ETD Center Search

▼ In this thesis we address the problem of mining association rules from databases containing quantitative attributes. Values of many quantitative attributes are distributed as strong concentrations in a few narrow regions across a very wide complete range of possible values. Intervals of equal width for such domains are not meaningful and may miss out on many peculiarities of data. Our methodology consists of a two phase approach. The first phase determines the boundaries around most meaningful intervals of the value range. We seek to maximize the information content of the choice of the selected initial interval boundaries. The second phase executes the association rule mining algorithm which uses these interval boundaries and modifies them, if needed, to determine rules with specified support and confidence levels. The set of generated rules is then examined to keep only the most specific versions by deleting their more general versions from the set. We have run tests with this algorithm using a network traffic database and the results obtained are presented in the thesis. We also contrast the benefits of this approach with the one in which we may start with uniform width, fixed size, intervals for a quantitative attribute. Advisors/Committee Members: Bhatnagar, Raj.

▼ Bounded Model Checking (BMC) is a formal method of verifying Very Large Scale Integrated (VLSI) circuits. It shows violation of a given circuit property by finding a counter-example to the property along bounded state paths of the circuit. The BMC problem is inherently NP-complete and is traditionally formulated to a boolean SATisfiability (SAT) problem, which is subsequently solved by a SAT solver. Automatic Test Pattern Generation (ATPG), as an alternative to SAT, has already been shown an effective solution to NP-complete problems in many computer-aided design areas. In the field of BMC, ATPG has already achieved promising results for simple properties; its effectiveness for more complicated nested properties, however, remains unknown. This thesis presents the first systematic framework of ATPG-based BMC capable of checking properties in all nested forms on gate level. The negation counterpart to a property is mapped into a structural monitor, which is tailored to a flattened model of the input circuit. A target fault is then injected at the monitor output, and a modified ATPG-based state justification algorithm is used to search a test for this fault. Finding such a test corresponds to formally establishing the property. The framework can easily incorporate any existing ATPG tool with little modification. The proposed framework has been implemented in a computer program called FORMAL, and has been used to check a comprehensive set of properties of GL85 microprocessor and USB 2.0 circuits. Experimental results show that the ATPG-based approach performs better in both capacity and efficiency than the SAT-based techniques, especially for large bounds and for properties that require large search space. Therefore, ATPG-based BMC has been demonstrated an effective supplement to SAT-based BMC in VLSI circuit verification. Advisors/Committee Members: Saab, Daniel G.

▼ The APC tumor suppressor is a multifunctional protein involved in cell migration, proliferation, differentiation and apoptosis. It is a component of the Wnt signaling pathway and is best known for its ability to down-regulate beta-catenin and consequent effects on transcriptional regulation. Previous work in our laboratory has demonstrated that APC accelerates apoptosis-associated caspase activity independently of transcription, suggesting novel tumor suppressor functions of APC. In the present study, the transcription-independent mechanisms of APC function in apoptosis were investigated. We mapped the APC apoptosis-accelerating region to amino acids 1-760 by testing a series of non-overlapping APC segments. Interestingly, this segment corresponds to a stable group II caspase cleavage product of APC released during apoptosis that includes the amino-terminal amino acids 1-777. Mutation of the APC aspartic acid residue at position 777 in APC to an alanine completely abolished in vitro cleavage of APC by a recombinant group II caspase. This mutation also rendered the full length protein unable to accelerate apoptosis in vitro. A truncated APC protein associated with familial and sporadic colorectal cancer, and unable to accelerate apoptosis in vitro and in vivo, is resistant to group II caspase cleavage. These results demonstrate that cleavage of APC and the subsequent release of an amino-terminal segment are necessary for the transcription-independent mechanism of APC-mediated apoptosis. Additionally, we have elucidated the mechanism of APC-mediated apoptosis by identifying and characterizing a downstream partner of APC in this apoptotic cascade. hTid-1, a homologue of the Drosophila tumor suppressor Tid 56, is an apoptosis modulator predominantly located in mitochondria. We have demonstrated that the amino-terminal segment of APC (APC 1-777) interacts with hTid-1 directly using co-immunoprecipitation, pull-down assays, and immunofluorescence. Immunofluorescence studies and subcellular fractionation show that the APC amino-terminus, exogenous and endogenous, which is released by caspase cleavage during apoptosis, is translocated to the mitochondria. Finally, over-expression of hTid1 partially rescues the HCT116 cells from apoptosis mediated by APC in the absence and presence of exogenous apoptosis stimuli. These data suggest that the amino-terminal segment of APC promotes cell sensitivity to apoptosis through physical and functional interactions with the apoptosis modulator hTid-1. Advisors/Committee Members: Groden, Joanna.

▼ This study evaluated the effects of using IntelliFill IV Robot system on IV admixture operations at the Division of Pharmacy, Cincinnati Children’s Hospital Medical Center (CCHMC), Cincinnati, Ohio. A before (without IntelliFill) and after (with IntelliFill) study design was applied. One-minute fixed-interval work sampling technique was used in the evaluation. Return of investment (ROI) analysis also was conducted in determining the break-even point. The data analyses include Chi-square test, frequency analysis, and time unit analysis. Total observations of pharmacy staff on IV admixture operations before and after using IntelliFill IV Robot system were 18,228 minutes and 17,231 minutes, respectively. There was a daily time spent saved of 0.42 FTE for pharmacy staff after using the IntelliFill system. The break-even point for using this IntelliFill IV Robot system was a daily workload of 489 syringes for automated IV admixture. IntelliFill IV Robot system could reduce labor utilization on IV admixture operations. Advisors/Committee Members: Lin, Dr. Alex.

