Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Kirby S. Chapman / The increasingly strict air emission regulations may require implementing Non-Selective Catalytic Reduction (NSCR) systems as a promising emission control technology for stationary rich burn spark ignition engines. Many recent experimental investigations that used NSCR systems for stationary natural gas fueled engines showed that NSCR systems were unable to consistently control the exhaust emissions level below the compliance limits. Part of this thesis is devoted to show the results from the field testing of three engines working in natural gas gathering stations located in the “Four Corners” area. These three engines are retrofitted with NSCR systems. Emissions and engine operating data were monitored for more than one year. Data collected from October 2007 through December 2008 shows significant variation in emissions levels over hours, days, and longer periods of time, as well as seasonal variations. As a result of these variations, simultaneous control of NOx and CO below the compliance limit was achieved less than fifty percent of the monitored time. Modeling of NSCR components to better understand, and then exploit, the underlying physical processes that occur in the lambda sensor and the catalyst media is now considered an essential step toward improving NSCR system performance. The second portion of this thesis focuses on modeling the lambda sensor that provides feedback to the air-to-fuel ratio controller. Correct interpretation of the sensor output signal is necessary to achieve consistently low emissions level. The goal of this modeling study is to improve the understanding of the physical processes that occur within the sensor, investigate the cross-sensitivity of various exhaust gas species on the sensor performance, and finally this model serves as a tool to improve NSCR control strategies. This model simulates the output from a planar switch type lambda sensor. The model consists of three modules. The first module models the multi-component mass transport through the sensor protective layer. Diffusion fluxes are calculated using the Maxwell-Stefan equation. The second module includes all the surface catalytic reactions that take place on the sensor platinum electrodes. All kinetic reactions are modeled based on the Langmuir-Hinshelwood kinetic mechanism. The third module is responsible for simulating the reactions that occur on the electrolyte material and determine the sensor output voltage. The details of these three modules as well as a parametric study that investigates the sensitivity of the output voltage signal to various exhaust gas parameters is provided in the thesis.

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Heartwater is a major threat to livestock in Africa due to its high mortality rate. The intracellular nature of the causative organism, Cowdria ruminantium, makes it difficult to study, hence an effective and user-friendly vaccine has been extremely difficult to obtain. Two C. ruminantium DNA libraries have recently been constructed, the lambda GEM11 bacteriophage DNA library and the lambda ZAPII bacteriophage DNA library, and this has lead to a renewed search for protective genes that could be used as a vaccine against heartwater. In this study, several molecular techniques including PCR, cloning and sequencing were used to identify genes in the lambda GEM11 bacteriophage DNA library that code for proteins, which could be used as vaccines to protect susceptible animals against heartwater. The lambda GEM11 library was screened with a rickettsial secretory protein gene sequence, known as seeD. One positive colony was selected from which the bacteriophage DNA was isolated. The C. ruminantium DNA was amplified from the bacteriophage DNA by using PCR and C. ruminantium-specific primers. The C. ruminantium DNA was screened with Mycoplasma, bovine and Cowdria DNA probes. The amplified DNA was subeloned into two vectors and the clones were screened by restriction analysis to identify clones containing inserts. The appropriate clones were sequenced and overlapping sequences matched, ordered and aligned. Two sequences were continuous with a short sequence of unidentified bases in between. Oligonucleotide primers were designed to amplify the DNA sequence between the two contiguous sequences. This led to the identification of the entire sequence of the C. ruminantium genome contained within the bacteriophage plaque. The single contiguous sequence was analysed and the putative protein-coding sequences were obtained and compared to DNA sequences of known organisms using the BLAST program. Five open reading frames were identified with homology to genes encoding specific proteins in bacteria. Two open reading frames showed homology to the genes encoding the transporter proteins, FtsY and the ABC transporter, and three open reading frames were found to be homologous to genes encoding the essential enzymes dethiobiotin synthetase, pro lipoprotein diacylglycerol transferase and the putative NADH-ubiquinone oxidoreductase subunit. The five open reading frames encode for genes, which are essential for the normal functioning of the C. ruminantium organism. However, these open reading frames might not be effective for use in a DNA vaccine since none of the open reading frames showed homology to obvious genes that could play a role in immunity and therefore confer protection. The open reading frames can be used in mutagenesis studies to produce attenuated strains of the organism that possess mutated versions of these proteins. These attentuated strains could be used for the vaccination of cattle, and thereby confer protection against viable pathogenic C. ruminantium isolates. / AFRIKAANSE OPSOMMING: Hartwater is 'n bedreiging vir vee in Afrika weens die hoë mortaliteitssyfer verbonde aan die siekte. Die intrasellulêre aard van die organisme wat hartwater veroorsaak, Cowdria ruminantium, bemoeilik navorsing aangaande die organisme. Dit het tot gevolg dat 'n effektiewe en gebruikersvriendelike entstof moeilik bekombaar is. Daar is onlangs sukses behaal met die konstruksie van twee C. ruminantium DNA genoteke, die lambda GEM11 bakteriofaag genoteek en die lambda ZAPII bakteriofaag genoteek. Dit het gelei tot 'n herlewing in die soektog na beskermende gene, wat in 'n entstof teen hartwater gebruik kan word. In hierdie studie is verskeie molekulêre tegnieke insluitende PKR, klonering en geenopeenvolging bepaling, gebruik om gene te identifiseer in die lambda GEM11 bakteriofaag genoteek wat kodeer vir proteïene wat in entstowwe gebruik kan word as beskerming teen hartwater. Die secD geen is gebruik om die lambda GEM11 bakteriofaag genoteek te sif. Een positiewe plaak is gevind waarna die DNA uit die bakteriofaag plaak geïsoleer en die C. ruminantium DNA vanuit die bakteriofaag plaak geamplifiseer is deur gebruik te maak van PKR en spesifieke C. ruminantium inleiers. Die C. ruminantium DNA is gesif met Mycoplasma, bees en Cowdria radioaktief gemerkte DNA peilers. Die C. ruminantium DNA is vervolgens in twee vektore gekloneer. Die klone is gesif deur middel van restriksie analise. Die DNA volgorde van die klone is bepaal en twee ononderbroke sekwense is geïdentifiseer met 'n gaping in die middel tussen die twee sekwense. Oligonukleotied inleiers is daarna ontwerp om die geenopeenvolging van die gaping tussen die twee sekwense te vul. Hierdeur kon die volledige geenopeenvolging van die genoom van C. ruminantium wat in die lambda GEM 11 bakteriofaag plaak voorkom, bepaal word. Hierdie volledige geenopeenvolging is vervolgens geanaliseer en die oop leesrame wat daarin voorkom geïdentifiseer. Vyf leesrame is gevind om homologie met gene wat kodeer vir proteïene wat in bakterieë voorkom, te toon. Twee leesrame het homologie met die gene wat kodeer vir transport proteïene, FtsYen die ABC transporter getoon, en drie leesrame het homologie met gene wat kodeer vir die essensiële ensieme detiobiotin sintetase, prolipoproteïen diasielgliserol transferase en die NADHubikinoon oksidoreduktase subeenheid getoon. Dié vyf leesrame het die potensiaal om as entstowwe gebruik te word aangesien al vyf leesrame kodeer vir gene wat 'n belangrike rol speel in die oorlewing van die C. ruminantium organisme. Alhoewel die leesrame moontlik nie so effektief sal wees in 'n DNA entstof nie, toon dit potensiaal om in mutasieeksperimente gebruik te word. Organismes wat die gemuteerde weergawe van die geen besit sal nie-funksionele proteïene produseer, wat 'n invloed kan hê op die normale fisiologiese funksies van die organisme en dus sal lei tot 'n minder virulente organisme. Die geattenueerde organisme kan moontlik gebruik word om diere te immuniseer en daardeur immuniteit aan diere lewer wat beskerming sal bied teen patogeniese C. ruminantium isolate.

