Geology of the Sand Creek porphyry molybdenum prospect /

The Sand Creek Prospect is located within the eastern exposed margin of the Coast Plutonic Complex. The occurrence is a plug and dyke porphyry molybdenum deposit. The rock types, listed in decreasing age: 1) metamorphlc schists and gneisses; 2) diorite suite rocks - diorite, quartz diorite, tonalite; 3) rocks of andesitic composition; 4) granodiorites, coarse porphyritic granodiorite, quartzfeldspar porphyry, feldspar porphyry; and 5) lamprophyre. Hydrothermal alteration is known to have resulted from emplacement of the hornblende-feldspar porphyry through to the quartz-feldspar porphyry. Molybdenum mineralization is chiefly associated with the quartz-feldspar porphyry. Ore mineralogy is dominated by pyrite with subordinate molybdenite, chalcopyrite, covelline, sphalerite, galena, scheelite, cassiterite and wolframite. Molybdenite exhibits a textural gradation outward from the quartz-feldspar porphyry. That is, disseminated rosettes and rosettes in quartz veins to fine-grained molybdenite in quartz veins and potassic altered fractures to fine-grained molybdenite paint or 6mears in the peripheral zones. The quartz-feldspar porphyry dykes were emplaced in an inhomogeneous stress field. The trend of dykes, faults and shear zones is 0^1° to 063° and dips between 58° NW and 86* SE. Joint Pole distribution reflects this fault orientation. These late deformatior maxima are probably superimposed upon annuli representing diapiric emplacement of the plutons. A model of emplacement involving two magmatic pulses is given in the following sequence: Diorite pulse (i) dioritequartz diorite, (ii) tonalites; granodiorite pulse (iii) hornblende-fildspar microporphyry, hornblende/biotite porphyry, (iv) coarse grained granodiorite, (v) quartz-feldspar porphyry, (vi) feldspar porphyry, and (vii) lamprophyre. The combination of plutonic and coarse porphyritic textures, extensive propylitic overprinting of potassic alteration assemblages suggests that the. prospect represents the lower reaches of a porphyry system.

Geology of the Gander Group, Gander River Ultramafic Belt and Davidsville Group in the Jonathan's Pond - Weir's Pond Area, northeast Newfoundland /

The study area is situated in NE Newfoundland between Gander Lake and the north coast and on the boundary between the Gander and Botwood tectonostratigraphic zones (Williams et al., 1974). The area is underlain by three NE trending units; the Gander Group, the Gander River Ultramafic Belt (the GRUB) and the Davidsville Group. The easternmost Gander Group consists of a thick, psammitic unit composed predominantly of psammitic schist and a thinner, mixed unit of semipelitic and pelitic schist with minor psammite. The mixed unit may stratigraphically overlie the psammitic unit or be a lateral facies equivalent of the latter. No fossils have been recovered from the Gander Group. The GRUB is a terrain of mafic and ultramafic plutonic rocks with minor pillow lava and plagiogranite. It is interpreted to be a dismembered ophiolite in thrust contact with the Gander Group. The westernmost Davidsville Group consists of a basal conglomerate, believed deposited unconformably upon the GRUB from which it was derived, and an upper unit of greywacke and slate, mostly of turbidite origin, with minor limestone and calcareous sandstone. The limestone, which lies near the base of the unit, contains Upper Llanvirn to Lower Llandeilo fossils. The Gander and Davidsville Groups display distinctly different sedimentological , structural and metamorphic histories. The Gander Group consists of quartz-rich, relatively mature sediment. It has suffered three pre-Llanvirn deformations, of which the main deformation, Dp produced a major, NE-N-facing recumbent anticline in the southern part of the study area. Middle greenschist conditions existed from D^ to D- with growth of metamorphic minerals during each dynamic and static phase. In contrast, the mineralogically immature Davidsville Group sediment contains abundant mafic and ultramafic detritus which is absent from the Gander Group. The Davidsville Group displays the effects of a single penetrative deformation with localized D_ and D_ features, all of which can be shown to postdate D_ in the Gander Group. Rotation of the flat Gander S- into a subvertical orientation near the contact with the GRUB and the Davidsville Group is believed to be a Davidsville D^ feature. Regional metamorphism in the Davidsville Group is lower greenschist with a single growth phase, MS . These sedimentological, structural and metamorphic differences between the Gander and Davidsville Groups persist even where the GRUB is absent and the two units are in contact, indicating that the tectonic histories of the Gander and Davidsville Groups are distinctly different. Structural features in the GRUB, locally the result of multiple deformations, may be the result of Gander and/or Davidsville deformations. Metamorphism is in the greenschist facies. Geochemical analyses of the pillow lava suggest that these rocks were formed in a back-arc basin. Mafic intrusives in the Gander Group appear to be the result of magraatism separate from that producing the pillow lava. The Gander Group is interpreted to be a continental rise prism deposited on the eastern margin of the Late Precambrian-Lower Paleozoic lapetus Ocean. The GRUB, oceanic crust possibly formed in a marginal basin to the west, is believed to have been thrust eastward over the Gander Group, deforming the latter, during the pre-Llanvirnian, possibly Precambrian, Ganderian Orogeny. The Middle Ordovician and younger Davidsville Group was derived from, and deposited unconformably on, this deformed terrain. Deformation of the Davidsville Group occurred during the Middle Devonian Acadian Orogeny.