▼ Retroviruses are RNA viruses that replicate through a DNA intermediate, the provirus. Provirus gene expression is dependent on the host machinery. The interplay between the virus and host post-transcriptional armamentarium is complex and the interface with the small RNA pathway has not been characterized. Retroviruses including human immunodeficiency virus type 1 (HIV-1) have evolved multiple strategies to utilize host machinery to execute intricate control of viral gene expression. As introduced in Chapter One of this dissertation, a prominent theme is that viral cis-acting RNA elements interact with cellular RNA binding proteins to modulate balanced viral post-transcriptional expression and sustain virus replication. The work in this dissertation characterized host protein interaction with a post-transcriptional control element (PCE) identified in the 5’ untranslated region (UTR) of at least eight retroviruses that facilitates efficient synthesis of retroviruses structural proteins. In addition, these studies also characterized virus-host interaction presented by the host small RNA pathway, which poses an innate cellular defense against infectious agents and retrotransposons. A growing literature shows that virus-encoded small RNAs and host encoded small RNAs play fundamental roles in animal virus replication. Another focus of the research herein was the characterization of the interaction of HIV-1 with the host small RNA pathway. The results revealed that virus-encoded RNA silencing suppressor activity modulates the activity of host-encoded microRNAs that can attenuate viral translation. Results of Chapter Two demonstrated for the first-time that RNA helicase A (RHA) is the cellular effector protein that operates the PCE/RNA switch. RNA mobility shift assays and RNA co-immunoprecipitation assays revealed that RHA specifically recognizes features of the redundant stem-loop structure of the PCE; the PCE/RHA interaction occurs in both the nucleus and the cytoplasm and is necessary for PCE activity. Downregulation of RHA abolishes PCE activity independently of a change in PCE mRNA stability or its cytoplasmic accumulation. Sucrose gradient analysis showed that RHA facilitates polysome accumulation of PCE-containing retroviral RNA and the cellular junD transcript. JunD is an AP-1 transcription factor and this transcript represents the first example of a cellular PCE/RHA interaction that is necessary for efficient translation. In summary, our results revealed a previously unidentified role for RHA in retrovirus and host cell translation that implicates RHA as an integrative effector of gene expression involved in the continuum of gene expression from transcription to translation. Chapter Three characterizes interplay between the host small RNA pathway and HIV-1. Experiments in plant and animal cell systems demonstrate that HIV-1 Tat regulatory protein exerts RNA silencing suppressor (RSS) activity across the plant and animal kingdoms. HIV-1 Tat and plant virus P19 RSS function similarly to suppress RNA silencing downstream of small RNA maturation. The effect of the host small RNA pathway was characterized by downregulation of the key enzyme of host microRNA biogenesis (Dicer), P19 expression, or by mutation in the conserved double-stranded RNA-binding domain of the Tat RSS. The outcome of the small RNA pathway on HIV-1 replication is attenuation of viral translation. The reversal of HIV-1 translation repression by plant RSS supports the recent finding in Arabidopsis that plant miRNAs operate by inhibition of translation. An implication of our study is that the host small RNA pathway plays a strategic role in the viral accumulation in a newly HIV-1-infected patient. Chapter Four describes results from microRNA microarrays and functional assays that assess the interface between the host small RNA pathway the HIV-1 accessory proteins Vpr and Vif. Profiles of host microRNAs were compared between cells infected with HIV-1 or a strain deficient in vpr/vif. The outcome of this work is a microRNA microarray database that stands a resource to develop testable hypotheses about the role of microRNAs in HIV-1 biology. Protein analysis demonstrated that Vpr/Vif modulates the activity of two miRNAs that downregulate a cellular transcriptional cofactor of Tat. The results of RNA and protein analysis provide an explanation for upregulation of HIV-1 transcription during HIV-1-induced cell cycle arrest. We conclude that modulation of microRNA activity by Vpr and Vif contributes to the positive selection for conservation of vpr in HIV-1 quasispecies in infected patients. In Chapter Five, changes in microRNA profile were evaluated upon infection of human lymphocytes with an HIV-1 strain deficient in Tat RSS activity. Comparative analyses with HIV-1 infection demonstrated that a collection of host microRNAs are modulated by HIV-1 Tat RSS activity and indicated a generalized rather than selective effect of Tat RSS activity on host small RNA activity. Results of ribosomal profile analysis of HIV-1 transfected 293 cells determined that HIV-1 gag RNA accumulates in high molecular weight complexes that co-sediment with puromycin resistant pseudo-polysomes. Pseudo-polysomes are known sites of translational repression by microRNA. The gag transcripts redistribute to polyribosomes upon expression of viral RSS. These results document that the interface between HIV-1 and the host small RNA pathway modulates viral protein synthesis. Perspectives on the experimental results and ideas for future directions are presented in Chapter Six. In conclusion, the work in this dissertation comprehensively characterized specific viral RNA interactions with host protein RNA helicase A and the interaction of HIV-1 regulatory and accessory genes with the host small RNA pathway. Each of these interactions is important for balanced translational control of the retrovirus. Advisors/Committee Members: Boris-Lawrie, Kathleen.

▼ Two homologous series of potentially mesomorphic monomers, 4,4′-bis(n-(acryloyloxy)alkyloxy) biphenyl (BnA) and 2,6-bis(n-(acryloyloxy)alkyloxy) naphthyl (NnA) were synthesized. Researches in three different areas were conducted based on above monomers: i. The first three chapters concern about topochemically controlled polymerization of BnA in mesophases. Generally two liquid crystalline phases were observed for BnA homologues, S B and S E. All the BnA-S E phases assume a tilted bilayer structure and have well defined 3-dimensional (solid-like) structures. Long range order exists in the smectic layer normal direction as well as in the lateral direction. The third chapter describes the photopolymerization of monomer B5A. Polymers (PB5A's) with different liquid crystalline structures were obtained. When B5A was cured in the S E phase, a quasi-topochemical reaction was involved and the resulting polymer was also in a S E phase. Two smectic B phases (PB5A-S B α and β phases) with different molecular arrangements were obtained when B5A was cured in the S B phase. When B5A was cured in the isotropic state, only a nematic LC structure was obtained. The molecular organization within th e monomer dictates the resulting polymer structure. ii. The fourth chapter examines the spacer concept in side chain liquid crystal polymers. The mesophase formation is thought to be realized due to the decoupling of the motions of the isotropic backbone and the anisotropic mesogenic side chain by the use of a flexible spacer group. In this study, a detailed investigation of the effect of spacer length on the structural ordering of side-chain LC polymers was carried out based on two homologous series of polymeric systems, PBnA and PNnA. It was found that as n increases, the decoupling of motions between the backbone and side-chain mesogenic group increases, and consequently, the LC order within the polymeric system increases. iii. Finally, in the fifth chapter, an attempt was made to estimate the glass transition of polymethylene. We employed a group contribution approach to the problem, i.e. extrapolation of the transition temperature of two homologous series of polymers (PBnA and PNnA) with increasing methylene group content. The monomers were photopolymerized in the isotropic state so that amorphous polymethylene was obtained. (Abstract shortened by UMI. Advisors/Committee Members: Litt, Morton H.

