Surface analysis of buna-N-rubber and teflon was performed. Scanning electron microscopy was used to analyze the topography of both materials and x-ray microanalysis identified the elemental chemical composition of the polymers. Teflon was primarily a smooth surface with random irregular spots, while buna-N-rubber had a very rough topography with "caverns" and crevices spread over the surface. The x-ray microanalysis showed that there are no impurities on the surface of teflon; however, calcium, silicone and sulfur were present on the surface of buna-N-rubber. Water contact angle measurements indicated that buna-N-rubber was a more hydrophobic surface than teflon. Qualitative analysis of the attachment of Pseudomonas fragi A TCC 4973, Listeria monocytogenes Scott A and Bacillus cereus ATCC 11778 to buna-N-rubber and teflon was assessed by scanning electron microscopy. These bacteria readily attached to both surfaces. Pseudomonas fragi attached after 2 hours in the presence of this microoorganism and Bacillus cereus and Listeria monocytogenes attached at 12 and 24 hours, respectively. Quantitative analysis of the attachment of Pseudomonas fragi to both surfaces as affected by various milk fat concentrations and temperature, and the availability of nutrients (different dilutions of skim milk, casein, casein and lactose, and whey and lactose) was conducted. Attachment was assessed by impedance microbiology. Milk fat content did not play a significant role in the process of attachment of this organism to either type of surfaces; however, significantly greater numbers attached to buna-N-rubber than to teflon. Overall bacteria attached in higher numbers to both surfaces when grown at 21°C, compared to bacteria grown at 4°C. For buna-N-rubber, bacteria attached in significantly higher numbers when the concentration of nutrients was minimal, while for teflon, the results were, in most cases, opposite to these. / Ph. D.

Variations in ATP content in three ground beef spoilage bacteria, Lactobacillus brevis, Lactobacillus jensenii, and Pseudomonas sp. were investigated using the bioluminescence (luciferin-luciferase) assay. Environmental factors (temperature, atmosphere, pH, aeration, and phase of growth), as well as differences among genera and species, were studied in relation to their effect on cellular ATP. Variations for each of the environmental factors and bacteria were shown statistically to be significantly different at the 0.05 level. The mean ATP/cell for each of the bacteria was 2.71 fg/cell (L. brevis), 2.20 fg/cell (L. jensenii), and 1.36 fg/cell (Pseudomonas sp.). For all three bacteria, ATP/cell was lower and more stable throughout the culture's growth cycle at 3°C or in N₂. In general, ATP/cell increases from a lowest value in lag phase to a highest value in stationary phase. The effect of sonication on ATP/cell was tested for each bacterium at one set of factors. Sonication studies showed that L. brevis cells were clumping, especially in aged cultures. After sonication, ATP/cell remained relatively constant from lag through stationary phase. L. jensenii showed no signs of clumping and ATP/cell increased as the culture aged. Sonication had a lethal effect on the Pseudomonas. Thus the ATP/cell for Pseudomonas increased dramatically as the culture aged. Guidelines concerning temperature, assumed ATP content for major contaminants, and sample handling must be followed in order to use the bioluminescence assay to estimate biomass in foods. / M.S.

