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Title: ELECTRICAL PROPERTIES OF REACTIVE MAGNETRON SPUTTERED VANADIUM OXIDE THIN FILMS.
Creator: Lam, Vu, Sundaram, Kalpathy, University of Central Florida
Abstract / Description: It is well known that vanadium oxide can take many different forms. However for this study, only the amorphous phase was investigated. Amorphous vanadium oxide (VOx) thin films were deposited on thermally grown silicon dioxide by DC magnetron sputtering using a vanadium metal target in an argon / oxygen atmosphere. The driving force of this study was to investigate the temperature coefficient of resistance (TCR) and low resistivity in the amorphous films. Sheet resistance is very sensitive to...
Show moreIt is well known that vanadium oxide can take many different forms. However for this study, only the amorphous phase was investigated. Amorphous vanadium oxide (VOx) thin films were deposited on thermally grown silicon dioxide by DC magnetron sputtering using a vanadium metal target in an argon / oxygen atmosphere. The driving force of this study was to investigate the temperature coefficient of resistance (TCR) and low resistivity in the amorphous films. Sheet resistance is very sensitive to small changes in temperature, making amorphous VOx very attractive to thermal sensor applications such as infrared detectors. To form the vanadium oxide, physical vapor deposition of vanadium metal at 200 Watts of DC power was used with varied amounts of oxygen in a primary argon atmosphere. During deposition, the concentration of oxygen was controlled by using a 20:80 mixture of O2 and Ar in conjunction with high purity Ar supply. Flow control techniques were derived and calculated to predict the percentage of oxygen before and during deposition to understand the reaction between the vanadium metal and oxygen. Concentrations of O2 in the deposition chamber were varied from 0.025% to 3.000% with the purpose of gaining an understanding of the affects of O2 concentration in amorphous VOx films. TCR and resistivity measurements were performed to characterize the films. The results showed a resistivity decrement with decreasing oxygen concentration. The films with lower concentrations of oxygen were found to have better TCR values then those with higher percentages of oxygen. To further reduce the resistivity of the VOx and maintain the TCR value, co-sputtering of noble metals (gold and platinum) with VOx was studied. The metals were co-sputtered at various power settings with the vanadium oxide reactive process at a fixed percentage of oxygen. The TCR and resistivity results showed that the additions of Au and Pt into VOx reduced the resistivity. However, only Au was found to improve TCR value. The results of these experiments showed that by reducing the amount of oxygen in the film, the ratio between TCR and resistivity further improved. Mechanical limits of the gas delivery system and the relatively low sensitivity to oxygen detection, gas flow control is limited when sputtering with only a single target. Several targets were therefore used during sputtering to allow for higher gas flows thereby increasing the effective sensitivity of the oxygen control. To increase the amount of available vanadium and still have a sufficient amount of detectable oxygen present, four vanadium targets were sputtered simultaneously. The measurements appeared to have a trend of increase in TCR values with a decrease in resistivity. For an ideal case, thermal sensor material should incorporate high TCR and low resistivity for better sensitivity. The amorphous vanadium oxide deposited by 4 vanadium targets seems to satisfy that requirement. In conclusion, a novel method has been established to fabricate amorphous vanadium oxide thin films with high TCR and low resistivity for infrared detectors.
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Date Issued: 2006
Identifier: CFE0001424, ucf:47049
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001424

Title: EXPLORATION OF BIOACTIVE COMPOUNDS OF GINGER AS A FOLK REMEDY FOR MIGRAINES.
Creator: Aleger, Nathan Vorbes, Elsheimer, Seth, Samsam, Mohtashem, University of Central Florida
Abstract / Description: Ginger (Zingiber Officinale) has been used in Asia for centuries to treat various ailments. Ginger has been reported to alleviate migraine pain via four bioactive compounds that can reduce nitric oxide synthase (NOS) resulting in the inhibition of nitric oxide (NO). The inhibition of nitric oxide results in the vasoconstriction of the intracranial blood vessels alleviating migraine pain. It is hypothesized that ginger has structural similarities to vasoconstrictor drugs causing similar...
Show moreGinger (Zingiber Officinale) has been used in Asia for centuries to treat various ailments. Ginger has been reported to alleviate migraine pain via four bioactive compounds that can reduce nitric oxide synthase (NOS) resulting in the inhibition of nitric oxide (NO). The inhibition of nitric oxide results in the vasoconstriction of the intracranial blood vessels alleviating migraine pain. It is hypothesized that ginger has structural similarities to vasoconstrictor drugs causing similar receptor interactions. A review of the bioactive compounds in ginger and popular vasoconstrictor drugs was done to determine structural similarities. The results of this study show that the compounds in ginger share no structural similarities with vasoconstrictor drugs used in the treatment of migraine headaches.
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Date Issued: 2017
Identifier: CFH2000251, ucf:45962
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000251

Title: Characterization, Morphology, Oxidation, and Recession of Silicon Nanowires Grown by Electroless Process.
Creator: Mertens, Robert, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Chow, Louis, Wahid, Parveen, Blair, Richard, University of Central Florida
Abstract / Description: This dissertation presents heretofore undiscovered properties of Silicon Nanowires (SiNWs) grown by electroless process and presents mathematical solutions to the special problems of the oxidation and diffusion of dopants for SiNWs. Also presented here is a mathematical description of morphology of oxidized SiNWs. This dissertation is comprised of several discussions relating to SiNWs growth, oxidation, morphology and doping.In here is presented work derived from a long-term study of SiNWs....
Show moreThis dissertation presents heretofore undiscovered properties of Silicon Nanowires (SiNWs) grown by electroless process and presents mathematical solutions to the special problems of the oxidation and diffusion of dopants for SiNWs. Also presented here is a mathematical description of morphology of oxidized SiNWs. This dissertation is comprised of several discussions relating to SiNWs growth, oxidation, morphology and doping.In here is presented work derived from a long-term study of SiNWs. Several important aspects of SiNWs were investigated and the results published in journals and conference papers. The recession of SiNWs was heretofore unreported by other research groups. In our investigations, this began as a question, (")How far into the substrate does the etching process go when this method is used to make SiNWs?(") Our investigations showed that recession did take place, was controllable and that a number of variables were responsible. The growth mechanism of SiNWs grown by electroless process is discussed at length. The relation of exposed area to volume of solution is shown, derived from experimentation. A relation of Silver used to Si removed is presented, derived from experimentation. The agglomeration of SiNWs grown by the electroless process is presented.The oxidation of SiNWs is a subject of interest to many groups, although most other groups work with SiNWs grown by the VLS process, which is more difficult, time-consuming and expensive to do. The oxidation of planar Silicon (Si) is still a subject of study, even today, after many years of working with and refining our formulae, because of the changing needs of this science and industry. SiNWs oxidation formulae are more complicated than those for planar Si, partly because of their morphology and partly because of their scale. While planar Si only presents one orientation for oxidation, SiNWs present a range of orientations, usually everything between (<)100(>) and (<)110(>) ( the (<)111(>) orientation is usually not presented during oxidation). This complicates the post-oxidation morphology to the extent that, subsequent to oxidation, SiNWs are more rectangular than cylindrical in shape. After etching to remove an oxidation layer from the SiNWs, the rectangular shape shifts 90(&)deg; in orientation.In traditional oxidation, the Deal-Grove formulae are used, but when the oxidation must take place in very small layers, such as with nanoscale devices, the Massoud formulae have to be used. However, even with Massoud, these formulae are not as good because of the morphology. Deal-Grove and Massoud formulae are intended for use with planar Si. We present some formulae that show the change in shape of SiNWs during oxidation, due to their morphology.The diffusion of dopants in SiNWs is a subject few research groups have taken up. Most of the groups who have, use SiNWs grown by the VLS method to make measurements and report findings. In order to measure the diffusion of dopants in SiNWs, a controllable diameter is needed. There are a number of ways to measure diffusion in SiNWs, but none of the ones used so far apply well to SiNWs grown by electroless process. Usually these groups present some mathematical formulae to predict diffusion in SiNWs, but these seem to lack mathematical rigor. Diffusion is a process that is best understood using Fick's Laws, which are applied to the problem of SiNWs in this dissertation.Diffusion is a science with a long history, going back at least 150 years. There are many formulae that can be used in the most common diffusion processes, but the processes involved with the diffusion of dopants in SiNWs is more complex than the simple diffusion processes that are fairly well-understood. Diffusion doping of SiNWs is a multiphase process that is more complex, first because it is multiphase and second because the second step involves a multiplicity of diffusing elements, plus oxidation, which brings on the problems of moving boundaries.In this dissertation, we present solutions to these problems, and the two-step diffusion process for SiNWs.
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Date Issued: 2012
Identifier: CFE0004412, ucf:49366
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004412