▼ The purpose of this study is to develop a communication model of employee cynicism toward organizational change. The few studies on employee cynicism were mainly conducted in the fields of management and psychology. The role of communication in shaping employee cynicism was rarely highlighted. Using the theoretical framework of social information processing (SIP), this study explored the communication variables in the social context which contribute to employee cynicism toward organizational change in a higher education institution. In the model, the three variables reflecting the social context, specifically, perceived quality of information, cynicism of colleagues, trust in the administration, are hypothesized to predict change-specific cynicism, which in turn, leads to intention to resist change. Participation in decision making (PDM) is hypothesized to predict intention to resist change both directly and indirectly through the mediating role of change-specific cynicism.The research was conducted in a Midwestern university which was undergoing a comprehensive strategic planning process. An online survey was administered to all full time tenure track faculty in this university. Path analysis was used to test the overall model fit. The findings of the study suggest that the proposed model explained a significant amount of variance in the outcome variables. However, contrary to the theoretical assumptions, PDM did not have significant causal effects on the outcome variables. Based on the empirical data, the proposed model was revised. The revised model fit the empirical data under study and all path coefficients were statistically significant at the .05 level. The revised model suggests that perceived quality of information had the largest causal effect on change-specific cynicism, followed by cynicism of colleagues, and finally trust in administration. Change-specific cynicism explained 79% of the variance in intention to resist change.The results of the study support SIP theory by indicating that change-specific cynicism emerges from the work environment. Future studies are called for to explore cynicism from the communication perspective. Further, more research should be conducted to investigate employee cynicism in the changing higher education environment. This study has significant practical implications for administrators in higher education institutions. Advisors/Committee Members: Daniels, Tom D.

▼ Marek's disease virus (MDV) causes malignant T cell lymphoma in chickens and is the major pathogen in poultry industry. The viral gene meq is abundantly expressed in MDV-transformed cell lines and MDV tumor samples. It contains a basic leucine-zipper region highly homologous to those of jun and fos, and a C-terminal proline-rich region including two and one-half repeat sequence (PRRs). In this report, we demonstrate that the proline-rich domain in the C-terminus of Meq is able to transactivate transcription when fused to the Ga14 DNA-binding domain, with the last 33 amino acids being essential for this activity. Full activity also requires at least one PRR, although fusion of itself alone with the DNA-binding domain represses transcription. Meq is able to dimerize with C-Jun and activate meq transcription through an AP-1-like motif in the meq promoter. The optimal binding sites of Meq/C-Jun and Meq/Meq are determined. Meq/C-Jun heterodimers bind a consensus with a core TRE/CRE site PuPuTGAC(G)TCAT. Meq homodimers bind two groups of DNA sequences. Group I site has a consensus GAGTGATGAC(G)TCATC, group II PuACACACAPy. By methylation interference assays and mutagenesis analysis, crucial nucleotides for the binding are identified. By computer simulation and circular pe rmutation assays, we further suggest that group II binding sites are intrinsically bent, and the DNA bending is necessary for the recognition by Meq/Meq. These results provide crucial information in the search of the functional targets of Meq, and shed new light on the general mechanism of DNA recognition by bZIP proteins Advisors/Committee Members: Kung, Hsing-Jien.

▼ The Veterans’ Glass City Skyway (VGCS) is a long span cable stayed bridge that carries I-280 over the Maumee River in Northwestern Ohio. Composed of 8,800 feet of precast, post-tensioned segmental box girders, the VGCS features a 1,225 feet cable stay span with a single plane of stays and was designed by FIGG Bridge Engineers, Inc. The Ohio Department of Transportation (ODOT) contracted the University Research Team (URT) composed of faculty and students from the University of Toledo and the University of Cincinnati to instrument the main span of the VGCS throughout construction and early service life. 128 vibrating wire strain gages were installed in eight segments at four cross sections to monitor the long-term behavior of this bridge. Data from these gages has been collected since the casting date of each segment. In this thesis, an overview of the long term strains and stresses was completed. The focus was on behavior during construction. Strain time histories were organized and compared to the construction time line. Approximate experimental stresses were derived from the strain data. The experimental stresses were compared to the stresses calculated by the contractor. The strain time histories were consistent with the construction logs and the experimental stresses were consistent with the analytical stresses. Overall, it was shown that the strain monitoring system was functioning properly and provided an accurate reflection of the actual strains on the VGCS. Advisors/Committee Members: Nims, Douglas.

▼ In modern microprocessors, more memory hierarchy and larger caches are integrated on chip to bridge the performance gap between high-speed CPU core and low speed memory. Large set-associative L2 caches draw a lot of power, generate a large amount of heat, and reduce the overall yield of the chip. As a result, large power consumption of the cache memory system has become a new bottleneck for many microprocessors. In this research, we analyze the performance of a location cache which works with a low power L2 cache system implemented by the drowsy cache technique. A small direct-mapped location cache is added to the traditional L2 cache system. It caches the way location information for the L2 cache access. With this way location information, the L2 cache can be accessed as direct-mapped cache to save both dynamic and leakage power consumption. Detailed mathematical analysis of the location cache power saving rate is presented in this work. To evaluate the power consumption of the location cache system on real world workloads, both SPEC CPU2000 and SPEC CPU2006 benchmark applications are simulated with the reference input set. Simulation results demonstrate that the location cache system can save a significant amount of power for all benchmark applications in L1 write through policy, and save power for benchmark applications with high L1 miss rate in L1 write back policy. Advisors/Committee Members: Jone, Dr. Wen-Ben.

▼ Coxeter groups arise in many parts of mathematics as groups generated by reflections. They provide an important source of examples in geometric group theory, where "virtual" properties of infinite groups, that is, properties of subgroups of finite index, are of strong interest. This dissertation focuses on virtual properties of infinite Coxeter groups. The following results are proved: (1) The intersection of a collection of parabolic subgroups of a Coxeter group is a parabolic subgroup; (2) The center of any finite index subgroup of an irreducible, infinite, non-affine Coxeter group is trivial; (3) Any finite index subgroup of an irreducible, infinite, non-affine Coxeter group cannot be expressed as a product of two nontrivial subgroups. Then, a unique decomposition theorem for subgroups of finite index in a Coxeter group without spherical or affine factors is proved based on (2) and (3). It is also proved that the orbit of each element other than the identity under the conjugation action in an irreducible, infinite, non-affine Coxeter group is an infinite set, which implies that an irreducible, infinite Coxeter group is affine if and only if it contains an abelian subgroup of finite index. Besides these, new proofs are given for the statement that the center of an irreducible, infinite Coxeter group is trivial, and a stronger version of this statement. Advisors/Committee Members: Davis, Michael.

▼ Linda Markowitz (2000) expanded the concept of a successful union campaign from beyond merely recognition to include post campaign solidarity. While making strides in the study of labor, Markowitz ignores what many others have missed as well, the changing labor market has segregated workers in the same industry across numerous buildings and cities, thus increasing the challenges unions face in building solidarity among members. This, combined with a demographically diverse workforce, and the cleavages that may result, makes union organizing ever more difficult. Even when a union is successful in obtaining recognition, long term solidarity may be at risk if specific demographic groups have unique concerns. This is particularly problematic if local tensions are ignored during the initial organizing drives. To assess these issues, I examine one union campaign spread across two major cities. Through focusing on the two primary locations of a wide spread janitors’ campaign, it becomes apparent that while an important victory was won, union organizers were unaware of concerns that arose from the unique demographics of the city. Specific factors that may influence solidarity after a successful campaign in relation to local demographics allows for a better understanding of the larger movement. Advisors/Committee Members: Martin, Andrew.

