Three Essays in Corporate Governance.

In Chapter 1, we find independent directors with CEO experience in a closely-related industry can improve firm value by improving the efficiency of capital expenditures and R&D investments. However, the effectuation of the potential contribution requires sufficient interaction with management. When the interaction is active, the industry-CEO experience has an economically and statistically significant positive impact; otherwise, the impact is insignificant. The interaction is proxied by competitive and dynamic challenges in product markets, the level of new business initiatives, or the frequency of board meetings. All proxies yield consistent evidence. Our findings demonstrate that active management-board interaction is essential to bring out the potential value independent directors can add to the firm. In Chapter 2, I propose fraction of experienced independent directors as an alternative measure of board monitoring. Serving as independent directors requires skills to effectively interact with management, which may be obtained through relevant past experience. Based on a sample of S&P 1500 firms over 2000-2010, I find the fraction of independent directors with at least five years of independent directorship experience proxies monitoring capacity of the board better than board independence. Independent director experience increases firm value when firms operate in non-competitive industry (high need for board monitoring). Board independence does not enhance firm value after controlling for the independent directorship experience. Independent directorship experience also increases CEO turnover-performance sensitivity. Past compensation committee experience may reduce total CEO compensation. In Chapter 3, we investigate performance implications of affiliated directors. Contrary to the view that independent directors may enhance corporate governance, we find affiliated directors may also enhance governance and firm performance: affiliated directors increase CEO pay-for-performance sensitivity, reduce managerial entrenchment, and enhance M&A and operation performance. The affiliation may provide directors better firm-specific information and aligned incentives. Not all affiliated directors are the same: directors affiliated through business relationship lead to subsequently improved performance. However, former employee directors are associated with lower corporate governance and firm performance. Directors that are precedents or descendents of the CEOs are positively associated with improved firm performance, but other types of family-related directors do not show such beneficial relation.PhDBusiness AdministrationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/102439/1/kshinwoo_1.pd

Terrain parameter estimation and traversability assessment for mobile robots

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (leaves 65-68).The estimation of terrain characteristics is an important missions of Martian exploration rovers. Since only limited resources and human supervision are available, efficient and autonomous method of estimation are required. In this thesis, an on-line estimation method of two important terrain parameters, cohesion and internal friction angle, is developed. The method uses onboard rover sensors and is computationally efficient. Terrain parameter estimation is of scientific interest, and can also be useful in predicting rover mobility on rough-terrain. A method to estimate traversability of a rover on deformable terrain using on-board sensors is presented. Simulation and experimental results show that the proposed methods can accurately and efficiently estimate traversability of deformable terrain.by Shinwoo Kang.S.M

Effects of a Dehydroevodiamine-Derivative on Synaptic Destabilization and Memory Impairment in the 5xFAD, Alzheimer's Disease Mouse Model

Carboxy-dehydroevodiamine·HCl (cx-DHED) is a derivative of DHED, which improves memory impairment. Carboxyl modification increases solubility in water, indicating that its bioavailability is higher than that of DHED. Cx-DHED is expected to have better therapeutic effects on Alzheimer's disease (AD) than DHED. In this study, we investigated the therapeutic effects of cx-DHED and the underlying mechanism in 5xFAD mice, transgenic (Tg) mouse model of AD model mice. In several behavioral tests, such as Y-maze, passive avoidance, and Morris water maze test, memory deficits improved significantly in cx-DHED-treated transgenic (Tg) mice compared with vehicle-treated Tg mice. We also found that AD-related pathologies, including amyloid plaque deposition and tau phosphorylation, were reduced after the treatment of Tg mice with cx-DHED. We determined the levels of synaptic proteins, such as GluN1, GluN2A, GluN2B, PSD-95 and Rabphilin3A, and Rab3A in the brains of mice of each group and found that GluN2A and PSD-95 were significantly increased in the brains of cx-DHED-treated Tg mice when compared with the brains of Tg-vehicle mice. These results suggest that cx-DHED has therapeutic effects on 5xFAD, AD model mice through the improvement of synaptic stabilization

Region-specific amyloid-β accumulation in the olfactory system influences olfactory sensory neuronal dysfunction in 5xFAD mice

