Doctor of Philosophy

dissertationSocial learning is an important part of consumers' lives. A major limitation of previous research in consumer social learning is the lack of attention to the effects of relationships built among participants on the learning process in online communities. Within a thread in an online forum, when a post is made referring to a previous post, a connection is built between the posts, indicating the opportunity for the continuation of the learning process. We construct a conceptual framework of reference relationships in ongoing threads. We propose that four key constructs related to the reference relationships between posts are associated with the continuation of the social learning process within threads, including engagement, sociality, advanced levels of learning, and existence and strength of ties between posters. We investigated 19 threads with 580 posts in a diabetes online community using both qualitative and quantitative analysis. Results provide substantial evidence that reference relationships in an ongoing thread are significantly positively associated with posters' engagement in the community and in the ongoing thread, advanced learning steps and sociality demonstrated in the content of posts in the ongoing thread, and ties in other threads. Our study suggests important implications for marketers in facilitating consumers' social learning process in online communities. Specifically, we suggest that by investigating posts made in reference relationships, marketers may identify the topics in which posters have interest and the influentials who disseminate and generate knowledge in online communities

Topological Band Theory for Non-Hermitian Hamiltonians

We develop the topological band theory for systems described by non-Hermitian Hamiltonians, whose energy spectra are generally complex. After generalizing the notion of gapped band structures to the non-Hermitian case, we classify "gapped" bands in one and two dimensions by explicitly finding their topological invariants. We find nontrivial generalizations of the Chern number in two dimensions, and a new classification in one dimension, whose topology is determined by the energy dispersion rather than the energy eigenstates. We then study the bulk-edge correspondence and the topological phase transition in two dimensions. Different from the Hermitian case, the transition generically involves an extended intermediate phase with complex-energy band degeneracies at isolated "exceptional points" in momentum space. We also systematically classify all types of band degeneracies.Comment: 6 pages, 3 figures + 6 pages of supplemental materia

Low Transmission to Elimination: Rural Development as a Key Determinant of the End-Game Dynamics of Schistosoma japonicum in China.

Rural development has been a critical component of China's economic miracle since the start of economic reform in the early 1980s, both benefiting from and contributing to the nation's rapid economic growth. This development has yielded substantial improvements of public health relevance, including contributing to major reductions in schistosomiasis prevalence. The history of schistosomiasis elimination in Japan suggests that development played a dominant causal role in that nation. We argue that it is highly probable that a similar story is playing out in at least some large regions of China. In particular, we summarize evidence from Sichuan Province which supports the case that economic development has led to improvements in rural irrigation and water supply which, together with changes in crop selection and agricultural mechanization, have all contributed to sustainable reductions in the prevalence of Schistosoma japonicum. The two major factors that have experienced major reductions are the area of snail habitat and the degree of human exposure, both through a variety of mechanisms which differ by region and economic circumstance. However, hotspots of transmission remain. Overall, however, economic development in traditionally endemic areas has provided the resources to carry out projects that have had major beneficial impacts on disease transmission that are likely to be sustainable

Regulation of BK virus DNA replication by transcription factors and noncoding RNAs

"May 2011"The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Title from PDF of title page (University of Missouri--Columbia, viewed on May 17, 2012).Thesis advisor: Dr. William R. FolkVita.Human polyomavirus BK (BKV) asymptomatically infects 80[about]90% of people during early childhood, and establishes a life-long persistent infection without causing overt clinical symptoms. High level BKV replication occurs predominantly in urogenital tracts of immune-suppressed patients following renal transplantation and bone marrow transplantation, which cause polyomavirus associated nephropathy (PVAN) and hemorrhagic cystitis, respectively. PVAN has become a leading cause for renal transplantation failures since tacrolimus and mycophenolate mofetil began to be widely used in transplantation patients in 1995. Epidemiological studies indicate that around 30% of kidney transplantation patients are at risk of developing PVAN and 50% of PVAN patients are at risk of transplantation failure. This dissertation explores the mechanisms by which the genomic noncoding control region (NCCR) regulates BKV DNA replication in cell culture and might be related to the establishment of BKV persistent infection and pathogenesis of PVAN. These studies indicate that cellular transcription factor NFI interacts with the BKV NCCR and stimulates BKV DNA replication in vivo and in vitro. Also, the data reveal that isotypes NFIA and NFIB strongly interact with BKV large T antigen (Tag) and NFIC interacts with DNA polymerase-[alpha] primase (pol-[alpha]primase), suggesting NFI-family transcription factors may stimulate BKV DNA replication through recruitment of Tag and pol-[alpha] primase. In contrast, ectopic expression of PCAF/GCN5 histone acetyltransferases inhibit BKV DNA replication. Tag has a site for acetylation by PCAF/GCN5, but inhibition of BKV DNA replication by PCAF/GCN5 is not due to acetylation of Tag, suggesting PCAF/GCN5 target other component(s) of DNA replication machinery. Possible targets include nucleosomes associated with the NCCR and other components of the replication machinery. A search for these targets is proposed, and possible functions of acetylation on BKV Tag are discussed. BKV DNA does not replicate in murine cells. We and our collaborators have found that this host-restriction of BKV DNA replication involves not only incompatibility of BKV Tag with mouse pol-[alpha]primase, but also inhibitory small noncoding RNAs in murine cells, termed srRNAs, that act through BKV NCCR. Specific srRNAs were sequenced and cloned. In vitro transcribed srRNAs inhibit BKV replication in vitro; and ectopic expression of a specific srRNA strongly inhibits BKV DNA replication in vivo in human cells. Surprisingly, srRNAs from human cancer cells stimulate BKV DNA replication in vitro, suggesting cell type specific expression of srRNAs has distinct role in regulation of BKV DNA replication. We propose that differential expression of srRNAs may have implication in the viral tropism, establishment of persistent infection and reactivation.Includes bibliographical reference

Z_3 Symmetry and Neutrino Mixing in Type II Seesaw

Neutrino mixing matrix satisfying the current experimental data can be well described by the HPS tri-bimaximal mixing matrix. We propose that its origin can be understood within the seesaw framework by a hidden condition on the mass matrix of heavy right-handed neutrinos under the transformation of the Abelian finite group Z_3 on the flavor basis. Ignoring CP phases, we show that it can lead to the generic form of the effective light neutrino mass matrix from which the HPS mixing matrix appears naturally, as well as an expeimentally allowed non-zero \sin\theta_{13}. We show that the model based on our proposal is in good agreement with the current experimental data.Comment: 9 page

Analysis of the Chinese provincial air transportation network

The air transportation system is of a great impact on the economy and globalization of a country. In this paper, we analyze the Chinese air transportation network (ATN) from a provincial perspective via the complex network framework, where all airports located in one province are abstracted as a single node and flights between two provinces are denoted by a link. The results show that the network exhibits small-world property, homogeneous structure and disassortative mixing. The variation of the flight flow within 24 h is investigated and an obvious tide phenomenon is found in the dynamics of Chinese provincial ATN for high output level of tertiary industry. Our work will offer a novel approach for understanding the characteristic of the Chinese air transportation network.Peer ReviewedPostprint (author's final draft