title: Dust Flow Separator Type Electrostatic Precipitator For A Control Of Particulate Matter Emissions From Natural Gas Combustion

contributor:
Chang, J.  S.
Engineering Physics

subject: Electrostatic Precipitator, Natural gas combustion, Pollution, Dust flow separator, Environmental Scanning Electron Microscope

abstract:
Pollution problems have drawn worldwide awareness and become significantly
important now. Particulate matter (PM) emission is one of the key pollution issues.
Particulate matter has a significant impact on the environment and human health,
especially particle sizes that range below  10μm. Researches continuously work an
improvement of fine particulate matter collections emitted from all kinds of sources, such
as automobiles, industrial combustion, etc. Governments in many countries are planning
to regulate the PM emission from the existing PM_10 (particle diameter<10μm) to new
limits PM_2.5 (particle diameter<2.5μm) within the next few years. For this reason, present
PM control system needs to be improved.

The objective of this work is to develop a dust flow separator type electrostatic
precipitator (DFS-ESP) for the effective control of fine particulate matter emission from
natural gas combustions. The characteristic of PM emitted from natural gas combustion is
studied, and the performance of a DFS-ESP is evaluated by experiments and numerical
predictions.

An experiment was conducted for natural gas combustion exhaust flow rates from
2.5 to 9 Nm^3/h, ESP applied voltages from 0 to 30kV, and gas temperature from 80 to
160°C. A series of particle measurements were conducted at upstream, downstream and
middle of the DFS-ESP system by an optical particle counter for particle mass density,
and by condensation nucleate particle counter for particle size distributions and particle number density. Particle sampled from the natural gas combustion system was also
analyzed by an environmental scanning electron microscope (ESEM) technique. Flow
velocity profile and pressure drop of the DFS-ESP were measured by a Pitot tube and
diaphragm type pressure transducer, respectively.

The experimental results show that the particle size emitted from natural gas
combustion ranges from 17 to 300nm in diameter, and the volume density is
approximately from 5 x 10^8 #pt/m^3 to 5 x 10^9 #pt/m^3 depending on the combustion
conditions. The dust flow separator can concentrate 90% of fine particles in 1 to 3% of
the gas flow and divert it from the main flow to the ESP section where the particles can
be removed. In terms of overall particle collection efficiency, the DFS-ESP system can
remove up to 90% of the particles based on the number density. The pressure drop across
the DFS-ESP is observed to be lower than lPa for the present range of flow rate, which is
within acceptable limits for industrial applications.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Genetic Determinants of Rare Coding Variants on the Development of Early-Onset Coronary Artery Disease

contributor:
Pare, Guillaume
Biochemistry and Biomedical Sciences

subject: Rare Variants; Exome Sequencing; Next-Generation Sequencing; Genetics; Cardiovascular Disease; Early-Onset Coronary Artery Disease; Early-Onset Myocardial Infarction; Coronary Artery Disease; Myocardial Infarction; Early-Onset Coronary Artery Disease Genetics; Early-Onset Myocardial Infarction Genetics; Coronary Artery Disease Genetics; Myocardial Infarction Genetics; Mendelian Dyslipidemia; Familial Hypercholesterolemia; Rare Variant Association; Gene Risk Scores; Stem Cells; iPSC

abstract:
Background: Coronary Artery Disease (CAD) represents the leading cause of mortality and morbidity worldwide despite declines in the prevalence of environmental risk factors. This trend has drawn attention to the risk conferred by genetic variation. Twin and linkage studies demonstrate a profound hereditary risk for CAD, especially in young individuals. Rare genetic variants conferring high risk for extreme disease phenotypes can provide invaluable insight into novel mechanisms underlying CAD development.
Methods: Whole exome sequencing was performed to characterize rare protein-altering variants in 52 early-onset CAD (EOCAD) patients encompassing the DECODE study. The enrichment of Mendelian dyslipidemias in EOCAD was assessed through interrogation of pathogenic mutations among known lipid genes. The identification of novel genetic CAD associations was conducted through case-only and case-control approaches across all protein-coding genes using rare variant burden and variance component tests. Lastly, beta coefficients for significant risk genes from the European population in the Early-onset Myocardial Infarction (EOMI) cohort (N=552) were used to construct calibrated, single-sample rare variant gene scores (RVGS) in DECODE Europeans (N=39) and a local European CAD-free cohort (N=77).
Results: A 20-fold enrichment of Familial hypercholesterolemia mutation carriers was detected in EOCAD cases compared to CAD-free controls (P=0.005). Association analysis using EOMI Europeans revealed exome-wide and nominal significance for two known CAD/MI genes: CELSR2 (P=1.1x10-17) and APOA5 (P=0.001). DECODE association revealed exome-wide and nominal significance for genes involved in endothelial integrity and immune cell activity. RVGS based upon beta coefficients of significant CAD/MI risk genes were significantly increased in DECODE (z-score=1.84; p=0.03) and insignificantly decreased among CAD-free individuals (z-score=-1.61; p=0.053).
Conclusion: Rare variants play a pivotal role in the development early CAD through Mendelian and polygenic mechanisms. Construction of RVGS that are calibrated against population and technical biases can facilitate discovery of single-sample and cohort-based associations beyond what is detectable using standard methods.

abstract: Thesis

abstract: Master of Science (MSc)


title: Oxide and Oxide Fluoride Chemistry of Xenon(VIII), Xenon(VI), and Iridium

contributor:
Schrobilgen, Gary J.
Chemistry

subject:
Inorganic Chemistry
Fluorine
Noble-gas Chemistry
Xenon
X-ray crystallography
Raman spectroscopy
High-oxidation states
xenon trioxide
Lewis acid base adducts
supramolecular
haloxenates
bromine xenon bond
iridium oxide fluoride
iridium dioxide
perxenate
xenon tetroxide