Escherichia coli (E. coli) is a gram-negative bacteria found in the intestinal system of humans that can also contaminate food, drinking water, as well as lakes and rivers. While not all strains are pathogenic, some including O157:H7 can cause severe illness. Conventional methods of detecting E. coli contamination in water samples often have limitations for on-site testing applications, which can include their slow detection time or need for expensive laboratory equipment. While several fluorescent biosensors for the detection of E. coli have been developed in the Didar lab, there is increased interest in colourimetric biosensors whose signal can be interpreted with the naked eye. This thesis will describe the development and performance of a hydrogel biosensor, that is made of polyacrylamide chains crosslinked by an E. coli detecting Deoxyribozyme (DNAzyme) and its substrate. In the presence of E. coli, the DNAzyme cleaves its substrate and crosslinking breaks down, resulting in the visible dissolution of the hydrogel. Paired with the use of bacteriophage induced cell lysis to amplify the target protein, detection sensitivity to the order of 10^1 CFU/mL has been achieved using this platform with an incubation time of 18 hours. A convolutional neural network (CNN) trained on optical images of the platform was able to classify samples as contaminated or uncontaminated with a validation accuracy of over 93%. / Thesis / Master of Applied Science (MASc) / Microbial contamination of water sources including surface water, groundwater, and drinking water can pose risks to human health. One bacterial species that can sometimes contaminate these sources is Escherichia coli (E. coli). To determine if E. coli is present in a water sample, it often needs to be sent to a laboratory for testing, which can be time consuming and inconvenient. Therefore, researchers are working to develop new sensors that are able to detect E. coli from water samples, ideally being simple enough to use that testing could be done right away and without sending the sample to another location. In this research project, we have developed a new biosensor that can detect E. coli in water samples. To use the sensor, a water sample is added onto a small red gel in a tube, and this gel breaks apart if E. coli is present in the sample.

A critical first step to improving existing and designing future wide-area networks is an understanding of the load placed on these networks. Efforts to model traffic are often confounded by atypical traffic - traffic particular to the observation site not ubiquitously applicable. The causes and characteristics of atypical traffic are explored in this thesis. Atypical traffic is found to interfere with parsimonious analytic traffic models. A detection and modeling technique is presented and studied for atypical traffic characterized by strongly clustered inliers. This technique is found to be effective using both real-world observations and simulated data. Another form of atypical traffic is shown to result in multimodal distributions of connection statistics. Putative methods for bimodal estimation are reviewed and a novel technique, the midpoint-distance profile, is presented. The performance of these estimation techniques is studied via simulation and the methods are examined in the context of atypical network traffic. The advantages and disadvantages of each method are reported. / Master of Science

An alternative on-site wastewater treatment and disposal system (OSWTDS) consisting of a soil infiltrator with low pressure distribution was evaluated in a soil that was unsuitable for a conventional OSWTDS under current Commonwealth of Virginia Sewage Handling and Disposal Regulations, due to a shallow seasonally perched water table and low hydraulic conductivity. The absorption field consisted of two subsystems numbered as 1 and 2 with effluent design loading rates of 5.1 and 10.2 Lpd/m2, respectively (actual loading rates of 2.4 and 4.9 Lpd/m2, respectively). Soil matric potentials compared seasonally for each subsystem and indicated that both provided similar hydraulic performance. Background water quality was generally improved by subsurface movement through the absorption fields. A bacterial tracer was found in shallow (45.7 cm) and deep (213.4 cm) sampling wells within 24 h in the two subsystems (but in low numbers) over both summer and winter sampling periods. A viral tracer was detected within 48 h in both shallow and deep wells, but only in subsystem 2 in the winter. In evaluating denitrification potential, the addition of glucose to soil core samples did increase quantitatively, although not significantly, nitrous oxide production in each subsystem, at each depth, during each season. Overall, the performance of both subsystems was very similar. The soil infiltrator functioned very well, as designed for the site and soil limitations. It appears to be a potential alternative OSWTDS for use in problem soils. / Master of Science

