Electrical crosstalk is becoming increasingly important as size shrinks and component densities increase in hybrid circuits. This occurs especially in multilayer thick film circuits. Crosstalk studies at high frequencies apply transverse electromagnetic (TEM) or quasi-TEM mode. However, the TEM mode theory is not applicable at low frequencies and low frequency-crosstalk is still a concern for circuit designers. In this research, crosstalk equations were derived in a simpler way, which can be used for low frequency applications such as automotive electronics. Test patterns were designed in both single and multilayer substrates in order to study crosstalk parameters such as line separation, line width, ground distance, ground type, and multilayer thickness. The mutual inductance and the mutual capacitance were calculated in order to use them in predicting crosstalk for particular transmission line geometrical structures. A conventional technique was used for the mutual inductance, and a new conformal mapping technique was developed for the mutual capacitance. Frequency dependence of crosstalk was confirmed by the equations developed. There is good agreement between the experimental mutual inductance and mutual capacitance and the calculated values. Finally, crosstalk prediction ( simulated by combining crosstalk equations with calculated mutual parameters ) fits well with the measured values. / Ph. D.

In plants, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR, EC 1.1.1.34) is a key enzyme regulating biosynthesis of phytosterols, plant growth regulators, carotenoids, antimicrobial defense compounds, and numerous other isoprenoids. To initiate molecular studies of HMGR in relation to defense responses in plants, we utilized yeast HMGR cDNA sequences to isolate tomato genomic sequences encoding HMGR. The nucleic acid sequence and gene structure was determined. The tomato HMGR gene (HMG2) contains four exons separated by three introns and encodes a polypeptide of 602 amino acid residues (about 64,714 Da). Two membrane-spanning regions are contained in the NH₂-terminus of the HMGR polypeptide. The COOH-terminus shares significant homology with HMGR sequences from different species. Genomic Southern hybridization analyses reveals that tomato contains 3 to 4 HMGR genes. The HMGz2 gene cross-hybridizes to mRNA of about 2.7 kb which is highly induced in tomato cells treated with fungal elicitors and in stems, leaves, or roots stressed by wounding suggesting that the HMGz2 is a defense-related gene in tomato. Hybridization with a gene specific probe indicates that the HMG2 gene is induced specifically during defense responses and is distinct from the gene(s) expressed during fruit development and ripening. / Ph. D.

For the first time, the bonding patterns of specific carbon atoms in woody plant lignin have been identified in situ. This was accomplished by administering and incorporating into the lignin fraction of Leucaena leucocephala, a tropical hardwood, ferulic acid enriched with ¹³C at either the 1-, 2-, or 3-C atom of the side chain. The plants were grown hydroponically over extended periods of time (28 days) under aseptic conditions in media containing the ferulic acid precursor, and then the tissues were examined by solid-state ¹³C NMR spectroscopy. Consequently, resonances due to the bonding patterns of the specific carbon atoms were determined. These resonances differ substantially from similarly labelled synthetic dehydrogenatively polymerized (DHP) lignin in both spectral profile and relative peak intensities. Subsequent studies using phenylalanine as precursor showed that it was better translocated into the aerial portions of the plant, and that its uptake did not result in distortion of lignification in those tissues, both in amount and monomeric composition. Consequently, the difference spectra obtained by ¹³C NMR analyses of phenylalanine-treated plants confirmed and extended the results obtained with ferulic acid. Evidence for the conversion of both precursors to the monolignols was shown by the difference spectra of [1-¹³C]-precursor-fed tissues, where the dominant resonance at 61-63 ppm is consistent with substructures containing the hydroxymethyl functionality. The spectrum obtained with roots administered [1-¹³C] ferulic acid showed the presence of a minor resonance (170-174 ppm) attributable to carboxylic acids/esters. By allowing the plant to undergo further metabolism by growing in hydroponic media without the precursor, these signals disappeared from the resulting spectrum. The first direct evidence for the dominance of the β-O-4’ linkage of lignin in situ was shown by the appearance of the resonance at 83 ppm corresponding to this substructure in both [2-¹³C] ferulic acid-treated roots and [2-¹³C] phenylalanine-treated roots and stems. Evidence for the occurrence of α-O-carbohydrate or α-O-aryl linkage in intact plant tissues was obtained in the spectra of tissues administered [3-¹³C] ferulic acid and [3-¹³C] phenylalanine. The effect of horseradish peroxidase/H₂O₂ in organic medium (dioxane/aqueous acetate buffer, pH 5, 95:5) on dehydrogenatively polymerized (DHP) lignin was reinvestigated. We found no evidence for vigorous depolymerization of DHP lignin under these conditions, contrary to claims made by Dordick, Marletta and Klibanov (1986, Proc. Natl. Acad. Sci. USA 83:6255-6257). Furthermore, we did not detect ferulic acid as a degradation product following treatment of DHP lignin with HRP/H₂O₂. Both coniferyl alcohol and DHP lignin were used in incubation experiments to determine effects of lignin peroxidase from the white-rot fungus Phanerochaete chrysosporium and H₂O₂ on these substrates. Gel filtration chromatography showed that polymeric materials of high molecular weights were the result of these treatments. Incubation of [1-¹³C], [2-¹³C] and [3-¹³C] coniferyl alcohol with lignin peroxidase/H₂O₂ resulted in products similar to-DHP lignins prepared by horseradish peroxidase/H₂O₂ with respect to occurrence of identical resonances in corresponding solution-state ¹³C NMR spectra. Consequently, the role of polymerization of low molecular weight phenolics as a mechanism for detoxification was ascribed to these fungal peroxidases. / Ph. D.

