Electrical impedance tomography is an imaging method with applications to geophysics and medical imaging. A new approximation is presented based on Nachman's 2-dimensional construction for closed domains. It improves upon existing approximations by extending the range of application from resolving 2 times the surface conductivity to imaging perfect conductors and insulators. With perfect knowledge of boundary data, this approximation exactly resolves a single conductive disc embedded in a homogenous domain. The problem, however, is ill-posed, and imaging performance degrades quickly as the distance from the boundary increases. The key to the approximation lies in (a) approximating Fadeev's Green's function (b) pre-processing measured voltages based on a boundary-integral equation (c) solving a linearized inverse problem (d) solving a d-bar equation, and (e) scaling the resulting image based on analytical results for a disc. In the development of the approximation, a new formula for Fadeev's Green's function is presented in terms of the Exponential Integral function. Also, new comparisons are made between reconstructions with and without solving the d-bar equation, showing that the added computational expense of solving the d-bar equation is not justified for radial problems. There is no discernible improvement in image quality. As a result, the approximation converts the inverse conductivity problem into a novel one-step linear problem with pre-conditioning of boundary data and scaling of the resulting image. Several extensions to this work are possible. The approximation is implemented for a circular domain with unit conductivity near the boundary, and extensions to other domains, bounded and unbounded should be possible, with non-constant conductivity near the boundary requiring further approximation. Ultimately, further research is required to ascertain whether it is possible to extend these techniques to imaging problems in three dimensions.

This thesis aims to develop an architectural zone for contact between two boroughs in Montreal: Mont-Royal and Rosemont-la-Petite-Patrie; these boroughs are divided by the Canadian Pacific Railway as well as the Van Horne viaduct. Empty lots along the the fringe of the railway are used by the artistic population, which has appropriated the industrial buildings and empty lots that border the rail line. Citizens also use informal passways to cross the railway and viaduct. The proposal of this thesis is to develop an urban space that will improve social cohesion and encourage unfettered access, by setting up safe crossings and encouraging the spread of arts and culture without changing the character of the site. The focus of this project is to support and develop, through architectural design, the social interaction that people create. It also aims to create an architecture of resistance to preserve the informal residual parks that border the railway. / I propose architecture of resistance, because I stand firmly against future developments. The rounded silhouette of my architecture is the result of my goal to preserve the parkland that already exists and works. By not altering the surroundings, I maintain the artistic community in the sector. Architecture of resistance is a form of opposition that residents of the sector already execute in their own way. Graffiti artists leave their traces on the walls, sculptors claim vacant land with found materials and people form committees to protect their surroundings. My proposal supports resistance to future development in the site and I am pleased to take part in that movement.

The MexCD-OprJ multidrug efflux pump of Pseudomonas aeruginosa confers resistance to a range of antimicrobials. Although not expressed under normal laboratory conditions, exposure to the membrane-active biocides, chlorhexidine or benzalkonium chloride, results in mexCD-oprJ expression. This suggests that membrane disruption provides the inducing signal. Consistent with this, increased mexCD-oprJ expression was demonstrated in the presence of additional membrane-damaging agents including polymyxin B, ethanol, SDS, EDTA, the organic solvents n-hexane and p-xylene, and the antimicrobial peptides melittin, V8 and V681. MexCD-OprJ expression was initially verified through increased resistance to known MexCD-OprJ antimicrobial substrates and subsequently using a mexC-lacZ transcriptional fusion and RT-PCR. Since the P. aeruginosa sigma factor AlgU is responsive to envelope stress, it was of interest to ascertain whether AlgU is capable of mediating this increased mexCD-oprJ expression. Thus, the impact of AlgU loss on mexCD-oprJ expression in response to membrane-damaging agents was assessed in a algU strain. In contrast with above, little or no mexCD-oprJ expression (assessed using resistance to MexCD-OprJ antimicrobial substrates, the mexC-lacZ transcriptional fusion and RT-PCR) occurred in response to membrane-damaging agents in the algU strain, consistent with AlgU playing a role in the envelope stress inducibility of mexCD-oprJ. Overall, envelope stress, and the ability to react to this stress through AlgU, appears to play an important role in mexCD-oprJ induction. This suggests an important role for MexCD-OprJ in alleviating envelope stress, independent of its ability to export and provide resistance to antimicrobials. A gene, PA4596, whose product shows substantial homology to the NfxB repressor of mexCD-oprJ expression, occurs downstream of mexCD-oprJ and shows AlgU-dependence and chlorhexidine inducibility, suggesting a role in the chlorhexidine-induced, AlgU-mediated expression of mexCD-oprJ. Thus, the impact of PA4596 loss on mexCD-oprJ expression was assessed. Paradoxically, the loss of PA4596 increases mexCD-oprJ expression in wild-type cells in response to chlorhexidine treatment (as assessed through RT-PCR), while its loss compromises mexCD-oprJ expression in an nfxB mutant. Nonetheless, this suggests that PA4596 is involved in the induction of mexCD-oprJ and that its ability to induce mexCD-oprJ differs depending on the state of nfxB. / Thesis (Master, Microbiology & Immunology) -- Queen's University, 2007-07-31 12:03:52.535

