856 matches in the database.
These are records: 1 - 30.
[1] [2] [3] [4] [5] … [29]
1.
Naber-Fisher, Glenellyn Mercedes Kae.
The Roles of Mentoring and Family Support in the Development of Asian Pacific American Female Leaders.
Degree: EdD, Leadership Studies, 2009, Bowling Green State University
► Research shows that there is a low number of Asian American women…
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▼ Research shows that there is a low number of Asian American women administrators in higher education institutions across the United States. The purpose of this life history study was to explore the lives of Asian Pacific American (APA) women in administration in predominately White public and private institutions of higher education in the Midwest. More specifically the study focused on the roles of mentoring and family support, and how they may have enhanced the professional lives of APA women.Five APA female middle level higher education administrators in the Midwest took part in the study. Data was collected from individual interviews with follow up questions and clarification via email. Data was then analyzed cross participants. Findings revealed that mentoring was a beneficial tool. The participants believed that their advancement in their careers was assisted by their mentors. Moreover, gender of the mentor did not make a difference in mentoring. Given the option to be mentored, these APA women were willing to take it. Findings also revealed that family was a support system for APAs. Family was found to be encouraging and supportive. Family (parents) not only emphasized education and hard work, but had high expectations. Themes which emerged from the data include political or civil rights involvement, enjoyment of living in the Midwest, the Asian American generation and mentoring. Recommendations for further research and leadership are also discussed.
Advisors/Committee Members: Pauken, Patrick.
Subjects: Education; Gender; Higher education
Keywords: Asian American; model minority; mentoring; leadership; higher education; adult development; life history; Asian culture
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2.
Nabiyouni, Maryam.
Mega-scale Bioinformatics Investigation of Codon Bias in Vertebrates.
Degree: MS, College of Medicine, 2011, University of Toledo Health Science Campus
► Although synonymous codon usage in mammals has been investigated for decades, there…
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▼ Although synonymous codon usage in mammals has been investigated for decades, there are still controversial interpretations of the observed results. Selectionism cannot explain the strong regularities in the codon bias, while neutralism is unable to comprehend the unusual high frequency of G or C nucleotides (~60%) in the third codon positions across all mammals. We performed a genome-wide computational analysis of synonymous codon usage with respect to local genomic GC-content, GC-content in the first and second codon positions, and overall genome length and GC-content. In this study, Codon Bias Index (CBI) is used to measure the codon bias in individual genes. The presented data is gathered from multiple available databases such as the Codon Usage Database, Animal Genome Size Database, BioGPS, and Exon/Intron Database. Our results suggest that local GC-content is a major contributor to the non-randomness of codon usage in mammals. Based on the obtained results, we propose a united hypothesis for the origin of GC-rich, GC-poor isochors and codon bias in mammals and vertebrates.
Advisors/Committee Members: Fedorov, Alexei.
Subjects: Bioinformatics; Biology; Biomedical Research
Keywords: Codon bias; GC composition; GC3; Vertebrates
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3.
Nachbauer, Cheryl Ann.
DISASTER RELIEF STRATEGY: Appropriating Abandoned Big Boxes.
Degree: M. Arch., Design, Architecture, Art and Planning : Architecture, 2009, University of Cincinnati
► “Give a man a safe home and you have housed his family…
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▼ “Give a man a safe home and you have housed his family – but train him how to build his own safe house and you have housed his family, and very probably his children’s families, and his relatives and friends.” - Ian DavisNatural disasters of any magnitude present an opportunity for adaptability and change. This thesis proposal will examine a disaster relief strategy that appropriates abandoned big boxes to provide immediate temporary, short term, and long term shelter. This thesis will focus on a hypothetical worst-case natural disaster scenario, to permit the proposed design to be easily scalable to handle disasters of any magnitude and apply to various global applications. The methodology includes a time frame of escorting the affected individuals through four disaster relief stages: removal, relocation, reconstruction and recovery. Cincinnati, Ohio, was chosen as the prototype for the disaster relief site due to the accessibility of abandoned big boxes, the lack of a permanent housing disaster plan, and the history of repeated flood damage resulting in numerous homeless individuals. Abandoned big boxes will be appropriated so that individuals will obtain immediate shelter where their basic needs will be met, so that the process of reconstruction and recovery can begin. Temporary and short-term residents will be housed until they can either return to their original dwelling or it has been appropriately repaired. Through the customization of prefabricated pods, aluminum framing systems, and structural insulated panels, long-term residents will participate in transforming the existing infrastructure of an abandoned big box into a personalized home that will evolve into a collective community.
Advisors/Committee Members: Williamson, Rebecca.
Subjects: Architecture
Keywords: Disaster Relief, Appropriation, Abandoned Big Box, Prefabrication, Kit-of Parts, Trauma Recovery, Community, Attachment
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4.
Nadas, Janos Istvan.
Computational Structure Activity Relationship Studies on the CD1d/Glycolipid/TCR Complex using AMBER and AUTODOCK.
Degree: PhD, Chemistry, 2009, Ohio State University
► The human immune system is very powerful and whose one function is…
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▼ The human immune system is very powerful and whose one function is to detect and eliminate foreign, pathogenic compounds that enter the body. The conventional major histocompatibility complexes (MHC) are able to bind peptides and present them to the T-cell lymphocytes thereby allowing the cell to communicate whether it is healthy or has been compromised. A different category of T-cell known as natural killer T (NKT) cells play an important role in bridging the innate and the adaptive immune systems, where NK cells and conventional T-cells exist, respectively. The innate immune response of these specific NKT cells has been associated with tumor rejection activities with the adaptive immune response being associated with protection against primarily bacterial infections, but also with viral and parasitic attacks.These NKT cells are also unique in that their T-cell receptor (TCR) proteins recognize foreign glycolipid antigens, not peptides, presented by MHC-I like Cluster of Differentiation 1 (CD1) molecules. The marine-sponge derived glycolipid α-galactosylceramide (α-GalCer) has so far been the most potent iNKT stimulatory ligand when presented by the CD1d protein. It is more than unusual that an α-glycolipid derived from a marine sponge could yield such a massive immune response in humans, since it is doubtful that humans have evolved with a defense mechanism against a possible invasion of marine sponges. Currently, the glycosphingolipids from the alpha-proteobacteria Sphingomonas are considered the natural foreign ligands for the system since they were found to activate iNKT cells but to a lesser degree than α-GalCer. The massive immune response cascade that follows after CD1d presentation of a glycolipid to iNKT cells has yielded a search for a better ligand with either comparable activity as α-GalCer but with less of its pharmaceutical hindrances or a ligand that can control the immune response. To date, superficial structure-activity relationships have been defined wherein modifications to either the sphingosine chain or acyl chain of the lipid can lead to a bias in the immune response, and modifications to the galactose sugar have led to null activity. Herein, this scientific project entailed the use of computational means to determine how the TCR protein of iNKT cells can differentiate so selectively between glycolipids presented by the CD1d protein in order to be able to design a better ligand for the system. Molecular dynamics simulations using AMBER found the crystallized CD1d/α-GalCer/TCR tertiary complex to be stable and relatively rigid in explicit solvent. A combination of high-level docking with AUTODOCK and simulation showed that modifications to the 2´- and 3´- positions of the galactose sugar are indeed not tolerated, whereas, modifications to the 4´- position were semi-tolerated. The simulations of CD1d/glycolipid binary complexes showed that glycolipids incapable of stimulating iNKT cells changed the direction of the CD1d residues that interact with TCR away from optimum orientation. Lastly, the evidence of a non-glycolipid ligand activating iNKT cells led to an undertaking of a virtual screening program to find a replacement for the galactose sugar yielding a library of viable aromatic-based lipid ligands.
