<p>An improved understanding of colloid transport in fractured media is required to assess the potential for microorganisms to contaminate groundwater, to develop groundwater management/protection plans, to design remedial action strategies based on the application of microorganisms, and to quantify colloid-facilitated transport of many organic and inorganic contaminants. Although colloid transport has been investigated to an extent in porous media environments, this field is still in its infancy in fractured media environments.</p> <p>Colloid transport in fractured media involves a host of complex and interacting processes, including (among others): advection, hydrodynamic dispersion, attachment and detachment, straining, size/ charge exclusion, and gravitational settling. These processes are, in turn, influenced by the physicochemical properties of fractured media, the geochemical properties of groundwater, hydrodynamics, and the colloid properties. This research program focused on investigating the effects of aperture field variability, specific discharge, and ionic strength on colloid transport in saturated, variable-aperture, single fractures. An extensive literature review was first conducted, and a combination of physical model experiments and numerical simulations were then employed to achieve this goal.</p> <p> Three transparent fracture replicas were fabricated, and the light transmission method was employed to obtain a direct measurement of each of the three aperture fields. A systematic series of hydraulic and tracer tests was conducted on each of the three experimental fractures, and the cubic law, mass balance and frictional loss apertures were calculated. Additionally, the experimental breakthrough curves were fit to the one-dimensional advection-dispersion equation. The results clearly demonstrate that the mass balance aperture is the only appropriate 'equivalent aperture' for describing transport in a single variable-aperture fracture, and that the mass balance aperture is an excellent approximation ofthe arithmetic mean aperture.</p> <p>A 3^3 factorial experimental design was then implemented to numerically investigate the interactive effect of the arithmetic mean (μb), standard deviation (σb), and anisotropic ratio (AR=λ^b x/ λ^b,y where λ^b x and λ^b y is the correlation length of the aperture field along x- and y- direction respectively) of single fracture apertures on dispersion regimes (specifically Taylor dispersion and geometric dispersion) and dispersivity. The simulation results show that: (1) for a fixed hydraulic gradient: (a) the dominant dispersion regime is controlled by μb, and to a lesser degree, σb, and (b) geometric dispersion becomes more dominant as the coefficient of variation (CoV = σb/μb) increases; (2) for a fixed mean aperture, the dispersivity and the spread in dispersivity for varying ARs increase with the CoV; and (3) the AR has a significant effect on dispersivity only when the CoV is large (>0.2).</p> <p> Numerical simulations investigating colloid and solute transport in single parallel-plate fractures, conducted using the Random Walk Particle Tracking (RWPT) method, demonstrated that: 1) There exists a threshold value, δo , of the aspect ratio, δ (δ= 2rc/b, where rc and b represent the colloid radius and fracture aperture respectively), where the average transport velocities of colloids and solutes are similar. When δ> δo , the Taylor Aris assumption is satisfied, and tp (tp = tc/ts, where tc and ts represent colloid and solute retention times respectively) decreases as δ increases, as is well documented in the hydrodynamic chromatography literature. However, when δ < δo , the Taylor-Aris assumption is violated, and tp increases as δ increases. This has never been documented before, and it helps to explain some seemingly contradictory work in the literature. 2) The Taylor dispersion coefficient and its extension by James and Chrysikopoulos (2003) will overestimate the colloid dispersion coefficient significantly when the Taylor-Aris assumption is violated. Additionally, these simulations demonstrated that tp and DL,coll/DL,solute (where DL,coll and DL,solute represent the dispersion coefficients of colloids and solutes respectively) decrease with increasing CoV, and that the anisotropy ratio, AR, only plays a minor role on these two ratios compared to the CoV. These observations have never been documented before to the knowledge of these authors, and have important implications towards the interpretation of colloid transport in both porous and fractured media.</p> <p> A combination of physical experiments, numerical simulations and visualization techniques was employed to investigate the impact of aperture variability, specific discharge, and ionic strength on colloid transport processes. The mean colloid transport velocity and colloid dispersion coefficient were obtained by fitting the analytical solution of the one-dimensional advection-dispersion equation (ADE) to the measured breakthrough curves. Two significant observations were made from the colloid transport experiment images: (1) colloids migrate along preferential pathways, and bypass some aperture regions; and (2) the colloid plume is irregular in shape, and becomes more irregular with increasing specific discharge, indicating non-Fickian transport. It is therefore postulated that the dispersivity cannot be completely determined by the aperture field characteristics alone; it is also a function of specific discharge. The colloid recovery in all fractures was found to increase with increasing specific discharge. For each specific discharge, it was found that the colloid recoveries in F2 and F3 were similar, and were always larger than the recovery in F1. This is consistent with the fact that the arithmetic mean apertures of F2 and F3 were similar (μb,F2= 1.57 mm, /μb,F3= 1.75 mm), and larger than that of F1 (μb,F1 = 0.88 mm). This suggests that it is the transport step (the step in which the colloids are transported from the bulk fluid to the vicinity of the fracture wall), and not the attachment step, that plays the dominant role in the colloid sorption process. It was also found that the mean transport velocity and dispersion coefficient of colloids are larger than those of solutes in F3 (CoV = 0.29), but similar to those of solutes in F1 (CoV = 0.78) and F2 (CoV = 0.71). This confirms the numerical simulation results from this work indicating that tp and DL,coll/DL,solute decrease with increasing CoV. These findings have significant implications on the interpretation of colloid transport data.</p> / Thesis / Doctor of Philosophy (PhD)