abstract:
This Thesis extends our fundamental knowledge of high-oxidation-state chemistry and in particular compounds of Xe(VIII), Xe(VI), and Ir(V). The crystal structure of XeVIIIO4 was obtained and provides important information on this fundamentally interesting endothermic and shock-sensitive compound. Macroscopic amounts of XeO3F2 have been prepared for the first time. Although the low-temperature Raman spectrum of solid XeO3F2 exhibits some frequency shifts and band splittings of the bending modes, the spectrum is similar to the Raman spectrum of the previously reported matrix-isolated compound. The crystal structures of decomposition and byproducts resulting from the syntheses of XeO3F2 have been obtained for [XeF5][HF2]∙XeOF4 and XeF2∙XeO2F2.
The solid-state structure of xenon trioxide, XeO3, was reinvestigated by low-temperature single-crystal X-ray diffraction and shown to exhibit polymorphism that is dependent on crystallization conditions. The previously reported α-phase (orthorhombic, P212121) only forms upon evaporation of aqueous HF solutions of XeO3. In contrast, two new phases, β-XeO3 (rhombohedral, R3) and gamma-XeO3 (rhombohedral, R3c) have been obtained by slow evaporation of aqueous solutions of XeO3. The extended structures of all three phases result from Xe=O----Xe bridge interactions among XeO3 molecules that arise from the amphoteric donor-acceptor nature of XeO3. The Xe atom of the trigonal pyramidal XeO3-unit has three Xe---O secondary bonding interactions. The orthorhombic α-phase displays the greatest degree of variation among the contact distances and has a significantly higher density than the rhombohedral phases. The ambient-temperature Raman spectra of solid α- and gamma-XeO3 have also been obtained and assigned for the first time.
Xenon trioxide interacts with CH3CN and CH3CH2CN to form O3XeNCCH3, O3Xe(NCCH3)2, O3XeNCCH2CH3, and O3Xe(NCCH2CH3)2. Their low-temperature single-crystal X-ray structures show that the xenon atoms are consistently coordinated to three electron-donor atoms which result in pseudo-octahedral environments around their xenon atoms. The adduct series provides the first examples of a neutral xenon oxide bound to nitrogen bases. Energy-minimized gas-phase geometries and vibrational frequencies were obtained for the model compounds O3Xe(NCCH3)n (n = 1−3) and O3Xe(NCCH3)n∙[O3Xe(NCCH3)2]2 (n = 1, 2). The natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM), electron localization function (ELF), and molecular electrostatic potential surface (MEPS) analyses were carried out to further probe the nature of the bonding in these adducts.
	Xenon trioxide forms adducts with the polytopic nitrogen base ligands: hexamine, DABCO, 2,2’-bipyridine, 1,10-phenanthroline, and 4,4’-bipyridine. The adducts were conveniently synthesized in aqueous or CH3CN solutions and are stable at room temperature. The crystal structures of hexamine∙2XeO3, hexamine∙XeO3∙H2O, 2,2’-bipyridine∙XeO3, 1,10-phenanthroline∙XeO3, and 4,4’-bipyridine∙XeO3 have been determined by low-temperature single-crystal X-ray diffraction. The structures consist of XeO3 molecules bridged by the ligands to form extended supramolecular networks with Xe---N bonds which range from 2.634(3) to 2.829(2) Å.  Raman spectroscopy was used to characterize and probe the room-temperature stabilities of these adducts. The reaction of 1,4-diazabicyclo[2.2.2]octane (DABCO) with XeO3 in aqueous solutions yields thin, plate-shaped crystals which are severely twinned whereas the reaction of DABCO with XeO3 in the presence of HF forms [DABCOH]2[F2(XeO3)2]∙H2O and [DABCOH2][F][H2F3] which were also characterized by low-temperature X-ray crystallography and Raman spectroscopy. A reversible temperature-dependent phase transition occurred for [DABCOH]2[F2(XeO3)2]∙H2O. The structures of 2,2’-bipy∙XeO3 and 1,10-phen∙XeO3 provide the first examples of noble-gas chelates. The structure of hexamine∙XeO3∙H2O provides the first instance in which a noble-gas centre is coordinated by water. These compounds also represent the first examples of sp2- and sp3-hybridized N---Xe(VI) bonds and are rare examples of noble-gas compounds that are air-stable at ambient temperatures.
Adducts between XeO3 and three molar equivalents of the nitrogen bases, pyridine and 4-dimethylaminopyridine (4-DMAP), have been synthesized and characterized. The crystal structures of (C5H5N)3XeO3, {(CH3)2)2NC5H4N}3XeO3∙H2O have been determined by low-temperature single-crystal X-ray diffraction. The reaction of hydrolyzed XeF6 in acetonitrile with pyridine or 4-DMAP afforded [C5H5NH]4[HF2]2[F2(XeO3)2] and [(CH3)2NC5H4NH][HF2]∙XeO3 which were characterized by low-temperature X-ray crystallography and Raman spectroscopy. The structures contain pyridinium cations that are hydrogen bonded to the fluoride coordinated to XeO3 and can be viewed as pyridinium fluoroxenates. The structure of (CH3)2NC5H5N∙XeO3∙H2O contains a water molecule that is hydrogen bonded to two oxygen atoms of two adjacent XeO3 molecules. The pyridine adduct, (C5H5N)3XeO3, was found to be relatively insensitive to shock, whereas the 4-DMAP adduct was extremely shock sensitive.
The number of isolable compounds which contain different noble-gas−element bonds is limited for xenon and even more so for krypton. Examples of Xe−Cl bonds are rare and prior to this work, no definitive evidence for a Xe−Br bonded compound existed. The syntheses, isolation, and characterization of the first compounds to contain Xe−Br bonds ([N(C2H5)4]3[Br3(XeO3)3] and [N(CH3)4]4[Br4(XeO3)4]) and their chlorine analogues are described. The bromo- and chloroxenate salts are stable in the atmosphere at room temperature and were characterized in the solid state by Raman spectroscopy, low-temperature single-crystal X-ray diffraction, and in the gas phase by quantum-chemical calculations. They are the only known examples of cage anions that contain a noble-gas element. The Xe−Br and Xe−Cl bonds are weakly covalent and can be viewed as σ-hole interactions, similar to halogen bonds.
Xenon trioxide reacts with alkali metal fluorides and chlorides to form a variety of room-temperature stable fluoro- and chloroxenate salts. The reaction of XeO3 with various ratios of KF in water afforded three new compounds. The crystal structures of α-K[F(XeO3)2], β-K[F(XeO3)2], α-K[FXeO3], K2[F2(XeO3)] have been determined. The reaction of XeO3 with aqueous CsF resulted in Cs3[F3(XeO3)2]. The XeVI−F bond lengths range from 2.3520(18) to 2.5927(17) Å. No stable product was isolated when [N(CH3)4]F was the fluoride source, but in the presence of HF, crystals of [N(CH3)4]3[HF2]2[H2F3]∙2XeO3 were obtained. The reaction of KCl with XeO3 in equimolar amounts resulted in the formation of K[ClXeO3] whereas the analogous reaction with CsCl yielded Cs3[Cl3(XeO3)4].
Attempts to synthesize Xe–P and Xe–S bonded compounds were unsuccessful and instead resulted in adducts between XeO3 and O-bases such as the phosphine oxide adduct, {(C6H5)3PO}2XeO3 and dimethylsulfoxide (DMSO) adduct {(CH3)2SO}3(XeO3)2. Although DMSO was found to be resistant to oxidation by XeO3, no significant Xe---S bonding interactions were observed. Acetone was found to be highly resistant to oxidation by XeO3 and forms {(CH3)2CO}3XeO3 at low temperatures. The reaction of pyridine-N-oxide yielded large crystals of (C5H5NO)3(XeO3)2 in which the structure contains short chains in contrast with ((CH3)2SO)3(XeO3)2 whose structure consists of discrete dimers. The reaction of XeO3 with the oxidatively resistant main-group oxide anion source, [N(CH3)4][OTeF5] in CH3CN solvent afforded [N(CH3)4][F5TeOXeO3(CH3CN)2].
Xenon trioxide reacts with potassium hydroxide to form the previously known K4[XeO6]∙2XeO3 salt which was characterized by Raman spectroscopy and low-temperature X-ray crystallography. The reaction of MgO with XeO3 yielded single crystals of [Mg(OH2)6]4[XeO6(XeO3)12O2]∙12H2O, which also contains perxenate-XeO3 interactions. Alkali metal carbonates also incorporate XeO3 into their crystal lattices. Raman spectra of M2[CO3(XeO3)n]∙xH2O (M = Na, K, Rb) were recorded and contain intense bands assigned to the XeO3 stretching modes and very weak bands assigned to the [CO3]2− modes. The reaction of dilute aqueous solutions of XeO3 with RbOH and atmospheric CO2 afforded single crystals of Rb2[CO3(XeO3)2]∙2H2O which were characterized by low-temperature X-ray crystallography. Attempts to incorporate XeO3 into other polyatomic anion salts such as KMnO4, NaClO3, and NaNO3 were unsuccessful.
The reaction of IrO2 with XeF6 in aHF provided [Xe2F11][IrF6], whereas the reaction of IrO2 with KrF2 with ClF3 in anhydrous HF solvent provided [ClO2][Ir2F11] and [ClO2][(μ-OIrF4)3]. The structure of [(μ-OIrF4)3]− consists of a six membered Ir3O3 ring with four terminal fluorine atoms on each Ir atom. It was also found that ClF3 forms an adduct with [Xe2F11][HF2] in which the structural parameters of ClF3 are very similar to that of solid ClF3. The [ClO2][Ir2F11] salt provides the first structural information on the [Ir2F11]− anion and the [(μ-OIrF4)3]− anion represents the first isolated iridium oxide fluoride species.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Xenon is a noble-gas element which is located in the far right-hand column of the periodic table and was previously thought to be chemically unreactive and incapable of forming compounds. In 1962, it was shown that xenon reacts with the most reactive compounds, such as elemental fluorine, but the resulting xenon compounds are themselves highly reactive. This Thesis extends the chemistry of some of the most unstable and chemically reactive xenon compounds that are currently known.  One such compound, xenon trioxide, tends to easily detonate unless carefully handled. Methods of stabilizing xenon trioxide were developed and its behaviour with compounds which resulted in formation of new xenon compounds was studied. The molecular structures of these compounds were investigated in the solid with particular emphases on their chemical bonding. Iridium is one of the most chemically resistant metals known. Highly reactive xenon and krypton compounds were used synthesize new iridium compounds.


title: Three-Phase Dual Active Bridge Converter: Design Considerations and Planar Transformer Design

contributor:
Emadi, Ali
Electrical and Computer Engineering

abstract:
This thesis discusses comprehensive design considerations for the three-phase dual-active-bridge (DAB) converter and presents a planar transformer design for the three-phase DAB converter used in smart home applications.
An overview of the planar transformer, including magnetic cores, planar windings as well as its advantages and disadvantages are presented first. The review on analysis of transformer losses, leakage inductance and stray capacitance provides a guideline for transformer design.
The operating principle of three-phase DAB converter is presented and the closed form expression of zero-voltage-switching (ZVS) condition, current stress of switching devices and DC link capacitors are obtained. Analytical results are applied in the parameter design of the DAB converter.
A new design method for the three-phase DAB converter parameter selection is proposed. A new parameter fL is defined to simplify the analysis from three dimensions (n, f, Lk) to two dimensions (n, fL), from which the feasible value of n is determined. Together with the constraint of transformer design, the effective operating area (EOA) of f and Lk is obtained. The main losses that vary with the selectable parameters are studied and the corresponding converter efficiency is presented at different voltage and power levels. The parameters (n, f, Lk) are determined based on the comprehensive parameter design considerations of the three-phase DAB converter.
A planar transformer for the three-phase DAB converter is designed based on the mathematical analysis and finite element analysis (FEA). The parameters that determine core selection are derived for the three-phase DAB converter. The winding design is accomplished using the FEA simulations. The impacts of different winding structures on the AC resistance, leakage inductance and stray capacitance are investigated, and the fully-interleaved design is selected for its low resistance and structural simplicity.
The planar transformer prototype is built and tested in a three-phase DAB converter. The experimental waveforms at different voltage levels and power ratings demonstrate the effectiveness of the converter and transformer. The converter ZVS behavior and efficiency performance are measured, which validate the analysis.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Frequency response of binaural inhibition underlying duration tuned neurons

contributor:
Faure, Paul A.
Psychology

subject:
Duration Tuned Neurons
Binaural
Paired-tone stimulation
frequency response properties
inferior colliculus
big brown bat

abstract: Auditory neurons selectively respond to frequency and amplitude of sound. In the auditory midbrain, duration-tuned neurons (DTNs) are subsets of neurons that selectively respond to the duration of sound. DTNs may help further understand the neural mechanism underlying temporal processing in the central nervous system. Temporal processing has been shown to play important roles in speech, discriminating species-specific signals, and echolocation. The goal of this thesis is to explore the role of DTNs through single-unit electrophysiological recordings in the auditory midbrain of the big brown bat (Eptesicus fuscus). Monotic and dichotic paired-tone stimulation was used to evoke excitatory and inhibitory responses from DTNs. Two stimuli consisted of best duration (BD) excitatory and non-excitatory (NE) tones. In the monotic condition, both tones were presented to the contralateral ear, and when they were close in time, the NE tone always suppressed spikes evoked by the BD tone.  In the dichotic condition, the BD tone was presented to the contralateral ear. The NE tone was presented to the ipsilateral ear and suppressed BD tone evoked spiking in ~50% of cells. Properties of the ipsilaterally-evoked inhibition were investigated by varying the frequency of the NE tone from the best excitatory frequency (BEF), throughout a cell’s excitatory bandwidth (eBW). We measured the inhibitory frequency response area, best inhibitory frequency (BIF), and inhibitory bandwidth (iBW) of each cell. We found inhibition became weaker as the frequency of the NE tone moved further from the middle of the eBW. We found that a DTN’s BEF and BIF closely matched, but the eBW was broader than the iBW and overlapped the iBW measured from the same cell. This suggests temporal selectivity of midbrain DTNs are created by monaural inputs, with binaural inputs playing a lesser role in shaping duration selectivity.