Advisors/Committee Members: Wang, Peng.
Subjects: Biophysics; Chemistry; Immunology
Keywords: α-galactosylceramide; CD1d; TCR; computational; molecular dynamics; AMBER; AUTODOCK
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5.
Nadaud, Philippe S.
High-Resolution Structural Studies of Paramagnetic Proteins by Multidimensional Solid-State Nuclear Magnetic Resonance Spectroscopy.
Degree: PhD, Chemistry, 2010, Ohio State University
► Nuclear magnetic resonance (NMR) is one of the major spectroscopic techniques available…
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▼ Nuclear magnetic resonance (NMR) is one of the major spectroscopic techniques available for the characterization of molecular structure and conformational dynamics with atomic level detail. NMR relies on the intrinsic magnetic properties of certain nuclear isotopes, such as 1H, 13C, 15N, and 31P, which provide convenient, site-specific structural probes when placed inside a large external magnetic field. Recent developments in solid-state NMR (SSNMR) spectroscopy promise to enable detailed structural studies to be performed for important biological macromolecules, which are inherently insoluble but at the same time cannot be readily crystallized for analysis by X-ray diffraction. Prominent examples of systems of this type include large macromolecular complexes, membrane-bound peptides and proteins important in cell signaling, and fibrillar protein aggregates associated with the development of systemic and neurodegenerative human disorders, including Alzheimer’s and Parkinson’s diseases and type II diabetes. One of the main outstanding problems in biomolecular solid-state NMR spectroscopy, which impedes the widespread structural studies of proteins using this methodology, is related to the paucity of long range (i.e., greater than 5 A) structural restraints that can be determined by the currently available SSNMR techniques. This is primarily due to the fact that through space magnetic dipole-dipole interactions between 1H, 13C, 15N nuclei, which report on interatomic distances and thus protein structure, become vanishingly small for distances significantly in excess of ~5-6 A. The underlying fundamental concept of the new SSNMR methods described in this thesis is that, when introduced into normally diamagnetic proteins, unpaired electrons, which like certain nuclei are also magnetic particles, can couple very strongly through space to the neighboring nuclei. Indeed these electron-nucleus interactions are several orders of magnitudes larger than typical internuclear magnetic dipole-dipole couplings due to the large magnetic moment of the electron spin. One well-known physical phenomenon, which is a direct consequence of these large electron-nucleus interactions is the so-called nuclear paramagnetic relaxation enhancement (PRE). Importantly, the PRE phenomenon depends on the electron-nucleus separation in a well-defined manner and can extend to distances of up to ~15-20 A. The observation and quantification of long-range PRE phenomena in the solid phase has great potential for investigation of protein structures by SSNMR spectroscopy. However, no SSNMR study to date has experimentally demonstrated the systematic measurement of PRE effects in uniformly 13C,15N isotope labeled proteins. To address this we have designed a series of SSNMR experiments for the detection and quantification of nuclear PREs in model protein molecules intentionally modified with covalently-attached non-native sidechains containing various paramagnetic centers including nitroxide spin labels and transition metal ions. Most significantly, in the case of proteins containing Cu2+ ions, in the form of EDTA-chelates, we were able to demonstrate the quantitative measurements of electron-nucleus distances up to ~20 A. Both the quality and the information content of these PRE-based structural restraints suggest that they will become useful in future applications of SSNMR spectroscopy to the rapid refinement of three-dimensional protein folds.
Advisors/Committee Members: Jaroniec, Christopher.
Subjects: Chemistry
Keywords: NMR paramagnetic solid-state protein nuclear magnetic resonance spectroscopy
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6.
Nadauld, Taylor D.
Essays in Real Estate Finance.
Degree: PhD, Business Administration, 2009, Ohio State University
► The first essay in the dissertation analyzes the structure and attributes of…
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▼ The first essay in the dissertation analyzes the structure and attributes of subprime mortgage-backed securitization deals originated between 1997 and 2007. Our data set allows us to link loan-level data for over 6.7 million subprime loans to the securitization deals into which the loans were sold. We show that the securitization process, including the assignment of credit ratings, provided incentives for securitizing banks to purchase loans of poor credit quality in areas with high rates of house price appreciation. Increased demand from the secondary mortgage market for these types of loans appears to have facilitated easier credit in the primary mortgage market. To test this hypothesis, we identify an event which represents an external shock to the relative demand for subprime mortgages in the secondary market. We show that following the SEC’s adoption of rules reducing capital requirements on certain broker dealers in 2004, five large deal underwriters disproportionately increased their purchasing activity relative to competing underwriters in ZIP codes with the highest realized rates of house price appreciation but lower average credit quality. We show that these loans subsequently defaulted at marginally higher rates. Finally, using the event as an instrument, we demonstrate a causal link between the demand for mortgages in the secondary mortgage market and the supply of subprime credit in the primary mortgage market. The second dissertation essay examines the corporate governance of international real estate firms. With the passage of real estate investment trust (REIT) legislation in numerous countries around the world, more public and private real estate firms can choose between organizing themselves as a REIT, or a real estate operating company (REOC). REITs pay virtually all net income to shareholders in the form of dividends and are regulated in their investment policy, leverage, ownership, and operations to varying degrees. This paper considers the possibility that controlling shareholders of public real estate firms adopt REIT status as a credible commitment to increased levels of investor protection. Theory predicts that REITs are valued at a premium to otherwise similar REOCs, which I test using a sample of publicly traded real estate firms from 16 countries around the world. Surprisingly, I find that REITs are valued at a discount to REOCs. I briefly explore possible explanations for the result. Finally, I provide limited evidence consistent with an alternative hypothesis, which proposes that managers may be less likely to adopt REIT status if they have more valuable properties under management and a high level of inside ownership.
Advisors/Committee Members: Karolyi, Andrew.
Subjects: Finance
Keywords: Securitization; Subprime Mortgages; REITs; Corporate Governance
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8.
Nadella, Murali Vara Prasad.
Expression and regulation of parathyroid hormone-related protein during lymphocyte transformation and development of humoral hypercalcemia of malignancy in lymphoma.