Identifying and locating permeable zones in geothermal fields is a critical step in determining reservoir potential and realizing energy production. Despite a general association with active faults, geothermal systems typically display heterogeneously distributed permeability that makes locating successful wells difficult. Faults are associated with complex distributions of secondary fractures, with variable attitude, fracture density, and connectivity – all of which can influence permeability. Simulations of the local stress state due to slip on a detailed model of the fault system at Brady Geothermal Field, NV, supported by models of key idealized fault geometries, are used to test the relationship between both productive wells or hydrothermal features and failed wells with stress states that promote or suppress fracture. These simulations show that hydrothermal features are generally associated with portions of faults best oriented to slip in the stress state measured at Brady. Critically, regions of enhanced coulomb stress (S_c^((max))) and reduced least compressive principal stress (σ3) that promote fractures occur at narrow, extensional relays and at intersections between faults; at Brady such locations correlate with the locations of production wells and hydrothermal surface manifestations. Despite this positive correlation, several of these structures do not host evidence of hydrothermal flow due to a lack of persistence along the dip of the fault necessary to connect to the heat source at depth. In contrast, regions of reduced S_c^((max)) and enhanced σ3 correspond to volumes that lie near the interior of faults, including at bends and at contractional relays. These locations are generally associated with failed wells; however, major production wells occur at a clear bend in a large fault at Brady. This may reflect the origin of the bend as breached relay and warrants further investigation. / Geology

Fractures, one of the most common findings in paleopathology, can reveal information about behaviour and social identity in the past. A new methodology for assessing the healing stages of fractures has recently been proposed, which could allow for additional data to be gathered from the study of fractures. Trauma, post-traumatic time interval, and injury recidivism were studied in five late Roman (c. 3rd – 4th centuries AD) British and Spanish skeletal samples. The aims of this thesis are: 1) record fractures and their healing stage using new post-traumatic time interval estimation methods; 2) determine how trauma profiles vary in the Romano-British and Spanish samples; 3) employ biocultural and life course approaches in the analysis of the results to reveal information about the culture, social identities, and environmental circumstances in the two Roman provinces under study. The remains of 214 adults from two Romano-British and three Romano-Spanish sites were examined for the presence of long bone and rib fractures. Fracture data was analyzed by age, sex, site, bone element, and fracture type to build a profile of trauma at each of the sites. In addition, cases of multiple injury were assessed using new post-traumatic time interval methods in order to discern cases of injury recidivism. A total of 44 individuals were identified as having 89 fractures across all the skeletal samples. Sixteen individuals had multiple fractures, eight of which were determined to have fractures of different ages using methods for determining post-traumatic time interval. Males and females had similar rates of fractures and multiple injuries. Fractures peaked among economically active young and middle-aged adults. A number of differences between the Romano-British and Spanish sample were observed with regards to trauma patterns and fracture prevalence. The results of this research contribute to our understandings of trauma profiles and injury recidivism in Roman populations, and provide the first comprehensive trauma study of a Romano-Spanish skeletal sample. / Thesis / Master of Arts (MA)

