can be affected by many factors including food density, temperature and pH. One such aspect not yet explored is the effect that parasitism has on Asplanchna girodi populations. During weekly samplings of a local lake, a parasitic oomycete was discovered to frequently infect the Asplanchna girodi population. Based on multi-year sampling data, this study supports recent work showing that parasitism of a zooplankton has the potential to have reproductive and evolutionary consequences. I show that epidemics of this parasite, Pythium, occur frequently and that an increased number of males in the population can be correlated to the presence of the parasite. Sexual reproduction involving males provides for Asplanchna girodi's only means of genetic recombination and production of diapausing eggs that overwinter. This study shows that there is a correlation between the rate of infection by Pythium and the density of males in the Asplanchna girodi population. By increasing the number of males in a population, the rate of diapause egg production is also increased. Infection by this parasite could therefore be associated with increased sexual reproduction and genetic recombination of A. girodi populations.
Development of a separable 3D cell co-culture system for the study of stem cell microenvironments

(Georgia Institute of Technology, 2010-12-20) Bloodworth, Nathaniel Craig

Stem cells represent an attractive cell choice for regenerative medicine applications due to their inherent ability to differentiate down multiple cell lineages given the correct cues. However, little is known concerning how the interactions, specifically the paracrine signaling effects, of native cells will influence the growth, proliferation, and differentiation of stem cells after implantation in vivo. This lack of fundamental knowledge necessitates the development of an in vitro model. Hydrogels are a biomaterial uniquely suited to the task of providing a tunable, cytocompatible environment in which to study these interactions between cell populations. By utilizing the technique of photolithography in conjunction with microfluidics, we developed and optimized a system to sequentially construct spatially segregated 3D co-culture constructs that will provide a basis for better understanding paracrine signaling between stem cells and other cell types native to orthopedic tissues. Additionally, by incorporating a degradable hydrogel interface between components, we demonstrated the separability of this system and the potential to isolate and recover individual populations after culture.
Aerobic biodegradation of diphenylamine

(Georgia Institute of Technology, 2010-12-20) Kim, Jenny Gi Yae

Diphenylamine (DPA) is a primary pollutant used as a stabilizer and as precursor for pesticides, pharmaceutical products and dyes. It has recently been found that a dioxygenase enzyme is responsible for the ability of bacteria to biodegrade diphenylamine (8). Despite our understanding of the degradation pathway of DPA, important questions remain regarding the evolutionary origin of the gene that encodes the dioxygenase. The answers to these questions will help future efforts to biodegrade this hazardous pollutant. Through selective enrichment, isolation and genetic screening, aniline degrading bacteria have been discovered to be responsible for the genes that encode the lower part of the DPA degradation pathway. Using the same technique of enrichment, isolation and genetic sequencing, we screened for candidates for the origin of the genes that encode DPA dioxygenase. Our hypothesis is that carbazole dioxygenase is the progenitor of DPA dioxygenase at the Repauno site. Comparison of the dioxygenase genes will allow us to test the hypothesis that horizontal gene transfer facilitated assembly of the pathway. We have also hypothesized that DPA degrading bacteria will not be able to degrade carbazole as a sole carbon, nitrogen and energy source to determine whether or not degrading bacteria are capable of having two pathways of degradation. We will test DPA degraders to determine whether or not they are able to degrade carbazole. Analyzing carbazole degradation will allow us to test the hypothesis that DPA degrading bacteria will not have retained the ability to degrade carbazole during the evolution of DPA dioxygenase due to our hypothesis that DPA dioxygenase originated from carbazole dioxygenase. In our future studies we are hoping that a carbazole degrader will encode a carbazole dioxygenase that will show significant similarities to DPA dioxygenase. We hope to develop results what will suggest that the dioxygenase gene originated from carbazole degraders through horizontal gene transfer. Experiments revealed that carbazole was not degraded by DPA degraders. The data support our hypothesis that DPA degrading bacteria did not retain the carbazole degradation pathway from carbazole degrading bacteria during the evolution of DPA dioxygenase.
Zooplankton population dynamics in Clayton County Water Authority reservoirs