Degree: PhD, Veterinary Biosciences, 2007, Ohio State University
► Although adult T-cell leukemia/lymphoma (ATLL) is caused due to infection with human…
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▼ Although adult T-cell leukemia/lymphoma (ATLL) is caused due to infection with human T-lymphotropic virus type-1 (HTLV-1), cellular events besides HTLV-1 infection are required for transformation of T-cells. HTLV-1 Tax plays an important role in the transformation of lymphocytes; however, the exact mechanisms remain unclear. Parathyroid hormone-related protein plays an important role in the pathogenesis of humoral hypercalcemia of malignancy observed in the majority of ATLL patients. PTHrP is also up-regulated in HTLV-1-carriers and normocalcemic ATLL patients. Using long-term co-culture assays, herein we reported that PTHrP and its receptor (PTH1R) were highly expressed during HTLV-1-mediated immortalization of lymphocytes. Co-transfection assays with HTLV-1 and PTHrP reporter plasmids showed that HTLV-1 mildly up-regulated PTHrP expression indicating that other cellular factors or events are required for increased expression of PTHrP in ATLL cells. The PTHrP gene is regulated by three promoter regions (P1, P2, and P3). We characterized an NF-êB binding site in the P2 promoter of human PTHrP and detected a specific complex in Tax-expressing human T-cells composed of p50/c-Rel, and two distinct complexes in ATLL cells consisting of p50/p50 homodimers and a second unidentified protein(s). Furthermore, we showed inhibition of NF-êB activity with Bay 11-7082 decreased PTHrP P2 promoter-initiated transcripts. Finally we developed a comparative xenograft model of canine T-cell lymphoma with hypercalcemia. Quantitative RT-PCR of T-cell lymphoma samples from hypercalcemic canine patients showed that PTHrP likely plays a central role in the pathogenesis of HHM and that hypercalcemia is the result of a combinatorial effect of different hypercalcemic factors. We monitored in vivo tumor progression and metastases in the mouse model by transducing the lymphoma cells with a lentiviral vector that encodes a luciferase-yellow fluorescent protein reporter and showed that in vivo trafficking patterns in this model were similar to that seen in dogs. These data demonstrated that 1) PTHrP and its receptor were markedly up-regulated during HTLV-1-mediated immortalization of lymphocytes 2) The PTHrP P2 promoter was regulated by NF-êB pathway in HTLV-1-infected and ATLL cells 3) Hypercalcemia in canine T-cell lymphoma patients was multifactorial and PTHrP plays an important role in the pathogenesis of HHM
Advisors/Committee Members: Rosol, Thomas J.
Subjects: Biology, Veterinary Science
Keywords: HTLV-1, ATLL, HHM, PTHrP, Canine lymphoma, Xenograft, Bioluminescent imaging
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9.
Nadella, Ramya.
Biosynthesis of Xyloglucan in Grasses and Identification of Endosperm Developmental Phases in Wheat Seeds.
Degree: MS, Plant Biology (Arts and Sciences), 2007, Ohio University
► Xyloglucans are the major hemicellulosic polysaccharides in the primary cell walls of…
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▼ Xyloglucans are the major hemicellulosic polysaccharides in the primary cell walls of dicots and non-graminaceous monocots but small amounts are also seen in the walls of grasses. They serve as cross-linkers of cellulose microfibrils and maintain the structural integrity of the cell.Xyloglucan biosynthesis mechanism is well understood and many biosynthetic genes have been identified in dicots. However this process is not known in grasses where structural differences in xyloglucan exist. Thus, this study aimed to investigate xyloglucan biosynthesis in grasses by functionally characterizing some xyloglucan biosynthetic genes, particularly the xylosyltransferases from wheat and rice. Wheat (TaGT34-7) and rice (OsGT34-3) homologs of Arabidopsis xyloglucan-xylosyltransferase (AtXT1) gene were previously identified using a bioinformatic script developed by Faik et al. (2006). The full-length cDNAs encoding TaGT34-7 and OsGT34-3 proteins were expressed in Pichia pastoris and Drosophila S2 expression systems, but the proteins did not show xylosyltransferase activity in Pichia pastoris and a low activity in Drosophila S2 cells. Further optimization is required to fully identify the function of these two proteins. In another study, the endosperm developmental phases were identified in developing wheat seeds using sectioning and light microscopy. Cell walls of wheat endosperm have ~70% (w/w) of arabinoxylan (AX), 20% (w/w) of mixed linked glucan (MLG), and only 5% (w/w) of cellulose. MLG and AX are deposited during cellularization and differentiation phases of the endosperm development, respectively. To identify the putative glycosyltransferase genes involved in the biosynthesis of these polymers (AX, MLG), it was necessary to first identify the endosperm developmental phases namely cellularization and differentiation phases at which they are deposited. Fresh wheat seeds were collected and their endosperm developmental phases were investigated using sectioning and light microscopy methods. Also, starch deposition was monitored using polarized light microscopy.
Advisors/Committee Members: Faik, Ahmed.
Subjects: Biology, Plant Physiology
Keywords: Xyloglucan; Grasses; Wheat; Rice
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12.
Nadian, Behrooz.
A unified tribological model for different regimes of lubrication and rub/impact phenomena in rotor dynamics.
Degree: PhD, Mechanical Engineering, 1995, Case Western Reserve University
► The research presented in this dissertation has produced an accurate unified tribological…
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▼ The research presented in this dissertation has produced an accurate unified tribological model to determine the fluid film and interacting forces between rotor and stator based on a realistic rough surface model. It also provides an overall solution strategy for calculation of forces for rotor-bearing interactions applied in the analysis of nonlinear rotordynamics problems. Surface roughness is generated computationally and, by using an average flow model, allows effects of surface roughness with different geometries on journal bearing performance to be analyzed. A mathematical model is developed for mixed lubrication and asperity contact in order to evaluate the asperity contacts loading, friction force, real contact area and fraction of journal bearing load capacity by asperity contact. A mathematical model for boundary lubrication in journal bearings has also been developed to determine the normal and traction contact forces. Stribeck type friction diagrams for different regimes of lubrication are computed and are in a good agreement with published experimental results. The rotor dynamics rub phenomena studied is based on a boundary lubrication model and shows routes to chaos. Surface parameter effects, such as roughness and hardness on rotor casing interacting forces are analyzed. By implementing the developed models for different regimes of lubrication in journal bearings, the transient dynamic analysis of a rotor in fluid film bearings has been studied based on realistically rough surfaces. Dynamical responses of the rotor in the presence of roughness indicates that a decrease of viscosity intensifies the influence of roughness in rotor trajectory and interacting forces. In the mixed lubrication region, short bearings are more influenced by surface roughness variation, compare to the long bearings. However, in the boundary lubrication region, all sizes of bearings are influenced by surface roughness variations
Advisors/Committee Members: Adams, M. L.
Subjects: Engineering, Mechanical
Keywords: Rotor dynamics, lubrication and rub/impact phenomena
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13.
NADIMPALLI, GAYATRI.
