Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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Now showing 1 - 4 of 4
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    HOW AND WHEN SIGNALING IMPACTS CONSUMPTION
    (2021) Kim, Nicole You Jeung; Ratner, Rebecca K.; Wang, Yajin; Business and Management: Marketing; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This dissertation includes three essays that investigate the impact of signals that certain consumption choices can send to other consumers. In particular, each essay focuses on how consumers’ consumption-related decisions (e.g., choice of hedonic items, selecting low variety, and communicating that one has no preference) impact an observing audience’s perceptions of the consumer and the subsequent impacts on the observer. The first essay demonstrates that consumers strive to position themselves as attractive friends by making hedonic consumption decisions. While consumers shift to hedonic consumption, anchoring on their belief that others would heavily value fun when it comes to friendship, this essay demonstrates that consumers themselves actually value other aspects of friendship more, such as meaningfulness. As a result of this discrepancy in the belief of friendship, hedonic choice does not effectively help consumers cultivate friendship with another person. The second essay investigates the signals that selecting a low (vs. high) variety of items sends to observers. Choosing low variety signals to observers that the consumer has accumulated consumption experiences in the past, and thus has greater expertise, compared to choosing high variety. This signal of expertise endows the consumer with influence to impact observers to make consumption choices that mimic the consumer and be more willing to take the consumer’s recommendations. The third essay examines the impact of expressing no preference in a joint decision making context. While consumers expect to make the decision easier for the recipient, recipients of no preference communication (vs. explicit preference communication), experience greater decision difficulty. This unexpected negative impact occurs because recipients of no preference communication perceive that the communicator actually has preferences that they are hiding. Further, because recipients infer that these hidden preferences are dissimilar to one’s own preferences, they end up making a choice for the joint consumption that they personally less prefer.
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    Mechanobiology of T cell activation
    (2015) Hui, King Lam; Upadhyaya, Arpita; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Cells can sense and respond to the physical environment through generation and transmission of mechanical forces from the surroundings to the cell interior and from one cell to another. This dissertation focuses on mechanosensing by T cells, key players in the adaptive immune system, which form a strong line of defense against infections by their ability to recognize foreign molecules and develop an appropriate response. T cells form close contact with an opposing antigen presenting cell upon recognition of protein fragments derived from infecting pathogens (antigens). Recent studies have shown that externally applied forces can trigger biochemical signaling in T cells. How forces are internally generated by T cells, involved in signaling and transmitted at the level of the cell interface, remains unclear. In this thesis, we investigate the molecular mechanisms of force generation by T cells and their response to forces and the stiffness of the opposing surface. We have quantitatively characterized the initial phase of T cell contact with a model of antigen-bearing surfaces. We observe that T cells spread on such substrates and that the kinetics of spreading follows a universal function, with the spreading rate dependent on actin polymerization and myosin II activity. Altering cell-substrate adhesions leads to qualitative changes in cell spreading dynamics and wave-like patterns of actin dynamics. We then used soft elastic substrates with stiffness comparable to that of antigen presenting cells, to measure the forces generated by T cells during activation. Perturbation experiments reveal that these forces are largely due to actin assembly and dynamics, with myosin contractility contributing to the development of traction forces but not its maintenance. We find that Jurkat T-cells are mechanosensitive, with both traction forces and signaling dynamics exhibiting sensitivity to the stiffness of the substrate. We further demonstrate that dynamics of the T cell microtubule cytoskeleton also participates in regulating forces at the cell-substrate interface, through the Rho/ROCK pathway which regulates myosin II light chain phosphorylation. Overall, this work highlights physical force as an essential mediator that connects stiffness sensing to intracellular signaling, which then directs gene expression and eventually the immune response in T cells.
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    Words Matter: Essays on The Relationship Between Executive Word Choice and Investor Evaluation
    (2012) Guo, Wei; Goldfarb, Brent; Kirsch, David A; Business and Management: Management & Organization; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This dissertation examines the relationship between executive word choices and investor evaluations. Although the importance of language in organizations and the legitimating effect of language for new ventures has stimulated rich theoretical and empirical discussion, scholars still know little about whether, how, and when the language used by executives at established organizations influences external constituents (e.g., investors). I address these questions using two studies. In the first study, drawing from theories of persuasion and attitude change in social psychology, I examine the effect of emotional messages used by executives on investor evaluations and identify persuasion as one path by which executive language influences investors. In the second study, I combine two theoretical perspectives, the market signaling theory in economics and the construe-level theory in psychology, and investigate the effect of executives' use of realism words on investor evaluations. The second study identified signaling as another path by which executive language influences investors. Hypotheses from both studies were tested using a sample of 4,324 verbatim transcripts of 694 organizations' executive presentations at investor conferences between 2004 and 2010. This dissertation contributes to the strategy literature by providing an alternative theoretical framework that focuses on the psychological effect of executives' word choice, and by identifying two paths by which the language of executives in established organizations influence investor evaluations.
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    The crosstalk between B-cell receptor mediated signaling and the actin cytoskeleton
    (2008-08-15) Sharma, Shruti; Song, Wenxia; Cell Biology & Molecular Genetics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Oligomerization of the B-cell receptor (BCR) by antigen leads to both signal transduction and antigen internalization for processing and presentation. Previous studies indicate that these processes intersect at the actin cytoskeleton to coordinate the two cellular processes for the optimal activation of B-cells. The exact mechanism by which signals are transduced via the actin cytoskeleton into the efficient internalization and transport of BCR-antigen complexes is not well delineated. In this thesis, I demonstrate that Bruton's tyrosine kinase (Btk), a Tec kinase in the early signaling pathway of the BCR, is able to transduce signals from the BCR to actin regulatory proteins such as WASP and N-WASP. Upon BCR activation, Btk modulates actin dynamics by increasing the levels of phosphorylated, active WASP and N-WASP in B-cells. Btk regulates the activity of WASP and N-WASP by increasing the levels of PtdIns-4,5-P2 and phosphorylated Vav, both of which are required for WASP and N-WASP activation. Inhibition of Btk activity by a point mutation or a specific inhibitor prevents BCR-induced increases in PtdIns-4,5-P2 as well as in phosphorylated WASP, N-WASP and Vav. Furthermore, Btk deficiency or inhibition leads to a severe reduction in BCR-mediated antigen internalization, processing, and presentation to cognate T-cells. Further studies on the role of WASP show no significant effect of WASP deficiency on BCR internalization, while WASP deficiency affects B-cell development, decreasing the numbers of T1/T2 immature B-cells and marginal zone B-cells. Intriguingly, the protein expression levels of N-WASP and WAVE-2, homologues of WASP, increase in WASP-/- B-cells, implicating a compensatory role for WASP homologues in the absence of WASP. Over-expression of N-WASP's proline-rich domain inhibits BCR-mediated antigen uptake and intracellular transport. All of these data indicate that Btk, which is activated upon BCR binding to antigen, regulates actin dynamics and consequently antigen uptake and transport, by activating WASP and N-WASP via Vav and phosphatidylinositides. This presents a novel mechanism by which BCR-mediated signaling regulates BCR-mediated antigen processing and presentation.