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- Title
- RECOVERY OF HYDROGEN AND HELIUM FROM THEIR MIXTURES USING METAL HYDRIDES.
- Creator
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Oztek, Muzaffer, Hampton, Michael, University of Central Florida
- Abstract / Description
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Waste streams of hydrogen and helium mixtures are produced at the Kennedy Space Center during purging of the hydrogen systems and supply lines. This process is done prior to and after hydrogen servicing. The purged waste gases are lost to the atmosphere, resulting in an annual loss of 2 million and 0.1 million standard cubic meters of helium and hydrogen, respectively. Recovery of these gases will have an economic benefit. Metals, alloys, and intermetallics are known to react with hydrogen in...
Show moreWaste streams of hydrogen and helium mixtures are produced at the Kennedy Space Center during purging of the hydrogen systems and supply lines. This process is done prior to and after hydrogen servicing. The purged waste gases are lost to the atmosphere, resulting in an annual loss of 2 million and 0.1 million standard cubic meters of helium and hydrogen, respectively. Recovery of these gases will have an economic benefit. Metals, alloys, and intermetallics are known to react with hydrogen in favorable conditions; therefore, they have the possibility of serving as separating and recovery agents. In this study, Mg2Ni, VTiNi and LaNi5 were studied for the separation of H2 from He, using differential scanning calorimetry and thermal volumetric analysis. The ability of LaNi5 to react with hydrogen reversibly at room temperature was verified, and further analysis focused on this compound. Size reduction and activation of LaNi5 by mechanical milling was investigated using different milling parameters for the purpose of activating the material for hydrogen absorption. Because it has been shown that addition of aluminum to LaNi5 resulted in improved hydriding and dehydriding properties, that system was studied further here. In this study, aluminum was added to LaNi5 by mechanical milling. Hydriding properties and elemental compositions of the samples were determined afterwards. The hydrogen absorption rate and capacity were compared to that of LaNi5. Both LaNi5 and its Al doped derivatives exhibited a reduced rate of hydrogen uptake and a reduced hydrogen capacity in the presence of helium. The effects of coating the samples with either gold-palladium or platinum were investigated. It was observed that coating the samples with Pt reduced the negative effect of He, whereas AuPd coating did not have any effect. Larger scale studies were done using a continuous U-tube hydride reactor, built and tested for separation of H2¬ from a 20:80 H2:He mixture. The amount of hydrogen retained in the bed was determined and found to be less than that for the batch systems.
Show less - Date Issued
- 2005
- Identifier
- CFE0000660, ucf:46507
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000660
- Title
- THE STUDY OF THREE DIFFERENT LAYERED STRUCTURES AS MODEL SYSTEMS FOR HYDROGEN STORAGE MATERIALS.
- Creator
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Oztek, Muzaffer, Hampton, Michael, University of Central Florida
- Abstract / Description
-
The strength and success of the hydrogen economy relies heavily on the storage of hydrogen. Storage systems in which hydrogen is sequestered in a solid material have been shown to be advantageous over storage of hydrogen as a liquid or compressed gas. Many different types of materials have been investigated, yet the desired capacity and uptake/release characteristics required for implementation have not been reached. In this work, porphyrin aggregates were investigated as a new type of...