ESTIMATING LEAKS IN WATER DISTRIBUTION SYSTEMS BY SEQUENTIAL STATISTICAL ANALYSIS OF CONTINUOUS FLOW READINGS.
Degree: MS, Engineering : Environmental Engineering, 2003, University of Cincinnati
► Leakage in water distribution pipes is a major problem faced by the…
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▼ Leakage in water distribution pipes is a major problem faced by the water industry. Water utilities often employ traditional audit methods to estimate water lost as leakage. Many hydraulic models have also been developed in the recent past to estimate leakage rates and locate leaks. However, water audits give an approximate estimate of the leakage rates and the mathematical models can be applied under certain hydraulic conditions only. In this thesis, a new method is presented for detecting the magnitude of leaks in residential service zones of a drinking water distribution system. It is assumed that continuous measurements of flow rates through the main supply line into a residential service zone are available during periods of low use. The procedure involves computing the sample mean and variance from the set of measured flow rates as these flows are truncated progressively from below. Trajectories of the sample statistics and their derivatives are plotted versus the level of data truncation. In the presence of leaks, these trajectories diverge from their expected theoretical path when plotted on a standardized graph derived from a mixed truncated normal distribution. The point of departure on the standardized graph indicates where the truncation threshold matches the maximum rate of network leakage. A performance limit for the proposed method is derived to account for spatial constraints reflecting network size and time constraints arising from interval averaging. A simple example is presented first where the leakage is assumed to be of constant magnitude. The leak analysis is then extended to a more complicated case where pressure fluctuations in the distribution system add a statistical noise to the flow measurements. Results show that the method developed in this thesis estimates leakage rates quite accurately even in the presence of statistical noise. The method can be used to estimate leakage rates in branching mainlines or residential District Metering Areas (DMAs) where flows can be measured continuously for a sufficiently long period of time.
Advisors/Committee Members: Buchberger, Dr. Steven G.
Keywords: water distribution systems; leaks; mixed truncated normal distribution; district metering areas; stagnation probability
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14.
Nadkarni, Aditi A.
Functional analysis of the Rad51d (E233G) breast cancer associated polymorphism and a pharmacogenetic evaluation of RAD51D status.
Degree: PhD, College of Graduate Studies, 2008, University of Toledo Health Science Campus
► RAD51D performs functions in homologous recombination and telomere maintenance,two genome stabilization mechanisms.…
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▼ RAD51D performs functions in homologous recombination and telomere maintenance,two genome stabilization mechanisms. A gene variant in the human RAD51D gene that replaced glutamic acid (E) to glycine (G) at amino acid position 233 was identified as a low penetrance allele in high-risk familial breast cancer cases not associated with either BRCA1 or BRCA2 mutations. This dissertation describes the effects of this variant allele on RAD51D protein interactions and function. Surprisingly, the Rad51d (E233G) polymorphism increased cellular resistance to the DNA damaging agents, mitomycin C, cisplatin, UV light and methyl methane sulfonate as well as to the microtubule inhibitor taxol in mouse cells. Additionally, the Rad51d (E233G) variant reduced the anaphase bridge index, a telomere dysfunction correlate, and conferred increased cellular proliferation, suggesting that this variant may affect telomere function. Protein interaction, measured by yeast-2-hybrid analysis, demonstrated a two-fold decrease in interaction between RAD51C and RAD51D-E233G, while normal levels of interaction between XRCC2 and the variant were maintained. Molecular modeling suggested that the glutamic acid-233 forms a salt bridge with lysine-23 in the N-terminal domain of RAD51D, and the E233G substitution may disrupt an inter-domain interaction. This indicated that the breast cancer associated E233G amino acid change affected RAD51D protein interactions and function. The effect of this variant was further tested in three human breast cancer cell lines, BT- 20, T47D and MCF-7. Interestingly, Rad51d (E233G) conferred increased cisplatin resistance and cell growth in breast cancer cells with a mutant p53 (BT20 and T47D) but not with a functional p53 (MCF-7). Inhibition of p53 by pifithrin alpha treatment rescued this phenotype in the MCF-7 cell lines suggesting that the effect was p53-dependent. Additionally, Rad51d (E233G) conferred an increase in the cisplatin resistance selectively of the MCF-7 cells in which p53 expression was stably knocked down by siRNA, further supporting the p53-dependent effect of the variant. These studies indicate that the E233G variant affects RAD51D protein interactions and functions and confers p53-dependent cisplatin resistance in breast cancer cell lines. This study is the first to analyze the functional effects of a clinically relevant RAD51D amino acid substitution. Since RAD51D functions in at least two possible mechanisms of chemoprotection, HR and telomere protection further study of this variant will provide insight into which cellular mechanism involving RAD51D functions in cellular response to anticancer agents. Ellagic acid is a dietary polyphenol currently being investigated for its anticarcinogenic as well as chemoprotective effects. A study described in the Results section of this dissertation describes the effects of mammalian Rad51d-gene status on cellular response to ellagic acid. Selective cytotoxicity of ellagic acid towards Rad51d-deficient cells with an HR defect and chromosomal instability provides preliminary evidence of a potential anticancer effect of ellagic acid that involves HR repair. The findings detailed in this dissertation characterize a role for RAD51D in chemoresistance and propose the potential of this HR player as a molecular target for anticancer therapy.
Advisors/Committee Members: Pittman, Douglas.
Subjects: Genetics; Oncology; Pharmacology
Keywords: DNA Repair; DNA Damage; cancer; genomics; chemotherapy; pharmacogenetics
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15.
Nadkarni-DeAngelis, Radha Bhaskar.
Clinical Course of Children with a Depressive Spectrum Disorder and Transient Manic Symptoms.
