identifier: Germé, Katuschia  (2021) Brain mechanisms of sexual disinhibition in the male rats by alcohol and amphetamine.  PhD thesis, Concordia University.

abstract: The expression of sexual behavior requires a proper balance between inhibition and excitation at cognitive, hormonal and neurochemical levels. Inhibition of sexual behavior is considered to be important and even crucial to maintain proper social cohesion and adaptation (i.e. in response to threat, aversion, culture, fertility). In humans, spreading of sexually transmitted diseases is often due to inappropriate and risky sexual behavior (e.g. multiple partners, no use of condoms) or to a loosening of inhibitions under the influence of drugs. It is therefore important to understand where these drugs (recreational, or prescription) act to induce disinhibited sexual behavior. In this thesis, the mechanisms of action of two drugs associated famously with sexual disinhibition but possessing two largely opposite mechanisms of action, alcohol and d-amphetamine, are investigated. This is done using a conditioned partner avoidance paradigm in which male rats are trained to avoid copulation with females bearing a conditioned inhibitory olfactory cue associated with non reward. This paradigm has been used previously to reveal the disinhibitory properties of low doses of alcohol. In the first chapter, it is established that d-amphetamine disrupts conditioned partner avoidance as d-amphetamine-treated males still copulate with females bearing the conditioned inhibitory cue. Furthermore, similar to alcohol, exposure to the inhibitory cue alone under the influence of d-amphetamine activates brain regions associated with sexual behavior and sexual reward. As alcohol is known to induce disinhibition of behavior in general and of sexual behavior in particular, the focus of the second and third chapters is to examine the potential neurotransmitters involved in the disinhibitory effect of alcohol. Using microdialysis, it is found that levels of dopamine in the nucleus accumbens are increased when alcohol-treated male rats are exposed to the sexually conditioned inhibitory cue. This increase is due to activation of dopaminergic neurons from the ventral tegmental area. On the other hand, neither alcohol nor the conditioned cue has an effect on glutamate or GABA levels in the nucleus accumbens. Together these data demonstrate that dopamine release in the nucleus accumbens via activation of dopaminergic neurons in the ventral tegmental area plays a permissive role in the disinhibitory effects of alcohol (and likely amphetamine) on the sexual behavior of male rats.


identifier: khoddami, shohre  (2021) A System Dynamics Approach to Comparative Analysis of Biomass Supply Chain Coordination Strategies.  Masters thesis, Concordia University.

type: Thesis NonPeerReviewed

abstract:
Biomass is one of the most efficient renewable energy sources to increase energy security and reduce the environmental issues. It could be utilised as back-up or main source of energy in off-grid remote northern communities of Canada, which are currently rely on fossil-fuels. However, small scale of energy demand, necessity of continuous energy supply, and spatial dispersion of such remote communities restrict the competitiveness and efficiency of bioenergy.
Managing bioenergy supply chain from supplying biomass to conversion facilities is vital to overcome the challenges in expanding bioenergy production. In this sense, forming collaboration among the entities plays a key role to improve the economy of scale and efficiency of bioenergy production. In the literature, several coordination strategies resulted in varying impacts on entities’ profit or cost. As such, analyzing and comparing them in various conditions could assure selecting the most efficient one. This study recommends quantity discounts and cost-sharing coordination policies to promote the biomass level at communities in a cost-efficient manner through establishing bundling orders and benefiting the lower cost.
This dissertation employs a system dynamics approach to simulate coordination scenarios and make the optimal decisions in a biomass supply chain including suppliers, hubs, and end-user. On that basis, performing a comparative analysis under various conditions and assumptions provide insights into the impact of coordination and selecting the preferred choice of coordination strategy for each player. The simulation-based optimization model is applied to a bioenergy supply chain case study in Canada’s off‐grid northern communities. The results of this research point to a significant role of coordination in improving the cost efficiency as well as the level of biomass-based energy production.


identifier: Ajjoub, Carl  (2021) A systematic analysis of equity issuance: evidence from around the world.  Masters thesis, Concordia University.

abstract: This study conducts a systematic analysis of seasoned equity offerings across a sample of twelve countries with differing legal systems at the micro level from 2009 to 2019. Civil law countries have been shown to exhibit reduced shareholder protection rights, causing the cost of equity for firms in those countries to be higher and thus making equity issues less attractive. In this paper, we start by using a series of logistic regressions to examine if firms in civil law countries are less likely to pursue financing through seasoned equity offers. More importantly, we employ a range of interaction variables to examine whether the SEO decision policies and likelihood to issue SEOs differ across legal systems based on firm-specific characteristics. Our results indicate significant differences in SEO decision relevance for some firm-specific variables. The results were mainly robust across our subsamples and alternate models, with a few exceptions specifically for our size subsamples.


identifier: Gerchicoff, Brent Thomas  (2021) The Dynamics of Containment: Alliance Cohesion and American Domestic Politics in Foreign Policy.  PhD thesis, Concordia University.

abstract:
Containment policy has been the dominant grand strategy of the United States throughout the second half of the twentieth century. This dissertation answers the following question: What variation is likely given different structural alliance configurations and domestic constraints? This dissertation will test the relationship between the cause, e.g. alliance cohesion (and domestic structures as the intervening variable) and resulting effect, type containment (proto-, containment, rollback) implemented by US. Through case study methodology and primary source textual analysis, I will test this argument against the Cold War historical record.
This dissertation finds that the dependent variable of foreign policy, specifically the typology of containment is largely determined by the independent variable, alliance cohesion (e.g. whether the alliance partners are balancing or intra-alliance bargaining with the alliance leader, or if the state fears the leader will not fulfill its defensive commitments). This relationship, with the inclusion of executive autonomy or constraint in domestic structures (IVV) is largely responsible for the foreign policy output by the United States in all but one of the case studies used to test this dissertation’s argument. The deviating case study demonstrates that the Carter Administration’s neglecting the alliance cohesion – containment policy axis led to, in effect, being selected out of American leadership and the Ronald Reagan reset with alliance politics and containment foreign policy at the forefront of the Administration’s foreign relations.
The discussion of containment strategies is a critical contemporary issue given the recent rise of the People’s Republic of China threatening to surpass the United States as the most powerful state in the international system, likely with hegemonic ambitions. Given that containment is a foreign policy short of war, makes this a strategy worth considering when confronting the reality of a rising nuclear revisionist power. At the time of this writing, there is no model that lays out the theoretical conditions which decision-makers will implement a policy of containment. This dissertation builds this theory. In demonstrating containment as a grand strategy that resides within a theoretical framework of a security policy short of war will open up possible foreign policy alternatives for states to consider.


identifier: Yang, Bowen  (2021) Season-Based Occupancy Prediction in Residential Buildings Using Data Mining Techniques.  Masters thesis, Concordia University.

abstract: Considering the continuous increase of global energy consumption and the fact that buildings account for a large part of electricity use, it is essential to reduce energy consumption in buildings to mitigate greenhouse gas emissions and costs for both building owners and tenants. A reliable occupancy prediction model plays a critical role in improving the performance of energy simulation and occupant-centric building operations. In general, occupancy and occupant activities differ by season, and it is important to account for the dynamic nature of occupancy in simulations and to propose energy-efficient strategies. The present work aims to develop a data mining-based framework, including feature selection and the establishment of seasonal-customized occupancy prediction (SCOP) models to predict the occupancy in buildings considering different seasons. In the proposed framework, the recursive feature elimination with cross-validation (RFECV) feature selection was first implemented to select the optimal variables concerning the highest prediction accuracy. Later, six machine learning (ML) algorithms were considered to establish four SCOP models to predict occupancy presence, and their prediction performances were compared in terms of prediction accuracy and computational cost. To evaluate the effectiveness of the developed data mining framework, it was applied to an apartment in Lyon, France. The results show that the RFECV process reduced the computational time while improving the ML models’ prediction performances. Additionally, the SCOP models could achieve higher prediction accuracy than the conventional prediction model measured by performance evaluation metrics of F-1 score and area under the curve. Among the considered ML models, the gradient-boosting decision tree, random forest, and artificial neural network showed better performances, achieving more than 85% accuracy in Summer, Fall, and Winter, and over 80% in Spring. The essence of the framework is valuable for developing strategies for building energy consumption estimation and higher-resolution occupancy level prediction, which are easily influenced by seasons.


identifier: Roelens, Abigail K  (2021) Dying in the Southwest.  Masters thesis, Concordia University.

title: Dying in the Southwest

abstract: Dying in the Southwest explores the relationship between the individual, the collective, and the larger socioeconomic systems that provide the foundation of the places we call home. The collection focuses primarily on the city of Windsor, Ontario, which was known as “Ground Zero” during the 2008 Financial Crisis. Due to high rates of unemployment, stagnant wages, and low desirability for investment, the people of Windsor-Essex County found themselves trapped within a constantly shaken snow globe. Inside this microcosm, habits and routines were broken and patched over hastily in order to survive. The poems follow the small, personal dramas that play out alongside and within the macroeconomic crisis. Dying in the Southwest captures the many attempts made to endure, adapt, or escape the city. Stagnation and failure pervade these attempts. Misdirection, error, and unwillingness to change lie at the core of both the cause and effect of the Financial Crisis. Throughout the collection, Dying in the Southwest maintains a balance of hope and cynicism for a city so ravaged by large-scale systems beyond its control.


identifier: Sergio Esteban, Rosales Garzón ORCID: https://orcid.org/0000-0001-8058-4197 <https://orcid.org/0000-0001-8058-4197>  (2021) Earth pressure on walls retaining overconsolidated cohesionless soil using the concept of critical state soil mechanics.  PhD thesis, Concordia University.