(Georgia Institute of Technology, 2010-12-20) Ahmed, Tamanna

Reservoirs supply most of Georgia s drinking water, and plankton dynamics can greatly influence the water quality of these reservoirs. Therefore, understanding the dynamics of zooplankton as well as phytoplankton is necessary. Unlike reservoirs in the northern United States, zooplankton dynamics in reservoirs in the South remain largely uncharacterized. Samples were collected from the Clayton County Water Authority reservoirs to study correlations between zooplankton taxa distribution and environmental variables. Population count data has demonstrated that the zooplankton dynamics in southern lakes vary from the dynamics typically seen in northern lakes. While temperature noticeably shaped seasonal densities in some species, other species had variable dynamics and seemed to not be affected by this environmental factor or other taxa of zooplankton, suggesting additional factors may regulate population composition and abundance.
Development and application of a rapid military model development framework

(Georgia Institute of Technology, 2010-12-20) Andriano, Nelson Gregory

Military operations are complex systems composed of the interactions of many smaller discrete systems, or assets: aircraft, watercraft, troops, etc. Historically, the requirements for new assets have been created based on standalone optimization. It is not just necessary to optimize requirements for a single scenario, such as a wartime operation, but instead to optimize the requirements that will benefit the entire military operation as a whole in a number of different scenarios, such as wartime and peace time. To better define future military assets it is necessary sample a large number of scenarios. To capture all of the interactions and develop a complete understanding of the overall system, it is necessary to model both combat and logistics, which have traditionally been modeled and analyzed separately. To characterize military operations and the assets that contribute to them, it is necessary to move beyond the traditional models that use aggregated approximations for combat and stand alone nodal analysis for logistics. A unique need for a framework which captures the complex interaction between combat and logistics while allowing a large number of automated cases and scenarios to run with no human in the loop. The framework this paper discusses was created to facilitate the making of models to analyze and characterize military operations and the effects that future assets will have on entire operations. The framework is agent-based, allowing bottom up definition and the gathering of emergent behavior, and uses a modified Hughes salvo method for combat, the Foundation for Intelligent Physical Agents messaging structure, and the beliefs, desires, and intentions (BDI) agent model. The modeling of communication and BDI creates myopic agents that are constrained by the information they can obtain, process, and react to. In this paper, the framework is first depicted and then validated by the creation of a model with the purposes of defining the requirements for a future asset, the Transformable Craft. The creation and testing of the model prove that the requirements for the framework have been met with success. The potential applications of the framework ranges from data-farming military operations models for future asset requirement, characterizing military operations systems, and providing a stepping stone for future agent-based military operations modeling and simulation work.
Uranyl phosphate minerals as long term sink in uranium bioremediation

(Georgia Institute of Technology, 2010-12-20) Saad, Emily Marie

US Department of Energy nuclear fuel and weapon production has resulted in uranium contaminated soils and groundwater. As the magnitude of this environmental issue requires an in situ remediation strategy, bioreduction of soluble U(VI) to insoluble U(IV) has been investigated. However, site specific conditions prevent the effectiveness of this remediation technique requiring instead a redox independent method. The biomineralization of the water soluble U(VI) species is presented as a remediation alternative, and the role of different organophosphate species and bacterial strains in this process continues to be studied. However, the stability of these uranyl phosphate minerals must also be examined to evaluate their role as long term sinks for uranium. This study seeks to quantify uranyl phosphate stability in environmentally relevant conditions by examining the effect of Na+, Ca2+, SO42-, and HCO3- present in typical subsurface environments, and uranium phosphate biomineralization in the presence of carbonates. The results of the study suggest that the uranyl phosphate species biomineralized by the facultative anaerobe, Rahnella sp.Y9602, isolated from soils at the DOE Oak Ridge Field Research Center (ORFRC) as a model organism, is preferred even in the presence of the competing carbonate species. Furthermore, even in the presence of cations and anions, uranyl phosphate minerals may be exploited as an alternative remediation reservoir.