Degree: PhD, Psychology, 2009, Ohio State University
► The present study (Multi-family Psychoeducation Group) provides 18-month longitudinal follow-up of children…
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▼ The present study (Multi-family Psychoeducation Group) provides 18-month longitudinal follow-up of children diagnosed with depressive spectrum disorder (DSD; major depressive disorder and/or dysthymic disorder) who present with clearly demarcated transient manic symptoms (TMS) of insufficient number or duration to be diagnosed with a bipolar spectrum disorder (BPSD; Bipolar-I, Bipolar-II, Cyclothymia, Bipolar-Not Otherwise Specified). Assessments were conducted at four time points, baseline (Time 1), 6 months (Time 2), 12 months (Time 3) and 18 months (Time 4). At Time 1 there were 115 participants in the BPSD group, 37 in the DSD + TMS group, and 13 in the DSD group. Due to sample attrition in the DSD + TMS and DSD groups, at Time 2 these two groups had 38 participants, at Time 3, 35 participants, and at Time 4, 33 participants. Measures that assessed socio-demographic variables, IQ (Kaufman Brief Intelligence Test), mood and co-morbid diagnoses (Children’s Interview for Psychiatric Syndromes – Child and Parent form [ChIPS/P-ChIPS]), clinical presentation (Mania Rating Scale, Children’s Depression Rating Scale – Revised, Children’s Global Assessment Scale, duration of prodromes), family environment (Coddington’s Life Events Scale, Expressed Emotion Adjective Checklist) and family history (Family History Research Diagnostic Criteria, Parental Mood Severity Index [calculated using Hamilton Rating Scale for Depression and Mania Rating Scale]) were collected at Time 1. I hypothesized that: 1) at Time 1, children with DSD + TMS will have lower C-GAS scores than children with DSD but higher scores than children with BPSD; 2) children with DSD + TMS at Time 1 will convert to BPSD at follow-up at a higher rate than children with DSD at Time 1; 3) conversion rates differed will not differ for DSD + TMS participants regardless of treatment status; 4) children with DSD + TMS at Time 1 who convert to BPSD at follow–up (converted group) will have greater impairment in clinical presentation, family environment and/or family history compared to children with DSD + TMS at Time 1 who do not convert (non-converted group). A secondary hypothesis was: the converted group will be more impaired on components of clinical presentation, family environment and/or family history than the non-converted group. Hypothesis 1, 3 and 4 were not supported. Hypothesis 2 was supported. The conversion rate from DSD + TMS to BPSD was 48% whereas the conversion rate from DSD to BPSD was 12.5% suggesting that TMS in a DSD population is a risk factor for conversion. This is particularly important, as pharmacologic treatments for children with depression and/or ADHD can destabilize children with bipolar disorder (Geller et al., 1992; Reichart & Nolen, 2004). Contrary to the hypothesis, for DSD + TMS participants, the one year wait-list control group (WLC) conversion rate was 60% whereas the immediate treatment group (IMM) conversion rate was 16% suggesting that psychosocial treatment may be beneficial. The secondary hypothesis was supported only for C-GAS scores. The converted group had lower C-GAS scores at Time 1 than the non-converted group. Clinical descriptions of converters and non-converters, limitations, clinical implication and future research ideas are discussed.
Advisors/Committee Members: Fristad, Mary.
Subjects: Psychology
Keywords: depression; mania; hypomania; irritability; children; conversion; bipolar disorder; depressive disorder; aggression; medication; dysthymia; major depressive disorder; risk factors; family history; family environment; clinical presentation; C-GAS; ADHD
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16.
Nadkarni, Suhita.
Dynamics of Dressed Neurons: Modeling the Neural-Glial Circuit and Exploring its Normal and Pathological Implications.
Degree: PhD, Physics (Arts and Sciences), 2005, Ohio University
► It is now established that glial cells are active partners to neurons…
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▼ It is now established that glial cells are active partners to neurons in the nervous system. Astrocytes, a subtype of glial cell, through characteristic calcium based excitability are able to integrate the activity of neurons and thereby modulate their normal function. Quantifiable coupling schemes were developed to incorporate the role of astrocytes in neuronal dynamics. The coupling mechanism between the two cells is dynamic, bidirectional and is based on experimental data. It takes place at two distinct time scales, with the calcium activity in astrocytes occurring in seconds while the electrical activity in neurons in milliseconds. Because of the extent of their influence on neuronal dynamics astrocytes can also be thought to play a crucial role in certain neurological disorders. Basic, yet physiologically relevant circuits were constructed to explore the consequences of aberrations in neuron astrocyte coupling. Our results suggest that stronger coupling between the two cells, which takes the form of upregulation of metabotropic glutamate receptors (mGluRs) by a factor of few tens in astrocytes in our model, makes the neuron hyperexcitable and leads to self sustained (seizure like) oscillations. This prediction is consistent with the experimental observation of 20-30 times more mGluRs seen on astrocytes of epileptic tissue. Further, inhibition by interneurons in the hippocampus is an essential mechanism. The complex dichotomy of excitation and inhibition defines the normal dynamics of the brain. The inhibitive action of interneurons is also thought to provide a vital first line of defense in pathological conditions like epilepsy. The effect of local inhibition on a hyperexcitable system with enhanced astrocytic coupling was examined and it was inferred that local inhibition is unlikely to remedy the hyperexcitable system. Under normal physiological conditions astrocytes are seen to strengthen spontaneous activity of neurons, a mechanism said to be involved in plasticity and learning. Our model is able to quantitatively mimic this pattern of marked increase of spontaneous activity due to the astrocyte. Synaptic transmission is the central pathway through which information processing is carried out. The role of astrocytes in potentiating synaptic transmission was studied. The simulations carried out are a pointer to astrocytes, as playing a role in enhancing signal transmission.
Advisors/Committee Members: Jung, Peter.
Subjects: Biophysics, Medical
Keywords: Astrocyte Neuron Interaction; Modeling Neural Glial Circuits; Astrocytes; Neurons; Metabotropic Glutamate Receptors
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17.
Nadler, Laurie Sue.
GABA(A) receptor subunit expression and assembly in rat cerebellar neurons.
Degree: PhD, Pharmacology, 1996, Case Western Reserve University
► The GABAA receptor mediates the action of γ-aminobutyric acid, the major inhibitory…
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▼ The GABAA receptor mediates the action of γ-aminobutyric acid, the major inhibitory neurotransmitter in the CNS. Multiple receptor subtypes, with distinct subunit compositions, exist in the brain. While 16 different receptor subunits have been identified by molecular cloning, the α1, β2/3, and γ2 subunits are thought to form a major GABAA receptor population. To understand how GABAA receptors are assembled and how their expression is regulated, we analyzed the α1, β2/3, and γ2 subunit polypeptides in the cerebellum and in cultured cerebellar granule neurons. The expression of GABAA receptor subunit polypeptides was examined using subunit-specific antibodies. In the cerebellum, β2/3 and γ2 polypeptide expression increased several-fold during the second and third postnatal weeks. Moreover, levels of the β2/3 and γ2 polypeptides increased between 2 and 6 days in cultured cerebellar granule neurons. These patterns were very similar to those previously determined for their encoding mRNAs. However, expression of the α1 subunit was more complex. Two α1-related polypeptide species of Mr 39 kDa and 51 kDa d isplayed reciprocal temporal profiles in cultured granule neurons, despite no significant change in the α1 mRNA level. Additional findings demonstrated that the 39 kDa polypeptide is also present in vivo and suggested that it is a novel form of the α1 subunit which contains a shortened N-terminal domain. These studies suggest that GABAA receptor subunit expression is regulated in part at the level of the mRNA, although α1 subunit expression may also be regulated at the level of receptor assembly. The relationship between subunit polypeptide expression and that of GABAA receptor complexes was assessed in radioligand binding assays. These studies showed that levels of receptor complexes increase in parallel with the 51 kDa α1, β2/3, and γ2 subunits both in vivo and in culture. Moreover, immunoprecipitation studies suggested the physical association of these subunits in one type of receptor oligomer. However, pharmacological experiments demonstrated the presence of multiple GABAA receptor subtypes in cultured granule neurons. Taken together, this work provides a first step towards the elucidation of GABAA receptor composition and assembly in identified neurons
Advisors/Committee Members: Siegel, Ruth E.