format: text video video video spreadsheet spreadsheet spreadsheet

abstract: The plane-strain (PS) critical-state (CS) friction angle is an important soil parameter in the design of several geotechnical projects. The static angle of repose, which is known to be the same as the PS-CS friction angle for normally consolidated cohesionless soil (NC), and the associated initial constant-volume friction angle were measured for three granular materials in the laboratory to validate the flow rule that accounts for dilatancy and accordingly the pore pressure coefficient A. To derive the flow rule, the law of conservation of energy and limit equilibrium technique were used to develop a bidimensional micromechanical model representing granular media in CS. The flow rule was then used to predict the at-rest coefficient K0-OC and theoretical porosity thresholds for the contractive, dilative, and collapsible behavior. The lateral stresses of silica sand under the standard and modified Proctor energies of compaction, and non-compacted, were measured in the laboratory for different Dr and OCR to validate the proposed K0-OC. As a by-product of the previous finding, a new methodology to determine OCR in compacted backfills was developed. For the active and passive states, the variational limit equilibrium method applied on NC dry granular media and the PS-CS friction angle were adopted to derive the nonlinear geometry of the slip-failure surface and the associated nonlinear coefficients Ka and Kp. The present micromechanical model was further used to develop a numerical approach to model the stress‒strain path and determine the minimum wall rotation required to develop PS-CS failure. Practical application, and design framework were prepared for various spreadsheets and illustrative examples.


identifier: Dunbar, Amanda Light  (2021) SparkNotes Use and Attitudes Among High School English Language Arts Students: A Retrospective Exploratory Mixed-Method Study.  Masters thesis, Concordia University.

abstract: This mixed-method study explored recollections of SparkNotes use among high school students in terms of the rate of use, the reasons for use, and the characteristics of users. The study also explored feelings and attitudes about SparkNotes use, particularly whether or not it is considered a form of cheating. An electronic survey collected quantitative and qualitative data from 209 anonymous participants with high school graduation dates between 2000 and 2020, most of whom described themselves as good readers who enjoyed reading. Sixty-nine percent reported that they had used SparkNotes for support with English homework, and this proportion did not vary significantly across geographic, vocational, or reading behavior-based cohorts, although there was a slight positive association between SparkNotes use and graduation year. Participants mainly reported using SparkNotes when they needed help understanding a text (68%) or remembering details of what they had read (66%), or when they had not entirely read the text (57%). Forty percent of participants said that using SparkNotes is not cheating, and 38% said it depends. When prompted for elaboration, participants offered qualitative comments suggesting intellectual engagement, plagiarism, and not reading as main factors in determining the legitimacy of a student’s SparkNotes use. The implications of these findings are discussed in terms of New Literacy Studies. Overall, results of the study indicate that SparkNotes is widely used as both a supplement to and a partial replacement for reading primary texts in high school English class, and that whether or not this is considered cheating depends largely on individual conceptions and values around reading.


identifier: Marquis, Didier  (2021) Bugging the Human Diet: An interdisciplinary study on insects as future foods.  PhD thesis, Concordia University.

abstract:
As food supply practices must adapt to the reality of limited natural resources, we must find alternative solutions to meet the dietary needs of a growing world population. This dissertation reports on the viability of edible insects as a solution to globally improve food security. Compared to conventional livestock, insect production requires less feed, water, and space while generating less pollution and waste. Moreover, circular insect farming methods can allow the reintroduction into the food chain of various types of clean and traceable organic residues in order to produce sustainable animal proteins within cities, therefore improving food sovereignty at the local scale. However, the general aversion for edible insects represents a major barrier that must be alleviated.

This dissertation identifies strategies to efficiently and sustainably introduce insect farming and consumption at the city scale. The introductory chapter of this thesis provides the rationale behind my research, framing its research area and explaining its key objectives. The second chapter is oriented towards consumer behavior as it focuses on the challenges related to marketing insect food products, paying particular attention to the motivations driving food choices. The third chapter exposes the results of both a national survey I developed aiming to assess the perceptions and attitudes of Canadians towards entomophagy (i.e. insect consumption) as well as insect tastings I organized in order to develop a better understanding of Quebeckers’ preferences for edible insect products. The fourth chapter exposes an action research project I led involving high school students delving on exposure and familiarization with edible insects as an avenue to positively change their perception towards entomophagy. The fifth chapter discusses how following industrial ecology principles in insect farms can allow to lower both production costs and environmental impacts. Finally, the concluding chapter holistically reflects on entomophagy and entotechnologies (i.e. insect farming practices) as sustainable solutions to reduce the ecological impacts linked to the production and consumption of animal proteins – tackling food waste and thus reducing the carbon footprint associated to the management of rapidly decomposable organic materials.


identifier: Dutta, Sukanya  (2021) Plug-in On-Board Single-Phase Cuk-Derived Bridgeless EV Charger for AC and DC Charging Systems.  Masters thesis, Concordia University.

abstract:
Electric vehicles (EVs) have recently garnered popularity in the consumer market due to its environment friendly nature as it uses clean energy to power vehicles. The EVs that are on road majorly comprise of two-wheeler, E-rickshaw, intralogistics equipment, trio, golf carts, short range mobility vehicle, which come under the category of low power EVs and passenger buses, loading trucks, electric trucks, which fall under the category of high power EVs. Batteries are the primary source of energy to power these EVs. Therefore, to recharge these batteries a battery charger is required. The conventional battery chargers have the merit of easy implementation but have higher component count, lower efficiency, complex control, low input power quality, and inflexible charging options. In order to achieve unity power factor (UPF), low THD, and high power quality; a power factor correction (PFC) unit becomes a crucial part of the AC-DC converters of the battery charger. The DCM design proves advantageous due to its inherent PFC operation at the input side, reduction of switching losses due to zero turn-on losses as well as zero reverse recovery diode losses. Also, the control circuit becomes simple as it requires only a single control loop and a single sensor. Thereby, making the converter reliable and robust towards high frequency noise. Further, to make the EV battery chargers flexible and to combat range anxiety, vehicle-to-vehicle power transfer aids in solving the issue.

This thesis analyses and designs a single-phase bridgeless Cuk-derived converter as onboard EV charger for AC and DC charging systems. At first, a single sensor based Cuk derived PFC AC-DC converter has been analyzed and studied which has the advantages of lower component count, improved efficiency, high power quality, and low cost. The converter is designed in DCM to accomplish PFC naturally on the input side. The voltage stress is lower compared to the conventional Cuk converter thereby, reducing the switching losses and enhancing the overall system efficiency. The converter control is simple requiring only one voltage loop and sensor. The detailed small-signal modelling using the current injected equivalent circuit approach and controller design has been presented. Further, to enhance the charging flexibility to mitigate the range anxiety, the same topology has been analyzed and designed for V2V charge transfer. A novel charge transfer technique has been implemented using the same topology. The loss analysis for both configurations has been reported in detail. The steady-state analysis and converter design for both configurations has been provided. Simulation results from PSIM 11 as well as proof-of-concept hardware prototype results are discussed extensively to validate the converter analysis, design and high performance.


identifier: Li, Rong  (2021) Three Essays on Online Consumer Engagement.  PhD thesis, Concordia University.

abstract: This thesis, comprised of three essays, examines the critical roles in driving consumer engagement on social media. Essay 1 explores the role of personification in consumer engagement. Drawing on the literature on personification in advertising, the Stereotype Content Model (SCM), and well-being theory, the essay demonstrates that compared with a non-personification appeal, a personification appeal featured in the brand posting leads to a higher level of consumer engagement. Across three studies, the findings show that a personification (vs. non-personification) appeal triggers consumers’ perceived warmth of the brand, which in turn heightens their need for social belongingness, thus leading to a higher level of consumer engagement. Further, hedonic motive from the perspective of consumers is identified as a boundary condition to such an effect. Specifically, the results show that hedonic motive enhances the serial mediation effect driving consumer engagement. Essay 2 draws on the literature on self-brand connections and advertising creativity, examining the downstream consequence of consumer engagement triggered by a personification appeal and identifying a moderator such as brand familiarity. Across two studies, the results demonstrate that a personification (vs. non-personification) appeal strengthens self-brand connections via perceived warmth and consumer engagement. Further, the effect of personification appeals on consumer engagement is amplified when the brand is unfamiliar rather than familiar. Essay 3 draws on autonomy-connectedness literature, self-construal theory, and self-congruity theory, exploring the interactive effect of autonomy-connectedness appeals and self-construal on consumer engagement. Across two studies, the results reveal that compared with connectedness-appeal content, autonomy-appeal content leads to higher engagement among consumers primed with independent self-construal, whereas connectedness-appeal (vs. autonomy-appeal) content leads to a higher level of engagement among consumers primed with interdependent self-construal. Further, the essay uncovers the underlying mechanism such that content self-congruity mediates the interactive effect of the appeal type and self-construal on consumer engagement. General discussions, theoretical contributions, and managerial implications are provided, respectively, in these three essays. Limitations and future research are also discussed, respectively.


identifier: Alizadeh, Habib  (2021) Simplicial volume and non-positive curvature.  Masters thesis, Concordia University.

abstract:
The simplicial volume is a non-negative real valued homotopy invariant of closed connected
manifolds measuring how efficient the fundamental class can be represented by real singular
cycles. The problem of determining whether the simplicial volume of a given manifold is
non-zero has been a challenge. It is known that the simplicial volume of negatively curved
manifolds is positive [15]. Losing the negative bound on the sectional curvature, it has
been shown that locally symmetric spaces of non-compact type have positive simplicial
volume [21]. In their 2018 paper, C.Connell and S.Wang showed that the simplicial volume
Xn \
of n-manifolds with non-positive sectional curvature and negative 4 ` 1 -Ricci curvature
have positive simplicial volume, which confirms the Gromov’s conjecture in special cases. The conjecture states that the simplicial volume of manifolds with non-positive sectional curvature and negative Ricci-curvature is positive. In this master thesis we will introduce required notions and preliminaries and present detailed proofs of the results mentioned above.