Show moreThe strength and success of the hydrogen economy relies heavily on the storage of hydrogen. Storage systems in which hydrogen is sequestered in a solid material have been shown to be advantageous over storage of hydrogen as a liquid or compressed gas. Many different types of materials have been investigated, yet the desired capacity and uptake/release characteristics required for implementation have not been reached. In this work, porphyrin aggregates were investigated as a new type of material for hydrogen storage. The building blocks of the aggregates are porphyrin molecules that are planar and can assume a face to face arrangement that is also known as H-aggregation. The H-aggregates were formed in solution, upon mixing of aqueous solutions of two different porphyrins, one carrying positively charged and the other one carrying negatively charged functional groups. The cationic porphyrin used was meso-tetra(4-N,N,N-trimethylanilinium) porphine (TAP) and it was combined with four different anionic porphyrins, meso-tetra(4-sulfonatophenyl)porphine (TPPS), meso-tetra(4-carboxyphenyl) porphine (TCPP), Cu(II) meso-tetra(4-carboxyphenyl) porphine, and Fe(III) meso-tetra(4-carboxyphenyl) porphine. The force of attraction that held two oppositely charged porphyrin molecules together was electrostatic attraction between the peripheral groups. Solid state aggregates were successfully isolated either by solvent evaporation or by centrifuging and freeze drying. TCPP-TAP and Cu(II)TCPP-TAP aggregates were shown to interact with hydrogen starting from 150 °C up to 250 °C. The uptake capacity was about 1 weight %. Although this value is very low, this is the first observation of porphyrin aggregates absorbing hydrogen. This opened the way for further research to improve hydrogen absorption properties of these materials, as well as other materials based on this model. Two other materials that are also based on planar building blocks were selected to serve as a comparison to the porphyrin aggregates. The first of those materials was metal intercalated graphite compounds. In such compounds, a metal atom is placed between the layers of graphene that make up the graphite. Lithium, calcium and lanthanum were selected in this study. Theoretical hydrogen capacity was calculated for each material based on the hydriding of the metal atoms only. The fraction of that theoretical hydrogen capacity actually displayed by each material increased from La to Ca to Li containing graphite. The weight % hydrogen observed for these materials varied between 0.60 and 2.0 %. The other material tested for comparison was KxMnO2, a layered structure of MnO2 that contained the K atoms in between oxygen layers. The hydrogen capacity of the KxMnO2 samples was similar to the other materials tested in the study, slightly above 1 weight %. This work has shown that porphyrin aggregates, carbon based and manganese dioxide based materials are excellent model materials for hydrogen storage. All three materials absorb hydrogen. Porphyrin aggregates have the potential to exhibit adjustable hydrogen uptake and release temperatures owing to their structure that could interact with an external electric or magnetic field. In the layered materials, it is possible to alter interlayer spacing and the particular intercalates to potentially produce a material with an exceptionally large hydrogen capacity. As a result, these materials can have significant impact on the use of hydrogen as an energy carrier.
Show less - Date Issued
- 2011
- Identifier
- CFE0003752, ucf:48769
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003752
- Title
- Tandem Mass Spectrometric Analysis of Ammonium and Sodium Oligoperoxide Adducts with the Application of Two-Dimensional Correlation Spectroscopy and Computational Chemistry.
- Creator
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Frisch, Jessica, Sigman, Michael, Fookes, Barry, Hampton, Michael, University of Central Florida
- Abstract / Description
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Oligoperoxides, H[OO(CH3)2C]nOOH, are formed as side products in the synthesis of the primary high explosive triacetone triperoxide (TATP). Previous tandem mass spectrometry (MSn) experiments using a quadrupole ion trap reported that the open-chained oligoperoxide adducts of ammonium or sodium resulted in different product ions in the mass spectra. Dissociation mechanisms were previously proposed based on MSn experiments, where n(>)2; however, a dissociation pathway achieved by an MSn...
Show moreOligoperoxides, H[OO(CH3)2C]nOOH, are formed as side products in the synthesis of the primary high explosive triacetone triperoxide (TATP). Previous tandem mass spectrometry (MSn) experiments using a quadrupole ion trap reported that the open-chained oligoperoxide adducts of ammonium or sodium resulted in different product ions in the mass spectra. Dissociation mechanisms were previously proposed based on MSn experiments, where n(>)2; however, a dissociation pathway achieved by an MSn experiment, where n(>)2, may not necessarily be the same pathway achieved in an MS2 experiment. For this dissertation research, the collision induced dissociation pathways were investigated for the open-chained oligoperoxides in MS2 experiments utilizing a quadrupole ion trap. Tandem mass spectral experiments were performed for the open-chained oligoperoxides ranging from the trimer to the octamer (n=3-8), including both ammonium and sodium adducts. The dissociation pathways were proposed as a result of two-dimensional correlation spectroscopy applied to the mass spectral data, which was referred to as two-dimensional correlation mass spectrometry (2D-CMS). The 2D-CMS method was first validated by analysis of simple and more complex kinetic models followed by simple and more complex molecules. To further aid in the elucidation of the dissociation mechanisms, computational chemistry was performed for the optimization of stable precursor and product ion structures and calculations of their relative energies and adduct dissociation energies.
Show less - Date Issued
- 2012
- Identifier
- CFE0004377, ucf:49371
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004377
- Title
- Iron Molybdenum Cofactor: Catalyst in Dihydrogen Production and NifEN's Role in the FeMo-co Biosynthetic Pathway.