abstract: Thesis

abstract: Master of Science (MSc)


title: SELF-CROSSLINKING P(APM-CO-AA) MICROSTRUCTURED FILMS AND NANOFIBROUS SCAFFOLDS AS BIOMIMETIC SCAFFOLDS

contributor:
Moran-Mirabal, Jose
Stöver, Harald
Chemistry and Chemical Biology

subject: polymer scaffolds

abstract: In nature, cells reside within an extracellular matrix (ECM), consisting of 3-dimensional (3D) networks of collagen and elastin which provide biophysical/chemical signals to direct cellular development and behaviour. Traditional methods of studying cellular behaviour often involve using 2-dimensional in vitro models that are convenient and cost-effective, but may not be representative of 3D in vivo conditions. A synthetic polyampholyte system, poly(N-(3-aminopropyl)methacrylamide hydrochloride-co-acrylic acid) [p(APM-co-AA)], was used here for the first time to construct two types of 3-dimensionally structured cell supports to mimic the ECM: microstructured films and nanofibrous scaffolds. Microstructured films were fabricated using a shape-memory polymer structuring approach and nanofibrous scaffolds were formed using electrospinning. Both films and nanofibers were thermally crosslinked by reaction of initially formed anhydride groups with pendant amines. Film topography was tuned through polymer solution concentration, and the surface chemistry of the crosslinked p(APM-co-AA) scaffolds was tuned by reaction of residual anhydride groups with hydrophilic or hydrophobic amines. The effects of film surface topography and surface chemistry on fibroblast morphologies were explored using fluorescence microscopy. This work presents the fabrication and characterization of tunable, self-crosslinking p(APM-co-AA) scaffolds as promising ECM mimics.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: The extracellular matrix (ECM), present within all biological tissues, consists of 3-dimensional (3D) networks of proteins which provide chemical and physical cues for cells. Abnormalities in the ECM is associated with a variety of disorders, such as coronary heart disease and tumours. Thus, the study of the ECM and how it affects cell behaviour is important both for a better understanding of ECM-related diseases, as well as for creating ECM-mimics for tissue engineering. The goal of this thesis is to explore the fabrication of 3D scaffolds using a synthetic polyampholyte that can be crosslinked under heat and chemically tuned using functionalization. This polyampholyte was electrospun into nanofibers and prepared into microstructured films, which were used to study the effects of surface topography and chemistry on murine fibroblast morphology and attachment. These polyampholyte scaffolds provide a new means to study cell behaviour in environments that mimic certain aspects of the ECM.


title: Self-Adjoint Sensitivities of S-Parameters with Time-Domain TLM Electromagnetic Solvers

contributor:
Nikolova, Natalia
Bakr, Mohamed
Electrical and Computer Engineering

subject: self-adjoint, sensitivities, S-parameters, time-domain, TLM electromagnetic solvers, waveguide, antenna structures

abstract:
 The thesis presents an efficient self-adjoint approach to the S-parameter sensitivity analysis based on full-wave electromagnetic (EM) time-domain simulations with two commonly used numerical techniques: the finite-difference time-domain (FDTD) method and the transmission-line matrix (TLM) method. Without any additional simulations, we extract the response gradient with respect to all the design variables making use of the full-wave solution already generated by the system analysis. It allows the computation of the S-parameter derivatives as an independent post-process with negligible overhead. The sole requirement is the ability of the solver to export the field solution at user-defined points. Most in-house and commercial solvers have this ability, which makes our approach readily applicable to practical design problems.

 In the TLM-based self-adjoint techniques, we propose an algorithm to convert the electrical and magnetic field solutions into TLM voltages. The TLM-based discrete adjoint variable method (AVM) is originally developed to use incident and reflected voltages as the state variables. Our conversion algorithm makes the TLM-AVM method applicable to all time-domain commercial solvers, FDTD simulators included, with
comparable accuracy and less memory overhead. Our approach is illustrated through waveguide examples using a TLM-based commercial simulator.

 Currently, our TLM-based self-adjoint approach is limited to loss-free homogeneous problems. However, our FDTD-based self-adjoint approach is valid for lossy inhomogeneous cases as well. The FDTD-based self-adjoint technique needs only the E-field values as the state variables. In order to make it also applicable to a TLM-based solver, whose mesh grid is displaced from the FDTD grid, we interpolate the E-field solution from the TLM mesh to that on the FDTD mesh. Our FDTD-based approach is validated through the response derivatives computation with respect to both shape and constitutive parameters in waveguide and antenna structures. The response derivatives can be used not only to guide a gradient-based optimizer, but also to provide a sufficient good initial guess for the solution of nonlinear inverse problems.

 Suggestions for further research are provided.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Rare Earth and Group 4 Transition Metal Complexes of Rigid Dianionic Pincer Ligands

title: Early Metal Complexes of Rigid Dianionic Ligands

contributor:
Emslie, David
Chemistry

subject: organometallic, rigid ligands, rare earth, group 4 transition metal, hydroamination, ethylene polymerization

abstract:
The synthesis and electropositive metal (Y, Lu, La, Zr, Hf) chemistry of
two rigid dianionic xanthene-based ligands, 4,5-bis(2,4,6-triisopropylanilido)-
-2,7-di-tert-butyl-9,9-dimethylxanthene (XN2) and 4,5-bis(2,4,6-triisopropylphenylphosphido)-
2,7-di-tert-butyl-9,9-dimethylxanthene (XP2) have been explored. The reaction of the pro-ligand H2XN2 with [Y(CH2SiMe2R)3(THF)2] (R =
Me or Ph) produced the monoalkyl yttrium complexes [(XN2)Y(CH2SiMe3)-
(THF)].(O(SiMe3)2)x (3, x = 1-1.5) and [(XN2)Y(CH2SiMe2Ph)(THF)].(O-
(SiMe3)2) (4). Neutral 3 reacted with excess AlMe3 to yield [(XN2)Y{(m-
Me)2AlMe2}(THF)].O(SiMe3)2 (5.O(SiMe3)2), which is thermally robust, and
transfer of the XN2 ligand to aluminum was not observed. However, [(XN2)-
AlMe].(O(SiMe3)2)0.5 (6.(O(SiMe3)2)0.5) was synthesized via the reaction of
H2XN2 with AlMe3. Compounds 3, 5 and 6 were characterized by X-ray crystallography,
and neutral 3, while being poorly active for ethylene polymerization,
was highly active for both intra- and inter-molecular hydroamination
with a variety of substrates. The synthesis of the pro-ligand H2XP2 was achieved via reduction of 4,5-bis(2,4,6-triisopropylphenylchlorophosphino)-2,7-di-tert-butyl-9,9-dimethylxanthene
(XP2Cl2; 7). Double deprotonation of H2XP2 (8) with excess KH
yielded the potassium salt, [K2XP2(DME)2.5] (9), which when stirred in THF
followed by recrystallization from hexanes, produced the tetrametallic complex,
[K4(XP2)2(THF)4] (10) featuring a central K4P4 cage. The reaction
of [K2XP2(DME)2.5] (9) with [YI3(THF)3.5] yielded a mixture of products including [(XP2)YI(THF)2] (11) and tris(2,4,6-triisopropylphenylphosphinidene)
(P3Tripp3); pure 11 could be isolated in low yield by extraction with
a minimum volume of hexanes or O(SiMe3)2. In the solid state, complex
11 reveals a face-capped trigonal bipyramidal geometry at yttrium, in which
the xanthene backbone is planar and adopts a large angle (85 degrees) between the
P(1)/C(4)/C(5)/P(2) and P(1)/Y/P(2) planes. Due to the successful synthesis and hydroamination catalysis achieved with
the XN2 ligand in combination with yttrium, the chemistry of XN2 was further
explored using both smaller (Lu) and larger (La) rare earth elements. The
alkane elimination reaction of H2XN2 with [Lu(CH2SiMe3)3(THF)2], followed
by crystallization from O(SiMe3)2, yielded [(XN2)Lu(CH2SiMe3)(THF)].(O-
(SiMe3)2)1.5 (12.(O(SiMe3)2)1.5). By contrast, lanthanum complexes of the
XN2 dianion were prepared by salt metathesis; treatment of H2XN2 with excess
KH in DME produced the dipotassium salt, [K2(XN2)(DME)x] (2; x =
2-2.5), and subsequent reaction with [LaCl3(THF)3] afforded [{(XN2)LaCl-
(THF)}x].(O(SiMe3)2)0.25x (13.(O(SiMe3)2)0.25x; x = 1 or 2) after crystallization
from O(SiMe3)2. Compound 13.(O(SiMe3)2)0.25x reacted with two equivalents
of LiCH2SiMe3, to form the dialkyl-`ate' complex, [Li(THF)x][(XN2)-
La(CH2SiMe3)2].Toluene.LiCl (14.Toluene.LiCl; x = 3). Both 12 and 14 (x
= 4) were structurally characterized by X-ray crystallography, and were evaluated
as catalysts for intramolecular hydroamination. While compound 14
showed poor activity, the neutral lutetium alkyl complex, 12, is highly active
for both intramolecular hydroamination and more challenging intermolecular
hydroamination. Like the yttrium analogue, 3, reactions with unsymmetrical
alkenes yielded Markovnikov products. Additionally, it is noteworthy that the activity of 12 surpassed that of 3 in the reaction of diphenylacetylene with
4-tert-butylbenzylamine. The reaction of H2XN2 with [Zr(NMe2)4], followed by crystallization from
O(SiMe3)2, yielded [(XN2)Zr(NMe2)2].(O(SiMe3)2)0.5 (15.(O(SiMe3)2)0.5). The
zirconium dimethyl complex [(XN2)ZrMe2] (16) was accessed via two routes;
either by treatment of 15.(O(SiMe3)2)0.5 with excess AlMe3, or by reaction of
15.(O(SiMe3)2)0.5 with excess Me3SiCl, affording [(XN2)ZrCl2] (17), followed
by the subsequent reaction of 17 with 2 equivalents of MeLi. The reaction of 16
with one equivalent of B(C6F5)3 or [CPh3][B(C6F5)4] yielded cationic [(XN2)-
ZrMe][MeB(C6F5)3] (18) and [(XN2)ZrMe(arene)][B(C6F5)4] (19; arene =
n6-benzene, n6-toluene or bromobenzene), respectively. Both 18 and 19 are active
for ethylene polymerization under 1 atm of ethylene at 24 and 80 degree Celcius in
toluene, with activities ranging from 23.5{883 kg/(mol.atm.h), yielding polymers
with weight average molecular weights (Mw) of 71{88 kg/mol and polydispersities
(Mw/Mn) of 3.94-4.67.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract:
Pincer ligands are defined as meridionally-coordinating tridentate ligands,
and are typically mono-, di- or tri-anionic. This thesis is focused on the synthesis
and reactivity of rigid dianionic pincer ligands with an NON- or POP-donor
array, with particular emphasis on rare earth and group 4 transition
metal complexes. This work explores the effect that these rigid ligands have
on the reactivity of the resulting metal complexes and the thermal stability
of the solid state structures. Both neutral and cationic mono alkyl complexes
have been isolated, and several are highly active catalysts for intra- and intermolecular
hydroamination or ethylene polymerization.


title: High-Power Diode Laser Surface Hardening Within a Machining Center

contributor:
Koshy, Philip
Elbestawi, Mohamed A.
Mechanical Engineering

subject: high-power, diode laser, surface hardening, machining center, heat transfer, temperature

abstract:
 Flexible manufacturing systems and lean production philosophies are in increasing industrial demand. Multiple manufacturing processes integrated into stand alone automated equipment can be utilized to greatly reduce operation costs. New technologies are continually being developed that can be easily combined with related manufacturing processes. Flexible machining and surface hardening operations can be realized in a single set-up by integrating a high-power diode laser (HPDL) within a machine tool structure.

