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1. Xanthakos, Stavra A. Prevalence and Determinants of Hepatic Steatosis in Young Adult Women.

Degree: MS, Medicine : Epidemiology (Environmental Health), 2006, University of Cincinnati

► The prevalence of nonalcoholic fatty liver disease (NAFLD) in children and young… (more)

▼ The prevalence of nonalcoholic fatty liver disease (NAFLD) in children and young adults is unknown, as population-based studies are often limited by use of serum aminotransferases as surrogate markers, lacking imaging or biopsy data to confirm NAFLD. This study determines the prevalence and determinants of NAFLD in young adult females using magnetic resonance imaging (MRI) to measure hepatic steatosis. Prevalence was hypothesized to be 15%. Methods: 278 female subjects, ages 25-27 years, were recruited from a population-based cohort. Exclusion criteria included weight >300 lbs, daily alcohol intake >20 gm/day, hepatotoxic medications, or serologic evidence of hepatitis B, C or autoimmune hepatitis. Anthropometric indices, serum lipids, insulin, glucose and aminotransferases (ALT, GGT) were measured. The hepatic fat index (HFI) was measured using a biopsy-validated MRI technique. Descriptive statistics and nonparametric tests were used, analyzing races separately to control for higher prevalence of obesity in the black females. Results: 38% of the cohort was obese (BMI > 30 kg/m2), but only 4% had abnormal ALT (>35 IU/L). Black females (N=157) had a higher prevalence of obesity (47% vs. 27%, p<0.001), abnormal waist circumference (40% vs. 25%, p=0.02), hyperinsulinemia (54% vs. 30%, p<0.001) and metabolic syndrome (10% vs. 5%, p =0.15) compared to white females. Mean HFI was 3.0 ± 2.6 (range 0 - 26) with no significant racial differences. Prevalence of abnormal HFI was 2.5%, with no significant racial differences (blacks 1.9%, whites 3.3%). BMI, waist-hip ratio, waist circumference, triglycerides, and GGT directly correlated with HFI. Of subjects with abnormal HFI, 100% were obese and hyperinsulinemic, 80% had abnormal waist circumference, but only 29% had abnormal ALT. Conclusions: Despite a high prevalence of obesity, significant hepatic steatosis is not very prevalent in young black and white adult women. Black women have a significantly higher prevalence of risk factors for NAFLD, but a strikingly low prevalence of hepatic steatosis, confirming that black race may protect against NAFLD. Shorter duration of obesity due to young age may contribute to a lower than anticipated prevalence and severity of hepatic steatosis in this population-based cohort of young adult females. Advisors/Committee Members: Heubi, Dr. James E.

Keywords: Nonalcoholic fatty liver disease; Nonalcoholic steatohepatitis; Obesity; Magnetic Resonance Imaging

2. Xavier, Graziane de O. Motivational Teaching Strategies in a Brazilian EFL School: How Important are they and how Frequently are they used?.

Degree: MA, Linguistics (Arts and Sciences), 2005, Ohio University

► For over two decades, scholars in the field of second language teaching… (more)

Subjects: Language, Linguistics

Keywords: Motivational teaching strategies; EFL/ESL Pedagogy; L2 Classroom research; EFL Teaching in Brazil; Motivational Conceptual Domains of Teaching Strategies

3. Xia, Honggang. On zeros of cubic L-functions.

Degree: PhD, Mathematics, 2006, Ohio State University

► We study the distribution of zeros of cubic L-functions and obtain a… (more)

Subjects: Mathematics

Keywords: zero density theorem, large sieve

4. Xiang, Kun. The role of L-type voltage-gated calcium channels in hippocampal CA1 neuron glutamate and GABA-A receptor-mediated synaptic plasticity following chronic benzodiazepine administration.

Degree: PhD, College of Graduate Studies, 2007, University of Toledo Health Science Campus

► Clinicians require caution prescribing benzodiazepines for a prolonged period of time because… (more)

▼ Clinicians require caution prescribing benzodiazepines for a prolonged period of time because of the development of functional tolerance and dependence. The objective of these dissertation studies was to evaluate the role of L-type VGCC in mediating glutamate receptors and GABAA receptor functional changes in the expression of benzodiazepine tolerance and dependence following a 1-week FZP oral treatment regimen in rats. Initially, AMPA receptor-mediated mEPSC amplitude in hippocampal CA1 neurons was evaluated in rats withdrawn from 1-week FZP administration, using whole-cell electrophysiological recordings, and was found to correlate with benzodiazepine withdrawal-anxiety in rats measured using an elevated plus-maze. A compensatory role of NMDA receptor functional down-regulation was further identified as a counterbalance to AMPA receptor-mediated neuronal hyper-excitation. Following pharmacological antagonism of NMDA receptor and VGCC function, a role for regulation of L-type VGCCs, but not NMDA receptors, in mediating enhanced AMPA receptor function and benzodiazepine withdrawal anxiety was identified. Further studies concentrated on the regulation of L-type VGCC function following chronic benzodiazepine administration using whole-cell voltage-clamp method. The temporal pattern of L-type VGCC functional regulation was evaluated following chronic benzodiazepine administration. The direct concentration- and use-dependent effect of the benzodiazepines to affect L-type VGCC currents was also investigated. Based on the evidence of L-type VGCC function changes and its role in mediating AMPA receptor synaptic plasticity following chronic FZP administration, the relation between L-type VGCC and GABA receptor was further explored. Pharmacological antagonism was again applied for investigating the role of L-type VGCC in mediating GABAA receptor function using whole-cell ctrophysiological recordings of GABAA receptor-mediated currents. GABAA receptor channel kinetics and single channel conductance was evaluated after L-type VGCC antagonist application both in vivo and in vitro. In all, these studies would give the insight of an L-type VGGG-dependent Ca2+ signaling mechanism in differentially mediating specific glutamate receptors and GABAA receptor synaptic changes that are associated with benzodiazepine tolerance and dependence. To serve as the foundation for more mechanistic studies, a model of the cellular mechanisms underlying benzodiazepine tolerance and dependence was proposed in these dissertation studies based on the present findings, and on past evidence from our laboratory and others. Advisors/Committee Members: Tietz, Elizabeth.