Background: Tibial fractures are associated with prolonged recovery. The aim of this study was to identify predictors of long-term physical functioning after tibial shaft fracture. Methods: We used data from the Trial to Re-evaluate Ultrasound in the Treatment of Tibial Fractures (TRUST) to determine, in patients with unilateral, open or closed tibial shaft fracture, the association between baseline factors and physical functioning at 1-year. All fractures were fixed using intramedullary nails. Physical functioning was measured using the 100-point Short Form-36 (SF-36) Physical Component Summary (PCS) score; higher is better; minimally important difference is 2 to 5 points. Results: There were 299 tibial fracture patients with complete data available for analysis. In an adjusted analysis, the factors associated with lower physical functioning at 1-year were: (1) current smokers (mean difference [MD] -2.55, 95% confidence interval [95%CI] -4.63 to -0.46, p=0.017), (2) body mass index >30 kg/m² (MD -2.57, 95% CI -4.86, -0.27, p = 0.029), and (3) patients who were receiving disability benefits or involved in litigation, or planned to be (MD -2.65, 95% CI -4.58 to -0.72, p = 0.007). Patients who were employed at the time of their fracture reported significantly higher physical functioning at 1-year (MD 4.56, 95% CI 2.32 to 6.80, p= <0.001) and those who were allowed to partial or full weight-bear post-operatively (MD 1.98, 95% CI 0.13 to 3.82, p=0.036). Neither age, sex, fracture severity or receipt of physical therapy were associated with long-term physical functioning. Conclusions: Among patients undergoing surgical repair of tibial fractures, partial or full weight-bearing post-operatively and employment at the time of injury predict better long-term functioning, whereas smoking, obesity, and receipt of disability benefits or involvement in litigation (or plans to be) predict worse long-term functioning. / Thesis / Master of Science (MSc)

Hip fractures are serious injuries that are associated with high rates of morbidity and mortality in older adults. While much of the increased risk of hip fracture with age can be explained by age-related decreases in bone mineral density, muscles and motor control are altered by aging as well. Muscles forces in vivo are thought to have a prophylactic effect that can reduce shear and bending in the femur. This is beneficial because bone is stronger in compression than in shear or tension, and shear plays an important role in fatiguing bone. Understanding how aging and muscular loads affect strains in the proximal femur could lead to improvements in clinical screening and preventative measures for hip fracture. Three studies were performed to investigate age-related changes in neuromuscular function during gait and how these changes affect strains in the proximal femur. Study 1 examined age differences in peak lower extremity joint torques during walking with controlled speed and step length. Studies 2 and 3 applied muscle forces estimated during gait to finite element models of the femur. Study 2 examined age differences in femoral strains, and Study 3 examined the sensitivity of strains to individual muscle forces. The results support the idea that older adults walk with reduced contributions from the ankle plantar flexors and increased contributions from the hip extensors. Interactions between age and speed indicate that older adults utilized a different neuromuscular strategy than young adults to vary the speed of their gait. No age differences were found for the largest magnitude strains in the proximal femur. However, young adults were able to apply larger loads to the femur without corresponding increases in femoral strains. Strains in the femoral neck were found to be sensitive to muscle forces, particularly hip abductor forces. Strains in the sub-trochanteric region tended to be larger than those in the femoral neck, and less sensitive to muscle forces. These results increase our understanding of neuromuscular changes that occur with age, and the effects of these changes on the femur. / Ph. D.

Ceci est une étude de cohorte prospective, avec un suivi d’un an, s’intéressant à la trajectoire postopératoire des patients gériatriques admis pour une fracture de la hanche. Un total de 254 patients étaient inclus dans cette cohorte. Cinq groupes de patients avec des trajectoires similaires ont été formés; 1-retour à domicile (n=63), 2-retour à la résidence (n=22), 3-réadaptation avant retour au milieu de vie original (n=36), 4- changement de milieu de vie (n=28) et 5-décès (n=37). Les patients évoluant dans la trajectoire 1 (évolution favorable) étaient plus jeunes. Les patients évoluant dans la trajectoire 5 (évolution défavorable) étaient plus âgés, étaient malnutris selon l’outil Mini Nutritional Assessement (MNA) et présentaient des troubles neurocognitifs selon leurs pointages du Mini-Mental State Examination (MMSE). Un délai chirurgical allongé était associé avec une mortalité à un an plus élevée, mais ces patients présentaient plus de comorbidités selon l’index de comorbidité de Charlson (CCI). Le délai entre le congé du patient et son départ réel de l’hôpital était associé avec le besoin d’un transfert dans un centre de réadaptation. Il y a donc un besoin de milieux intermédiaires pouvant accueillir les patients gériatriques ayant subi une chirurgie pour fracture de la hanche, afin qu’ils puissent quitter l’hôpital. Les efforts pour améliorer les soins aux patients gériatriques avec fracture de la hanche devraient être déployés pour résoudre ces enjeux. / This is a prospective observational cohort study of patients admitted for a hip fracture between 2011 and 2017, with a one-year follow-up. A total of 254 patients were enrolled in this cohort. Most patients evolved in one of the following trajectories at one year; (1) 30% went back at home (2) 11% went back to their senior residence (3) 16% needed readaptation (4) 13% were discharged to a different location than prior to admission (5) 18% were deceased at one year. Patients evolving in trajectory 1 (favorable outcome) were younger. Patients evolving in trajectory 5 (poor outcome) were older, had lower Mini Nutritional Assessment (MNA) scores and had lower Mini-Mental State Examination scores (MMSE). Longer surgical delay was associated with higher mortality and comorbidities. The delay between discharge from the attending staff and real departure from the hospital was associated with the need for a readaptation. There is a need for intermediate residences such as readaptation centers to facilitate discharge from the hospital. Efforts to improve the postoperative care for elderly patients with a hip fracture should focus on those issues.

