Semiconductor device simulators have generally been based on either classical or semi-classical approaches. In these approaches, the Poisson's equation is solved with either the current continuity equation or the Boltzmann transport equation. Methods based on quantum mechanics have been generally very computer intensive, and thus until recently not much favored. However, with the availability of faster and more powerful computers this picture is changing. As the physical dimensions of the semiconductor devices are reduced, the assumptions made in the classical and the semi-classical approaches become invalid and the simulation results become inaccurate. For such cases, quantum mechanical concepts must be introduced to provide accurate simulation results. This dissertation presents the proof of concept of a semiconductor device simulator based on the quantum mechanical principals. The simulation technique is based on the self consistent solution of the Poisson's and time independent Schrodinger wave equation for a 1-D finite differenced grid. The applicability of the technique to a 2-D finite differenced grid is also presented. The simulation is performed by first solving for the Fermi energy distribution inside the simulation domain. The initial estimates about the carrier concentrations are developed from the Fermi energy distribution. Based on the carrier concentrations, the potential distribution inside the device is updated using the Poisson's equation. The updated potential distribution is then used in the time independent Schrodinger's equation and the carrier wave vectors are thus determined. The carrier wave vectors, along with appropriate density of state function and distribution function are used to update the carrier concentrations. For the 1-D case, the density of state function is based on a single dimension of a three dimensional volume with the assumption that the density of states is the same for all the three dimensions. The distribution function used is the Fermi-Dirac distribution function. The new carrier concentrations thus computed are then substituted back into the Poisson's equation, and self consistency is obtained when minimum error criteria has been met. The device simulator has the capability of simulating heterojunctions semiconductor devices fabricated from elemental semiconductors such as Si and Ge, as well as binary and tertiary compound semiconductors. / Ph. D.

The objective of this work is to solve a model one dimensional duct design problem using a particular optimization method. The design problem is formulated as an equality constrained optimization, called All at once method, so that the analysis problem is not solved until the optimal design is reached. Furthermore, the block structure in the Jacobian of the linearized constraints is exploited by decomposing the variables into the design and flow parts. To achieve this, Sequential quadratic programming with BFGS update for the reduced Hessian of the Lagrangian function is used with Variable reduction method which preserves the structure of the Jacobian in representing the null space basis matrix. By updating the reduced Hessians only of which the dimension is the number of design variables, the storage requirement for Hessians is reduced by a large amount. In addition, the flow part of the Jacobian can be computed analytically. The algorithm with a line search globalization is described. A global and local analysis is provided with a modification of the paper by Byrd and Nocedal [Mathematical Programming 49(1991) pp 285-323] in which they analyzed the similar algorithm with the Orthogonal factorization method which assumes the orthogonality of the null space basis matrix. Numerical results are obtained and compared favorably with results from the Black box method - unconstrained optimization formulation. / Ph. D.

As a first step toward improving creeping bentgrass (Agrostis palustris Huds.) via genetic engineering, this study was conducted to develop genetic transformation systems in creeping bentgrass. Establishment of embryogenic cell cultures is a prerequisite for crop improvement via genetic engineering. A protocol for initiating and maintaining embryogenic callus and suspension cultures in creeping bentgrass was developed by substantially modifying and combining a few existing protocols. A high frequency of plant regeneration was obtained following this protocol. Several factors affecting electroporation efficiency were studied using transient expression assay of the reporter uuid gene encoding B-glucuronidase (GUS). Increases in plasmid DNA resulted in increases in GUS activity. Maximal GUS activity was observed at field strength of 950 V/cm, protoplast density of 2 x 10⁶/ml, and KCl concentration of 125 mM in the electroporation buffer. Information obtained from this study facilitated optimization of electroporation conditions. To identify a 5’ regulatory sequence conferring a high level of transgene expression in creeping bentgrass, the effect of six different 5’ regulatory sequences on transient gene expression was studied in electroporated creeping bentgrass protoplasts. The cauliflower mosaic virus (CaMV) 35S promoter was least active; whereas the rice actin 1 gene 5’ sequence was most active among the six sequences tested. Ranked in order of activity (high to low), the other four 5’ sequences were: 1) the CaMV 35S promoter plus the maize alcohol dehydrogenase 1 gene (Adh1) intron 6; 2) the 5’ sequence of the maize ubiquitin gene (Ubi-1), 3) the maize Adh1 promoter and its intron 1, and 4) the 35S promoter plus the Adh1 intron 1. Stable transformation of creeping bentgrass was conducted via particle bombardment and electroporation using a plasmid, pZO1052, containing the reporter B-glucuronidase (uidA) gene and the selectable marker hygromycin phosphotransferase (hph) gene under the control of CaMV 35S promoter plus the maize Adh1 intron 6. Putative transformants were selected by culturing cells on medium containing hygromycin. Transgenic plants and calli were obtained following particle bombardment. The frequency of putative transformants was 4.6 hygromycin-resistant colonies per bombardment. Integration of the transgenes was confirmed by Southern blot hybridization. A high frequency of escapes, however, occurred in the transformant selection following electroporation, which resulted in inefficient transformant recovery. In this study, efficient genetic transformation systems using particle bombardment were established. Use of these systems will facilitate the improvement of creeping bentgrass. / Ph. D.