 The following research presents the concept of integrated laser surface hardening within a machine tool environment. Experimental work was performed using a HPDL for transformation hardening of AISI 4140 steel.

 Both quasi-steady analytical and transient finite element heat transfer models have been developed. Solutions of the models are compared, which show that the more sophisticated finite element modeling is necessary only if accuracy of peak surface
temperature is important. Otherwise, the simpler but faster analytical model can be used to describe the temperature profiles during laser heating.

 A novel approach using temperature indicating lacquers was shown to be a simple and reliable tool for temperature measurement. The analytical model was further used to find a best fit with the experimental measurements to estimate the fraction of laser power absorbed by the workpiece surface. With the aid of the model, it was shown that the austenite transformation temperature is highly dependent on the scanning speed. For slower speeds, the transform temperature was closer to the A3 temperature given by the iron-iron carbide phase diagram. Tests performed at faster scanning speeds indicated transformation temperatures as high as 1230 °C.

 Experiments were divided into three series. The first series was performed at slow scanning speeds (200-1000 mm/min) and low laser powers (200-500 W). Hardening was executed on flat workpieces with the laser scanning along a linear path. The second and third test series were performed at fast scanning speeds (2000-8000 mm/min) and higher laser powers (1000-2000 W) with hardening done on rotating cylindrical workpieces. The third tests series consisted of two laser passes in an attempt to increase the penetration depth of the hardened layer. These tests resulted in severe distortion due to melting that would require nearly the entire hardened layer to be machined away post heat treatment. However, if the melting temperature is not significantly exceeded multiple laser passes could be used to increase the thickness of the hardened layer.

 Higher case depths were realized for the slow tests since these tests have a greater laser-work interaction time. During laser treatment, the uncoated workpieces were left exposed to allow for oxidation and melting in order to increase the fraction of absorbed laser power. The absorptivity is shown to be as high as 85% for these tests.

 Results are presented in a form useful in selection of laser power and scanning speed to obtain the desired level of hardening, without having to resort to complex analytical or numerical models. Investigations into in-process monitoring show that measurement of surface temperature using an infrared thermometer could be used to
control the generated hardened layer reducing process scrap.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Carbon Injection Into Electric Arc Furnace Slags

contributor:
Coley, Kenneth S.
Irons, Gordon A.
Materials Science and Engineering

subject: carbon, injection, electric arc, furnace, slags, gasification

abstract: The reaction between carbon and iron oxide-containing slag is crucial to efficient electric arc furnace steelmaking. The reaction occurs via gaseous intermediates, and the rate of gas generation by carbon gasification is limited by the chemical reactions at the slag-gas and carbon-gas interfaces. The aim of the present study was to obtain an understanding of the gasification rate limiting factors and slag foaming behaviour that could be readily applied to industrial electric arc furnace situations. The rate of carbon gasification was measured in experimental simulations of an electric arc furnace heat with slags containing between 21.6 and 48.2 wt% 'FeO'. It was found that rate control was dominated by the carbon-gas chemical reaction. A model was developed which describes the carbon gasification rate, amount of residual carbon in the slag, gas composition, slag-gas interfacial area and bubble diameter during carbon injection into slag. The model predicts rate control by the carbon-gas chemical reaction, in agreement with experimental observations. The slag foaming behaviour was investigated, and it was found that the foaming index is a useful parameter in quantifying foam height only if void fraction is constant with respect to gas flow rate. The average bubble size was observed to be an important factor in determining foam stability, with smaller bubble size resulting in greater foam height.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Peripheral artery endothelial function responses to altered blood flow in humans

contributor:
MacDonald, Maureen
Kinesiology

subject:
endothelial function
blood flow
flow-mediated dilation
shear stress
flow pattern
arterial function

abstract:
Endothelial function is influenced by a variety of factors, including shear stress direction and magnitude. Whereas improvements in endothelial function have mostly been attributed to increased anterograde flow, the results of many interventional models in humans suggest that enhancing blood flow in both anterograde and retrograde directions to create a high shear stress oscillatory stimulus may be optimal for improving endothelial function.  Well-controlled studies are necessary to further this theory. The purposes of this study were to determine the brachial artery acute shear stress and endothelial function responses to (1) passive heat stress (HEAT), (2) ECG-gated cuff compressions (CUFF), and (3) ECG-gated rhythmic handgrip exercise (HGEX); and (4) to determine if there is a relationship between the degree of shear stress oscillation and endothelial function, regardless of the stimulus applied. We hypothesized that (1) HEAT would increase anterograde shear stress and decrease retrograde shear stress, leading to an unpredictable change in endothelial function; (2) CUFF would increase both anterograde and retrograde shear stress, leading to an increase in endothelial function; (3) HGEX would increase anterograde and retrograde shear stress and exercise metabolites, leading to an increase in endothelial function; and (4) the change in oscillatory shear index would be positively associated with the change in flow-mediated dilation, such that an increment increase in the degree of shear stress oscillation would be accompanied by a proportional improvement in endothelial function.
In separate visits, 10 young healthy males (22±3 years) underwent 10 minutes of unilateral HEAT, CUFF, or HGEX on the left arm (EXP), while the right arm served as a within-subject time control (CON). Non-invasive finger plethysmography was used to measure heart rate (HR) and blood pressure (BP) throughout the testing sessions. Ultrasonography was used to obtain measures of blood velocity and arterial diameter from the brachial artery of both limbs throughout the interventions. Anterograde and retrograde shear stress (SS) and oscillatory shear index (OSI) were calculated at baseline and during each intervention to assess the blood flow pattern changes. Endothelial function was assessed before and after each intervention, in both limbs simultaneously using a flow-mediated dilation (FMD) test. HEAT increased HR during the intervention (P < 0.05), mean BP and diastolic BP after the intervention (P < 0.05), anterograde SS in EXP (rest: 15.2 ± 2.9 vs. HEAT: 29.8 ± 8.5 dynes/cm2, P < 0.05), and FMD% in both limbs (P = 0.000). CUFF did not change HR or BP, increased anterograde (rest: 17.9 ± 4.1 vs. CUFF: 43.0 ± 12.4 dynes/cm2, P < 0.05) and retrograde (rest: -3.1 ± 2.5 vs. CUFF: -22.7 ± 6.0 dynes/cm2, P < 0.05) SS in EXP, but did not change FMD% in either limb (P = 0.248). HGEX increased HR during the intervention (P < 0.05), mean BP during and after the intervention (P < 0.05), anterograde SS in EXP (rest: 18.7 ± 5.9 vs. HGEX: 56.4 ± 11.5 dynes/cm2, P < 0.05), and FMD% in both limbs (P = 0.001). These findings suggest that an anterograde-dominant shear stress stimulus may be effective at improving endothelial function, but the confounding effect of sympathetic nervous system activation may play a more dominant role in the acute control response for shorter duration interventions such as the ones explored in this study.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: It has been well established that the pattern of blood flow can impact arterial function, but the nuances of this relationship remain unclear. Through the use of heating, cuff compression, and exercise, this study sought to determine the optimal shear stress pattern to see beneficial changes in arterial function in the arm of young healthy males. Our results show many real life interventions alter not only the shear stress pattern in the artery, but also involve other systems like the brain and muscle that are crucial to maintaining the body’s physiological balance. It is clear that arterial function is regulated through a variety of different mechanisms, and that the changes we observe will depend on the parameters (e.g. duration, intensity, timing of assessment) of the applied stimulus. More specifically, isolating study designs should be constructed to determine the individual contributions of different human body systems to the arterial regulatory response.


title: Rolling in the (Waters of the) Deep: Purification and Water Imagery in Early Jewish Literature

contributor:
Machiela, Daniel
Religious Studies

subject:
Purity
Ancient Judaism
Water
Priestly author
Ritual washing
Liminality
Sanctification
Creation/Flood
Eschatology

abstract:
Scholars such as Jonathan Klawans have distinguished between two types of impurity described in priestly texts: ritual and moral.  The former, which denotes bodily pollution, occurs as a result of natural human processes (i.e., birth, death, genital discharge) and can render one temporarily unfit for temple worship, though it bears no clear ethical implications. Conversely, moral impurity refers to the more permanent defilement brought about by ethical transgressions (i.e., murder, apostasy, adultery), and has the capacity to stain the land of Israel itself, in addition to threatening the sanctity of the temple. However, this separation between ritual and moral dimensions of pollution are not absolute, as even Klawans allows that these categories are rather “pliable” (and to a certain extent, intertwined.)
This thesis explores the concept of purity (both ritual and moral) in early Jewish literature, through a detailed analysis of water and cleansing language. In particular, I emphasise conceptual links between water for a) ritual washing and b) moral cleansing or sanctification. In this way, I highlight the flexibility of scholarly purity categories, demonstrating how purification can often be understood “holistically,” as encompassing both ritual and moral dimensions. I also illustrate how water seems to embody liminal tensions, oscillating between thresholds of purity and pollution, as well as primordial chaos and cosmic order. The thesis is divided into two major sections: Part One focuses on representations of water in the Hebrew Bible, whereas Part Two examines non-canonical texts from the Second Temple period.