▼ The folate receptor (FR) type Beta, which is expressed in about 70% of acute myelogenous leukemia (AML) and can be selectively up-regulated by all-trans retinoic acid (ATRA), is a promising target for therapeutic intervention in AML. Using KG-1 and MV4-11 AML cells and recombinant 293 cells, we show that the histone deacetylase (HDAC) inhibitors Trichostatin A (TSA), valproic acid (VPA) and FK228 potentiate ATRA induction of FR-Beta. ATRA and/or TSA did not induce de novo FR synthesis in any of a variety of FR-negative cell lines tested. These results indicate that the combination of ATRA and innocuous HDAC inhibitors may be expected to facilitate selective FR-Beta-targeted therapies in AML. Mechanistic studies showed that (1) TSA did not alter the effect of ATRA on the expression of retinoic acid receptors (RARs) Alpha, Beta or Gamma, (2) ATRA increased the association of RAR Alpha with the basal FR-Beta promoter; (3) the enhancement of the ATRA effect by TSA was associated with increased acetylation of the core histones H3 and H4 at or near the basal FR-Beta promoter, (4) TSA caused a striking ATRA-dependent increase in Sp1 binding at the promoter without a further change in the association of RAR Alpha or an increase in Sp1 expression; (5) TSA further decreased the availability of putative repressor AP-1 protein(s). We further demonstrate that FR-Beta selectively mediated cell growth inhibition by the (6S) diastereoisomer of dideaza tetrahydrofolate in a manner that was potentiated by ATRA and HDAC inhibition. This study also found that ATRA induced apoptosis in MV4-11 cells but increased FR-Beta expression in the surviving cells. These surviving cells resistant to ATRA induced apoptosis can mimic the residual cells refractory to ATRA differentiation therapy. Thus this cell line can serve as a model cell line to establish FR-Beta-targeted therapy for minimal residual disease in APL. Sublines of MV4-11 cells that have uniform cell populations were isolated. Preliminary data showed that ATRA treatment increased the expression of FR-Beta in the cells collected from NOD/SCID mouse bone marrow engrafted with two such sublines demonstrating the feasibility of using this approach to develop novel FR-Beta-targeted-therapies for minimal residual disease in APL. Advisors/Committee Members: Ratnam, Ph.D., Manohar.

▼ The first two projects describe new applications of flow injection capillary electrophoresis (CE). The first study focuses on the determination of lactate or oxalate using injected lactate oxidase (LO) and peroxidase with UV detection. Two reactions, catalyzed by (LO) and peroxidase, are initiated by a single injection of the enzymes and the substrate 2,2’-azino-bis(3-ethylene-thiazoline-6-sulfonic acid) (ABTS) into the capillary previously filled with the sample (lactate or lactate-oxalate mixture) and the running buffer containing NADH. The oxidized ABTS product upon reaction with NADH is converted to NAD+, which is detected at 266 nm with a sample throughput of 7 min including wash steps. Linearity for lactate is established from 0.0025 – 1mM and serum samples are analyzed with an average recovery of 101%. This method can also be applied to the determination of oxalate as an inhibitor of LO. The second topic describes the determination of the concentration of cardiolipin using CE with on-line N-nonylacridine orange (NAO) dye interaction and spectrophotometric detection at 497 nm. Other phospholipids do not interfere and a detection limit of 0.05 ìM was found. In a blind study, actual mitochondrial cell membrane samples in the µL range, taken from cells before or after UV light exposure, are analyzed using the CE method. The last two topics describe preconcentration of pharmaceuticals and phospholipids with nano-electrospray ionization mass spectrometry (nano-ESI MS). An analytical method is developed for the quantitative determination of dicyclomine in serum with cyclopentolate as the internal standard by off-line nano-ESI MS with reversed phase mini-solid phase extraction (mini-SPE). Different length (0.5cm, 1cm) reversed phase (C4 and C18) mini-SPE cartridges are prepared by packing gel-loader pipette tips for optimization of the preconcentration effect. A factor of 100 is possible using the 1 cm C18 or C4 cartridge. Spiked serum samples are quantitatively determined using the C18 cartridge. Preconcentration of phospholipids is first studied for nano-ESI MS by weak anion exchange SPE. With aminopropyl SPE, detection limits are lowered 2-2000 times for different phospholipids as compared to no SPE. With aminopropyl mini-SPE and mixed mode C18/aminopropyl (1:1) mini-SPE, the detection limits for eight different phospholipids are lowered another factor of 5 better (about 0.05 to 5 pmol/ìL) than those for weak anion exchange SPE. Linear calibration curves are able to be established. Advisors/Committee Members: Danielson, Neil D.

▼ This work combines the use of biochemical and structural modeling approaches to characterize the FHA domains from human Chk2 and Caenorhabditis elegans Chk2 proteins. The DNA damage checkpoint pathway is vital to the maintenance of genomic integrity. Chk2 plays key roles on this pathway by phosphorylating several important cell cycle control modulators, such as tumor suppressor p53. The exact functions of the FHA domain of Chk2 are still not clearly known, while it has been generally considered as the regulator to the Chk2 kinase activities. In this dissertation, efforts have been put to express and purify the unstable Chk2 FHA domain. After fine tuning the conditions, great improvements have been observed on the NMR spectrums, which are the essentials for the future structural work. Well-resolved 2D and 3D spectra have been obtained. Seeking to identify binding substrates for Chk2 FHA domain, combinatorial peptide library screenings have been utilized to determine the consensus sequence of the target phosphopeptides. Chk2FHA was found to bind to phosphotyrosyl peptides containing pYXXXL motif. A phosphopeptide from p53 centered by (pY107)GFRL was identified with mild affinity (KD = 6.1¦ÌM) to Chk2 FHA domain. Chk2 complex structure with this pY-peptide was proposed by structural modeling. It features similar global structure as the recently solved Chk2FHA-pT-peptide complex, while the interaction details between Chk2FHA and phosphopeptides might be different. The consensus sequence identified by pT-peptide library screening displays strong selection of Ile at the +3 position. A phosphopeptide with sequence containing pT329LQI from p53 was shown to bind to Chk2FHA (KD = 11.7 ¦ÌM) and perturb its global structure, though the physiological impact of this binding event still needs to be elucidated. Another pT-peptide containing pT1851YLI from tumor suppressor BRCA1 has also been investigated and it exhibits decent affinity (KD = 1.2 ¦ÌM) to Chk2FHA. C. elegans Chk2 was recently discovered and very little is known about its functions. Ce-Chk2 has been demonstrated to play key roles in meiotic recombination, while it conserves the function of a DNA damage checkpoint at the pachytene stage. Investigation on Ce-Chk2 will shed more light on the properties of the Chk2 family. While no report on Ce-Chk2 at the protein level has been published to date, we have successfully expressed the full-length, FHA domain and kinase domain of Ce-Chk2 in E. coli. Purification of Ce-Chk2 FHA domain was achieved and combinatorial peptide library screenings were carried out to search for the binding targets of Ce-Chk2FHA. It was found that Ce-Chk2FHA, similar to Chk2FHA, strongly selects Leu at the +4 position in pY-peptides. The pT- and pS-peptide libraries have also been screened. Advisors/Committee Members: Tsai, Ming-Daw.

