Current Search: oxidative stress (x)
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- Title
- Molecular Mechanisms involved in inflammatory angiogenesis induced by monocyte chemotactic protein induced protein-1 (MCPIP1).
- Creator
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Roy, Arpita, Kolattukudy, Pappachan, Ebert, Steven, Parthasarathy, Sampath, Self, William, University of Central Florida
- Abstract / Description
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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.
Show less - Date Issued
- 2012
- Identifier
- CFE0004793, ucf:49760
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004793
- Title
- The Role of Mitochondrial Omi/HtrA2 Protease in Protein Quality Control and Mitophagy.
- Creator
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Ambivero, Camilla, Zervos, Antonis, Teter, Kenneth, Siddiqi, Shadab, Self, William, University of Central Florida
- Abstract / Description
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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.
Show less - Date Issued
- 2013
- Identifier
- CFE0004805, ucf:49752
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004805
- Title
- SELENOTRISULFIDE DERIVATIVE OF ALPHA-LIPOIC ACID: EVALUATION IN A CELL CULTURE MODEL FOR POTENTIAL USE AS A TOPICAL ANTIOXIDANT.
- Creator
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Alonis, Melenie, Self, William, University of Central Florida
- Abstract / Description
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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.
Show less - Date Issued
- 2005
- Identifier
- CFE0000663, ucf:46531
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000663
- Title
- Malondialdehyde (MDA) and Glutathione Peroxidase (GPx) are elevated in Crohns disease-associated with Mycobacterium avium subspecies paratuberculosis (MAP).
- Creator
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Qasem, Ahmad, Naser, Saleh, Masternak, Michal, Parthasarathy, Sampath, Andl, Claudia, University of Central Florida
- Abstract / Description
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Inflamed tissue in Crohn's disease (CD) are continuously producing toxic oxygen metabolites leading to cellular injury and apoptosis. Here, we are evaluating the role of Mycobacterium avium subspecies paratuberculosis (MAP) in oxidative stress in CD by evaluation of lipid peroxidation and antioxidant defense activity. Specifically, we measured malondialdehyde (MDA) level and selenium-dependent glutathione peroxidase (GPx) activity in the plasma from patients and cattle infected with MAP. The...
Show moreInflamed tissue in Crohn's disease (CD) are continuously producing toxic oxygen metabolites leading to cellular injury and apoptosis. Here, we are evaluating the role of Mycobacterium avium subspecies paratuberculosis (MAP) in oxidative stress in CD by evaluation of lipid peroxidation and antioxidant defense activity. Specifically, we measured malondialdehyde (MDA) level and selenium-dependent glutathione peroxidase (GPx) activity in the plasma from patients and cattle infected with MAP. The level of MAP antibodies in bovine sera was determined by IDEXX kit whereas detection of MAP DNA was performed by IS900-based nPCR. A total of 42 cattle (21 infected with MAP and 21 healthy controls), 27 CD subjects, 27 of CD-healthy relatives, 66 subjects with various diseases and 34 non-related healthy subjects were investigated. Overall, GPx activity was significantly higher in MAP infected humans (0.80941(&)#177;0.521) versus MAP (-ve) samples (0.42367(&)#177;0.229 units/ml), P(<)0.01. Similarly, the average of GPx activity in cattle infected with MAP was 1.59(&)#177;0.65 units/ml compared to 0.46907(&)#177;0.28 units/ml in healthy cattle (P(<)0.01). Although it was not statistically significant, MDA average level was higher in MAP infected human samples versus MAP (-ve) controls (1.11(&)#177;0.185 nmol/ml versus 0.805(&)#177;0.151 nmol/ml, respectively). Similarly, MDA average level in CD samples that are MAP+ (1.703(&)#177;0.231 nmol/ml) was higher than CD samples that are MAP (-ve) (1.429(&)#177;0.187 nmol/ml). In cattle, MDA average level in MAP infected samples was significantly higher at 3.818(&)#177;0.45 nmol/ml compared to 0.538(&)#177;0.18 nmol/ml in healthy cattle (P(<)0.01). Clearly, the data demonstrated that MAP infection is associated with oxidative stress and resulting in the pathophysiology of worsening of the condition of CD patients.
Show less - Date Issued
- 2016
- Identifier
- CFE0006699, ucf:51906
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006699
- Title
- CLASS-E CASCODE POWER AMPLIFIER ANALYSIS AND DESIGN FOR LONG TERM RELIABILITY.
- Creator
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Kutty, Karan, Yuan, Jiann-Shiun, University of Central Florida
- Abstract / Description
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This study investigated the Class-E power amplifier operating at 5.2 GHz. Since the operation of this amplifier applies a lot of stress on the switching transistor, a cascode topology was applied in order to reduce the drain-source voltage stress. Such an amplifier was designed and optimized in order to improve stability, power added efficiency, and matching. A layout for the said design was then created to be fabrication-ready using the TSMC 0.18 um technology. Post-layout simulations were...
