Sequence analysis of the entire 3.5 kb <i>Hind</i>III genomic DNA fragment previously isolated from <i>Nostoc commune</i> UTEX 584 (Defrancesco and Potts 1988), determined the exact locations of the <i>nifU, nifH</i>, and <i>nifD</i> genes and identified two potential stem loop structures, a direct repeat, and an ORF that codes for a protein with a predicted amino acid sequence similar to that of myoglobin from <i>Paramecium caudatum</i>. The <i>N. commune</i> UTEX 584 myoglobin-like protein has a predicted length of 118 amino acids and molecular mass of 12,906 Da. A PCR copy of the gene (<i>glbN</i>) was cloned for overexpression of the protein. The recombinant protein was purified and used for spectral analysis and for the production of polyclonal antisera. Treatment of the recombinant protein with dithionite and CO resulted in spectral shifts characteristic of hemoproteins that bind oxygen. While some of the spectral characteristics are unique to the protein, in general the spectra were more like those of globins than cytochromes. Based on these characteristics and the sequence similarity to the P. caudatum mnyoglobin, we proposed the name cyanoglobin, with the gene designation glbN and the protein designation GlbN. Western analysis of GlbN expression was performed on N. commune UTEX 584 and two species of Anabaena (Anabaena sp. PCC 7120 and Anabaena variabilis). In N. commune UTEX 584 a protein with a molecular mass similar to that predicted for GlbN was detected. This protein was produced in increased amounts under the same growth conditions that resulted in increased production of nitrogenase reductase (the nifH gene product). No proteins of similar size to GlbN were detected in Anabaena sp. PCC 7120 or A. variabilis. A possible function of GlbN may be for oxygen storage, transport, or protection of the nitrogenase system. These functions as well as those of the direct repeat and the potential stem loop structures and their relationship to nitrogen fixation or other physiological processes in N. commune UTEX 584 require further analysis. / Ph. D.

This thesis presents the development of a multifaceted conceptual framework for discrete-event simulation and its implementation within an integrated visual simulation support environment (VSSE). The intertwined research objectives regarding the conceptual framework and the companion VSSE are presented. A literature review of related work is conducted. The core of the thesis describes the conceptual framework (called the DOMINO), the VSSE and each of the tools from its supporting toolset, and the VSMSL (Visual Simulation Model Specification Language). Three example model applications (bus route, traffic intersection, and branch operations examples) demonstrate the use of the VSSE and the underlying DOMINO. The thesis is evaluated using the research objectives as assessment criteria. The DOMINO is truly multifaceted. Both graphical and object-oriented, the DOMINO provides design and implementation guidance over the simulation model life cycle. The DOMINO is not restricted to specific problem domains but is independent of application domain. Several different perspectives for developing model component logic are available to modelers under the VSMSL. The VSSE demonstrates significant advances in integrated, automated support for model development which include graphical facilities for definition and specification and effective verification techniques. The VSSE underscores the contributions of the research effort and has helped to identify potential areas for future research. / Ph. D.

Three new computational procedures are presented for the simulation of incompressible wall-bounded turbulent flows. First, an integral method based on the strip integral method has been developed for the solution of three-dimensional turbulent boundary-layer flows. The integral equations written in a general form using non-orthogonal streamline coordinates include the turbulent shear stress at the upper limit of an inner strip inside the boundary-layer. The shear stress components are modeled using the Boussinesq assumption, and the eddy viscosity is defined explicitly as in differential methods. The turbulence modeling is not hidden in opaque empirical correlations as in conventional integral methods. A practical four-parameter velocity profile has been established based on the Johnston Law of the Wall using a triangular model for the crosswise velocity. Two strips are used to solve for the four unknowns: skin friction coefficient, wall crossflow angle, boundary-layer thickness, and location of maximum crosswise velocity. The location of maximum crosswise velocity proves to be a natural and adequate parameter in the formulation, but it is numerically sensitive and has a strong influence on the wall crossflow angle. Good results were obtained when compared to predictions of other integral or differential methods. Secondly, two computational procedures solving the Reynolds Averaged Navier-Stokes equations for 20 and 3D flows respectively have also been developed using a new treatment of the near-wall region. The flow is solved down to the wall with a slip velocity based on Clauser's idea of a pseudolaminar velocity profile. The present idea is different from the wall-function methods and does not require a multi-layer eddy viscosity model. The solution of the equations of motion is obtained by the Finite Element Method using the wall shear stress as a boundary condition along solid surfaces, and using the Clauser outer region model for the eddy viscosity. The wall shear stress distribution is updated by solving integral equations obtained from the enforcement of conservation of mass and momentum over an inner strip in the near-wall region. The Navier-Stokes solution provides the necessary information to the inner strip integral formulation in order to evaluate the skin friction coefficient for 2D flows, or the skin friction coefficient and the wall crossflow angle for 3D flows. The procedures converge to the numerically "exact" solution in a few iterations depending on the accuracy of the initial guess for the wall shear stress. A small number of nodes is required in the boundary-layer to represent adequately the physics of the flow, which proves especially useful for 3D calculations. Excellent results were obtained for the 2D simulations with a simple eddy viscosity model. 3D calculations gave good results for the turbulent boundary-layer flows considered here. The present methods were validated using well-known experiments chosen for the STANFORD conferences and EUROVISC workshop. The 2D numerical predictions are compared with the experimental measurements obtained by Wieghardt-Tillmann, Samuel-Joubert, and Schubauer-Klebanoff. For the 3D analyses, the numerical predictions obtained by the strip-integral method and the Finite Element Navier-Stokes Integral Equation procedure are validated using the Van den Berg-Elsenaar and Müller-Krause experiments. / Ph. D.