▼ Growth factor independence-1 (Gfi-1) is a zinc-finger transcriptional repressor that plays a critical role in hematopoiesis. Gfi-1 regulates the development of myeloid and lymphoid cells, and controls hematopoietic stem cell self-renewal. Gfi-1 is weakly oncogenic but strongly cooperates with oncoprotein Myc in lymphomagenesis. How Gfi-1 functions in hematopoiesis remains poorly understood. Data presented here demonstrate that Gfi-1 represses p21Cip1 and MBP through two distinct mechanisms. Gfi-1 interacts with Myc-interacting zinc-finger protein (Miz-1), a transcriptional activator regulating cell cycle progression and apoptosis, and is recruited by Miz-1 to the promoter of Miz-1 target gene p21Cip1, which encodes a potent cell cycle inhibitor, leading to transcriptional repression. Repression of p21Cip1 by Gfi-1 is independent of direct DNA-binding. Knockdown or deficiency of Gfi-1 results in augmented p21Cip1 expression. Interestingly, Gfi-1 forms a ternary Gfi-1/Miz-1/Myc complex on the p21Cip1 promoter and collaborates with Myc in the repression of p21Cip1. This Miz-1-dependent transcriptional repression by Gfi-1 also applies to other Miz-1 target genes encoding cell cycle inhibitors p15Ink4b and p27Kip1. Consistent with the mechanism of Miz-1-dependent transcriptional repression, Gfi-1 also represses growth inhibitory cytokine TGF-β-activated p21Cip1 independent of DNA-binding. Interestingly, Gfi-1 expression is downregulated by TGF-β, suggesting a role of Gfi-1 in TGF-β-mediated growth inhibition. MBP encodes a cytotoxic granule protein expressed in eosinophils and basophils. Our data identify MBP as a new target of Gfi-1-mediated transcriptional repression. Unlike p21Cip1, however, the repression of MBP by Gfi-1 requires Gfi-1 direct DNA-binding as evidenced by the fact that the Gfi-1 dominant negative mutant N382S, which is defective for DNA-binding, relieves the transcriptional repression of MBP by Gfi-1. Indeed, knockdown of Gfi-1 results in enhanced expression of MBP. Expression of the N382S mutant has been shown to cause premature apoptosis of myeloid cells induced to differentiate by G-CSF. Interestingly, overexpression of MBP also results in increased apoptosis during G-CSF-stimulated terminal neutrophilic differentiation, indicating that elevated MBP expression may contribute to the N382S-associated apoptosis of differentiating myeloid cells. These data suggest that the transcriptional repression of MBP by Gfi-1 may contribute to the role of Gfi-1 in regulating granulocyte development. Taken together, our study demonstrates Gfi-1-mediated transcriptional repression of p21Cip1 and MBP by two different mechanisms. Gfi-1, via binding to Miz-1, is recruited to p21Cip1 and other Miz-1 target genes leading to transcriptional repression, and Gfi-1 represses MBP, however, through direct DNA-binding. These findings provide new insights into the transcriptional regulation by Gfi-1 and may have broad implications for better understanding the role of Gfi-1 in normal hematopoiesis and tumorigenesis. Advisors/Committee Members: Dong, Fan.

▼ Common fragile sites are conserved regions of mammalian chromosomes that are exquisitely sensitive to forming gaps or breaks on metaphase chromosomes after partial inhibition of DNA synthesis. Studies revealing that fragile sites and fragile site genes are deleted or rearranged in many cancer-derived cells have demonstrated the importance of these loci in genome instability in cancer. Our laboratory has primarily been working on two common fragile site genes, FHIT and WWOX, which are located at FRA3B and FRA16D, respectively, the two most frequently expressed and best-characterized fragile sites in the human genome. FHIT and WWOX are both tumor suppressor genes that frequently show reduction or loss of expression in various human cancers. In this research which is focused on identifying signal pathways affected by these tumor suppressors, we demonstrated that: 1) Fhit down-modulates the expression of a cell cycle regulatory protein, cyclin D1, in various cells and experimental conditions. Cyclin D1, an oncogenic protein up-regulated in many human cancers, was down-modulated by Fhit overexpression by contributing to degradation of cyclin D1 through the proteosome pathway. 2) The WWOX gene has a role in prostate cancer development; Wwox expression was reduced or lost in prostate cancer-derived cells and tissues, in part due to DNA hypermethylation in the WWOX regulatory region. Both WWOX mRNA and protein expression can be restored after inhibition of DNA methylation and histone deacetylation. Restoration of WWOX suppressed prostate cancer growth and induced apoptosis in vitro and in vivo. Furthermore, Wwox suppressed prostate cancer-derived cell growth through binding and cytoplasmic sequestration of the transcription factor Ap2gamma, preventing Ap2gamma from entering the nucleus to activate ErbB2, and blocking ErbB2-mediated androgen receptor signaling. Advisors/Committee Members: Huebner, Kay F.

▼ Multicarrier CDMA has emerged recently as a promising candidate for the next generation broad-band mobile networks. Since multicarrier CDMA combines the multicarrier technique and the spread-spectrum CDMA technique, many multiuser detection methods used in DS-CDMA can be applied to multicarrier CDMA system. In this thesis, we propose a direct blind multiuser detection method for multicarrier CDMA based on linear prediction. Using only the spreading code of the desired user, we extract the column vector subspace corresponding to the signal of interest from the channel matrix of the received complex signal. And then zero-forcing (ZF) and minimum mean square error (MMSE) detectors are constructed. Our algorithms do not require channel estimation and avoid the channel estimation error. Simulations show that in most conditions, our algorithms outperform the typical subspace-based algorithm and the eigen-method used in a multicarrier system. Advisors/Committee Members: Fan, Dr. Howard.