identifier: Morrice, Elliott  (2021) The Effects of Light, Colour, and Print-Size on Reading Speed in the Visually Impaired.  PhD thesis, Concordia University.

abstract: Reading is an essential component of daily life and it can be one of the most difficult tasks faced by individuals with low vision. A variety of factors, e.g., magnification, print-size, lighting, and colour, have been shown to improve reading speeds in the visually impaired, but there is no gold standard measure that can be used to assess optimal colour and illumination to facilitate reading. Increased print-size and luminance have consistently been shown to improve reading speed, and improved lighting has also been shown to improve the overall quality of life of the visually impaired. Conversely, colour manipulation, e.g., different coloured lighting, lens filters, plastic overlays, are controversial in their utility as there is contradictory evidence for their efficacy at improving reading speed. Additionally, there is a lack of research in the field examining at how both lighting and colour can be manipulated simultaneously, at various print-sizes, to examine their impact on reading speed in both the visually and non-visually impaired. Consequently, improved luminance and increased print-size are standard practices in low vision rehabilitation (LVR), however, the use of colour in LVR is likely to be more nuanced, individualistic, and/or not adequately assessed. Unfortunately, in the field of LVR there is no accepted and validated gold standard measure that can be used to determine optimal colour and illumination to facilitate reading at various print-sizes. Therefore, the purpose of this dissertation is to examine the effects of colour, illumination, and print-size on reading, and to compare/contrast the efficacy of novel assistive technology devices that may be used in the context of LVR to determine optimal colour and illumination to facilitate reading.


identifier: Jain, Arihant  (2021) Moments of Cubic Hecke L-Functions.  Masters thesis, Concordia University.

title: Moments of Cubic Hecke L-Functions

abstract: Moments of families of L-functions provide understanding of their size and also about their distribution. The aim of this thesis is to calculate the asymptotics of the first moment of L-functions associated to primitive cubic Hecke characters over $Q(\omega)$ and upper bounds for 2k-th moments for the same family. Both of these results assume Generalized Riemann Hypothesis. We consider the full family of characters which results in a main term of order x log x. We also calculate conditional upper bounds for 2k-th moments for the same family and conclude that there >> x primitive characters of conductor at most x for which the L-function doesn't vanish at the central point.


identifier: Ghassemi Panah, Anahita and Paraschivoiu, Marius  (2021) CFD Based Estimation of Wind Energy Potential in Urban Locations.  Masters thesis, Concordia University.

creator:
Ghassemi Panah, Anahita
Paraschivoiu, Marius

abstract: Wind energy plays a critical role as a safe and clean source of energy. However, the complexity of wind patterns produced by the topographical characteristics of urban environments considerably affect the performance of urban wind turbines. In order to address these effects, this study utilizes both Computational Fluid Dynamics (CFD) and meteorological data in order to simulate the wind flow in an urban area and to predict the performance of a wind turbine at specific locations on top of buildings. This thesis presents a review of vertical axis wind turbines and the desirable locations of these types of wind turbines above a building in an urban area. Numerical simulations offer a cost-effective method with an acceptable accuracy to evaluate wind turbine locations. Two test cases have been studied to illustrate the behavior of wind turbines located on the roofs of buildings. The full scale of the urban area and the computational domain are constructed, and the flow is simulated based on the STAR CCM+ ® software. The three-dimensional, steady Reynolds-Averaged Navier-Stokes equations are solved to obtain the velocity of the wind in urban areas. Meteorological data is then used to estimate the potential energy production at specific locations on the top of a building. Multiple locations are studied in terms of annual total Energy output to find out the best potential position for turbine installation. Results demonstrate a significant difference of energy output for different locations of the wind turbines on the same building. This study introduces an effective tool to study the annual total energy output potential at multiple locations above the building in much shorter time span (within a month) rather than the existing experimental or field methods.


identifier: Joyce, Megan M ORCID: https://orcid.org/0000-0003-1580-3554 <https://orcid.org/0000-0003-1580-3554>  (2021) Spatial Movement Decisions Among Foraging Japanese Monkeys (Macaca fuscata).  Masters thesis, Concordia University.

abstract: Like humans, animals routinely make decisions. These decision-making opportunities can impact an individual’s survival and reproduction. Research has shown that nonhuman primates make intentional, directional movement choices when solving spatial navigation problems in foraging. However, few studies investigate contextual factors influencing an individual’s decision-making process. Here, I investigated the influence of social (dominance rank, intraspecies competition), individual (age, sex, physical impairment), and environmental (interspecies competition) variables on route choice decision-making in a large (400+) group of free-ranging Japanese monkeys who inhabit forests around the Awajishima Monkey Center in Japan. I used a multi-destination foraging experiment with 6 feeding platforms in a (4mx8m) Z-array, which was successfully completed by 29 identifiable individuals during solitary foraging trials (N=155 successful trials). The macaques: (1) did select optimal routes, and (2) used heuristics similar to primates in other studies. Linear mixed-effects models detected relationships: (1) between age and experiment run time (juvenile macaques completed the array significantly faster than adult and young adult participants); and (2) between route length and competition (trials with competitors nearby were significantly longer than those absent of competitors). Contextual factors led to variation in Japanese macaque decision-making. Participants preferentially used what I term a sweep strategy, which promoted food acquisition in the experiment. I argue this strategy was a response to the island’s topography and intragroup competition. My research on individual variation in route choice contributes to a better overall understanding of group-level movements and the processes underlying foraging decisions, which can contribute to conservation and management.


identifier: Moini Jazani, Arman ORCID: https://orcid.org/0000-0003-2265-020X <https://orcid.org/0000-0003-2265-020X>  (2021) Development of Dual-Location Acid and Glutathione Cleavable Block Copolymers for Drug Delivery.  PhD thesis, Concordia University.

abstract:
The efficiency of chemotherapeutic drugs has been drastically compromised by their undesired side effects. Drug delivery via amphiphilic block copolymer (ABP)-based nanoassemblies has received considerable attention as a new therapeutic method to selectively deliver chemotherapeutic drugs to tumors. Nevertheless, one of the persisting challenges for this therapeutic method is the slow degradation of the nanoassemblies and the sluggish release of encapsulated drugs in the cancer cells. To circumvent this problem, a variety of cleavable linkages have been integrated in the nanoassemblies that can be degraded in response to endogenous stimuli found in tumor environments. Particularly, tumors are known to be acidic and have higher concentrations of cytosolic glutathione (GSH) compared to normal cells.
This thesis describes the investigation of novel strategies for the synthesis of dual location acid- and dual acid/GSH-degradable ABPs for intracellular drug delivery. Various ABPs were synthesized via atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer (RAFT) polymerization and concurrent ATRP/RAFT polymerization to study their structure-property relationships for effective intracellular drug delivery. These copolymers were designed to have acid-labile acetal or ketal groups and GSH-cleavable disulfide linkages at a junction of hydrophilic and hydrophobic blocks and in hydrophobic blocks. They self-assembled to spherical micelles with cleavable linkages at the hydrophobic core or the interface. The studies of acid or/and GSH-responsive degradation and disassembly revealed that the cleavage of acid- and GSH-cleavable linkages results in disassembly of nanoassemblies through the synergistic shedding of hydrophilic corona as well as the loss of the hydrophobic/hydrophilic balance of micelles core. The nanoassemblies were successfully loaded with Doxorubicin (a clinically used anti-cancer drug) and exhibited enhanced drug release in the presence of acidic or/and GSH stimuli. Promisingly, dual-location acid and acid/GSH degradable nanoassemblies showed biocompatibility, anti-cancer activity and cellular uptake in HeLa cancer cells.


identifier: Mirvalad, Seyed Javad  (2021) Durability Properties of Blended Portland Limestone Cement Containing Calcium Carbonate Nanoparticles.  PhD thesis, Concordia University.

abstract:
The use of Portland Limestone Cement (PLC) as a greener alternative to Portland Cement (PC) dates back to 1960s. In Canada, PLC was first introduced in 2008 with the limestone content limit of 15%. While the use of PLC alone in sulfate exposure is prohibited according to CSA A23.1, the limit of 15% is mainly to ensure a suitable level of mechanical and durability performance. Improving the performance of PLC and decreasing its clinker content is very appealing since it can contribute to reducing the carbon and energy footprint of cement industry. Calcium carbonate nanoparticles (NC) have been shown to be effective in accelerating cement hydration in ultra high performance concretes and concretes with high levels of supplementary cementing materials, but their effect on durability has been rarely studied.
In this research, limestone cement was made by blending micro limestone powder with general use cement at 15%, 20%, and 25% content levels. NC was used as an additive at 1%, 2%, 3%, and 4% and heat of hydration using isothermal calorimetry technic was evaluated. Based on the results of this test, 2% addition of NC was selected as the most favorable addition level and was used in mortar samples for further durability investigations. Additionally, the same mixtures were made with the addition of 2% nano silica (NS), which is a one of the most widely-used nanoparticles in cement, in order to put the efficacy of NC in perspective. Several mechanical and durability measures such as compressive strength, volume of permeable voids, sorptivity, bulk electrical conductivity, bulk electrical resistivity, and expansion due to ettringite and thaumasite sulfate attack were studied on mortar samples.
The results showed that 2% NC addition was significantly effective in improving durability of mortar samples. Also, 2% NC addition was found to be more effective than 2% NS addition in improving all of the measures except for compressive strength. Moreover, considering durability performance, it was concluded that, with the 2% NC addition, limestone content limit of 15% can be safely increased to 20% and even to 25% if sulfate resistance is not required.