This qualitative case study addressed the question, “What strategies and tactics do people use to access intuition in solving complex, ill-structured problems?” Such problems are not routine, well-defined, or solved by immediate application of well-known procedures or decision rules. A comprehensive literature review revealed a paucity of empirical data on accessing intuition during problem solving. Additionally, while some posited a relationship between ill-structured problems and intuitions, no studies existed linking the two. This study explored people’s specific actions at the moment when an overall solution becomes apparent to the problem solver. It focused on both the conscious actions people take to access their intuition (strategies) and on the conscious or unconscious skills, clusters of related skills, or procedures (tactics) they use (Gerber, 1983), as well as underlying tacit processes (Fischbein, 1987). Participants were 11 human resource managers. This group was chosen because its members frequently encounter complex, ill-structured problems or help others focus on how to solve such problems. Specific individuals were recommended by colleagues who considered them to be articulate and interested in intuition. They completed journals to document the moment of solution and participated in follow-up, in-depth interviews. To ensure internal validity, participants acted in the role of “co-researchers.” They reviewed manuscripts, journals, and interviews for accuracy and reviewed written narratives to ensure that their statements had been understood. Two corraborated the process of category construction. A qualitative content analysis of journal results indicated that in seven instances intuitions occurred when participants were with others and that these seven were listening in some fashion at the moment of solution. Further analysis, which incorporated the interviews, indicated that actions most frequently taken at the moment of intuition included immersion, searching, thinking—working on task, undirected thinking, making connections, and listening. Whether a given action was a Strategy, tactic, or tacit process depended on how deliberately people acted and how aware they were of their actions. Results also showed that problems were ill-structured and that intuitions had characteristics consistent with those identified by Fischbein (1987). Finally, the study found that, for the participants in this case study, the dynamics of intuition can be summed up with the following proposition: A propelling concern to solve a complex problem leads to continuous search and spontaneous combustion. Implications for future research suggest the need for a conceptual framework for studying intuition; extended research in the workplace and other settings, examining especially instances when people are with others at the moment of solution; a more in-depth investigation of actions to access intuition, focusing on specific actions such as listening as well as the sequencing of all actions; and inquiry into how people’s values and beliefs affect their actions. It is recommended that practitioners join in research efforts as well as engage learners in an exploration of their own actions to access intuition during problem solving. / Ed. D.