▼ Acetylation of the N-terminal tails of newly synthesized histones H3 and H4 by type-B histone acetyltransferases (HATs) is thought to play a role in chromatin assembly. While originally known as a cytoplasmic factor, Hat1p, the catalytic subunit of the first identified type-B HAT, has been shown to exist in both the cytoplasm and the nucleus. Hat1p and specific lysine residues in the histone H3 N-terminal tail have been shown to be redundantly required for telomeric silencing, and multiple protein factors have been found to be involved in both telomeric silencing and DNA damage repair. This raised the possibility that Hat1p might also be involved in DNA damage repair. Substitution of specific lysine residues in the histone H3 N-terminal tail, as well as combination of specific lysine residue replacement in H3 and HAT1 deletion resulted in enhanced sensitivity to methyl methanesulfonate. This sensitivity was specific for DNA double Strand beraks (DSBs), as these mutants were sensitive to endonuclease digestion, but not to UV irradiation. While histone H3 mutations showed minor effects on nonhomologous end joining, the primary defect in the histone H3 and HAT1 mutants was in pathway of homologous recombination. Subsequent epistasis analysis indicates that the histone H3 and Hat1p may contribute to DSB repair through an Asf1p-dependent chromatin assembly pathway. Hat1p was then found to become associated with damaged DNA. Further kinetic analysis showed that Hat1p localization to DSB occurs after the phosphorylation of histone H2A S129 and concomitantly with the recruitment of the recombinational repair factor Rad52p. In addition, the nuclear Hat1p-associated histone chaperonee Hif1p was also recruited to DSB and followed similar kenetics as that of Hat1p. Moreover, the acetylation of all four histone H4 N-terminal domain lysine residues including 5, 8, 12 and 16 was increased following DSB generation on the MAT locus, but only acetylation of lysine 12, the primary target of Hat1p, is dependent on the presence of Hat1p. The results presented here suggest that Hat1p is responsible for specific changes in histone modification that occur during the course of recombinational repair of DSB and thus plays a direct role in DSB repair. Advisors/Committee Members: Parthun, Mark.

▼ Zn2+ dyshomeostasis in brain might be involved in the pathogenesis of brain diseases such as Alzheimer's disease and stroke. Thus, neurons tightly control the level of intracellular free Zn2+ within a narrow window of optimal concentration. In this study, the mechanisms of transporter-mediated Zn2+ extrusion and uptake across the plasma membrane of cultured cortical neurons were studied. Changes in intracellular Zn2+ levels were tracked in individual neurons by microfluorometry using a Zn2+ selective fluorophore, FluoZin3. Zn2+ uptake and efflux was measured by first loading cultured cortical neurons with Zn2+ then reducing extracellular Zn2+ to near zero by addition of EDTA. Studies revealed that the primary means of Zn2+ efflux in cortical neurons required both extracellular Na+ and Ca2+. A Na+, Ca2+/Zn2+ exchanger mechanism is proposed to extrude Zn2+ at the expense of electrochemical sodium and calcium gradients. ZnT1 (SLC30A1) protein levels were reduced around 40% in cultured cortical neurons (*p2+ efflux to decrease compared with the control neurons (*p2+ efflux transporter or at least regulating Zn2+ efflux. In case of Zn2+ uptake, acidosis or alkalosis both inhibited Zn2+ uptake at resting condition. Depolarization induced large Zn2+ uptake in neurons. ZIP1 (SLC39A1) protein levels were reduced around 22% by shRNAi (*p2+ uptake (*p2, the hZIP1 expression was highly reduced observed by immunostaining. The findings of my studies can be summarized into three aspects: firstly, a Na+, Ca2+/Zn2+ exchanger and ZnT1 appear to be separate routes acting to reduce intracellular Zn2+ levels in cultured cortical neurons. Second, a Zn2+, HCO3- symporter mechanism and ZIP1 could uptake Zn2+ into neurons at resting condition. Third, hZIP1 protein expression can be regulated by zinc levels at translational levels. Advisors/Committee Members: Colvin, Robert A.

▼ Coulter Counter (CC) is a device for counting small particles by recording the electrical current change during the translocation of the particle through a small pore. By counting the number of pulses in the measured current signal, the number of particles in the solution can be determined. The size and translocation time can also be deducted from the magnitude and duration of the pulses. In order to produce measurable current change, only particles of comparable sizes with the pore can be characterized, however. With rapid development of present micro/nano-fabrication technologies, CC is now widely used to characterize various micro/nano size particles, including small molecules, proteins, and even DNA. This thesis presents an electrical model and a comprehensive multi-physical model of ion transport in CC. The electrical model represents the classical theory of CC. From this model, the off-center effect and particle shape effect were further explored for which analytical results are not available. The multi-physical model involves a coupled system of the Navier-Stokes equation for flow field, the Nernst-Planck equation for electrolyte ion transport, and the Poisson equation for electrical field. The model is used to simulate the electrolyte flow with a surface charged particle in a nano-channel, representing the core part of CC. 2D axial symmetric system is used to reduce the computational time. The model predicts the flow and electric fields as well as the distribution of the ion concentrations in the channel. The effects on electric current through the channel are then investigated by systematically varying the particle surface charge, size, and electrolyte concentration. The Electrical Double Layer polarization under electrical and pressure fields was also investigated. Different patterns of polarization were found and compared. Advisors/Committee Members: Wang, Guo-Xiang.

▼ Both the Geographic Information Systems (GIS) and the Statistical Analysis System (SAS) developed by geographers and statisticians, respectively, were employed to detect the impact of the previous Feed Materials Production Center (FMPC) at Fernald, OH on urinary cancer incidence in community residents participating in the Fernald Medical Monitoring Program (FMMP). To explore the spatial pattern of urinary cancer incidence, GIS was employed to conduct address matching and create quadrats. Moran's Index, a measurement of spatial autocorrelation, was calculated in SAS. Since the spatial autocorrelation was not significant, a backward elimination strategy followed by a stratification analysis of weighted logistic models with DISTANCE of each participant to FMPC as the main factor of interest was employed. Among the people who drank well water, the nearer they lived to FMPC, the more likely it was for them to get urinary cancer (Risk Ratio = 0.703, 95% CI = (0.56, 0.88) ). AGE, GENDER and SMOKING were also included in modeling as covariates. The data indicate that GENDER may be a potential effect modifier. In order to show how to incorporate the spatial autocorrelation into a regular logistic regression model, autologistic regression models were built using PROC GENMOD in SAS, which confirmed that urinary cancer incidence presented no obvious spatial pattern in the Fernald vicinity. Key Words: urinary cancer incidence, Fernald Medical Monitoring Program, spatial autocorrelation, Moran's Index, GIS, weighted logistic model, autologistic regression model. Advisors/Committee Members: Succop, Paul.