Keywords: Benzodiazepine; L-VGCCs; Hippocampus; AMPA receptor; Dependence/Tolerance; GABA receptor

5. Xiang, Tengfei. Synthesis and Characterization of Polymeric Schiff Bases from 2,5-Diformylfuran.

Degree: MS, Chemistry, 2012, University of Akron

► Furan derivatives have the potential to be an alternative resource since it… (more)

Subjects: Chemistry

Keywords: Polymer; Schiff Base; Furan

6. Xiangxiang, Fang. Characterization and Modeling of SiC Power MOSFETs.

Degree: MS, Electrical and Computer Engineering, 2012, Ohio State University

► SiC power MOSFETs are great candidates for high-voltage power switching applications because… (more)

Subjects: Electrical Engineering

7. Xiang, Yang. Reachability, Routing and Distance Labeling Schemes in Graphs with Applications in Networks and Graph Databases.

Degree: PhD, College of Arts and Sciences / Department of Computer Science, 2009, Kent State University

► Three fundamental and related problems, with applications in networks and graph databases,… (more)

▼ Three fundamental and related problems, with applications in networks and graph databases, are the focus of this dissertation. They are: how to answer quickly whether a vertex can reach another vertex in a directed graph, using a succinct representation of the reachability information; how to route a message efficiently from a source vertex to a destination vertex and how to calculate or estimate quickly the distance between any two vertices, using very limited information stored locally at those vertices. To efficiently answer reachability queries, we introduce a novel path-tree structure to assist with the compression of transitive closure and answering reachability queries. Our path-tree generalizes the traditional tree cover approach and can produce a better compression rate for the transitive closure. We also propose a 3-hop indexing scheme with high compression rate targeting the directed graphs with higher edge-vertex ratio. In addition, we show how to effectively summarize reachability information. To efficiently route messages in a graph, we investigate three strategies of how to use a spanning tree T of a graph G to navigate in G, i.e., to move from a current vertex x towards a destination vertex y via a path close to optimal. We investigate advantages and limitations of these strategies on several families of graphs such as graphs with locally connected spanning trees, graphs with bounded length of largest induced cycle, graphs with bounded tree-length, and graphs with bounded hyperbolicity. For most of these families of graphs, the ancestry information from a Breadth-First-Search-tree guarantees short enough routing paths. In many cases, the obtained results are optimal up to a constant factor. Finally, we propose distance and routing labeling schemes for circle graphs and polygon graphs by constructing collective additive tree spanners. We show that the family of n-vertex circle graphs admits a 2-additive distance labeling scheme with O(log3n)-bit labels and O(log n) time distance decoder, and the family of n-vertex k-polygon graphs admits a 2-additive distance labeling scheme with O(log k log2n)-bit labels and O(log k) time distance decoder. Similar routing labeling schemes are also designed for these families of graphs. Advisors/Committee Members: Dragan, Feodor.

Subjects: Computer science

Keywords: Reachability, Routing, Distance, Labeling schemes, Graphs, Networks, Graph databases

8. Xiao, Chang. The role of Sonic Hedgehog as a regulator of adult stomach physiology.

Degree: PhD, Medicine: Systems Biology and Physiology, 2011, University of Cincinnati

► Significance: Understanding the role of Sonic Hedgehog (Shh) as a regulator of… (more)

▼ Significance: Understanding the role of Sonic Hedgehog (Shh) as a regulator of adult stomach physiology and identifying the underlying mechanism are important for obtaining knowledge of the pathogenesis of Helicobacter pylori (H.pylori) and developing innovative genetic or pharmacologic therapeutic strategies to prevent gastric precancerous transformation. Background: Based on the correlation between loss of Shh and pre-cancerous transformation in the gastric mucosa during H.pylori infection, it is hypothesized that Shh functions as a morphogen in the adult stomach to control the normal function and differentiation of gastric epithelium. However, the physiological consequences of loss of Shh, independent of H.pylori –induced inflammation, remain unexplored. Objectives: Objectives that are met in this dissertation are as follows: (1) Create and characterize tissue specific-Shh deficient mouse models for studying the role of Shh in the homeostasis of gastric epithelium, (2) Identify the cellular and molecular events subsequent to Hedgehog signaling inhibition in both mouse models and cell culture systems, (3) Determine whether Hedgehog signaling is required for tissue regeneration and repair in injured gastric mucosa. Results: Constitutive deletion of Shh from parietal cells resulted in development of gastric hypochlorhydria, hypergastrinemia, foveolar hyperplasia and delayed zymogen cell differentiation. Deletion of Shh caused repressed E-cadherin expression, disrupted adherens- and tight-junctions formation and subsequent activation of Wnt pathway, which may account for the observed phenotype. The clinical process of loss-and regain- of Shh expression during H.pylori infection and eradication was recapitulated in tamoxifen-inducible parietal cell-specific Shh deficient mice, in which re-expression of Shh contributed to the histological restoration of gastric epithelium. Deletion of Shh also impaired the capacity of tissue regeneration and resulted in deficient ulcer healing in the adult stomach. Conclusions: Shh functions as a morphogen in the adult stomach regulating the differentiation and regeneration of gastric epithelium. Advisors/Committee Members: Zavros, Yana.

Subjects: Physiological Psychology

Keywords: Sonic Hedgehog; adult stomach; differentiation; tissue regeneration

9. Xiao, Dan. An implementation of kernelization via matchings.

Degree: MS, Electrical Engineering (Engineering), 2004, Ohio University

An implementation of kernelization via matchings Advisors/Committee Members: Juedes, David W.

Keywords: Kernelization; Matchings

10. Xiao, Feng. Molecular Mechanism of Connector-RNA Interaction of Bacteriophage Phi29 DNA Packaging Motor and Applications of Motor Components in Nanotechnology.

