Essays on Financial Structure, Managerial Compensation and the Product Market

This thesis consists of three chapters on financial structure, managerial compensation, and product markets. The unifying theme of these chapters is to examine how the financial decisions of firms are affected by market imperfections. Chapter 1 places emphasis on the impact of internal imperfections arising from asymmetric beliefs (or behavioral biases) and agency conflicts by examining how these internal imperfections affect managerial compensation and corporate financial structure. On the other hand, Chapters 2 and 3 incorporate external market imperfections especially arising from imperfect product market competition. More specifically, these two chapters develop market equilibrium frameworks to examine how the matching market for CEOs and firms interacts with the product market to affect the distributions of CEO compensation and firm size. In Chapter 1, we develop a dynamic model to examine the effects of asymmetric beliefs of a firm\u27s manager and blockholders regarding the profitability of the firm\u27s projects, and differing attitudes towards their risk, on its capital structure. The firm\u27s capital structure reflects the tradeoff between the positive incentive effects of managerial optimism that increases the manager\u27s output and blockholders\u27 private benefits against the negative effects of risk-sharing costs. We provide several testable implications for the effects of the degree of managerial optimism as well as permanent and transitory components of the firm\u27s risk on different components of capital structure. In our calibration of the model, performed separately for different industries, we show that while optimism and risk have qualitatively similar effects on capital structure in different industries, their quantitative effects are significantly different. The interactive effects of asymmetric beliefs and agency conflicts could potentially explain a significant portion of the substantial inter-industry variation in capital structure. Chapter 2 studies how the distributions of CEO talent and compensation vary across industries, and how product market characteristics affect these distributions. We develop a market equilibrium model that incorporates the competitive assignment of CEOs to firms in a framework in which firms engage in imperfect product market---specifically, monopolistic---competition. Using the distributions of CEO pay and firm value in each of twelve Fama-French industries, we calibrate the parameters of our structural model, and indirectly infer the unobserved distributions of CEO talent and firm quality that together determine firm output. We then conduct several counterfactual experiments using the calibrated models corresponding to each of the industries. We find that the distribution of CEO talent does, indeed, vary dramatically across industries. More importantly, contrary to the conclusions of earlier studies that abstract away from the effects of the product market (Tervio, 2008 and Gabaix and Landier, 2008), the impact of CEO talent on firm value appears to be quite significant. Our estimates of the effect of CEO talent on firm value for the industries in our sample are two orders of magnitude higher than those obtained by the aforementioned studies. Further, our estimates suggest that the compensation of CEOs is quantitatively in line with their contributions to firms. Broadly, our study shows that it is important to incorporate the product market environment in which firms operate when assessing the contributions of CEOs to firms. Chapter 3 builds a market equilibrium framework in which the CEO-firm matching process is affected by the product market. We show that under reasonable assumptions there is a unique equilibrium in which only managers with ability above a unique cutoff level are matched to firms. This very simple screening process endogenizes the distribution of active managers who match with firms. Our calibration of the model using a parametric approach, which is in contrast with the empirical analysis performed in Chapter 2, strongly supports the principle arguments on the importance of CEO talent and appropriate CEO talent levels (on average) in Chapter 2. In addition, due to the law of demand and supply, which is a key feature of the extended model, we obtain somewhat different influence of some of product market characteristics on CEO pay. Furthermore, our parametric approach allows us to draw some implications for the effects of CEO talent distribution on the market equilibrium

Factors associated with Postpartum Depression and Its Influence on Maternal Identity

PURPOSE: This study aimed to examine the factors associated with postpartum depression and its influence on maternal identity of postpartum women. METHODS: Research design was a cross sectional descriptive study with a total of 89 women within the six month postpartum period. Associations of eating habits, overall sleep quality and other factors with postpartum depression utilizing the Korean Beck Depression Inventory (K-BDI) were done. The influence of postpartum depression on maternal identity was analyzed. Variables yielding significant associations (p<.05) were included in an adjusted logistic regression and a stepwise multiple regression. RESULTS: Mean scores of postpartum depression was 9.42+/-6.08 and 31.5% (n=28) for mild depression, 11.2% (n=10) was moderate and 4.5% (n=4) was severe depression on the K-BDI scale. Perceived health status and overall sleep quality were predictors of postpartum depression. Postpartum depression and the husband's love were predictors of maternal identity. CONCLUSION: Awareness of poor health perception and sleep quality will be helpful to detect for postpartum depression. Strategies to increase maternal identity during the postpartum period would be tailored by level of depression

Metal/graphene sheets as p-type transparent conducting electrodes in GaN light emitting diodes

We demonstrate the use of graphene based transparent sheets as a p-type current spreading layer in GaN light emitting diodes (LEDs). Very thin Ni/Au was inserted between graphene and p-type GaN to reduce contact resistance, which reduced contact resistance from similar to 5.5 to similar to 0.6 Omega/ cm(2), with no critical optical loss. As a result, LEDs with metal-graphene provided current spreading and injection into the p-type GaN layer, enabling three times enhanced electroluminescent intensity compared with those with graphene alone. We confirmed very strong blue light emission in a large area of the metal-graphene layer by analyzing image brightness.open281

Materials and extracellular matrix rigidity highlighted in tissue damages and diseases: Implication for biomaterials design and therapeutic targets