▼ In this research, the volatility of PCB was investigated. A simple microcosm of sediment, water and air that allowed for (pseudo) one-dimensional transport of PCB was established to conduct PCB volatilization studies. First, the rate and extent of PCB volatilization from sediment and other substrates spiked with two PCB congeners, 4,4'-dichlorobiphenyl (DCB) and 2,2', 4, 4', 5, 5'-hexachlorobiphenyl (HCB) were determined experimentally. Second, the rate of PCB volatilization from two types of Lake Hartwell sediments, uniformly naturally contaminated with PCBs, was measured. A relationship between the rate of volatilization and the extent of substitution of the PCB with chlorine was accessed. A fundamental mathematical model of PCB transport in a sediment-water-air system was developed. The data obtained from volatilization experiments were applied to validate the one-dimensional mathematical model. The calibrated model was run to simulate various scenarios that led to better understanding of the transport mechanism of PCBs. For all the scenarios investigated, experimental results revealed significant volatilization of DCB from all the different substrates studied. Important observations included: Volatilization of DCB from water was very fast, the higher the water level, the slower the volatilization rate; The rate of volatilization decreased when the sediment lost moisture; the rates of PCB volatilization from contaminated silica sand and betonite clay were very similar and faster than the rate observed for natural sediments but still slower than the rate of volatilization from water; volatilization of PCB was positively correlated with sediment contamination level; volatilization of solid PCBs from glass surfaces was surprisingly fast; PCBs volatilized faster from surfaces covered with a thin water layer than when no water was present; in all cases studied, the volatilization of HCB was dramatically lower than that of DCB. The data obtained from Lake Hartwell study showed significant volatilization of PCBs. PCBs volatilized faster from the deep layer sediment than from the top layer sediment. Results also indicated lower chlorinated congeners volatilized preferentially. Advisors/Committee Members: Suidan, Dr. Makram.

▼ The dissertation consists of two essays. Essay I proposes a theory which explicitly models the strategic fraud detection behavior of the regulator (e.g., the SEC), and studies the strategic interaction between corporate fraud commission and detection. The model generates several new testable empirical implications. Essay II empirically studies whether the SEC strategically responds to fraud commission and how effective Sarbanes-Oxley is in reducing fraud commission using detected fraud data of corporate America in the last 10 years. Essay I: The paper considers an agency model of fraudulent misreporting which implies a rich set of relationships between the commission of fraud, the observation or detection of fraud, economic performance, and the compensation policy of the firm. The paper develops a number of testable empirical implications and highlights several interesting phenomena, including implications on exogenous variables that can cause an increase in the amount of fraud committed but a decrease in the amount of fraud being observed (and visa versa). Thus, empirical studies that seek to identify the firm or managerial characteristics associated with the commission of fraud cannot infer a relationship by simply examining how the amount of observed fraud varies with these characteristics. In addition, the paper also shows that an increase in an industry’s growth potential can cause that industry to fall from a high-productivity pooling equilibrium (with high levels of incentive compensation and effort and, as a result, many high-productivity firms) to the lower-productivity mixed-strategy equilibrium (with lower levels of incentive compensation and effort and, as a result, fewer high-productivity firms), resulting in a drop in economic performance. Essay II: In the wake of recent financial scandals, there are heated debates over whether the SEC is effective in combating fraud as well as over the costs and benefits of the Sarbanes-Oxley Act. This paper investigates two research questions empirically: 1. Does the SEC strategically respond to fraud commission? 2. How effective is SOX in reducing fraud commission? Using a sample of firms subject to SEC litigations for fraud and employing the bivariate probit with partial observability technique, we find strong evidence in favor of theoretical predictions with the assumption that the regulator is strategic in combating fraud, but contradicting to theoretical predictions assuming that the fraud detection environment is exogenous or mechanical (i.e., without a strategic regulator). We also find that SOX has been very effective and decreased fraud commission by two thirds after its enactment. Our finding should provide some useful insight to policy makers in light of the current debates. Advisors/Committee Members: Slezak, Steve.

Analog very large scale integrated circuits design of two-phase and multi-phase voltage doublers with frequency regulation Advisors/Committee Members: Starzyk, Janusz.

▼ C57BL/6J male mice fed a high-fat diet become obese and develop type 2 diabetes (T2DM), which serves as a model of obesity-associated diabetes in humans. In this study, proteins were extracted from the pancreas of diabetic and control mice and were resolved by 2 dimensional gel electrophoresis (2-DE). The pancreatic protein profiles were compared between control and diabetic mice. Eleven protein spots were differentially expressed and 10 of them were identified by mass spectrometry (MS) analyses. REG1 and REG2 proteins, which may be involved in the regeneration of pancreatic ß-cells, were up-regulated very early in the progression of obese mice to T2DM. Up-regulation of Reg1 and Reg2 may reflect the effort by the pancreas to ameliorate the hyperglycemic condition by stimulating the proliferation of pancreatic ß-cells resulting in subsequent insulin secretion. Rho GDP-dissociation inhibitor 1 (GDI-1), 1-Cys peroxiredoxin protein, and pancreatic elastase 3B were also up-regulated in the pancreas of diabetic mice relative to control. However, how these expression levels are related to the diabetic condition is unclear. Glutathione peroxidase (Gpx1), which functions in the clearance of reactive oxidative species (ROS), was down-regulated in diabetic mice. The down-regulation of glutathione peroxidase in pancreas could contribute to the progressive deterioration of ß-cell function, which may be related to the hyperglycemia induced oxidative stress. Finally, the protein levels of the receptor of activated protein kinase C1, which function in many signaling cascades, was decreased in diabetic mice when compared with normal controls. Because of their potential importance to T2DM, Reg 2 and Gpx1 were selected as potential targets of further investigation. Generation of transgenic mice that over-express Reg2 or Gpx1 can provide valuable information to understand the biological function of Reg2 and Gpx1 during the development of diabetes in mice. As a part of this strategy, expression vectors for Reg2 and Gpx1 were constructed and stable mammalian cell lines which express the genes were established. Expression was confirmed at the mRNA and protein levels for the two genes. Transgenic mice with the Reg2 gene under the control of mouse metallothionien I promoter were generated. These studies will provide a means to study the physiological function of these proteins in association with diabetes and ß-cell function. Advisors/Committee Members: Kopchick, John J.