- Creator
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Maxwell, Deborah, Clausen, Christian, Yestrebsky, Cherie, Hampton, Michael, Sigman, Michael, University of Central Florida
- Abstract / Description
-
Humankind's tremendous industrial and technological progress over the last two centuries has been driven by the natural abundance and availability of fossil fuels. As those reserves deplete, the prudent course of action would be to develop other readily available fuel sources. Some research efforts using biomolecules involve the hydrogenases and nitrogenases with the goal of evolving dihydrogen. At the nitrogenase active site, the iron-molybdenum cofactor (FeMo-co) catalyzes the reduction of...
Show moreHumankind's tremendous industrial and technological progress over the last two centuries has been driven by the natural abundance and availability of fossil fuels. As those reserves deplete, the prudent course of action would be to develop other readily available fuel sources. Some research efforts using biomolecules involve the hydrogenases and nitrogenases with the goal of evolving dihydrogen. At the nitrogenase active site, the iron-molybdenum cofactor (FeMo-co) catalyzes the reduction of dinitrogen and protons to form ammonia and dihydrogen.Toward the goal of producing dihydrogen passively as an alternative fuel, a novel advanced material has been developed. CdSe nanoparticles complexed with FeMo-co, in both aqueous and organic solvent systems showed complex formation. When the system was interrogated by EPR spectroscopy, evidence of electron transfer was observed. The CdSe-MSA?NafY?FeMo-co system when illuminated with visible light evolved dihydrogen consistently in four different experimental sets under the same reaction conditions. NifEN protein plays an important role in the biosynthesis of FeMo-co in addition to the involvement of NifU, NifS, NifB, NifX, NifH and NafY. After NifB synthesizes a FeMo-co precursor, 6-Fe NifB-co, NifEN further incorporates additional Fe, S, Mo, and (R)-homocitrate to complete the synthesis of FeMo-co. Molybdenum is provided to NifEN as its oxoanion, Mo(VI)O42-; however, in FeMo-co molybdenum is in the oxidation state of Mo(IV). EPR spectroscopic investigation of NifEN turnover samples showed a signal at g = 2.00 that was dependent on molybdate concentration. Power and temperature profiles gave evidence that the g = 2.00 EPR signal was distinct from the Fe-S clusters in NifEN. The species observed at g = 2.00 was assigned to the reduction of Mo(VI) to Mo(V). How to utilize the effectiveness of FeMo-co and complex it to photoactive materials for the purpose of evolving dihyrogen upon illumination, thus providing a sustainable alternative energy source is one subject of this dissertation. A related subject is to gain an understanding of the biosynthetic pathway of FeMo-co by investigation of NifEN turnover experiments. This understanding should contribute towards the development of improved catalysts for meeting future energy demands.
Show less - Date Issued
- 2012
- Identifier
- CFE0004623, ucf:49917
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004623
- Title
- Nitrogen-Containing Materials for Mechanochemical Synthesis, Luminescence Analysis, and Heterogeneous Catalysis.
- Creator
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Nash, David, Zhai, Lei, Hampton, Michael, Harper, James, Rex, Matthew, Blair, Richard, University of Central Florida
- Abstract / Description
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Various inorganic nitrogen-containing materials have been exploited for their different properties. Several nitride materials are commercially attractive due to their mechanical properties making them suitable for ceramic industries and wide bandgaps fitting for use as semiconductor and insulator materials, as well as optoelectronics. Nitride materials can exhibit versatility in applications such as the use of gallium nitride to make blue LEDs, nitrides of titanium and silicon being utilized...