The ATP-binding cassette (ABC) transporter superfamily consists of 49 members, to which both Multidrug Resistance Protein 1 (MRP1/gene symbol: ABCC1) and MRP4 (ABCC4) belong. Single nucleotide polymorphisms (SNPs) in drug metabolizing genes have been shown to affect individual responses to drugs and toxins. However, the role of SNPs in modulating the activity of drug transporters, such as MRP1 and MRP4, is poorly characterized. The overall goal of my thesis was to determine the effects of SNPs in the promoter regions of human ABCC1 and ABCC4. For MRP1/ABCC1, two proximal promoter SNPs (-275A>G, -260G>C) were identified in the literature and recreated in vitro, and the activity of the mutant ABCC1 promoter constructs was measured in five human cell lines using a dual luciferase assay. The activity of the -275A>G promoter was comparable to the wild-type ABCC1 promoter. On the other hand, the -260G>C substitution decreased ABCC1 promoter activity in HepG2, MCF-7 and HeLa (40 - 60%) cells. A 1706 bp fragment containing the 5’-flanking and untranslated regions of ABCC4 were isolated from two bacterial artificial chromosome clones and six serially deleted ABCC4 promoter reporter constructs generated. Luciferase assays of the basal promoter constructs of ABCC4 in HEK293T cells revealed the presence of one or more negative regulatory regions between -1706 and -876, between -876 and -641, and one or more positive regulatory regions between -641 and -356, and between -356 and -17. Also, the ABCC4 promoter displayed differential activity in MDCKI and LLC-PK1 cells than in HEK293T cells. One SNP (-523G>C) was identified from an online database and its activity tested. However, -523G>C SNP did not cause any significant change in the ABCC4 promoter activity in both HEK293T and HepG2 cells (80 – 130%). In summary, the data obtained suggest that the promoter SNPs studied may affect the transcriptional activity of ABCC1 or ABCC4, but it seems likely that this is not true in all cell types. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2007-09-28 10:03:16.119