abstract: Thesis

abstract: Master of Arts (MA)


title: The Lived Experiences of Women in Christian Ministry in Canada

contributor:
Pawluch, Dorothy
Sociology

subject: Identity, Narrative Work, Turning Points, Christian Ministry, Gender, Clothing, Liminal, Carnal, Spiritual, Feminization, Christian Pastors, Religion, Performance of Self, Symbolic Interactionism, Grounded Theory, Qualitative Research

abstract: The entrance of women into ordained ministry positions is a relatively new phenomenon in the North American Christian church, and has yet to be given adequate scholarly attention. This thesis probes the experiences of several pioneering women, presenting both the substantial and theoretical contributions emerging from a qualitative study of female pastors ministering in Protestant congregations across Canada. Data collection and analysis were approached through the lens of symbolic interactionism and grounded theory. The main findings emerging from 44 qualitative, in-depth interviews have been organized into three distinct papers to constitute a sandwich dissertation. The first paper outlines how some women experience a “call” to ministry and how this change in trajectory impacts their identity and constructions of the past, while the second two papers address different facets of performing the pastoral role once within it. Paper 2 explores the dilemmas women encounter in the area of clothing and appearances, a concern many of the women identified as influencing their performance of the pastoral role. Paper 3 explores in greater depth the ways women feel they perform the pastoral role differently than their male counterparts, and raises questions about the impact this may have on changing the role in the future. Taken together, the three papers contribute to a broad range of debates in the theoretical literature about key facets of the human experience, including: changing career trajectories, role making and performance of self, and microlevel influences on institutional change. The dissertation also encourages a new direction for sociological research – human interactions with the divine.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: This thesis investigates what it is like to be a female pastor in the Christian church in Canada, as women have only recently been able to be fully ordained in most Protestant denominations. Three themes are explored: (1) how women decide to enter into Christian ministry, (2) how they navigate dilemmas around clothing in the pastoral role, and (3) how they feel they do pastoral ministry differently than their male counterparts. On a more theoretical level, this thesis also helps us understand the experiences of women entering traditionally male occupations, illuminating how they – and perhaps anyone who undergoes a career transition – navigate changes in work roles and identities, how clothing can help them achieve legitimacy in a role, and how women may be changing the professions they enter into in large numbers by doing their work differently.


title: The Effects of Radiative Feedback on Star Cluster Formation and the Galactic Interstellar Medium

contributor:
Pudritz, Ralph
Harris, William
Physics and Astronomy

subject:
Astrophysics
Star Clusters
Simulations
Radiative Transfer
HII Regions
Feedback

abstract:
The majority of stars form in clusters which are themselves birthed in Giant Molecular Clouds (GMCs). The radiation produced by clusters during their formative phase heats and ionizes the surrounding gas and drives outflows via radiation pressure. The combination of these processes, referred to as radiative feedback, is a proposed mechanism for limiting the star formation efficiency (SFE) in molecular clouds. In this thesis, we use 3D numerical simulations of turbulent GMCs, completed using the code FLASH and a sophisticated radiative transfer scheme, to explore the effects of radiative feedback on cluster formation and the larger scale interstellar medium (ISM). We present suites of simulations that vary the initial GMC mass from 10^4 to 10^6 M$_{\odot}$ and consider both gravitationally bound and unbound clouds. We find that clusters form within the highly filamentary clouds where they can undergo subsequent merging. Radiative feedback only plays a minor role in lowering the SFE of 10^6 M$_{\odot}$ GMCs. However, it completely disrupts intermediate mass clouds (~10^5 M$_{\odot}$), reducing the SFE by a factor of two. We then examine the escape fraction of UV photons from GMCs --- a quantity relevant to the structure of the ISM and cosmic reionization. We show that the escape fraction is dynamic
and can vary by factors of two over short timescales because of the rapid growth and collapse of HII regions. The escape fractions from massive GMCs are typically low (~5%) while intermediate mass models are characterized by escape fractions nearing 100%. We combine our GMC models to represent the escape fraction from a population of clouds in dwarf starburst and spiral-type galaxies. We successfully reproduce the star formation rates in these galaxies and find typical escape fractions of 8% in all cases. These results place important constraints on galactic-scale models studying the ISM and cosmic reionization.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Investigating implications and mechanisms of diet induced obesity for multi organ function in a murine model of early sepsis

contributor:
Fox-Robichaud, Alison
Medical Sciences

subject: obesity, early sepsis, inflammation

abstract:
Given the current obesity epidemic, the prevalence of overweight and obese patients with critical illness is increasing rapidly, however how obesity shapes critical illness and immune response to infection is not entirely understood. We developed a clinically relevant murine model of obesity in the context of sepsis, and examined organ specific inflammatory responses. Male C57BL/6 mice were fed either a high fat Western Diet (WD) (Modified Breslow, 21% Butterfat and 0.15% cholesterol) or normal chow diet (NCD) for 6, 15 or 27 weeks. Sepsis was induced by cecal ligation and perforation (CLP), and six hours post-surgery, plasma and tissue samples were harvested and flash frozen in liquid nitrogen. Septic obese mice at 15 and 27 weeks had significantly (p<0.0001) lower levels of lung myeloperoxidase (26.3±3.8 U/mg tissue) compared to age matched ad libitum (44.1±2.8 U/mg tissue) and diet restricted (63.2±5.60 U/mg tissue) controls, indicative of less lung inflammation. Obese mice (4.23±0.10g) had significantly enlarged livers compared to controls (1.55±0.80g and 1.22±0.031g), with pronounced steatosis, and hepatocyte ballooning, independent of sepsis. These findings are in congruence with clinical observations that obese individuals are protected from sepsis-induced lung injury, however the mechanisms involved are not entirely clear.
We also examined effects of housing conditions on susceptibility to developing metabolic syndrome, and inflammatory response in our obesity and sepsis model. For this study, animals were fed either WD or NCD for 15 weeks and were housed in static or ventilated cages. Unlike static cages, ventilated cages have HEPA filtered air supply system and exhaust air ventilation, protecting the animals from air borne particles and preserving the microbiological barrier. Therefore, ventilated cages provide a more sterile environment compared to static cages. After 15 weeks, fecal matter was collected from the cages and mice were subjected to sepsis using the CLP technique. Six hours post surgery, animals were sacrificed and tissues were harvested, snap frozen and stored at   -80°C. The animals from the more sterile environment (ventilated cages) had significantly (p<0.0001) less weight gain and did not show signs of overt hyperglycemia, compared to mice housed in a less sterile environment (static cages). In addition, obese mice housed in static cages had less lung injury compared to controls during early sepsis, however this difference was not evident in mice from ventilated cages. There were also significant differences in the fecal microbe composition, where ventilated groups had greater Firmicutes (69% ± 0.06% for WD and 76% ± 0.03%) and less Bacteroidetes population (15% ± 0.04% for WD and 12% ± 0.02% for NCD) compared to static groups (Firmicutes: 42% ± 0.08% for WD and 24% ± 0.02% for NCD, Bacteroidetes: 37% ± 12% for WD and 53% ± 29% for NCD). This study highlighted the impact of environment on the susceptibility to developing metabolic syndrome, and the potential impact on the associated immune responses, in our mouse models of obesity and sepsis.
Leptin is an important mediator of immune responses to infection, and the levels are elevated during diet induced obesity in both mice and humans. We found that mice treated with leptin one hour prior to surgery, had significantly less injury (32.62±1.6 U/mg tissue) compared to saline treated animals (46.58±3.48 U/mg tissue), as evident from lung myeloperoxidase levels and histopathology scores. In addition, proprotein convertase subtilisin/kexin type 9 (PCSK9) over expressing mice on a normal diet, had significantly greater lung injury (46.51±4.51 U/mg tissue myeloperoxidase levels) compared to knockouts (31.14±1.75 U/mg tissue), this difference was not observed in WD fed mice with differential PCKS9 expression. In conclusion, WD fed mice had significantly less lung inflammation but greater hepatic injury. Furthermore, both leptin and PCSK9 are important mediators of lung inflammation in early sepsis.

abstract: Thesis

abstract: Doctor of Science  (PhD)


title: The Constitution of Theseus: The Metaphysics of Constitutional Precommitment

contributor:
Waluchow, Wilfrid J.
Philosophy

subject:
commitment
constitutions
essential features
precommitment

abstract: Constitutions and bills of rights have previously been argued to be non-democratic. To justify the entrenched nature of constitutions, some theorists have argued that constitutions represent a type of rational precommitment. However, this precommitment understanding of constitutions is not without its own problems. In this work, I will argue the prominent understanding of constitutional precommitment used by its proponents seems to rely upon a definition of commitment to which their arguments do not stay true. However, when I try to amend their arguments and apply a proper example of commitment, it leads to some problems with other tenets of the constitutional debate, especially the fact of constitutional entrenchment. In an attempt to determine just what it would take to save the rational precommitment understanding of constitutions, while maintaining a proper definition of commitment, I turn to metaphysical puzzles about change, persistence, and the possibility of a mereological understanding of our constitution. I conclude that 1) current debates do not have a proper conception of commitment and are thus failing to accomplish their ends, and 2) if proponents of the rational precommitment view do not buy into my analysis, then it is going to prove quite difficult to keep their account afloat once we properly define commitment.

abstract: Thesis

abstract: Master of Arts (MA)


title: THE IMPACT OF BISPHENOL A IN COMBINATION WITH STRESS AND DIETHYLHEXYL PHTHALATE ON IMPLANTATION, UTERINE MORPHOLOGY, AND ADHESION PROTEIN EXPRESSION IN INSEMINATED FEMALE MICE

title: ENVIRONMENTAL CHEMICALS AND STRESS DISRUPT IMPLANTATION

contributor:
deCatanzaro, Denys
Psychology

subject:
Toxicology
BPA
Endocrine Disrupting Chemicals
DEHP
Reproduction
Implantation

abstract: Bisphenol A (BPA), the monomer of polycarbonate plastics and epoxy resins, can disrupt intrauterine implantation of fertilized ova in mice. This effect is also induced by exposure to chronic stress or high doses of diethylhexyl phthalate (DEHP), a plasticizer found in polyvinyl chloride products. I assessed the potential combinatory effects of BPA and stress on blastocyst implantation, uterine morphology, adhesion protein expression, and urinary hormone levels. Subcutaneous injections of BPA administered from gestation days (GDs) 1–4 paired with a stressor (rat exposure across a grid) reduced the number of implantation sites on GD 6 at a dose where neither BPA nor stress had this effect on their own. Uterine luminal area was increased by BPA when paired with stress. BPA reduced epithelial cadherin (e-cadherin), a uterine adhesion protein, independently from the stressor. Urinary estradiol was significantly increased by BPA relative to controls, regardless of stress. In other experiments, effects of concurrent BPA and DEHP administered were assessed. Inseminated female mice were injected with BPA, DEHP, or BPA + DEHP from GDs 1–4. Implantation measured in uteri on GD 6 was disrupted by a combined dose but not by the individual doses. This dose also decreased the amount of e-cadherin and cadherin-11, another adhesion protein expressed by cells, while cadherin-11 was also affected by BPA alone. In further experiments designed to elucidate the interaction of BPA and DEHP, mice were fed 14C-BPA and injected with varied doses of DEHP, then tissues were excised and measured for radioactivity. When given DEHP, males and cycling and peri implantation females showed increased BPA deposition in reproductive tissues and serum. As people are commonly exposed to both DEHP and BPA through consumer products, it is important to determine their interactions and also to understand how dose-response is affected by other factors such as stress.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Concentrations of bisphenol A and estradiol are elevated by exposure to endocrine-disrupting chemicals