Show moreVarious inorganic nitrogen-containing materials have been exploited for their different properties. Several nitride materials are commercially attractive due to their mechanical properties making them suitable for ceramic industries and wide bandgaps fitting for use as semiconductor and insulator materials, as well as optoelectronics. Nitride materials can exhibit versatility in applications such as the use of gallium nitride to make blue LEDs, nitrides of titanium and silicon being utilized as medical implants for their chemical inertness and hardness, and the heavy use of boron nitride as a solid lubricant in the cosmetic industry. Amines have been used as nitrogen-containing organic ligands in organometallic complexes that exhibit phenomenal photophysical properties. These complexes have been heavily studied for potential applications in optoelectronics and chemical sensing. This dissertation will focus on two nitrogen-containing materials that have yet to be explored for the potential applications to be discussed. The first is hexagonal-boron nitride (h-BN), which was previously mentioned to have a substantial use in the cosmetic industry, giving products such as lipstick, foundation, and blush their slick feeling. Computational models have shown the possibility of altered electronic properties of defect sites in the h-BN sheets. These defect sites will be explored experimentally to determine any catalytic activity. Specifically, the hydrogenation reaction using defect-laden hexagonal-boron nitride will be investigated. Successful catalysis would add to the short list of non-metal catalyst, and provide an alternative catalyst that costs significantly less than the traditional metal catalysts commonly used in commercial industries. The second of the two nitrogen-containing materials is a class of metal complexes based on organometallic clusters of copper(I) iodide. Copper(I) iodide clusters formed with amine ligands have been studied for around four decades and the photophysics behind their photoluminescent properties are well understood. Much of the work has been done for use as a potential emissive material in the optoelectronics field. They have also been studied for applications in the sensing of environmental compounds. Here, research will display its use as a novel sensor for narcotic substances. This forensic application will be further explored to develop and eventually commercialize a complete field drug testing system for law enforcement and crime lab use, with the goal to equip law enforcement personnel with a presumptive drug testing method that is accurate, easy-to-use, safe, adaptable, and affordable. This system will consist of a narcotic drug-indicating test strip, a handheld fluorescence spectrometer manufactured in-house using relatively inexpensive parts, and a mobile app that will leverage photoemission data of the tested drug samples collected by multiple crime labs to provide the ability for sample-to-reference data matching. Law enforcement users would have the ability to rapidly identify an unknown substance by applying it to a test strip, testing it using the spectrometer, and capturing an image of the resulting photoemission and analyzing the spectral profile in search of a match with the support of a cloud database.
Show less - Date Issued
- 2017
- Identifier
- CFE0007129, ucf:52297
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007129
- Title
- Interdisciplinary Studies Students' Academic and Social Engagement: A Quantitative Study.
- Creator
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Simmons, Jessica, Boyd, Tammy, Cintron Delgado, Rosa, Beverly, Monifa, Hampton, Michael, University of Central Florida
- Abstract / Description
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This study explored interdisciplinary studies students' academic and social engagement. As the review of literature demonstrated, student engagement and satisfaction are important to retention and institutions can adopt policies and practices to foster student engagement. Because interdisciplinary studies programs often struggle to maintain relevance, fostering student engagement is one way to ensure maximum student satisfaction and retention. This study identified factors of student...
Show moreThis study explored interdisciplinary studies students' academic and social engagement. As the review of literature demonstrated, student engagement and satisfaction are important to retention and institutions can adopt policies and practices to foster student engagement. Because interdisciplinary studies programs often struggle to maintain relevance, fostering student engagement is one way to ensure maximum student satisfaction and retention. This study identified factors of student engagement that were positively related to satisfaction and confirmed that requiring core interdisciplinary studies courses had a positive impact on engagement.A quantitative instrument, the Interdisciplinary Studies Student Engagement Survey, was adapted from the National Survey of Student Engagement questionnaire to collect self-reported responses. The following eight factors of student engagement were found to be relevant: (a) diversity-related activities, (b) shared understanding and experiences, (c) interaction with peers, (d) interaction with faculty members, (e) active and collaborative learning, (f) integrated learning, (g) out-of-class experiences, and (h) academic challenge. Respondents reported the most frequent participation in integrated learning and the least frequent participation in out-of-class experiences. It was determined that students with nontraditional characteristics tended to participate more frequently in academic engagement, whereas students with traditional characteristics tended to participate more in social engagement. In addition, enrollment in mandatory interdisciplinary core courses was found to positively influence engagement in seven of the eight identified factors. Enrollment in core courses was also positively related to satisfaction. Finally, all eight engagement factors positively correlated with satisfaction to some degree.
Show less - Date Issued
- 2011
- Identifier
- CFE0004168, ucf:49072
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004168
- Title
- Electrochemical Studies of Nanoscale Composite Materials as Electrodes in PEM Fuel Cells.
