Ray theory plays an important role in seismic imaging and velocity model building. Although rays are the high-frequency asymptotic solutions of the wave equation and therefore do not usually capture all details of the wave physics, they provide a convenient and effective tool for a wide range of geophysical applications. Especially, ray theory gives rise to traveltimes. Even though wave-based methods for imaging and model building had attracted significant attentions in recent years, traveltime-based methods are still indispensable and should be further developed for improved accuracy and efficiency. Moreover, there are possibilities for new ray theoretical methods that might address the difficulties faced by conventional traveltime-based approaches. My thesis consists of mainly four parts. In the first part, starting from the linearized eikonal equation, I derive and implement a set of linear operators by upwind finite differences. These operators are not only consistent with fast-marching eikonal solver that I use for traveltime computation but also computationally efficient. They are fundamental elements in the numerical implementations of my other works. Next, I investigate feasibility of using the double-square-root eikonal equation for near surface first-break traveltime tomography. Compared with traditional eikonal-based approach, where the gradient in its adjoint-state tomography neglects information along the shot dimension, my method handles all shots together. I show that the double-square-root eikonal equation can be solved efficiently by a causal discretization scheme. The associated adjoint-state tomography is then realized by linearization and upwind finite-differences. My implementation does not need adjoint state as an intermediate parameter for the gradient and therefore the overall cost for one linearization update is relatively inexpensive. Numerical examples demonstrate stable and fast convergence of the proposed method. Then, I develop a strategy for compressing traveltime tables in Kirchhoff depth migration. The method is based on differentiating the eikonal equation in the source position, which can be easily implemented along with the fast-marching method. The resulting eikonal-based traveltime source-derivative relies on solving a version of the linearized eikonal equation, which is carried out by the upwind finite-differences operator. The source-derivative enables an accurate Hermite interpolation. I also show how the method can be straightforwardly integrated in anti-aliasing and Kirchhoff redatuming. Finally, I revisit the classical problem of time-to-depth conversion. In the presence of lateral velocity variations, the conversion requires recovering geometrical spreading of the image rays. I recast the governing ill-posed problem in an optimization framework and solve it iteratively. Several upwind finite-differences linear operators are combined to implement the algorithm. The major advantage of my optimization-based time-to-depth conversion is its numerical stability. Synthetic and field data examples demonstrate practical applicability of the new approach. / text

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This study examined the similarities and differences in the adolescent monozygotic (MZ) twin and same-sex dyzygotic (DZss) twin sibling relationship. Specific constructs investigated were: companionship, empathy, directiveness/teaching, avoidance, rivalry, and aggression. Participants included 192 same-sex twin pairs, age 9 - 18, and their biological parents. The data is part of a national study from the Non-Shared Environment in Adolescent Development Project. The nationally representative data set provided a measure of the Sibling Inventory of Behavior - Expanded Version (Anderson & Rice, 1999), whereby each participant individually responded to the paper-pencil questionnaire. Twinship status differences, gender differences, reporter differences and reporter by twinship interactions were examined. The results found significant differences between MZ twins and DZss twins on the constructs of empathy, companionship, avoidance, rivalry, and aggression. MZ twins demonstrated and reported higher levels of empathy and companionship and lower levels of avoidance, rivalry, and aggression, when compared to DZss twins. There was no interaction effect of twinship by gender, except on directiveness/teaching; however, significant differences were found between male MZ/DZss twins and female MZ/DZss twins on the constructs of empathy, companionship, directiveness/teaching, and avoidance. Female MZ/DZ twins reported and demonstrated higher levels of empathy, companionship, and directiveness/teaching, and lower levels of avoidance. Overall, there were no reporter differences between twins on any of the six constructs. There were significant differences between parental perceptions and twin perceptions on empathy, companionship, directiveness/teaching, rivalry and aggression. A significant difference between mothers and fathers was found on the constructs of empathy and avoidance. On the construct of avoidance, mothers and fathers differed from each other, however, fathers did not differ from the twins. There was no twinship by reporter interaction effect, except on directiveness/teaching. Overall, the results suggest that MZ twins report and are perceived as having a more positive relationship than DZss twins. The results also support the need for multireporter research in order to obtain a truer picture of the family relationship. The gender findings further extend the understanding of the role of gender in the sibling relationship. Lastly, due to the paucity of twin research, the results aid in the development of a framework for understanding the adolescent twin relationship.