abstract: Endocrine-disrupting chemicals (EDCs) are synthetic substances that perturb estrogen, androgen, and thyroid systems, thereby impacting development, reproduction, behaviour, and general health. People are concurrently exposed to numerous EDCs from diverse sources, including consumer products, personal care products, medical devices, and environmental media. I explored impacts of [1] triclosan (a synthetic biocide), [2] butyl paraben and [3] propyl paraben (antimicrobial preservatives), and [4] tetrabromobisphenol A (a flame retardant) on bisphenol A (BPA) and 17β-estradiol (E2) concentrations in vivo. I developed a novel protocol that measured acute effects of these four EDCs upon radiolabeled 14C-BPA or 3H-E2 in blood serum and tissues, and natural E2 in urine. First I showed that BPA, the monomer of polycarbonate plastics, localizes to the reproductive organs of female mice following low-dose dietary exposure. Subsequently, I demonstrated that exposure to any one of the four EDCs elevated 14C-BPA concentrations in blood serum, reproductive organs, and other peripheral tissues of female and male mice. Such exposure also elevated concentrations of natural E2 in urine. Finally, I showed that concurrent exposure to all four EDCs, in addition to diethylhexyl phthalate (a plasticizer), can elevate concentrations of 14C-BPA and E2 at much lower doses than required when given alone. These data show that endocrine-disrupting chemicals interact in vivo, and that they can modulate the toxicokinetics of BPA and disrupt natural estrogen homeostasis. This is consistent with evidence that EDCs compete for access to enzymes that are critical for their metabolism and estrogen regulation, such as cytochrome p450, sulfotransferase, UDP-glucuronosyltransferase, and hydroxysteroid dehydrogenase. Given the detrimental reproductive and carcinogenic effects of persistently elevated estrogen activity, the findings of these studies emphasize the importance of further investigating adverse health outcomes of chemical mixtures. Furthermore, studies of multiple chemicals should be considered when assessing risk and determining regulatory exposure limits.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: HUMAN MOTOR CORTEX ORGANIZATION: HOMUNCULAR PLASTICITY AND ITS MECHANISM

contributor:
Nelson, Aimee
Kinesiology

subject: Motor Cortex, Spinal cord injury, Homunculus, Neuroplasticity, Interhemispheric inhibition

abstract: The primary motor cortex (M1) contains a somatotopic progression with highly overlapping areas outputting to muscles of the upper limb. This organization is modified by muscle activity and neurological injury such as spinal cord injury (SCI). To date, bilateral M1 organization in controls and SCI has been minimally explored, and no study has examined the cortical territory that directs output to multiple muscles thought to be involved in movement synergies. An initial study was conducted to characterize the bilateral organization and representational overlap for muscles of the upper limb in incomplete spinal cord injury relative to uninjured individuals. Differences in symmetry and amount of overlapping territory were observed between groups, possibly reflecting differences in synergistic muscle use. The second study examined transcallosal communication between the two motor cortices and its role in dynamically modulating motor representations during unilateral contraction. The depth of interhemispheric inhibition (IHI) was examined in a muscle of the right hand by delivering a conditioning stimulus to ipsilateral M1 followed by a test stimulus to contralateral M1. Reduced IHI corresponded to larger cortical territory, a relationship that existed for both contralateral and ipsilateral contraction.  These data demonstrate that the magnitude of IHI in a hand muscle predicts the size of the cortical territory occupied by that muscle. We present a mechanistic model to explain these findings that further elucidate the role of interhemispheric communication in shaping motor output. This interaction between transcallosal inhibition and motor output may act as a component to experience-dependent plasticity within M1. By targeting this interaction, it may be possible to facilitate motor learning and performance or promote recovery of function following neurological injury. Further study examining the role of various intracortical circuits on representational plasticity and modulation of these interactions may yield advances in both basic and clinical neuroscience.

abstract: Thesis

abstract: Master of Science (MSc)


title: High Field NMR Investigation of Yb2Pt2O7

contributor:
Imai, Takashi
Physics

abstract: The rare-earth pyrochlore oxides are the prime example of three-dimensional frustrated magnetism. Pyrochlores are of the chemical form A2B2O7 where the A site is a rare-earth metal and B is a non-magnetic ion. The A and B sites separately form a network of corner-sharing tetrahedra which are interwoven with each other. The geometric frustration of the pyrochlores make them extremely interesting as it introduces new and complicated behaviour that has not been studied before. It is typically difficult to conduct NMR experiments on such materials as many of the more well studied pyrochlore materials do not have appropriate nuclei for NMR. Yb2Pt2O7 is an exception as platinum is an excellent atom for NMR experiments. Yb2Pt2O7 is an effective S=1/2 XY pyrochlore, meaning that the magnetic moment on the Yb ion is anisotropic.  195Pt high field NMR measurements were performed on a powder sample of the pyrochlore Yb2Pt2O7 in fields from 1T to 8T. The NMR frequency shift increased rapidly at low temperature until it was saturated due to the magnetic field strength.  The spin-lattice relaxation rate, 1/T1, showed exponential behaviour from ~20K down to 1.8K for the higher fields of 2T, 4T and 8T. The rapid decrease in 1/T1 indicates that the spin fluctuations freeze out at temperatures well before the known zero-field transition to a ferromagnetic state at ~0.3mK. The 1/T1 data was fit to an exponential e^(-∆/T) to extract an energy scale ∆.  Finding the peak of the 1/T1T as a function of temperature and scaling analysis were also used to determine an energy scale. All three methods showed the same behaviour with magnetic field strength, where ∆ decreases linearly as the field strength is lowered.  Low field NMR experiments are being planned to determine if this behaviour continues below 1T.

abstract: Thesis

abstract: Master of Science (MSc)


title: Enhancing the Capability of White Light Interferometry on Complex Surfaces

contributor:
Veldhuis, S. C.
Mechanical Engineering

subject: white light, interferometry, complex surfaces, ZYGO NewView 5000

abstract:
 The Zygo NewView 5000 is a new piece of equipment for McMaster University - it has recently been bought, and it is the first white light interferometer at McMaster. This thesis begins by developing the capabilities of this equipment. A significant limitation found is that the sample being measured must be near perpendicular to the optical axis. The optical axis is the centre of the light beam path for the light that the white light interferometer uses to make measurements. A significant enough angle away from perpendicularity will cause "dropout," where no data is returned for that pixel. Through experimenting with taking flat measurements (where the test part is perfectly perpendicular) and attempting to combine them with tilted measurements, a certain amount of distortion was found between the two. In order to properly fill in data, this problem needs to be addressed; correspondingly the focus of the thesis was altered to account for the distortion. Further experiments were performed
comparing measurement profile results to those obtained using a Mitutoyo Formtracer, a stylus profilometer. It was determined that measurement distortion on the Zygo NewView only occurred when the samples were tilted; tilted measurements from the Zygo NewView were therefore altered with a distortion correction function to compensate for the error. There was a much better match of the tilted Zygo data to the Mitutoyo Formtracer results when the distortion correction was applied to the data, particularly in the areas where the tilt improves the data quality.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: A self-heuristic biases perception and representation of novel people and objects

contributor:
Shedden, Judith M.
Psychology

subject:
self
social cognition
heuristic
ownership
Implicit Association Test
implicit
memory
association

abstract:
A robust associative self network automatically biases attention, memory, and impression formation in a heuristic-like way. This thesis examines whether this self-heuristic underlies association formation of novel person and object representations to the self network and how this structure influences perceptions.
	This was tested across three experiments. The first employed an implicit task to assess whether self-similar individuals were represented with greater association strength to self-concept than self-dissimilar individuals. The second used an implicit task to measure whether newly-owned, previously-owned, and unowned objects exhibited different association strength with self-concept. The third determined the impact of minimal self-similarity to another individual, presented either before or after encoding, on memory for encoded information about them.
	Results of these experiments support three conclusions summarizing how a self-heuristic affects perceptions of novel stimuli. First, self-relevance automatically biases cognitive representation of novel self-similar (versus self-dissimilar) people and owned (versus unowned) objects, evidenced by stronger implicit association strength between these stimuli and self-concept. Next, this representation biases memory accuracy and errors in favour of heuristic-consistent information, even in contexts of minimal self-similarity. Finally, representation of self-similar people and owned objects relative to the self network biases perception through first-order effects, whereby unrelated concepts sharing an association to the self-network can influence one-another. Owned objects were automatically more favourably evaluated due to a first-order association with self-positivity. Perception of well-established self-knowledge was malleable based on response pairing with first-order associated self-similar or self-dissimilar individuals. Finally, when memory retrieval for self-similar and self-dissimilar individuals failed, responses were predicted based on first-order associated personality traits.
	These conclusions provide novel support for the existence of an automatic and ubiquitous self-heuristic that biases representation formation and subsequent perception of novel people and objects.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: A highly accessible network of self-representation biases attention and memory in favour of self-relevant information. I investigated how this network mediates representation of novel people and novel objects, stimulus categories that have received little attention in the social cognitive literature.  An implicit test of cognitive association strength (i.e. the Implicit Association Test) revealed that novel self-similar (versus self-dissimilar) people and owned (versus unowned) objects are immediately associated to the self network. The new representations led to perceptual biases through first-order associations, whereby strictly self-relevant information was generalized to self-similar people and owned objects. For instance, even minimal self-similarity to a novel individual biased memory retrieval and reconstruction so that the retrieved information was consistent with the expectation of self-similarity. Together, the findings highlight the ubiquity and automaticity with which self-associations mediate cognitive representations and consequent perceptions of novel people and objects in realistic social situations.


title: MRI Velocity Quantification Implementation and Evaluation of Elementary Functions for the Cell Broadband Engine

contributor:
Anand, Christopher Kumar
Computing and Software

subject: MRi velocity, quantification, implementation, elementary functions, cell, broadband engine, regularization parameters

abstract:
 Magnetic Resonance Imaging (MRI) velocity quantification is addressed in part I of this thesis. In simple MR imaging, data is collected and tissue densities are displayed as images. Moving tissue creates signals which appear as artifacts in the images. In velocity imaging, more data is collected and phase differences are used to quantify the velocity of tissue components. The problem is described and a novel formulation of a regularized, nonlinear inverse problem is proposed. Both Tikhonov and Total Variation Regularization are discussed. Results of numerical simulations show that significant noise reduction is possible.

