Doctor of Philosophy

dissertationThe chemical-looping technology is quickly becoming an attractive alternative for the combustion of fossil fuels in energy production. With the rapid growth in the anthropogenic production of carbon dioxide (CO2) due, in large part, to the combustion of fossil fuels, it is becoming increasingly important to identify technologies that are capable of producing energy, at the same rate as traditional fossil-fuels units, while serving in a secondary capacity of managing emissions. Among the materials suggested for use in chemical-looping, copper-oxide has emerged as a front runner. Materials such as copper oxide allow the direct combustion of solid fuels, without an intermediary gasification step, by spontaneously decomposing from cupric oxide (CuO) to cuprous oxide (Cu2O), liberating free oxygen in the process. The rate at which these particles decompose can be as much as 50 times faster than the rates of gasification. This work provides the academic community with results geared toward the production and implementation of copper-based oxygen carriers by: 1. Developing novel oxygen carrier materials and, 2.Developing models describing both the oxidation and decomposition of copper oxide-based materials. It has been determined that the decomposition of copper-oxide is well described by a global reaction rate for a wide range of copper oxide-based oxygen carrier materials. This global reaction rate suggests that the activation energy of decomposition that best predicts reaction rates of the different CuO-based materials is 62 kJ/mol and that the rate law has a zero order dependence on the concentration of the solid carrier. The modeled oxidation kinetics of Cu2O to CuO for two different oxygen carrier materials is presented. Unlike the simple case of decomposition of CuO, the oxidation of Cu2O is highly dependent on the solid concentration. During oxidation, the volume change of the solid is about a 5% increase. This causes a pore-blocking effect which is observed at low temperatures (below 700°C). However, at higher temperatures (above 800°C), this effect is not apparent. These two regimes are best described by two different kinetic models: pore-blocking kinetics is used for the lower temperature regime while nucleation/growth kinetics, given by Avrami-Erofeev, is used to model the higher temperature regimes

Static post-Newtonian equivalence of GR and gravity with a dynamical preferred frame

A generally covariant extension of general relativity (GR) in which a dynamical unit timelike vector field is coupled to the metric is studied in the asymptotic weak field limit of spherically symmetric static solutions. The two post-Newtonian parameters known as the Eddington-Robertson-Schiff parameters are found to be identical to those in the case of pure GR, except for some non-generic values of the coefficients in the Lagrangian.Comment: 13 pages; v.2: minor editing, signs corrected, version to appear in PRD; v. 3: signs corrected in eqn (3

Metapopulation Viability of Swamp Rabbits in Southern Illinois: Potential Impacts of Habitat Change

Swamp rabbits (Sylvilagus aquaticus) in southern Illinois exist as a metapopulation due to fragmentation of the bottomland hardwood forests in which they live. This fragmentation makes their persistence in Illinois uncertain. We used population viability analysis (PVA) to estimate the probability of persistence of the swamp rabbit metapopulation in Illinois, using a habitat suitability map we created and life history parameters drawn from the literature. We varied the parameters used in our PVA from 50% to 150% of the initial value to compare their effects on extinction risk and to direct future management and research. We tested the effects of potential habitat loss and fragmentation by 1) removing patches individually and in groups from the analysis and by 2) adding 60, 120, and 180 m to the edge of all patches. We also tested the potential effect of dispersal corridors by increasing dispersal between connected patches. Under baseline conditions, the model suggests a 0% chance of quasiextinction (90% metapopulation decline) of swamp rabbits within 25 (or even 50) years. Changes in fecundity values and the effects of catastrophic flooding had the greatest effect on extinction risk, and changes in no other parameter yielded any appreciable impact. Removing the largest patches from the population increased the 25- year risk of extinction to 4%, whereas any other modifications to the habitat did not change the extinction risk. We suggest that managers focus on sustaining habitat quality, particularly upland habitats adjacent to occupied bottomland hardwood forests to improve the likelihood of swamp rabbit persistence in Illinois

Assessing Cross anisotropy of Small-Strain Stiffness Using the Resonant Column apparatus

