published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Linguistics / Master / Master of Arts in Applied Linguistics

published_or_final_version / abstract / Computer Science / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Linguistics / Master / Master of Arts

published_or_final_version / Linguistics / Master / Master of Arts in Applied Linguistics

This dissertation considers repetition phenomena in Hindi-English bilingual discourse. Through analysis of everyday Hindi-English conversations, I demonstrate that code-switching and related bilingual phenomena systematically expand options bilingual speakers have for structuring discourse, managing interactions, and making linguistic and social meaning. The systematicity and strategy of Hindi-English code-switching are particularly apparent in what I term bilingual repetition. In bilingual repetition, the semantic content of an utterance in one language is repeated in another language, usually in close proximity to the first occurrence. Bilingual repetition is encountered throughout South Asian multilingual contexts ranging from casual conversations to printed advertisements to Bollywood dialogues. I also consider repetition as a discourse-level areal feature of South Asia. Both monolingual and bilingual repetition phenomena offer an opportunity to investigate alternatives for making meaning both within and across languages due to the side-by-side presentation of semantically and formally related messages. Ultimately, code-switching and repetition in Hindi-English bilingual discourse emerge as practices that both create and reflect linguistic and social simultaneity. / text

This study casts the code-switching patterns observed among Spanish-English bilinguals in Bayside, Texas within the framework of Bell’s (1984) theory of audience design, which is claimed to apply to both monolingual style-shifting as well as bilingual code-switching. The latter part of this claim has been little explored. The intent of this study, then, is to determine if the explanatory power of audience design, as demon¬strated in studies on style-shifting, does indeed hold when applied to cases of language alternation. Analysis of the data from Bayside generally supports Bell’s theory as it shows speakers adjusting their use of Spanish and/or English to suit their audience. The study will highlight a less frequently analyzed aspect of Bell’s model, i.e., the role of the auditor, and will call for the auditor to be classified as a primary influencer of lin¬guistic choice in bilingual contexts, alongside the addressee. The code selection patterns exhibited by a pair of Bayside residents in a series of interviews and in conversations videotaped at the local general store will be com¬pared to illustrate the effects of addressee and auditor. A qualitative analysis will dem¬onstrate that differing determinations regarding the linguistic repertoires of the auditors led to contrasting linguistic choices on the part of the study’s subjects. The data collected will show that, when selecting a language of communication, as opposed to a register, style, or dialect, a speaker may be more greatly affected by an auditor than by the addressee. The methods used in collecting the data will also support an expan¬sion of Bell’s model to include an additional participant category suitable for capturing the effect of the recording device, as per Wertheim (2006). / text

RNA recombination is a major factor driving viral evolution and contributing to new disease outbreaks. Therefore, understanding the mechanism of RNA recombination can help scientists to develop longer lasting antiviral strategies. Tombusviruses are one of the best model RNA viruses to study RNA virus recombination. My goals were to dissect the mechanism of tombusviral RNA recombination. To do so, in my thesis, I describe my results on the roles of (i) the viral replicase and the viral RNA templates; and (ii) the effect of host factors on tombusvirus recombination events. To study the mechanism of RNA recombination without the influence of selection pressure on the emerging recombinants, we developed an in vitro RNA recombination assay based on viral RNA templates and purified viral replicase preparations. Using this in vitro assay, we demonstrated that replicase driven template switching is the mechanism of recombination, whereas RNA ligation seems less likely to be a major mechanism. In addition, we also studied the role of RNA substrates, in more detail. Our results showed that viral replicase preferred to use functional RNA domains in the acceptor RNAs over random switching events. Host factors may also play important roles in RNA recombination. Using yeast as a model system for studying replication and recombination of a tombusvirus replicon, we identified 9 host genes affecting tombusvirus RNA recombination. Separate deletion of five of these genes enhanced generation of novel viral RNA recombinants. Further studies on one of these genes, XRN1, a 5-3 exoribonuclease, indicated that it might be involved in degradation of tombusvirus RNAs. Lack of Xrn1p resulted in accumulation of truncated (partially degraded) replicon RNAs, which became good templates for RNA recombination. To further study Xrn1p, we overexpressed Xrn4p of Arabidopsis thaliana, a functional analogue of the yeast Xrn1p, in Nicotiana benthamiana plants. After superinfecting the Xrn4p-overexpressing N. benthamiana with tombusvirus, truncated tombusvirus genomic and subgenomic RNA1 were observed. Some of the identified tombusvirus variants were infectious in protoplasts and could systemically infected N. benthamiana plants. Overall, this is the first report that a single host gene can affect rapid viral evolution and RNA recombination.

This thesis is devoted to the analysis of problems that arise when long products of matrices taken in a given set are constructed. A typical application is the stability of switched linear systems. The stability of a discrete-time linear system is a classical engineering problem that has been well understood for long: the dynamics can be expressed in terms of the eigenvalues of the matrix ruling the system. A more complicated problem arises when the dynamical system can switch, that is, if the matrix changes over time. If this matrix is taken from a given set but can be chosen arbitrarily in this set at every time, the stability problem turns to the computation of a quantity, the joint spectral radius of the set of matrices, introduced in the early sixties. While this quantity appears to be hard to compute, it has acquired more and more importance during the last decades, and new applications of the joint spectral radius in engineering or mathematics are frequently discovered. It has for instance been proved useful for the analysis of regularity of fractals, for the continuity of wavelets, or for autonomous agents detection in sensor networks. In the first part of this thesis, we present a theoretical survey of the joint spectral radius, including old and new results. The joint spectral subradius, which is its stabilizability counterpart, is also considered. In a second part, we study some applications related to long products of matrices. We first analyse in detail a problem in coding theory, that has been recently shown to involve a joint spectral radius computation. We then propose a new application of the joint spectral radius (and related quantities) to a classical problem in number theory, namely the counting of overlap-free words. We then turn to problems related with autonomous agents detection: we analyse the trackability of sensor networks, and introduce and analyse a new notion, namely the observability of sensor networks.