Title: The Role of Mitochondrial Omi/HtrA2 Protease in Protein Quality Control and Mitophagy.
Creator: Ambivero, Camilla, Zervos, Antonis, Teter, Kenneth, Siddiqi, Shadab, Self, William, University of Central Florida
Abstract / Description: Omi/HtrA2 is a nuclear encoded mitochondrial serine protease with dual and opposite functions that depend entirely on its subcellular localization. During apoptosis it is released to the cytoplasm where it participates in cell death. While confined in the mitochondria it has a pro-survival function that may involve the regulation of protein quality control (PQC) and mitochondrial homeostasis. We used the yeast two-hybrid system to dissect Omi/HtrA2's pathway by identifying novel interactors...
Show moreOmi/HtrA2 is a nuclear encoded mitochondrial serine protease with dual and opposite functions that depend entirely on its subcellular localization. During apoptosis it is released to the cytoplasm where it participates in cell death. While confined in the mitochondria it has a pro-survival function that may involve the regulation of protein quality control (PQC) and mitochondrial homeostasis. We used the yeast two-hybrid system to dissect Omi/HtrA2's pathway by identifying novel interactors and substrates. Our studies revealed a novel function of Omi/HtrA2 in the regulation of a Lys-63 deubiquitinating (DUB) complex. In addition, we found the mechanism by which Omi/HtrA2 protease participates in mitophagy by directly regulating the protein level of Mulan E3 ubiquitin ligase, especially during mitochondrial stress.Abro1 is a scaffold protein of the DUB complex known as BRISC (BRCC36 isopeptidase complex). In addition, Abro1 is involved in a cytoprotective pathway and is regulated by Omi/HtrA2. Three specific interactors of Abro1 protein were identified, ATF4, ATF5 and JunD, all members of the activating protein 1 (AP-1) family. We focused our studies on ATF4 since, like Abro1, it is ubiquitously expressed and is important in cell cycle regulation and survival. Abro1's interaction with ATF4 was specific and occurred only when cells were stressed. The significance of this interaction was the translocation of Abro1 from the cytoplasm to the cell nucleus. These results establish a new cytoprotective function of cytoplasmic Omi/HtrA2 as a regulator of the BRISC DUB complex.Furthermore, we have recently identified the mitochondrial Mulan E3 ubiquitin ligase as a substrate of Omi/HtrA2 protease. Mulan, along with MARCH5/MITOL and RNF185, are the only three mitochondrial E3 ubiquitin ligases identified thus far. The function of Mulan has been linked to cell growth, cell death, and autophagy/mitophagy. To investigate Mulan's function and its control by Omi/HtrA2, E2 conjugating enzymes that form a complex with Mulan E3 ligase were identified. Four specific interacting E2s were isolated, namely Ube2E2, Ube2E3, Ube2G2, and Ube2L3. To identify substrates for each unique Mulan-E2 complex, fusion baits were used in a modified yeast two-hybrid screen. Our results suggest that Mulan participates in various pathways, depending on the nature of its E2 conjugating enzyme partner. One of the interactors isolated against the Mulan-Ube2E3 bait was the GABARAP (GABAA receptor-associated protein), a member of the Atg8 family. We characterized this interaction both in vitro and in vivo and its potential role in mitophagy. Our studies defined a new pathway by which Mulan participates in mitophagy by recruiting GABARAP to the mitochondria.
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Date Issued: 2013
Identifier: CFE0004805, ucf:49752
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004805

Title: Lithographic Vertical-Cavity Surface-Emitting Lasers.
Creator: Zhao, Guowei, Deppe, Dennis, Likamwa, Patrick, Fathpour, Sasan, Sundaram, Kalpathy, University of Central Florida
Abstract / Description: Remarkable improvements in vertical-cavity surface-emitting lasers (VCSELs) have been made by the introduction of mode- and current-confining oxide optical aperture now used commercially. However, the oxide aperture blocks heat flow inside the device, causing a larger thermal resistance, and the internal strain caused by the oxide can degrade device reliability, also the diffusion process used for the oxide formation can limit device uniformity and scalability.Oxide-free lithographic VCSELs...
Show moreRemarkable improvements in vertical-cavity surface-emitting lasers (VCSELs) have been made by the introduction of mode- and current-confining oxide optical aperture now used commercially. However, the oxide aperture blocks heat flow inside the device, causing a larger thermal resistance, and the internal strain caused by the oxide can degrade device reliability, also the diffusion process used for the oxide formation can limit device uniformity and scalability.Oxide-free lithographic VCSELs are introduced to overcome these device limitations, with both the mode and current confined within the lithographically defined intracavity mesa, scaling and mass production of small size device could be possible. The 3 ?m diameter lithographic VCSEL shows a threshold current of 260 ?A, differential quantum efficiency of 60% and maximum output power density of 65 kW/cm2, and shows single-mode single-polarization operation with side-mode-suppression-ratio over 25 dB at output power up to 1 mW. The device also shows reliable operation during 1000 hours stress test with high injection current density of 142 kA/cm2. The lithographic VCSELs have much lower thermal resistance than oxide-confined VCSELs due to elimination of the oxide aperture. The improved thermal property allows the device to have wide operating temperature range of up to 190 (&)deg;C heat sink temperature, high output power density especially in small device, high rollover current density and high rollover cavity temperature. Research is still underway to reduce the operating voltage of lithographic VCSELs for high wall plug efficiency, and the voltage of 6 (&)#181;m device at injection current density of 10 kA/cm2 is reduces to 1.83 V with optimized mesa and DBR mirror structure. The lithographic VCSELS are promising to become the next generation VCSEL technology.
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Date Issued: 2012
Identifier: CFE0004634, ucf:49912
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004634

Title: VACANCY ENGINEERED DOPED AND UNDOPED NANOCRYSTALLINE RARE EARTH OXIDE PARTICLES FOR HIGH TEMPERATURE OXIDATION RESISTANT COATINGS.
Creator: THANNEERU, RANJITH, SEAL, SUDIPTA, University of Central Florida
Abstract / Description: Rare earth oxides with trivalent lattice dopants have been of great interest to researchers in the recent years due to its potential applications in catalysis and high temperature protective coatings. The ability to store oxygen in rare earths is the basis for catalysis because of the ability to change valence states which causes the presence of intrinsic oxygen vacancies in the crystal lattice. Although, several doped-rare earth oxide systems in micron scale have been investigated, the...
Show moreRare earth oxides with trivalent lattice dopants have been of great interest to researchers in the recent years due to its potential applications in catalysis and high temperature protective coatings. The ability to store oxygen in rare earths is the basis for catalysis because of the ability to change valence states which causes the presence of intrinsic oxygen vacancies in the crystal lattice. Although, several doped-rare earth oxide systems in micron scale have been investigated, the doping effect in cerium oxide nanoparticles with well characterized particle size has not been studied. The doping of ceria at that small size can be very beneficial to further improve its catalytic properties and alter the high temperature phases in alloy systems. Cost effective room temperature chemical methods are used in the current work to synthesize uniformly distributed undoped and doped (dopants: La, Nd, Sm, Gd, Y and Yb) rare earth oxide nanoparticles. In the present study, the variation of the properties in nanocrystalline ceria (NC) synthesized by microemulsion method is studied as a function of dopant size and its concentration. To further understand, the role of dopant (cation) size on the oxygen vacancy concentration, doped nanocrystalline oxide powders were analyzed by Raman Spectroscopy, X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). XRD studies showed that lattice parameter change in nanocrystalline oxide by doping trivalent rare earth elements is largely depending on size of trivalent ions. It showed that by doping larger cations (Gd3+ and Y3+) compare to Ce3+ causes lattice expansion where as smaller cations (Yb3+) leads to lattice contraction. It also showed that the lattice expansion or contraction is directly proportional to dopant concentration. The results of Raman Spectroscopy showed that the correlation length decreases resulting in increase in oxygen vacancies for larger trivalent dopants (Sm3+, Gd3+ and Y3+). However, the correlation length increases resulting in decrease in oxygen vacancies for smaller trivalent dopants (Yb3+) compare to nanocrystalline ceria. These nanostructured oxides are further applied to develop high temperature oxidation resistance coatings for austenitic steels. The present study investigates the role of oxygen vacancies in the performance of high temperature oxidation resistance as a function of various trivalent dopants and dopant concentration. NC and La3+ doped nanocrystalline ceria (LDN) particles were coated on AISI 304 stainless steels (SS) and exposed to 1243K in dry air for longer duration and subjected to cycling. The results are further compared with that of micro-ceria (MC) coatings. The coated samples showed 90% improvement in oxidation resistance compared to uncoated and MC coated steels as seen from the SEM cross-sectional studies. XRD analysis showed the presence of chromia in both NC and 20 LDN samples which is absent in uncoated steels. From SIMS depth profiles, Fe, Ni depletion zones are observed in presence of LDN coated sample indicating diffusion through the oxide layer. The role of oxygen vacancies in the nanoceria coatings on the early formation of protective chromia layer is discussed and compared to its micron counterpart. This study helps in understanding the role of oxygen vacancies to protect austenitic stainless steel at high temperature and confirms the oxygen inward diffusion rather cation outward diffusion in rare earth oxide coatings. It also gives an idea to identify the type of dopant and its concentration in nanocrystalline cerium oxide which supplies the critical oxygen partial pressure required at high temperature to form primarily impervious chromia layer.
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Date Issued: 2007
Identifier: CFE0001711, ucf:47306
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001711