Motivated by concerns posed by college athletics and questions about the effectiveness of educational reform commissions, this study centered on two questions: specifically, How did the Knight Commission function to bring policy reform to college sports?; and, generally, How does an independent, temporary commission influence organizational change? Grounded in the reform commission literature and a conceptual framework developed from political science, policy science, and organizational change theories, the research design employed two approaches - one inductive and one deductive - to focus on five areas of inquiry. Political processes were pivotal in bringing change. A "policy window" developed from the confluence of new, supportive key actors, public opinion favorable to reform, and threats of Congressional intervention. The Commission's empowerment created a choice opportunity for long-involved stakeholders to reauthorize athletic governance reform. Prior to empowerment, key actors reached consensus on core values and reform approach. The Knight Commission's operation enhanced the authority of key actors with standing as policy makers. Although intellectual undertakings supported an image of objective rationality, the Commission served more as an inter-organizational governance tool. Cross-fertilization" resulting from Commissioners who served as "linking pins" (Likert, 1967) between political systems, united a broad coalition on a single plan. A reform model that buttressed higher education values and was embedded in long-accepted principles of governance manipulated the "policy space" in athletics to focus debate on its issues. Other Commission activities served to enhance its "subjective authority" (Barnard, 1938) - acceptance at the bottom of the organization. The study process utilized "partisan policy analysis" (Lindblom, 1968) to persuade operational-level stakeholders. The report recommendations advanced the largest perceived increment of policy change that would not threaten its "acceptance." The extensive publicity surrounding report release served to inform and prepare the bottom layer of involved organizations and the public for change suggested by a representative group of eminent policy leaders. With enhanced authority and concordance on reform agenda, cross-boundary members successfully initiated policy reform. The still-intact Knight Commission supported internal policy makers and became accepted as a legitimate provider of policy influence. / Ph. D.

The superoxide dismutase from a radiation-resistant bacterium Deinococcus radiodurans has been purified to electrophoretic homogeneity. The superoxide dismutase has a specific activity of 3300 units/mg and an apparent molecular mass of 43,000 daltons. The enzyme contains 1.5 gram-atom of manganese per mol dimer, and is composed of two identical subunits of 23,500 daltons. The enzyme rapidly loses its catalytic activity and metal content upon dialysis in denaturing reagent, guanidine hydrochloride, and the metal ion chelator 8-hydroxyquinoline. The denatured apoprotein was renatured upon removal of the denaturant by dialysis. The renatured apoprotein assumed a gross conformation similar to the native enzyme as indicated by fluorescence spectroscopy. The renatured apoprotein was reconstituted to the native specific activity upon addition of manganese in the absence of denaturant. The manganese econstituted enzyme contained 1.7 gram-atom of manganese per mol dimer, and had a specific activity of 3650 units/mg. Kinetic studies revealed that the reconstitution with manganese was pH-dependent, and was inhibited by competing metal ions (iron and zinc). / Ph. D.