The sedimentology of the Bloomington fan complex: an element of the Oak Ridges Moraine, Southern Ontario

The Oak Ridges Moraine is a major physiographic feature of south-central Ontario, extending from Rice Lake westward to the Niagara Escarpment. While much previous work has largely postulated a relatively simple the origin of the moraine, recent investigations have concentrated on delineating the discernible glacigenic deposits (or landform architectural elements) which comprise the complex mosaic of the Oak Ridges Moraine. This study investigates the sedimentology of the Bloomington fan complex, one of the oldest elements of the Oak Ridges Moraine. The main sediment body of the Bloomington fan complex was deposited during early stages of the formation of the Oak Ridges Moraine, when the ice subdivided, and formed a confined, interlobate lake basin between the northern and southern lobes. Deposition from several conduits produced a fan complex characterized by multiple, laterally overlapping, fan bodies. It appears that the fans were active sequentially in an eastward direction, until the formation of the Bloomington fan complex was dominated by the largest fan fed by a conduit near the northeastern margin of the deposit. Following deposition of the fan complex, the northern and southern ice margins continued to retreat, opening drainage outlets to the west and causing water levels to drop in the lake basin. Glaciofluvial sediment was deposited at this time, cutting into the underlying fan complex. Re-advancing northern ice then closed westerly outlets, and caused water levels to increase, initiating the re-advance of the southern ice. As the southern ice approached the Bloomington fan, it deposited an ice-marginal sediment complex consisting of glacigenic sediment gravity flows, and glaciolacustrine and glaciofluvial sediments exhibiting north and northwesterly paleocurrents. Continued advance of the southern ice, overriding the fan complex, ii produced large-scale glaciotectonic deformation structures, and deposited the Halton Till. The subaqueous fan depositional model that is postulated for the Bloomington fan complex differs from published models due to the complex facies associations produced by the multiple conduit sources of sediment feeding the fans. The fluctuating northern and southern ice margins, which moved across the study area in opposite directions, controlled the water level in the interlobate basin and caused major changes in depositional environments. The influence of these two lobes also caused deposition from two distinct source directions. Finally, erosion, deposition, and deformation of the deposit with the readvance of the southern ice contributed further to the complexity of the Bloomington fan complex.

The effects of plants(Typha Latifolia)and root-bed medium on the treatment of domestic sewage within a vertical flow constructed wetland /