When well water becomes contaminated to the extent that is does not meet EPA drinking water quality standards, it is considered unsafe for consumption. Nitrate and total coliform bacteria are both health contaminants and are both regulated in public water systems. A nitrate concentration of 10 mg/L or higher is considered unsafe, as is the presence of total coliform bacteria. Well degradation, inadequate well construction, and aquifer contamination can all result in contamination of well water. Factors such as well type, well age, well depth, treatment devices, population density, household plumbing pipe materials, and nearby pollution sources may affect household water quality. The specific objective of this study was to determine which factors influence nitrate levels and total coliform presence/absence of household well water. If possible, these influencing factors would be used to develop a relationship that would allow household residents to predict the nitrate level and total coliform presence/absence of their well water. As a result, a means of predicting the contamination risk to a specific well water supply under a given set of conditions, in addition to increasing awareness, could provide the homeowner with a rationale for further investigating the possibility of contamination. Existing data from the Virginia Cooperative Extension Household Water Quality Testing and Information Program were assembled for analyses in this project. The data consisted of 9,697 private household water supplies sampled from 1989-1999 in 65 Virginia counties. Initially, the entire state of Virginia was analyzed, followed by the five physiographic provinces of Virginia: the Blue Ridge, Coastal Plain, Cumberland Plateau, Ridge & Valley, and Piedmont. Ultimately, Louisa County was investigated to evaluate the possibility that better models could be developed using smaller land areas and, consequently, less geological variation. Least squares regression, both parametrically and non-parametrically, was used to determine the influence of various factors on nitrate levels. Similarly, logistic regression was used to determine the influence of the same parameters on nitrate categories, presence/absence of total coliform, and risk categories. Using stepwise model-building techniques, based primarily on statistical significance (p-values) and partial coefficient of determination (partial-R2), first and second-order linear models were evaluated. The best-fitting model only explained 58.5% of the variation in nitrate and none of the models fit well enough to be used for prediction purposes. However, the models did identify which factors were, in a statistical sense, significantly related to nitrate levels and total coliform presence/absence and quantified the strength of these relationships in terms of the percent of variation explained. / Master of Science

Egg yolk contamination of egg whites continues to be a serious problem in the egg industry. The ability of egg whites to form stable and voluminous foams is greatly inhibited by accidental yolk contamination, even at extremely small levels. Experiments were conducted to determine if lipase can regenerate the functional properties of yolk-contaminated egg whites. Treatments included control, 0.2% yolk-contamination, and 0.2% yolk-contamination that was treated with lipase and colipase and heated at 37°C for 1 hour. Lipase from Mucor meihei and colipase from porcine pancreas were added to yolk-contaminated egg white samples to target and hydrolyze the triglycerides from egg yolk. Enzymatic hydrolysis was confirmed using thin-layer chromatography. Treatment of yolk-contaminated samples with lipase, colipase and heat yielded a drastic improvement in a number of the functional properties, including the final foam volume, foam capacity, and foaming power. These functional properties showed complete restoration to control levels. However, foam stability and foam drainage levels were not statistically different from yolk-contaminated samples that had not been enzymatically treated. Enzyme treated yolk-contaminated egg whites were also tested in an angel food cake system. There were three treatments, including an uncontaminated control, a contaminated control, and a lipase and colipase treated yolk-contaminated sample. Comparison between treatments was performed by volume analysis. The enzyme treated yolk-contaminated egg whites performed similarly to uncontaminated control angel food cakes. / Master of Science

No / We have investigated the susceptibility of degraded human hair shaft samples to contamination by exogenous sources of DNA, including blood, saliva, skin cells, and purified DNA. The results indicate that on the whole hair shafts are either largely resistant to penetration by contaminant DNA, or extremely easy to successfully decontaminate. This pertains to samples that are both morphologically and biochemically degraded. We suggest that this resistance to the incorporation of contaminant DNA relates to the hydrophobic and impermeable nature of the keratin structures forming the hair shaft. Therefore, hair samples represent an important and underestimated source of DNA in both forensic and ancient DNA studies.