Displacement fields from point-like defects are investigated by x-ray diffraction. The atomic volume changes in the interstitial compounds using crystallographic information has been found to correlate with the size of filled octahedral sites. Systematic correlations enable estimates to be made of the components of the dipole tensor for interstitials in octahedral sites for binary systems containing N, C, and 0 in V, Nb, Ta, Cr, Mo, W, and Fe lattices. X-ray diffraction analysis of the concentration and residual stress gradients in N implanted Mo crystals and Nb films show that the dominant source of internal strain arises from N located in octahedral sites. For Nb implanted at LNT, these distortion centers are aligned equally along three mutually perpendicular directions to maintain cubic symmetry. Large biaxial residual strains are developed after a 5at% implantation of N into Nb and Mo. Radiation damage is present as small vacancy and interstitial loops. A method was developed to obtain the orientation function for samples containing a fiber texture. A slit correction is included and the final results from this simplified approach are compared with the pole figure measured by direct x-scanning. Knowing the orientation function allows one to correct the integrated intensities to that for an ideal powder, thereby allowing thermal and static displacements to be obtained from textured samples. Anisotropic displacements about coherent Be rich GP zones were investigated in a Cull-at%Be alloy. The results indicate that the attenuation factor 2M which determines the relative integrated intensities of Bragg, quasiline, and static diffuse scattering can be expressed in a simplified form. Experimental data of 2M for aged Cu-Be samples show an anisotropy. The anisotropy increases with increasing aging time when the equiaxed-GP zones formed in the early stage collapse into platelike GP zones. / Ph. D.

Ceramic substrates play an important role in thick film hybrid microelectronic circuits. Existing substrates such as alumina and beryllia do not meet satisfactorily the desired requirements. The newly developed aluminum nitride (<i>AIN</i>) substrate shows a great deal of promise and potentially embraces the best qualities of alumina and beryllia. The objective of this dissertation is to study the electrical properties, thick film interaction, and environmental effects on <i>AIN</i> substrates, and also to examine the performance of this material for high power - high frequency hybrid thick film applications. In particular, wideband dielectric constant measurements of A1N and other ceramic substrates are performed, oxidization and humidity effects on surface properties of <i>AIN</i> are addressed, and short and long term aging effects on several circuit parameters are studied. To evaluate the performance of <i>AIN</i> in high power and high frequency applications, two circuits; an impulse generator and a power converter, are realized, tested and compared with those on alumina substrates. The thick film circuits realized on <i>AIN</i> perform considerably better than those on alumina. / Ph. D.

A partial-wave analysis of pion photoproduction data up to a photon lab energy of 1.8 GeV has been performed. Both energy-dependent and energy-independent solutions have been obtained. The energy-dependent parametrization incorporates the recently determined elastic pion nucleon scattering amplitudes in such a way as to satisfy unitarity and utilize the resonance structure contained in the pion nucleon elastic amplitudes. Starting from the energy-dependent solution, energy-independent partial-wave solutions are obtained at a set of energies from threshold to 1.8 GeV. The data base used in the analysis contains 11,911 data from the reactions. The predictions of our solution are compared with the experimental data and previous analyses. Suggestions are made for future experiments. A total of sixteen resonances exist in the energy range from threshold to 1.8 GeV. These resonance states are studied using our energy-independent solutions. Photon decay couplings to the sixteen resonances are extracted. These couplings are also compared with previous solutions and quark model predictions. / Ph. D.

This study examines intertemporal variation in the associations of accounting data with subsequent firm returns. A number of accounting research studies pool data indiscriminately across time and firms. Previous research has disclosed the nature and effects of cross-sectional dependencies in pooled data. On the other hand, intertemporal dependencies associated with real macroeconomic phenomena have not been widely researched. The objective of this study was to provide evidence as to whether accounting data's associations with subsequent firm returns systematically vary across recession-associated and expansion-associated valuation change periods. Eighty-two accounting ratios were examined for evidence of systematic variation in association across business cycle-associated valuation events. Analyses are conducted, using both simple and multiple regression. Business cycle effects on the predictive accuracy of regression models were also examined. / Ph. D.

The turbulent character of the supersonic wake of a linear cascade of fan airfoils has been studied experimentally using a two-component Laser Doppler Anemometer. The cascade was tested in the Virginia Polytechnic Institute and State University intermittent wind tunnel facility, where the experimental Mach and Reynolds numbers were 2.36 and 4.8 x 10⁶, respectively. In addition to mean flow measurements, Reynolds normal and shear stresses were measured as functions of cascade incidence angle and streamwise location in the near-wake and the far-wake. The extremities of profiles of both the mean and turbulent wake properties were found to be strongly influenced. by upstream shock-boundary-layer-interactions, the strength of which varied with cascade incidence. In contrast, the peak levels of turbulence properties within the shear layer were found to be largely independent of cascade incidence, and could be characterized in terms of the streamwise position only. This fact permitted the determination of the decay of the Reynolds shear stress, the production rate of turbulent kinetic energy, and the turbulent kinetic energy itself with streamwise location. / Ph. D.