identifier: Xia, Yuanjie  (2021) Reducing the Length of Field-replay Based Load Testing.  Masters thesis, Concordia University.

abstract:
With the development of software, load testing have become more and more important. Load testing can ensure the software system can provide quality service under a certain load. Therefore, one of the common challenges of load testing is to design realistic workloads that can represent the actual workload in the field. In particular, one of the most widely adopted and intuitive approaches is to directly replay the field workloads in the load testing environment, which is resource- and time-consuming.
In this work, we propose an automated approach to reduce the length of load testing that is driven by replaying the field workloads. The intuition of our approach is: if the measured performance associated with a particular system behaviour is already stable, we can skip subsequent testing of this system behaviour to reduce the length of the field workloads. In particular, our approach first clusters execution logs that are generated during the system runtime to identify similar system behaviours during the field workloads. Then, we use statistical methods to determine whether the measured performance associated with a system behaviour has been stable. We evaluate our approach on three open-source projects (i.e., OpenMRS, TeaStore, and Apache James). The results show that our approach can significantly reduce the length of field workloads while the workloads-after-reduction produced by our approach are representative of the original set of workloads. More importantly, the load testing results obtained by replaying the workloads after the reduction have high correlation and similar trend with the original set of workloads. Practitioners can leverage our approach to perform realistic field-replay based load testing while saving the needed resources and time.


identifier: Kinsley, Christine  (2021) Taking the Temperature: Associations between Sibling Relationship Warmth and Reports of Daily Interactions in Preadolescence.  Masters thesis, Concordia University.

abstract: Although most children grow up with siblings, this relationship is greatly understudied compared to other relationships in a child’s life. While much research has focused on sibling conflict, warmth is also important to understanding how to foster a positive relationship. Different positive aspects of the sibling relationship can include disclosure, teaching and learning, prosocial behaviors (e.g., comforting and helping), companionship (e.g., spending free time together) and positive emotionality. This study examined how these features, as well as negative features such as fighting and negative emotionality, in daily sibling interactions were related to warmth. Daily diaries completed by 33 preadolescent children (M = 11.5 years; 14 girls) were analyzed. Analyses assessed both between- and within-person patterns. Results indicated that positive emotionality in daily interactions was most closely related to warmth. Furthermore, on days in which siblings reported more negative interactions, they also reported fewer positive interactions. Finally, when children reported a positive behavior towards their sibling on a given day, their sibling was reported to reciprocally engage in similar types of behavior. However, warmth did not significantly moderate either (a) the link between positive and negative daily interactions or (b) daily patterns of reciprocity in the sibling relationship. The results of this study may ultimately inform interventions aimed at fostering warmth in the relationship as well as guide parents on how to help their children develop a warm and positive relationship between their children.


identifier: Xie, Yuxuan ORCID: https://orcid.org/0000-0002-9110-9874 <https://orcid.org/0000-0002-9110-9874>  (2021) Comprehensive Study of 1-bit Delta-Sigma Modulation in Digitized Radio over Fiber Fronthaul Systems.  Masters thesis, Concordia University.

abstract:
Mobile access network includes backhaul and fronthaul transmission system. To support the requirements of high capacity, low cost and low power consumption in fronthaul transmission systems, radio over fiber (RoF) technology has become the most popular solution for fronthaul transmission. Current fronthaul transmission technology is based on digitized CPRI RoF transmission (CPRI- common protocol radio interface). However, the conventional CPRI RoF leads to fronthaul systems with high complexity, and high-power consumption. To simplify, 1-bit delta-sigma modulation based digital RoF fronthaul system was proposed, in which the complexity and power consumption of the antenna tower units by moving complicated signal processing to central baseband units are reduced. When 1-bit delta-sigma modulation is used, an electrical bandpass filter is only required at the antenna tower to convert a digital signal to an analog RF signal for a downlink fronthaul.
In this thesis, comprehensive studies and comparison of three 1-bit delta-sigma modulations (DSM) in fronthaul optical transmission are given, which are two bandpass and one envelope delta-sigma modulation. The first bandpass 1-bit DSM considered (type-I) is based on a mixed-signal and a bandpass ΔΣ modulator, and the second bandpass 1-bit DSM considered (type-II) is based on all-digital signal and two low-pass ΔΣ modulators.
First, the ΔΣ modulator, i.e. the core unit of the DSM, is designed for a long-term evolution (LTE) signal of 200 MHz. In the ΔΣ modulator, the loop filter plays a significant role, and thus it is first optimized. Based on theoretical analysis, simulations and experiments, the Chebyshev-based loop filter is selected because it has a narrower transition band and wider stopband. Moreover, it is found that the order of the loop filter should be matched with input signal bandwidth.
Among the three DSMs, it is found by simulations and experiments that bandpass DSM type Ⅰ is the simplest system, and it also leads to the best optical transmission. However, the bandpass DSM type Ⅰ is the highest in the design difficulty because it uses a bandpass ΔΣ modulator. The bandpass DSM type Ⅱ is the easiest system to be implemented by hardware for its all-digital structure. However, due to a wider signal spectrum, the type-II is more sensitive to fiber dispersion, and the wider signal spectrum is induced by digital carrier.
It is found that harmonic noise can be added to the signal band in the envelope DSM when the signal is not narrow, such as 200 MHz in this thesis. Further, it is shown that this noise becomes the dominating factor in transmission performance. Therefore, the envelope DSM leads to the worst transmission performance among the three DSMs.
DSM generated NRZ is also compared to conventional NRZ. It is found that the DSM generated NRZ leads to worse transmission performance than conventional NRZ, i.e., more sensitive to fiber dispersion, which is due to the fact that the DSM generated NRZ has a larger optical spectrum. To reduce the effect of fiber dispersion, it is demonstrated that the digital up-sampling after DSM can be used to reduce the optical bit rate, and thus transmission is much less sensitive to fiber dispersion.


identifier: Refahi, Leila ORCID: https://orcid.org/0000-0003-4297-1342 <https://orcid.org/0000-0003-4297-1342>  (2021) Curriculum for Climate Justice: Transforming Environmental Knowledge through Socially Engaged Art Practices.  Masters thesis, Concordia University.

abstract: By examining the interactive tools of Socially Engaged Art (SAE) and artmaking in dialogue, this thesis explores how transformational environmental knowledge can be developed in a learning environment focused on adult education. Using Design-Based Research (DBR), with the participation of six adults from different backgrounds, I designed and carried out four sessions of educational workshops on the following themes: Environmental Indifference, Climate Change, Animals, and Environmental Justice. I designed the workshops to provide a shared space for participants to create, learn, converse, and engage freely in the research process. This research illuminates how an integrated curriculum for Art Education, using Socially engaged art methods and an environmental approach, can provide opportunities to re-direct our thinking and learning and help us to re-imagine our connections with the environment.


identifier: Aalizadeh, Mohammad Sadegh  (2021) Automatic Motivation Detection for Extract Method Refactoring Operations.  Masters thesis, Concordia University.

abstract:
Refactoring is a common maintenance practice that enables developers to improve the internal
structure of a software system without altering its external behaviour. In this study
we propose a novel method to automatically detect 11 motivations driving the application
of EXTRACT METHOD refactoring operations. We conduct a large-scale study on
325 open-source Java repositories to automatically detect the motivations of 346K EXTRACT
METHOD refactoring instances. Previous studies have been merely based on surveys,
manual analysis of pull requests or commit-messages to detect the motivations of
developers. In this study we develop motivation detection rules to automatically extract
the developer motivations based on the context of a refactoring operation in the commit.
We find that the top four motivations for EXTRACT METHOD refactoring is to introduce
reusable methods, remove duplication, facilitate the implementation of new features and
bug fixes, and decompose long methods to improve their readability. There is an association
between the removal of duplication and the introduction of reusable methods in
the refactoring instances with multiple motivations. The findings of this study provide essential
feedback and insight for the research community, refactoring recommendation tool
builders, and project managers, to better understand why and how developers perform EXTRACT
METHOD refactorings and help them build refactoring tools tailored to the needs
and practices of developers.


identifier: Nikbakht, Elaheh  (2021) Investigating long-term short pairing strategies for leveraged exchange-traded funds using machine learning techniques.  Masters thesis, Concordia University.

abstract: Although the literature on leveraged exchange-traded funds (LETFs) concurs with the idea that they are short-term investment tools, recent studies offer some investment strategies for them that are also profitable in the long term. These strategies, however, are typically only tested on a limited number of highly traded LETFs. This study uses different types of LETFs to examine various portfolios with different combinations of bull and bear LETFs, to find the best investment strategy in the long run. It then uses different machine learning techniques to analyze which factors define the best investment strategies, with portfolios being rebalanced on a quarterly and annual basis. The sample of this study consists of 44 pairs of LETFs from 2012 to 2020 that have different underlying assets and leverage levels. The results reveal that short-selling the combination of both bull and bear LETFs does not yield a significant positive return compared to the market, however, the return generated from short-selling a portfolio with only bear ETFs can significantly beat the market, especially when the market is bullish. The quarterly and annual results are consistent and show that short-selling a full bear portfolio is the winning strategy in both of these intervals. Moreover, the results show that as the correlation of LETFs with their underlying index increases, the return of short-selling both bull and bear LETFs decreases. At the same time, an increase in the net asset value of bull LETFs results in an increase in the return of short-selling bull LETFs and a decrease in return of short-selling the bear LETFs.


identifier: Mulvihill, Kathryn  (2021) A Self-Determination Theory Perspective on Wellbeing in the Transition from University: Trait Autonomy and Basic Psychological Need Satisfaction through Graduates’ Goal Pursuits, Past and Present.  PhD thesis, Concordia University.