DNA-DNA hybridization experiments were used to examine the genetic variation that has accumulated with the North American Biological Species (NABS) of Armillaria. Forty strains including nine of the ten NABS and A. tabescens were used in this study. The normalized percent hybridization values ranged from 80%-100% similarity within a given biological species and ranged from 30%-85% among the biological species, The NPH data was summarized with UPGMA clustering analysis to give four main clustering groups, two were homogeneous and two were heterogeneous, The first included A. tabescens; the second included A. mellea; the third included A. calvescens, A. gallica, A. sinapina, NABS IX, and NABS X; the fourth included A. gemina and A. ostoyae. One cluster of two A. gallica strains shared greater similarity with NABS X than it had to four other conspecific strains, The NPH data and estimates of genome size (genetic complexity) was analyzed using a stoichiometric approach to calculate equivalents of homologous DNA and low copy repetition frequencies. Reciprocal NPH values did not predict relative genome size as expected, However, as the relative genome size increases, the equivalents of homologous DNA increases in the same proportion. This suggests that as an Armillaria genome increases in total complexity (novel sequences), certain ancestral sequences are duplicated in proportion the increase in total genetic complexity, This interpretation of the data is discussed with respect to interspecific hybridization, diploidy, and chromosomal evolution including alloploidy, aneuploidy, and chromosomal length polymorphisms. / Ph. D.

The adsorption of a number of Brønsted acids of differing strengths has been studied on stoichiometric and defective Sn0₂ (110) surfaces. The extent of dissociation of these acids depends on the surface composition and the strength of the acid. Two crystallographically inequivalent types of oxygen vacancies can be introduced onto SnO0₂ (110) surfaces, and the kinetics of the reactions of Brønsted acids is influenced by the number and type of oxygen vacancies present on each surface. The site requirement for dissociation of Brønsted acids has been described as a coordinatively unsaturated cation and an available anion. On the Sn00₂ ( 110) surfaces studied, this site requirement was seen to be a necessary but not sufficient condition for dissociation. In contradiction to the generally accepted idea that the presence of defects increases reactivity, the most defective SnO₂ (110) surface considered showed the lowest activity for dissociation for all adsorbates studied. / Ph. D.