Degree: PhD, Engineering : Biomedical Engineering, 2009, University of Cincinnati

► During assembly, bacteriophage phi29 utilizes a motor to insert genomic DNA into… (more)

▼ During assembly, bacteriophage phi29 utilizes a motor to insert genomic DNA into a preformed protein shell called the procapsid. The motor contains one twelve-subunit head-tail connector gp10, a packaging RNA (pRNA) ring, and an ATPase protein, gp16, with unknown stoichiometry. It was proposed that the symmetry mismatch between the five-fold procapsid shell and twelve-fold connector (or the hexameric pRNA ring) produces a force to drive a rotation motor to translocate and compress DNA. There were discrepancies regarding the location of the foothold for the pRNA and whether the pRNA ring is a hexamer or a pentamer. To elucidate the mechanism of phi29 DNA packaging, both purified connector and purified procapsid were used for binding studies with in vitro synthesized pRNA. Removal of the N-terminal fourteen amino acids of the gp10 protein by proteolytic cleavage resulted in undetectable binding of pRNA to either the free connector or the procapsid. It is therefore concluded that pRNA bound to the 12-fold symmetrical connector to form a pRNA-connector complex and that the foothold for pRNA is the connector but not the capsid protein. Further work on the purified connectors showed that diverse RNA or DNA binds to the connector nonspecifically and with similar ability. However a combined pRNA ring-forming group was very specific for motor binding. It is generally believed that the specificity in RNA/protein interaction relies on molecular contact through a surface charge, or 3D structure matching. Here we report a new mechanism suggesting that the specificity and affinity of RNA/protein interaction relies on RNA static ring formation. pRNA did not form a ring prior to motor binding. Only those RNAs that formed a static ring, via the interlocking loops, stayed on the motor. Single interlocking loop interruption resulted in pRNA detachment. Extension or reduction of the ring circumference failed in motor-binding. This new mechanism was tested by redesigning two artificial RNAs that formed hexamer and packaged DNA. The results also confirmed that the stoichiometry of pRNA on the motor was a common multiple of two and three, thus, a hexamer. To build a synthetic nanomotor which mimics the functions of phi29 DNA packaging motor, connector protein was reengineered, and a thin lipid monolayer was used to direct the assembly of massive sheets of single layer patterned arrays of the reengineered motor dodecamer. Uniform, clean and highly-ordered arrays were constructed as shown by both transmission electron microscopy and atomic force microscopy imaging. The reengineered connector protein was also found to have the ability of forming a 20 x 30 nm ellipsoid nanoparticle containing 84 subunits or 7 connectors. The formation of this structure was mediated and stabilized by N-terminal peptide extensions. Reversal of the 84-subunit ellipsoid nanoparticle to its dodecamer subunit was controlled by the cleavage of the extended N-terminal peptide with a protease. The 84 outward-oriented C-termini were conjugated with a streptavidin binding peptide which can be used for the incorporation of markers. This further extends the application of this nanoparticle to pathogen detection and disease diagnosis by signal enhancement. Advisors/Committee Members: Guo, Peixuan.

Subjects: Biochemistry

Keywords: phi29 DNA packaging motor, bionanotechnology, hexamer, pRNA

11. Xiao, Haiyi. LOW TRANS FATTY ACID CONTAINING HYDROGENATED EDIBLE OILS.

Degree: MS, Paper Science and Engineering, 2007, Miami University

► An investigation of an electrochemical process for hydrogenating edible oils at low… (more)

Keywords: Vegetable Oil, Soybean Oil, Hydrogenation, Formate, Kinetics, Model

12. Xiao, Hong. Torque and Magnetization Measurements on the Heavy Fermion Superconductor CeCoIn5.

Degree: PhD, College of Arts and Sciences / Department of Physics, 2009, Kent State University

► We performed out-of-plane torque measurements on CeCoIn5 heavy fermion single crystals. Ourresults… (more)

Subjects: Physics

Keywords: heavy fermion, superconductivity

13. Xiao, Hong. Distribution of Metal Ions in Prostate and Urine during Prostate Carcinogenesis.

Degree: MS, Medicine: Biostatistics (Environmental Health), 2011, University of Cincinnati

► Prevention and detection of prostate cancer (PCa) are major concerns in the… (more)

Subjects: Biostatistics

Keywords: Prostate Cancer; metal ions; imputation; Hotelling's T square

14. Xiao, Jin. Pharmacokinetics, pharmacodynamics, metabolism, transport, and resistance studies of a novel histone deacetylase inhibitor FK228 (FR901228, NSC630176).

Degree: PhD, Pharmacy, 2004, Ohio State University

► Depsipeptide FK228 (FR901228, NSC630176), a promising histone deacetylase (HDAC) inhibitor, is currently… (more)

▼ Depsipeptide FK228 (FR901228, NSC630176), a promising histone deacetylase (HDAC) inhibitor, is currently undergoing clinical evaluation against various malignancies. Pharmacokinetic study of FK228 in the rat was first conducted with a focus on its pharmacokinetic properties and dose recovery. FK228 was found to be removed rapidly from the circulation with a total body clearance higher than the rat cardiac output, suggesting extensive metabolism in the blood. Dose recovery of FK228 was low (<15%) and there was an involvement of glutathione in FK228 elimination. Based on these results, we conducted in vitro metabolism studies, which led to identification of four glutathione conjugates and two thiols from rat and human blood incubations. Purification of these major metabolites followed by HDAC inhibition assays indicated that FK228 is a prodrug, with three major metabolites being more potent HDAC inhibitors than FK228 itself. A clinical pharmacokinetic study in AML and CLL patients was conducted. A pharmacokinetic-pharmacodynamic correlation study showed that HDAC inhibitory activity was inversely correlated with FK228 systemic exposure. This provided the first clinical evidence that FK228 was a prodrug. FK228 transport and uptake was investigated. It was found that FK228 is a substrate for both MDR1 and MRP1 by transport and cytotoxicity studies using specific inhibitors of the membrane transporters. In order to study the roles of MDR1 and MRP1 in acquired FK228 resistance, four FK228 resistant cell lines were established and characterized. We found that upregulation of MDR1, but not MRP1 or other ABC transporters, was responsible for the acquired resistance. The maintenance of acquired FK228 resistance depended on continuous drug exposure. No deregulation or impairment of the histone acetylation machinery was found. The MDR1 upregulation was further found to be via a reversible induction procedure, in which FK228 first inhibited HDACs and then caused hyperacetylation at the MDR1 promoter region to form the euchromatin structure ready for transcription. Overall, the dissertation work, involving both preclinical and clinical studies, provided valuable information of pharmacokinetics, bioactivation, transport and uptake, and resistance of the novel anticancer drug FK228. Advisors/Committee Members: Chan, Kenneth K.