abstract: This research aims to identify determinants of wellbeing in the transition from university, a challenging lifespan transition with long-term implications for adult development. We applied self-determination theory, a theory of motivation, wellbeing, and optimal development, to propose an integrative model of wellbeing during this transition. This model predicts that trajectories of wellbeing should reflect the extent to which social environments encountered during the transition support vs. thwart graduates’ basic psychological needs, the extent to which graduates’ dispositional tendencies catalyze processes that facilitate vs. undermine need satisfaction, and the extent to which need-relevant qualities of social environments and graduates’ need-relevant dispositional tendencies influence one another across the transition. We tested this model by investigating whether trait autonomy, a dispositional factor associated with need satisfaction and wellbeing within SDT, promotes graduates’ wellbeing by facilitating need satisfaction though goal pursuits, past and present. We examined this overarching hypothesis across two analyses of longitudinal data collected from graduates transitioning from a large, public university in Québec. Study 1 investigated whether trait autonomy promotes wellbeing by catalyzing need-satisfying processes of striving for post-graduation goals. Results confirmed that higher levels of trait autonomy predicted more self-concordant striving processes and, through them, increases in graduates’ life satisfaction across the transition from university. Study 2 investigated whether trait autonomy might also promote wellbeing by providing graduates with need-satisfying memories of past striving. We tested this hypothesis in relation to a single memory – that of facing an unattainable goal while in university – and two distinct, but conceptually related memory pathways – (i) need satisfaction associated with unconscious activation of episodic memories and (ii) need-satisfying themes of growth in narratives consciously constructed from these memories. The results confirmed our hypothesis, but mainly through the first memory pathway, raising theoretical and methodological issues for future research. Together, findings constitute the first empirical evidence for an integrative, SDT-based model of wellbeing in the transition from university, make theoretical contributions to SDT and other frameworks (i.e., the self-concordance model, the theory of episodic memory need satisfaction, and the theory of narrative identity), raise intriguing questions for future research, and identify promising approaches to intervention to support the wellbeing of graduates during this key transition.


identifier: Bansal, Sunanda ORCID: https://orcid.org/0000-0002-4367-6778 <https://orcid.org/0000-0002-4367-6778>  (2021) Vector Representation of Documents using Word Clusters.  Masters thesis, Concordia University.

abstract: For processing the textual data using statistical methods like Machine Learning (ML), the data often needs to be represented in the form of a vector. With the dawn of the internet, the amount of textual data has exploded, and, partly owing to its size, most of this data is unlabeled. Therefore, often for sorting and analyzing text documents, the documents have to be represented in an unsupervised way, i.e. with no prior knowledge of expected output or labels. Most of the existing unsupervised methodologies do not factor in the similarity between words, and if they do, it can be further improved upon. This thesis discusses Word Cluster based Document Embedding (WcDe) where the documents are represented in terms of clusters of similar words and, compares its performance in representing documents at two levels of topical similarity - general and specific. This thesis shows that WcDe outperforms existing unsupervised representation methodologies at both levels of topical similarity. Furthermore, this thesis analyzes variations of WcDe with respect to its components and discusses the combination of components that consistently performs well across both topical levels. Finally, this thesis analyses the document vector generated by WcDe on two fronts, i.e. whether it captures the similarity of documents within a class, and whether it captures the dissimilarity of documents belonging to different classes. The analysis shows that Word Cluster based Document Embedding is able to encode both aspects of document representation very well and on both of the topical levels.


identifier: Roy, Mithun  (2021) Harmonic states in quantum cascade lasers: Frequency-domain analysis and mode-spacing control.  Masters thesis, Concordia University.

abstract:
Quantum cascade lasers (QCLs) are unipolar lasers where lasing transition and carrier transport occur between subbands that result from multiple nanometer-thick quantum wells and barriers formed by the conduction band edges of a semiconductor heterostructure. Since their inception in 1994, QCLs have undergone tremendous improvements with respect to output power, frequency range covered, and maximum operating temperature. As a result, they have become a prominent source of light emitting in the mid- and far-infrared regions of the electromagnetic spectrum.

Multimode behavior of QCLs was a focus of many past works. In a recent comprehensive study, it was found that, if the pumping is increased gradually from threshold, QCLs enter into a harmonic state regime, which is characterized by the lasing of side modes that are separated from each other by multiples of free spectral range (FSR). With a further increase in the pumping, finally, transition into the familiar single-FSR-spaced regime (dense state regime) occurs. Unlike the dense state regime, the harmonic state regime of QCLs has not gone through intense scrutiny, as it is a relatively recent discovery.

In this thesis, a theoretical investigation into the harmonic state regime of QCLs is performed. The work is based on Maxwell’s equation and the density matrix (DM) formalism. The two-level DM equations, although commonly employed, ignore many important details of complex carrier transport through a QCL structure. Therefore, here, a three-level DM formalism is employed, which takes into account phenomena such as resonant tunneling and carrier scattering between the three states.

The thesis is mainly divided into two parts. In the first part, starting from the DM-Maxwell equations, an analytical expression for the instability gain of the side modes is derived. This expression can explain the appearance of harmonic states in QCLs. Using this analytical expression, the effects of group velocity dispersion on the harmonic states are studied. In the second part, multimode behavior of QCLs is analyzed using a more general model than that used in the first part. In particular, openness (non-unity facet reflectivity) of the cavity is considered, which was not taken into account in previous works that used the modal expansion method to study QCLs. Using the theory, it is shown that the coating of a facet can be used to excite harmonic states with different mode spacing. Such a control over the generation of harmonic states could make QCLs invaluable for applications such as microwave and terahertz generation, picosecond pulse generation in the mid-infrared frequency range, and broadband spectroscopy.


identifier: Bavand, Amir Hossein  (2021) The Impact of Parallel and Batch Testing in Continuous Integration Environments.  Masters thesis, Concordia University.

abstract:
Testing is a costly, time-consuming, and challenging part of modern software development. During continuous integration, after submitting each change, it is tested automatically to ensure that it does not break the system’s functionality. A common approach to reducing the number of test case executions is to batch changes together for testing. For example, given four changes to test, if we group them in a batch and they pass we use one execution to test all four changes. However, if they fail, additional executions are required to find the culprit change that is responsible for the failure.
In this study we first investigate the impact of batch testing in the level of the builds. We evaluate five batch culprit finding approaches: Dorfman, double pool testing, BatchBisect, BatchStop4, and our novel BatchDivide4.
All prior works on batching use a constant batch size. In this work, we propose a dynamic batch size technique based on the weighted historical failure rate of the project.
We simulate each of the batching strategies across 12 large projects on Travis with varying failures rate. We find that dynamic batching coupled with BatchDivide4 outperforms the other approaches. Compared to TestAll, this approach decreases the number of executions by 47.49% on average across the Travis projects. It outperforms the current state-of-the-art constant batch size approach, i.e. Batch4 by 5.17 percentage points.
Our historical weighting approach leads us to a metric that describes the number of consecutive build failures. We find that the correlation between batch savings and FailureSpread is r = −0.97 with a p ≪ 0.0001. This metric easily allows developers to determine the potential of batching on their project.
However, we then show that in the case of failure of a batch, re-running all the test cases is inefficient. Also, for companies with notable resource constraints, e.g., Ericsson, running all the tests in a single machine is not possible and realistic. To address this issues we extend our work to an industrial application at Ericsson.
We first evaluate the effect of parallel testing for a project at Ericsson. We find that the re- lationship between the number of available machines for parallelization and the FeedbackTime is nonlinear. For example, we can increase the number of machines by 25% and reduce the Feedback- Time by 53%.
We then examine three batching strategies in the test level: ConstantBatching, TestDynamic- Batching, and TestCaseBatching. We evaluate their performance by varying the number of parallel machines. For ConstantBatching, we experiment with batch sizes from 2 to 32. The majority of the saving is achieved using batch sizes smaller than 8. However, ConstantBatching increases the feedback time if there are more than 6 parallel machines available. To solve this problem, we pro- pose TestDynamicBatching which batches all of the queued changes whenever there are resources available. Compared to TestAll TestDynamicBatching reduces the AvgFeedback time and AvgCPU time between 15.78% and 80.38%, and 3.13% and 48.78% depending on the number of machines. Batching all the changes in the queue can increase the test scope. To address this issue we propose TestCaseBatching which performs batching at the test level instead of the change level. Using Test- CaseBatching will reduce the AvgFeedback time and AvgCPU time between 19.84% and 84.20%, and 5.65% and 50.92% respectively, depending on the number of available machines for parallel testing. TestCaseBatching is highly effective and we hope other companies will adopt it.


identifier: Jia, Wenjun  (2021) Investigating neurocognition in design creativity under loosely controlled experiments supported by EEG microstate analysis.  PhD thesis, Concordia University.

abstract: Design is a recursive process to create original and useful artifacts to meet human needs. Creativity is a critical ability for designers to create original and useful artifacts. Design creativity focuses on creativity mechanisms during the design process. Even though many studies endeavor to understand cognition in design creativity by protocol analysis, neurocognitive underlying design creativity remains unknown. Such scarcity can be explained by the intrinsic characteristics of the design process and the data analysis approaches. Loosely controlled experiments are capable of simulating the intrinsic characteristics of the design process, whereas they would increase difficulties of data analysis due to unstructured data and hidden causal relationships between a stimulus and its response. Therefore, this research aims to: (i) test the effectiveness of loosely controlled experiments through comparing its findings on phenomena that have been effectively studied by validated experimental research; (ii) structure and segment unstructured electroencephalography (EEG) signals through EEG microstate analysis; (iii) identify EEG-defined large scale brain networks and uncover their temporal dynamics in design creativity; (iv) capture the temporal dynamics of EEG defined large-scale brain networks to classify different cognitive activities in design creativity through RNN techniques under the autoencoder framework. The loosely controlled experiments supported by EEG microstate analysis appear to offer an effective approach to facilitating an ecologically valid neurocognitive study.


