The study objectives were to: (1) assess fetal exposure to oxidative stress by measuring amniotic fluid concentrations of nitric oxide (NO), thiobarbituric acid--reactive substances (TBARS), and ferric reducing antioxidant power (FRAP) and (2) establish whether these concentrations were associated with infant birth weight, gestational age, or oxidative stress-related conditions arising during pregnancy. Frozen amniotic fluid samples were obtained from 654 mothers undergoing amniocentesis for genetic testing during second trimester in Montreal, QC, Canada. Maternal and neonatal characteristics were collected from medical charts and questionnaires and exclusion criteria were applied. ANOVAs and multivariate regression analyses showed that NO, which differed among pre-term, term, and post-term groups, was a positive predictor of gestational age. TBARS were highly correlated with sample storage and were not associated with pregnancy outcome parameters. FRAP positively predicted gender-corrected birth-weight-for-gestational-age. Our study shows that markers of oxidative and nitrative stress in-utero are associated with pregnancy outcomes.

The study objective was to determine whether early 2 nd trimester amniotic fluid (AF) erythropoietin (EPO) was associated with and predictive of (a) development of maternal gestational diabetes (GDM) and (b) the infant outcome parameters of (i) gestational age at birth (GAAB) assessed exclusively among spontaneous vaginal deliveries or (ii) birth weight (measured in grams and percentiles). Enzyme-linked-immunosorbent assay was used to determine the EPO concentration of 170 biobanked AF samples. Student's t-test revealed no difference between GDM and non-GDM subjects. AF EPO was not predictive of GAAB despite being significantly greater among preterm infants compared to post-term infants. In contrast, AF EPO was significantly higher among the smallest infants using both birth weight classification schemes. However, following inclusion of known covariates AF EPO was predictive of gram birth weight only. Early 2nd trimester AF EPO may emerge as a useful biomarker of fetal nutritional status and/or growth.

The objectives were (1) to establish a profile of total fatty acids and cholesterol in amniotic fluid (AF) as well as (2) to determine possible associations between AT fatty acids (micromolar and relative proportion) with gestational age and birth weight. A total of 208 AF samples collected between 12 and 22 weeks of gestation during routine amniocentesis were analyzed using tandem column gas chromatography (GC). Smoking increased AF polyunsaturated fatty acid (PUFAs) levels while developmental stage and storage time decreased AF fatty acid quantities. AF trans fatty acids (TFAs) were negatively associated with both birth outcomes, whereas specific fatty acids including stearic acid (C18:0) and gondoic acid (C20:1n-9) were identified as negative predictors for gestational age and birth weight respectively. This study demonstrated novel relationships between fatty acids and fetal growth and gestational age in early midgestation AF, suggesting a possible role of AF fatty acids in predicting birth outcomes.

Gasoline is a substance commonly encountered in forensic settings. Unfortunately, gasoline is an easily obtainable ignitable liquid that arsonists commonly use to initiate or expedite the spread of an intentionally set fire. Fires claim the lives of many people each year in addition to causing widespread property damage. Many fire scene investigations result in charges of arson, which has the legal connotation of a committed crime. For this reason, extensive analysis and investigation must be undertaken before any suspected arson scene is deemed an actual case of arson. Although ignitable liquids, including gasoline, may be present at the scene of a fire, it does not necessarily mean they were intentionally used as accelerants. An accelerant is a fuel used to initiate a fire. These realities, in addition to several other factors, demonstrate why a rapid, reliable, gasoline analysis method is crucial to forensic applications. In this thesis, direct analysis in real time – mass spectrometry (DART-MS) is evaluated as a potential method that could better identify, distinguish and classify gasoline brands from one another. Techniques such as DART-MS could enable forensic laboratories to better identify questioned gasoline samples. Many ignitable liquids share similar chemical properties, and forensically relevant evidence is often obtained from a crime scene in less than favorable conditions. Fire debris can encompass various materials, including burnt carpet, flooring, items of furniture and clothing, among others. If gasoline was used as an accelerant, it may be present in trace amounts after the termination of the fire. Materials submitted for laboratory analysis may be substrates with compositions that have components similar to those found in some ignitable liquids. These are just a few of the potential obstacles that could be encountered with analyzing fire debris in a forensic setting. Traditionally, gas chromatography – mass spectrometry (GC-MS) methods are utilized for gasoline analysis in the criminal laboratory setting. While traditional GC-MS methods are sensitive and able to classify samples as gasoline, they are time consuming in terms of both sample preparation and analysis. Additionally, they do not generate differential mass spectral data based on the brand of gasoline. Conversely, gasoline analysis in this research, utilizing the DART-MS method, demonstrated that five different brands of gasoline could be distinguished from one another both by visual examination of mass spectra and with methods of chemometric analysis. Advantageously, the DART-MS method, an ambient ionization technique, requires little sample preparation and a rapid sample analysis time, which could drastically increase the throughput of standard sample analysis with further method development. The goals and objectives of this research were to optimize the DART-MS parameters for gasoline analysis, determine if DART-MS analysis could distinguish gasoline by brand, develop chemometric models to appropriately classify gasoline samples, and finally lay groundwork for future studies that could further develop a more efficient and discriminating DART-MS gasoline analysis method for forensic casework. Each brand of gasoline was observed to have a chemical attribute signature (CAS) consisting of not only low-mass ions, but also a variety of high-mass ions not usually observed with gasoline samples analyzed by GC-MS. Although variables including season, storage time, dilution and age of the gasoline were observed to contribute to the resulting mass spectral data, once the mass spectra are better understood, they could offer even more discriminating power between samples than simple analysis of the gasoline brand. In this research, DART-MS parameters were first optimized for gasoline analysis. Subsequently, the five acquired brands of gasoline: Shell, Sunoco, Irving, Cumberland Farms and Gulf, were analyzed both undiluted (or neat) and diluted utilizing the DART-MS analysis method. GC-MS data was generated and analyzed to show comparisons. After analyzing the data generated by both approaches, it was apparent that the DART-MS method could generate CASs based on the gasoline brand and offer a degree of differentiation that traditional GC-MS does not. Additional chemometric analyses utilizing principle component analysis (PCA) and the construction of models with Analyze IQ Lab software verified that the gasoline brands were distinguishable when samples were analyzed with this ambient ionization method. PCA plots of the neat gasoline demonstrated clustering based on brand. Additionally, models constructed from training samples generated from DART-MS analysis of the various brands were able to accurately classify gasoline samples as "yes" or "no" when a test set of gasoline was compared to all five brands. The lowest associated testing error rate for some of these models was 0%. However, additional analysis with greater sample sizes needs to be further carried out to more accurately evaluate this method of gasoline analysis and classification.