No description available.

The purpose of this study is to analyze the effect of CBI-reforms on inflation in different parts of the world from a theoretical and empirical perspective. Compared to previous studies, this study focuses on whether CBI-reforms have different effects on reducing inflation in different parts of the world. The study is based on a 132 country data-set from 1980 to 2005 compiled by Daunfeldt et al. (2008). The result indicates that the reduction in inflation due to the CBI-reforms varies between 2.2 and 12.32 percentage points in Asia, Europe, South America and Oceania, supporting the claim that implementing CBI-reforms can be successful in reducing inflation in most of the parts of the world.

The cumulative risk model is used to explain the coexistence of small gender differences and large health disparities between husbands and wives. Specifically, the current model incorporates conflict (a risk factor), support (a protective factor), and coping (a moderator of the conflict-stress link) to predict cortisol slopes for newlywed husbands and wives. One hundred and seventy-two couples completed both global and daily measures of protective factors (empathy, responsiveness, and perceived support), risk factors (withdrawal, loyalty, self-silencing, and negativity), and coping (self-distraction, substance use, emotional support, and rumination). For the six days that participants provided daily reports of these constructs, participants also provided waking and evening saliva samples for later determination of salivary cortisol levels. I hypothesized that men would incur more protective factors than would women, and that these protective factors would be associated with steeper cortisol slopes (i.e., healthy cortisol slopes.) Further, I hypothesized that women would incur more cumulative risks than would men, and that these risks would be associated flatter cortisol slopes (i.e., unhealthy cortisol slopes). Finally, I hypothesized that the association between cumulative risk and cortisol slopes would be moderated by coping, such that theoretically-effective coping strategies would blunt the impact of cumulative risks whereas ineffective coping strategies would exacerbate the impact of cumulative risks. Support for these hypotheses was mixed. Women did incur fewer cumulative protective factors than did men; however, there were no gender differences in cumulative risks for this highly satisfied newlywed sample. The impact of both cumulative protection and cumulative risk on cortisol slopes differed for men and women. Coping moderated the impact of cumulative risk on daily cortisol slopes, but again these patterns were different for men and women. Future work must continue to isolate gender differences in relationship processes to understand resulting health implications. With further refinement, the proposed model can provide a more holistic explanation of gendered health disparities, and perhaps identify ways that women and men can experience more equivalent health benefits from romantic relationships. / text

This dissertation contains two essays that use empirical techniques to shed light on open questions in the asset pricing literature. In the first essay, I investigate whether foreign institutional investors affect stock liquidity in domestic equity markets. The evidence indicates that stocks with higher foreign institutional ownership subsequently experience higher liquidity. However, it is difficult to interpret the causal relation of this finding because institutional investors self-select into more liquid stocks. To solve this problem, I exploit a provision in the 2003 US dividend tax cut which extends tax-relief to dividends from US tax-treaty countries but not to dividends from non-treaty countries. This natural experiment suggests a causal link between foreign institutional investors and liquidity. Consistent with the predictions of theoretical models, I find that liquidity improves due to foreign institutional investors increasing information competition. In the second essay, I introduce a new measure of difference of opinion using mutual fund portfolio weights to test prominent competing theories of the effect of heterogeneous beliefs on asset prices. The over-valuation theory (Miller (1977)) proposes that in the presence of short-sale constraints stock prices reflects only the view of optimistic investors which implies lower subsequent returns. Alternatively, neo-classical asset pricing models (Williams (1977), Merton (1987)) suggest that differences of opinions indicate high levels of information uncertainty or risk which implies higher expected returns. My initial result finds no support for the over-valuation theory. Instead, the measure used in this study finds that high differences of opinion stocks weakly outperform low differences of opinion stocks by 2.42% annually which is more consistent with the information uncertainty explanation. / text

published_or_final_version / Sociology / Master / Master of Social Sciences

published_or_final_version / Nursing Studies / Master / Master of Nursing in Advanced Practice

published_or_final_version / abstract / toc / Sociology / Master / Master of Philosophy