Title: SELENOTRISULFIDE DERIVATIVE OF ALPHA-LIPOIC ACID: EVALUATION IN A CELL CULTURE MODEL FOR POTENTIAL USE AS A TOPICAL ANTIOXIDANT.
Creator: Alonis, Melenie, Self, William, University of Central Florida
Abstract / Description: Selenium is a required micronutrient in mammalian cells. It is incorporated in the form of selenocysteine into selenoenzymes such as glutathione peroxidase and thioredoxin reductase, and is absolutely required for activity. Thioredoxin reductase is necessary for reduction of oxidized thioredoxin and therefore plays a major role in maintaining the redox status of the cell. Glutathione peroxidase is responsible for reducing peroxides into their corresponding alcohols and water. Together, these...
Show moreSelenium is a required micronutrient in mammalian cells. It is incorporated in the form of selenocysteine into selenoenzymes such as glutathione peroxidase and thioredoxin reductase, and is absolutely required for activity. Thioredoxin reductase is necessary for reduction of oxidized thioredoxin and therefore plays a major role in maintaining the redox status of the cell. Glutathione peroxidase is responsible for reducing peroxides into their corresponding alcohols and water. Together, these selenoenzymes constitute a significant part of the cell's arsenal to defend itself against oxidative stress. Exogenous sources of oxidative stress, such as UV radiation, are capable of generating reactive oxygen species (ROS). Elevated levels of ROS can lead to covalent modifications of lipids, nucleic acids, and proteins within a cell. This damage has been implicated in the development of cancer and degenerative diseases. As the skin is the first level of defense for UV radiation, skin cancer is an obvious concern. Previous studies have demonstrated a protective effect against UV-induced cytotoxicity when selenium compounds were administered to skin cells in cell culture models. Topical selenium application to mice has also been shown to reduce UV damage to skin. Although a variety of chemical forms of selenium are available in nutritional supplements, the efficiency by which they are used for selenoprotein synthesis varies greatly. It is debated within the selenium research community which form is best for use as a supplement. In this study, we have focused on a selenotrisulfide derivative of alpha-lipoic acid (LASe). We have examined its utilization for selenoprotein synthesis through radiolabeling studies (75Se) in a human keratinocyte cell line (HaCaT). We have determined that is incorporated into selenoproteins with nearly the same efficiency as selenite and L-selenocysteine. We have also determined that LASe is far more efficient as a supplement in cell culture than selenate or L-selenomethionine, two forms of selenium commonly used as supplements. LASe was also found to protect HaCaT keratinocytes from UV- induced cytotoxicity. Cells pretreated with LASe and exposed to 500J/m2 and 750J/m2 of broadband (UVA/UVB) UV radiation showed greater survival than untreated controls in a dose –dependent manner. Cells pre-treated either with lipoic acid or selenium in the form of selenite alone also observed protection. Nonetheless, these finding are significant given that LASe was previously shown to penetrate the skin better than other forms of selenium. These results indicate that LASe has the potential for use as a topical antioxidant upon further testing in animal studies.
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Date Issued: 2005
Identifier: CFE0000663, ucf:46531
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000663

Title: DESIGN AND FABRICATION OF A FULL-FEATURED LABSCALE HYBRID ROCKET ENGINE.
Creator: Platt, Kyle, Petersen, Eric, University of Central Florida
Abstract / Description: The design, development, integration and testing of a full-featured, Lab-Scale Hybrid Rocket Engine was not only envisioned to be the chosen method of putting student payloads into space, but to be an invaluable teaching resource. The subject of the present thesis is the analysis, design, development, integration and demonstration of a lab-scale hybrid rocket motor. The overarching goal of this project was to establish a working developmental lab model from which further research can be...
Show moreThe design, development, integration and testing of a full-featured, Lab-Scale Hybrid Rocket Engine was not only envisioned to be the chosen method of putting student payloads into space, but to be an invaluable teaching resource. The subject of the present thesis is the analysis, design, development, integration and demonstration of a lab-scale hybrid rocket motor. The overarching goal of this project was to establish a working developmental lab model from which further research can be accomplished. The lab model was specifically designed to use a fuel source that could be studied in normal laboratory conditions. As such, the rocket engine was designed to use Hydroxyl Terminated Polybutadiene as the fuel and Liquid Nitrous Oxide as the oxidizer. Developing the rocket engine required the usage of several electronics modules and a software package. The custom-designed electronics modules were a Signal Conditioning & Data Amplification Interface and a Data Acquisition Network. The software package was coded in Visual Basic (VB). A MathCAD regression rate computer model was designed and written to geometrically constrain the engine design. Further, the computer model allowed for the "what-if" situations to be evaluated. Using ProPep, solutions to the Equilibrium Thermodynamics Equations for the fuel and oxidizer mixture were obtained. The resultants were used as initial input to the computer model for predicting the lab-scale rocket's Chamber Pressure, Chamber Temperature, Ratio of Specific Heats and Molecular Weight. Details on the model, the rocket hardware, and the successful test firing are provided.
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Date Issued: 2006
Identifier: CFE0000972, ucf:46714
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000972

Title: POLYMER-DERIVED SI-AL-C-N CERAMICS:OXIDATION, HOT-CORROSION, AND STRUCTURAL EVOLUTION.
Creator: Wang, Yiguang, An, Linan, University of Central Florida
Abstract / Description: Polymer-derived ceramics are a new class of materials synthesized by thermal decomposition of polymer precursors. Previous studies have shown that the materials exhibit excellent thermo-mechanical properties and can be stable at temperatures up to 2000oC. Furthermore, the novel polymer-to-ceramics process enables the manipulation of the ceramic structures at the atomic/nano level by designing the chemistry of polymer precursors and controlling the pyrolysis conditions, thereby, the properties...
Show morePolymer-derived ceramics are a new class of materials synthesized by thermal decomposition of polymer precursors. Previous studies have shown that the materials exhibit excellent thermo-mechanical properties and can be stable at temperatures up to 2000oC. Furthermore, the novel polymer-to-ceramics process enables the manipulation of the ceramic structures at the atomic/nano level by designing the chemistry of polymer precursors and controlling the pyrolysis conditions, thereby, the properties of ceramics. In this dissertation, oxidation/hot-corrosion behavior and the structural evolution of Si-Al-C-N ceramics have been studied. The structural evolution and crystallization behavior of the SiCN and SiAlCN ceramics are investigated using FT-IR, XRD, and NMR. The results revealed that aluminum could greatly affect the structural evolution and crystallization behavior of polymer-derived ceramics, resulting to better stability. The oxidation kinetics of the SiCN and SiAlCN ceramics in air is determined by directly measuring the thickness of the oxide scale with SEM as a function of oxidation time. The results revealed that while the oxidation of the SiCN ceramics follows parabolic kinetics in all of the ranges of testing temperatures, oxidation of the SiAlCN ceramics is complicated: their oxidation rates are similar to that of SiCN ceramics at the earlier stage, but they decrease to very low levels after a certain time. The oxidation rate of the SiAlCN ceramics is more than an order of magnitude lower than any other silicon based ceramics previously reported. The transportation behavior of oxygen through the oxide scales is studied by 18O diffusion. The results indicate that oxidation is controlled by molecular oxygen diffusing through the oxides for both SiCN and SiAlCN ceramics; however, the oxygen diffusion rate in the oxides on SiAlCN ceramics is remarkably retarded. The structures of the oxides are characterized by XRD and NMR. A structural model is advanced to account for the aluminum effect on the oxygen diffusion in the oxide. The oxidation and hot-corrosion kinetics of the SiCN and SiAlCN ceramics in water vapor are determined by measuring their weight changes as a function of annealing time. The kinetic constants, kp and kl, are obtained by fitting the weight-change data with a paralinear model. The results reveal that the SiAlCN ceramics have a much better corrosion resistance than the SiCN and CVD SiC/Si3N4. After annealing at 1400oC for 300 hours, the SiAlCN-20 still retains more than 70% of its original strength, while the SiCN only retains about 20% of its original strength. The improvement in oxidation/hot-corrosion resistance of the SiAlCN ceramics is attributed to the low activity of the SiO2 in the Al2O3-containing silica. In summary, I have developed a new class of high-temperature materials, Si-Al-C-N ceramics. It is demonstrated that these new materials have excellent oxidation and corrosion resistance and thermal stability. Together with their easy processability, the materials will find many high temperature applications such as environmental barrier coatings, ceramic matrix composites, and MEMS for harsh environments.
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Date Issued: 2006
Identifier: CFE0001017, ucf:46810
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001017

Title: ROOM TEMPERATURE SYNTHESIS AND SYSTEMATIC CHARACTERIZATION OF ULTRA-SMALL CERIA NANOPARTICLES.
Creator: Patel, Chetak, Santra, Swadeshmukul, University of Central Florida
Abstract / Description: Cerium oxide (ceria, CeO2) is a rare earth oxide that has attracted wide-spread research interest because of its unique properties such as high mechanical strength, oxygen ion conductivity, oxygen storage capacity and autocatalytic property. In recent years, researchers have discovered that ceria nanoparticles (NPs) are capable of protecting cells from free radical induced damage. Interestingly, it was found that nanometer size (~ 5 nm) ceria can scavenge free radicals quite efficiently, thus...
Show moreCerium oxide (ceria, CeO2) is a rare earth oxide that has attracted wide-spread research interest because of its unique properties such as high mechanical strength, oxygen ion conductivity, oxygen storage capacity and autocatalytic property. In recent years, researchers have discovered that ceria nanoparticles (NPs) are capable of protecting cells from free radical induced damage. Interestingly, it was found that nanometer size (~ 5 nm) ceria can scavenge free radicals quite efficiently, thus acting as an anti-oxidant. This phenomenon has been explained based on the autocatalytic property of ceria NPs. Several methods have been developed for the synthesis of ceria NPs that include flame combustion, hydroxide co-precipitation, hydrothermal/solvothermal, microemulsion, sonochemical and microwave-assisted heating methods and sol-gel method. Ceria NPs synthesized by these methods are often highly aggregated. Furthermore, large scale synthesis of monodispersed CeO2 NPs is quite challenging. Therefore it is desirable to synthesize ceria NPs in bulk quantity keeping its important properties intact, specifically free-radical scavenging property. The main goal of this study is therefore to synthesize ultra-small (< 5.0 nm), high quality monodispersed ceria NPs in large quantities. In this thesis work, I present a couple of room temperature techniques, dilute sodium hydroxide (NaOH) assisted and ethylenediamine (EN) assisted for the synthesis of nearly mono-dispersed, ultra-small (< 5 nm) and water-dispersible ceria NPs. Morphology and particle size of the ceria NPs were investigated through high resolution transmission electron microscopy (HRTEM). The HRTEM analysis confirmed the formation of 3.0 ± 0.5 nm size and 2.5 ± 0.2 nm size highly-crystalline ceria NPs when synthesized using dilute NaOH and EN as solvents, respectively. The nanostructures were characterized by X-ray diffraction (XRD) studies to determine the crystal structure and phase purity of the products. The samples were also thoroughly characterized by X-ray photoelectron spectroscopy (XPS) to determine the oxidation state of cerium ions. The presence of the +3 and +4 oxidation states in the samples was also confirmed from the XPS analysis. The co-existence of these two oxidation states is necessary for their applications as free radical scavenger. The autocatalytic behaviors of the ceria NPs were investigated through a hydrogen peroxide test and monitored by UV-visible transmission spectroscopy.
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Date Issued: 2009
Identifier: CFE0002883, ucf:48043
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002883