identifier: Kumar, Priya  (2021) The Kids are (M)all Right: Youth Culture and Shopping Centers in Late Twentieth Century America.  Masters thesis, Concordia University.

abstract: This thesis explores the era in which shopping centers reached the zenith of its growth and pop cultural relevancy in the United States in the late twentieth century. By tracing the shopping center from its inception as an enclosure that served the needs of the developing and sprawling suburbs to the entertainment complexes that came to define them in the late twentieth century, it can be argued that malls turned away from serving their communities in favor of promoting a type of conspicuous consumption. This thesis also explores the parallel rise of the so-called “teenager,” a demographic that was named to complement the commercial culture that came to define them. This thesis focuses on self-described mallrats in the late twentieth century, and particularly how the two phenomena—mall culture and youth culture—dovetailed under an increasingly deregulated neoliberal regime. This thesis, therefore, delves into the implications of a generation that came of age within the windowless walls of the shopping mall.


identifier: Whatley, Justin  (2021) Fault Analysis Using Learning Models with Model Interpretation.  Masters thesis, Concordia University.

abstract:
As machine learning moves from theoretical applications in academia to promising solutions to problems across industry and healthcare, effective interpretability strategies are critically impor- tant to adoption. However, model interpretability strategies can be extended to offer more than validation for the predictions a model is making. Learned models offer a proxy for the data by capturing relationships between feature inputs and target outcomes, offering a representation that can be analysed. To that end, this work describes a fault analysis system that leverages learned models to characterize faults by using SHapley Additive exPlanations (SHAP).
In particular, this fault analysis system was designed for large structured datasets such as those available in telecommunications networks. The strategy works by forming a learned representation with tree-based models using gradient-boosting. Once a problematic sample is selected for analysis, the computationally efficient implementation of the SHAP algorithm specialized for tree-based models is employed to gauge feature contributions to the performance degradation observed in the sample. Thus, this fault analysis strategy effectively provides an explanation for the degradation in a problematic sample informed through a model-based representation of the relevance of input characteristics across contexts. An evaluation of the strategy is performed, demonstrating its reliability for structured communications data using a 4G LTE dataset.


identifier: Shields-Rivard, Sara  (2021) Queer Interwar Design: Eyre de Lanux and her Sapphic Spaces.  Masters thesis, Concordia University.

abstract: This thesis examines the designed interiors of Elizabeth Eyre de Lanux (1984-1996), an American writer, artist, and designer expatriated in Paris during the interwar period. Active primarily from 1928 to 1932, she designed her interiors collaboratively with her romantic partner, the British textile designer Evelyn Wyld (1882-1973). This thesis looks to interior design history, queer studies, and decolonial theories within the decorative arts to frame the analysis of de Lanux’s work and, when relevant, her life. This thesis posits that she designed hybrid spaces—rooted in Art Deco, gleaning from Modernism—as a reflection of her own hybrid identity, as a queer woman engaged in female masculinity, same-sex intimacies, and polyamories. The first section explores de Lanux’s gendered, sexual, and stylistic hybridities in her early collaborative interior displays with Wyld, exhibited at various Parisian Salon exhibitions, positioning them as imagined spaces for the modern queer/sapphic woman. Serving as blueprints for her designed modern Parisian dwellings, her displayed interiors prompt the study of the pied-à-terre apartments designed for queer, single, or widowed women, serving as the second and final chapter of this thesis. While these interiors remain decorative in nature, they demonstrate an engagement with, and subversion of, modernist sight, while also employing a kind of queer performance of identity, navigating queer in/visibility of space.  The visual and material analysis of her designed attempts to create for the modern queer/sapphic woman—both as imagined spaces on display and subsequent inhabited apartments—allow for creative interventions into the understanding of modernism and identity politics in interwar Paris.


identifier: Xian, Zixiang  (2021) Generative Models Based on the Bounded Asymmetric Gaussian Distribution.  Masters thesis, Concordia University.

abstract:
The bounded asymmetric Gaussian mixture model (BAGMM) has proved that it generally performs better than the classical Gaussian mixture model. In this thesis, we investigate the learning of the BAGMM. Indeed, we propose an Expectation-Maximization (EM) algorithm to estimate the model parameters. A model selection criterion for BAGMM using minimum message length (MML) is proposed to determine the optimal number of clusters. The MML is shown to perform better than other model selection criteria.
In this thesis, we additionally propose an unsupervised feature selection framework using BAGMM to determine the structure of high dimensional data without knowing in advance the number of clusters nor the importance of the involved features. The validation for this framework involves several human-related recognition challenges, such as human activity categorization and human gender recognition.
Finally, we integrate the BAGMM into a hidden Markov model (HMM) framework, which uses BAGMM to model the emission probability distribution. The BAGMM-based HMM is evaluated with several real-world applications and compared with other Gaussian mixture-based HMMs.


identifier: Villeneuve, Gabriel  (2021) Écrire sans marquer : Traduire The Cook and the Carpenter de June Arnold en français.  Masters thesis, Concordia University.

abstract: Ce mémoire de maîtrise est une traduction commentée du roman de 1973 The Cook and the Carpenter de June Arnold. Le projet est ancré dans une approche féministe et dans l’apport théorique traductologique de Henri Meschonnic puisqu’il est question de respecter le rythme de l’œuvre dans la langue source tout en surmontant les difficultés que pose la création d’une système grammatical original non genré. Les contextes dans lesquels s’inscrivent la publication du roman et sa traduction sont d’abord explorés. Ensuite, les valeurs du texte qui composent son rythme sont analysées afin d’en faire émerger une méthode de traduction adaptée au roman, et les stratégies de traduction y sont énumérées en détail. Le projet cherche à explorer les possibles du français pour y découvrir une voie permettant à des personnages littéraires d’exister et de prendre la parole sans avoir à divulguer leur genre ou leur sexe, tout en faisant, plus généralement, à la langue cible ce que le texte fait à la langue source.


identifier: Shaw, Michael  (2021) I Can Feel My Teeth.  Masters thesis, Concordia University.

title: I Can Feel My Teeth

abstract: I Can Feel My Teeth is a collection of semi-autobiographical poems exploring the different forms discomfort and denial may take. The title refers to an observation I have continuously made throughout my life that the only times you can feel your teeth are when you, body or mind, are unwell. My poems utilize nature imagery and animal comparisons in unusual ways to further deepen the speaker’s denial. If animals are part of nature, then surely the speaker’s pain is natural as well. Scattered throughout the collection are references to the speaker’s motherland, a place infested with memories and vermin, which serve to heighten the isolation felt in the other poems. The speaker has no outlet for this discomfort, and as a result turns inward towards their work, further distancing themselves from society. I Can Feel My Teeth has no happy ending, because there is nothing in the speaker’s future except for more of the same, reflecting the tedium of life in quarantine. It’s not all bad though. In the poem’s own words, “Don’t the continents look happy?”


identifier: Abd El Malek, Christine  (2021) Mass spectrometric identification and quantification of mitochondrial proteins that are enriched or depleted in budding yeast lacking Tor1, a protein that accelerate chronological aging.  Masters thesis, Concordia University.

abstract: The study of aging captured the interest of many researchers as the accumulation of old cells appeared to be linked to several chronic age-related diseases. Despite the complexity of the aging process, the pathways underlying cellular aging were revealed with the help of molecular analyses using the budding yeast Saccharomyces cerevisiae. This model is a unicellular eukaryote that is intensively used in aging research as its mechanisms are evolutionarily conserved across phyla. Our laboratory focused on one of those pathways, namely target of rapamycin type 1 (TOR1) signal transduction network that regulates cell growth in response to the availability of nutrients and growth factors. As such, the TOR1 signaling network activates several pro-aging processes and inhibits some anti-aging processes. Genetic, dietary, or pharmacological manipulations suppressing TOR1 activity have been shown to extend the lifespan. Thus, the single-gene deletion mutant tor1Δ has been used to investigate the mitochondrial proteome using non-caloric restriction. Mitochondrial functionality is vital as their decline is a hallmark of cellular aging in evolutionarily distant eukaryotes. Mitochondria synthesize the bulk of cellular ATP by harboring pathways that link the tricarboxylic acid cycle and oxidative phosphorylation. Mitochondrial fusion and fission are essential contributors to mitochondrial functionality maintenance because they regulate the age-related changes in mitochondria assembly and biogenesis. Mass spectrometry was used to identify and quantify the purified mitochondrial proteins from differently aged control wild-type and tor1Δ mutant strains of budding yeast that were upregulated or downregulated. These findings suggest that some of the mitochondrial proteins in the tor1Δ mutant strain are upregulated and could contribute to the mechanism that extends lifespan in yeast cells.


identifier: Wen, Min  (2021) Towards Adaptive Federated Semi-Supervised Learning for Visual Recognition.  Masters thesis, Concordia University.