 The method is firstly verified with MATLAB. A number of experiments are carried out with different regularization parameters, different magnetic fields and different noise levels. The experiments show that the stronger the complex noise is, the stronger the magnetic field requires for estimating the velocity. The regularization parameter also plays an important role in the experiments. Given the noise level and with an appropriate value of regularization parameter, the estimated velocity converges to ideal velocity very quickly. A proof-of-concept implementation on the Cell BE processor is described, quantifying the performance potential of this platform.

 The second part of this thesis concerns the evaluation of an elementary function library. Since CBE SPU is designed for compute intensive applications, the well developed Math functions can help developer program and save time to take care other details. Dr. Anand's research group in McMaster developed 28 math functions for CBE SPU. The test tools for accuracy and performance were developed on CBE. The functions were tuned while testing. The functions are either competitive or an addition to the existing SDK1.1 SPU math functions.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: The Study of Architectured Materials with a Corrugated Geometry

contributor:
Zurob, Hatem
Materials Science and Engineering

subject:
Materials Engineering
Composite Materials
Corrugated Materials
Architectured Materials
Finite Element Modeling

abstract: Compared to materials with a straight geometry, materials with a corrugated architecture have shown potential to improve ductility without sacrificing strength due to the unbending of the corrugation during loading. The purpose of this research was to study the effect of geometric and material parameters on the stress-strain response of materials with a corrugated geometry and understand what controls the unbending process and under what conditions improved ductility was achievable. This involved studying isolated corrugations and corrugation reinforced composites under tensile and transverse compressive loading by performing parametric studies using Finite Element Modeling (FEM) simulations. These simulations showed that improvements in ductility are directly related to the degree of corrugation present and can be attributed to an initial bending dominated process. The unbending of the corrugation leads to an evolving geometry which causes the material to strengthen and ultimately delays necking. For corrugated composites, it was found that there is significant interplay between the properties of the components and the geometry of the corrugation. To obtain a benefit in ductility through corrugation, the matrix must have sufficiently high work hardening to accommodate the unbending corrugation without itself necking, but also have sufficiently low flow stress relative to the reinforcement yield strength to prevent the corrugation from stretching instead of unbending. Also, if the boost in work hardening from unbending occurs too early, no gain in ductility is achieved. In addition to these findings, tools for predicting the strength and ductility of these materials were developed, including an analytical model for the isolated corrugations and a series of benefit maps and surfaces for the corrugated composites. These tools proved to be fairly effective. Finally, the FEM findings were compared to experimental stress-strain curves and strain maps for validation and showed relatively good qualitative agreement.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: It is uncommon to find a material that possesses both high strength as well as the ability to elongate a lot without failing. One way to achieve this combination of properties is to use a wavy or corrugated structure that provides increased elongation when loaded due to the straightening of the corrugation. The purpose of this thesis was to study how materials which possess a wavy or corrugated geometry behave when they are subjected to a stretching load. This research utilized computer simulations and simple experimental testing to evaluate both isolated corrugations and corrugations embedded in another material. It was found that the amount of improvement in elongation is dependent on the initial amount of waviness. Also, whether a material shows improved elongation depends on whether the corrugation is able to unbend, which in turn depends on the corrugation geometry and the relative mechanical properties of the two materials.


title: Quantitative Multi-Phase Field Modeling of Polycrystalline Solidification in Binary Alloys

contributor:
Zurob, H.S.
Provatas, N.
Materials Science and Engineering

subject: quantitative, multi-phase, field modeling, polycrystalline, solidification, binary alloys, equiaxed dendritic growth, interface

abstract:
This thesis develops a new quantitative multi-phase field model for polycrystalline
solidification of binary alloys. We extend the thin interface formalism of Karma and co-workers to multiple order parameters. This makes it possible to model segregation and interface kinetics during equiaxed dendritic growth quantitatively, a feature presently lacking from polycrystalline or multi-phase solidification models. We study dendrite tip speed convergence as a function of interface width during free dendritic growth. We then analyze the steady state and grain coalescence properties of the model. It is shown that the model captures the correct physics of back diffusion and repulsive grain boundary coalescence as outlined by Rappaz and co-workers. Finally, the model is applied to simulate solidification and coarsening in delta-ferrite solidification.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Pseudomonas aeruginosa minor pilins regulate virulence via modulation of FimS-AlgR activity

contributor:
Burrows, Lori
Biochemistry and Biomedical Sciences

subject:
pseudomonas aeruginosa
type iv pili
virulence
caenorhabditis elegans
alginate
biofilms

abstract: The type IV pilus is a motility organelle found in a range of bacteria, including the opportunistic pathogen Pseudomonas aeruginosa. These flexible fibres mediate twitching motility, biofilm maturation, surface adhesion, and virulence. The principle structural protein of the pilus is the major pilin, PilA, while a set of low abundance “minor pilins” are proposed to constitute the pilus tip. The minor pilins, FimU and PilVWXE, along with the non-pilin protein PilY1, prime assembly of surface-exposed pili. The fimU-pilVWXY1E operon is positively regulated by the FimS-AlgR two-component system. Independent of pilus assembly, PilY1 is an adhesin and mechanosensor that, along with PilW and PilX, triggers virulence upon surface attachment. Here, we aimed to uncover the mechanism for PilWXY1-mediated virulence. We hypothesized that loss of PilWXY1 would relieve feedback inhibition on FimS-AlgR, resulting in increased transcription of the minor pilin operon and dysregulation of virulence factors in the AlgR regulon. Caenorhabditis elegans slow killing assays revealed that pilW, pilX, and pilY1 mutants had reduced virulence relative to a pilA mutant, implying a role in virulence independent of pilus assembly. FimS-AlgR were required for the increased promoter activity of the minor pilin operon upon loss of pilV, pilW, pilX, or pilY1. Overexpression or hyperactivation of AlgR by point mutation led to reduced virulence, and the virulence defects of pilW, pilX, and pilY1 mutants were dependent on FimS-AlgR expression. We propose that PilWXY1 inhibit their own expression at the level of FimS-AlgR, such that loss of pilW, pilX, or pilY1 leads to FimS-mediated activation of AlgR, and reduced expression of acute-phase virulence factors. Accumulation of mutations in the minor pilin operon may represent an evolutionary strategy for P. aeruginosa populations in chronic lung infections, as loss of PilWXY1 would upregulate the expression of AlgR-dependent virulence factors – such as alginate – characteristic of such infections.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: Pseudomonas aeruginosa is a bacterium that causes dangerous infections, including lung infections in cystic fibrosis patients. The bacteria use many strategies to infect their hosts, one of which involves a grappling hook-like fibre called the type IV pilus. There are many components involved in assembly and function of the pilus, including five proteins called “minor pilins” and a larger protein called PilY1 that may help the pilus detect surface attachment. We used a roundworm infection model to show that loss of PilY1 and specific minor pilins leads to delayed killing, while loss of other pilus proteins has no effect on worm survival. This effect was due to increased activation of a regulatory system called FimS-AlgR that inhibits expression of other factors used by this bacterium to infect its hosts. By studying how P. aeruginosa causes infection, we can design better strategies to disarm it and reduce the severity of infections.


title: Automated 3D Visualization of Brain Cancer

contributor:
Doyle, Thomas
eHealth

subject:
visualization
segmentation
decision making
clinical workflow
brain cancer

abstract: Three-dimensional (3D) visualization in cancer control has seen recent progress due to the benefits it offers to the treatment, education, and understanding of the disease. This work identifies the need for an application that directly processes two-dimensional (2D) DICOM images for the segmentation of a brain tumor and the generation of an interactive 3D model suitable for enabling multisensory learning and visualization. A new software application (M-3Ds) was developed to meet these objectives with three modes of segmentation (manual, automatic, and hybrid) for evaluation. M-3Ds software was designed to mitigate the cognitive load and empower health care professionals in their decision making for improved patient outcomes and safety. Comparison of mode accuracy was evaluated. Industrial standard software programs were employed to verify and validate the results of M-3Ds using quantitative volumetric comparison. The study determined that M-3Ds‘ hybrid mode was the highest accuracy with least user intervention for brain tumor segmentation and suitable for the clinical workflow. This paper presents a novel approach to improve medical education, diagnosis, treatment for either surgical planning or radiotherapy of brain cancer.

abstract: Thesis

abstract: Master of Science (MSc)


title: Characterization of the PilS-PilR two component regulatory system of Pseudomonas aeruginosa

contributor:
Burrows, Lori L
Biochemistry

subject:
Pseudomonas aeruginosa
Type IV pili
Two-component System

abstract: Two-component regulatory systems are an important means for most prokaryotes to adapt quickly to changes in their environment. Canonical systems are composed of a sensor kinase, which detects signals that trigger autophosphorylation, and a response regulator, which imparts changes within the cell, usually through transcriptional regulation. The opportunistic pathogen, Pseudomonas aeruginosa, expresses a plethora of two-component systems including the PilS-PilR sensor-regulator pair, which directs transcription of the major component of the type IV pilus (T4P) system, pilA, in response to an unknown signal. T4P are surface appendages that are required for full virulence, as they perform several important functions including twitching motility, cell surface attachment, surface sensing, and biofilm formation. While loss of pili is known to decrease virulence, the effect of surplus surface pili on pathogenicity was unknown. In other T4P-expressing bacteria, PilR regulates the expression of non-T4P related genes, but its regulon in P. aeruginosa was undefined. Here, we identify PilA as an intramembrane signal for PilS, regulating its own expression. When PilS-PilR function is altered through the use of activating point mutations, which induce hyperpiliation, pathogenicity in C. elegans was significantly impaired compared to both wild type and non-piliated strains of P. aeruginosa. This phenotype could be recapitulated using other hyperpiliation-inducing mutations, providing evidence that over production of surface pili likely prevents productive engagement of contact-dependent virulence factors. Last, transcriptomic analyses revealed that expression of over 50 genes – including several involved in flagellar biosynthesis and function – is modulated by PilSR, suggesting coordinate regulation of motility in P. aeruginosa. Together, this work provides new information on the control of pilA transcription and suggests novel roles for surface pili and the PilSR two component system in virulence and swimming motility, respectively. The knowledge gained from this work could be applied to the development of a PilS or PilR based anti-virulence therapeutic.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Pseudomonas aeruginosa is a Gram negative bacterium and a common cause of hospital acquired infections. The World Health Organization recently ranked P. aeruginosa as one of the top “priority pathogens” for which new treatments are desperately needed, in part due to its intrinsic resistance to many antibiotics. Among the key features that contribute to the infectivity of P. aeruginosa are its Type IV pili (T4P), which are flexible, retractile surface appendages involved in cell surface attachment, movement across solid surfaces and other important functions. Production of the major pilin protein, PilA, which forms most of the pilus, is tightly controlled by the two-component regulatory system, PilS-PilR, where PilS is a sensor and PilR is a regulator that directly controls pilin expression. The aim of this work was to identify the signal(s) detected by the sensor, as well as additional genes or systems under PilSR control. We showed that the pilin protein interacts directly with the sensor to control its own expression, and that dysregulation of the PilS-PilR two-component system impairs both pathogenicity and other forms of motility. Together, the data presented here provide insight into how PilS-PilR control expression of systems required for virulence of P. aeruginosa and highlight the potential of these proteins as possible therapeutic targets.