Title: CHARACTERIZING SPONTANEOUS FIRES IN LANDFILLS.
Creator: Moqbel, Shadi, Reinhart, Debra, University of Central Florida
Abstract / Description: Landfill fires are relatively common incidents that landfill operators encounter which have great impact on landfill structure and the environment. According to a U.S. Fire Administration report in 2001, an average of 8,300 landfill fires occurs each year in the United States, most of them in the spring and summer months. Subsurface spontaneous fires are considered the most dangerous and difficult to detect and extinguish among landfill fires. Few studies have been conducted on spontaneous...
Show moreLandfill fires are relatively common incidents that landfill operators encounter which have great impact on landfill structure and the environment. According to a U.S. Fire Administration report in 2001, an average of 8,300 landfill fires occurs each year in the United States, most of them in the spring and summer months. Subsurface spontaneous fires are considered the most dangerous and difficult to detect and extinguish among landfill fires. Few studies have been conducted on spontaneous fires in landfills. Information regarding the thermal behavior of solid waste is not available nor have measurements been made to evaluate spontaneous ignition of solid waste. The purpose of this research was to provide information concerning the initiation of spontaneous ignition incidents in landfills, and investigate the conditions favoring their occurrence. This study enabled better understanding of the self-heating process and spontaneous combustion in landfills. Effects of parameters critical to landfill operation on spontaneous combustion were determined. Spontaneous combustion occurs when materials are heated beyond the ignition temperature. Temperature rise occurs inside the landfill due to exothermic reactions which cause self-heating of the solid waste. Oxygen introduction leading to biological waste degradation and chemical oxidation is believed to be the main cause of rising solid waste temperatures to the point of ignition. A survey was distributed to landfill operators collecting information regarding spontaneous firs incidents in their landfills. Survey results raised new questions necessitating further study of subsurface fires incidents. Subsurface spontaneous fires were not restricted to any landfill geometry or type of waste (municipal, industrial, commercial, and construction and demolition). Results showed that landfill fires occur in landfills that do and do not recirculate leachate. Although new methods have been developed to detect subsurface fires, landfill operators depend primarily on visual observation of smoke or steam to detect the subsurface fires. Also, survey results indicated that excavating and covering with soil are the most widespread methods for extinguishing subsurface fires. Methane often has been suspected for initiating spontaneous subsurface firs in the landfill. However, combustible mixture of methane and oxygen requires very high temperature to ignite. In this study it was shown that spontaneous fires are initiated by solid materials with lower ignition points. Laboratory tests were conducted evaluating the effect of moisture content, oxygen concentration and leachate on spontaneous ignition of solid waste. A new procedure for testing spontaneous ignition is described based on the crossing-point method. The procedure was used to study the spontaneous combustion of solid waste and determine the auto-ignition temperature of the solid waste components and a synthesized solid waste. Correlations have been established between auto-ignition temperature, specific weight and energy content and between self-heating temperature and specific weight. Correlations indicated that compaction can help avoid spontaneous combustion in the landfill. Dense materials require higher energy to increase in temperature and limit the accessibility of oxygen. In the experimental work, moisture was found to promote both biological and chemical self-heating. Increasing moisture content lowers the solid waste permeability and absorbs more energy as it evaporates. Dissolved solids in leachate were found to promote self-heating and ignition more than distilled water. Varying oxygen concentrations indicated that heat generation occurs due to chemical oxidation even at oxygen concentration as low as 10% by volume. However, at 10% by volume oxygen, solid waste did not exhibit thermal runaway nor flammable combustion. At 0% by volume oxygen, tests results indicated occurrence of self-heating due to slow pyrolysis. A numerical one-dimensional energy model was created to simulate temperature rise in landfill for four different scenarios. Using the results from the laboratory experiment, the model estimated the heat generation in solid waste due to chemical reactions. Results from the scenario simulations indicated that moisture evaporation is the major heat sink in the landfill. The model showed that gas flow has a cooling effect due to increasing amount of evaporated water and can control the temperature inside the landfill. The model showed that a temperature higher than the biological limit can be maintained in the landfill without initiating spontaneous fire.
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Date Issued: 2009
Identifier: CFE0002589, ucf:48275
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002589

Title: Work Function Extraction of Indium Tin Oxide Used As Transparent Gate Electrode For MOSFET.
Creator: Nehate, Shraddha, Sundaram, Kalpathy, Kapoor, Vikram, Yuan, Jiann-Shiun, University of Central Florida
Abstract / Description: Recent commercialization has peaked interest in transparent conducting oxides being implemented in display technology. Indium Tin Oxide (ITO) is a popular transparent conducting oxide which has been utilized as high work function electrode in liquid crystal displays, solar cells, gas sensors and heat reflecting films. Indium Tin Oxide films exhibit excellent transmission characteristics in the visible and infrared spectrum while maintaining high electrical conductivity. High work function...
Show moreRecent commercialization has peaked interest in transparent conducting oxides being implemented in display technology. Indium Tin Oxide (ITO) is a popular transparent conducting oxide which has been utilized as high work function electrode in liquid crystal displays, solar cells, gas sensors and heat reflecting films. Indium Tin Oxide films exhibit excellent transmission characteristics in the visible and infrared spectrum while maintaining high electrical conductivity. High work function electrodes are used to inject holes into organic materials. In majority applications the ITO work function has an impact on the device performance as it affects the energy barrier height at the hetero-junction interface. Hence, the work function of ITO is of critical importance.In this thesis, the work function of ITO is extracted successfully from a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) device for the first time. Two MOSFET devices are fabricated using a four level mask under exact same conditions. Aluminum metal is used as a drain and source contact for both MOSFETs. One of the MOSFET has aluminum gate contact and transparent conducting ITO is used as gate contact for the second MOSFET. From the threshold voltage equation of both the fabricated MOSFETs, work function of ITO is extracted. Further optical transmission studies of ITO performed in the visible spectra are also reported in this study.
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Date Issued: 2016
Identifier: CFE0006364, ucf:51534
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006364

Title: Development of enzyme-free hydrogen peroxide biosensor using cerium oxide and mechanistic study using in-situ spectro-electrochemistry.
Creator: Saraf, Shashank, Seal, Sudipta, Cho, Hyoung Jin, Zhai, Lei, Heinrich, Helge, Harper, James, University of Central Florida
Abstract / Description: During recent development, it has been demonstrated that cerium oxide nanoparticles (CNPs) have exhibited catalytic activity which mimics naturally existing enzymes such as superoxide dismutase (SOD) and catalase. The underlying mechanism is attributed to the modulation of oxygen vacancies on CNPs lattice by dynamic switching of the oxidation states between Ce3+ and Ce4+ due to the electron transfer resulting from the redox reaction between CNPs and reactive oxygen species such as hydrogen...
Show moreDuring recent development, it has been demonstrated that cerium oxide nanoparticles (CNPs) have exhibited catalytic activity which mimics naturally existing enzymes such as superoxide dismutase (SOD) and catalase. The underlying mechanism is attributed to the modulation of oxygen vacancies on CNPs lattice by dynamic switching of the oxidation states between Ce3+ and Ce4+ due to the electron transfer resulting from the redox reaction between CNPs and reactive oxygen species such as hydrogen peroxide (H2O2). Thereby the redox potential of CNPs is dependent on the surface chemistry i.e. the surface concentration of Ce3+ and Ce4+ Currently, the ratio of Ce3+/ Ce4+ in CNPs is characterized ex-situ using XPS or TEM which involves sample drying and exposure to high energy X-rays and electron beam, respectively. Sample drying and high energy beam exposure could lead to sample deterioration. The goal of the study is to explore a technique to characterize CNPs in-situ and identify the surface chemistry of CNPs. The in-situ investigation of CNPs was carried using spectroelectrochemistry wherein the electrochemical and optical measurements are carried out simultaneously. Detailed optical characterization of two different CNPs having different catalytic activity were carried under oxidation and reduction environments. Analysis of spectra revealed widely different redox potential for CNPs which was a function of pH and composition of buffer solution. In second part of dissertation a suitable surface chemistry of CNPs is investigated to replace the enzyme in biosensor assembly to allow amperometric detection of H2O2 in physiological conditions. Upon electrochemical investigation of the physio-chemical properties of CNPs, it was found that CNPs having higher surface concentration of Ce4+ as compared to Ce3+ oxidation states, demonstrated increased catalytic activity towards H2O2. The addition of CNPs resulted in 5 orders of increment in amperometric current with a response time of 400 msec towards detection of H2O2 and exhibited excellent selectivity in presence of interfering species. Additionally, cerium oxide was successfully integrated into the biosensor assembly through the anodic electrodeposition, which allowed the transfer of electron generated from the CNPs in the redox reaction to the electrode and demonstrated successful sensing of H2O2. Furthermore, to achieve detection of H2O2 in physiological conditions, CNPs were integrated with nanoporous gold (NPG) which exhibited anti-biofouling properties. The anti-biofouling property of NPG was investigated using electrochemical techniques and showed excellent signal retention in physiological concentration of albumin proteins. The novel study targets at developing robust enzyme free biosensor by integrating the detection ability of CNPs with the anti-biofouling activity of NPG based electrode.
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Date Issued: 2016
Identifier: CFE0006498, ucf:51404
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006498

