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Multicatalytic Cerium Photoredox Reactions for the Activation of O-H Bonds and Total Synthesis of (±)-Hyperolactone C
No full textRadical chemistry enables a wealth of valuable organic transformations in organic synthesis. Photoredox catalysis has made entry into this high-energy radical regime more appealing and often reveals unique reactivity and functional-group tolerance. Chapter 1 presents an overview of radical chemistry and the key role of photoredox catalysis in modern approaches to chemical synthesis. This thesis focused on the development of new photoredox platforms to access radical intermediates and their application in the synthesis of complex molecules.
In Chapter 2, a cerium photoredox platform was used to generate high energy O-centered radical intermediates from the native O-H bonds of common chemical feedstocks including alcohols, carboxylic acids, and 1,3-dicarbonyls. The multicatalytic system enabled a variety of redox-neutral transformations including fragmentation of lactols and cycloalkanols to the corresponding formate esters and ketones and hydrodecarboxylation. Synergistic application of cerium photoredox and nickel catalysis enabled a remote arylation reaction that furnished distal aryl and alkyl ketones via C(sp²)-C(sp³) and C(sp³)-C(sp³) cross-coupling in moderate to high yields without reliance on cycloalkanol ring-strain or redox-auxiliaries.
In Chapter 3, the photoredox platform was adapted to activate 1,3-dicarbonyl C(sp³)-H acids, forming radical intermediates that performed a plethora of reactions including hydroalkylation, oxidative cyclization, and cross-coupling. The discovery of both cerium-containing and cerium-free conditions prompted detailed mechanistic experiments that gave insight into important reaction. Exploration of reaction scope and mechanistic studies helped to develop our understanding of the platform. NMR and UV/Vis spectroscopy revealed ground-state equilibria between reaction components and the kinetics of thermal oxidation processes. Stern-Volmer fluorescence quenching experiments were used to elucidate the dominant photochemical events from catalyst excited states. Competition experiments and isotope studies helped determine the reaction path of organic substrates. Computational modelling was used to rationalize reaction outcomes including regio- and stereoselectivity, guided us in devising strategies for synthesis of more complex products, and ultimately enabled a total synthesis.
In Chapter 4, total synthesis of the natural product hyperolactone C displayed the utility of the photoredox platform in complex molecule synthesis. The hydroxyfuranoate intermediate was quickly assembled from abundant building blocks and enabled a 4-step synthesis, the shortest route to date. A Au(I)-catalyzed addition of glycolate esters to unsymmetrical propiolate esters, a previously underdeveloped hydroetherification reaction, and a Dieckmann condensation of the resulting Z-enol ether were developed to access hydroxyfuranoate esters. The densely functionalized spirolactone core with two contiguous stereocentres was constructed in the key final step using the oxidative photoredox cyclization that demonstrated remarkable tolerance for the oxidation-sensitive π-excessive furan heterocycle. Using the complementary redox-neutral hydroalkylation, we have also generated several analogues of this bioactive natural product. Inspired by the biosynthetic hypothesis for formation of biyouyanagin natural products, we performed an intramolecular [2+2] reaction to yield a 2-oxatricyclo[3.2.1.0³,⁶]octane-bearing compound that may represent an undiscovered natural product
Migración forzada, cosmopolitismo y memoria en la literatura latinoamericana contemporánea (El camino a Ítaca de Carlos Liscano, Más allá del invierno de Isabel Allende y Desierto sonoro de Valeria Luiselli)
No full textThis thesis studies the representation of forced migrations in the novels El camino a Ítaca (1994) by Carlos Liscano, Más allá del invierno (2017) by Isabel Allende, and Desierto sonoro (2019) by Valeria Luiselli. Through a theoretical reflection centered on vernacular cosmopolitanism and memory, I examine the ethical and political impetus behind the recourse to hybrid narrative forms to represent stories of displacement and migration. I show how by representing the experiences of exclusion, lack of rights, and hostility towards precarious migrants, these works expose the fissures in the traditional conception of cosmopolitanism and its ideals of global citizenship. In my reading, these novels reveal the limitations of this ideal and can also be understood as an archive of vernacular cosmopolitans’ memories. Furthermore, I argue that the works intertwine the current violence of marginal migrations with the violence of the Latin American dictatorships in the XX century, connecting the figure of the disappeared with migrant-related in a transnational context. Finally, in evidencing how fiction about transnational displacements challenges the fixed categories migrants and refugees, as well as ideas of global mobility, this study critically addresses contemporary conceptual debates on forced migration, cosmopolitanism, and memory
Garbage In, Garbage Out: Measuring and Predicting Insufficient Effort Responding in Survey Research
No full textThe validity and reliability of conclusions drawn from survey data are contingent upon the quality of responses provided by participants. When analyzing survey data, researchers assume participants are engaged and exert a sufficient effort responding to the survey items. While it was initially believed that most survey research participants are attentive, a growing body of evidence suggests that up to 50% of participants (Francavilla et al., 2019; Meade & Craig, 2012) put forth an insufficient effort responding (IER). Although IER represents a significant threat to survey research integrity, important gaps persist in the literature pertaining to the detection and prediction of IER. On the one hand, a standardizable IER detection approach has yet to be developed. On the other hand, even if understanding the process underlying IER is crucial to prevent it, a robust and widespread examination of the predictors of IER remains to be conducted. This thesis sought to tackle the aforementioned gaps across six studies divided into three manuscripts.