Subjects: Biology, Neuroscience
Keywords: Cerebellum; Neurons; Receptors, GABA-A
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18.
Nadolnyak, Denis Alexandrovic Jr.
Three essays on the economics of agricultural biotechnology.
Degree: PhD, Agricultural, Environmental and Development Economics, 2003, Ohio State University
► This dissertation consists of three essays on the economics of agricultural biotechnology.…
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▼ This dissertation consists of three essays on the economics of agricultural biotechnology. In the first essay, “A Model of Diffusion of Genetically Modified Crop Technology in Concentrated Agricultural Processing Markets - The Case of Soybeans”, a dynamic model of diffusion of a genetically modified crop technology is developed and simulated. The model accounts for factors specific to agricultural markets, such as oligopsony power of crop processors, grower characteristics, and identity preservation requirements. It is found that market power of crop processors decreases the equilibrium adoption levels and prolongs the diffusion period. Producer uncertainty and perception of the risks associated with planting GM crops increases equilibrium adoption levels but lengthens the diffusion period, and producer heterogeneity with respect to new crop profitability may have different effects on the diffusion process. The second essay is called “Valuation of International Patent Rights for Agricultural Biotechnology”. In it, the choices that biotechnology companies make about marketing different genetically modified (GM) crops in different countries with highly uncertain returns are modeled as a real option problem of the entry decision solved at a micro-level by individual firms. A computational solution to the model produces distributions of entry probabilities that are determined by different market and regulatory environments. These proportions are compared to the actual data on incidences of biotech firms entering foreign markets with different GM crops, and conclusions about the distribution of patent values, returns evolution, and efficiency of local IPR protection are drawn. In the third essay, “Patent Policy Analysis for the Case of Agricultural Biotechnological Innovations”, certain peculiarities of the process of development of agricultural biotechnological innovations are considered, in particular the distinction between an RandD race for an event discovery and subsequent competition for developing the discovery’s marketable applications. A formal model is specified and analyzed with regard to how different patent protection policies affect firms’ RandD strategies and social surplus from innovations. It is found that inclusive scope patent protection encourages more RandD and faster innovation diffusion than additional scope protection, which is superior to length protection.
Advisors/Committee Members: Sheldon, Ian M.
Keywords: GM crops; Patent; Soybeans; scope protection
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19.
Nadour, Alaa M.
MBG - Induced EMT.
Degree: MS, College of Graduate Studies, 2007, University of Toledo Health Science Campus
► Interest and research in Epithelial-mesenchymal transition are currently growing at a high…
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▼ Interest and research in Epithelial-mesenchymal transition are currently growing at a high level due the importance of this process in embryogenesis, organ development, tumor progression, and several pathologic conditions in adult tissues. Epithelial to mesenchymal transformation (EMT) is now believed to play a major role in the pathogenesis of renal interstitial fibrosis, and organ fibrosis in general. This unique event along with other several cellular pathways, leads to excessive accumulation and deposition of extracelular matrix components that cause fibrous scars and destruction of kidney parenchyma, with consequent end-stage renal failure.Multiple intracellular signaling pathways are implicated in the regulation of this complicated event. Marinobufagenin (MBG), a cardiotonic steroid, and an inhibitor of the enzymatic activity of Na/K-ATPase, has shown a potency to activate multiple signaling pathways that ultimately leads to EMT in renal epithelial cells. Therefore, it was reasonable to hypothesize that elevated levels of this cardiotonic steroid could be a potent inducer of EMT. Our study on the porcine proximal epithelial cell line demonstrates that Marinobufagenin induces EMT in time and concentration dependent fashion.
Advisors/Committee Members: Shapiro, Joseph.
Subjects: Biology, Molecular
Keywords: MBG; EMT; TGF-β; Epithelial; Mesenchymal; cells; LEF-1
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20.
Nadsady, Kenneth Allan.
A two-stage method for system identification from time series.
Degree: MS, Electrical Engineering (Engineering), 1998, Ohio University
A two-stage method for system identification from time series.
Advisors/Committee Members: Irwin, R. Dennis.
Keywords: Hankel Matrix Singular Values; two-stage system identification technique; Eigenvalue Realization Algorithm
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21.
Naelitz, Samantha L.
Girls just want to have fun: Connecting girls in grades six through eight with reading materials they want to read.
Degree: MEd, Reading, 2008, Bowling Green State University
► The purpose of this study was to find out what reading materials…
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▼ The purpose of this study was to find out what reading materials girls in grades six, seven, and eight were interested in reading. It is essential that educators work to connect students with materials they want to read to foster motivation and positive attitudes towards reading. To do so, educators must understand exactly what types of materials students are interested in reading. Specific categories were established including: types of reading material, types of books, genres, themes, last three books read for fun, favorite books, and books students would like to read in the future. A survey was developed in order to answer these questions. The survey was administered to students from four different schools across grades six, seven, and eight. A total of 151 female students participated in the study. The results of the study indicated that female students in grades six, seven, and eight are interested in reading a wide variety of topics. The results were listed by category in terms of frequency. The questions that required participants to respond with specific titles and authors were listed in order of frequency as well. Several specific titles and authors were repeated among students. The repeated titles were then categorized by types of book, genres, and themes. Participants seemed to be interested in a variety of materials such as magazines, books, fiction, novels, mystery, fantasy, and materials regarding friendship, love, and adventure. The titles provided indicate students are reading fiction, novels, realistic fiction, biography, fantasy, science fiction, historical fiction, horror, and materials regarding friendship, growing up, family, courage, and relationships. This study suggests that educators find reading materials that interest students in order to connect students with reading materials they want to read.
Advisors/Committee Members: Hendricks, Cindy.
Subjects: Education
Keywords: Reading: grade six; grade seven; grade eight; middle school girls; junior high girls
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22.
Naenna, Praphun.
Numerical and Analytical Studies of the Electromagnetic Bias in Satellite Altimetry.