Supercritical extraction (SFE) has most often been linked to the use of modified or unmodified CO₂ for the recovery of relatively non-polar analytes from solid matrices. The objective of this research was to expand current supercritical fluid (SF) techniques to the recovery of analytes from non-traditional matrices. SFE with three unique matrices was completed. Small mammals are often used in drug toxicity studies. Pharmaceutical dosage verification in the animal feed is a requirement in these studies. Atovaquone, a drug used in the treatment of aids related pneumonia, was successfully recovered from rat feed with supercritical CO₂. Drug recoveries of ≥ 90% were achieved with a range of drug concentrations from 0.03% to 1.1% in the feed. The second phase of the investigation studied the recovery of acyclovir, an antiviral agent, from Zovirax® 5% ointment. This recovery required a radically different approach from all previous SFE techniques, as the analyte was completely insoluble in the supercritical fluid. This unique situation led to the development of "Inverse SFE", where the ointment matrix was extracted and the drug analyte was retained in the extraction vessel. Included in the investigation were the effects of temperature, modifier, drug recovery techniques and length of extraction. Employing a 20 minute inverse SFE, 99% of the acyclovir was recovered from the ointment. Increasing regulation, disposal costs and environmental issues have fueled concerns over the use of chlorinated organic solvents. Currently, over 50% of the samples regulated by the EPA have liquid matrices that have been traditionally analyzed using these solvents. The implementation of solid phase extraction (SPE) has significantly reduced the amount of organic solvent utilized for the extraction of liquid matrices; however, further reduction is desired. The third phase of this work concerned the elution of a SPE disk with SF wherein the disk had been used to concentrate pollutants from fresh and brackish water. Initially, this research focused on the quantitation of polyaromatic hydrocarbons (PAHs) from distilled water. The analytes were deposited onto a solid phase extraction disk and eluted with a SF. The proper method of quantitation, relative versus absolute, was also investigated. Optimization of the SF elution in relation to time, temperature, flow rate, and pressure while maintaining quantitative recoveries was performed. A three step, 27 minute SF elution method resulted from this effort. Recoveries were ≥ 90% for all the 16 PAHs studied. A chamber temperature of 80°C with liquid flow rate of 2 mL/minute was employed. The study was expanded to 39 EPA Method 525.1 analytes in distilled water. Although system contamination proved to be a problem, all but four analytes were quantitatively recovered according to EPA criteria. SF elution studies of brackish water matrices from the Chesapeake Bay indicated suspended sediment was responsible for water retention on the surface of the SPE disk. The retained water interfered with analyte recovery. More thorough drying techniques resulted in the recovery all but five analytes meeting EPA criteria. / Ph. D.

This dissertation is a collection of papers investigating objectives and incentives in financial markets. The first essay (Chapter 2) deals with the endogenous determination of credit history, credit-worthiness, loans and efforts by borrowers over time. A financial market with adverse selection and moral hazard is analyzed. Facing the adverse selection, lenders are not able to offer separate contracts to different types of borrowers. However, knowing borrowers' credit histories, lenders are able to assign different credit worthiness to borrowers that have different credit histories, and offer different contracts to different groups. It is shown that if borrowers' credit rating is too low, they make low effort to repay their debts. As a borrower acquires a good credit history and has his credit-rating upgraded above a certain point, it becomes worthwhile for him to choose high effort. A low quality borrower may make high effort in early periods in order to build up a good credit history and obtain better terms in the future contracts then shift back to the low effort even though his project continues to succeed when he approaches the end of his life. / Ph. D.

Relative levels of task uncertainty associated with various CPA firm services were examined in this study. Additionally, tests to determine whether systematic variation occurs at the office or at the firm level were conducted. Multiple measures of task uncertainty were developed. Multiple analysis of variance techniques were used to analyze data drawn from audit, tax, actuarial and benefits consulting, and general business consulting engagements. Data was drawn from two office of one Big Six CPA firm. As expected, after comparing audit and tax engagements from two office, the null hypothesis that there was no difference in task uncertainty levels between offices on either service type could not be rejected. The null hypothesis that no difference in levels of task uncertainty between the four service types exist was rejected. This result was also consistent with expectations. These findings provide empirical support for an assumption made by previous researchers that the individual firm is the appropriate level for analysis. Additionally, results suggest that, at the firm level, differences in levels of task uncertainty do exist. In general, audit and tax services appear to involve lower levels of task uncertainty than do consulting services; however, it should be noted that significant differences also existed between consulting services. The implications of these results for future research are that the firm appears to be the appropriate organizational level for examining research questions related to CPA firms. Also, consulting services need to be considered not as one service type, but potentially as distinct from one another. Future research involving other Big six firms as well as second and third-tier firms could lead to greater generalizability of these results / Ph. D.