Title: Mechanochemistry for Solid-State Syntheses and Catalysis.
Creator: Restrepo, David, Blair, Richard, Kuebler, Stephen, Miles, Delbert, Clausen, Christian, Orlovskaya, Nina, University of Central Florida
Abstract / Description: Traditional methods of synthesizing inorganic materials, such as hydrothermal, sol-gel, calcination and grinding steps, can typically require use of high temperatures, expensive precursors or use of solvents. Because of the energy-intensive nature or environmental impact these techniques, there is a push, especially from an industrial perspective, to move towards greener approaches. Mechanochemistry is a solvent-free alternative technique that can be used to synthesize a variety of materials...
Show moreTraditional methods of synthesizing inorganic materials, such as hydrothermal, sol-gel, calcination and grinding steps, can typically require use of high temperatures, expensive precursors or use of solvents. Because of the energy-intensive nature or environmental impact these techniques, there is a push, especially from an industrial perspective, to move towards greener approaches. Mechanochemistry is a solvent-free alternative technique that can be used to synthesize a variety of materials under ambient conditions. Due to this, there is an increase in attention towards the use of this approach in both solid-state inorganic and organic chemistry.This dissertation reports the mechanochemical synthesis of a few inorganic materials without the need of using high temperatures or solvents. Additionally, examples are presented in which mechanochemistry is used in conjunction with a secondary technique. This mechanical activation of the precursors lead to a decrease in calcination temperature and reactions times, as well as alteration of properties or unique reaction products. The synthesis of kaolinite, vanadia nanostructures, and spinels were carried out in this fashion. Mechanical activation of the precursors allowed for reduced hydrothermal treatment times in case of both kaolinite and vanadia nanostructures and the spinels are calcined at lower temperature for shorter periods of time. In addition, we report alternative template agents than previously reported for the formation of vanadia nanotubes, and report the formation of nanorods. Choosing the appropriate amine template can alter the structure and size of the material.Isomorphously substituted mixed oxides, kaolinite and spinels (MgAl2O4 and ZnAl2O4) were synthesized through a mechanically assisted process. Kaolinites are treated hydrothermally for 1 week at 250 (&)#186;C to produce an X-ray pure crystalline material. The spinels undergo calcination as low as 500 (&)#186;C to produce a nanocrystalline material. Rare-earth metals and transition metals were used as the substitutional atom. The substituted kaolinites exhibit strong order along the c axis, but less ordering along the a and b axes. Trivalent chromium and trivalent rare-earth metals, such as La, Ce, Pr, Nd, Eu, Gd, Ho, and Er, are used to replace aluminum in the structure. Likewise, divalent and trivalent transition, such as Mn, Ni, Cu and Cr, are used as the substitutional atoms in MgAl2O4 and ZnAl2O4. Cathodoluminescence studies on the substituted Spinel structure show that Mn2+ ions can occupy both the tetrahedral or octahedral holes to give a green and red emission, respectively. On the other hand, Cr3+ ions only occupy the octahedral holes to yield a red emission, similar to that in ruby. These isomorphously substituted materials may have potential applications in catalysis or glaze materials in ceramics.Oxidized graphite, an alternative to graphite oxide and graphene, can be synthesized rapidly by mechanochemical means. Grinding urea hydrogen peroxide adduct with graphite without the need of a solvent produces a product with an oxygen content of 5-15 wt%. The byproducts of this reaction are urea and water. This material is oxidized along the edges of the sheets, allowing it to be hydrophilic while retaining the conductivity. The material can suspend in water and processing allows for films of resistivities between 50 ? cm-2 and 10 k? cm-2. It was determined that the edges are fully oxidized to yield (-)COOH groups. This process offers a scalable, environmentally benign route to large quantities of oxidized graphite.An alternative method for the synthesis of nanostructured vanadia is reported. This process involves mechanical grinding of vanadium pentoxide, V2O5, with an amine template, such as diphenylamine, theophylline, rhodamine 6G and rhodamine, prior to hydrothermal treatment. This allows for the synthesis of VOx nanotubes and nanorods dependent on which template is used. Diphenylamine, theophylline, and rhodamine B produce nanorods. Use of rhodamine 6G produces asymmetric VOx nanorods.In addition to the mixed metals oxides mentioned above, sodium and calcium tantalates are synthesized mechanically. This route does not require the need of elevated temperatures or expensive and hazardous materials. X-ray diffraction analysis of NaTaO3, Ca2Ta2O7, Ca4Ta2O9 and CaTa2O6 shows that these are the only phases detected after 4 h, 10 h, 27 h and 10 h of milling, respectively. During the synthesis of Ca2Ta2O7, an intermediate phase, Ca4Ta2O9, forms within 1 h, which reacts after 5 h to form the desired product. Reference Intensity Ratio analysis shows that the material synthesized mechanically is nanocrystalline Ca2Ta2O7.Nanocrystalline ZrSi2 can also be obtained through mechanochemical synthesis. This method allows for size control and results in crystallites ranging from 9 to 30 nm. Dilution with CaCl2 enables the size control process. A linear relationship exists between the concentration of CaCl2 and the crystallite size. Contrary to a typical self-propagating metathesis reaction, this process does not allow for self-propagation and requires continuous input of mechanical energy to continue. However, this method allows for non-passivated nanoparticles of ZrSi2, which can be incorporated into composites as a reinforcement material for several applications.Hard and ultra-compressible borides, such as ReB2 and OsB2, can be synthesized mechanically. The traditional synthesis of ReB2 requires excess boron due to treatment at high temperatures. This can lead to amorphous boron aggregating at the grain boundaries, which in turn, this would degrade the properties of the material. The mechanochemical approach requires mechanical treatment of Re and B powders in stoichiometric quantities for 80 h. Mechanical synthesis of OsB2 powders requires a 1:3 ratio of Os and B powders. After 12 h of milling time, h-OsB2 begins to form, and is the major phase present after 18 h. The lattice parameters corresponding to the hexagonal OsB2 were determined to be a = b = 2.9047 (&)#197;, c = 7.4500 (&)#197;, ? = ? = 90(&)#186;, ? = 120(&)#186;. Treatment of the OsB2 powder at 1050 (&)#186;C under vacuum for 6 days did not induce a phase change, suggesting the hexagonal phase is very stable.Mechanocatalysis of the depolymerization of cellulose and hydrogenation of olefins over BN are reported as well. Heterogeneous catalysis is difficult to apply to solids, such as cellulose. However, mechanical grinding of kaolin and cellulose allows for the catalysis to occur in the solid state. This process allows for a variety of different biomasses to be used as feedstock without inhibition. Kaolinite was found to be the best acid catalyst due to high surface acidity and its layered structure, allowing for up to 84% conversion of the cellulose to water-soluble compounds. This process allows for reduction of waste, insensitivity of feedstock, multiple product pathways and scalability.Hydrogenation reactions are carried out using transition-metals catalysts. These metals have desirable catalytic properties not seen in main group elements, but there is growing concern over their use. A metal-free heterogeneous hydrogenation catalyst based on frustrated Lewis pairs would significantly reduce the health, environmental, and economic concerns associated with these metal-based catalysts. We report the first metal-free heterogeneous hydrogenation catalyst. Hydrogenation of trans-cinnamic acid is carried out over defect-laden h-BN. The reactor we use is designed to maximize the defects produced in BN sheets. The introduction of defects in BN creates frustrated Lewis pairs. DFT calculations show that the carbon double bond is weakened over boron substitution for nitrogen sites, vacancies of both boron and nitrogen, and Stone-Wales defects.A new method for crystalline germanium deposition occurring at lower temperatures (210-260 (&)#186;C) is reported. This method involves mechanical treatment of the precursors to reduce the particle size. A ground mixture of Ge and CuI are heated under vacuum to synthesize GeI2. In situ disproportionation of this compound at 210 (&)#186;C allows for the deposition of polycrystalline Ge films onto a both glass and polymer substrates. The rate of deposition is found to be 25 ng min-1. The byproducts of this process are GeI2, GeI4 and Cu3Ge, which are valuable precursors for the synthesis of germanium nanostructures and organogermanium compounds.Mechanochemistry is also utilized for the synthesis of trisubstituted pnictides. Mechanochemical treatment of bromobenzene with either Na3Sb or Na3Bi allows for the formation of triphenylstibine or triphenylbismuthine, respectively. The synthesis of the alkali metals pnictide precursors is reported as well. The synthesis of triphenylstibine produces SbPh3 as the major product from the reaction. The synthesis of triphenylbismuthine produces more Wurtz-type coupling products, which are due to the BiPh3 acting as a catalyst. Tributyl and triphenyl analogues are reported as well. The trialkylated analogues for both Sb and Bi produce more Wurtz type coupling products. This would allow for a more cost effective and scalable, alternative methods than what is currently in use today.
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Date Issued: 2013
Identifier: CFE0004741, ucf:49785
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004741

