Graduation date: 1992

Organic Light Emitting Diodes (OLEDs) are widely viewed as next generation platform for flat panel displays and solid state lighting. Currently, OLED efficiency is not high due to high driving voltage. Molybdenum trioxide (MoO3) is ideal for p-type doping of the wide bandgap organic semiconductor 4,4’-bis-9-carbozyl biphenyl (CBP). With p-type doped CBP layer as Hole Transport Layer (HTL), driving voltage can be significantly reduced. Effective design for doped OLED structure consists of a HTL with doped layer from 20nm to 40nm and MoO3 concentration above 5%, the optimized OLED with doped CBP HTL present an 18% improvement over a standard device with CBP HTL at 100mA/cm2. Injection is found to be the principle cause of the reduction of driving voltage and shows close relations to doped layer thickness. Also charge balance is an important factor for high current efficiency, doped layer can be used as tools to promote charge balance.

Organic Light Emitting Diodes (OLEDs) are widely viewed as next generation platform for flat panel displays and solid state lighting. Currently, OLED efficiency is not high due to high driving voltage. Molybdenum trioxide (MoO3) is ideal for p-type doping of the wide bandgap organic semiconductor 4,4’-bis-9-carbozyl biphenyl (CBP). With p-type doped CBP layer as Hole Transport Layer (HTL), driving voltage can be significantly reduced. Effective design for doped OLED structure consists of a HTL with doped layer from 20nm to 40nm and MoO3 concentration above 5%, the optimized OLED with doped CBP HTL present an 18% improvement over a standard device with CBP HTL at 100mA/cm2. Injection is found to be the principle cause of the reduction of driving voltage and shows close relations to doped layer thickness. Also charge balance is an important factor for high current efficiency, doped layer can be used as tools to promote charge balance.

Existing research suggests that market misvaluations affect corporate investment, often leading to suboptimal investment. I examine whether earnings smoothness reduces the impact of market valuations on corporate investment and in turn enhances investment efficiency. I find that earnings smoothness has a strong negative effect on the sensitivity of corporate investment to stock prices. Further analyses indicate that this negative effect is driven by both innate and discretionary components of earnings smoothness and is more pronounced for firms operating in more volatile business environments. I complement these findings by demonstrating that firms with smoother earnings have lower over- (under-)investment and higher future operating performance. Collectively, the evidence suggests that earnings smoothness improves corporate investment efficiency by reducing the impact of market valuations on investment.

Hepatitis C virus (HCV) causes a significant health problem worldwide due to the lack of effective vaccines. It has been recognized that a rapid, vigorous, and broadly targeted cell-mediated immune response (Th1-like) is often associated with the clearance of HCV infections. DNA vaccines represent a promising means for HCV vaccination because they tend to induce a Th1-biased cell-mediated response in the host cell. Currently, the delivery of DNA vaccine for HCV in large animals as well as in humans is not as effective as in small animals. Nano delivery systems would be a promising approach to overcome this problem. Carbon nanotubes (CNTs) have been extensively studied for delivering drugs, proteins, peptides, and nucleic acids including plasmid DNA to cells and organs with varying degrees of success, but few of them have been applied to DNA vaccine for HCV.<p> This thesis presents a study of using functionalized CNTs (f-CNTs) to improve the efficacy of plasmid DNA vaccine delivery for HCV. First, CNTs were functionalized via 1,3-dipolar cycloaddition reaction with the appropriate amino acids and aldehydes. NMR and TEM results suggested that the CNTs were successfully functionalized and became soluble in water. Then plasmid DNAs which encode green fluorescence protein reporter gene, luciferase reporter gene, and HCV core protein, respectively, were delivered into human hepatoma cells via calcium phosphate precipitation method, f-CNT delivery system, and a combination of f-CNT and calcium phosphate method, respectively. The result showed that f-CNTs, in combination with the calcium phosphate method, significantly enhanced the gene expression in human hepatoma cells.<p> Consequently, this study concludes that the f-CNT can significantly enhance gene expression in liver cells conferred by a plasmid DNA when combined with calcium phosphate precipitation method. Even though the mechanisms of this enhancement await further investigation, the results of this thesis may have important implications in developing DNA vaccines for infectious diseases in general and for hepatitis C in particular.

