Cotton seedling disease caused by Pythium ultimum Trow and Rhizoctonia solani Kühn occurs worldwide in soils ranging from pH 4.5 to 8.5. Studies with cotton have not yet established the relative importance of two classes of secondary metabolites synthesized by soilborne pseudomonads, siderophores (sid) (low molecular weight Fe⁺³ chelators) and antibiotics (ant), in the suppression of these pathogens. Greenhouse bioassays to screen for rhizosphere competent strains identified a single strain of Pseudomonas chlororaphis (L-850), that produced siderophores and multiple antifungal antibiotics, including one or more phenazines. A Tiff Image Analyzer (TIA) software program was developed that allowed assessment of wild-type (wt) L-850, and (ant) and (sid) mutant populations as a function of cotton root surface area (cm²) in the absence of soil irrigation. Bacterial density and distribution patterns on roots evaluated 22, 36, and 50 DAP, in two pathogen-free soils (pH 5.7, high Fe⁺³, high phosphorus (P); pH 8.0, low Fe⁺³, low P) indicated that populations of both wt and mutants persisted after day 22 at levels between log 4.6 (lower laterals) to log 6 cfu/cm² (upper tap) even as total root area increased 122% from day 22 to 50. Population densities of all strains were consistently 1/8 to 3/4 log unit lower in the pH 5.7 soil on the lower tap and upper lateral roots, respectively. The loss of siderophore production appeared to enhance the rhizosphere competence of strain L-850. For greenhouse trials with three pathogen inoculum densities (low, intermediate, high) protection against preand postemergence damping-off (phase 1) and hypocotyl/root rot of young plants (phase 2) by the (sid) and wt strains was similar (P = 0.05) whereas, protection by seed treatment with the (ant) mutant was reduced. The level of suppression provided by L-850 was equivalent (P = 0.05) to the standard fungicide at low and intermediate pathogen pressure. These studies demonstrated a minimum contribution of siderophores in the biological control of cotton seedling disease and established a significant role for antibiotic biosynthesis over a range of soil physical and chemical characteristics. / Ph. D.

Ed. D.

M.S.

"Architecture may be many things: ie. there is no one thing that is Architecture." As tired as this phrase may be, it is extremely valid nonetheless. From Frampton's <i>Critical Regionalism</i> to Derrida's <i>Deconstruction</i>, this declaration is rendered indisputable. Whatever the architecture does become, however, it can do so only from a boundary [as in both Heiddeger's suggestion of a <i>beginning</i> and in the Greek belief that that is where a thing "begins its presencing"].₁ It is the boundary--the WARP [from Hertzberger]--that permits the opportunities for making to come into being. "Making" can thereby be considered to be the other critical component--the WEFT--in this process of becoming. This thesis is the beginning of a search for such a method of thinking in architecture. 1. Heidegger, Martin. <i>Poetry, Language, Thought</i> (Harper & Rowe, Publishers, Inc., 1971), p. 154. / Master of Architecture

Ph.D.

With increasing global competitiveness, top management of multinational corporations have realized that their resources cannot be effectively and efficiently transformed into marketable outputs without having managers who have global perspectives and a familiarity with the company's interest in overseas operation. To create a management team with global perspectives, multinational firms are using expatriate managers to fill overseas managerial positions. In Pacific Asia, the region's economic growth has attracted tremendous investments in hotel development from multinational companies, and these companies are increasingly hiring foreign professionals and managers to fill their business needs. However, while some expatriates have been very successful in Asia, many others encountered inherent problems related to overall satisfaction in the foreign environment which may lead to failures in their assignments. Failures in overseas assignments or expatriate turnovers are very costly to multinational companies. Current literature indicates a void in the research on predictors of hotel expatriate satisfaction and the relationship between satisfaction and turnover. The purpose of this study is to examine the antecedents (predictors) and consequences (turnover) of hotel expatriate satisfaction in three Asian countries; China, Hong Kong, and Singapore. The study consisted of a mailed survey of the expatriate hotel managerial employees in the three countries, followed by compilation and statistical analysis of relevant data to obtain empirical results which are used to develop a model of antecedents and consequences of hotel expatriate satisfaction. The findings from this study suggests that expatriate satisfaction can be predicted by five factors; (1) cultural adjustment, (2) skill variety, (3) role clarity, ( 4) participation, and (5) cross-cultural training. In addition, the research indicates that both expatriate job and general satisfaction relate to turnovers, and job satisfaction has stronger impact on expatriate's intention to quit. / Ph. D.