The effect that plants {Typha latifolia) as well as root-bed medium physical and chemical characteristics have on the treatment of primary treated domestic wastewater within a vertical flow constructed wetland system was investigated. Five sets of cells, with two cells in each set, were used. Each cell was made of concrete and measured 1 .0 m X 1 .0 m and was 1.3 m deep. Four different root-bed media were tested : Queenston Shale, Fonthill Sand, Niagara Shale and a Michigan Sand. Four of the sets contained plants and a single type of root-bed medium. The influence of plants was tested by operating a Queenston Shale set without plants. Due to budget constraints no replicates were constructed. All of the sets were operated independently and identically for twenty-eight months. Twelve months of data are presented here, collected after 16 months of continuous operation. Root-bed medium type did not influence BOD5 removal. All of the sets consistently met Ontario Ministry of Environment (MOE) requirements (<25 mg/L) for BOD5 throughout the year. The 12 month average BOD5 concentration from all sets with plants was below 2.36 mg/L. All of the sets were within MOE discharge requirements (< 25 mg/L) for suspended solids with set effluent concentrations ranging from 1.53 to 14.80 mg/L. The Queenston Shale and Fonthill Sand media removed the most suspended solids while the Niagara Shale set produced suspended solids. The set containing Fonthill Sand was the only series to meet MOE discharge requirements (< Img/L) for total phosphorus year-round with a twelve month mean effluent concentration of 0.23 mg/L. Year-round all of the root-bed media were well below MOE discharge requirements (< 20mg/L in winter and < 10 mg/L in sumnner) for ammonium. The Queenston Shale and Fonthill Sand sets removed the most total nitrogen. Plants had no effect on total nitrogen removal, but did influence how nitrogen was cycled within the system. Plants increased the removal of suspended solids by 14%, BOD5 by 10% and total phosphorus by 22%. Plants also increased the amount of dissolved oxygen that entered the system. During the plant growing season removal of total phosphorus was better in all sets with plants regardless of media type. The sets containing Queenston Shale and Fonthill Sand media achieved the best results and plants in the Queenston Shale set increased treatment efficiency for every parameter except nitrogen. Vertical flow wetland sewage treatment systems can be designed and built to consistently meet MOE discharge requirements year-round for BOD5, suspended solids, total phosphorus and ammonium. This system Is generally superior to the free water systems and sub-surface horizontal flow systems in cold climate situations.

A Study of Nonfans and Fans of the National Lacrosse League's Edmonton Rush

The National Lacrosse League (NLL) is floundering. In an attempt to understand why NLL fans attend games and other sport fans do not, the NLL’s Edmonton Rush were studied. To best address the NLL’s attendance woes, two primary research questions were developed: 1) Why do fans of the Oilers and Oil Kings choose not to attend Edmonton Rush games? 2) Why do fans of the Edmonton Rush attend games? To answer these questions an online focus group along with a document analysis of Rush media, and a telephone interview were used to collect data. The data collection methods mentioned above assisted in answering the primary and secondary research questions, which allowed three major themes along with sub-themes to inductively emerge. The nonfans of the Rush do not attend Rush games because of the connection they have with hockey and the disconnection they have with lacrosse, some are simply not interested or were not entertained, as well as the lack of exposure the Rush receive. The Rush fan participants attend Rush games because of Edmonton community pride, the entertainment value they get out of attending a game, it is a great alternative new sport experience and it either is a substitute or a compliment to hockey. Both the nonfan and fan participants of this study believe that different marketing approaches can be utilized in order to attract nonfans to attend games.

Immediate and enduring effects of corticosterone administration during adolescence and adulthood on anxiety and depressive behavior in male rats