I examine the relation between tax avoidance and firm investment by drawing on two capital market imperfections, adverse selection and moral hazard, to provide a link between tax avoidance and investment. Firms experiencing capital rationing because of adverse selection rely on internal resources to fund investment opportunities because of costly external financing. Tax avoidance can provide additional cash-flows that may alleviate capital rationing. Alternatively, tax avoidance can exacerbate problems of moral hazard by facilitating managerial rent extraction in the form of overinvestment. I find a positive relation between tax avoidance and investment suggesting effects of either capital rationing or overinvestment. To distinguish between these two effects, I examine how the relation between tax avoidance and investment varies in settings where capital rationing or overinvestment is more likely to occur. My findings suggest that firms rely on the cash savings from tax avoidance to alleviate capital rationing.

Physiological traits that are biologically associated with feed efficiency may be useful indicator traits residual feed intake (RFI). The objective of this study was to examine the relationships between RFI, temperament, serum hormones and serum metabolites in growing heifers. A 4 yr study (n = 114-119 heifers/yr) was conducted with Brangus heifers (Initial BW = 271 ± 26 kg) that were weaned for 25.5 ± 8.6 d prior to high roughage diet adaptation (ME = 2.0 Mcal/kg DM). Individual dry matter intakes (DMI) were measured using Calan gate feeders and BW measured at 7-d intervals during the 70-d studies. RFI was calculated as the residual from the linear regression of DMI on mid-test BW0.75 and average daily gain (ADG). Temperament scores and exit velocity (EV) were taken at 0-d. Temperament index (TI) was calculated as the average of EV and chute score. On 0-d, blood samples were collected and assayed for partial blood counts (WBC, RBC, hemoglobin, HB), metabolites (total protein, TP; glucose; creatinine; blood urea nitrogen, BUN; β-hydroxybutyrate, BHB) and hormones (cortisol; insulin-like growth hormone I, IGF-I). Across all heifers, RFI was positively correlated with DMI (0.70) and feed:gain (0.59). Heifers with low RFI (< 0.5 SD from mean RFI 0.00 ± 0.71 kg/d) consumed 16 percent less DMI and had 16 percent lower feed:gain than heifers with high RFI (> 0.50 SD from mean RFI). RFI was weakly correlated (P < 0.05) with WBC (0.15), HB (-0.11), total protein (-0.10), BUN (0.10), creatinine (-0.11) and BHB (0.13). Hemoglobin and BHB were weakly correlated with all feed efficiency traits except feed conversion ratio (FCR). No phenotypic correlation was found between cortisol and IGF-I with RFI. Temperament was not correlated with RFI. Cortisol, creatinine and glucose were moderately correlated with all temperament traits. Low TI heifers (calm) had significantly higher Final BW, ADG and DMI than high TI heifers. Calm animals had significantly lower cortisol, HB, creatinine and glucose and higher BHB. These results suggest that the temperament and serum metabolites evaluated in this study have limited utility as indicator traits for RFI in growing heifers.

Three experiments were conducted (1) to develop and characterize polyclonal antibodies against ovine adipocyte plasma membranes (APM), (2) to evaluate the effect of administering the developed antibodies to lambs on lamb growth and carcass characteristics, and (3) to investigate the possibility of using the developed antibodies to identify antigenic components on ovine APM that are tissue, species and possibly site specific. In Experiment 1, the developed antibodies showed a high rate of reactivity to APM and cross reacted with plasma membranes (PM) from liver, kidney, heart and erythrocytes. Adsorption of antisera with either liver PM or erythrocyte PM for 6 h resulted in a significant reduction in antisera cross-reactivity to liver or erythrocyte PM, respectively, with little effect on its specific reactivity to APM or cross-reactivity with PM of the other tissues tested. The antisera also reacted in different affinities to APM from sheep, pig and rat. The antisera also showed differential binding to APM isolated from different anatomical locations. In Experiment 2, five wether lambs were assigned to either a control or treatment group to study the effect of passive immunization with the antisera immunoglobulin (ASig) on lamb growth and carcass characteristics. Treatment with ASig resulted in a significant (P<.OS) reduction of 45% in wet perirenal fat weight, and of 1.8 and 0.8% in subcutaneous and perirenal lipid content, respectively. ASig immunization also significantly (P<.O5) reduced blood plasma non-esterified fatty acid without adversely affecting blood plasma triglycerides or packed cell volumes (hematocrit). Animals immunized with ASig also showed a significant (P<.OS) reduction in average weight daily weight gain, but this effect was not associated with any adverse effect on efficiency of carcass production. Moreover, passive immunization tended to improve protein accretion and efficiency of nitrogen utilization. In Experiment 3, the developed antisera immunoglobulins recognized three unique ovine APM components, in comparison with plazma membranes from liver, kidney, heart or RBC, with molecular weights of 70, 106 and 110 KD, and showed to react more intensely with APM antigenic components that are in common with PM of the tissues tested. Antisera immunoglobulins recognized just two (44, 46 KD) antigenic components on porcine APM that are shared with those of ovine APM but did not react with any component on APM of either rat or chicken. / Graduation date: 1990