- Creator
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Anderson, Jordan, Zhai, Lei, Blair, Richard, Hampton, Michael, Zou, Shengli, Seal, Sudipta, University of Central Florida
- Abstract / Description
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Polymer electrolyte membrane fuel cells (PEMFCs) have recently acquired much attention as alternatives to combustion engines for power conversion. The primary interest in fuel cell technology is the possibility of 60% power conversion efficiency as compared to the 30% maximum theoretical efficiency limited to combustion engines and turbines. Although originally conceived to work with hydrogen as a fuel, difficulties relating to hydrogen storage have prompted much effort in using other fuels....
Show morePolymer electrolyte membrane fuel cells (PEMFCs) have recently acquired much attention as alternatives to combustion engines for power conversion. The primary interest in fuel cell technology is the possibility of 60% power conversion efficiency as compared to the 30% maximum theoretical efficiency limited to combustion engines and turbines. Although originally conceived to work with hydrogen as a fuel, difficulties relating to hydrogen storage have prompted much effort in using other fuels. Small organic molecules such as alcohols and formic acid have shown promise as alternatives to hydrogen in PEMFCs due to their higher stability at ambient conditions. The drawbacks for using these fuels in PEMFCs are related to their incomplete oxidation mechanisms, which lead to the production of carbon monoxide (CO). When carbon monoxide is released in fuel cells it binds strongly to the platinum anode thus limiting the adsorption and subsequent oxidation of more fuel. In order to promote the complete oxidation of fuels and limit poisoning due to CO, various metal and metal oxide catalysts have been used.Motivated by promising results seen in fuel cell catalysis, this research project is focused on the design and fabrication of novel platinum-composite catalysts for the electrooxidation of methanol, ethanol and formic acid. Various Pt-composites were fabricated including Pt-Au, Pt-Ru, Pt-Pd and Pt-CeO2 catalysts. Electrochemical techniques were used to determine the catalytic ability of each novel composite toward the electrooxidation of methanol, ethanol and formic acid. This study indicates that the novel composites all have higher catalytic ability than bare Pt electrodes. The increase in catalytic ability is mostly attributed to the increase in CO poison tolerance and promotion of the complete oxidation mechanism of methanol, ethanol and formic acid. Formulations including bi- and tri-composite catalysts were fabricated and in many cases show the highest catalytic oxidation, suggesting tertiary catalytic effects. The combination of bi-metallic composites with ceria also showed highly increased catalytic oxidation ability. The following dissertation expounds on the relationship between composite material and the electrooxidation of methanol, ethanol and formic acid. The full electrochemical and material characterization of each composite electrode is provided.
Show less - Date Issued
- 2012
- Identifier
- CFE0004510, ucf:49264
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004510
- Title
- Mechanochemical Synthesis of Fuels from Sustainable Sources Utilizing Solid Catalysts.
- Creator
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Todd, Jacob, Zhai, Lei, Blair, Richard, Hampton, Michael, Harper, James, Rahman, Talat, University of Central Florida
- Abstract / Description
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The transition to biofuels as a means of curbing the emissions of greenhouse gases has given rise to several questions such as what to use as the feedstock and how to cost effectively process them.(&)nbsp; The production of bio-derived chemicals presents challenges in synthesis and in use as a drop-in fuel replacement.(&)nbsp; Through the use of mechanochemistry reaction pathways can be utilized that allow the efficient production of biofuels and bioderived chemicals.(&)nbsp; To this end...
Show moreThe transition to biofuels as a means of curbing the emissions of greenhouse gases has given rise to several questions such as what to use as the feedstock and how to cost effectively process them.(&)nbsp; The production of bio-derived chemicals presents challenges in synthesis and in use as a drop-in fuel replacement.(&)nbsp; Through the use of mechanochemistry reaction pathways can be utilized that allow the efficient production of biofuels and bioderived chemicals.(&)nbsp; To this end mechanically driven esterification and transesterification reactions were studied.(&)nbsp; It was found that the acid base properties of solid catalysts was critical to efficient reactions.(&)nbsp; Further investigation into mechanocatalytic reaction resulted in a reaction scheme where glucose can be used as a feedstock for the production of propane from glucose through a retro aldol reaction followed by hydrodeoxygenation.(&)nbsp; The use of mechanochemistry facilitates the efficient synthesis of important energy molecules and allows new reaction pathways to be exploited.(&)nbsp; The efficient production of bio-derived chemicals will reduce our impact on the environment.(&)nbsp;(&)nbsp;
Show less - Date Issued
- 2017
- Identifier
- CFE0006809, ucf:51805
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006809
- Title
- Assessment of molecular interactions via magnetic relaxation: a quest for inhibitors of the anthrax toxin.