Previous research has shown that the stress hormone corticosterone can increase depressive and anxiety-like behavior in rats as well as dampen the HPA response to a novel stressor (Kalynchuk et aI., 2004; Johnson et aI., 2006). Several studies have also shown that adolescence is a period of increased sensitivity to the negative effects of stressors (reviewed in McCormick et aI., 2010), which are often the result of exposure to corticosterone, and yet there is no research to date examining the effects of corticosterone administration during adolescence. The purpose of these experiments is to determine both the immediate and enduring effects of prolonged exposure to corticosterone in adolescence and adulthood on anxiety-like behavior, depressive behavior, and the HPA response. In Experiment 1 adolescent and adult rats were administered an injection of 40 mg/kg of corticosterone or vehicle daily for 16 days. Ha l f of the rats were then tested on the elevated plus maze (EPM) one day after their last injection, and the following day were tested on the forced swim test (FST). After the FST, which is a stressor, blood samples were collected at three time points, and the plasma concentrations of corticosterone were determined using a radioimmunoassay. The remaining rats were left undisturbed for three weeks, and then underwent the same testing as the first group. Corticosterone treatment had little effect on anxiety-like and depressive behavior, but it did alter the HPA response to the FST. In those rats tested soon after the period of injections, corticosterone dampened the HPA response as compared to vehicle treated rats in both adolescent and adult treated rats. For the adolescent treated rats that were tested several weeks later, corticosterone treatment increased HPA response as compared to the vehicle treated rats, but the same was not true for the adult treated rats. I t was hypothesized that the lack of behavioral effects of the corticosterone treatment may be the result of the vehicle injections inducing a stress response and thereby both groups would have similarly altered behavior. In Experiment 2 rats were administered corticosterone dissolved in their drinking water with 2.5% ethanol, or jus t the 2.5% ethanol or plain water, to determine the effects of corticosterone treatment without a stressor present. The regular drinking water was replaced with treated water for 16 days either during adulthood or adolescence, and as before, rats were either tested in the FST one day after the water was removed or three weeks later. Again there was no effect of treatment on depressive behavior. Similar to what was observed in Experiment 1, corticosterone treatment dampened the HPA response to a stressor for the rats tested soon after the treatment period. However, in Experiment 2 there was no effect of treatment on HPA response in those rats tested several weeks after they were treated. These results indicate that corticosterone can have a lasting effect on the HPA when administered in adolescence by injections but not in drinking water, which is likely because of the different schedules of exposure and rates of absorption between the two administration methods.

Subliminal Exposure to Empathy Primes: A New Method to Reduce Intergroup Bias?

An abundant literature has demonstrated the benefits of empathy for intergroup relations (e.g., Batson, Chang, Orr, & Rowland, 2002). In addition, empathy has been identified as the mechanism by which various successful prejudice-reduction procedures impact attitudes and behaviour (e.g., Costello & Hodson, 2010). However, standard explicit techniques used in empathy-prejudice research have a number of potential limitations (e.g., resistance; McGregor, 1993). The present project explored an alternative technique, subliminally priming (i.e., outside of awareness) empathy-relevant terms (Study 1), or empathy itself (Study 2). Study 1 compared the effects of exposure to subliminal empathy-relevant primes (e.g., compassion) versus no priming and priming the opposite of empathy (e.g., indifference) on prejudice (i.e., negative attitudes), discrimination (i.e., resource allocation), and helping behaviour (i.e., willingness to empower, directly assist, or expect group change) towards immigrants. Relative to priming the opposite of empathy, participants exposed to primes of empathy-relevant constructs expressed less prejudice and were more willingness to empower immigrants. In addition, the effects were not moderated by individual differences in prejudice-relevant variables (i.e., Disgust Sensitivity, Intergroup Disgust-Sensitivity, Intergroup Anxiety, Social Dominance Orientation, Right-wing Authoritarianism). Study 2 considered a different target category (i.e., Blacks) and attempted to strengthen the effects found by comparing the impact of subliminal empathy primes (relative to no prime or subliminal primes of empathy paired with Blacks) on explicit prejudice towards marginalized groups and Blacks, willingness to help marginalized groups and Blacks, as well as implicit prejudice towards Blacks. In addition, Study 2 considered potential mechanisms for the predicted effects; specifically, general empathy, affective empathy towards Blacks, cognitive empathy towards Blacks, positive mood, and negative mood. Unfortunately, using subliminal empathy primes “backfired”, such that exposure to subliminal empathy primes (relative to no prime) heightened prejudice towards marginalized groups and Blacks, and led to stronger expectations that marginalized groups and Blacks improve their own situation. However, exposure to subliminal primes pairing empathy with Blacks (relative to subliminal empathy primes alone) resulted in less prejudice towards marginalized groups and more willingness to directly assist Blacks, as expected. Interestingly, exposure to subliminal primes of empathy paired with Blacks (vs. empathy alone) resulted in more pro-White bias on the implicit prejudice measure. Study 2 did not find that the potential mediators measured explained the effects found. Overall, the results of the present project do not provide strong support for the use of subliminal empathy primes for improving intergroup relations. In fact, the results of Study 2 suggest that the use of subliminal empathy primes may even backfire. The implications for intergroup research on empathy and priming procedures generally are discussed.