An investigation of the application of nucleophilic aromatic substitution by the SRN 1 mechanism of halobenzenesulfonamides and related compounds towards the synthesis of 1,2-benzothiazine I,I-dioxides is reported. 3-Substituted and 3,4- disubstituted 2<i>H</i>-l,2-benzothiazine l,l-dioxides were prepared in moderate to good yields via the photostimulated reaction of 2-halobenzenesulfonamides with ketone enolates. It was observed that with certain ketone enolates reduction to yield benzene sulfonamide competed with the substitution reaction. The presence of β-hydrogen atoms was a common structural feature of ketones used in reactions in which reduction competed with substitution. It was also observed that the amount of reduction product isolated increased as a function of the number of β-hydrogen atoms present on the ketone enolate. It was found that 2-bromo and 2-iodobenzenesulfonamide exhibit comparable reactivity with ketone enolates that do not possess β-hydrogen atoms. However, a marked decrease in the reactivity of 2-bromobenzenesulfonamide was observed when β-hydrogen atoms were present on the ketone enolate. / Ph. D.

The parameters controlling column flotation have been investigated using laboratory and pilot-scale flotation cells. It was determined that column recovery is a function of flotation rate constant, axial dispersion, retention time and fractional air hold-up within the cell. Mathematical expressions have been developed which describe each of these parameters and the manner in which they respond to changing column geometry and flow conditions. Based on the data and mathematical expressions developed in the laboratory and pilot-scale testing, a scale-up procedure has been developed for column flotation. Unlike other column scale-up approaches, this procedure incorporates the four primary parameters governing column recovery (i.e., axial dispersion, flotation rate constant, retention time and air fraction) along with carrying capacity limitations to provide a complete scale-up of the entire column. Based on test work conducted in a 2-inch laboratory column, scale-up predictions were made and validated for 30-inch and 8-foot diameter columns. The scale-up procedure has been incorporated into a computer package for making predictions from laboratory data. / Ph. D.

Raman scattering and ultraviolet-visible reflectivity have been used to characterize the structural and electronic changes that occur in GaAs during ion implantation and subsequent annealing. In this work, the damaged structure is modelled as an amorphous GaAs matrix embedded with GaAs microcrystals. The longitudinal-optic (LO) Raman-line characteristics were monitored to determine the amorphous volume fraction, the average microcrystal diameter and, for the annealed samples, the carrier concentration. An oscillator analysis of the reflectivity spectra, along with the effective medium approximation, was carried out to determine the linewidths of the interband peaks and the amorphous volume fraction in the damage layer. To determine damage depth profiles, spectra were taken as a function of the amount of material removed via chemical etch. A new method of interpreting reflectivity spectra was developed to deal with the etchant-induced roughness. This roughness reduced the reflectivity by a constant factor in the region between 4.5 and 5 eV. The ratio between reflectivities at 4.55 and 4.75 eV was monitored to determine qualitatively the amount of damage. The annealing studies show that structural recovery occurs at a lower temperature than that for which electrical activation occurs. The depth profile of a sample annealed at 400°C reveals that nucleation takes place not only at the boundary between the damaged and undamaged layers (i.e., "epitaxial regrowth") but also at the microcrystal/amorphous interfaces within the damage layer. The oscillator analysis of the dielectric properties was further developed, and a connection was established between the Strengths, positions, and linewidths of the interband oscillators and the shift in position of the LO Raman line. The results indicate that the static dielectric constant is independent of microcrystal size. A comparison between (211) and (100) oriented Si-implanted GaAs was done as well, showing greater near surface damage and a shallower total damage layer for the (211) samples. Finally, a method for characterizing damage, based on the observed shifts of the two-phonon ("2LO") Raman peak as the incident photon energy is varied around the E₁ interband energy (2.9 eV), has been developed. The results suggest that the total mass of the electron-hole pair involved in the scattering process increases even for large (>400 Å) microcrystals. The 525°C annealed sample had little damage, and was studied with this technique. / Ph. D.

The teacher dismissal process is of critical importance to educators involved in both administrative and teaching positions. The legal prerequisites, opinions, and cases have been frequently reviewed and presented in countless studies. This study was designed to examine the dismissal process from the perspective(s) of the participants involved in the procedure. The study investigated the question: Do commonalities exist surrounding the circumstances and personalities involved in teacher dismissal proceedings during the school years 1987-88, 1988-89, or 1989-90? The study consists of ten field studies randomly selected from Virginia school divisions indicating a teacher dismissal during the period school years 1987-90. Field interviews were conducted to develop each of the ten case studies. The data were analyzed in two ways. First, like job participants were compared across case studies to identify commonalities during their involvement in the teacher dismissal process. Secondly, a profile of these commonalities was developed to show a typical pattern of circumstances and personalities involved in the teacher dismissal process. The study revealed that eight of the ten cases were based on issues outside of classroom instructional problems. Six of the ten teachers facing dismissal were ethnic minorities. Nine of the ten superintendents and all ten of the principals in the study did not hire the teacher facing dismissal in the cases. Finally, none of the teachers facing dismissal in the case studies was an active participant in a plan for improvement or a work plan. / Ed. D.