Almost all soils exhibit cross-anisotropic stiffness to some extent. However, measuring the cross anisotropic properties of soils is difficult because of the need to determine the 3 independent stiffness parameters Eν, Eh, Gνh, and the associated Poisson’s ratios, nνh and nhh. Current techniques that are employed, for example using bender elements or field geophysics, are not always reliable, whilst preparing specimens in different orientations and subsequent testing using standard laboratory techniques has practical constraints. The resonant column is a laboratory apparatus that has been extensively used to measure the torsional stiffness (Gνh). Relatively recent development has also allowed the Stokoe resonant column to measure Young’s modulus from flexural excitation of the specimen. The apparatus has also been used to determine Eν through axial oscillation. Thus a modified resonant column apparatus can apply four different excitations (flexure in two directions, torsion and longitudinal excitation) to a soil. This paper reports a series of dynamic finite element numerical simulations of physical tests in the resonant column apparatus, carried out to model both the apparatus and a cross-anisotropic soil specimen. Forward modelling has been carried out to determine the impact of different degrees of anisotropy on the resonant frequencies of ‘specimens’ with their axes of anisotropy aligned in different directions relative to the vertical axis of the apparatus. Methods of determining the elastic parameters from these data are assessed

High-Spatial-Resolution OH PLIF Visualization in a Cavity-Stabilized Ethylene-Air Turbulent Flame

High-spatial-resolution OH planar laser-induced fluorescence was measured for a premixed ethylene-air turbulent flame in an electrically-heated Mach 2 continuous-flow facility (University of Virginia Supersonic Combustion Facility, Configuration E.) The facility comprised a Mach 2 nozzle, an isolator with flush-wall fuel injectors, a combustor with optical access, and an extender. The flame was anchored at a cavity flameholder with a backward-facing step of height 9 mm. The temperature-insensitive Q1(8) transition of OH was excited using laser light of wavelength 283.55 nm. A spatial filter was used to create a laser sheet approximately 25 microns thick based on full-width at half maximum (FWHM). Extension tubes increased the magnification of an intensified camera system, achieving in-plane resolution of 40 microns based on a 50% modulation transfer function (MTF). The facility was tested with total temperature 1200 K, total pressure 300 kPa, local fuel/air equivalence ratios of approximately 0.4, and local Mach number of approximately 0.73 in the combustor. A test case with reduced total temperature and another with reduced equivalence ratio were also tested. PLIF images were acquired along a streamwise plane bisecting the cavity flameholder, from the backward facing step to 120 mm downstream of the step. The smallest observed features in the flow had width of approximately 110 microns. Flame surface density was calculated for OH PLIF images

Acetaminophen use and risk of asthma, rhinoconjunctivitis and eczema in adolescents : ISAAC Phase Three

Rationale: There is epidemiological evidence that the use of acetaminophen may increase the risk of developing asthma. Objectives: To investigate the risk of asthma and other allergic disorders associated with the current use of acetaminophen in 13- to 14-year-old children in different populations worldwide. Methods: As part of the International Study of Asthma and Allergies in Childhood (ISAAC) Phase Three, 13- to 14-year-old children completed written and video questionnaires obtaining data on current symptoms of asthma, rhinoconjunctivitis, and eczema, and a written environmental questionnaire obtaining data on putative risk factors, including acetaminophen use in the past 12 months. Measurements and Main Results: The primary outcome measure was the odds ratio (OR) of current asthma symptoms associated with acetaminophen use calculated by logistic regression. A total of 322,959 adolescent children from 113 centers in 50 countries participated. In the multivariate analyses the recent use of acetaminophen was associated with an exposure-dependent increased risk of current asthma symptoms (OR, 1.43 [95% confidence interval, 1.33–1.53] and 2.51 [95% confidence interval, 2.33–2.70] for medium and high versus no use, respectively). Acetaminophen use was also associated with an exposure-dependent increased risk of current symptoms of rhinoconjunctivitis and eczema. Conclusions: Acetaminophen use may represent an important risk factor for the development and/or maintenance of asthma, rhinoconjunctivitis, and eczema in adolescent children.peer-reviewe

High-Resolution OH and CH2O Visualization in a Premixed Cavity-Anchored Ethylene-Air Flame in a M = 0.6 Flowfield