Title: Molecular Mechanisms involved in inflammatory angiogenesis induced by monocyte chemotactic protein induced protein-1 (MCPIP1).
Creator: Roy, Arpita, Kolattukudy, Pappachan, Ebert, Steven, Parthasarathy, Sampath, Self, William, University of Central Florida
Abstract / Description: Major diseases such as cardiovascular diseases, diabetes, obesity and tumor growth are known to involve inflammatory angiogenesis. MCP-induced protein 1 (MCPIP1) encoded by ZC3H12A gene, was reported to promote angiogenesis and is addressed in my dissertation as MCPIP. The mechanism/s involved in the angiogenic differentiation induced by MCPIP was however unknown. The aim of this study was to bridge this gap in our knowledge and delineate the molecular mechanisms and sequential processes...
Show moreMajor diseases such as cardiovascular diseases, diabetes, obesity and tumor growth are known to involve inflammatory angiogenesis. MCP-induced protein 1 (MCPIP1) encoded by ZC3H12A gene, was reported to promote angiogenesis and is addressed in my dissertation as MCPIP. The mechanism/s involved in the angiogenic differentiation induced by MCPIP was however unknown. The aim of this study was to bridge this gap in our knowledge and delineate the molecular mechanisms and sequential processes involved in angiogenesis mediated via MCPIP. To determine if angiogenesis induced by inflammatory cytokines, TNF-?, IL-1? and IL-8 is mediated via induction of MCPIP, knockdown of MCPIP by its specific siRNA, in human umbilical vein endothelial cells was performed. Oxidative stress, ER stress and autophagy are known to be involved in mediating inflammation. We hypothesized that MCPIP-induced angiogenic differentiation is mediated via induction of oxidative stress, ER stress and autophagy. Chemical inhibitors and specific gene knockdown approach were used to inhibit each process postulated. Oxidative stress was inhibited by apocynin or cerium oxide nanoparticles or knockdown of NADPH oxidase subunit, phox47. Endoplasmic reticulum (ER) stress was blocked by tauroursodeoxycholate or knockdown of ER stress signaling protein IRE-1 and autophagy was inhibited by the use of 3?methyl adenine, or LY 294002 or by specific knockdown of beclin1. Matrigel assay was used as an in vitro tool to assay angiogenic differentiation. Inhibition of each step inhibited the subsequent steps postulated. The results reveal that angiogenesis induced by inflammatory agents is mediated via sequential induction of MCPIP that causes oxidative and nitrosative stress resulting in ER stress leading to autophagy required for angiogenesis. MCPIP has deubiquitinase and anti-dicer RNase activities. If and how the dual enzymatic activities of MCPIP mediate angiogenesis was unknown. Our results showed that hypoxia-induced angiogenesis is mediated via MCPIP. MCPIP deubiquitinated ubiquitinated hypoxia-inducible factor (HIF-1?) and the stabilized HIF-1? entered the nucleus to promote the transcription of its target genes, cyclooxygenase-2 and vascular endothelial growth factor causing the activation of p38 MAP kinase involved in angiogenesis. MCPIP expression promoted angiogenesis by inhibition of thrombospondin-1 synthesis via induction of silent information regulator (SIRT)-1 and/or via suppression of VEG-inhibitor levels caused by inhibition of NF-?B activation. MCPIP inhibited the production of the anti-angiogenic microRNAs (miR)-20b and miR-34a that repress the translation of HIF-1? and SIRT-1, respectively. Cells expressing the RNase-dead mutant of MCPIP, D141N, that had lost the ability to induce angiogenesis had deubiquitinase activity but did not inhibit the production of miR-20b and miR-34a. Mimetics of miR-20b and miR-34a inhibited MCPIP-induced angiogenesis. These results show for the first time that both deubiquitinase and anti-dicer RNase activities of MCPIP are involved in inflammatory angiogenesis. Results from our study delineate key processes that could be potential targets for therapeutic intervention against inflammatory angiogenesis.
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Date Issued: 2012
Identifier: CFE0004793, ucf:49760
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004793

Title: Cerium oxide Nanoparticles: Their Phosphatase Activity and its Control.
Creator: Dhall, Atul, Self, William, Seal, Sudipta, Zervos, Antonis, University of Central Florida
Abstract / Description: Cerium oxide nanoparticles are established scavengers of reactive oxygen and nitrogen species. They have many potential biomedical applications that depend on their physicochemical properties and mode of preparation. Recent studies have found these nanoparticles possess phosphatase mimetic activity. Studying such catalytic activities will qualify their biomedical applications and render information on their bioavailability and potential toxicity.Two oxidation states of cerium exist in these...
Show moreCerium oxide nanoparticles are established scavengers of reactive oxygen and nitrogen species. They have many potential biomedical applications that depend on their physicochemical properties and mode of preparation. Recent studies have found these nanoparticles possess phosphatase mimetic activity. Studying such catalytic activities will qualify their biomedical applications and render information on their bioavailability and potential toxicity.Two oxidation states of cerium exist in these nanoparticles (3+ or 4+). It is hypothesized that the oxidation state of cerium in the nanoparticles determines the amount of adsorbed water on the crystal lattices. This in turn governs their activity as phosphatases. Nanoparticles with higher levels of cerium in the 4+ state exhibit phosphatase activity while those with higher levels of cerium in the 3+ state do not. This phosphatase activity may be controlled with the addition of inhibitory anions. It is hypothesized that anions with structures similar to phosphate can inhibit phosphatase activity by leading to the production of complexes on the surface of cerium oxide nanoparticles.Substrates that were used to test this activity include para-nitrophenyl phosphate (pNPP), 4-methylumbelliferyl phosphate (MUP) and adenosine triphosphate (ATP). To highlight the role of adsorbed water, we also performed experiments on pNPP with methanol as a solvent. The activity was measured by absorbance (pNPP and ATP) or fluorescence (MUP) and reported as nmol of phosphate/min. In some cases this rate was calculated through coupled reactions or by measuring the rate of formation of other colored products formed along with the release of phosphate such as pNP (para-nitrophenol).The phosphatase activity increased as the amount of adsorbed water increased implying that the abundance of adsorbed water makes the surface of 4+ ceria nanoparticles more active. Phosphatase activity for all the substrates exhibited Michaelis-Menten kinetics. Although the phosphatase activity of these nanoparticles is slow (turnover rate) as compared to real biological phosphatases, it can be used as a model catalytic activity to follow other catalytic activities that are associated with nanoparticles that have an abundance of cerium in the 4+ state, such as catalase activity. These results also provide information on the nature of the active sites involved in the catalytic activities associated with these nanoparticles.We identified three inhibitors, tungstate, molybdate and arsenate, which decreased the phosphatase activity of these nanoparticles in a dose dependent manner. Vmax, Km and Ki values were determined by varying substrate concentrations in the presence and absence of inhibitors. A partial mixed inhibition model was fit for each of these inhibitors.Summary: Phosphatase activity of cerium oxide nanoparticles with higher levels of cerium in the 4+ oxidation state was used as a model catalytic activity to study the nature of the active sites involved in catalysis. The study of inhibitors can reveal more information as to the surface binding of substrates in catalysis.
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Date Issued: 2014
Identifier: CFE0005603, ucf:50261
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005603