Subjects: Health Sciences, Pharmacy

Keywords: FK228; depsipeptide; pharmacokinetics; pharmacodynamics; metabolism; prodrug; transport; MDR1; resistance; induction

15. Xiaojing, Li. An Investigation on Balance Switching Behavior in Credit Card Market.

Degree: PhD, Economics, 2008, Ohio State University

► Research on the behavior of credit card balance switching is underdeveloped because… (more)

▼ Research on the behavior of credit card balance switching is underdeveloped because data on the phenomenon are quite limited. The few previous studies suggest that consumers' choice of accepting a low introductory interest rate and then switching a balance to it mainly depends on the APR difference and the outstanding credit card balances. This dissertation uses the Consumer Finance Monthly data with much richer information about consumers' credit history and card holding conditions to investigate several fundamental factors in balance switching. A theoretical model is developed to rationalize revolvers' decision about balance switching. An exercise of dynamic optimization is conducted to reveal the relationship between switchers' reservation rate, payment process, and the predicted duration spell. Econometric methods are used to do the empirical analysis. Two endogenous switching regression models are applied to inspect two distinct responses on the switchers' side. The accelerated lifetime model is adopted to capture the impact of the credit card debt and other relevant factors on the duration spell for holding an initial card. Last, we address the issue of unobserved heterogeneity in a structural Weibull-Gamma duration model.The two theoretical predictions in this paper are consistent with the primary findings in our empirical study. Switchers wait for an interest rate that is regarded as sufficiently low. Consumers with worse payment history have to wait longer to receive such a low rate. Our survival analysis shows that the degree of stress over the debt rather than the amount of credit card debt itself hastens consumers' switching decision. The fitted hazard rate is bell-shaped both in the accelerated lifetime model with Gamma distribution and in the structural duration model. Cardholders are most likely to switch in the window of the sixth to twelfth month staying with old cards. Our empirical findings support "adverse selection" as in Ausubel (1991). Switchers improved their debt situation right after switching. But balance switching could only bring symptomatic relief but not a credit cure. Switchers still bear a heavier burden of credit card debt in the long run. Advisors/Committee Members: Dunn, Lucia.

Subjects: Economics

Keywords: Balance Switching, Default History, Adverse Selection, Endogenous Switching Regression, Accelerated Lifetime

16. Xiao, Linlin. Detection of Viable Foodborne Pathogens and Spoilage Microorganisms by Nucleic Acid Amplification Based Platforms.

Degree: PhD, Food Science and Nutrition, 2011, Ohio State University

► Foodborne disease outbreaks and microbial spoilage threaten public health and cause major… (more)

▼ Foodborne disease outbreaks and microbial spoilage threaten public health and cause major financial loss to the food industry and the society. Proper detection of concerned microorganisms in both raw materials and final food productes is a key to control the problems associated with microbial contamination. Several platforms were used to develop accurate, rapid, quantitative, specific and sensitive detection methods for targeted, viable cells, including RNA-based amplification platforms, such as nucleic acid sequence based amplification (NASBA) and reverse transcriptase PCR (RT-PCR), as well as DNA amplification coupled with sample treatment with DNA-intercalating dye propidium monoazide (PMA). In this study, a NASBA-molecular beacon assay targeting 18S ribosomal RNA has been established to investigate its potential to detect viable spoilage yeasts in juice products. Using the developed platform, less than 100 yeast cells per reaction was detected rapidly and specifically. In addition, significant decrease of amplification signals after lethal heat treatments indicated that this platform has the potential for rapid detection of viable spoilage yeasts if combined with quantitative analysis. Listeria monocytogenes contamination is a serious public health issue. The second part of my project compared the suitability of using 16S rRNA, inlA mRNA and rplD mRNA as indictors to detect viable L. monocytogenes cells via Taqman real-time RT-PCR assay. Under the conditions examined, the amplification signals by all three transcripts were reduced in dead cells, while the inlA and rplD mRNA signals decreased more dramatically than 16S rRNA. However, residue signals were still detected from dead cells even after extreme heat treatments. The ideal cell viability indictor should disappear rapidly and completely after cell inactivation. In the third part of my study, cDNA microarray analysis was conducted to select unstable mRNA targets. Using unstable transcript ornithine decarboxylase (ODC) mRNA screened by cDNA microarray assay, a Taqman real-time RT-PCR platform was established to detect viable and heat or disinfectant Pro-san® inactivated spoilage Pseudomonas. Under the experimental condition, ODC-specific RT-PCR signals were almost undectable after Pseudomonas cells were exposed to mild heat treatments. DNA-intercalating dye propidium monoazide (PMA) only can penetrate damaged cell membrane and form crosslinkage with DNA molecules, resulting in inhibition of amplification. PMA coupled Taqman real-time PCR was developed to examine viable Pseudomonas spp. PMA treatment successfully minimized false positive amplification signals by dead cells after heat, acid or disinfectant Pro-san® inactivation. Results from this study provided critical information regarding nucleic acid amplification-baed methods for viable foodborne microbial detection, and the new knowledge regarding overall RNA stability will have significant impact on data interpretation for transcriptome related studies. The rapid detection platforms developed have direct applications in both food industry and basic scientific research. Advisors/Committee Members: Wang, Hua.

Subjects: Food Science

Keywords: Foodborne Pathogens, Food spoilage, Nucleic Acid Amplification Based Detection Platforms, Viable microbial detection,RNA, cell viability indictor, Spoilage yeasts, Listeria monocytogenes, Pseudomonas, NASBA, real-time RT-PCR, PMA-PCR

17. Xiao, Mingli. An Empirical Study of Using Internet-Based Desktop Videoconferencing in an EFL Setting.

Degree: PhD, Instructional Technology (Education), 2007, Ohio University

► The recently developed Internet-based desktop videoconferencing as the highest level of CMC… (more)