The precombustion desulfurization of coal was investigated by photochemical methods and by the application of a novel pyrite depressant in froth flotation. Semiconductor photoelectrochemical catalysis was extensively examined. As much as 41% of the organic sulfur was removed and 72% overall desulfurization of micronized Illinois No. 2 coal was obtained. Zinc oxide, in colloidal suspension, produced a small increase in the overall desulfurization at longer reaction times when compared to direct photolysis. The major limiting factor in organic sulfur removal from coal appears to be accessibility rather than reactivity. Kinetic experiments conducted with the model organosulfur compound, dibenzothiophene, showed high photochemical reactivity with nearly complete conversion occurring in 5 minutes in a saturated solution at 25°C. Scanning electron microscopic examination of product coals showed empty casts in places once occupied by iron pyrite. Additionally, a novel process was developed for separating clean coal from metal sulfide minerals such as pyrite and marcasite. The process comprises depressing the metal sulfide minerals with a reagent resulting from the alkaline oxidation and polymerization of a polyphenol or a quinone, and selectively floating clean coal from the depressed metal sulfide minerals. The process was investigated using microflotation, conventional Denver cell flotation, and microbubble column flotation. Up to 90% pyritic sulfur rejection was achieved from a coal and coal pyrite synthetic mixture. The process efficiency is a function of pH with greater improvements generally occurring at acidic pH when compared with the results obtained in the absence of the quinonoid reagent. However, in the case of microbubble column flotation with micronized coals, the largest overall pyritic sulfur and ash rejection occurred under alkaline conditions. Data from x-ray photoelectron spectroscopy and calorimetry indicate the quinonoid reagent modified the surface properties of minerals by reversible adsorption. / Ph. D.

The range of polymeric materials containing the Si-O bond spans from the three-dimensional inorganic networks of silica (SiO₂), to linear high molecular weight polysiloxanes which display properties of both organic and inorganic materials. Part 1 of this dissertation describes the synthesis of three-dimensional inorganic SiO₂ networks and organic-inorganic hybrid networks using a low temperature solution technique known as the sol-gel process. During this process, hydrolysis and subsequent condensation of inorganic alkoxides (most often tetraethylorthosilicate, TEOS) in the presence of catalysts leads to the formation of three-dimensional SiO₂ networks. However, the strong acid or base catalysts typically employed in sol-gel reactions would also cause undesirable degradation of many organic modifiers, especially at higher temperatures required for the drying of the gels. A catalyst-free sol-gel process, based on tetramethyl orthosilicate (TMOS), the most reactive silicon tetra alkoxide in the series, was developed. The catalyst-free route provides an optimum reaction environment for the synthesis of organic-inorganic materials through copolymerization reactions. This concept will be exemplified by two organic-inorganic systems in which TMOS was used as the inorganic component while poly(dimethylsiloxane) and polyimide oligomers respectively, were employed as the organic component. The effect of such modifications on the surface and bulk properties of the inorganic SiO₂ networks was also investigated. Part 2 of this dissertation describes specific aspects associated with the synthesis of amine containing polysiloxane oligomers. A new molecular design which allows for independent control of molecular weight and amine functionalities was developed. The new synthesis involves anionic ring opening equilibrium copolymerization of the cyclic siloxane tetramer D₄ with a new cyclic siloxane monomer containing amine functionalities as pendant groups on silicon atoms. The effect of the bulky substituent {-CH₂CH(CH₃)CH₂NHCH₂CH₂NH₂} of the silicon atom on the position of thermodynamic equilibrium, and the extent of molecular weight and composition control in the linear polysiloxane oligomers was studied. / Ph. D.