▼ The more stringent regulations for wastewater discharge present new technology challenges to wastewater treatment (WWT) plants. There is a particular pressing need for improving the hygienic quality of the treated water. Membrane bioreactors (MBRs) represent one of the most innovative approaches to restrain the release of pathogens from WWT plants. Using membranes with a pore-size of 0.1~0.5 mm or less, not only bacteria but also viruses are virtually completely retained. However, membrane fouling is a very serious problem faced by MBRs. Cake layer formation generates largest resistance for membrane filtrations. It was well known that adding flocculants could flocculate small sludge flocs and soluble EPS (Extracellular Polymeric Substances) into large flocs. Flocculated sludge flocs can form a more porous cake, which would enable a higher permeate flux. A procedure was developed to prepare glutaraldehyde-crosslinked chitosan nanofibers as a flocculant that is insoluble but well dispersible in water. Polyacrylonitrile (PAN) nanofiber serves as the reference for evaluating the nanofiber structure contribution to membrane filtration, because of its poor flocculation ability. Another commercial soluble flocculant MPE50 (Nalco Company, Naperville, Illinois) was also compared. The toxicity/inhibition test, turbidity reduction test, and short-time filtration test were conducted to evaluate the flocculant performance. There was no obvious inhibition to the growth of microorganisms by addition of 50~100 mg/L of any of the tested flocculants. It was also demonstrated that adding dissolved chitosan and MPE50 could help reduce the turbidity of the supernatant up by 80% and 55% respectively after allowing the sludge to settle for 45 minutes. Chitosan was effective in the pH range of 5-8, while MPE50 was effective in the wider range of 4-9. PAN nanofiber and crosslinked chitosan nanofiber showed low turbidity reduction ability at concentrations higher than 25 and 50 mg/L, respectively, after adjusting for the turbidity of nanofibers themselves. Total filtration resistance Rt and membrane fouling rate were calculated from the short-term filtration tests. Both dissolved chitosan and MPE50 could improve the filtration performance with lower transmembrane pressure (TMP) and higher permeate flux. However, the performance of PAN and crosslinked chitosan nanofibers was not very consistent from replicate experiments. It is demonstrated that adding nanofiber would not harm the filtration system but the crosslinked chitosan did not improve the filtration process as expected. The possible reasons are discussed for future improvements. Advisors/Committee Members: Ju, Lu-Kwang.

▼ Protein hydration dynamics is essential for many biological functions. However, understanding protein hydration dynamics has been technically challenged by the time and spatial resolution. This dissertation thus is a systematic investigation of protein hydration dynamics by integrating ultrafast fluorescence spectroscopy with the site-directed mutagenesis method. Using single tryptophan as the local optical probe, we first studied the site-specific solvation dynamics in various different conformations of the prototype peptide melittin and protein human serum albumin; both studies showed a strong correlation between local solvation dynamics and peptide/protein conformation transitions, and the critical role of hydration water in the structural integrity of the peptide/protein. To clarify the molecular interpretation of the solvation dynamics from time-resolved fluorescence studies, we also examined the local solvation dynamics at the surface of protein Staphylococcus nuclease using site-directed mutations; we replaced the local charged residues in close proximity to the tryptophan probe one at a time with an uncharged residue and did not observe significant change in the measured solvation dynamics, thus confirming that solvation correlation functions mainly measure the water dynamics in the protein hydration layer; the solvation dynamics is typically biexponential with the fast time constant resulting from local water relaxation in the hydration layer while the slow time from hydration water network rearrangement tightly coupled with protein fluctuations. To better understand the molecular mechanism of tryptophan fluorescence behaviors in proteins, we then surveyed the tryptophan fluorescence in more than 40 proteins with the femtosecond fluorescence method and molecular dynamics simulations. We were able to identify the carbonyl- and sulfur-containing residues as able quenching groups of tryptophan fluorescence within 100-ps; the former includes glutamine and glutamate residues while the later disulfide bond and cysteine residues. We studied the protein dynamics in human thioredoxin and were able to distinguish four time-overlapping dynamical processes at its active-site and determined their respective time scales; these results elucidated the temporal evolution of hydration water motions, electron transfer reactions and local protein fluctuations at the active site of human thioredoxin, and illustrated continuously synergistic dynamics of biological functions over wide time scales. Building on our understanding of hydration dynamics in isolated proteins or protein mimics, we are applying protein hydration dynamics as a tool to address more biologically relevant questions. Preliminary results are summarized in the final chapter for our efforts to unveil the molecular mechanism of molecular recognition in calmodulin using femtosecond-resolved fluorescence spectroscopy. Advisors/Committee Members: Zhong, Dongping.

▼ This thesis focuses on the synthesis and characterization of chalcogenide nanomaterials for thermoelectric energy conversion and N-doped nanostructured metal oxides for photocatalysis. A sonoelectrochemical method was applied to synthesize Bi2Se3 heterostructured nanowires and PbTe nanorods. Experimental parameters that affect the growth of these nanoparticles are discussed. Furthermore, nanostructured n-type Bi2Se3 and p-type PbSe thin films were fabricated by a chemical bath deposition method. Thermoelectric transport measurements showed large Seebeck coefficients for both Bi2Se3 and PbSe thin films at room temperature. The crystal orientation and transport properties of nanostructured PbSe thin films are pH sensitive. The results of transport measurements on nanostructured PbSe thin films suggest that nanostructuring can enhance the Seebeck coefficient but lower the electrical conductivity by restricting the mobility. On the other hand, a chemical approach was introduced to incorporate N into TiO2, ZrO2, HfO2, CeO2 and SnO2 nanoparticles. XPS results indicate that N could be doped into these materials and N-doping levels could be controlled. Reflectance spectra show that visible-light absorptions of the nanoparticles are enhanced through N-doping. Furthermore, an enhanced visible-light photocatalytic activity was observed for N-doped metal oxide nanoparticles. Both the optical and photocatalytic properties of N-doped nanoparticles are dependent on N-doping levels. Advisors/Committee Members: Clemens, Burda.

▼ Pneumocystis carinii is an opportunistic infectious agent. Immunocompromised or immunodeficient individuals such as AIDS patients have a risk of developing life-threatening P. carinii pneumonia (PcP). Previous work showed that incubating Pneumocystis carinii organisms with radiolabeled mevalonate in the presence of lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, which converts endogenous cold HMG-CoA to mevalonate did not increase radiolabeling of sterols. This suggested that P. carinii had a lovastatin-insensitive pathway to sterols. Recently, leucine was found to serve as the major carbon source for sterol biosynthesis in some Leishmania species, but the pathway in these parasites involved the HMG-CoA to mevalonate step. In the present study, the mechanism of leucine uptake by P. carinii was demonstrated to be by carrier-mediated transport and further experiments showed that the organism takes up leucine by facilitated diffusion. Since P. carinii is able to take up leucine from the extracellular environment, whether it could metabolize leucine for its sterols was tested by using a cell-free system. Preliminary results showed that leucine was able to be incorporated into P. carinii sterols and lovastatin had no effect on this incorporation. This suggested that P. carinii has a pathway from leucine that enters sterol biosynthesis at a step after the HMG-CoA to mevalonate step. Further studies were conducted to examine the incorporation of leucine into specific sterols synthesized by P. carinii. For this study, 1-dimensional thin-layer chromatography (TLC) and preparative gas liquid chromatography were used for separation and isolation of sterol components, and the radioactivity in them was measured. Advisors/Committee Members: Kaneshiro, Edna.