Bacteriophage holins are a diverse group of proteins that are responsible for the spontaneous and specifically-timed triggering of host cell lysis. The best-studied holin, S105 of phage lambda, is known to form lesions, or “holes”, in the inner membrane of E. coli which are large enough to allow the endolysin through to the periplasm. S105 has been studied extensively by both genetic and biochemical approaches; however, little is known about the mechanism of hole formation or the structure of the lambda holin and its inner membrane lesion. An in vitro system for reconstituting hole formation by S105 was developed in which liposomes containing a self-quenched fluorophore served as artificial cell membranes (1-2). Upon delivery of solubilized S105 to the liposomes, an increase in fluorescence was observed, indicating that the fluorophore within the liposomes had escaped into the surrounding media via an S105-mediated hole in the membrane. This in vitro system, which has been optimized in this work, has been a valuable biochemical tool for analysis and reconstitution of the pathway to S105 hole formation in the cell membrane. Due to the difficulty associated with over-expression and purification of toxic membrane proteins, there are no solved structures of bacteriophage holins. Sample preparation and experimental conditions for NMR spectroscopy were optimized and structural information about a lambda holin mutant protein was obtained. Specifically, micellar contacts of transmembrane domain regions versus water contacts of the C-terminal region, secondary structure, and backbone dynamics were determined. Cryo-electron microscopy was used to visualize the inner membrane lesions formed by phage holins [lambda] S105, P2 Y, and T4 T. Therefore, the large holes initially seen in cells expressing S105 are not specific to the lambda holin, nor to class I holins. The S105 holes average ~340 nm (3), and are the largest membrane lesions ever observed in biology. They are stable at their original size, and are not localized to a specific region of the membrane. In addition, missense mutants of S105 were used to correlate hole size, protein accumulation, and lysis timing in a current model for the S105 hole formation pathway.

Thèse de doctorat : Informatique : Vandoeuvre-les-Nancy, INPL : 2005. / Titre provenant de l'écran-titre. Bibliogr.

Thèse de doctorat : Informatique : Nancy 1 : 2008. / Titre provenant de l'écran-titre.

Thèse doctorat : Informatique : Nancy 1 : 2007. / Titre provenant de l'écran-titre.

Thesis (Ph. D.)--University of California, San Diego, 2002. / Vita. Includes bibliographical references (leaves 146-152).

Thèse de 3e cycle : Informatique : Lille 1 : 1998. / Résumé en français et en anglais. Bibliogr. p. 103-112.

Even though lambda calculus (λ-calculus) and combinatory logic (CL) appear to be equivalent, they are not. As yet we do not have a reduction in CL which corresponds to β-reduction in λ-calculus. There are three proposals but they all have few problems one of which is the lack of a complete characterization of CL-terms corresponding to λ-terms in β-normal form. Finding such a characterization for any of the three proposals appears to require a lot of examples which are tedious and time consuming to develop by hand. For this reason, a computer program to do reductions and abstractions of CL-terms would be useful. This thesis is about an attempt to write such a program. The program that we have does not yet work for the three proposals but it works for βη-strong reduction. Coding this program turned out to be much harder than anticipated. Dr. Robin Cockett developed a semantic translation which helped in coding the program but his semantic translation needs to be extended to all three proposals to obtain the program originally desired and that needs a lot of research. / v, 96 leaves ; 29 cm

Thesis (M.S.)--Bowling Green State University, 2008. / Document formatted into pages; contains vi, 48 p. : ill. Includes bibliographical references.