Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 82-84). Also available in electronic version. Access restricted to campus users.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Bras, Bert; Committee Member: Jeter, Sheldon; Committee Member: McGinnis, Leon. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Organic π-conjugated molecules and materials with large real parts and small imaginary parts of the third-order polarizability are of great interest for all-optical switching applications. In this dissertation, we use quantum-chemical and molecular-dynamics approaches to investigate the structure-property relationships that influence the nonlinear optical properties of π-conjugated molecules and materials. We begin with an overview of nonlinear optics, focusing in particular on the electronic properties of linear π-conjugated systems and some of the important problems that have limited device applications of these molecules to date. This is followed by a brief review of the computational methods employed in these studies. We then turn to the main results of the dissertation. Chapter 3 describes the structural dependence of the transition dipole moment between the first two polymethine excited states. Chapter 4 discusses the relationship between BLA, which depends on the geometric structure, and BOA, which probes electronic structure. Chapter 5 describes the benchmarking of computational methods to describe the symmetry-breaking of long polymethines and preliminary evidence regarding the role of vibrational modes in symmetry-breaking. Chapter 6 explains the negative third-order polarizability of tetraphenylphosphate and analogous systems. Chapter 7 focuses on molecular-dynamics studies of polymethine aggregation, particularly the relationships between chemical structure and the geometric and electronic structures of aggregates. Finally, Chapter 8 provides a synopsis of the work and discussion of further directions.

The costs of acquiring parcels by condemnation are usually significantly higher than those for property acquired by negotiation, suggesting that Right-of-Way (R/W) acquisition costs may best be described by two different regression equations. This paper develops a switching regression model of acquisition cost to simultaneously predict the probability of whether a parcel will go to condemnation rather than be acquired via negotiation and the corresponding acquisition costs under these two regimes. The error terms of the selection equation and the two cost equations follow a trivariate normal distribution to reflect correlations across unobserved factors (such as a land owner's tenacity or a site's view value). When this model is calibrated using data on properties acquired across the state of Texas for transportation projects between 2008 and 2011, results suggest that R/W appraisers and staff should pay special attention to commercially used parcels in urban areas involving a partial taking with a relatively small remainder. Comparison of cost estimates between the two regimes (condemnation vs. negotiation) suggests that condemned parcels will have, on average, 78% higher acquisition costs across the 1,710 acquired properties and 51% greater price variation. These results suggest that it is much more costly to acquire a property and more difficult to accurately predict its costs if it cannot be acquired via negotiation. The application of model estimates to an example corridor highlights the value of simulation to capture all modeling uncertainties. This two-regime model is further extended to a three-category multinomial endogenous switching, allowing for differential cost estimates across negotiation-deed, administrative settlement, and condemnation contexts. A model of acquisition time -- from the agency's initial-offer date to its final possession date is also developed, to examine the effects of condemnation on acquisition duration. The results suggest that condemnation proceedings add approximately 7 to 8 months, on average, to parcel acquisitions by the Texas Department of Transportation. Taken together, such switching models for condemnation versus negotiated settlement highlight the benefits of avoiding condemnation proceedings in R/W acquisition. Estimation results illuminate the relative importance of various parcel and owner attributes, impacting the nature and cost of acquisition, and enhancing opportunities for R/W staff to identify more contentious properties and establish more reliable budget estimates. / text