Glacial stratigraphy and micromorphology of the Pine Point Pb-­‐Zn mining district, Northwest Territories

This investigation aims to gain a better understanding of the glacial history of the Pine Point Mining district, Northwest Territories, by examining the sedimentological properties of the glacial sediments including, geochemical analysis, heavy mineral concentrate analysis, clast macro-­‐fabrics, pebble lithologies, and micromorphological investigation. Four till units were identified, and three were associated with identified erosional bedrock features and streamlined landforms in the area, indicating a minimum of three ice flow directions. Sedimentological properties suggest that these units were all Type-­B tectomict/mélange till, emplaced as part of a soft subglacial deformable bed. The lack of ice-­‐marginal advance and retreat sequences within the studied till, suggests the Middle Wisconsinan Laurentide Ice margin was likely north and west of the Pine Point area, as opposed to along the margin of the Canadian Shield and Western Sedimentary Basin where it has been suggested to have existed.

Isoflavone exposure throughout suckling results in improved adult bone health in mice

Exposure to isoflavones (ISO), abundant in soy protein infant formula, for the first 5 days of life results in higher bone mineral density (BMD),greater trabecular connectivity and higher fracture load of lumbar vertebrae (LV) at adulthood. The effect of lengthening the duration of exposure to ISO on bone development has not been studied. This study determined if providing ISO for the first 21 days of life, which more closely mimics the duration that infants are fed soy protein formula, results in higher BMD, improved bone structure and greater strength in femurs and LV than a 5-day protocol. Female CD-1 mice were randomized to subcutaneous injections of ISO (7 Q1 mg kg/body weight/day) or corn oil from postnatal day 1 to 21. BMD, structure and strength were measured at the femur and LV at 4 months of age, representing young Q2 adulthood. At the LV, exposure to ISO resulted in higher (P,0.05) BMD, trabecular connectivity and fracture load compared with control (CON). Exposure to ISO also resulted in higher (P,0.05) whole femur BMD, higher (P,0.05) bone volume/total volume and Q3 lower (P,0.05) trabecular separation at the femur neck, as well as greater (P,0.05) fracture load at femur midpoint and femur neck compared with the CON group. Exposure to ISO throughout suckling has favorable effects on LV outcomes, and, unlike previous studies using 5-day exposure to ISO, femur outcomes are also improved. Duration of exposure should be considered when using the CD-1 mouse to model the effect of early life exposure of infants to ISO.

Lung cancer risk associated with occupational exposure to nickel, chromium VI, and cadmium in two population-based case-control studies in Montreal.

