Three Essays on Postsecondary Education

Thompson, John C The University of Texas at Dallas ProQuest Dissert 2019 해외박사(DDOD)

Postsecondary education has numerous long-term impacts on those students who go on to pursue and complete it. In this work, I examine the impact of several policies which influence student’s entry into and matriculation through the postsecondary system of Texas. My first chapter looks at the impact of going to a flagship university for students who gain access to that school through an uncommon pathway. My second chapter examines the impact of the Budget Control Act of 2011, and its elimination of subsidized student loans for graduate students, on educational outcomes for graduate students. My third chapter looks at the impacts that graduate student instructors have on the students who take their courses.

Emerging Network Connectomics in Phantom Sound Perception

Mohan, Anusha The University of Texas at Dallas ProQuest Dissert 2018 해외박사(DDOD)

The brain is hypothesized to be a hierarchical prediction system. It constantly compares the incoming information from the sensory pathways with a pre-existing model of the environment. Damage at different locations in these pathways leads to the loss of sensory input, resulting in the brain receiving different input from what it would expect. This may lead to an uncertainty that may be minimized by the production of a phantom percept. A phantom percept is the perception of a sensation in the absence of an external source. In this dissertation, we specifically focus on the auditory phantom percept: Tinnitus. Tinnitus is accompanied by a “loudness” component and a variable emotional component or “distress.” The loudness is unique to the disorder (domain-specific) and distress is common to other pathologies as well (domain-general). A wealth of information is available about the relationship between these behavioral correlates and changes in static functional connectivity. However, their relationship with dynamic changes in network connectivity is yet to be explored. Thus, the aim of this study is to investigate changes in the flexibility and stability of time-varying functional connectivity (temporal variability) in tinnitus and its relation to loudness and distress. In the current study, we observed a spatio-temporal change of temporal variability in tinnitus. We also observed that the relationship between temporal variability and behavioral symptoms depended on the amount of distress experienced. In participants with low distress, there was no linear relationship between temporal variability and loudness or distress. However, in participants with high distress, we observed that as loudness increases, temporal variability increases; and as distress increases temporal variability decreases. This trend is observed in the parahippocampus in the alpha2 frequency band. The increasing temporal variability with increasing loudness may relate to a Bayesian search for updating deafferentation-based missing information. On the other hand, the decreasing temporal variability with increasing distress possibly reflects less adaptive, contextual processing. Therefore, the findings may reveal a way of understanding the changes in network dynamics not just in tinnitus, but in other brain disorders as well. This dissertation is divided into 5 Chapters. Chapter 1 systematically reviews the phantom percepts in various sensory domains and the different mechanisms of compensation to sensory uncertainty. Chapter 2 focuses specifically on tinnitus. It reviews the current literature on tinnitus, their drawbacks and outlines the purpose of the current study. It also serves as an introduction to temporal variability, the measure of dynamic functional connectivity used in this dissertation. Chapter 3 describes the tinnitus and control groups, materials, and experimental methods used in the current study. Chapter 4 details the results of the current study. Finally, Chapter 5 discusses these results, limitations and future applications of the study.

Disparity in Risk Factors for Urban Residential Fire Related Injuries and Deaths

Min, Soojin The University of Texas at Dallas ProQuest Dissert 2018 해외박사(DDOD)

The location characteristics of neighborhoods and balance in demand and supply capacity may play a role in determining the effectiveness of fire protection service delivery. Spatial accessibility to fire protection services integrates the location characteristics of neighborhoods and the dimensions of demand and supply capacity of fire protection services. Using the two-step floating catchment area (2SFCA) method and logistic regression, this study measures spatial accessibility to fire protection services and examines its association with unintentional residential fire related injuries and deaths in Dallas, Texas. This analysis uses annual public fire incident data from 2012 to 2015, obtained from the U.S. Fire Administration, and census. In addition to fire characteristics and neighborhood demographics, spatial accessibility to fire protection services was significantly associated with unintentional residential fire related injuries with a small effect size. The analysis results suggest that there is disparity in the spatial accessibility score between low-income and non low-income census block groups, mainly in northeast and southwest service areas. The findings can be used to help identify high-risk neighborhoods for implementing fire injury prevention programs and select locations of additional fire stations.

Three Essays on Economic Demography

Zhang, Zeyu The University of Texas at Dallas ProQuest Dissert 2018 해외박사(DDOD)

There are three essays in my dissertation. The first essay examines the effect of participation in the Women, Infants, and Children (WIC) program on the distribution of household labor supply. Receiving benefits from this subsidy program has two.