In Manuscript 1, a novel standardizable IER detection approach (i.e., multidimensional insufficient effort responding detection approach; mIERda) was introduced and its criterion validity was examined across a series of four simulation studies. Building on Manuscript 1, Manuscript 2 relied on a prospective design to further the validation of the mIERda and assess its construct validity using 18 datasets (N = 5014). Lastly, drawing on 23 datasets (N = 2216) collected over the course of two years, Manuscript 3 examined the contextual (i.e., survey length, study topic, time of the semester) and personal (i.e., personality, global motivation, motivation for research participation) determinants of IER using a prospective longitudinal design. Taken together, findings arising from this thesis provide evidence of the criterion (Manuscript 1) and construct (Manuscript 2) validity of the mIERda. Results from Manuscript 3 demonstrate a limited contribution from contextual determinants and suggest that IER is mostly driven by personal determinants. Results also support that global autonomous motivation acts as a protective factor against IER at the start of the survey, whereas amotivation for research is tied to greater odds of IER throughout the survey. These findings provide meaningful insight to guide recommendations pertaining to IER detection, survey design, and motivational interventions with the overarching goal of lessening the prevalence of IER and its impact on survey research
An Exploration of Neural Heterogeneity and its Consequences on Network Dynamics and Neuromodulation
No full textHeterogeneity is a pervasive and ubiquitous aspect of physical and biological systems. This is especially true in the brain, where heterogeneity exists across all scales, from genetics and ion channel distribution to cell types and patterns of neuron connectivity. This heterogeneity has been linked to stable, persistent behaviour, increased information transmission, and effective neural encoding. Importantly, although neural heterogeneity is often regarded as a static property and modelled as a fixed meta-parameter, this is not the case in the brain. Rather, heterogeneity is, in many instances, a dynamic property of the brain that alters in response to persistent activity and brain state which has been associated with increased stability and robustness. However, the importance of specific manifestations of heterogeneity, in static or dynamic forms, is less clear. That is, recent research has shown that, despite many decades of research exploring animal-to-animal and cell-to-cell heterogeneity, it may have no bearing on the net electrical output of the cells and that neurons possess considerable electrophysiological overlap despite their heterogeneous composition.
In this thesis, we explore heterogeneity in both its malleable and static forms. We first propose a model for a firing rate-based homeostatic adaptation of neural excitability (e.g. gain). Endowing a simple network model of excitatory neurons with this candidate mechanism and heterogeneous excitability. Measuring the net heterogeneity as a function of the average pairwise difference between neurons, we explore how this heterogeneity may be up- or down-regulated in response to external stimulation and network-related factors such as degree of connectivity, and presynaptic firing rate and weights. Maintaining heterogeneity in neural excitability has been experimentally and computationally demonstrated to be crucial to having persistently stable network dynamics. Notably, these observations have been made in very generalized frameworks, where the heterogeneity in neural excitability is assumed to arise from similar distributions for all cell types. However, highly detailed datasets of human cortical neurons have demonstrated this to be inaccurate. Rather, subtypes of cells have characteristic groupings of responsiveness and input sensitivity (e.g. excitability). Leveraging one such dataset made freely available by the Allen Institute for Brain Science, we investigate the effects of distinct excitabilities between the excitatory and inhibitory neurons on network dynamics.