MRPs mediate the ATP-dependent efflux of a structurally diverse array of compounds. Certain MRPs, including MRP1, MRP2 and MRP4, are involved in multidrug resistance in tumour cells, while in non-malignant cells these MRPs can influence the distribution and/or elimination of many clinically important drugs. In addition, these MRPs mediate the efflux of physiological metabolites, many of which are conjugated organic anions. Modulation of the drug transporting activity of MRP1 (and to a lesser extent MRP2 and MRP4) has been a long sought after therapeutic objective. In this study, the modulatory abilities of five structurally distinct classes (I-V) of chalcogenopyrylium dyes (CGPs) were examined utilizing an in vitro assay which measures inhibition of radiolabeled estradiol glucuronide ([3H]E217βG) (a prototypical MRP substrate) uptake into inside-out membrane vesicles prepared from MRP-transfected human embryonic kidney (HEK) cells. Additionally, some CGPs were tested in a calcein efflux assay using intact MRP1-transfected HEK cells. Sixteen of 34 CGPs initially tested at a single concentration (≤30 μM) inhibited MRP1-mediated uptake by >50%, with IC50’s ranging from 0.7-7.6 μM. Of the 9 CGPs with IC50’s ≤2 μM, five belonged to Class I, two to Class II, and two to Class IV. When tested in the calcein efflux assay, only 4 of 16 CGPs inhibited MRP1-mediated cellular efflux by >50% (I-3, -4, -6, IV-1) while a fifth (II-5) inhibited efflux by 23%. These five CGPs were then tested as modulators of [3H]E217βG uptake by MRP2 and MRP4. Their effects on MRP2 transport activity were differential with two (I-4, I-6) inhibiting transport (IC50’s 2.0, 7.1 μM), two (I-3, IV-1) stimulating transport (>2-fold), while II-5 had no effect. On the other hand, all five CGPs inhibited [3H]E217βG uptake by MRP4, but less effectively than by MRP1. Finally, five analogs of CGP IV-1 were tested for their effects on MRP1, MRP2 and MRP4 [3H]E217βG uptake, but none were more efficacious than CGP IV-1. The CGPs tested here represent novel MRP1, MRP2 and MRP4 modulators with variable effects on transport activities. These CGPs may represent a new avenue for the development of clinically applicable modulators of MRP proteins involved in multidrug resistance. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2011-11-28 17:50:49.432

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Cytochrome P4501A (CYP1A), a xenobiotic metabolizing enzyme found in allvertebrates, is highly induced following exposure to a number of organic contaminants.Several populations of teleosts residing in highly contaminated areas have been found toexhibit resistance to the toxic effects of contaminants, a condition characterized byreduced expression of CYP1A.Within this work I demonstrated that expression of CYP1A mRNA, protein, andactivity in caged rainbow trout (Oncorhynchus mykiss) was an effective biomarker ofpolychlorinated biphenyl (PCB) contamination. Furthermore, through the use of bothlaboratory and field studies, I demonstrated that several species inhabiting a PCBcontaminated site exhibited either acquired (Ameiurus natalis) or natural (Lepomiscyanellus) resistance to the CYP1A inducing effects of PCBs. Further studiescharacterized the response of several other Lepomis species to CYP1A inducingcompounds, demonstrating that the natural resistance of L. cynaellus is a characteristicshared by at least two other members of the genus. Lepomis species were relativelyinsensitive to CYP1A induction following PCB exposure yet exhibited highly inducedCYP1A levels following exposure to another CYP1A inducer, the model polyaromatichydrocarbon benzo[a]pyrene (BaP), suggesting a number of species within the genusLepomis may display natural resistance to certain classes of CYP1A inducingcompounds.Additional studies using responsive and resistant populations of killifish wereused to examine the consequences of resistance on fish physiology. Thyroid hormones,known to be altered by PCBs in mammals, were variable but did not differ significantlybetween responsive and resistant fish following PCB exposure. Treatment with PCBssuppressed production of the egg yolk precursor protein vitellogenin in primaryhepatocytes of responsive fish. Studies examining the developmental impacts of toxicantexposure demonstrated altered aspects of development in PCB responsive but notresistant Fundulus heteroclitus embryos exposed to polybrominated diphenyl ethers(PBDEs), compounds structurally related to PCBs. PBDE exposure in juvenile Ictaluruspunctatus failed to induce CYP1A or uridine diphosphate glucuronyltransferase(UDPGT) activity indicating PBDEs do not impact these commonly measuredtoxicological endpoints. The findings of this work describe novel pollutant responses in anumber of species with varying degrees of pollutant sensitivity and contribute to theunderstanding of toxicant induced alterations in teleost physiology.

The fire resistance of timber connections is relatively unknown in the construction and design industries even though they are widely used. This research focuses on the fire resistance of nailed, screwed, bolted and self-drilling doweled connections in laminated veneer lumber (LVL) timber. These connections have been found to have high strength under cold or normal temperature but hardly achieved 30 minutes fire rating in the furnace tests. To establish the performance of connections, an investigation was carried out on the compressive strength of connections by having compressive tests using an Instron Testing Machine. Similar connections were tested at simulated fire conditions under constant load in a custom-built furnace. The different fasteners used and the arrangement of the connections gave different connection strengths at ambient and elevated temperature.