This dissertation utilizes content identifying methodologies based on preference and expected price ratings, and a free response format survey, to examine environmental factors that influence human perception of commercial landscapes and storefronts. Survey respondents rated scenes of commercial landscapes and storefronts according to their preference for the scene and their expected price of goods sold in the establishments depicted. Signs were removed from the scenes to permit evaluation of design characteristics in a context that is free from the external influence of information conveyed through product and retailer image. The respondents provided additional information about their shopping habits, shopping preferences, demographic background, and the scenes being rated. Preference and expected price ratings were analyzed using nonmetric factor analysis, to obtain dimensions or groupings of scenes which are the result of common stimuli or visual characteristics. The content or common stimuli of each dimension was then identified using information provided by the respondent. The relationship between the dimensions and respondent characteristics was then examined. A positive linear relationship was identified between preference and expected price ratings. This finding indicates that in the absence of signs, people tend to fall back on their preferences to make judgments about the price of merchandise sold in commercial landscapes. While there were commercial landscapes that were judged to offer low prices, those landscapes were also associated with the negative characteristics of poor service, poor quality and dangerous environments. The findings of this dissertation research provide evidence that reaffirms the importance of coherence, complexity, mystery and legibility in environmental perception, and supports prospect refuge theory. Respondents preferred commercial landscapes with interesting and involving environments. Storefronts that utilize angles, arcades, porticos, towers, and other forms of facade articulation were preferred. Likewise, visually rich and well . textured materials, such as brick, interlocking pavers and stamped concrete increased preference for commercial landscapes. Storefronts that utilize accent features, such as towers or awnings were found to have greater legibility, because these features assist in way finding. / Ph. D.

This dissertation is concerned with airport ground network operations and runway design problems. An aircraft landing simulation model is proposed to predict landing aircraft operations in airfield networks considering gate location and taxiway network information. By using the integrated simulation results, an improved dynamic programming model is established to solve the runway exit location problem. The simulation model uses aircraft kinematic functions coupled with individual parameters to describe the landing process. A multiobjective optimization and a shortest path algorithm are used to predict the aircraft exit choice and expected taxiway path in a runway-taxiway network. By recognizing pilot motivation during the landing process, several influencing factors such as terminal location, traffic density, runway and weather conditions are considered in the aircraft landing simulation. Random variables such as aircraft approach speed, deceleration rate and runway exit speed are created to represent the stochastic aircraft landing behavior by using a Monte Carlo sampling technique. The model results, with some simplifications, could be used to solve runway exit location problem by providing the expected distribution of aircraft landing distances and aircraft runway occupancy times. With real-time input data, the model could also provide information on aircraft exit choice, runway occupancy times and shortest taxiway path to an assigned terminal location for both the pilot and the air traffic controller in a ground traffic automatic control system. The dynamic programming model is based on previous research results with substantial improvements. Instead of only focusing on the runway configuration, the proposed model recognizes airline terminal location as an influence factor in the runway exit location problem and introduces this influence in the optimization procedure. An interactive computer program has been developed in C language on a RISC 6000 workstation to perform all these tasks. The choice of a workstation platform improves the performance of the dynamic programming algorithm when compared to personal computer solutions. / Ph. D.

Ph. D.

Ph. D.