OH and CH2O were imaged in a premixed, cavity-anchored, ethylene-air turbulent flame using a high resolution planar laser-induced fluorescence (PLIF) system. The electrically-heated, continuous flow facility (UVa Supersonic Combustion Facility, Configuration E) consisted of a Mach 2 nozzle, an isolator with fuel injectors, a test section with a cavity flame holder and optical access, and an extender. Standard test conditions comprised total temperature 1200 K, total pressure 300 kPa, local equivalence ratio near 0.4, and local Mach number near 0.6. OH PLIF data was also collected for a case with reduced total temperature and another with reduced equivalence ratio. OH and CH2O were excited in separate experiments with light sheets at 283.55 nm and 352.48 nm, respectively. A light sheet of approximate thickness 25 ?m illuminated the stream-wise midplane. This plane was imaged for 120 mm downstream of the backward-facing step. The intensified camera system imaged OH with magnification 1.97, a square 6.67 mm field of view, and in-plane resolution of 39 ?m. The smallest observed OH structures observed were approximately 100 ?m wide. The CH2O PLIF image signal was much weaker; the smallest observed structures were approximately 200 ?m wide. Composite fluorescence images were computed for the observed area

AntiJen: a quantitative immunology database integrating functional, thermodynamic, kinetic, biophysical, and cellular data

AntiJen is a database system focused on the integration of kinetic, thermodynamic, functional, and cellular data within the context of immunology and vaccinology. Compared to its progenitor JenPep, the interface has been completely rewritten and redesigned and now offers a wider variety of search methods, including a nucleotide and a peptide BLAST search. In terms of data archived, AntiJen has a richer and more complete breadth, depth, and scope, and this has seen the database increase to over 31,000 entries. AntiJen provides the most complete and up-to-date dataset of its kind. While AntiJen v2.0 retains a focus on both T cell and B cell epitopes, its greatest novelty is the archiving of continuous quantitative data on a variety of immunological molecular interactions. This includes thermodynamic and kinetic measures of peptide binding to TAP and the Major Histocompatibility Complex (MHC), peptide-MHC complexes binding to T cell receptors, antibodies binding to protein antigens and general immunological protein-protein interactions. The database also contains quantitative specificity data from position-specific peptide libraries and biophysical data, in the form of diffusion co-efficients and cell surface copy numbers, on MHCs and other immunological molecules. The uses of AntiJen include the design of vaccines and diagnostics, such as tetramers, and other laboratory reagents, as well as helping parameterize the bioinformatic or mathematical in silico modeling of the immune system. The database is accessible from the URL:

The Spectroscopic Orbit of the Evolved Binary HD 197770

We have used spectra taken between 1992 and 1997 to derive the spectroscopic orbit of the eclipsing double-lined spectroscopic binary HD 197770. This binary has a period of 99.69 +/- 0.02 days and K amplitudes of 31.2 +/- 0.8 and 47.1 +/- 0.4 km s^{-1} for components A & B, respectively. The msin^{3}i values for A & B are 2.9 and 1.9, respectively, and are close to the actual masses due to the eclipsing nature of this binary. Both components of HD 197770 have spectral types near B2 III. This means both components are undermassive by about a factor of five and, thus, evolved stars. Additional evidence of the evolved nature of HD 197770 is found in 25, 60, and 100 micron IRAS images of HD 197770. These images show 2 apparent shells centered on HD 197770; a bright 60 micron shell with a 14' diameter and a larger (1.2 degeree diameter) bubble-like feature. At least one of the components of HD 197770 is likely to be a post-AGB star.Comment: will be published in the AJ (1998 June), also availible at http://snake.phys.lsu.edu/~gordon/papers/hd197770.htm

Structure of the first representative of Pfam family PF04016 (DUF364) reveals enolase and Rossmann-like folds that combine to form a unique active site with a possible role in heavy-metal chelation.

The crystal structure of Dhaf4260 from Desulfitobacterium hafniense DCB-2 was determined by single-wavelength anomalous diffraction (SAD) to a resolution of 2.01 Å using the semi-automated high-throughput pipeline of the Joint Center for Structural Genomics (JCSG) as part of the NIGMS Protein Structure Initiative (PSI). This protein structure is the first representative of the PF04016 (DUF364) Pfam family and reveals a novel combination of two well known domains (an enolase N-terminal-like fold followed by a Rossmann-like domain). Structural and bioinformatic analyses reveal partial similarities to Rossmann-like methyltransferases, with residues from the enolase-like fold combining to form a unique active site that is likely to be involved in the condensation or hydrolysis of molecules implicated in the synthesis of flavins, pterins or other siderophores. The genome context of Dhaf4260 and homologs additionally supports a role in heavy-metal chelation