Title: Evaluation of Iron and Manganese Control for a Volcanic Surface Water Supply Treated with Conventional Coagulation, Sedimentation and Filtration Processes.
Creator: Hall, Christine, Duranceau, Steven, Lee, Woo Hyoung, Randall, Andrew, University of Central Florida
Abstract / Description: A research project assessing the effectiveness of potassium permanganate (KMnO4) for the treatment of iron (Fe) and manganese (Mn) has been conducted by the University of Central Florida (UCF) on behalf of the United States Navy with regards to the water supply on the island of Guam, located in the Marianas Islands. The study consisted of three basic investigative components: one that examined the use of potassium permanganate for iron and manganese control for Fena Lake, a second that...
Show moreA research project assessing the effectiveness of potassium permanganate (KMnO4) for the treatment of iron (Fe) and manganese (Mn) has been conducted by the University of Central Florida (UCF) on behalf of the United States Navy with regards to the water supply on the island of Guam, located in the Marianas Islands. The study consisted of three basic investigative components: one that examined the use of potassium permanganate for iron and manganese control for Fena Lake, a second that examined the existing unit operations that comprised the Navy's water treatment plant (NWTP), and a third that examined iron and manganese field sampling analytical procedures.In the first and primary component of the research, surface water from Fena Lake located within the Naval Magazine in proximity of Santa Rita, Guam was collected at several different lake depths and initially analyzed for iron and manganese using inductively coupled plasma. Subsequent aliquots of Fena Lake collected at the various water depths were transferred to jars then dosed with varying amounts of potassium permanganate after which iron and manganese content was determined. The jars were covered to simulate actual lake to plant transfer conditions experienced at the Navy's on-island facilities. A portion of the jars was dosed with potassium permanganate prior to metals analysis in order to allow for comparisons of baseline conditions. To represent conventional treatment processes, the water samples were then coagulated with aluminum sulfate prior to filtration to remove the oxidized manganese and iron formed from the addition of the potassium permanganate. Coagulated aliquots were filtered and collected to evaluate residual dissolved iron and manganese content. Based on the results of the jar tests it was determined that manganese was reduced by 95% or greater and that iron was completely removed to below the analytical detection limit (0.001 mg/L). It was determined that the potassium permanganate dose required for oxidation of iron was 0.94 mg/mg iron and for manganese was 1.92 mg/mg manganese. It was also observed that when the jars containing aliquots that turned brown in color after potassium permanganate dosing meant that iron and manganese were present and were being oxidized; however, water samples that turned pink were found to be over-dosed with potassium permanganate. The pink water is an undesired characteristic and could result in customer complaints when distributed to the system.The second component of research focused on NWTP existing conditions. Water samples were collected after each key unit operation within the NWTP and analyzed for iron and manganese. This was to determine if pre-chlorination at Fena Lake was effective at removing iron and manganese that could be present in the source water. Analysis was conducted where pre-chlorination at Fena Lake was practiced as well as when no pretreatment was practiced prior to the NWTP. It was determined that the iron and manganese were not detected downstream of the coagulation unit operation within the NWTP even when pre-chlorination was not practiced. Consequently pre-chlorination of Fena Lake source water was not required for controlling iron and manganese under the conditions experienced in this study.A third study was also implemented to confirm that 0.1-micron filters are appropriate for use in preparing samples for analytical determination of iron and manganese analysis at various points within the NWTP. The filtration step is important to delineate between dissolved and suspended iron and manganese forms. Standard Methods 3120B recommends the use of 0.45-micron filters, although based on literature it has been shown that oxidized manganese particles may be smaller than a 0.45-micron pore size. Unless a coagulant was used, the oxidized manganese may not be fully removed via the 0.45-micron filter. To verify the effectiveness of using a 0.1-micron filter, a jar test was conducted to compare the use of a 0.1-micron filter, a 0.45-micron filter, and a 0.45-micron filter after the sample has been coagulated. It was found that the use of a 0.1-micron filter was superior to the use of 0.45-micron filters even with coagulant addition when directly comparing between dissolved and suspended iron and manganese forms. It is recommended that 0.1-microns be utilized in lieu of historically recommended 0.45-micron filters for sample preparation procedures.
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Date Issued: 2014
Identifier: CFE0005180, ucf:50655
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005180

Title: INVESTIGATION OF THE EFFECT OF EDGE-OXIDIZED GRAPHENE OXIDE (EOGO) ON THE PROPERTIES OF CEMENT COMPOSITES.
Creator: Alharbi, Yousef, Nam, Boo Hyun, Chopra, Manoj, Zaurin, Ricardo, Kwok, Kawai, University of Central Florida
Abstract / Description: The use of edge-oxidized graphene oxide (EOGO), produced by a mechanochemical ?process that allow to deliver a product suitable for large-scale production at affordable cost, as ?an additive in cement composites was investigated. Comprehensive experimental tests were ?conducted to investigate the effect of EOGO on the properties of cement composites. The ?experimental tests were designed for three subtasks: (1) investigation of the performance of ?EOGO and its mixing method on the strength,...
Show moreThe use of edge-oxidized graphene oxide (EOGO), produced by a mechanochemical ?process that allow to deliver a product suitable for large-scale production at affordable cost, as ?an additive in cement composites was investigated. Comprehensive experimental tests were ?conducted to investigate the effect of EOGO on the properties of cement composites. The ?experimental tests were designed for three subtasks: (1) investigation of the performance of ?EOGO and its mixing method on the strength, pore structure and microstructure of EOGO-?cement composites, (2) evaluation of the rheological and fluidity behavior of EOGO-cement ?paste and mortar, and (3) investigation of the mechanism of the enhanced workability of ?EOGO-concrete. EOGO content ranged from 0.01% to 1% and two mix design methods were ?employed for cement paste and mortar to explore an optimum and feasible mix design of ?EOGO. Compressive and flexural strength tests were conducted to investigate the mechanical ?performance of EOGO-cement composites. Total porosity and water sorptivity were performed ?to investigate the pore structure of EOGO-cement paste and mortar. Furthermore, petrographic ?analyses were conducted to characterize the microstructure of EOGO-cement composites. ?Imaged based-mini-slump and flow table tests were performed to measure the fluidity of ?EOGO-cement paste and mortar. The rheological properties of EOGO-cement paste were ?measured through viscometer test. The mechanism of the enhanced workability of EOGO-?concrete was investigated by performing slump and water absorption of aggregate in cement ?paste tests. The key findings are (1) the addition of EOGO into cement composites improves the ?compressive and flexural strength, (2) 0.05% of EOGO is the optimum content to improve the ?strength and pore structure of EOGO-cement composites, (3) the addition of EOGO reduces the ?fluidity and increases the viscosity of EOGO-cement composites, (4) the addition of EOGO ?improves the workability of concrete, and (5) dry-mix design is feasible and more practical for ?large-scale production.?
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Date Issued: 2019
Identifier: CFE0007425, ucf:52721
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007425

Title: Cerium oxide nanoparticles act as a unique catalyst and scavenge nitric oxide and peroxynitrite and decrease RNS in vitro and in vivo.
Creator: Dowding, Janet, Self, William, Bossy-Wetzel, Ella, Zervos, Antonis, Seal, Sudipta, Santra, Swadeshmukul, University of Central Florida
Abstract / Description: Cerium oxide nanoparticles (CeO2 NPs)(nanoceria) have been shown to possess a substantial oxygen storage capacity via the interchangeable surface reduction and oxidation of cerium atoms, cycling between the Ce4+ and Ce3+ redox states. Reduction of Ce4+ to Ce3+ causes oxygen vacancies or defects on the surface of the crystalline lattice structure of the particles, generating a cage for redox reactions to occur. The study of the chemical and biological properties of CeO2 NPs has expanded...
Show moreCerium oxide nanoparticles (CeO2 NPs)(nanoceria) have been shown to possess a substantial oxygen storage capacity via the interchangeable surface reduction and oxidation of cerium atoms, cycling between the Ce4+ and Ce3+ redox states. Reduction of Ce4+ to Ce3+ causes oxygen vacancies or defects on the surface of the crystalline lattice structure of the particles, generating a cage for redox reactions to occur. The study of the chemical and biological properties of CeO2 NPs has expanded recently, and the methods used to synthesize these materials are also quite diverse. This has led to a plethora of studies describing various preparations of CeO2 NPs for potential use in both industry and for biomedical research. Our own work has centered on studies that measure the ability of water-based CeO2 NPs materials to reduce reactive oxygen and nitrogen species in biological systems, and correlating changes in surface chemistry and charge to the catalytic nature of the particles. The application in experimental and biomedical research of CeO2 NPs began with the discovery that water-based cerium oxide nanoparticles could act as superoxide dismutase mimetics followed by their ability to reduce hydrogen dioxide similar to catalase. While their ROS scavenging ability was well established, their ability to interact with specific RNS species, specifically nitric oxide (NO) or peroxynitrite (ONOO-) was not known. The studies described in this dissertation focus on the study of RNS and cerium oxide nanoparticles.Our in vitro work revealed that CeO2 NPs that have higher levels of reduced cerium sites (3+) at the surface (which are effective SOD mimetics) are also capable of accelerating the decay of peroxynitrite in vitro. In contrast, CeO2 NPs that have fewer reduced cerium sites at the particle surface (which also exhibit better catalase mimetic activity) have NO scavenging capabilities as well as some reactivity with peroxynitrite. Our studies and many others have shown cerium oxide nanoparticles can reduce ROS and RNS in cell culture or animal models. The accumulation of ROS and RNS is a common feature of many diseases including Alzheimer's disease (AD). Testing our CeO2 NPS in cortical neurons, we used addition of A? peptide as an AD model system. CeO2 NPs delayed A?-induced mitochondrial fragmentation and neuronal cell death. When mitochondrial ROS levels are increased, mitochondrial fission is activated by DRP1 S616 phosphorylation. Specifically, our studies showed the reduction of phosphorylated DRP1 S616 in the presence of CeO2 NPs. Results from our studies have begun to unravel the molecule mechanism behind the catalytic nature of how CeO2 NPs reduce ROS/RNS in biological systems and represents an important step forward to test the potential neuroprotective effects of CeO2 NPs in model systems of AD.A plethora of studies describing various preparations of CeO2 NPs for potential use in both industry and for biomedical research have been described in the past five years. It has become apparent that the outcomes of CeO2 NPs exposure can vary as much as the synthesis methods and cell types tested. In an effort to understand the disparity in reports describing the toxicity or protective effects of exposure to CeO2 NPs, we compared CeO2 NPs synthesized by three different methods; H2O2 (CNP1), NH4OH (CNP2) or hexamethylenetetramine (HMT-CNP1). Exposure to HMT-CNP1 led to reduced metabolic activity (MTT) at a 10-fold lower concentration than CNP1 or CNP2 and surprisingly, exposure to HMT-CNP1 led to substantial decreases in the ATP levels. Mechanistic studies revealed that HMT-CNP1 and CNP2 exhibited robust ATPase (phosphatase) activity, whereas CNP1 lacked ATPase activity. HMT-CNP1 were taken up into HUVECs far more efficiently than the other preparations of CeO2 NPs. Taken together, these results suggest the combination of increased uptake and ATPase activity of HMT-CNP1 may underlie the mechanism of the toxicity of this preparation of CeO2 NPs, and may suggest ATPase activity should be considered when synthesizing CeO2 NPs for use in biomedical applications. Overall the studies have uncovered two new catalytic activities for water-based CeO2 NPs (NO scavenging and accelerated decay of peroxynitrite), demonstrated their ability to reduce RNS in an AD cell culture model as well as identifying a catalytic activity (phosphatase) that may underlie the observed toxicity of CeO2 NPs reported in other studies.
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Date Issued: 2012
Identifier: CFE0004782, ucf:49783
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004782

