In man, tolerance to an orthostatic stress varies widely. Compensatory cardiovascular responses to orthostatic stressors such as head-up tilt, +Gz acceleration, and lower body negative pressure (LBNP) have been identified. However, physiologic reactions associated with the capacity to withstand a presyncopal- limited orthostatic exposure requires additional clarification. The relationship between maximal oxygen uptake (‘VO₂ max) and presyncopal-limited LBNP tolerance was examined in adult male subjects categorized into high (HAC) and low (LAC) aerobic capacity groups. In addition to similar (N.S.) cardiovascular responses, the (mean) and cumulative LBNP stress indices (CS)) observed in the HAC (722 torr•min) and LAC (784 torr•min) groups were also similar (N.S.). These data fail to support a relationship between LBNP tolerance and ‘VO₂ max. Cardiovascular responses associated with LBNP tolerance were measured during the control period (pre-LBNP) and final minute (peak LBNP) of decompression. The CSI criterion distinguished high (HT, n = 10) and low (LT, n = 8) LBNP tolerant groups was 640 torr•min. A greater (p < 0.05) end-diastolic volume and cardiac output was observed in the HT subjects during pre-LBNP may have provided a larger reserve to utilize throughout exposure to LBNP. At peak LBNP, both groups demonstrated similar (N.S.) cardiac outputs despite a higher (p < 0.05) HT heart rate. These data suggest that a major mechanism in prolonging LBNP tolerance may have been a greater LBNP-induced tachycardia. Blood samples were drawn to determine group differences in vasoactive neuroendocrine response. During peak LBNP, concentrations of norepinephrine increased (p < 0.05) in both groups. The HT group displayed greater (p < 0.05) LBNP-induced increases in vasopressin and plasma renin activity. These data suggest that HT subjects may have supplemented the catecholamine pressor response by involving the vasopressin and renin-angiotensin systems. The affect of cholenergic and beta-adrenergic blockades on cardiovascular responses to LBNP were examined in six HT and five LT subjects. CSI in both groups were unchanged (N.S.) by administration of atropine as compared to a placebo LBNP exposure. Propranolol however, reduced (p < 0.05) LBNP tolerance in both groups. This CSI reduction was greater (p < 0.05) in the HT subjects. The reduction in LBNP tolerance appeared closely associated with the negative chronotropic effect.

The first chapter of this dissertation evaluates changes in fuel procurement practices by coal- and natural gas-fired electricity generating plants in the United States following state-level legislation that ended cost-of-service regulation. I construct a detailed dataset that links confidential, shipment-level data on the price of virtually all of the fuel delivered to coal- and gas-fired electricity plants in the United States from 1990-2009, with plant-level data on operations and regulatory status. I find the price of coal drops by 12% at deregulated plants relative to matched plants that were not subject to any regulatory change, whereas there was no relative drop in the price of gas. I show how my results lend support to theories of asymmetric information between generators and regulators, regulatory capture, and capital-bias as important sources of distortion under cost-of-service regulation. The second chapter analyses changes in the cost of generating electricity following the introduction of regional wholesale electricity markets. I use proxy methods based on Olley and Pakes (1996); Levinsohn and Petrin (2003) to estimate fuel-specific production functions, and construct the Olley-Pakes productivity index to decompose costs in to within-plant productivity and allocative efficiency changes. I then apply a potential outcomes framework to the derived productivity estimates, allowing the construction of counterfactual costs that explicitly account for permanent differences between market and non-market areas and common transitory shocks. I find that the introduction of market-based dispatch methods has reduced fossil-fuel production costs by upwards of 15%. The third chapter is based on joint work with Roland Fryer and Jorg Spenkuch. We develop a Roy model in which individuals sort into peer groups based on comparative advantage. Two key results emerge: First, when comparative advantage is the guiding principle of peer group organization, the effect of moving a student into an environment with higher-achieving peers depends on where in the ability distribution she falls and the effective wages that clear the social market. As a result, linear in means estimates of peer effects are not identified. We show that the model’s testable prediction in the presence of this confounding issue is borne out in two data sets. / Economics

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Statutory reserves in life insurance companies are required by regulation laws. Regulators monitor insurers’ statutory reserves to protect policy holders’ future benefits and ensure the insurers are financially healthy. The purpose of this report is to give a brief introduction to statutory reserves in life insurance companies. In this report, assumptions and valuation methods for statutory reserve valuations are explained and discussed. The comparisons between statutory reserves and GAAP reserves are also discussed. / text

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College-aged individuals experience verbal and physical dating aggression at high rates, which is troubling given the associated deleterious consequences. Verbal and physical aggression are highly correlated, with verbal aggression often serving as a precursor to physical aggression. The current studies examined factors that may influence the likelihood and escalation of dating aggression in response to a dating conflict scenario, including alcohol intoxication, self-regulation, and trait aggressivity. Study 1 assessed the construct validity of a newly developed audio-taped scenario of mutual aggression as well as a hot sauce task. Men and women with (n=31) and without (n=30) a history of past-year dating aggression provided responses to the conflict scenario using the Articulated Thoughts in Simulated Situations (ATSS) procedure. Under the guise of an assessment of sensitivity, participants allocated hot sauce for a fictitious participant to consume. Results supported the construct validity of the conflict scenario but not the hot sauce task, which was therefore not included in Study 2. Study 2 examined the influence of alcohol's pharmacological and expectancy effects as well as one’s ability to self-regulate thoughts, feelings, and behavior on aggression intentions in response to the mutual aggression conflict scenario. Participants were randomized to either receive alcohol (n=48; blood alcohol content M = .082%), placebo (n=48), or no alcohol (n=48). Using ATSS procedures identical to Study 1, intoxicated individuals articulated more verbal aggression intentions overall and exhibited a greater increase across the conflict scenario than those who did not receive alcohol, but did not differ from those who received placebo. There were no effects of alcohol on physical aggression intentions. Individuals who received placebo and who were poorer at suppressing emotions articulated more verbal aggression intentions than intoxicated individuals. Additionally, individuals higher in trait aggressivity articulated more physical aggression intentions and intoxicated individuals with lower relationship satisfaction articulated more verbal aggression intentions. Results suggest that both the pharmacological and expectancy effects of alcohol were important to the occurrence of aggression. Whereas higher trait aggressivity and lower relationship satisfaction may be risk  factors  for  aggression,  regulating  one’s  emotions  may  reduce  the frequency of aggression. / text

published_or_final_version / abstract / toc / Botany / Master / Master of Philosophy

published_or_final_version / abstract / toc / Biochemistry / Master / Master of Philosophy