abstract:
Internet of Things (IoT) devices such as smart phones and wireless sensors have proliferated in smart cities over the past few years. Various applications, including augmented reality, autonomous driving and smart homes, are based on the effective use of data generated by IoT devices. However, two main issues constrain the development of IoT applications. The first issue originates from the data distribution, which is usually isolated and not easy to be centralized due, in large part, to privacy concerns. The second issue arises from the shortage of labeled data, as the labeling process is costly, time-consuming and often requires input from domain experts. More recently, federated semi-supervised learning has become a viable solution to mitigate these issues by collaboratively training a machine learning model using decentralized labeled and unlabeled data. It also brings extensibility and generalizability without privacy infringement compared to traditional centralized training. However, the federated learning process is quite challenging due to data heterogeneity among clients. The contributions in this thesis are two-fold. First, we present an adaptive federated semi-supervised learning framework, which seamlessly integrates adaptive optimizers on both server and client sides in an effort to promote system adaptability. Experiments and ablations studies conducted on four standard benchmark datasets demonstrate the effectiveness of our proposed approach in image classification, achieving superior performance over strong baseline methods.
The other contribution consists of designing a two-stage human activity recognition system, which also incorporates adaptive optimizers into both local and global training. Clients train a local autoencoder model with a learning rate adaptive to local gradients, while the central orchestration server updates the global autoencoder model by applying a gradient-based adaptive optimizer to the average of clients’ model updates. Our system leverages a large amount of unlabeled data on clients with the aim of achieving a higher classification accuracy. The key benefit of adaptive optimizers is their ability to improve local training, while stabilizing the global aggregation in a bid to guarantee a proper optimization. We demonstrate through experiments that the proposed framework is robust to non-independent and identically distributed data and yields a stable convergence rate in different settings.


identifier: Gaudissart, Albane  (2021) Passing through Maasailand. Encountering Maasai Youth and the navigation of boundaries and identity politics.  Masters thesis, Concordia University.

abstract: Engaresero, located on Maasailand in Northern Tanzania, has been in the last few years a good example of the rapid increase of global connectivity and the emergent possibilities arising from being connected to varied social geographies simultaneously. Based on ethnographic research in Engaresero, this thesis examines the engagements of Maasai youth in these varied social geographies. Whether it is the local pastoral rhythm and social order, the national education system or tourism activities, these competing systems each hold their set of expectations and opportunities. By looking at hairstyles, mobile phone usage, vernacular expressions and the creation of ethnographic content for tourists, this paper describes the heterogeneous trajectories emerging from these superimposed systems and structures of authorities. Maasai youth has developed numerous strategies to align expectations with their own aspirations. Their skillful navigation involves intergenerational dialogues that leads to the indigenization of modernity, and boundary work, which enables sustaining competing authorities in order to maintain harmonious relationships. This future-making process of new generations shows fluidity and self-reflexivity and this thesis suggests that it is also historically contingent to the ongoing pressures over the pastoralist lifestyle, land and the idea of being Maasai. The historical plight of oppressive colonial and other dominant powers have shaped this capacity to negotiate competing authorities, and this includes anthropological theories and representations. Reflecting on positionality and land struggles, this thesis questions the anthropological tendency to critique notions, such as “Maasai culture,” at the risk of diminishing the local discourse and commitment to cultural reproduction. Instead, it proposes adopting a similar fluidity in anthropological considerations of cultural representation in order to take seriously the everyday struggles to maintain self-determination in Maasailand.


identifier: Johnsen, Ingvild  (2021) Sarah Koenig and Serial: What Does the Dramatized Narrator Bring to Podcast Storytelling?  Masters thesis, Concordia University.

abstract: This thesis explores the various narrative strategies used by the dramatized narrator of Sarah Koenig in the podcast series Serial. It views these strategies through the lens of journalistic professionalism and ethical guidelines; standards built on ideas of neutrality, balance, fairness and objectivity. Koenig's personal and confessional voice illustrates the potentially intimate nature of the podcast medium, and challenges traditional conceptions of what journalism is and what it should be. The series' mainstream success further amplifies these questions, as journalism is facing existential threats in a digital world where access to information is plentiful and its distribution democratized. Using narratological terms, this thesis describes how Koenig's dramatized narrator is used to communicate ambiguity, convey transparent subjectivity, encourage audience engagement, and uses journalistic storytelling as a humanizing process. These aspects not only result in a powerful form of storytelling, but also provide future professionals with an alternative approach to journalism in an age where objectivity has become a fraught ideal.


identifier: Muhialdin, Hamed  (2021) Behavioral Newsvendors and Random Demand.  Masters thesis, Concordia University.

abstract:
Previous studies on laboratory newsvendor problem observed the pull-to-center (PTC) effect, that decision makers tend to concentrate their orders around average demand and fail to optimize the expected profit. However, existing experiments in this context have been limited to random demand with uniform distributions. This study examines the robustness of the PTC effect under a boarder range of demand distributions and estimates whether some reference-point based models may explain the observed behavior of the decision makers.

This study is based on three sessions of newsvendor experiments with performance-based compensation. In each session, subjects are provided with a uniform, normal, or fat-tail demand distribution and two profit scenarios. For each profit scenario, subjects place their order quantities before running a computer simulation that determines the actual demand and their realized profits. Parallelly, simulation behavioral data can be generated based on five different reference-point based models with a wide spectrum of risk and loss aversion parameters.

The study provides statistical comparisons between the experimental data and simulation data from reference-point based models which concludes that in terms of measure of errors, the stochastic mean model performs the best in the low-profit scenario across all three demand distributions, whereas the status quo and participation payout models perform the best in the high-profit scenario when demand follows a uniform distribution. Moreover, the statistics show that the security-based model performs the best in the high-profit scenario when demand follows a normal distribution whereas the participation payout model performs best in the high-profit scenario when demand follows a fat-tail distribution. This study also discusses how demand distribution can affect the newsvendor decision behavior.


identifier: Karbasian, Hamidreza ORCID: https://orcid.org/0000-0003-3067-4359 <https://orcid.org/0000-0003-3067-4359>  (2021) Aerodynamic optimization using high-fidelity computational fluid dynamics.  PhD thesis, Concordia University.

abstract: In this study, we demonstrate the ability to perform large-scale PDE-constrained optimizations using Large Eddy Simulation (LES). We first outline the challenges associated with performing gradient-based optimization using LES, specifically chaotic divergence of the sensitivity functions. We then demonstrate that shape optimization using LES and Mesh Adaptive Direct Search Method (MADS) is feasible for aerodynamic design. Next, we introduce a Dynamic Polynomial Approximation (DPA) procedure, which allows the high-order solution polynomial representation used by the flow solver to be increased, or decreased, depending on the poll size being used by MADS. This allows rapid convergence towards the optimal design space using lower-fidelity simulations, followed by an automatic transition to higher-fidelity simulations when close to the optimal design point. Additionally, this study proposes a new physics-constrained data-driven approach for sensitivity analysis and uncertainty quantification of large-scale chaotic dynamical systems. Unlike conventional sensitivity analysis, the proposed approach can manipulate the unsteady sensitivity function (i.e., tangent) for PDE-constrained optimizations. In this new approach, high-dimensional governing equations from physical space are transformed into an unphysical space (i.e., Hilbert space) to develop a closure model in the form of a Reduced-Order Model (ROM). Afterward, a new data sampling approach is proposed to build a data-driven approach for this framework. To compute sensitivities, Least-Squares Shadowing (LSS) minimization is applied to the ROM. It is shown that the proposed approach can capture sensitivities for large-scale chaotic dynamical systems, where Finite Difference (FD) approximations fail. Therefore, we expect that implementing the proposed optimization approach can be applied to large-scale chaotic problems, such as turbulent flows, and this approach significantly reduces computational cost and data storage requirements.


identifier: Aubry, Anthony  (2021) High-Fidelity Gradient-Free Optimization of Low Pressure Turbine Cascades.  Masters thesis, Concordia University.

abstract: This study explores aerodynamic shape optimization of Low Pressure Turbine (LPT) blades using Implicit Large Eddy Simulation (ILES) coupled with the Mesh Adaptive Direct Search (MADS) optimization algorithm. Aerodynamic shape optimization in the aerospace industry relies heavily on the adjoint method combined with steady-state Computational Fluid Dynamics (CFD) solvers, namely the Reynolds-Averaged Navier-Stokes (RANS) approach. While this methodology has proven quite useful and efficient for common optimization problem, its effectiveness is reduced when faced with separated turbulent flow. As LPT designs move increasingly towards high lift configurations to reduce engine weight, accurately predicting transition and turbulent separation for each optimization cycles becomes a necessity. The T106D blade with an exit Mach number of 0.4 and Reynolds number 80,000 is used as the initial conditions before optimization, because of the presence of turbulent transition and separation on the Suction Surface (SS). First, the ILES framework employing the Flux Reconstruction (FR) approach is presented along with the benefits of its implementation on modern many-core hardware, specifically Graphical Processing Units (GPUs). The formulation of the MADS algorithm is then presented and compared against gradient-based methods and other gradient-free methods. A Bézier curve is used to modify the original blade camber line, with the use of 4 control points, permitting a wide range of shapes to be obtained. Then, the results of the baseline case are presented with a comparison with experimental results to validate the methodology selected. The results of optimization cycles using two different objective functions are then presented and compared with the original blade. Results demonstrate that a total pressure loss coefficient reduction of about 16% was achieved in the first optimization, while a tangential force increase of more than 29% was achieved with the second optimization. Finally, recommendations are made as to how this methodology could be successfully applied in industrial applications, and what future research should focus on.


identifier: Nikeghbali, Ali  (2021) Estimation of Mobile Crane Cycle Time to Improve the Accuracy of Modular-Based Heavy Construction Project Schedules.  Masters thesis, Concordia University.

abstract:
Abstract
Estimation of Mobile Crane Cycle Time to Improve the Accuracy of Modular-Based Heavy Construction Project Schedules