Intraplate tectonics is generally not well documented and understood, despite its significance for seismic hazards in areas such as southeastern Canada. Neotectonics is even less well understood in these regions. This study focuses on providing an in-depth analysis of potential neotectonic pop-up structures in southern Ontario, Canada, leading to a comprehensive definition of what pop-up structures are, to constrain the processes involved in neotectonism, and to determine the extent to which neotectonism impacts the region. Previous literature has hypothesized that neotectonic structures have a likely potential to be linked to reactivated structures within the Precambrian Basement rocks of the Canadian Shield. In addition to documenting new potential neotectonic structures, this work provides a brief overview of tectonics in southern Ontario, and how previously measured lineaments in the Precambrian Basement may align with observable, potentially neotectonic surface structures. Three locations in southern Ontario were documented using a combination of ground and drone-based structural analysis: 1) Fletcher Creek Ecological Preserve, 2) Wainfleet Wetlands Conservation Area, and 3) multiple sites on Manitoulin Island. These sites were chosen where previous studies had documented neotectonic activity, and/or where initial geomorphic analyses indicated the possibility of a pop-up structure. All sites are located within the Silurian to Devonian cover rocks of the Niagara Escarpment. Fracture patterns at each site were analyzed using ground-based measurements using FieldClino and/or drone-based photogrammetry (DJI Phantom 4 V2 and Phantom 4 Pro acquisition followed by analysis in Pix4D and Drone2Map), where applicable. Where access permitted, ground-based measurements iv were obtained on structures, in addition to RTK-DGPS (Real Time Kinematic Differential Global Positioning System) profiles over potential pop-up structures. Analysis revealed that pop-up structures exhibit a distinct geomorphic expression, manifesting as a near-linear elevated ridge, where stress relief features have variable geomorphic expressions, such as domes. In southern Ontario, the presence of these pop-ups and stress relief features demonstrates that the region is tectonically active, despite often being characterized as a stable continental interior. This study adds to a growing body of work documenting neotectonics in southern Ontario, with several stress-related structures documented for the first time in this study, showing their prevalence over a wide area. The results of this study were used to create an updated tectonic hazard map of Ontario. / Thesis / Master of Science (MSc)

Objectif : Établir si des impacts sur la qualité de vie des aînés peuvent être identifiés, secondairement à une fracture mineure incidente, selon leur degré de fragilité au moment de leur évaluation dans les urgences. Méthodes : Cette étude s'inscrit dans le programme du Canadian Emergency Team Initiative (2010-2016). Les éléments de santé physique reliés à la qualité de vie ont été mesurés 3 et 6 mois après la fracture par le « Short Form 12-item Health survey » (SF-12). L'indice du « Canadian Study of Health and Aging - Clinical Frailty Scale » fut utilisé pour qualifier le statut de fragilité des personnes selon qu'elles soient Robustes, Pré-Fragiles ou Fragiles au moment de la visite à l'urgence pour le traitement de leur fracture. Les analyses principales portent sur la comparaison des scores moyens aux composantes physiques du SF-12, en fonction du statut fragile. Résultats : Cette sous-cohorte d'aînés de 345 participants dont 263 femmes, présentait un âge moyen de 76,2 ± 7,4 ans. Au total 56% des sujets étaient Robustes, 33% Pré-Fragiles et 11% étaient Fragiles. Plus de 70% des fractures subies étaient aux membres inférieurs ou supérieurs, et étaient survenues lors de chutes (88%). L'ensemble des analyses révèlent des associations statistiquement significatives (p ≤ 0,005) entre l'augmentation du niveau de fragilité et la diminution de tous les scores ajustés au SF-12 (composante physique globale, fonctionnement physique, capacité d'exercer ses rôles de nature physique), et ce à 3 ou 6 mois post-fracture. Conclusion : Nos résultats suggèrent que l'évaluation systématique des aînés, quant à leur degré de fragilité contribuerait ultimement à leur offrir une prise en charge spécifique, incluant traitement et suivi, mieux adaptée à leurs besoins.