Cancer du poumon associé à l’exposition au nickel, au chrome VI et au cadmium dans le milieu de travail utilisant deux études populationnelles cas-témoins à Montréal. Au début des années 1990, le nickel, le chrome VI et le cadmium ont été classés en tant qu’agents cancérigènes de classe 1 par le CIRC (Centre International de Recherche sur le Cancer). Cependant, les résultats des études ayant permis la classification de ces métaux n’ont pas toujours été reproduits, et d’importantes questions demeurent quant aux effets de ces métaux à de faibles niveaux d’exposition. Un plus grand nombre de recherches empiriques est donc nécessaire afin de réaffirmer la cancérogénicité de ces agents, et d’identifier les circonstances dans lesquelles ils peuvent être néfastes. L'objectif de cette étude était d'explorer la relation entre l’exposition à un des métaux (soit le nickel, le chrome VI, ou le cadmium) et les risques subséquents de développer un cancer du poumon chez des travailleurs provenant de différents milieux de travail qui sont exposés à ces métaux à de différents degrés. Deux études cas-témoins de base populationnelle menées à Montréal ont fourni les données nécessaires pour examiner la cancérogénicité de ces métaux. La première étude était menée entre 1979 et 1986 chez des hommes âgés de 35 à 70 ans ayant un cancer dans l’un de 19 sites anatomiques de cancer sélectionnés. La seconde étude était menée entre 1996 et 2001 chez des hommes et des femmes âgés de 35 à 75 ans, avec un diagnostic de tumeur maligne au poumon. Dans ces deux études, les cas ont été recensés dans tous les hôpitaux de l'île de Montréal, tandis que les contrôles populationnels appariés par âge et stratifiés par sexe, ont été sélectionnés des listes électorales. Une entrevue avec chaque sujet a permis d'obtenir un historique d'emploi détaillé ainsi que des informations précises sur les facteurs de risques socio-économiques et personnels. Les descriptions de poste ont été évaluées par une équipe d'experts chimistes et hygiénistes afin de déterminer si le sujet a été exposé à chaque agent, et pour mesurer à la fois la concentration et la durée de chaque exposition, ainsi que l’exposition cumulative tout au long de la vie de chaque participant. Pour déterminer si une exposition à l’un des trois métaux en cause était associée à une augmentation de l'incidence du cancer du poumon, des données ont été analysées par régression logistique : des ajustements ont été effectués pour des facteurs de confusion pertinents incluant un historique détaillé du tabagisme. Des mesures catégoriques d'exposition cumulée ont été également analysées, ainsi que la modification des effets par le tabagisme. Les deux études ont été analysées séparément, puis par la suite combinées afin d'augmenter la puissance statistique. Les niveaux d'exposition mesurés dans cette population ne semblaient pas poser un excès de risque de cancer du poumon pour les travailleurs exposés au chrome VI. Cependant, ceux qui ont été exposés au nickel ont subi une augmentation significative du risque, et ce, quel que soit leur niveau d'exposition. Le risque de développer un cancer du poumon suite à une exposition au cadmium était élevé, mais pas de manière significative. Pour chacun des trois métaux, le risque de cancer du poumon était très élevé parmi les non-fumeurs, mais pas parmi les fumeurs. L’effet combiné du tabagisme et de l’exposition aux métaux était compatible avec un excès de risque additif. Cependant, les intervalles de confiance dans cette étude tendaient à être larges, et une faiblesse de puissance statistique peut limiter l’interprétation de certains résultats. Cette étude est unique dans la mesure où elle a fourni des preuves empiriques sur les risques de développer le cancer du poumon liés aux faibles niveaux d’exposition au nickel, au chrome VI, ou au cadmium provenant de divers contextes de travail. Dans la plupart des autres études, la majorité des expositions pertinentes n’ont pas été bien contrôlées. À l'inverse, cette étude a bénéficié de la collecte et de la disponibilité d'information détaillée concernant le tabagisme et d’autres facteurs de risque. Les résultats de cette étude ont d'importantes conséquences pour la santé publique, tant au niveau de la détermination des risques pour les travailleurs actuellement exposés à ces métaux, qu'au niveau de l’évaluation des risques pour la population en général, elle-même exposée à ces métaux par le biais de la pollution et de la fumée de cigarette. Cette analyse contribuera fort probablement à une réévaluation par le CIRC de la cancérogénicité de ces métaux. L'exploration de la relation entre les risques de cancer du poumon et l'exposition au nickel, au chrome VI et au cadmium est donc opportune et pertinente.

Associations between Exposure to Socio-Cultural Influences in Proximal Environments and Weight Concerns among Urban-Dwelling Women

Résumé Les préoccupations et comportements alimentaires entourant le poids sont omniprésentes chez les jeunes adolescentes et femmes qui habitent dans les cultures occidentales où les formes corporelles sont orientées vers un idéal ultra-mince. L’objectif de cette étude est d’examiner si une plus grande exposition aux endroits faisant la promotion de la minceur est associée à des préoccupations pour le poids plus élevées chez les femmes. Cette étude fait partie d’un projet intitulé ¨Social, cultural, and economic disparities and disordered eating: Understanding the contribution of neighbourhood and individual level factors¨ (Gauvin, Steiger, & Brodeur, 2009). Un échantillon de 1288 femmes âgées entre 20 et 40 ans et résidant à Montréal depuis au moins 12 mois ont répondu à un sondage téléphonique. Des régressions logistiques ont comparé les femmes se situant dans le quintile le plus élevé des préoccupations de poids avec les femmes dans les autres quintiles en fonction de leur exposition 15 jours ou plus dans des endroits faisant la promotion de la minceur. De plus, une analyse de sensibilité a vérifié si l’association demeurait significative à d’autres niveaux d’exposition. Les facteurs confondants ont été contrôlés statistiquement. Les résultats démontrent qu’une fréquentation d’au moins 15 jours par mois d’endroits faisant la promotion de la minceur est associée à des préoccupations plus élevées pour le poids. Aussi, fréquenter ces lieux entre 15 et 20 jours/mois est aussi associé à des préoccupations de poids élevées. Des interventions de santé publique pourraient viser la diminution des pressions socioculturelles vers la minceur.