▼ The recently developed Internet-based desktop videoconferencing as the highest level of CMC offers an authentic learning environment in which language learners can orally and visually interact with another human being in the target language, much in the same way as in a face-to-face interaction (Wang, 2004a, 2004b). The purpose of this study is to investigate the effects of interaction with native speakers via Internet-based desktop videoconferencing on EFL learners’ language proficiency in terms of fluency, accuracy and complexity, as well as examine L2 learners’ perception on using Internet-based videoconferencing to access native speakers to promote L2 learning.A control group and an experimental group were applied in this study, with 10 native-nonnative dyads participating in Internet-based desktop videoconferencing as a treatment for experimental group and10 nonnative-nonnative dyads using traditional face-to-face interaction for the control group. Ten topics were assigned to both groups and the research lasted about 10 weeks. Data collected from the two groups in Weeks 2, Week 6 and Week 10 were transcribed, coded and analyzed in terms of linguistic fluency, accuracy and complexity using doubly multivariate repeated measures of ANOVA for the statistic analysis. Follow-up questionnaires with both groups and online interviews with five of the participants in the experimental group were also conducted.The results indicated that there was a significant improvement in fluency, a slightly significant improvement in accuracy, but no improvement in complexity for the L2 learners in the experimental group. Interactional mode has a significant effect on L2 learners’ language proficiency. Using Internet-based desktop videoconferencing to talk with native speakers resulted in better performance by the participants in the experimental group than those in the control group in terms of fluency, accuracy and complexity. There was a significant interaction effect of time by interactional mode in terms of fluency, but no interaction effects were detected in terms of accuracy and complexity.Results from the participants’ follow-up questionnaires and interviews indicated that the Internet-based desktop videoconferencing creates a comfortable, spontaneous and less threatening environment for L2 learners to interact with native speakers. L2 learners have perceived great improvement in their language proficiency in terms of fluency and accuracy. Pedagogical implications, limitations of the study and recommendations for future research were also provided. Advisors/Committee Members: Franklin, Teresa J.

Subjects: Education, Curriculum and Instruction; Language, Linguistics

Keywords: Internet-based desktop videoconferencing; Second Language acquisition; fluency; accuracy; complexity; language proficiency

18. Xiao, Rui. Activation and regulation of TRP channels.

Degree: PhD, Biophysics, 2008, Ohio State University

► Mammalian TRP superfamily is composed of 28 members. Based on the sequence… (more)

▼ Mammalian TRP superfamily is composed of 28 members. Based on the sequence homology and functional similarity, they are grouped into 6 subfamilies: canonical TRP (TRPC), vanilloid TRP (TRPV), melastatin TRP (TRPM), ankyrin TRP (TRPA), polycystin TRP (TRPP), and mucolipin TRP (TRPML). TRP channels display rather diverse tissue expression pattern and physiological functions.We mainly focused on three TRP channels: TRPV3 from TRPV subfamily; TRPC4 and TRPC5 from TRPC subfamily. For TRPV3, we performed three functional studies: first, we found that arachidonic acid (AA), together with other poly-unsaturated fatty acids (PUFAs), greatly potentiated TRPV3 channel function independent of its downstream metabolites or signaling pathways. Second, besides being potentiated by AA and other PUFAs, TRPV3 also displays an intrinsic unique functional property: sensitization upon prolonged or repetitive chemical or physical stimulations. We studied the molecular mechanism underlying this unique feature and found that calcium plays a critical role from both intracellular and extracellular sides. Third, a spontaneously occurring point mutation linked to rodent hair-less phenotype was mapped to Gly573 of TRPV3. We carried out detailed functional studies with G573C and G573S mutants of TRPV3, and discovered that these two point mutations cause constitutive channel activation and severe host cell death, which provides an important clue for the hairless phenotype. Moreover, we studied the activation mechanism of TRPC4 and TRPC5. Strikingly, we found that in addition to the previously identified Gq/11 signaling pathway, another commonly considered inhibitory G protein-coupled receptor, Gi/o signaling pathway, was excitatory for the activation of TRPC4 and TRPC5. In fact, compared to Gq/11, the Gi/o pathway was even stronger for the activator of TRPC4/C5. We also demonstrated the synergistic effect between these two pathways. The full activation of TRPC4/C5 appeared to require both signaling pathways, indicating that TRPC4 and TRPC5 work as coincident detectors for the two important G protein signaling pathways. We further confirmed the requirement of phospholipase C (PLC) and intracellular Ca2+ for the excitatory effect of Gi/o. More detailed studies will help us understand the precise underlying mechanism of Gi/o-induced TRPC4/C5 activation. Advisors/Committee Members: Zhu, Michael.

Subjects: Biophysics

Keywords: TRPV3; TRPC4; TRPC5; sensitization; PUFAs; Ca2+; Gq/11; Gi/o

19. Xiao, Ruiyang. The Freezing of Highly Sub-cooled H2O/D2O Droplets.

Degree: MS, Environmental Science, 2008, Ohio State University

► The condensation of H2O and D2O in a supersonic Laval nozzle was… (more)

Subjects: Chemistry

Keywords: sub-cooled droplets; FTIR; supersonic nozzle

20. Xiao, Ruiyang. Sonochemical Degradation of Pharmaceuticals and Personal Care Products.

Degree: PhD, Civil Engineering, 2012, Ohio State University

► The widespread use of pharmaceuticals and personal care products (PPCPs) has raised… (more)

▼ The widespread use of pharmaceuticals and personal care products (PPCPs) has raised environmental concerns due to their presence in aquatic environments, unknown chronic low-dose exposure to humans, and recalcitrance to conventional water treatment technologies. In this dissertation, ultrasound, especially in pulsed wave (PW) mode has been explored to remove PPCPs. The focus was to fundamentally and mechanistically understand how ultrasound degrades PPCPs and what controls degradation kinetics. First, ultrasound was employed to degrade the pharmaceuticals, ciprofloxacin (CIPRO) and ibuprofen (IBU), in the presence of Suwannee River fulvic acid (SRFA) and terephthalic acid (TA) to gain an understanding of the effect of environmentally relevant matrix organics on degradation kinetics. The matrix organics inhibited the sonolysis of CIPRO and IBU to different extents. Based on the results, SRFA stays in bulk solution, either quenching •OH and/or associating with the target compounds. Similar to SRFA, TA, a commonly used •OH scavenger, reacts with •OH in the bulk region but we also suspect it accumulates on or interacts with cavitation bubbles. The indication has caused us to reexamine the validity that TA can be used as a bulk •OH scavenger, because a flawed bulk •OH scavenger not only misestimates the contribution of •OH in bulk solution to the overall contaminant degradation, but also misrepresents the nature of the reaction in the aqueous cavitational systems. By using PW ultrasound we evaluated the performance of different •OH scavengers (i.e., formic acid (FA), carbonic acid (CA), terephthalic acid (TA)/terephthalate (TPA), potassium iodide (KI), methanesulfonate (MS), benzenesulfonate (BS), and acetic acid (AA)/acetate) to determine the performance of •OH scavengers. The degradation of carbamazepine (CBZ), a probe compound serving as the reference compound occurred primarily at bubble-water interface in the study. Based on the pulsed enhancement (PE) of CBZ, acetic acid/acetate appears to scavenge •OH in bulk solution, and not interact with cavitation bubbles. For formic acid, carbonic acid, terephthalic acid/terephthalate, benzenesulfonate, and iodide, the PE was significantly decreased compared to in the absence of the scavenger. These scavengers not only quench •OH in bulk solution but also affect the cavity interface. To apply the knowledge of AA as a bulk •OH scavenger, seven PPCPs, namely CBZ, IBU, CIPRO, acetaminophen (ATP), sulfamethoxazole (SFT), propyl gallate (PG), and diethyl phthalate (DP) were degraded by ultrasound. Degradation rates by PW ultrasound were compound dependent with degradation either faster for smaller compounds or slower for larger compounds than that under CW ultrasound. To investigate the discrepancy of degradation rate of the PPCPs between CW and PW ultrasound, AA was added and irradiated with each compound to differentiate the contribution of bulk •OH oxidation in its overall degradation. The results showed that the fraction of degradation occurring in bulk solution is positively correlated with the molar volume of the compound. Smaller PPCP compounds are able to more readily diffuse to bubble interfaces and are impacted most by pulsing ultrasound. Our results suggest PW ultrasound improves the energy efficiency of ultrasound as a treatment technology for small size PPCPs. Advisors/Committee Members: Weavers, Linda.