Show moreThis study investigated the Class-E power amplifier operating at 5.2 GHz. Since the operation of this amplifier applies a lot of stress on the switching transistor, a cascode topology was applied in order to reduce the drain-source voltage stress. Such an amplifier was designed and optimized in order to improve stability, power added efficiency, and matching. A layout for the said design was then created to be fabrication-ready using the TSMC 0.18 um technology. Post-layout simulations were performed in order to realize a more realistic circuit performance with the layout design in mind. Long-term stress effects, such as oxide breakdown, on the key transistors were modeled and simulated in order to achieve an understanding of how leakage currents affect the overall circuit performance. Simulated results were compared and contrasted against theoretical understanding using derived equations. Recommendations for future advancements were made for modification and optimization of the circuit by the application of other stress reduction strategies, variation in the class-E topology, and improvement of the driver stage.
Show less - Date Issued
- 2010
- Identifier
- CFE0003360, ucf:48477
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003360
- Title
- Scandia and ceria stabilized zirconia based electrolytes and anodes for intermediate temperature solid oxide fuel cells: Manufacturing and properties.
- Creator
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Chen, Yan, Orlovskaya, Nina, An, Linan, Chen, Quanfang, Sohn, Yongho, Raghavan, Seetha, Huang, Xinyu, University of Central Florida
- Abstract / Description
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Scandia and ceria stabilized zirconia (10 mol% Sc2O3 (-) 1 mol% CeO2 (-) ZrO2, SCSZ) has superior ionic conductivity in the intermediate temperature range for the operation of solid oxide fuel cells, but it does not exhibit good phase stability in comparison with yttria stabilized zirconia (8 mol% Y2O3 (-) ZrO2, YSZ). To maintain high ionic conductivity and improve the stability of the electrolyte, layered structures with YSZ outer layers and SCSZ inner layers were designed, along with the...
Show moreScandia and ceria stabilized zirconia (10 mol% Sc2O3 (-) 1 mol% CeO2 (-) ZrO2, SCSZ) has superior ionic conductivity in the intermediate temperature range for the operation of solid oxide fuel cells, but it does not exhibit good phase stability in comparison with yttria stabilized zirconia (8 mol% Y2O3 (-) ZrO2, YSZ). To maintain high ionic conductivity and improve the stability of the electrolyte, layered structures with YSZ outer layers and SCSZ inner layers were designed, along with the referential electrolytes containing pure SCSZ or YSZ. The electrolytes were manufactured by tape casting, laminating, and pressureless sintering techniques. After sintering, while the thickness of YSZ outer layers remained constant at ~30 ?m, the thickness of inner layers of SCSZ for the 3-, 4- and 6-layer designs varied at ~30, ~60 and ~120 ?m, respectively. Selected characterizations were employed to study the structure, morphology, impurity content and the density of the electrolytes. Furthermore, in situ X-ray diffraction, neutron diffraction and Raman scattering were carried out to study the phase transition and lattice distortion during long-term annealing at 350 (&)deg;C and 275 (&)deg;C for SCSZ and YSZ, respectively, where the dynamic damping occurred when Young's modulus was measured.In YSZ/SCSZ electrolytes, thermal residual stresses and strains were generated due to the mismatch of coefficients of thermal expansion from each layer of different compositions. They could be adjusted by varying the thickness ratios of each layer in different designs of laminates. The theoretical residual stresses have been calculated for different thickness ratios. The effect of thermal residual stress on the biaxial flexural strength was studied in layered electrolytes. The biaxial flexure tests of electrolytes with various layered designs were performed using a ring-on-ring method at both room temperature and 800 (&)deg;C. The maximum principal stress during fracture indicated an increase of flexural strength in the electrolytes with layered structure at both temperatures in comparison with the electrolytes without compositional gradient. Such an increase of strength is the result of the existence of residual compressive stresses in the outer YSZ layer. In addition, Weibull statistics of the strength values were built for the layered electrolytes tested at room temperature, and the effect of thermal residual stresses on Weibull distribution was established. The calculation of residual stress present at the outer layers was verified. The high ionic conductivity was maintained with layered electrolyte designs in the intermediate temperature range. It was also established that the ionic conductivity of layered electrolytes exhibited 7% (-) 11% improvement at 800 (&)deg;C due to the stress/strain effects, and the largest improvements in a certain electrolyte was found to nearly coincide with the largest residual compressive strain in the outer YSZ layer.In addition to the study of layered electrolytes, mechanical properties of porous Ni/SCSZ cermet were studied. The anode materials were reduced by 65 wt% NiO (-) 35 wt% SCSZ (N65) and 50 wt% NiO (-) 50 wt% SCSZ (N50) porous ceramics in the forming gas. Young's modulus as well as strength and fracture toughness of non-reduced and reduced anodes has been measured, both at room and high temperatures. High temperature experiments were performed in the reducing environment of forming gas. It was shown that while at 700 (&)deg;C and 800 (&)deg;C the anode specimens exhibited purely brittle deformation, a brittle-to-ductile transition occurred at 800 (-) 900 (&)deg;C, and the anode deformed plastically at 900 (&)deg;C. Fractography of the anode specimens were studied to identify the fracture modes of the anodes tested at different temperatures.