Beyond excitability, we consider the effects of morphological (e.g. neuron architecture) heterogeneity on neurons’ responses to external stimulation. Using biophysically accurate, freely available models of mouse primary visual cortex neurons, we do a detailed characterization of their whole cell (e.g. length, volume, etc.) and compartmental (e.g. branch thickness and length, etc.) traits. Simulating the neuron models under a uniform electric field, we record the somatic membrane potential response and link it to the strength of the applied field to define the susceptibility of each neuron to simulation. Thereafter, correlation and partial correlation analyses are performed to explore the importance of morphological traits to neuron susceptibility. The null results of these efforts then suggest that the high degree of heterogeneity in neuron morphology may limit the selectivity with which they can be targeted, and support the notion that neurons demonstrate high electrophysiological overlap
An Evaluation of Incident Chronic Kidney Disease Across Ontario and Healthcare Utilization Through Predictive Risk Equations
No full textChronic Kidney Disease remains a common, progressive condition that affects approximately one-tenth of the adult population. Despite its marked prevalence, there has yet to be a true estimation of its incidence within Ontario, Canada. The first objective of this thesis is to evaluate the incidence of early-stage CKD across Ontario and determine which groups are most at-risk. The implications of these results we hope will help determine resource allocation for policy makers and raise awareness for those who have a higher likelihood of developing CKD. The second objective will be to identify those who are at risk of CKD using a risk equation and determine their healthcare utilization, specifically investigating primary care access, specialist referrals, disease monitoring, and prescription management, across risk categories. These results will describe how those at higher risk of CKD are being evaluated and managed throughout their healthcare journey
Synthesis of Ruthenium Complexes with "PNR" (R = H, Me) Ligands and Their Role in the Electrocatalytic and Photocatalytic Reactions
No full textRepurposing CO₂ in the atmosphere is a key strategy to combat global warming and reduce fossil fuel capture conditions. Molecular catalysts (metal complex catalysts) can be precisely designed at the molecular level to accelerate CO₂ conversion reactions. Different classes of metal complexes catalyzed the reduction of CO₂ with astonishing efficiency and selectivity. Recently, numerous semiconductor photocatalysts were designed in heterostructure systems, which are composed of complex components of semiconductor and metal. Homogeneous metal complexes can be employed to study reaction processes more straightforwardly than the heterogeneous method.
This study focuses mainly on proposed mechanisms driving the photochemical reduction of CO₂ initiated by ruthenium complexes. Ruthenium complexes mainly produce HCOOH and H₂, and the product selectivity is highly dependent on the reaction conditions. This study investigated complexes of ruthenium with bidentate phosphino-aminopyridine ligands for their photocatalytic activity. Catalysis was carried out using as solvent, 4 mL of a solution of this complex in N, N-dimethylacetamide (DMA), with [Ru(bpy)₃]²⁺ as a photosensitizer, and 1 mL of triethanolamine (TEOA) as a sacrificial agent in the presence of carbon dioxide. LEDs (1050 mW, 700 mA, 3.4 x 10⁻⁸ mol photons/sec) at 450 nm wavelength were used to irradiate the reaction mixture with visible light.
The results show that the photocatalytic activity is greatly enhanced by the presence of the ligand group. NMR spectroscopy and gas chromatography confirmed the generation of carbon monoxide (CO), hydrogen (H₂), and formic acid (HCOOH) via the photocatalytic reduction of CO₂ catalyzed by ruthenium complexes.
Graphical Abstract: Ru-based complexes synthesized with various substituents on the N-(diphenylphosphino)-2-aminopyridines ligand were investigated for their behaviour in photocatalytic CO₂ reduction
Evaluation of Noble Gas Extraction Methods for Inter- and Intragranular Porewater in Argillaceous Rocks
No full textThe long-term, safe storage of nuclear waste within deep geological formations represents a critical focus of contemporary research and public interest. As nuclear energy continues to be an essential component of sustainable energy strategies – particularly within Canada – the use of noble gases as tracers of physico-chemical processes for the site characterisation of prospective Deep Geological Repositories (DGRs) is a promising yet technically challenging approach. This study develops and evaluates methodologies for extracting and quantifying isotopic noble gases from the porewater of the Opalinus Clay (OPA) formation in northwest Switzerland, a well-established analogue for argillaceous DGR settings (Bossart and Thury, 2008). The first study (Chapter 2) examines the traditional encapsulation of cores for porewater analysis within stainless-steel cylinders and evaluates three normalization techniques for estimating initial porewater concentrations from headspace noble gas measurements. A second study (Chapter 3) explores a more cost-effective encapsulation method involving core samples stored in vacuum-sealed PE/Al-foil bags, similar to Zuo et al. (2021). However, this method presented challenges due to limited degassing. Consequently, this required low-temperature baking to promote outgassing to form a headspace over a period of six weeks, although this process may have introduced isotopic fractionation associated with He, and elemental fractionation in Ne and Ar. Consequently, additional preparation, storage, and extraction refinements may be needed to realise the potential of this technique. Collectively, these findings highlight key methodological considerations in sampling and analysing argillaceous cores for noble gases, highlighting the need for further refinement towards establishing more comprehensive “best-practice” protocols
Dynamic and Stochastic Decision-Making: Applications in Healthcare Operations
No full textHealthcare delivery, disaster response, and other large-scale operational problems in healthcare share a common challenge: they require the efficient allocation of scarce resources under uncertainty, time pressure, and complex interdependencies. This dissertation develops novel optimization and decision-support frameworks that address this challenge by combining rigorous mathematical modeling with advanced approximation techniques. While the application domains differ, from scheduling patients in specialized clinics to evacuating vulnerable populations during wildfires, the underlying motivation is the same: to design resource allocation strategies that are both effective in practice and computationally tractable for real-world problems.