Subjects: Environmental Engineering

Keywords: PPCPs; ultrasound; pulse enhancement; scavenger; molecular size; hydrophobicity

21. Xiao, Xiao. Promoting Conservation Subdivision Development in Sprawl Areas - A framework of formulating local government strategies.

Degree: MCP, Design, Architecture, Art and Planning : Community Planning, 2010, University of Cincinnati

► Sprawl creates a series of social and environmental issues, such as increasing… (more)

▼ Sprawl creates a series of social and environmental issues, such as increasing pollution, increasing traffic and traffic-related fatalities, decreasing land and water quantity and quality, and increasing infrastructure costs. However, as the population grows and the need of residential development grows, sprawl would continue in the future. Local governments in the sprawl areas, thus, are seeking land use planning strategies to eliminate sprawl problems.Conservation subdivision development (CSD), a relatively new development tool, emerged about two decades ago, is trying to balance the demand of land development and the conservation of environment, ecosystems, farmland and cultural and historical features. It could reduce the sprawl problems by clustering the development on the relatively small portion of the site, and leaving major portion of the site as conservation areas. This study uses marketing concept in business field to help local government to promote CSD. The study provides a framework for local governments to formulate CSD promotion strategies based on the situations that local government are facing, analysis of the characteristics and needs of developers (the suppliers of CSDs) and residentshomeowners (the consumers of CSDs), analysis of benefits and barriers of applying CSD approach, and the conservation objectives and goals; and then prepare time schedule for the implementation of CSD promotion strategies and monitor the outcomes of the strategies to adjust and update the strategies for better result. The framework is demonstrated with a hypothetical case study. It requires knowledgeable staff and careful research to formulate strategies to promote CSDs. The lack of knowledgeable staff and careful research would reduce the effectiveness of these promotion strategies. In addition, the CSD approach is still relatively new compared with prevailed conventional development in residential development industry. It needs time and afford to achieve the wide rang implementation of CSD approach. Advisors/Committee Members: Wang, Xinhao.

Subjects: Urban planning

Keywords: Conservation Subdivision Development; Open Space; Marketing; Marketing Plan; Promoting; Strategies

22. Xiao, Xiaosui. China encounters Western ideas (1895-1905): a rhetorical analysis of Yan Fu, Tan Sitong and Liang Qichao.

Degree: PhD, Communication, 1992, Ohio State University

Advisors/Committee Members: Foss, Sonja K.

23. Xiao, Ying. A Two-dimensional Stochastic Model for Prediction of Localized Corrosion.

Degree: MS, Chemical Engineering (Engineering), 2004, Ohio University

► The two-dimensional (2-D) stochastic model, which describes the balance of two processes:… (more)

Keywords: Localized Corrosion; Modeling; Stochastic; Film; Carbon Steel; Prediction

24. Xiao, Zhigang. Synthesis of Functional Multilayer Coatings by Plasma Enhanced Chemical Vapor Deposition.

Degree: PhD, Engineering : Electrical Engineering, 2004, University of Cincinnati

► Silicon dioxide, silicon-containing polymer, silicon nitride, metal nitride, and germanium thin films… (more)

▼ Silicon dioxide, silicon-containing polymer, silicon nitride, metal nitride, and germanium thin films were grown by electron cyclotron resonance (ECR) microwave plasma enhanced chemical vapor deposition (PECVD), and multilayer coatings were grown for high hardness and high corrosion resistance. Silicon dioxide was grown from hexamethyldisiloxane (HMDSO), 1,3,5,7-tetramethylcyclotetrasiloxane (TOMCTS ), and octamethylcyclotetrasiloxance (OMCTS) in a oxygen plasma. The grown silicon dioxide thin films were hard and colorless. Silicon nitride was grown from hexamethyldisiloxane (HMDSO) and tetramethylsilane (TMS) in an ammonia (NH3) plasma. The silicon nitride thin films grown from HMDSO were hard and transparent while the silicon nitride thin films grown from TMS were black and hard. Silicon-containing polymer was grown from 100% OMCTS. The polymer thin films are colorless, had relatively low hardness and very good salt-fog corrosion resistance. Titanium nitride, zirconium nitride, and chromium nitride were grown from titanium (IV) isopropoxide and tetrakis(dimethylamino)titanium, zirconium 2-methyl-2-butoxide and zirconium t-butoxide, and bis(ethylbenzene)chromium in an ammonia plasma. The grown titanium nitride and zirconium nitride thin films had characteristic gold coloring and high hardness while the grown chromium nitride thin films were black gray and had high hardness. Germanium thin films were grown from tetramethylgermane (TMG) in a argon plasma. The deposited germanium films were uniform and had polished-like shining surface. X-ray photoelectron spectroscopic (XPS) analyses showed the films contained 97 % germanium atomic concentration with less than 1 % carbon, and X-ray diffraction (XRD) analyses showed the films had the crystal structure of <220>. Hard corrosion-resistant silicon-containing multilayer coatings were grown in a high-density microwave electron cyclotron resonance discharge. The multilayer coatings consist of a relatively soft silicon-containing polymer thin film as the bottom layer and a hard silicon dioxide or silicon nitride thin film as the top layer. Silicon-containing polymer thin films were grown from 100% OMCTS. Silicon dioxide and silicon nitride thin films were grown from OMCTS with O2 and HMDSO with NH3, respectively. The multilayer structures combined high surface hardnesses with good corrosion resistance, surviving 1800 to 2600 hours in an ASTM B117 salt-fog corrosion test. Multilayer coatings with a titanium nitride or zirconium nitride bottom layer and a transparent silicon-containing polymer or silicon dioxide top layer were grown in a high-density microwave electron cyclotron resonance discharge for protective or decorative coating application. The grown multilayer coatings had gold coloring and good film thickness. Advisors/Committee Members: Mantei, Dr. Thomas.