- Creator
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Santiesteban, Oscar, Perez Figueroa, Jesus, Liao, Yi, Yestrebsky, Cherie, Hampton, Michael, Lambert, Stephen, University of Central Florida
- Abstract / Description
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Anthrax is severe disease caused by the gram-positive Bacillus anthracis that can affect humans with deadly consequences. The disease propagates via the release of bacterial spores that can be naturally found in animals or can be weaponized and intentionally released into the atmosphere in a terrorist attack. Once inhaled, the spores become activated and the anthrax bacterium starts to reproduce and damage healthy macrophages by the release of the anthrax toxin. The anthrax toxin is composed...
Show moreAnthrax is severe disease caused by the gram-positive Bacillus anthracis that can affect humans with deadly consequences. The disease propagates via the release of bacterial spores that can be naturally found in animals or can be weaponized and intentionally released into the atmosphere in a terrorist attack. Once inhaled, the spores become activated and the anthrax bacterium starts to reproduce and damage healthy macrophages by the release of the anthrax toxin. The anthrax toxin is composed of three virulent factors: (i) anthrax protective antigen (APA), (ii) anthrax lethal factor (ALF), and (iii) anthrax edema factor (AEF) that work in harmony to effectuate the lethality associated with the disease. Out of the two internalized factors, ALF has been identified to play a critical role in cell death. Studies in animals have shown that mice infected with an anthrax strain lacking ALF survive the infection whereas when ALF is present the survivability of the mice is eliminated. Although the current therapy for anthrax is antibiotic treatment, modern medicine faces some critical limitations when combating infections. Antibiotics have proven very efficient in eliminating the bacterial infection but they lack the ability to destroy or inhibit the toxins released by the bacteria. This is a significant problem since ALF can remain active in the body for days after the infection is eliminated with no way of inhibiting its destructive effects. The use of inhibitors of ALF is an attractive method to treat the pathogenesis of anthrax infections. Over the last decade several inhibitors of the enzymatic activity of ALF have been identified. In order to identify inhibitors of ALF a variety of screening approaches such as library screenings, Mass Spectroscopy- based screenings and scaffold-based NMR screening have been used. Results from these screening have yielded mainly small molecules that can inhibit ALF in low micromolar to nanomolar concentrations. Yet, although valuable, these results have very little significance with regards to treating ALF in a real-life scenario since pharmaceutical companies are not willing to invest in further developing these inhibitors. Furthermore, the low incidence of inhalation anthrax, the lack of a market for an ALF inhibitor, and the expenses associated with the approval process of the FDA, have hindered the motivation of pharmaceutical companies to pursuit these kind of drugs. Therefore we have screened a small-molecule library of FDA approved drugs and common molecules in order to identify currently approved FDA drugs that can also inhibit ALF (Chapter III). The screening revealed that five molecules: sulindac, fusaric acid, naproxen, ketoprofen and ibuprofen bound to either ALF or APA with sulindac binding both. Additionally, we have developed a nanoparticle-based screening method that assesses molecular interactions by magnetic relaxation changes (Chapter II). Using this assay, we were able to accurately measure the dissociation constants of different interactions between several ligands and macromolecules. Moreover, we have used computational docking studies to predict the binding site of the identified molecules on the ALF or APA (Chapter IV). These studies predicted that two molecules sulindac and fusaric acid could be potential inhibitors of ALF since they bind at the enzymatic pocket. As a result, we tested the inhibitory potential of these molecules as well as that of the metabolic derivatives of sulindac (Chapter V). Results from these studies provided conclusive evidence that fusaric acid and sulindac were both strong inhibitors of ALF. Furthermore, the metabolic derivatives of sulindac, sulindac sulfide and sulindac sulfone also inhibited ALF. Overall, taking together these results we have discovered the alternate use of a currently used drug for the treatment of ALF pathogenesis.
Show less - Date Issued
- 2012
- Identifier
- CFE0004794, ucf:49745
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004794
- Title
- A Study of the Degradative Capabilities of the Bimetallic System: Mg(Pd/C) as Applied in the Destruction of Decafluoropentane, an Environmental Contaminant.