Le Site Pilote de Tchernobyl (CPS) est voué à l’étude de la migration des radionucléides à partir de l’une des tranchées creusée pour enfouir la matière contaminée à la suite de l'accident de Tchernobyl (1986). L’objectif de cette thèse est d’étudier les processus de migration des éléments dans la nappe phréatique.D’abord, l’extension maximale du panache de contamination est étudiée à l’aide du traceur conservatif 36Cl. Dans la nappe, les rapports 36Cl/Cl sont 1 à 4 ordres de grandeur supérieurs au rapport naturel théorique (particulièrement en aval de la tranchée), signifiant une importante contamination de la nappe par le 36Cl.Ensuite, un modèle conceptuel des processus géochimiques est proposé à partir de l’étude des variations en [Cl-], [HCO3-], [SO42-], [NO3-], [Na+], [Ca2+], [K+] [Mg2+], [Si], [Fe2+], [Mn2+] et des rapports δ18O et δ2H. Certains éléments sont très influencés par la présence de la tranchée mais des processus naturels peuvent aussi avoir une influence sur géochimie des eaux (eau-roche ou de drainage).Puis, les rapports isotopiques 238U/235U, 86Sr/88Sr et 87Sr/86Sr sont mesurés pour étudier la migration d’U et du Sr. La dissolution des particules de combustible enfouies dans la tranchée et le lessivage des radionucléides qui leur sont associés pourraient avoir un impact significatif sur les rapports isotopiques dans la nappe. Une augmentation des concentrations en [238U] est observée en aval de la tranchée mais les rapports 238U/235U mesurés sont naturels. La procédure d'analyse des rapports 86Sr/88Sr et 87Sr/86Sr ne permet pas d’observer un changement de ces rapports dans la nappe mais une diminution du rapport est observée en profondeur. / The Chernobyl Pilot Site (CPS) was set up to study the migration of radionuclides from one of the trenches dug in situ to bury materials contaminated after Chernobyl accident. The aim of this study is to investigate migration processes in groundwater. At first, the maximal extent of the contaminant plume is investigated based on the study of conservative tracer 36Cl. High contamination of groundwater by 36Cl is shown, with 36Cl/Cl ratios 1 to 4 orders of magnitude higher than the theoretical natural ratio (specifically downgradient of the trench). Then, a conceptual model of the main geochemical processes in groundwater is proposed based on the study of variantions in [Cl-], [HCO3-], [SO42-], [NO3-], [Na+], [Ca2+], [K+] [Mg2+], [Si]), [Fe2+], [Mn2+], and δ18O and δ2H. Some element concentrations are mainly governed by migrations from the trench. However, natural geochemical processes are also assessed to have an influence on groundwater geochemistry (water-rock interaction, leakage). Next, uranium and strontium migrations are investigated based on measurements of 238U/235U, 86Sr/88Sr, 87Sr/86Sr ratios. Indeed, dissolution fuel particles buried in the trench and the release of associated radionuclides is supposed to have a significant impact on those ratios in groundwater. However, in spite of an increase of [238U] concentrations downgradient of the trench, measured 238U/235U ratios in groundwater are in the natural range. Analytical procedure for 86Sr/88Sr and 87Sr/86Sr ratio measurement does not allow observing some trend downgradient of the trench; however, 87Sr/86Sr ratios clearly decrease with the depth.