Keywords: PECVD, ECR, Multilayer Coating, Silicon Dioxide, Silicon Nitride, Silicon-Containing Polymer, TiN Thin Film, ZrN Thin Films, CrN Thin Films, Ge Thin Film, ASTM B117, and DLI

25. Xia, Ping. Adhesive functions in fibronectin's alternatively-spliced ED(a) segment.

Degree: PhD, Molecular Biology and Microbiology, 1996, Case Western Reserve University

► EDa (EIIIA) is an alternatively-spliced type III homology repeat present in cellular… (more)

▼ EDa (EIIIA) is an alternatively-spliced type III homology repeat present in cellular fibronectins (cFNs) but not in plasma fibronectin (pFN). Potential adhesion-promoting activity was investigated for EDa and its two neighboring repeats III11 and III12. Recombinant protein corresponding to EDa alone promoted Balb/c 3T3 cell attachment, as did neighboring repeats III11 and III12 when tested as single repeats. Activities were even higher for recombinant proteins containing two or three repeats. While EDa alone exhibited 40-60% of the attachment activity of human pFN depending upon cell type, EDa with both neighboring repeats displayed 70-90% of pFN activity. Besides attachment, the recombinant substrata also supported limited cell spreading. 3T3 cells on the EDa substratum displayed round cell bodies with filopodia contacting the substratum. Cells on III11-EDa-III12 displayed spindle-shaped cell bodies and pseudopods in contact with the substratum. The two-repeat molecule of III11-III12 gave an intermediate response. Moreover, adhesion activities towards these recombinant proteins were oncogene-regulated: comple tely abrogated by two different ras oncogenes, unaffected by the sis oncogene, and elevated by the src oncogene aFunctional complementarity was noted between EDa recombinant molecule and pFN. Co-coating substrata with EDa and a suboptimal concentration of pFN led to increased attachment and extensive spreading of v-src-transformed 3T3 cells relative to that found on substrata of suboptimal pFN or EDa alone. This complementarity requires as little as 1 μg/ml EDa in the adsorbing mixture and displays sequence specificity for only EDa (i.e., III11 or III12 was without effect.). Furthermore, stress fibers and focal contacts were inducible on the EDa:PFN mixture, suggesting the full adhesion-promoting competence of the heterologous substrata aSynergy in promoting post-attachment adhesion responses among III11, EDa and III12 was also observed. This conclusion is supported by two lines of evidence: (a) spreading on two-repeat molecules was better than spreading on single-repeat molecules, and (b) only the three-repeat molecule was competent for inducing stress fibers and focal adhesions. Experimental evidence indicated that glycosaminoglycans did not participate in these adhesion processes; neither did β1-containing integrins. Affinity chromatography was employed to isolate the putative receptor(s) to no avail. These studies reveal a new adhesion promoting activity in fibronectin molecules whose function is more effectively presented by cFNs than pFN, which may indicate the advantage of cFNs in various physiological and pathological conditions where expression of EDa sequence is elevated. Advisors/Committee Members: Culp, Lloyd A.

Subjects: Biology, Cell

Keywords: Fibronectin's alternatively-spliced ED(a) segment

26. Xia, Qing. Online Monitoring of Aerobic Denitrification of Pseudomonas Aeruginosa by NAD(P)H Fluorescence.

Degree: MS, Chemical Engineering, 2006, University of Akron

► In cystic fibrosis airway infection, Pseudomonas aeruginosa forms microaerobic biofilm and undergoes… (more)

▼ In cystic fibrosis airway infection, Pseudomonas aeruginosa forms microaerobic biofilm and undergoes significant physiological changes. It is important to understand the bacterium’s metabolism at microaerobic conditions. Continuous cultures of P. aeruginosa (ATCC 9027) maintained at different dissolved oxygen concentrations (DO) and three different dilution rates (D) were studied for the effects of DO and D on various culture properties, especially on aerobic respiration and denitrification. The DO was varied from 0 mg/L (completely anoxic condition) to 2.2 mg/L, and measured with optical sensors that could accurately determine very low DO based on oxygen-quenched luminescence. The studied dilution rates were 0.026 h-1, 0.06 h-1 and 0.13 h-1. The strain was found to perform aerobic denitrification; while the specific nitrate and nitrite reduction rates decreased with increasing DO, denitrification persisted even at relatively high DO levels (1-2.2 mg/L) at different D. In the presence of nitrate, the Monod constant for DO (i.e., the critical DO at which the specific oxygen uptake rate (OUR) is half of the maximum rate) was practically zero (< 0.001 mg/L) for this P. aeruginosa strain. Aerobic denitrification appeared to function as an electron-accepting mechanism supplementary or competitive to aerobic respiration. The shift of culture’s respiratory mechanism was also clearly detected with a fluorometer targeting at intracellular NAD(P)H, i.e., the reduced coenzymes nicotinamide adenine dinucleotides (phosphate). Comparatively, the NAD(P)H fluorescence was highest at the anoxic, denitrifying condition (NFUDN), lowest at fully aerobic conditions (NFUOX), and intermediate fluorescence (NFU) at conditions where both denitrification and aerobic respiration occurred. Representing a quantitative measure of the culture’s “fractional approach” to the fully denitrifying state, the normalized fractions (NFU - NFUOX)/(NFUDN - NFUOX) were correlated with the calculated fractions of electrons accepted by denitrification. The denitrification-accepted fractions of electrons increased with the NFU fractions: the increases were gradual at larger DO levels (DO ≥ d 0.1 mg/L), but much sharper at lower DO at three different dilution rates. The fluorescence fraction changed more rapidly than the electron fraction at very low DO levels (< 0.001 mg/L). The results demonstrated that online NAD(P)H fluorescence was a feasible technique for effective monitoring and quantitative description of the microaerobic state of microorganisms. Advisors/Committee Members: Ju, Lu-Kwang.