The second chapter of this thesis addresses the scheduling of patients in healthcare settings where multiple appointment types, priorities, and dependencies must be managed simultaneously. Most traditional scheduling practices ignore the fact that diagnostic tests and specialist consultations are interdependent, or that lead times and patient priority levels critically affect care quality. To bridge this gap, a dynamic scheduling model is developed that integrates these factors, ensuring that tests and consultations are coordinated in a timely and efficient manner. Using the linear programming approach to Approximate Dynamic Programming (ADP), an efficient approximation of the value function is derived, resulting in an efficient scheduling policy. Simulation experiments based on real-world clinical data show that the proposed policy outperforms existing benchmarks, significantly reducing waiting times and improving compliance with care protocols. In addition, a practical heuristic, designed for direct adoption by hospitals, achieves comparable performance while remaining interpretable and easy to implement. These contributions underscore the importance of bridging theoretical advances with practical applicability.
The third chapter of this thesis shifts to the context of disaster response, focusing on supported evacuations during wildfires. Unlike self-evacuations, supported evacuations involve individuals who require direct assistance, such as hospital patients or residents of long-term care facilities, for whom evacuation is significantly more complex. Here, the problem is not only one of vehicle routing and fleet sizing, but also of ensuring that evacuations occur within narrow time windows while considering the possibility of infrastructure disruptions. A two-stage stochastic optimization framework is proposed to capture diverse sources of uncertainty and complexity associated with vehicle routing, facility location, and fleet sizing decisions. Given the computational challenges of such decisions, a novel solution methodology based on Logic-Based Benders Decomposition is developed, further enhanced by combinatorial inequalities and neighborhood search strategies. Numerical experiments, including one based on data from a community wildfire drill in Colorado, demonstrate that the proposed solution approach provides substantial improvements in evacuation time and resource utilization compared to existing approaches. This work highlights how stochastic modeling and advanced decomposition methods can produce actionable strategies in time-critical disaster management settings.
The fourth chapter of this thesis is methodological and addresses the broader challenge of solving high-dimensional infinite-horizon dynamic programming problems. Many resource allocation problems in healthcare, disaster response, and beyond can be framed as sequential decision-making problems, but exact solutions are typically intractable due to the curse of dimensionality. To mitigate this, a novel piecewise affine approximation framework is introduced for regional value function approximation. Instead of assuming a single global approximation, the method adaptively partitions the state space and fits localized affine functions in regions where the value function is highly nonlinear or irregular. The proposed approach, which is simulation-driven, iteratively refines partitions, balancing accuracy with interpretability. Experiments across diverse domains, including queueing systems, energy storage management, and patient scheduling, show that this method achieves superior performance compared to traditional single-function approximations. More importantly, it provides better approximations while maintaining computational efficiency, making it a versatile tool for approximate dynamic programming applications.
Taken together, the contributions of this dissertation demonstrate both breadth and depth. From an application perspective, the research presented in this thesis addresses two globally critical challenges: improving access and timeliness in healthcare delivery, and enhancing preparedness in disaster response. From a methodological perspective, this thesis advances the frontier of approximate optimization techniques, particularly in dynamic programming and large-scale stochastic systems. A unifying theme across all three studies is the emphasis on balancing rigor with practicality. Each chapter not only provides a novel theoretical approach, but also yields solutions that can be implemented and trusted in real-world settings where decisions are urgent and stakes are high.
This dissertation thus contributes to the fields of operations research, healthcare analytics, and disaster management by developing scalable, interpretable, and implementable optimization frameworks. By integrating domain-specific modeling with generalizable approximation methods, it provides a foundation for tackling a broad class of resource allocation problems under uncertainty, that are increasingly central in today’s complex and interconnected world
Blast and Post-Fire Behaviour of Glued-Laminated Timber Panels
No full textThe increasing trend toward taller timber structures, built with mass timber panels, has made it essential to understand the multi-hazard response of these structural elements and how subsequent or simultaneous hazards affect their performance. Current design standards provide guidelines for individual hazards, such as fire, blast, seismic, and wind in isolation, and only conceptual holistic design frameworks have been proposed, focusing mainly on redundancy and stability under multiple hazards. Limitations in conducting research on structural elements subjected to multi-hazard scenarios are largely driven by the high cost and practical challenges associated with such experiments.