New statistical methods to assess the effect of time-dependent exposures in case-control studies

Contexte. Les études cas-témoins sont très fréquemment utilisées par les épidémiologistes pour évaluer l’impact de certaines expositions sur une maladie particulière. Ces expositions peuvent être représentées par plusieurs variables dépendant du temps, et de nouvelles méthodes sont nécessaires pour estimer de manière précise leurs effets. En effet, la régression logistique qui est la méthode conventionnelle pour analyser les données cas-témoins ne tient pas directement compte des changements de valeurs des covariables au cours du temps. Par opposition, les méthodes d’analyse des données de survie telles que le modèle de Cox à risques instantanés proportionnels peuvent directement incorporer des covariables dépendant du temps représentant les histoires individuelles d’exposition. Cependant, cela nécessite de manipuler les ensembles de sujets à risque avec précaution à cause du sur-échantillonnage des cas, en comparaison avec les témoins, dans les études cas-témoins. Comme montré dans une étude de simulation précédente, la définition optimale des ensembles de sujets à risque pour l’analyse des données cas-témoins reste encore à être élucidée, et à être étudiée dans le cas des variables dépendant du temps. Objectif: L’objectif général est de proposer et d’étudier de nouvelles versions du modèle de Cox pour estimer l’impact d’expositions variant dans le temps dans les études cas-témoins, et de les appliquer à des données réelles cas-témoins sur le cancer du poumon et le tabac. Méthodes. J’ai identifié de nouvelles définitions d’ensemble de sujets à risque, potentiellement optimales (le Weighted Cox model and le Simple weighted Cox model), dans lesquelles différentes pondérations ont été affectées aux cas et aux témoins, afin de refléter les proportions de cas et de non cas dans la population source. Les propriétés des estimateurs des effets d’exposition ont été étudiées par simulation. Différents aspects d’exposition ont été générés (intensité, durée, valeur cumulée d’exposition). Les données cas-témoins générées ont été ensuite analysées avec différentes versions du modèle de Cox, incluant les définitions anciennes et nouvelles des ensembles de sujets à risque, ainsi qu’avec la régression logistique conventionnelle, à des fins de comparaison. Les différents modèles de régression ont ensuite été appliqués sur des données réelles cas-témoins sur le cancer du poumon. Les estimations des effets de différentes variables de tabac, obtenues avec les différentes méthodes, ont été comparées entre elles, et comparées aux résultats des simulations. Résultats. Les résultats des simulations montrent que les estimations des nouveaux modèles de Cox pondérés proposés, surtout celles du Weighted Cox model, sont bien moins biaisées que les estimations des modèles de Cox existants qui incluent ou excluent simplement les futurs cas de chaque ensemble de sujets à risque. De plus, les estimations du Weighted Cox model étaient légèrement, mais systématiquement, moins biaisées que celles de la régression logistique. L’application aux données réelles montre de plus grandes différences entre les estimations de la régression logistique et des modèles de Cox pondérés, pour quelques variables de tabac dépendant du temps. Conclusions. Les résultats suggèrent que le nouveau modèle de Cox pondéré propose pourrait être une alternative intéressante au modèle de régression logistique, pour estimer les effets d’expositions dépendant du temps dans les études cas-témoins

Study of baleen whales’ ecology and interaction with maritime traffic activities to support management of a complex socio-ecological system

Thesis written in co-mentorship with Robert Michaud.