Keywords: Rhamnolipid; AERUGINOSA; DENITRIFICATION; NAD; FLUORESCENCE; AEROBIC; Continuous cultures

27. Xia, Shijing. Experimental and Computational Studies for Various Organic Systems.

Degree: PhD, Chemistry, 2008, Ohio State University

► The electronic properties and the thermodynamic preferences for O2 addition to various… (more)

▼ The electronic properties and the thermodynamic preferences for O2 addition to various tetrathiatriarylmethyl (TAM)-type triarylmethyl (trityl) radicals were experimentally and theoretically investigated. The radicals' stability in the presence of O2 and biological milieu was also experimentally assessed. Results showed that H substitution on the aromatic ring affects the trityl radical's stability and may lead to substitution reactions in cellular systems. We proposed that this degradation process involves an arylperoxyl radical that can further decompose to alcohol or quinone products. Computational approaches were also being used to search for spin probes with improved stability and enhanced chemical and biological properties.A signature absorbance at 392 nm, which is generated from acetonitrile solutions of N-hydroxypyridin-2-thione in the presence of trans-stilbene, was used in competitive laser flash photolysis (LFP) experiments to determine rate constants of reactions for hydroxyl radical with sixteen different benzene derivatives. Structure-reactivity relationships for these reactions were derived. Computational studies were employed to reveal the details of these reactions. The tautomerism and photochemistry of N-hydroxypyridones (NHPs) and N-hydroxy-pyridinethiones (NHPTs) were also studied theoretically in order to find some potential radical precursors or probes for hydroxyl radical reactions with aromatics. To avoid the problems typically encountered in the measurement of rate constants of superoxide radical trapping by nitrones, a more straightforward approach, stopped-flow UV methodology, has been developed by using KO2 as a direct source of superoxide radical. The absolute rate constants for the reactions of superoxide radical anion with five different spin traps were measured experimentally. The conformational and IR spectroscopic studies of several novel capsules were studied computationally. The theoretical data rationalized the experimental results, and demonstrated, along with experimental data, that these compounds have a tendency to associate intramolecularly. The conformational dynamics and thermodynamics of a series of monovalent ureas, the synthetic divalent urea and its dimer were computationally studied using the B3LYP/6-31+G** level of theory which was validated to be a suitable method to study this system. Theoretical studies were also employed to study the radical-addition reactions of benzene with 13 radicals as well as regio- and diastereo-selectivity in the dimethyl dioxirane (DMDO) mediated epoxidation of carbohydrate-based oxepines. Advisors/Committee Members: Hadad, Christopher.

Subjects: Chemistry

Keywords: computational; experimental; radical; trityl; hydroxyl; superoxide; oxepine; urea; capsule

28. Xia, Xinggao. Modeling A Microfluidic Capacitive Sensor for Metal Wear Debris Detection in Lubrication Oil.

Degree: MS, Electrical Engineering, 2009, University of Akron

► This thesis presents a model of a MEMS capacitive sensor for wear… (more)

Subjects: Electrical engineering; Mechanical engineering

Keywords: Microfluidic; Capacitive Sensor; Modeling; Metal Wear Debris Detection; Finite Element Simulation

29. Xia, Yining. Farrell-Tate cohomology of the mapping class group.

Degree: PhD, Mathematics, 1990, Ohio State University

Advisors/Committee Members: Glover, Henry.

30. Xie, Chao. Singularities in the Unphysical Complex Plane for Deep Water Waves.

Degree: PhD, Mathematics, 2009, Ohio State University

► Two-dimensional free surface flows may be formulated through boundary integrals which allows… (more)

▼ Two-dimensional free surface flows may be formulated through boundary integrals which allows analytic continuation in the unphysical complex plane. For two dimensional water waves, Tanveer showed that the only form of singularity in the unphysical plane is of the square-root type. One may wonder what influence these singularities may have on the behavior of water waves. This thesis resolves some of these questions by tracking singularities in the unphysical domain and relating their close approach to the real axis with wave breaking.The main result is the direct verification of Tanveer’s singularity result. A boundary integral technique is used to simulate deep water wave motion. A spectral procedure is used to form-fit the Fourier spectrum of the curvature of the wave profile to a prescribed asymptotic expression. The form-fit provides information on the power and location of the closest singularity to the real axis. The power of the curvature singularities is found to be -3/2 when the curvature is expressed as a function of the Lagrangian variable. This singularity is associated with a pole singularity in the complex arclength plane, and is not an artifact of the parametrization. The singularity approaches the real axis when a plunging breaker occurs. For nonbreaking waves, the singularity wanders above some level in the unphysical plane. It is then established that this curvature singularity is theoretically equivalent to Tanveer’s one-half power singularity. When the surface elevation is viewed as a function of horizontal distance, a different type of singularity arises. It is a square root type singularity that takes the form of a breaking wave when it reaches the real axis of the horizontal coordinate. Nonlinear interactions among various wavelengths are considered important in random ocean waves. A particularly important nonlinear interaction is the Benjamin-Feir instability. For moderate initial amplitudes, the end-state of this instability is either wave breaking or the Fermi-Pasta-Ulam recurrence. Clearly, singularities in the unphysical domain will play a role. Starting with initial conditions that contain several singularities away from the real axis, their trajectories are studied. When breaking occurs, results show that it is one of the crests in the wave train that breaks like a plunging breaker while others remain moderately flat. One of the singularities moves close to the real axis while the other singularities stay far away. When recurrence occurs, evidence indicates that the closest singularity remains far away from the real axis for all time. The hope and the possibility is that a study of singularities in Benjamin-Feir instability may lead to insight into nonlinear wave interactions in general. Advisors/Committee Members: Baker, Gregory R.

Subjects: Fluid dynamics; Mathematics

Keywords: singularities; unphysical complex plane; water waves

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