Show less - Date Issued
- 2013
- Identifier
- CFE0005090, ucf:50750
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005090
- Title
- Design, Development, and Testing of a Miniature Fixture for Uniaxial Compression of Ceramics Coupled with In-Situ Raman Spectrometer.
- Creator
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Jordan, Ryan, Orlovskaya, Nina, Kwok, Kawai, Ghosh, Ranajay, University of Central Florida
- Abstract / Description
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This thesis is about the design, development and integration of an in-situ compression stage which interfaces through the Leica optical microscope coupled with a Renishaw InVia micro-Raman spectrometer. This combined compression stage and Raman system will enable structural characterization of ceramics and ceramic composites. The in-situ compression stage incorporates a 440C stainless steel structural components, 6061 aluminum frame, a NEMA 23 stepper motor. Two load screws that allow to...
Show moreThis thesis is about the design, development and integration of an in-situ compression stage which interfaces through the Leica optical microscope coupled with a Renishaw InVia micro-Raman spectrometer. This combined compression stage and Raman system will enable structural characterization of ceramics and ceramic composites. The in-situ compression stage incorporates a 440C stainless steel structural components, 6061 aluminum frame, a NEMA 23 stepper motor. Two load screws that allow to apply compressive loads up to 14,137 N, with negligible off axis loading, achieving target stresses of 500 MPa for samples of up to 6.00 mm in diameter. The system will be used in the future to study the structural changes in ceramics and ceramic composites, as well as to study thermal residual stress redistribution under applied compressive loads. A broad variety of Raman active ceramics, including the traditional structural ceramics 3mol%Y2O3-ZrO2, B4C, SiC, Si3N4, as well as exotic materials such as LaCoO3 and other perovskites will be studied using this system. Calibration of the systems load cell was performed in the configured state using MTS universal testing machines. To ensure residual stresses from mounting the load cell did not invalidate the original calibration, the in-situ compression stage was tested once attached to the Renishaw Raman spectrometer using LaCoO3 ceramic samples. The Raman shift of certain peaks in LaCoO3 was detected indicative of the effect of the applied compressive stress on the ceramics understudy.
Show less - Date Issued
- 2019
- Identifier
- CFE0007824, ucf:52809
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007824
- Title
- INVESTIGATION OF PS-PVD AND EB-PVD THERMAL BARRIER COATINGS OVER LIFETIME USING SYNCHROTRON X-RAY DIFFRACTION.
- Creator
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Northam, Matthew, Raghavan, Seetha, Ghosh, Ranajay, Vaidyanathan, Raj, University of Central Florida
- Abstract / Description
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Extreme operating temperatures within the turbine section of jet engines require sophisticated methods of cooling and material protection. Thermal barrier coatings (TBCs) achieve this through a ceramic coating applied to a substrate material (nickel-based superalloy). Electron-beam physical vapor deposition (EB-PVD) is the industry standard coating used on jet engines. By tailoring the microstructure of an emerging deposition method, Plasma-spray physical vapor deposition (PS-PVD), similar...
Show moreExtreme operating temperatures within the turbine section of jet engines require sophisticated methods of cooling and material protection. Thermal barrier coatings (TBCs) achieve this through a ceramic coating applied to a substrate material (nickel-based superalloy). Electron-beam physical vapor deposition (EB-PVD) is the industry standard coating used on jet engines. By tailoring the microstructure of an emerging deposition method, Plasma-spray physical vapor deposition (PS-PVD), similar microstructures to that of EB-PVD coatings can be fabricated, allowing the benefits of strain tolerance to be obtained while improving coating deposition times. This work investigates the strain through depth of uncycled and cycled samples using these coating techniques with synchrotron X-ray diffraction (XRD). In the TGO, room temperature XRD measurements indicated samples of both deposition methods showed similar in-plane compressive stresses after 300 and 600 thermal cycles. In-situ XRD measurements indicated similar high-temperature in-plane and out-of-plane stress in the TGO and no spallation after 600 thermal cycles for both coatings. Tensile in-plane residual stresses were found in the YSZ uncycled PS-PVD samples, similar to APS coatings. PS-PVD samples showed in most cases, higher compressive residual in-plane stress at the YSZ/TGO interface. These results provide valuable insight for optimizing the PS-PVD processing parameters to obtain strain compliance similar to that of EB-PVD. Additionally, external cooling methods used for thermal management in jet engine turbines were investigated. In this work, an additively manufactured lattice structure providing transpiration cooling holes is designed and residual strains are measured within an AM transpiration cooling sample using XRD. Strains within the lattice structure were found to have greater variation than that of the AM solid wall. These results provide valuable insight into the viability of implementing an AM lattice structure in turbine blades for the use of transpiration cooling.
Show less - Date Issued
- 2019
- Identifier
- CFE0007844, ucf:52830
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007844