An experimental program was developed that included twenty-three full-scale uncharred and charred glued-laminated timber panels tested under static and dynamic loading, with a focus on establishing their performance before and after exposure to a short-duration real fire. Simulated blast tests were conducted at the University of Ottawa Shock Tube facility, and the charred panels were extracted from the Mass Timber Demonstration Fire Test Program, a full-scale field fire test conducted in Ottawa, Canada, in 2022. In addition to the full-scale structural tests, twenty-five charred samples were examined using image analysis software.
The experimental results showed that the theoretical dynamic zero-strength layer value exceeds the static value, suggesting rate-dependent effects. The findings also demonstrated that a single-degree-of-freedom model with the Reduced Cross-Section Method can be a reliable predictive tool with proper inputs to simulate the dynamic response of structural elements for fire followed by blast loading scenario; a methodology that can be extended to other timber structural elements. Based on the experimental results, recommendations for Canadian design provisions were highlighted and discussed, and a detailed design example was presented
Transport Phenomena in Oscillatory Flow Mini Coils for Solid-Forming Reactions
No full textTraditional pharmaceutical and fine chemical production processes possess a high degree of flexibility because batch or semi-batch stirred tank reactors are primarily utilized, which aren't often allocated to any specific reaction or product; instead, they are flexible to produce different chemicals via various reactions at a wide range of operating conditions. This flexibility is associated with some problems, such as low heat transfer performance, poor mixing quality, and fouling. Reducing the problems associated with traditional pharmaceutical processes is included in the concept of "Process Intensification," which refers to methods and modifications implemented in a process to enhance its efficiency and economy, such as reducing equipment volume, handling chemical reactions at optimized conditions, decreasing energy consumption, and waste materials.
The focus of this research was on the intensification and characterization of a coil reactor capable of handling solid-forming reactions and potentially applicable to pharmaceutical industries. This type of reactor has been partially intensified as its flow is continuous, and its volume reduced relative to batch-wise operation. In this work, oscillatory flow at different operating conditions (frequency, amplitude, and net flow rate) was applied to the fluid flowing in the reactor, aiming to better intensify its performance.
First, the behavior of fluid flow inside the reactor in terms of residence time distribution (RTD) and associated axial dispersion was experimentally investigated and mathematically characterized by a statistical model. The results showed that there is a point at which the axial dispersion under oscillatory conditions is minimum. The axial dispersion was also correlated with the operating conditions and coil dimensions by a Dean number with the flow amplitude as the characteristic length.
Second, the viscous power dissipation and phase shift between the coil pressure drop and velocity at different oscillatory conditions was numerically studied by a CFD model in order to better understand the relationship between the instantaneous flow field, power dissipation and the RTD variance.
Third, the enhancement of the wall-to-fluid heat transfer was evaluated under non-oscillatory and oscillatory conditions. For the non-oscillatory experiments, three new correlations were developed for the thermal entrance length of coils, Nusselt number of developing laminar flow, and combined (developing and developed) flow, and the Nusselt number of turbulent flow. The result showed that the heat transfer coefficient of coils in laminar flow is not significantly dependent on the coil curvature. Then the Nusselt number of the oscillatory flow was characterized using the non-oscillatory results and correlated with the operating conditions and coil dimensions. The results showed that although oscillation can enhance the coil heat transfer coefficient, the amount of enhancement is limited by the net flow rate.
Finally, the reactor performance during a sample solid-forming reaction was characterized, and the effect of oscillatory conditions on the particle size distribution was studied. The net flow rate and oscillation frequency can effectively change the particle size, while the effect of amplitude needs more investigation for different reactions. In addition, online measurement of the pressure drop for a concentrated reaction showed that oscillation can extend the operation time by decreasing the amount of fouling and consequently the risk of blocking.
According to the achievements in this research, applying oscillation can provide ranges of operating conditions in which the plug flow performance, convective heat transfer coefficient, particle growth, and PSD broadness are optimized. However, these ranges are mostly independent, and for quantities related to solid forming reactions, they are case-specific. Therefore, to design a reactor for a specific solid-forming reaction, a trade-off must be established between different design parameters such that more important quantities are in acceptable ranges