The effectiveness of an adsorption filter in retaining bacteria present in milk was examined. Skim milk and whole milk (100ml) were separately filtered through a 47mm adsorption filter. No significant change in total solids, total fat, and solids-not-fat percentages of skim and whole milk permeates was observed after filtration. Adsorption of Pseudomonas fluorescens at target concentrations of 103 , 102 , and 101 cells/ml was determined in 100ml of dairy standard methods buffer, nutrient broth, whole milk, and skim milk. The average percentage bacterial retentions were 95 ± 5.5%, 95 ± 2.6%, 28 ± 22.1%, and 62 ± 15.5%, respectively. A treatment was developed for milk to increase the bacterial retention of ~ fluorescens after filtration. The preferred treatment for 100ml of skim milk involved the following final concentrations (v/v): 0.80% disodium ethylenediamine-tetraacetic acid, 0.02% sodium dodecyl sulfate, pH to 7.5 with 1N sodium hydroxide. The average bacterial retention of ~ fluorescens using the treatment was 91 ± 7.1%. Enumeration of bacteria adsorbed to the filter was then conducted using impedance microbiology. When milk was inoculated with ~ fluorescens at target concentrations of 103 , 102 , and 101 cells/ml, an average log bacterial increase of 1.4 ± 0.1 (25x) was obtained. This method will allow for rapid detection of microorganisms in milk by increasing microbial load in the tested sample and eliminating the need for pre-enrichment. / Ph. D.

Filaments of the desiccation-tolerant cyanobacterium Nostoc commune are embedded within, and distributed throughout, a dense glycan sheath. Analysis of the glycan of field materials and of pure cultures of N. commune DRH1 through light and electron microscopy, immunogold-labelling and staining with dyes, revealed changes in the pattern of differentiation in glycan micro-structure, as well as localized shifts in pH, upon rehydration of desiccated field material. A Ca/Si rich external (pellicular) layer of the glycan acts as a physical barrier on the surface of N. commune colonies. A purified fraction (> 12 kDa) of an aqueous extract of the glycan from desiccated field material contained glucose, N -acetylglucosamine, glucosamine, mannose and galactosamine with ratios of 3.1 : 1.4 : 1 : 0.1 : 0.06, respectively. Ethanol extracts of N. commune contained trehalose and sucrose and the levels of both became undetectable following cell rehydration. Elemental analysis of glycan extracts showed a flux in the concentrations of salts in the glycan matrix following rehydration of desiccated colonies. Intracellular cyanobacterial trehalase was identified using immunoblotting and its synthesis was detected upon rehydration of desiccated field cultures. Water-stress proteins (Wsp; molecular masses of 33, 37, and 39 kDa are the most abundant proteins in glycan), a water soluble UV-AlB-absorbing pigment, the lipid-soluble UV-protective pigment scytonernim, as well as two unidentified cyanobacterial glycoproteins (75 kDa and 110 kDa), were found within the glycan matrix. No evidence was found for either glycosylation, phosphorylation or acylation of Wsp polypeptides. NH2-terminal sequence analysis of the three proteins of Wsp were identical: Ala-Leu-Tyr-Gly-Tyr-Thr-Ile-Gly-Glu-Gln-X-Ile-Gln- Asn-Pro-Ser-Asn-Pro-Ser-Asn-Gly-Lys-Gln. An unidentified 68-kDa protein, the second most abundant protein in aqueous extracts of the glycan, was isolated and its N-terminal sequenced was determined: Ala-Phe-lle-Phe-Gly-Thr-Ile-Ser-Pro-Asn-Asn-Leu-Ser-Gly- Thr-Ser-Gly-Asn-Ser-Gly-Ile-Val-Gly-Ser-Ala. Gene bank searches with these sequences, and an internal sequence ofWsp (Glu-Ala-Arg-Val-Thr-Gly-Pro-Thr-Thr-Pro-Ile-Asp), identified homologies with various carbohydrate-modifying enzymes. Purified Wsp polypeptides associate with 1,4-β-D-xylanxylanohydrolase activity that was inhibited specifically by Wsp antiserum. In the absence of salt, Wsp polypeptides, and the water-soluble UV -A/B-absorbing pigments, form multimeric complexes through strong ionic interactions. The role of the glycan, and the protein and pigments that reside within it, in the desiccation tolerance of N. commune is discussed with respect to structure/function relationships. / Ph. D.