Title: Investigation on the Mechanical, Microstructural, and Electrical Properties of Graphene Oxide-Cement Composite.
Creator: Al Muhit, Baig Abdullah, Nam, Boo Hyun, Zhai, Lei, Chopra, Manoj, University of Central Florida
Abstract / Description: Nanotechnology refers to the use of the materials or particles ranging from a few nanometers (nm) to 100 nanometers (nm) in a wide range of applications. Use of nanomaterials in cement composite to enhance the mechanical properties, fracture toughness and other functionalities has been studied for decades. In this regard, one of the carbon-based nanomaterials, Graphene Oxide (GO), has received attentions from researchers for its superior mechanical properties (e.g. tensile strength, yield...
Show moreNanotechnology refers to the use of the materials or particles ranging from a few nanometers (nm) to 100 nanometers (nm) in a wide range of applications. Use of nanomaterials in cement composite to enhance the mechanical properties, fracture toughness and other functionalities has been studied for decades. In this regard, one of the carbon-based nanomaterials, Graphene Oxide (GO), has received attentions from researchers for its superior mechanical properties (e.g. tensile strength, yield strength, and Young's modulus). Although GO is not lucrative in increasing electrical conductivity (EC) of cement paste compared to that of graphene- another derivative of GO, reduced graphene oxide (rGO), might be a solution to increase EC. Another derivative of GO is the solution to the problem.In this research, the compressive strength and flexural strength of GO-cement composite (GOCC) and rGO-cement composite (rGOCC) have been investigated with 0.01% and 0.05% GO and rGO content. GOCC-0.05% showed 27% increase in compressive strength compared to the control cement paste after 28 days (d) of hydration. GOCC-0.01% showed only 3.4% increase in compressive strength compared to the control. rGOCC-0.05% showed 21% increase in compressive strength and 15.5% increase in Modulus of Rupture (MOR) compared to the control cement paste after 28 d of hydration. On the other hand, rGOCC-0.01% showed 7% increase in compressive strength and 0.35% increase in MOR after 28 d. GOCC-0.05% showed increasing trends in compressive strength after 28 d indicating continuation of hydration. Similarly, rGOCC-0.05% also showed increasing trends in compressive and flexural strength after 28 d, possibly due to the reason described earlier.Microstructural investigation on GOCC-0.05% and GOCC-0.01% by X-ray Diffraction (XRD) illustrated that the crystallite sizes of tobermorite-9(&)#197; and jennite, which are mineralogical counterpart of disordered Calcium-Silicate-Hydrate (C-S-H), increases from 3 d to 28 d, representing the crystallite growth due to continued hydration. However, the crystallite size of GOCC-0.05% was smaller than that of GOCC-0.01% at both 3 d and 28 d, indicating finer nucleated grains. According to Hall-Petch equation, mechanical strength increases with decreasing particle size. Finer particles or grains can increase the strength in cement composites in several other ways: (1) GO acted as heterogeneous nucleation sites because of reactive functional groups. Activation energy was decreased by these (")defects(") in the cement paste, and consequently, numerous nuclei of C-S-H. with high surface area were formed, (2) because of finer grains, cracks are forced to move along a tortuous path, which makes the structure difficult to fail, and strength increased consequently (3) Finer grains of GOCC-0.05% created compacted hydration products decreasing porosity which can indirectly increase the strength. The above reasons, separately or in conjunction, might increase the strength of GOCC-0.05% and proved that GO is responsible for increasing heterogeneous nucleation sites during cement hydration.Early age hydration (EAH) characteristics were investigated for rGOCC specimens with 0.1% and 0.5% rGO content. Scanning Electron Microscope (SEM), Energy Dispersive X-ray analysis (EDX), and X-ray Diffraction (XRD) were employed to study the EAH characteristics. SEM/EDX, and XRD analysis were performed after 15 min, 1 h, 3 h and 24 h of hydration. (EAH) study on rGOCC-0.1% showed that at 15 m(&)#172;in hydration, numerous precipitates of, possibly, C-S-H formed along the grain boundary (GB) of unhydrated cement grains. This served as visual confirmation of Thomas and Scherer's Boundary Nucleation and Growth (BNG) model that hydration of cement grains was initiated by the short burst of nucleation of C-S-H embryos along GB. EDX on rGOCC-0.1% and rGOCC-0.5% showed that Ca/Si ratio in C-S-H was ~2.0. This finding indicated that C-S-H structure in this study was concurrent with that of impure jennite. XRD analysis also evidently showed that jennite was present, possibly possessing a short range ordered (SRO) structure, referring to local crystalline structure in a very short area. After consulting Chen's work, it would be appropriate to say that C-S-H found in this study resembled more as C-S-H (II), which is disordered jennite. It was also observed that as expected with cement with nanomaterials, with continuing hydration, pore spaces were filled with hydration products such as C-S-H, ettringite, CH, sulfoaluminates etc,.Lastly, Electrical resistivity (ER) testing on 9 sets of rGOCC specimens was conducted. The specimen includes 0.5%, 1%, 5% rGO content, and the control conditioned in both oven dry (OD) and saturated surface dry (SSD). ER increased with the increase of rGO content from 0.5% and 1% compared to that of the control. However, the ER of rGOCC-5% was significantly decreased, showing 93% reduction compared to the control, which can be interpreted as a threshold value for sensing applications to be explored. As expected, large reduction of ER value occurred on the specimens with the SSD condition. This reduction can be attributed to the ionic conduction though the pore solution of the composites. As the rGO content increased, so did the potential nucleation sites for hydration (as can be seen in SEM images), which might block the number of contact points among the rGO, resulting in low conduction and high resistivity. However, as rGO content increased to 5%, the contact areas/points increased to a degree that could trump the nucleation seeding sites, resulting in decreased ER. The ER measured with the rGOCC specimens was comparable to that of cement composites incorporating carbon fibers (CF), and steel fibers, but higher content of rGO are required to have a similar ER range of those fiber cement composites. This might be due to smaller sizes of rGO sheets and lower aspect ratio compared to other nanofibers causing drastic reduction of electron tunneling mechanism compared to other fibers.
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Date Issued: 2015
Identifier: CFE0005752, ucf:50107
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005752

graphene oxide (6)	+ -
oxidation (6)	+ -
graphene (5)	+ -
nanoparticles (5)	+ -
Modeling (4)	+ -

Nanoparticles (4)	+ -
cerium oxide nanoparticles (4)	+ -
Ceria (3)	+ -
Cerium Oxide (3)	+ -
Cerium oxide nanoparticles (3)	+ -
Ferrate (3)	+ -
Oxidation (3)	+ -
SOFC (3)	+ -
Solid Oxide Fuel Cells (3)	+ -
XRD (3)	+ -
catalysis (3)	+ -
cerium oxide (3)	+ -
chlorine dioxide (3)	+ -
iron (3)	+ -
potassium permanganate (3)	+ -
surface chemistry (3)	+ -
AFM (2)	+ -
Angiogenesis (2)	+ -
Catalysis (2)	+ -
Cerium Oxide Nanoparticles (2)	+ -
Cerium oxide (2)	+ -
Corrosion (2)	+ -
Disinfection by-products (2)	+ -
EXAFS (2)	+ -
Fuel Cells (2)	+ -

ETD Collection (83)	+ -
Honors Collection (7)	+ -

University of Central Florida (90)	+ -
Seal, Sudipta (15)	+ -
Zhai, Lei (13)	+ -
Heinrich, Helge (8)	+ -
Duranceau, Steven (7)	+ -

Orlovskaya, Nina (7)	+ -
Self, William (7)	+ -
Sundaram, Kalpathy (5)	+ -
Yuan, Jiann-Shiun (5)	+ -
An, Linan (4)	+ -
Blair, Richard (4)	+ -
Chopra, Manoj (4)	+ -
Lee, Woo Hyoung (4)	+ -
Raghavan, Seetha (4)	+ -
Schoenfeld, Winston (4)	+ -
Yestrebsky, Cherie (4)	+ -
Chow, Lee (3)	+ -
Clausen, Christian (3)	+ -
Das, Tuhin (3)	+ -
Gaume, Romain (3)	+ -
Kuebler, Stephen (3)	+ -
Kwok, Kawai (3)	+ -
Likamwa, Patrick (3)	+ -
Nam, Boo Hyun (3)	+ -
Parthasarathy, Sampath (3)	+ -
Randall, Andrew (3)	+ -
Reinhart, Debra (3)	+ -
Roldan Cuenya, Beatriz (3)	+ -
Sohn, Yongho (3)	+ -
Vaidyanathan, Raj (3)	+ -

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