Ranaviruses are large dsDNA viruses that are considered emerging pathogens, and they are known to cause mortality events in amphibian and fish populations. This research utilizes experimental and genomic data to elucidate the mechanisms driving the evolution and spread of ranaviruses, with a focus on host switching within the genus. In Chapter 1, we utilize virus challenge assays to examine potential transfer of ranaviruses between cultured juvenile largemouth bass (M. salmoides) and bullfrog tadpoles (Rana catesbeiana). Additionally, a commonly used antiparasitic treatment containing malachite green and formalin (MGF) was utilized to suppress the immune system of largemouth bass to assess the susceptibility of immunocompromised fish to ranaviruses. The results indicate that tadpoles are not susceptible to Largemouth Bass Virus (LMBV), but that bass are susceptible to ranaviruses isolated from amphibians. Furthermore, immunocompromised fish were more susceptible to both LMBV and FV3 infections than immunocompetent fish. In Chapter 2, we used eight sequenced ranavirus genomes and two selection-detection methods (site-based and branch-based) to identify genes that exhibited signatures of positive selection, potentially due to the selective pressures at play during host switching. We found evidence of positive selection acting on four genes via the site-based method, three of which are newly-acquired genes unique to ranavirus genomes. Our results suggest that the group of newly acquired genes in the ranavirus genome may have undergone recent adaptive changes that have facilitated interspecies and interclass host switching. In Chapter 3, we annotated and analyzed the nearly complete genomic sequence of LMBV to determine its taxonomic classification. The available genomic content and phylogenetic evidence suggests that LMBV is more closely related to amphibian-like ranaviruses (ALRVs) than grouper ranaviruses, and this is further supported by greater genomic collinearity between LMBV and ALRVs. This data suggests that the classification of LMBV as a ranavirus is warranted. The results presented here will help to clarify the taxonomic relationships of ranaviruses, and will also be useful in developing management strategies to limit interspecific and intraspecific viral spread. The information garnered from this research will have far-reaching implications in studies of amphibian conservation, disease evolution, and virology. / text

Purpose: This study examined the effects of conceptual scoring on vocabulary performance of bilingual children with and without language impairment and the classification accuracy of an expressive vocabulary test across four scoring methods, single language and conceptual scoring, for bilingual (English-Spanish) children with and without language impairment. Method: Participants included English speaking monolingual children (n=14) and Spanish-English bilingual children (n=116) ages 5-11. Children completed the English and bilingual versions of the Expressive One-Word Picture Vocabulary Test. Four different scores were derived representing monolingual scores in English and Spanish, and three conceptual scores. Within-test conceptual scores credited children’s other language responses during the test; and across-test conceptual scores compiled a conceptual score across Spanish and English administrations of the test. Results: Across-test conceptual scoring resulted in better overall classification, sensitivity, and specificity than within-test conceptual scoring, which resulted in better overall classification, sensitivity, and specificity than monolingual scoring; however, neither method achieved minimum standards of 80% accuracy in sensitivity and specificity. Conclusions: Results suggest that bilingual children are not always able to readily access their second language in confrontation naming tasks. Priming or inhibition may play a role in test performance. Cross-test conceptual scoring yielded the highest classification accuracy and is the recommended method for clinical practice. / text

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Linguistics / Master / Master of Philosophy

Not available / text

Este trabajo presenta los resultados de una investigación sobre el uso del inglés (la lengua materna de los estudiantes) por los profesores en la clase de segundo semestre de español a nivel de universidad. Los resultados mostraron que las profesoras escogían conscientemente la lengua que utilizaban así como cuándo y cómo la empleaban en clase. Parece que la experiencia de las profesoras como instructoras hacía que el inglés fuera menos usado por las que tenían más práctica como instructoras o un mejor domino de su L2, ya fuera ésta el inglés o el español. Sin embargo, los usos más discutidos y esperados del inglés en clase (logístico y pedagógico) no fueron en ningún caso el más común. La razón principal por la que las profesoras usaban el inglés era por cuestiones de relación de comunicación con sus estudiantes, es decir, el uso social de la lengua. This paper presents the results of a study centered on the use of English (L1 of the students) by teachers in the second-semester college level Spanish class. The results show that instructors consciously choose when and how they use English or Spanish and that the more experienced teachers, as well as those that have a better dominance of their L2, use less English in class. My research adds to that from previous investigations through the analysis of the social, logistical and pedagogical use of the students’ L1. My study shows that educators use English socially in order to establish rapport with their students far more often than for logistical or pedagogical reasons. / text