The Effect of Partial Promoter Sequences on Primer Labeling and De Novo Initiation By T7 RNA Polymerasepolymerase

Padmanabhan, Ramesh The University of Texas at Dallas ProQuest Dissert 2018 해외박사(DDOD)

The bacteriophage T7 RNA polymerase (T7 RNAP) is the prototype of the family of single subunit RNA polymerases which includes the T3, SP6 and mitochondrial RNA polymerases. It is also the most well characterized enzyme of this family of polymera. Here, we have developed an in vitro transcription system to study the ability of T7 RNAP to use truncated promoters similar to mitochondrial promoters. In this system, we used oligonucleotides which are capable of forming intra- and inter-molecu.

The role of nucleus accumbens in tinnitus

Hullfish, Jeffrey Andrew The University of Texas at Dallas ProQuest Dissert 2019 해외박사(DDOD)

Targeting Auditory Cortex Plasticity Using Vagus Nerve Stimulation

Buell, Elizabeth Paige The University of Texas at Dallas ProQuest Dissert 2019 해외박사(DDOD)

Essays on Network Effects, Service Pricing Plans and Online Message Virality

Zihagh, Fereshteh The University of Texas at Dallas ProQuest Dissert 2019 해외박사(DDOD)

The first part of my dissertation investigates information technology and examines the matching between buyers and sellers in IT outsourcing markets, and how the social network between firms explains the observed matches. Specifically, I examine how interfirm connections and the information and resources accruing to firms from such connections-i.e., firm social capital - affect firms’ decision to sign a contract with a specific firm. The idea is that information spillovers from these connections constrain economic activities and that firms’ competitiveness changes by changing their network position. Using a unique panel data of 49,072 contracts signed between buyers and sellers in 1989-2013, I construct the network such that the nodes are the firms which are connected because they collaborate on shared projects. I use the network measures and client-specific characteristics in a two-sided matching model to quantify the change in the created joint value in the match when the firms’ network position changes. Results suggest that a network of vendors and clients is more valuable as the size of their network grows (i.e., higher joined social capital is more valued) and that clients with higher social capital derive disproportionally more value from a vendor’s network. Moreover, although synergies created from the similarity in network positions are valuable in most cases, there are exceptions to this which are explained by transaction costs specific to such instances. The findings help firms design their competitive strategy by predicting the effect of repositioning in the network.In my second chapter, I use a randomized field experiment to investigate customers’ reaction to pricing and tariff design in the internet service industry. Specifically, I examine the effect of promotions and tariff structure (3-part tariff) on internet subscriber revenue and churn using a field experiment. Researchers have reported cases in which the impact of pricing decisions on profits is beyond what economic interpretations justify. However, behavioral effects of pricing and tariff structure on post-purchase outcomes are ignored in empirical studies even though they provide useful insight into consumer behavior and can have significant policy implications. I propose a parsimonious model that allows pricing, tariff structure, and new service introduction to impact two relevant behaviors in contractual settings: the level of transactions after plan choice and the decision to churn. My model also accounts for customer heterogeneity by including “level of price-sensitivity” and comparing the behavior of high and low price-sensitive segments. I use data from an Internet Service Provider (ISP) in a natural field experiment setting and find that promotions attract new customers, but they do so at the cost of increasing customers’ price sensitivity and lowering their inertia. Moreover, I find that customers who are not exposed to promotions spend more on plan and credit purchases even after I control for possible self-selection of more price-sensitive customers into the group that is exposed to promotions. I also find that high price-sensitive customers respond differently to constant exposure to promotions compared with low price-sensitive segments. I conclude that doing less relevant and targeted promotions wins price-sensitive customers, but it also encourages showrooming and comparison behavior. In other words, a marketing campaign that attracts new customers may also hurt customer lifetime value. I recommend that firms need to consider this trade-off when designing pricing policies.In the last chapter, I develop an empirical model to study how users’ social capital, mediated by image motives (i.e., driven by the perception of others) and intrinsic motives (i.e., driven by personal satisfaction rather than posting consequences), influences the propensity to post/retweet positive or negative contents online. My findings show that the identity of users can explain their motivations to post on online platforms and the receivers' engagement with the posted contents. Results show that there is an inverted U-shaped relationship between the number of followers and motives. The breakdown of motives reveals that both image and intrinsic motives are highest for users with a medium number of followers. Moreover, I find that as the number of followers increases, users are more likely to post due to intrinsic motives than image-related motives. Even though users with a higher number of followers believe negative content can lead to more virality, they do not post negative content mainly because they do not care as much about the reciprocity from followers as they care about the intrinsic satisfaction that they derive from posting contents. The results of my model show that intrinsic motives (in order of importance: validate thoughts, have fun, be a listener, amplify news, entertain/inform, save tweets) are more conducive to posting of positive content. On the other hand, image motives (in order of importance: look clever/expert, identify with a group, gain followers) are associated with the negative content but have no significant association with the positive content. The findings have implications for designing social media content strategy and fostering reader engagement.