Yes / The suspected scaphoid fracture remains a diagnostic conundrum with over-treatment a common risk-averse strategy. Cross-sectional imaging remains the gold standard with MRI recommended but CT used by some because of easier access or limited MRI availability. The aim of this feasibility study was to evaluate whether cone beam computed tomography (CBCT) could support early diagnosis, or exclusion, of scaphoid fractures. Patients with a suspected scaphoid were recruited fracture between March and July 2020. All underwent a 4-view X-ray. If this examination was normal, they were immediately referred for a CBCT scan of the wrist. Those with a normal scan were discharged to research follow-up at 2 and 6-weeks. 68 participants were recruited, 55 had a normal or equivocal X-ray and underwent CBCT. Nine additional radiocarpal fractures (16.2%) were demonstrated on CBCT, the remainder were discharged to research follow-up. Based on the 2-week and 6-week follow up three patients (4.4%) were referred for MRI to investigate persistent symptoms with no bony injuries identified. CBCT scans enabled a rapid pathway for the diagnosis or exclusion of scaphoid fractures, identifying other fractures and facilitating early treatment. The rapid pathway also enabled those with no bony injury to start rehabilitation, suggesting that patients can be safely discharged with safety-net advice following a CBCT scan.

Les traumatismes demeurent la principale cause de mortalité et de morbidité chez les jeunes adultes. Les traumatismes au bassin peuvent être mortels, principalement à cause d'un possible choc hypovolémique. Les fractures du bassin nécessitent une prise en charge rapide. Malheureusement, l'identification des patients avec une fracture pelvienne au préhospitalier est difficile et il existe actuellement peu d'interventions préhospitalières disponibles. La ceinture de compression pelvienne, une solution temporaire pour réduire le saignement, est utilisée à l'urgence, mais aussi au préhospitalier dans certaines provinces canadiennes et à l'international. Il y a toutefois une absence de consensus dans la littérature quant aux réels bénéfices associés et à savoir si son utilisation en préhospitalier dans notre système serait bénéfique. L'objectif de mon projet de maitrise était d'évaluer l'identification et la prise en charge des fractures du bassin à l'urgence et lors de la phase préhospitalière. Deux sous-études distinctes ont été utilisées pour établir le portrait de la situation dans la région de la Capitale-Nationale. Premièrement, une étude rétrospective de septembre 2017 à septembre 2021 comportant 228 patients traités au centre de traumatologie tertiaire à Québec. Cette étude a permis d'identifier un sous-triage élevé au préhospitalier et un manque de formation quant à l'installation de la ceinture dans les centres hospitaliers référents. La deuxième étude réalisée de juillet à août 2022 comportait deux cohortes prospectives : une collecte de données sur le terrain et une simulation à la Coopérative des techniciens ambulanciers du Québec (CTAQ). Sur le terrain, 29 patients ont été identifiés et 11 duos de paramédics ont participé à une simulation. Cette étude a permis de démontrer un manque de standardisation concernant l'évaluation du bassin au préhospitalier et par le fait même, des difficultés à bien les suspecter. Ces travaux s'inscrivent dans une lignée d'études portant sur l'amélioration des soins préhospitaliers d'urgence en traumatologie au Québec. / Trauma remains the leading cause of mortality and morbidity in young adults. Pelvic trauma can be fatal, mainly due to the hypovolemic shock sometimes associated with it. Pelvic fractures require rapid management to improve patient outcome. Unfortunately, identifying patients with pelvic fractures in the prehospital setting is difficult, and there are few pre-hospital interventions available. The pelvic binder, a temporary solution to reduce bleeding, is used in the emergency department, but also in the prehospital setting in some Canadian provinces and internationally. However, there is a lack of consensus in the literature as to the real benefits associated with it, and whether its use in the prehospital setting in our system would be beneficial. The aim of this master's project was to evaluate the identification and management of pelvic fractures in the emergency department and in the prehospital phase. Two separate sub-studies were used to establish a portrait of the situation in the Capitale-Nationale region. First, a retrospective study from September 2017 to September 2021 involving 228 patients who arrived directly or were transferred to the tertiary trauma center in Quebec City. This study identified high prehospital undertriage and a lack of training relative to pelvic binder installation in emergency departments. Secondly, a prospective cohort study was carried out from July to August 2022, involving two cohorts: data collection in the field and simulation at the Coopérative des techniciens ambulanciers du Québec (CTAQ). In the field, 29 patients were identified, and 11 paramedic duos participated in a case simulation. This study identified a lack of standardization in prehospital pelvis assessment, and consequently difficulties in correctly identifying them. This work is part of a line of studies to improve prehospital emergency care for traumatized patients in our healthcare system.