Degree: PhD, Electrical and Computer Engineering, 2011, Ohio State University
► The electromagnetic (EM) bias is an important error term in sea surface…
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▼ The electromagnetic (EM) bias is an important error term in sea surface height estimation from satellite radar altimetry. Although numerous theoretical studies of the EM bias have been performed in the past, most are based on low-order hydrodynamic and electromagnetic models that impact the results obtained. This dissertation attempts to improve understanding of the underlying physical mechanism of the EM bias through both numerical and analytical approaches, so that EM bias correction algorithms for satellite missions can be improved. The first part of the dissertation employs a Monte Carlo procedure with numerical nonlinear hydrodynamic simulations coupled with numerical physical optics methods for electromagnetic scattering from the sea surface to produce a deterministic set of sea surface profiles and the corresponding altimeter pulse returns. This numerical approach allows studies of the impact of various physical effects on the EM bias including long wave and short wave effects. Results have shown that short sea waves can play an important role for the EM bias; these effects are not fully captured by previous low-order EM bias theories. The second part of the dissertation involves the development of an improved analytical model of the EM bias in order to capture and explain effects obtained previously in the numerical Monte Carlo study. The analytical model utilizes the same formulation as used in the computation of pulse returns in the previous Monte Carlo simulation and has a final form that involves an integral containing the correlation and reduced bicorrelation functions of the sea surface. The surface reduced bicorrelation functions due to the effects of nonlinear long waves and modulated short waves are derived from the weakly nonlinear theory of Longuet-Higgins and the hydrodynamic modulation transfer function respectively. It can be shown that, in the geometrical-optics limit, the developed analytical model yields previous models of altimeter pulse return and EM bias when appropriate. Comparisons of the results obtained analytically to the empirical EM bias model for Jason-2 satellite mission show reasonable agreement. Effects of sea swell and shallow water depth are also considered.
Advisors/Committee Members: Johnson, Joel T.
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23.
Nafday, Omkar A.
FILM FORMATION AND CO2 CORROSION IN THE PRESENCE OF ACETIC ACID.
Degree: MS, Chemical Engineering (Engineering), 2004, Ohio University
► The role of acetic acid (HAc) on the protectiveness of iron carbonate…
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▼ The role of acetic acid (HAc) on the protectiveness of iron carbonate (FeCO 3 ) films in CO 2 corrosion has been investigated using electrochemical, scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. HAc has recently been recognized as a major factor in premature pipeline failure causing either generalized or localized corrosion. The main cause of concern is the undissociated (free) HAc which is found in oilfield brines. The pH value of the brine determines both the amount of free HAc and the supersaturation (SS). In order for a protective FeCO 3 film to form, the SS value is critical. A series of experiments was performed to test the effect of various amounts of free HAc on cylindrical X-65 steel coupons at different values of pH at stagnant (no rotation) conditions. A 3% sodium chloride (NaCl) salt solution by weight was used to simulate oilfield brine. All experiments were conducted at fixed pH, 80°C to accelerate film formation. In order to ascertain that a FeCO 3 film was indeed formed, a XRD scan was conducted on the film observed on the sample at the end of experiment and the matching of constituent element peaks confirmed a FeCO 3 film. HAc was found to have no effect on film formation and on the final corrosion rates of X-65 mild steel. The SEM pictures show no effect of HAc on film formation and protectiveness at a fixed pH. No evidence of localised corrosion (pitting) was observed on the specimens.
Advisors/Committee Members: Nesic, Srdjan.
Subjects: Engineering, Chemical
Keywords: Film formation and CO 2 Corrosion in the Presence of Acetic Acid
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24.
Nafziger, Fern M.
Route through Concrete: Employing cultural appropriation to restructure America's strip malls.
Degree: M. Arch., Design, Architecture, Art and Planning : Architecture (Master of), 2010, University of Cincinnati
► This thesis focuses on human appropriation into a transitioning retail structure of…
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▼ This thesis focuses on human appropriation into a transitioning retail structure of the American suburban neighborhoods. There is a current phenomenon of immigrants settling into suburban environments, and at the same time closely carrying their cultural heritage. How can the individual change their environment to fit their own needs and desires while only being one part of a larger whole? By studying the differing perceptions of political, social and physical boundaries these small business owners will methodically implement a way to break the confines of the encasement of a strip mall. How these businesses grow and expand, diminish and contract, can influence how the building is restructured through time. By exploring the everyday, a method of implementing changes will be developed to continually alter the structure of the strip mall to better serve both the entrepreneur and the neighborhood. The intention of this thesis is to reveal a method by which retailers of all cultures can express their identity through how they appropriate space within specified boundaries. To accomplish this, it will be necessary to explore means by which to express this difference in culture to the ‘outside’ to allow people to be more socially accepting and aware. These two objectives will in turn have a positive residual effect on the suburban community by improving the now declining conditions of the suburbs as well as empowering ethnic entrepreneurs to open and grow in their business ventures.
Advisors/Committee Members: Williamson, Rebecca.
Subjects: Architecture
Keywords: strip mall; culture; appropraition
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25.
Nafziger, Jonathan W.
A Novel Cache Migration Scheme in Network-on-Chip Devices.
Degree: MS, Engineering and Applied Science: Computer Engineering, 2010, University of Cincinnati
► Future Network-on-Chip (NoC) designs no longer map single cores to each cache…
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▼ Future Network-on-Chip (NoC) designs no longer map single cores to each cache slice but rather multiple cores in layouts known as hybrid architectures. Additional proposals have suggested creating reconfigurable hybrid architectures where the OS can revise core-to-cache mappings as required. However, these designs will still be measured by their ability to reduce the average L2 cache delay. Denser core placements with varying core mappings require cache policies with intelligent data placement schemes otherwise there will be no gain to overall system performance as a result of the networked architecture. Solutions such as OS-directed page placement can reduce some of this delay by placing pages in caches local to the initial requestor. However, due to the page-level allocation granularity compared to line-level data accesses, this policy can still result in shared data existing in remote locations during highly parallelized applications. The most effective network delay reduction alternative is line-level data migration. Data migration policies are designed to take advantage of data temporal locality by assuming data recently used by a processor will be used again in the future. Several variations of migration policies have been proposed to address this demand. However, the physical costs, high computation demands and poor scalability of these methods have reduced their effectiveness in future layouts with hundreds of cores. Additionally, many proposals fail to consider migrating data to a centralized location with even latencies for multiple active cores instead they reduce latency for a single core at the expense of all others. This best average placement is also known as the nearest-neighbor search or the “Two-Dimensional Post Office Problem”. The proposed Directional Migration solution attempts to solve these problems by providing an autonomous, line-level migration that is responsive to multiple cores with varying access patterns. This design maintains two usage sensors in the form of physical counters on a per-cache-line basis. Migrations traverse only a single network hop to reduce in-transit delays, providing finely-tuned movement and responsiveness to changes in future access patterns. This migration policy is further enhanced by the addition of the Active Neighbor Migration policy. This method is a unique implementation which proposes consideration of data spatial locality. Here each triggered migration causes analysis of logically neighboring lines for potential early migrators. The Directional Migration solution with the Active Neighbor Migration policy provides a solution to the nearest-neighbor search with a constant physical cost in relation to the number of cores and size of the network while maintaining a linear physical cost in relation to the size of the cache. This is of enormous importance as the size of networks and volume of cores on a single device grow. The physical cost is also independent of the number of shared or migratory lines as the volume of such continues to grow exponentially due to highly parallelized applications. Finally, this solution provides an adaptive response to changes in network layout and core density as necessitated by any NoC architectures.
Advisors/Committee Members: Vemuri, Ranganadha.
Subjects: Electrical engineering
Keywords: Network-on-chip; NoC; Cache; Data Migration; Spatial Locality; Temporal Locality
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26.
Nafziger, Kathryn M.