Background: Hyposmia in Alzheimer’s disease (AD) is a typical early symptom according to numerous previous clinical studies. Although amyloid-β (Aβ), which is one of the toxic factors upregulated early in AD, has been identified in many studies, even in the peripheral areas of the olfactory system, the pathology involving olfactory sensory neurons (OSNs) remains poorly understood. Methods: Here, we focused on peripheral olfactory sensory neurons (OSNs) and delved deeper into the direct relationship between pathophysiological and behavioral results using odorants. We also confirmed histologically the pathological changes in 3-month-old 5xFAD mouse models, which recapitulates AD pathology. We introduced a numeric scale histologically to compare physiological phenomenon and local tissue lesions regardless of the anatomical plane. Results: We observed the odorant group that the 5xFAD mice showed reduced responses to odorants. These also did not physiologically activate OSNs that propagate their axons to the ventral olfactory bulb. Interestingly, the amount of accumulated amyloid-β (Aβ) was high in the OSNs located in the olfactory epithelial ectoturbinate and the ventral olfactory bulb glomeruli. We also observed irreversible damage to the ectoturbinate of the olfactory epithelium by measuring the impaired neuronal turnover ratio from the basal cells to the matured OSNs. Conclusions: Our results showed that partial and asymmetrical accumulation of Aβ coincided with physiologically and structurally damaged areas in the peripheral olfactory system, which evoked hyporeactivity to some odorants. Taken together, partial olfactory dysfunction closely associated with peripheral OSN’s loss could be a leading cause of AD-related hyposmia, a characteristic of early AD. © 2021, The Author(s).1

Spatial memory deficiency early in 6xTg Alzheimer’s disease mouse model

Abstract Alzheimer’s disease (AD) is mainly characterized by the deposition of extracellular amyloid plaques and intracellular accumulation of neurofibrillary tangles (NFTs). While the recent 5xFAD AD mouse model exhibits many AD-related phenotypes and a relatively early and aggressive amyloid β production, it does not show NFTs. Here, we developed and evaluated a novel AD mouse model (6xTg-AD, 6xTg) by crossbreeding 5xFAD mice with mice expressing mutant (P301L) tau protein (MAPT). Through behavioral and histopathological tests, we analyzed cognitive changes and neuropathology in 6xTg mice compared to their respective parental strains according to age. Spatial memory deficits occurred in 6xTg mice at 2 months of age, earlier than they occurred in 5xFAD mice. Histopathological data revealed aggressive Aβ42 and p-tau accumulation in 6xTg mice. Microglial activation occurred in the cortex and hippocampus of 6xTg mice beginning at 2 months. In 6xTg model mice, the synaptic loss was observed in the cortex from 4 months of age and in the hippocampus from 6 months of age, and neuronal loss appeared in the cortex from 4 months of age and in the hippocampus 6 months of age, earlier than it is observed in the 5xFAD and JNPL3 models. These results showed that each pathological symptom appeared much faster than in their parental animal models. In conclusion, these novel 6xTg-AD mice might be an advanced animal model for studying AD, representing a promising approach to developing effective therapy

Impact of Classified Board on M&A Target Shareholder Value: Nurturing Innovation through Entrenchment

We find that classified board in the M&A target firm is positively related to the target shareholder value, but only for firms with both intensive R&D investment and strong external governance. We also find that firms with classified board exhibit superior quality innovation when they have both intensive R&D investment and strong external governance. These findings are consistent with the view that classified board provides long-term perspectives that promote productive but risky R&D investment, which is highly valued in M&A. Our findings are distinct from the view expressed in extant literature that classified board enhances target shareholder value because of stronger bargaining power

Effect of cx-DHED on Abnormal Glucose Transporter Expression Induced by AD Pathologies in the 5xFAD Mouse Model

Alzheimer’s disease (AD) is a form of dementia associated with abnormal glucose metabolism resulting from amyloid-beta (Aβ) plaques and intracellular neurofibrillary tau protein tangles. In a previous study, we confirmed that carboxy-dehydroevodiamine∙HCl (cx-DHED), a derivative of DHED, was effective at improving cognitive impairment and reducing phosphorylated tau levels and synaptic loss in an AD mouse model. However, the specific mechanism of action of cx-DHED is unclear. In this study, we investigated how the cx-DHED attenuates AD pathologies in the 5xFAD mouse model, focusing particularly on abnormal glucose metabolism. We analyzed behavioral changes and AD pathologies in mice after intraperitoneal injection of cx-DHED for 2 months. As expected, cx-DHED reversed memory impairment and reduced Aβ plaques and astrocyte overexpression in the brains of 5xFAD mice. Interestingly, cx-DHED reversed the abnormal expression of glucose transporters in the brains of 5xFAD mice. In addition, otherwise low O-GlcNac levels increased, and the overactivity of phosphorylated GSK-3β decreased in the brains of cx-DHED-treated 5xFAD mice. Finally, the reduction in synaptic proteins was found to also improve by treatment with cx-DHED. Therefore, we specifically demonstrated the protective effects of cx-DHED against AD pathologies and suggest that cx-DHED may be a potential therapeutic drug for AD

Multi-Sensor Terrain Estimation for Planetary Rovers

rovers to perform difficult tasks in rough terrain, with limited human supervision. Knowledge of terrain physical characteristics would allow a rover to adapt its control and planning strategies to maximize its effectiveness . This paper describes recent and current work at MIT in the area of terrain estimation and sensing. A method for on-line terrain parameter estimation is presented. A complementary method for terrain traversability estimation is also presented. Sensor issues related to terrain estimation are discussed, and a vision-based method for measuring wheel sinkage is described. It is shown that these methods can lead to accurate and efficient understanding of a rover's physical surroundings