La perfusion intraveineuse occupe une large place dans les services de soins cliniques. Les patients reçoivent de nombreux médicaments simultanément dans la même voie centrale, où des problèmes de compatibilité entre les médicaments peuvent survenir. La maitrise de ces incompatibilités médicamenteuses, génératrices de particules, représente donc un enjeu majeur dans la prise en charge des patients polymédiqués.La première partie de ce travail est une analyse de la littérature portant sur les incompatibilités médicamenteuses et leurs principales conséquences sur le plan clinique. A ce titre, un chapitre est dédié à l’ensemble des moyens de prévention de ces problèmes, parmi lesquels l’usage de filtres en ligne de perfusion ou de dispositifs de perfusion multi-lumières.La première partie de nos travaux expérimentaux est consacrée à l’évaluation de la filtration terminale comme stratégie de prévention de l’administration de particules aux patients. Dans ce contexte, nos travaux ont porté sur le noircissement des filtres en ligne observé dans un service de réanimation néonatale. L’objectif était de définir la nature de l’incompatibilité en cause et de s’assurer, dans un second temps, de l’efficacité des filtres malgré les phénomènes de noircissement. Les filtres ont été examinés par microscopie électronique et comptage particulaire. Un aminogramme de la nutrition parentérale a également été réalisé. Une interaction spécifique a été mise en évidence entre un acide aminé (la cystéine) et un oligoélément (le cuivre) dans les poches. De plus, le maintien de la fonction des filtres en ligne a été démontré.La seconde partie de nos travaux est axée sur l’évaluation de l’intérêt d’un dispositif médical multi-lumières innovant dans la prévention des incompatibilités médicamenteuses. Le premier travail mené dans cette thématique a montré in vitro son intérêt à prévenir la survenue d’incompatibilités physiques entre plusieurs associations médicamenteuses, allant de deux à six médicaments administrés simultanément. Nos résultats indiquent que la conception de ces nouveaux dispositifs de perfusion et notamment leur géométrie interne permet de minimiser le temps de contact entre les produits, et ainsi d’améliorer la compatibilité entre les produits, au même titre que le type de solution d’hydratation. Le second travail consistait à poursuivre l’évaluation de ces dispositifs de perfusion multi-lumières en reproduisant un protocole de perfusion utilisé habituellement en hématologie pédiatrique et associant plusieurs médicaments incompatibles à l’origine de précipité. Un comptage particulaire réalisé de manière dynamique a permis de montrer que l’emploi de ces dispositifs permettait de réduire significativement la charge particulaire administrée aux patients, en comparaison avec les dispositifs standard de perfusion (rampes de robinets).Les résultats de l’ensemble de nos travaux sont prometteurs pour l’amélioration de la prise en charge des patients. Ils doivent être maintenant confirmés au travers d’une étude clinique. / Intravenous infusions are extensively used in clinical wards. Patients simultaneously receive many drugs through a limited number of venous accesses, thus increasing the risk of physical drug incompatibilities. Preventing incompatibility is therefore important for the safe administration of injectable drugs of polymedicated patients.The first part of this work consisted in analysing published literature on drug incompatibilities and their clinical consequences. This chapter includes a review of tools preventing drug incompatibilities, which include in-line filtration or the use of multi-lumen infusion sets.The first part of our experimental work is dedicated to the evaluation of terminal in-line filtration for preventing the injection of drug particles to patients. In this context, our research has focused on the blackening of in-line filters, which have been observed during the infusion of binary parenteral nutrition (BPN) delivered in a neonatal intensive care unit. The purposes of our study were, first, to examine the elemental content of precipitates isolated from infused BPN bags and so determine the main physicochemical interactions occurring in them and, second, to evaluate the blackening effect of in-line filters on filtration capacity. Filter membranes were examined by scanning electron microscopy and energy dispersion spectroscopy. Amino acid (AA) profiles were obtained from BPN mixtures to determine the concentrations of each AA. A specific interaction was identify between cysteine and copper in our BPN. Despite the gradual blackening of in-line filters during BPN bag infusion, the filter membranes continued to filter solutions efficiently and safely.The second part of our work focused on the assessment of the impact of new multilumen infusion access devices on the occurrence of known drug incompatibility.The first study used a well-documented incompatible combination of two to six drugs and three different carrier fluids. The multilumen infusion access device was able to prevent the occurrence of drug incompatibilities in nearly half of the drug combinations tested. This study confirmed that the characteristics of an infusion device have an impact on drug physical incompatibilities. The main hypothesis is those fluid dynamics differ according to infusion device and accesses, which modify the contact time between drugs and the infusion vehicle.The second in vitro study focused on a pediatric multidrug protocol for patients diagnosed with lymphoblastic leukemia and receiving allogeneic transplantation. A dynamic particle count test was used over 24 hours to evaluate the overall particulate contamination. The use of a multi-lumen infusion set reduces significantly overall particulate contamination compared to the standard infusion set.These results pave the way to performing a randomized controlled clinical trial assessing the multilumen infusion access device.