Particulate Nature of Matter, Self-Efficacy, and Pedagogical Content Knowledge: Case Studies in Inquiry.
Degree: MS, Chemistry, 2008, Miami University
► In many classrooms, elementary teachers focus their efforts on literacy and frequently…
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▼ In many classrooms, elementary teachers focus their efforts on literacy and frequently marginalize science instruction. In order to increase time spent teaching science, a local school district initiated a program that coupled literacy with standards-based, inquiry science instruction. Utilizing a qualitative, case study approach, this research explored how teaching physical science through inquiry affected teachers' knowledge of the particulate nature of matter, self-efficacy, and pedagogical content knowledge. The results of the inquiry revealed that a sound understanding of good inquiry practices did not always translate to practice, that teaching through inquiry with prior knowledge of the particulate nature of matter can uncover gaps in this knowledge, and that self-efficacy was only influenced by the teachers' knowledge of the particulate nature of matter if the teacher understood the connections between this knowledge and their teaching practice.
Advisors/Committee Members: Lowery Bretz, Stacey.
Subjects: Chemistry
Keywords: particulate nature of matter; self-efficacy; pedagogical content knowledge; elementary education
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27.
Nagabhushan, Sahana.
Neural Mechanisms Underlying Stress-Induced Depression and Its Prevention.
Degree: BS, College of Arts and Sciences / Department of Biological Sciences, 2011, Kent State University Honors College
► Psychological and physical stressors stimulate the noradrenergic system which results in the…
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▼ Psychological and physical stressors stimulate the noradrenergic system which results in the induction of cytokine production via norepinephrine acting on β-adrenergic receptors. These cytokines, especially IL-1β, and the dysregulation of the noradrenergic system are implicated in depressive behavior. Current antidepressants increase norepinephrine in the brain which often leads to worsening of depressive symptoms during early stages of treatment. Blocking the effects of norepinephrine, with a β-adrenergic receptor blocker like Propranolol, may prevent stress-induced depression.
Advisors/Committee Members: Johnson, John.
Subjects: Behavioral Sciences
Keywords: depression, stress, norepinephrine, b-adrenergic receptors, propranolol, interleukin-1
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28.
Nagalingam, Dakshinamurthy Sharma.
OXIDATION RESISTANT COATINGS ON MICROCELLUAR CARBON FOAM USING SIMPLE SCALABLE TECHNIQUES.
Degree: MS, Materials Science and Engineering, 2007, Wright State University
► Carbon foam has many applications in the fields of thermal management, net-shape…
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▼ Carbon foam has many applications in the fields of thermal management, net-shape composites and electronic cooling due to its porous structure, low density, electrical and thermal conductivities. However it is prone to oxidation at high temperatures in air. Whereas some previous studies have reported oxidation protective coatings on other carbon structures such as graphite parts and fibers, there is very limited work on foam. Moreover, earlier methods have used vapor phase techniques such as Plasma Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD). There is no known study involving such coatings using simple scalable liquid phase method. This thesis reports our results on such coatings obtained on carbon foam. Boron Nitride was chosen as the coating material. Several solvents and processes were investigated. Finally a two step process using PVP binder in alcohol-based solution is found to be most effective. Unlike other available methods this technique does not involve toxic precursors or by-products. This method is simple and can be obtained at atmospheric pressure. Different coating combinations using various particle sizes were applied and their surface morphologies were studied using SEM (Scanning Electron Microscopy) and FESEM (Field Emission Scanning Electron Spectroscopy). It was observed that coating formed using 1µ BN followed by 0.7µ size BN particles has the best performance so far. The surface chemistry of this coating was studied using X-ray Photo Spectroscopy (XPS) and found to be that of pure BN after heat treatment. This coating was tested on several grades of aerospace foams having different porosities and cell sizes. The testing shows that this layer enhances the oxidation resistance of all foams to a certain extent. However it is most effective on the foams that have ridged ligaments compared to those having smooth ligaments. On carbon foams having high surface roughness this layer could suppress oxidation even at 800 C and enhance the survivability by 333%. This coating approach therefore shows promise as a scalable, environmentally friendly way of inhibiting oxidation in porous carbon structures.
Advisors/Committee Members: Mukhopadhyay, Sharmila M.
Subjects: Engineering, Materials Science
Keywords: Carbon Foam, Coatings
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29.
Naganathan, A.
Hot Stamping of Manganese Boron Steel(Technology Review and Preliminary Finite Element Simulations).
Degree: MS, Mechanical Engineering, 2010, Ohio State University
► The simulation of hot stamping is rather complex and challenging, and requires…
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▼ The simulation of hot stamping is rather complex and challenging, and requires information about properties of die and sheet materials, heat transfer, and friction between the deforming material and the dies. A large number of researchers use different commercial codes , such as LS-Dyna, Pamstamp, Autoform, and DEFORM to conduct hot stamping simulations with various levels of success. In this study DEFORM, a commercial code widely used for the analysis of hot, cold and warm forging operations and die design has been used. This code can consider elastic and plastic deformations of the sheet material, friction, heat transfer and elastic deflections of the dies. Two part geometries have been analyzed, using information provided in the literature as well as that obtained from various companies that produce hot stamped parts. The results indicate that it is possible to predict the deformation and temperatures in the part and in the dies by considering the variation of interface heat transfer in function of interface pressure. Using this approach it is also possible to optimize the design of cooling channels in the dies. It appears that the approach, used in this study, is quite promising for use in industrial environment to optimize die and process design for hot stamping.
Advisors/Committee Members: Altan, Taylan.
Subjects: Mechanical Engineering
Keywords: Hot Stamping,22MnB5
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30.
Nagapattinam Ramamurthi, Ragavendar.
Dynamic Trace-based Analysis of Vectorization Potential of Programs.
Degree: MS, Computer Science and Engineering, 2012, Ohio State University
► Most modern processes, ranging from high performance desktop processors to power efficient…
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▼ Most modern processes, ranging from high performance desktop processors to power efficient mobile processors comes equipped with a SIMD vector unit. Further, with upcoming processors and GPUs the length of the vector registers continue to widen. Exploiting the vector units is no longer an option for programs aiming for high performance and efficiency. A lot of existing code bases are not written to exploit vectorization. Although modern compilers have good auto-vectorizers, static analysis is inherently limiting and does not uncover full vectorization potential of programs. Therefore a tool which identifies vectorization potential of existing programs is very useful. In this thesis, we describe an approach to identify vectorization potential of programs by analyzing the dynamic data dependency graph built using the execution trace of the program. By observing the runtime dependencies of the program and allowing any dependency preserving reordering, we uncover vectorization opportunities missed by compile time analyses. The description of the implementation details of the vectorization analysis tool is provided and then, vectorization metrics for a few benchmarks are measured and presented.
Advisors/Committee Members: Ponnuswamy, Dr. Sadayappan.
Subjects: Computer Science
Keywords: Performance analysis; dynamic analysis; vectorization
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