Applications of Software Defined Networking in a Service Provider Environment

Kadiyala, Krishna Priyanka The University of Texas at Dallas ProQuest Dissert 2019 해외박사(DDOD)

Software Defined Networking (SDN) is a networking paradigm that promises to give network administrators finer control over the network, the ability to manage traffic flows effectively, and make re-provisioning network resources faster while also enabling the network to be more flexible, scalable and visible. Despite the promises and potential of SDN, the adoption of SDN by service providers is a challenging, daunting task and hence has not seen approval and acceptance. Although this lack of adoption can be attributed to a few major factors, an important limitation is that enterprise networks do not have a green-field environment and it is not viable to do an overhaul of the existing traditional network infrastructure to build an SDN-based network in its place. Additionally, other significant concerns such as cost, time, performance and security are also deciding factors in enabling SDN in a service provider environment. To facilitate the adoption of SDN in ISPs and a smoother transition, the concept of a Hybrid SDN/IP network has emerged. The fundamental idea behind this concept of a hybrid network is to invest in a few SDN-capable devices that will be incorporated into an existing, functional and operational legacy network. This simple idea has been seen as a promising migration strategy to enable SDN adoption in service provider networks. The goal of this thesis is to explore, identify and implement use case scenarios of such a hybrid network, in which, a few SDN devices co-exist within the traditional network architecture. To this end, we first present Inter-Autonomous System Traffic Engineering with SDN that takes advantage of the presence of SDN devices in the network to solve the Inter-AS TE problem in service provider networks. By introducing SDN elements in the internal network of an AS, we show how the stringency of the internal network can be overcome to better load balance traffic on the outgoing links of the network. Intuitively, identifying productive locations to place the SDN devices can effectively decrease the number of SDN devices required to achieve the objectives for the ISP. In keeping with this idea, we then explore the SDN node selection problem that addresses how to choose a set of nodes in the existing network that can be replaced by SDN devices in order to meet the objective for Inter-AS TE in an ISP. Lastly, we propose Greening service provider networks with SDN to address the problem of high energy consumption in service provider networks. We aim to leverage the presence of SDN nodes in the network to enable shutting down unused routers within the network. Although shutting down routers inside a network results in lower energy consumption of the network, we run the risk of having all the traffic traverse through only a few egress links in the network, thereby leading to congestion on these links. Thus, we propose to take advantage of the flexibility of SDN nodes in the network by being able to move traffic around to avoid congestion on the egress links, while at the same time enabling shutdown of nodes in the network. We believe that the ideas explored and presented in this thesis bring to perspective interesting solutions incorporating SDN to some of the problems seen in today’s traditional service provider networks. These solutions are based on adopting a transitional approach to incorporating SDN with the legacy infrastructure and add to the many potential benefits that the SDN paradigm promises for a service provider network.

Identification of Ligands Selectively Targeting Breast Cancer Stem Cells via Combinatorial Chemical Library Screening

Long, Chao The University of Texas at Dallas ProQuest Dissert 2018 해외박사(DDOD)

Cancer stem cells (CSCs), also known as tumor-initiating cells (TICs), play critical roles in the resistance to anti-cancer therapies, tumor metastasis and tumor relapse. An innovative synthetic binder to cancer stem cells would provide not only a chemical tool to study the mechanism of cancer stem cells, but also become a lead ligand for imaging, diagnoses or therapeutics targeting cancer stem cells. Herein, a synthetic peptoid ligand CL-1-19-1 that selectively binds to cancer stem cell subpopulation over non-CSC subpopulations of breast cancer was identified via a cellbased high throughput screening from a one-bead-one-compound (OBOC) combinatorial chemical library. CL-1-19-1 was verified to bind to CD24−/CD44+/ALDH+ cancer stem cell phenotype of MCF-7, MDA-MB-231, and BT549 respectively. CL-1-19-1-immobilized beads can also be utilized as a synthetic tool for the isolation of cancer stem cell subpopulation from ovarian cancer and prostate cancer cell lines. CL-1-19-1-bound population of cancer cells displayed increased expressions of stemness-associated transcription factors, such as SOX2, KLF4, C-myc, and Nanog. Furthermore, the CL-1-19-1-bound population demonstrated a higher tumor growth rate in vivo, as well as larger tumor size and cells from the tumors exhibited stronger expressions of cancer stem cell markers and more migratory activity. In conclusion, CL1-19-1 has been identified as the first synthetic binder of breast, ovarian and prostate CSCs, thus having high prospects as a chemical tool for isolating cancer stem cells from various solid cancer types including breast, ovarian, and prostate.