- Creator
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Tomlin, Douglas, Clausen, Christian, Yestrebsky, Cherie, Hampton, Michael, Elsheimer, Seth, Griffin, Timothy, University of Central Florida
- Abstract / Description
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Pollution from hydrofluorocarbons (HFCs) poses a serious challenge to the environmental community. Released from industrial operations, they have contaminated both the atmosphere and groundwater and are considered persistent in both media. For over the past 20 years, the practice of synthesizing HFCs as alternatives to chlorofluorocarbons (CFCs) has been conducted in an effort to reverse the effects of stratospheric ozone layer depletion. HFCs also exhibit desirable properties as precision...
Show morePollution from hydrofluorocarbons (HFCs) poses a serious challenge to the environmental community. Released from industrial operations, they have contaminated both the atmosphere and groundwater and are considered persistent in both media. For over the past 20 years, the practice of synthesizing HFCs as alternatives to chlorofluorocarbons (CFCs) has been conducted in an effort to reverse the effects of stratospheric ozone layer depletion. HFCs also exhibit desirable properties as precision cleaning solvents due to their low surface energies but that use has lead to releases contaminating groundwater resulting in recalcitrant pollution in the form of dense non-aqueous phase liquids (DNAPLs). Results from studies requested by the EPA have shown HFCs to exhibit developmental and neurological damage in animal life along with their impact to humans remaining not completely understood. Therefore, the potential hazards of HFCs to human health and the environment necessitates the development of an effective and environmentally responsible technology for their remediation from groundwater. The National Aeronautics and Space Administration (NASA) has employed the use of various halogenated solvents in its spacecraft cleaning operations at its facilities for many years and in that time experienced accidental releases which eventually resulted in environmental contamination. Many of the organic solvents employed in these operations consisted of halogenated compounds with most being partially chlorinated and fluorinated hydrocarbons. Through normal use and operation, releases of these materials found their way into the environs of atmosphere, soil and groundwater. Remediation of fluorinated compounds has not followed the successful path laid by clean-up technologies developed for their chlorinated counterparts. Fluorinated compounds are resistant however to those methods due to their unreactive nature stemming from the properties of the strong carbon-fluorine bond. This unique bonding property also ensures that their environmental persistence endures. One particular fluorinated groundwater contaminant, the HFC 1,1,1,2,2,3,4,5,5,5-decafluoropentane (DFP), which has been used by NASA since the late 1990's was selected as the focus of this study. For this study, various reductive metal systems were evaluated for their capability towards effective degradation of DFP. These included the metals: iron, magnesium, aluminum and zinc and several bimetallic alloys as well as on carbon support. Variations in protic solvent reaction media and acidic metal activation were also explored. The bimetallic reductive catalytic alloy Magnesium with Palladium on Carbon, Mg(Pd/C), in aqueous media proved to be the successful candidate with 100% conversion to simple hydrocarbons. Mechanistic evaluation for degradation is proposed via a series of stepwise catalytic hydrodefluorination reactions. Kinetic studies revealed degradation to obey second order reaction kinetics. Further study should be conducted optimizing an in situ groundwater delivery method for field application. Additionally, the developed technology should be assessed against other groundwater fluorocarbon pollutants; either as a method for remediating multiple fluorinated polluted sites or as a polishing agent where all other pollutants have been abated.
Show less - Date Issued
- 2012
- Identifier
- CFE0004798, ucf:49742
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004798
- Title
- Development of Novel Redox Sensors and Processes Towards Biological Applications.
- Creator
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Patel, Jigna, Yestrebsky, Cherie, Clausen, Christian, Hampton, Michael, Harper, James, Diaz, Diego, University of Central Florida
- Abstract / Description
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Research on the cure and early detection of diseases such as diabetes, Alzheimer's, and Parkinson's is becoming of great interest due to the increasing number of people affected by them every year. An accurate and quick detection of various damaging species is highly critical in treatments of such diseases not only for exploring possible cures but also for early detection. If these diseases are detected during the initial stages than the possibility of curing them is much higher. Motivated by...