The influence of environmental contaminants on time to pregnancy

Cette thèse porte sur l’évaluation de l’impact de certains composés environnementaux sur la fécondité féminine, tel que mesuré par le délai de conception (« time to pregnancy » en anglais, ou TTP). Cette recherche a été réalisée dans le cadre de l’Étude mère-enfant sur les composés chimiques de l’environnement (MIREC), une cohorte de grossesse de 2001 femmes recrutées durant le premier trimestre dans dix villes canadiennes de 2008 à 2011. Les données des questionnaires et les échantillons biologiques ont servi à évaluer l’effet de deux groupes de composés : les persistants [composés perfluorés – perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA) et perfluorohexane sulfonate (PFHxS)] et les non persistants (bisphénol A, triclosan et phtalates). Cette thèse comprend également une analyse du potentiel du ratio index-annulaire (2D:4D) comme mesure de sensibilité endocrinienne. À ce jour, des mesures anthropométriques ont été collectées sur environ 800 mères-enfants dans le cadre de l’Étude mère-enfant sur les composés chimiques de l’environnement : biomonitoring et neurodéveloppement à la petite enfance (MIREC CD Plus), un suivi de la cohorte MIREC portant sur la croissance et le développement des enfants jusqu’à 5 ans. Sur l’ensemble, les résultats de cette thèse permettent d’étoffer les preuves concernant les effets adverses potentiels de plusieurs contaminants environnementaux sur la fécondité féminine, telle que mesurée par le TTP. Dans le premier article, nous avons montré une association entre les PFOA et les PFHxS et une baisse de fécondité, ce que d’autres recherches avaient déjà révélé. Dans le deuxième article, nous avons évalué l’effet du triclosan sur le TTP, ce qui n’avait jamais été examiné, pour montrer un délai plus élevé chez les femmes du quartile supérieur d’exposition. De plus, nos résultats sont en accord avec ceux de la seule étude ayant évalué l’effet du Bisphénol A sur la fécondité féminine, qui n’avait pas détecté d’effet. Finalement, nos données semblent indiquer une association entre l’exposition des femmes aux phtalates et un TTP plus court, mais ces résultats ne sont pas statistiquement significatifs. En ce qui a trait au potentiel du ratio index-annuaire (2D:4D) pour mesurer la sensibilité endocrinienne chez les femmes, nos données ne permettent pas d’établir une association entre ce ratio et le TTP. Pour ce qui est des enfants, nous n’avons pas trouvé d’effet adverse entre le tabagisme de la mère durant la grossesse et leur ratio 2D:4D. Par conséquent, nos données ne semblent pas justifier l’utilisation du ratio 2D:4D pour mesurer la sensibilité endocrinienne en lien avec le potentiel reproducteur (basé sur le TTP) ou l’exposition des enfants au tabac durant le premier trimestre de grossesse.

The costs of alcohol, illegal drugs, and tobacco in Canada, 2002.

Objective: The aim of this study was to estimate costs attributable to substance use and misuse in Canada in 2002. Method: Based on information about prevalence of exposure and risk relations for more than 80 disease categories, deaths, years of life lost, and hospitalizations attributable to substance use and misuse were estimated. In addition, substance-attributable fractions for criminal justice expenditures were derived. Indirect costs were estimated using a modified human capital approach. Results: Costs of substance use and misuse totaled almost Can. $40 billion in 2002. The total cost per capita for substance use and misuse was about Can. $1,267: Can. $463 for alcohol, Can. $262 for illegal drugs, and Can. $541 for tobacco. Legal substances accounted for the vast majority of these costs (tobacco: almost 43% of total costs; alcohol: 37%). Indirect costs or productivity losses were the largest cost category (61%), followed by health care (22%) and law enforcement costs (14%). More than 40,000 people died in Canada in 2002 because of substance use and misuse: 37,209 deaths were attributable to tobacco, 4,258 were attributable to alcohol, and 1,695 were attributable to illegal drugs. A total of about 3.8 million hospital days were attributable to substance use and misuse, again mainly to tobacco. Conclusions: Substance use and misuse imposes a considerable economic toll on Canadian society and requires more preventive efforts.