Rigidity (or stiffness) of materials and extracellular matrix has proven to be one of the most significant extracellular physicochemical cues that can control diverse cell behaviors, such as contractility, motility, and spreading, and the resultant pathophysiological phenomena. Many 2D materials engineered with tunable rigidity have enabled researchers to elucidate the roles of matrix biophysical cues in diverse cellular events, including migration, lineage specification, and mechanical memory. Moreover, the recent findings accumulated under 3D environments with viscoelastic and remodeling properties pointed to the importance of dynamically changing rigidity in cell fate control, tissue repair, and disease progression. Thus, here we aim to highlight the works related with material/matrix-rigidity-mediated cell and tissue behaviors, with a brief outlook into the studies on the effects of material/matrix rigidity on cell behaviors in 2D systems, further discussion of the events and considerations in tissue-mimicking 3D conditions, and then examination of the in vivo findings that concern material/matrix rigidity. The current discussion will help understand the material/matrix-rigidity-mediated biological phenomena and further leverage the concepts to find therapeutic targets and to design implantable materials for the treatment of damaged and diseased tissues

Effects on Growth and Osteogenic Differentiation of Mesenchymal Stem Cells by the Zinc-Added Sol-Gel Bioactive Glass Granules

Responses of mesenchymal stem cells (MSCs) cultured with zinc-added (2 and 5%) bioactive glass granules were evaluated in terms of cell growth and osteogenic differentiation. MSCs were cultured with different quantities (3, 10 and 30) of glass granules for up to 21 days in the osteogenic medium. Cell growth was stimulated by a small quantity of glasses, particularly those that contained zinc. Osteogenic differentiation, as assessed by alkaline phosphatase activity (ALP) activity, was significantly enhanced by the glasses, particularly with large quantities of glass and for prolonged culturing. Expression of bone-sialo protein (BSP) was significantly up-regulated around the bioactive glass granules. Moreover, the zinc addition significantly altered the ALP and BSP depending on the culture time and glass quantity. Cellular mineralization was improved in all glass samples, and particularly in the 2% zinc-glass. Taken together, the zinc addition to bioactive glass induced the MSCs growth and their osteogenic differentiation, at least to the level of zinc-free glass, and with even higher level observed depending on the quantity and culture time. These findings indicate that the zinc addition to bioactive glass may be useful in development of biomaterials for the stimulation of adult stem cell in bone tissue engineering

Impact of mechanical stretch on the cell behaviors of bone and surrounding tissues

Mechanical loading is recognized to play an important role in regulating the behaviors of cells in bone and surrounding tissues in vivo. Many in vitro studies have been conducted to determine the effects of mechanical loading on individual cell types of the tissues. In this review, we focus specifically on the use of the Flexercell system as a tool for studying cellular responses to mechanical stretch. We assess the literature describing the impact of mechanical stretch on different cell types from bone, muscle, tendon, ligament, and cartilage, describing individual cell phenotype responses. In addition, we review evidence regarding the mechanotransduction pathways that are activated to potentiate these phenotype responses in different cell populations

Electrospun Nanofibers Applications in Dentistry

Nanofibrous structures exhibit many interesting features, such as high surface area and surface functionalization and porosity in the range from submicron to nanoscale, which mimics the natural extracellular matrix. In particular, electrospun nanofibers have gained great attention in the field of tissue engineering due to the ease of fabrication and tailorability in pore size, scaffold shape, and fiber alignment. For the reasons, recently, polymeric nanofibers or bioceramic nanoparticle-incorporated nanofibers have been used in dentistry, and their nanostructure and flexibility have contributed to highly promotive cell homing behaviors, resulting in expecting improved dental regeneration. Here, this paper focuses on recently applied electrospun nanofibers in dentistry in the range from the process to the applications

A Case of Korean Ginseng-Induced Anaphylaxis Confirmed by Open Oral Challenge and Basophil Activation Test

Two case reports discussing Korean ginseng-induced allergic reactions have been published; both were inhalation-induced respiratory allergies in occupational settings. In this report we discuss the first case of anaphylaxis that developed after an oral intake of ginseng, confirmed by an open oral challenge, a skin prick test (SPT), and a basophil activation test (BAT). A 44-year-old man experienced rhinorrhea and nasal stiffness, followed by respiratory difficulty with wheeze and abdominal pain 10 minutes after oral intake of fresh ginseng. He had suffered from episodes of allergic rhinitis during the spring season for several years. Upon presentation, a physical examination, chest radiograph, and routine laboratory tests were unremarkable. Total serum IgE level was 41 IU/mL. The SPT results showed strong positive responses to alder, birch pollens, and ginseng extracts (1:500 w/v). The methacholine bronchial challenge test revealed a positive result at PC20 of 5.83 mg/mL. The open oral challenge was performed using 50 g of fresh ginseng and showed immediate onset of facial flushing, cough, respiratory difficulty with wheeze, and abdominal pain combined with a significant decrease in FEV1 levels (54% from the baseline). Serum-specific IgE and IgG4 antibodies were not detectable by enzyme-linked immunosorbent assay. BAT showed a remarkable increase in the expression of CD203c and CD63 with the addition of ginseng extract in a dose-dependent manner, while no changes were noted in the controls. In conclusion, oral intake of Korean ginseng could induce anaphylaxis, which is mediated by non-IgE-dependent direct activation of basophil/mast cells