title: Discriminant Analysis for Longitudinal Data

contributor:
McNicholas, Paul
Mathematics and Statistics

subject:
mixture models
supervised learning
longitudinal data
classification
statistical learning

abstract:
Various approaches for discriminant analysis of longitudinal data are investigated,
with some focus on model-based approaches. The latter are typically based on the
modi ed Cholesky decomposition of the covariance matrix in a Gaussian mixture;
however, non-Gaussian mixtures are also considered. Where applicable, the Bayesian
information criterion is used to select the number of components per class. The
various approaches are demonstrated on real and simulated data.

abstract: Thesis

abstract: Master of Science (MSc)


title: Fabrication and Characterization of GaAsP Nanowire-on-Silicon Tandem Photovoltaic Cells

contributor:
LaPierre, Ray
Engineering Physics

subject:
III-V
nanowire
photovoltaics
tandem cell

abstract:
One-dimensional vertical nanostructures, nanowire arrays, are investigated for applications in photovoltaics.  Specifically, III-V core-shell p-i-n nanowire arrays are grown by molecular beam epitaxy on silicon substrates, using the self-assisted vapour-liquid-solid growth method.  GaAs1-xPx nanowires are grown with an optimized composition to maximize the potential efficiency of a GaAsP nanowire-on-silicon tandem solar cell under AM1.5G illumination.  Photovoltaic devices are fabricated and assessed by optical and electrical characterization techniques, to identify areas for refinement of device design and processing.
Combining the unique properties of nanowire arrays, the quality and tunability of III-V materials, and the economics and infrastructure of silicon-based device fabrication, this work examines a novel approach to affordable renewable energy.
Methods of substrate removal via etching are investigated for optical characterization of nanowire arrays, and an improved technique for electrical characterization of ITO contacts is explored.  The first nanowire-on-silicon tandem device utilizing a radial p-n junction nanowire structure is reported, achieving an open circuit voltage of 1.2 V, a short circuit current density of 7.6 mA/cm2, a fill factor of 40%, and an efficiency of 3.5%.  Finally, projects for future improvements to the work described herein are suggested.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Magnetocaloric Effect in Iron-Phosphide Based Phases

contributor:
Mozharivskyj, Yurij
Chemistry

subject:
Magnetocaloric effect
Fe2P
Iron Phosphide
Entropy change
MCE
magnetization
magnetic cooling
(Mn,Fe)2(Si,P)
x-ray diffraction
arrot plot
arc melting
sintering

abstract:
Ever since the discovery of the giant magnetocaloric effect (GMCE) in the Gd5(Si,Ge)4 phases, magnetic cooling has gained significant interest because of its potential environmental benefits and increased efficiency compared to vapour-based refrigeration. This current work is focused on one of the most promising GMCE systems, the (Mn,Fe)2(Si,P) materials. An alternative synthetic route has been explored for the Mn2-xFexSi0.5P0.5 and MnFeSiyP1-y series which is capable of producing phase-pure samples. The new preparation technique eliminates common impurities that arise from established methods thus providing a more accurate description of the structural and physical properties. The low cost, non-toxicity, abundance of starting materials and easy tuning of the magnetic properties make these materials desirable for potential applications.
Phase-pure magnetocaloric Mn2-xFexSi0.5P0.5 materials (x = 0.6, 0.7, 0.8, 0.9) were synthesized through arc-melting followed by high temperature sintering. Structural features of samples with x = 0.6, 0.9 were studied through temperature dependent synchrotron powder x-ray diffraction. Magnetic measurements established the Curie temperature, thermal hysteresis, and magnetic entropy change of this system. According to the diffraction and magnetization data, all of the samples were shown to have a first-order magnetostructural transition which becomes less pronounced for Mn-richer samples.
The MnFeSixP1-x phases (x = 0.30, 0.35, 0.40, 0.48, 0.52, 0.54, 0.56) have also been synthesized by the same method. For the first time, single crystals of x = 0.30, 0.40 were successfully grown. Variable temperature x-ray diffraction experiments for x = 0.30 were completed which show the structural changes across the phase transition. This structural data was complemented with magnetization data providing Curie temperatures and thermal hysteresis.

abstract: Thesis

abstract: Master of Science (MSc)


title: Three Essays on Product Recall Decision Optimization

contributor:
Parlar, Mahmut
Business

subject: product recall optimization, dynamic programming, newsvendor

abstract:
This thesis examines decision optimization of product recalls. Product recalls in recent years have shown unprecedented impact on both immediate economic and reputational damage to the company and long-lasting impact on the brand and industry. Admittedly, imperfect product quality makes recalls inevitable. Thus, we explore from three perspectives to elicit business insights regarding better management and risk control.
    Chapter 1 introduces the topic of product recall management optimization and its real-world motivation.
    Chapter 2 views the decision making of "when to initiate a product recall" as a dynamic process and takes the feedback of customer returns to update the product defect rate. Updating is simplified by the conjugate properties of beta distribution and Bernoulli trials. We develop the optimal stopping model to find the thresholds of total product returns above which initiating recall is optimal. We implement dynamic programming to solve the model optimally. For large-size problems, we propose a simulation method to balance computation time with solution quality.
    Chapter 3 allows the company to control the recall risk by investing in quality. We adopt the one-stage stochastic newsvendor model and add quality-dependent recall risk. The resulting model is not concave in production quantity and quality levels. The parametric analysis reveals several interesting features such as the optimal ordering quantity and quality level have a conflicting relationship. We further extend our model from internal supply to external supply from multiple sources.
    Chapter 4 examines managing product recalls from the closed-loop supply chain management and disruption management perspectives. We model the location and allocation decisions of both manufacturing plants and reprocessing facilities where facilities are built after the recalls. Numerical experiments show the costs of overlooking potential recalls vary greatly, indicating the necessity of considering recalls in initial designs and the importance of accurate recall probability prediction.
    Chapter 5 summarizes.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: The Evolution of Antibiotic Production in a Spatial Model of Bacterial Competition

contributor:
Higgs, Paul
Biology

subject:
bacteria
antibiotics
spatial model
competition
cooperation
rock paper scissors

abstract: Bacteria occupy a wide range of niches with many different types coexisting. They compete directly, with some capable of producing antibiotics that kill other members of the niche. Despite this, long term survival of these ecosystems is possible. Here, we consider a lattice-based three-component system with antibiotic producers, non-producers (or cheaters), and susceptible cells competing.  In our system, there is a metabolic cost tied to production rate, resulting in a decrease in growth rate for the producers. Non-producers behave as cheaters that gain the benefit of an antibiotic without the cost of producing it themselves. The susceptible cells are a faster growing different species. The model behaves in a fashion similar to the game “rock-paper-scissors", because producers beat susceptible cells, non-producers beat producers, and susceptible cells beat non-producers. We consider two spatial lattice models, one in which there is a nearest neighbour interaction between cells, and one in which the long-range diffusion of the antibiotic is explicitly included. We consider the parameter space in which the three cell types can coexist (taking into account cost and production rate), and determine the regions in which production rate is too high or too low to allow coexistence. We determine that antibiotic producers will evolve to an optimal production rate and that low-rate producers can outcompete complete cheaters (non-producers). We finally illustrate that the introduction of a fourth “resistant” cell type allows the system to survive with four members for some parameters. In other cases, addition of the resistant cells causes the extinction of the producers, which eventually favours the susceptible cells.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: We looked at computational models of bacterial interaction involving producers, non-producers, and susceptible cell types that interacted in a manner similar to the game “rock-paper-scissors”. We determined that the system is stable for the long term for a given set of parameters, otherwise susceptible cells win as not enough antibiotic is being produced, or too much is being produced, significantly inhibiting the growth of producers. Moreover, we found that these systems can evolve, tending towards one production rate, in order to better allow the system to survive. Non-producers also evolve, tending to low production rates instead. These results have implications in understanding bacteria that cannot be cultured and perhaps aiding in the discovery of novel antibiotics.


title: COMPUTATIONAL FRAMEWORK FOR THE GENERALIZED BERGE SORTING CONJECTURE

contributor:
Deza, Antoine
Computing and Software

subject: Berge Sorting

abstract: In 1966, Claude Berge proposed the following sorting problem. Given a string of n alternating white and black pegs, rearrange the pegs into a string consisting of all white pegs followed immediately by all black pegs (or vice versa) using only moves which take 2 adjacent pegs to 2 vacant adjacent holes. Berge's original question was generalized by considering the same sorting problem using only Berge k-moves, i.e., moves which take k adjacent pegs to k vacant adjacent holes. Let h(n,k) denote the minimum number of Berge k-moves to sort a string of n alternating white and black pegs.The generalized Berge sorting conjecture states that h(n,k) is equal to the ceiling of n/2 for any k and large enough n. We develop a computational framework to determine h(n,k) for small instances with a focus on the most computationally challenging instances; that is, the determination of (k+2,k).

abstract: Thesis

abstract: Master of Applied Science (MASc)