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This thesis presents quantitative tools for the metabolomic analysis of amniotic fluid (AF) using vibrational spectroscopy. A total of 300 AF samples were collected for this retrospective cohort study and both Raman and near infrared (NIR) spectra were measured. Spectral data was compressed using a Haar wavelet transform and stage-wise multilinear regression (MLR). Calibration models were calculated for glucose, lactate and uric acid concentrations in AF. Birth weight, gestational diabetes mellitus (GDM) and gestational age were classified with the resulting compressed Raman and NIR spectra, using a genetic algorithm (GA) and a cross-validation approach. Results show that both Raman and NIR spectra of AF were not able to estimate the concentrations of glucose, lactate or uric acid with high precision. However, metabolomic analysis of AF Raman and NIR spectra was capable of estimating the development of GDM, abnormal birth weights as well as gestational ages with sensitivities >75% and specificities >77%. In addition, Raman and NIR metabolomic profiles showed a statistical difference in patients delivering preterm. Of the two spectroscopic analyses studied, NIR spectroscopy of AF has the potential to become a robust and non-invasive diagnostic tool for maternal and fetal health.

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Ce travail porte sur l'étude de propriétés optiques des fluides à échelle micrométrique. A cet effet, nous avons conçu, réalisé et étudié différents types de micro-résonateurs optofluidiques, sous forme de laboratoires sur puce. Notre analyse est fondée sur la modélisation analytique et numérique, ainsi que sur des mesures expérimentales menées sur des micro-cavités optiques; nous utilisons l'une d'entre elles pour des applications de réfractométrie de fluides homogènes et de fluides complexes ainsi que pour la localisation par piégeage optique de microparticules solides. Nous nous sommes d'abord concentrés sur l'étude d'une nouvelle forme de micro-cavité Fabry-Pérot basée sur des miroirs courbes entre lesquels est inséré un tube capillaire permettant la circulation d'une solution liquide. Les résultats expérimentaux ont démontré la capacité de ce dispositif à être utilisé comme réfractomètre avec un seuil de détection de 1,9 × 10-4 RIU pour des liquides homogènes. De plus, pour un liquide contenant des particules solides, la capacité de contrôler la position des microparticules, par des effets de piégeage optique ou de liaison optique, a été démontrée avec succès. Dans un second temps, un résonateur optique est formé simplement à partir d'une goutte de liquide disposée sur une surface super-hydrophobe. La forme quasi-sphérique résultante est propice à des modes de galerie. Il est démontré que, jusqu'à des tailles de gouttelettes millimétriques, la technique de couplage en espace libre est toujours en mesure d'accéder à ces modes à très faible queue évanescente d'interaction, contrairement à ce qu'indiquait jusqu'ici la littérature. De tels résonateurs optofluidiques à gouttelette devraient trouver leur application notamment comme capteur d'environnement de l'air ambiant ou encore comme incubateur de micro-organismes vivants pouvant être suivis par voie optique / This work focuses on the study of optical properties of fluids at the micrometer scale. To this end, we designed, implemented and studied different types of optofluidic micro- resonators in the Lab-on-Chip format. Our analysis is based on analytical and numerical modeling, as well as experimental measurements conducted on optical microcavities; we use one of them for refractometry applications on homogeneous fluids and on complex fluids, as well as for the localization of solid microparticles by optical trapping. We first focused on the study of a new form of Fabry-Perot micro-cavity based on curved mirrors between which a capillary tube is inserted for injecting a fluidic solution. Experimental results demonstrated the ability of this device to be used as a refractometer with a detection limit of 1.9 × 10-4 RIU for homogeneous liquids. Furthermore, for liquid containing solid particles, the ability to control the microparticles position either by optical trapping or optical binding effects has been successfully demonstrated. In a second step, an optical resonator is simply formed from a liquid droplet placed on top of a superhydrophobe surface. The resulting quasi-spherical shape supports resonant whispering gallery modes. It is shown that, up to millimeter size droplets, the proposed technique of free-space coupling of light is still able to access these modes with very low evanescent tail interaction, contrary to what was indicated in the literature so far. Such optofluidic droplet resonators are expected to find their applications for environmental air quality monitoring, as well as for incubator of living micro-organisms that can be monitored optically