Ali Nikeghbali
Modular-based construction projects rely heavily on mobile cranes for lifting large quantities of materials. In recent years, these materials have become heavier and larger, and construction site layouts have become more and more congested; these factors significantly impact efficiency and productivity. In practice, on these large sites today, lift planning takes place using an intuitive approach which increases project cost and decreases productivity. A lack of comprehensive methods to identify influential factors on crane motion speeds and motion types leads to difficulties in evaluating the accurate work cycle of cranes. Therefore, addressing mobile crane cycle times during operations is critical to enhancing productivity and rapid reaction in projects. In order to improve mobile cranes’ cycle time project, the ability to accurately estimate the work cycle of mobile cranes is necessary. To address this need, this thesis proposes a methodology that involves five procedures: (i) model initiation to build up safety factor (SFs) and clearance functions; (ii) a lift analysis to study wind parameters and its effect on module shape, weight, and dimension; (iii) development of wind function; (iv) a model expansion to build up crane motion speeds function, and implementation of fuzzy if-then and inference system ; (v) time computation to estimate the crane cycle time. The proposed framework is proven effective by six case studies conducted on a large, congested industrial site. Accuracy in the case study’s project for mobile crane estimation of cycle time were increased.


identifier: Nachabe, Jude  (2021) Sleep quality during the COVID-19 pandemic and High frequency- heart rate variability as a moderator: A longitudinal study.  Masters thesis, Concordia University.

abstract: A growing body of literature describes the effect of the confinement during the COVID-19 pandemic on sleep quality and duration. Sleep quality seems to be worsening during the confinement for vulnerable individuals, but seems to be improving for others with less rigid school and work schedules. High frequency heart rate variability (HF-HRV) has been conceptualized as a biomarker of vulnerability to stress-related sleep disturbances. The goal of this study was to investigate the effect the confinement on sleep quality, sleep efficiency, and sleep duration and to investigate HF-HRV as an individual difference in sleep reactivity to confinement. One hundred and fifty participants (Mage = 50.62, SD = 6.0) completed the Pittsburg Sleep Quality Index (PSQI) at the beginning of the confinement, about a month later, and at the end of confinement period of the first wave of the COVID-19 pandemic in Montreal, Canada. HF-HRV was collected few years prior to the onset of the pandemic. Results from hierarchical linear models demonstrated a curvilinear effect for sleep duration and sleep quality with poorer sleep quality and less sleep duration a month into confinement compared to the beginning of the confinement, followed by improved sleep quality and greater sleep duration during the deconfinement period; whereas sleep efficiency linearly decreased over time. Financial stress predicted between-person differences in PSQI scores at the beginning of the confinement, but HF-HRV did not predict within-person changes in PSQI scores. These results highlight the importance of providing sleep interventions to individuals and families affected by the pandemic.


identifier: Lécuyer, Élissya  (2021) The Shade of You.  Masters thesis, Concordia University.

title: The Shade of You

abstract: The Shade of You brings together two strangers when Indigo, a 23-year-old woman, falls upon a journal belonging to someone she only knows as “E.F.”. Passionate about stationery, Indigo first finds herself drawn to this small notebook because of her curiosity for the object itself, filled with this stranger’s handwriting written in a light lavender ink. As Indigo flips through its pages, her admiration for the visual images of words themselves leads to her need to read them. This is when she will witness the grief of an older sibling after the death of Sophie, the journal writer’s 16-year-old sister. With an intertwining storyline comprised of E.F.’s journal entries and Indigo’s present life, the journal becomes a door for Indigo into the realities of trauma and suicide as an older sister herself. Inspired by the works of Ocean Vuong and Ruth Ozeki and their respective take on grief and time, this story and its alternating narratives will bring to the surface a parallel between living and writing trauma, and reading it.


identifier: Ismail-Allouche, Zeina  (2021) “ineradicable voices; narratives toward rerooting” An oral history research-creation based on the life stories of individuals who experienced transracial/intercountry adoption.  PhD thesis, Concordia University.

abstract:
“ineradicable voices; narratives toward rerooting ”; An oral history research-creation based on the life stories of individuals who experienced transracial/intercountry adoption
Zeina Ismail-Allouche, PHD
Concordia University, 2021

This collaborative oral history research-creation, grounded in Indigenous methodologies (Kovach, 2009; 2010; Smith, 1999; Wilson, 2008), amplifies the critical narrative of transracial/intercountry adoption through the life stories of individuals who experienced transracial/intercountry adoption (adoptees), regardless of their places of origin and adoption. An Advisory committee of adoptees guided the research and 22 collaborators (including the Advisory committee) worked together to ensure a co-authored representation of these long-silenced voices. The creative outcome was a Zoom oral history headphone verbatim performance.
The online public event (available at this link: https://storytelling.concordia.ca/projects-item/ineradicable-voices-narrations-toward-rerooting/) revealed complex, intimate, intense and unique pathways with intersections of colonial systems, identity formation, and enduring racism. Search for origins was perceived as necessary for the healing process and Indigenous custom adoption was identified as the best community-based practice in parallel with investing in preventing separation and breaking the vicious cycle of poverty.
The research-creation is timely amidst the tragic discovery of the remains of more than 1000 children buried at different sites of the colonial residential school following the 15 May 2021 release of the Laurent Commission final report on Children's Rights and Youth Protection calling for reform of the youth protection system in Quebec.  Internationally, the implications of the ongoing COVID-19 pandemic is expected to expose more children to the risk of falling into transracial/intercountry adoption; some 150 million people across the globe will be pushed into poverty by 2021 due to the global recession and the closure of many firms because of the lockdown (World Bank, 2021). Lebanon is of particular concern because of the country's unprecedented economic and political crises. History has proven that transracial/intercountry adoption was practiced as a rescue intervention despite the fact that it has been critically revisited in many writings highlighting its long-term and irreversible psychological challenges (Blackstock, 2011; Brodzinsky, 1993; Cantwell, 2014).
The thesis is a complementary document to the public event. It presents the theoretical framework of the research-creation. The thesis includes my connections to the research subject, a historical perspective on adoption practices and the colonial legacies of forced separation of Indigenous children in Canada, the research methodologies, the impact on audience, my learnings about the methodologies, an analysis of findings and proposed recommendations.


identifier: Buitrago, Mauricio  (2021) Intricacies of Modeling and Analysis of DC Characteristics of Single- and Multi-Channel Laterally-Gated AlGaN/GaN Heterojunction Field Effect Transistors.  Masters thesis, Concordia University.

abstract:
The present thesis offers a detailed description about the modeling of single- and multi-channel laterally-gated AlGaN/GaN heterojunction field effect transistors (HFETs) through device investigation in the Comsol Multiphysics® simulation environment. After two decades of research, studying GaN HFETs continues to be a very interesting area of investigation. This is because of the interest in using these devices in high frequency applications as well as low frequency power management. Laterally-gated GaN HFETs have recently drawn the attention of semiconductor devices engineers that search for obtaining higher current densities, higher linearity, better stability at higher frequencies, and better power management while increasing packing density.
The presented simulations offer an in-depth analysis of the observations made at thermal equilibrium and the results obtained for the DC characteristics of these devices, along with the comparison of these characteristics with those of the top-gated varieties. These observations demonstrate the improved effectiveness of lateral gating in controlling multiple vertically stacked 2DEG channels. Although there is improvement on several parameters like current density, linearity, and ON resistance (Ron), as the number of channels increases, simulations demonstrate a certain degree of degradation of drain-induced barrier lowering (DIBL) and knee voltage (Vknee). For these simulations, the devices’ self-heating at higher current densities was not considered. Also, the ohmic contacts were assumed to be ideal.


identifier: Cai, Zhengchen  (2021) Personalized Functional Near Infra-Red Optical Tomography to Investigate the Hemodynamic Correlates of Fluctuations in Neuronal Excitability.  PhD thesis, Concordia University.

abstract:
The relationship between cortical excitability and hemodynamic activity has been demonstrated in animal studies. However, it is poorly reproduced and understood in humans, limited by the requirement of simultaneous measurements of excitability and hemodynamic activity. Transcranial Magnetic Stimulation (TMS) is a non-invasive technique that induces human cortical plasticity and allows the assessment of modulated cortical excitability. Functional Near Infra-Red Spectroscopy (fNIRS) is a non-invasive neuroimaging modality, which allows monitoring changes in oxy- and deoxy-hemoglobin (i.e., HbO/HbR) in the cerebral cortex. Taking advantage of the fNIRS technique being insensitive to electromagnetic artifacts and wearable, the combination with TMS provides a unique and promising way to assess the relationship between cortical excitability and hemodynamic responses in humans.
This Ph.D. thesis consists of four original studies combining personalized Near Infra-Red Optical Tomography (NIROT) and TMS to investigate the hemodynamic correlates of fluctuations in neuronal excitability, each including key methodological developments. In the first manuscript, we proposed and evaluated a new NIROT reconstruction method – the Maximum Entropy on the Mean (MEM), by adapting and improving its original version proposed for Electro-/Magneto-encephalography source imaging. After detailed evaluations of MEM NIROT on realistic simulated data, we introduced in the second manuscript the original concept of personalized NIROT workflow combining MEM reconstruction and personalized optimal montage. Using functional magnetic resonance imaging as the reference, the evaluation of finger tapping data demonstrated that our proposed workflow allowed better spatial accuracy and reliability than other widely used NIROT methods. The third manuscript applied this workflow on a simultaneous TMS and fNIRS study and demonstrated a positive relationship between motor task-related hemodynamic activity and cortical excitability. The last manuscript applied advanced Bayesian data analysis and hierarchical models to the same data set, which improved the accuracy and reliability of the results when dealing with relatively high variability and small sample size data. Our results showed a significant positive correlation between the effects of TMS modulated cortical excitability and its effects on task-related hemodynamic activity. Therefore, our studies contribute to further expand the application of brain stimulation to the treatment of neuronal disorders that may require modulations of the hemodynamic response.