The objective of this research was to characterize the performance of a downflow bubblecontact (DBCA) hypolimnetic aerator — Speece Cone-. The effect of two key design factors, inlet water velocity and the ratio of gas flow rate to water flow rate on four standard units of measure was examined: (a) the Oxygen Transfer Coefficient, KLa, corrected to 20°C, KLa₂₀ (hr­-¹), (b) the Standard Oxygen Transfer Rate, SOTR (g0₂.hr­-¹) (c) the Standard Aeration Efficiency, SAE (gO₂kWhr­-¹), and (d) the Standard Oxygen Transfer Efficiency, SOTE (%). Two sources of oxygen, Pressure Swing Adsorption (PSA) oxygen (87% purity) and air, were compared. KLa₂₀, SOTR, and SAE increased with an increase in the ratio of gas flow rate to water flow rate for both air and oxygen, over a range of 0.5% to 5.0%; while SAE deceased. An increase in inlet water velocity resulted in a decrease in KLa, corrected to 20°C, SOTR, and SAE, but an increase in the SOTE. Treatments on air showed similar, but much less dramatic effect of the gas flow rate to water flow rate ratio and water inlet velocity on KLa₂₀, SOTE, SAE, and SOTE, when compared to treatments on PSA oxygen. The best performance was achieved with an inlet water velocity of 6.9-7.6 ms­-¹ and oxygen flow rate to water flow rate ratio of about 2.5%. At this combination, the SOTE was about 66-72%.