Show moreResearch on the cure and early detection of diseases such as diabetes, Alzheimer's, and Parkinson's is becoming of great interest due to the increasing number of people affected by them every year. An accurate and quick detection of various damaging species is highly critical in treatments of such diseases not only for exploring possible cures but also for early detection. If these diseases are detected during the initial stages than the possibility of curing them is much higher. Motivated by this, many researchers today have developed numerous types of sensing devices that can detect various physiological and biological compounds. However, most of these sensors are enzyme based. They have several setbacks such as the lack of sensitivity, restricted selectivity, short shelf life, and biological fouling. To overcome these obstacles, we examine the use of nanoceria modified Pt and Au electrodes for the detection of glucose and reactive oxygen species such as hydrogen peroxide. Amperometric detection of glucose and hydrogen peroxide is critical for biological applications for diabetes and possible Alzheimer's and Parkinson's patients. This dissertation focuses on the exploration of non-enzymatic detection of glucose and reactive oxygen species which has the prospective to be used for biological applications, in addition to an investigation of an odor control technology that uses these reactive oxygen species for the treatment of wastewater plants. The combination of bi-metallic composites with nanoceria showed increased oxidation ability towards glucose and hydrogen peroxide. The following dissertation expands on the relationship between bi-metallic nanoceria composite materials and its electro-oxidation of glucose and hydrogen peroxide towards biological sensing along with an investigation of an odor control technology that utilizes generates hydroxyl radical fine particle mist for the degradation of hydrogen sulfide odor in wastewater treatment plants.
Show less - Date Issued
- 2013
- Identifier
- CFE0005227, ucf:50585
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005227
- Title
- The Behavior of Cerium Oxide Nanoparticles in Polymer Electrolyte Membranes in Ex-Situ and In-Situ Fuel Cell Durability Tests.
- Creator
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Pearman, Benjamin, Hampton, Michael, Blair, Richard, Clausen, Christian, Seal, Sudipta, Campiglia, Andres, Yestrebsky, Cherie, Mohajeri, Nahid, University of Central Florida
- Abstract / Description
-
Fuel cells are known for their high efficiency and have the potential to become a major technology for producing clean energy, especially when the fuel, e.g. hydrogen, is produced from renewable energy sources such as wind or solar. Currently, the two main obstacles to wide-spread commercialization are their high cost and the short operational lifetime of certain components.Polymer electrolyte membrane (PEM) fuel cells have been a focus of attention in recent years, due to their use of...
Show moreFuel cells are known for their high efficiency and have the potential to become a major technology for producing clean energy, especially when the fuel, e.g. hydrogen, is produced from renewable energy sources such as wind or solar. Currently, the two main obstacles to wide-spread commercialization are their high cost and the short operational lifetime of certain components.Polymer electrolyte membrane (PEM) fuel cells have been a focus of attention in recent years, due to their use of hydrogen as a fuel, their comparatively low operating temperature and flexibility for use in both stationary and portable (automotive) applications.Perfluorosulfonic acid membranes are the leading ionomers for use in PEM hydrogen fuel cells. They combine essential qualities, such as high mechanical and thermal stability, with high proton conductivity. However, they are expensive and currently show insufficient chemical stability towards radicals formed during fuel cell operation, resulting in degradation that leads to premature failure. The incorporation of durability improving additives into perfluorosulfonic acid membranes is discussed in this work.Cerium oxide (ceria) is a well-known radical scavenger that has been used in the biological and medical field. It is able to quench radicals by facilely switching between its Ce(III) and Ce(IV) oxidation states.In this work, cerium oxide nanoparticles were added to perfluorosulfonic acid membranes and subjected to ex-situ and in-situ accelerated durability tests.The two ceria formulations, an in-house synthesized and commercially available material, were found to consist of crystalline particles of 2 (-) 5 nm and 20 (-) 150 nm size, respectively, that did not change size or shape when incorporated into the membranes.At higher temperature and relative humidity in gas flowing conditions, ceria in membranes is found to be reduced to its ionic form by virtue of the acidic environment. In ex-situ Fenton testing, the inclusion of ceria into membranes reduced the emission of fluoride, a strong indicator of degradation, by an order of magnitude with both liquid and gaseous hydrogen peroxide. In open-circuit voltage (OCV) hold fuel cell testing, ceria improved durability, as measured by several parameters such as OCV decay rate, fluoride emission and cell performance, over several hundred hours and influenced the formation of the platinum band typically found after durability testing.
Show less - Date Issued
- 2012
- Identifier
- CFE0004789, ucf:49731
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004789