Esta tesis contribuye a la literatura sobre la eficiencia y la productividad adoptando un enfoque gerencial. Las aplicaciones empíricas se dirigen hacia el sector bancario español, industria que ha atraído un gran interés debido su crecimiento post-desregulatorio. Además, es probable que este interés se intensifique, pues la reciente crisis financiera ha generado la necesidad de reestructurar el sector y de introducir nuevas estrategias competitivas. Tres temas constituyen los capítulos centrales de esta tesis: (1) La identificación y el análisis de conglomerados bancarios a través de la descomposición de un indicador de productividad y eficiencia, (2) La formalización de nuevas propuestas para realizar benchmarking basado en índices de la productividad total de los factores (PTF), (3) La evaluación de los beneficios potenciales de fusiones y adquisiciones a través de fronteras de eficiencia convexas y no convexas. En el contexto de los grupos estratégicos, el primer capítulo analiza la productividad y la eficiencia de los bancos y las cajas de ahorros españolas durante 1998-2006. Para ello se utiliza el indicador de productividad de Luenberger, que se descompone de forma similar a los índices de Malmquist. La PTF se descompone en cambios tecnológico y de eficiencia. A su vez, esté ultimo se descompone en cambios de eficiencia pura, de escala y de congestión. Los resultados empíricos muestran que las mejoras de productividad se deben en parte a la innovación tecnológica y explican cómo se desarrolla la competencia entre los bancos y las cajas de ahorros. Posteriormente, los componentes del Luenberger se utilizan como inputs en un análisis de conglomerados. Las interpretaciones de los grupos resultantes se hacen a través de las principales diferencias entre los varios indicadores de productividad y eficiencia. Finalmente, siguiendo la literatura sobre grupos estratégicos, se introducen diversos ratios bancarios para alcanzar nuevas interpretaciones de los grupos. El segundo capítulo propone nuevas perspectivas de benchmarking para el análisis de la PTF. Se vincula así la literatura sobre el benchmarking con los estudios de eficiencia y productividad. Concretamente, varias especificaciones del índice de PTF de Hicks-Moorsteen están adaptadas a las siguientes perspectivas de evaluación comparativa: (1) estática, (2) de base y unidad fijas, y (3) cambio dinámico de la PTF. Estos enfoques utilizan empresas fijas y/o tecnologías de base como referencia. A diferencia de la mayoría de los índices de productividad, el índice de Hicks-Moorsteen estándar siempre proporciona resultados factibles e interpretables desde la PTF. Mediante estas especificaciones, un gerente puede evaluar diferentes aspectos comparativos entre la empresa y sus competidores. Las implicaciones del análisis propuesto se ejemplifican en el sector bancario español durante 1998-2006. El tercer capítulo analiza las potenciales mejoras de eficiencia obtenidas de las operaciones de fusiones y adquisiciones, un tema ampliamente estudiado pero a menudo con resultados no concluyentes. Especulamos que esto se debe parcialmente al supuesto tecnológico de convexidad que puede condicionar los resultados. Por ello, ambas tecnologías, convexas y no convexas, se utilizan para analizar las fusiones y adquisiciones y revelar las reducciones de exceso de costes debido a ineficiencias técnicas y de escala. Asimismo, se establecen condiciones ex ante para alcanzar las potenciales reducciones de costes. Utilizando una muestra de 32 procesos de fusión ocurridas durante 1988-2006 en el sector bancario español, se encuentran que significativas reducciones de costes se producen a partir de los dos años después de la fusión. Además, se muestra como las estimaciones no convexas son más próximas a los movimientos de costes observados. Estos hallazgos son relevantes dada la actual ola de fusiones provocada por la crisis financiera, y deberían ser complementados con investigaciones sobre eficiencia de gama y economías de diversificación. / This dissertation contributes to the efficiency and productivity literature by adopting a managerial focus to address gaps in previous research. In doing so, it uses existing methodological tools, further developed and adapted to current needs. These proposals are applied to the Spanish banking sector, an industry that attracted vast amounts of interest due to its post-deregulation growth phase. Against the background of the recent financial crisis, this attractiveness for research of (Spanish) banks will probably escalate, as new consolidation policies from central institutions will induce novel competitive strategies. Three topics represent the core chapters of this thesis: (1) The identification and analysis of bank performance groups through decomposed productivity and efficiency indicators; (2) New proposals of total factor productivity (TFP) benchmarking via technology-based index numbers; (3) The assessment of potential gains from mergers and acquisitions (M&As) through convex and non-convex efficiency frontiers. In the framework of the strategic groups' literature, the first chapter analyses changes in the productivity and efficiency of Spanish private and savings banks between 1998 and 2006. By adapting a decomposition of the Malmquist productivity indices, it proposes similar components decomposing the Luenberger productivity indicator. TFP is disentangled into technological and efficiency changes. The latter is then decomposed into pure efficiency, scale and congestion changes. Empirical results show that productivity improvements are partially due to technological innovation and explain how the competition between private and savings banks develops. Consequently, the Luenberger components are used as cluster analysis inputs. Thus, economic interpretations of the resulting performance groups are made via key differences in TFP components. To end with, as suggested by the strategic groups' literature, insights are gained by linking these performance groups with banking ratios. Second, by proposing a benchmarking framework to analyze TFP, a gap is filled between the benchmarking literature and multi-output efficiency and productivity studies. Different specifications of the Hicks-Moorsteen TFP index are tailored for specific benchmarking perspectives: (1) static, (2) fixed base and unit, and (3) dynamic TFP change. These approaches assume fixed units and/or base technologies as benchmarks. In contrast to most productivity indices, the standard Hicks-Moorsteen index always leads to feasible results and TFP interpretations. Through the defined specifications, managers can assess different facets of the firm's strategic choices in comparison with relevant benchmarks and thus have a broad background for decision making. An analysis for the Spanish banking industry between 1998 and 2006 illustrates the feasibility and managerial implications of the proposed framework. The third chapter scrutinizes the potential efficiency gains from M&As, a widely researched topic, but often linked to inconclusive results. We speculate that this is partly caused by the employed methodological assumptions. Among them, the assumption of a convex technology can be an important influence on the results. Thus, both convex and non-convex technologies are used to reveal post-M&As cost excess gains due to scale and technical inefficiencies. Ex ante conditions for achieving potential cost reductions are devised and then tested ex post on a sample of 32 Spanish banking M&As that occurred between 1988 and 2006. Empirical results show that significant cost excess reductions appear two years after the merger event. Furthermore, it is illustrated that the non-convex estimations are closer to the movements in the observed costs. These are interesting findings in view of the upcoming merger wave and should be complemented with research on scope efficiency and economies of diversification.