Copyright of Brock Student Theses and Major Research Papers (MRPs)


Students retain the copyright of their theses and major research papers. Under the terms of the “Thesis and Major Research Paper Copyright Licence” students grant Brock University the right to preserve and disseminate theses and major research papers via the Brock University Digital Repository, Library and Archives Canada and in other third party thesis databases.

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  • Lifestyle factors and neuroimaging metrics as predictors of cognitive performance in healthy aging

    Guardia de Souza e Silva, Tiago; Department of Psychology
    Despite all the advances made in health-related and psychological sciences, advancing age continues to be accompanied by cognitive decline. Aging is usually associated with major changes in the structure and functioning of the brain that lead to impairments in multiple cognitive functions. The trajectories of age-related effects on the brain and cognition exhibit considerable differences across cognitive domains and across individuals, and investigating approaches and factors that might prevent brain and cognitive decline during aging is considered a topic of great scientific and public health relevance. The overall goal of this thesis was to evaluate age-related differences in brain structure and functional connectivity to further our understanding of the neural mechanisms involved in age-related declines in cognition. This thesis also aimed to investigate the influence of lifestyle factors on age differences in cognition, and in that regard, I focused on the effects of sleep quality and physical activity on memory. In Study 1, I assessed the impact of aging on grey matter volume of the medial temporal lobe MTL and prefrontal cortex PFC and compared the relative contributions of MTL and PFC structures to age differences in associative memory. My findings emphasize the critical role of the frontal lobes, and the control processes they subserve, in determining the detrimental effects of age on memory. Additionally, I observed that the relationship between frontal grey matter volume and memory was not moderated by age or sex, suggesting that greater volume in PFC structures relates to better memory performance across the lifespan and in both sexes. In Study 2, I assessed the effects of age on functional brain networks. Given the essential role of the arousal system (ARAS) in cortical activation and previous findings of disrupted ARAS functioning with age, I investigated the hypothesis that age-related changes in ARAS-cortical functional connectivity may contribute to commonly observed age-related differences in cortical connectivity. The findings of this study showed that the arousal system is functionally connected to widespread cortical regions and suggest that age differences in functional connectivity within the cortex may be driven by age-related changes in the brainstem and these altered connectivity patterns have important implications for cognitive health. In Study 3, I investigated the relationship between sleep quality, physical activity, and memory in middle-age and older adults, in addition to assessing the impact of the COVID-19 pandemic on participants’ mood and sleep quality. Our results showed that people who were more active reported better sleep quality and showed better memory, and better sleep quality was associated with better memory. Moreover, our findings also showed that some of the beneficial effects of physical activity on cognition are partially mediated by improved sleep. Additionally, this study indicated that the COVID-19 pandemic had a deleterious effect on people’s sleep quality and overall well-being. Taken together, these studies suggest that aging is associated with disruptive effects on brain structure and function, and that these changes are associated with age-related cognitive decline. Additionally, our study supported the association between lifestyle factors, more specifically, sleep quality and physical activity, and cognitive performance during aging.
  • Are We There Yet? An Examination of the Effectiveness of Individual Support Plans in Promoting the Human Rights and Quality of Life for Persons with Intellectual and/or Developmental Disabilities

    Bishop, Courtney; Department of Child and Youth Studies
    Individual Support Plans (ISP) play a significant role in ensuring that the value-based disability-related goals of international and provincial legislation are brought to fruition—mainly with a focus on promoting Human Rights and improving quality of life (QOL) outcomes. The ISP is a living document that, through person-centered planning practices, guides the day-to-day supports provided to persons labelled with an intellectual and/or development disability (PLWIDD). Literature has demonstrated that ISPs are most effective when there is an alignment between an individual’s identified needs and wants, clearly defined goals with matched support strategies, and measurement tools to monitor and evaluate individual and team progress towards goal attainment. Further, ISPs are more likely to demonstrate improved QOL outcomes when the goals capture and promote the following QOL domains: self-determination, personal development, interpersonal relationships, social inclusion, rights, and physical, emotional, and material well-being. This project aimed to promote improved QOL outcomes for PLWIDD supported by Community Living Haldimand, through a collaborative examination of their current ISP framework and processes. The goal of this project was to provide recommendations for a new ISP framework that was shaped by current research on effective and efficient ISPs, and authentically founded in the expressed concerns and recommendations of those who are responsible for developing, implementing, monitoring, and evaluating the effectiveness of the ISP. A document analysis of 9 completed ISPs identified the alignment across the components of an effective ISP and the number and types of QOL domains that were or were not present. A Nominal Group Technique (NGT) and focus group participation from Coordinators and Supervisors assisted in capturing the culturally sensitive language surrounding QOL and the ISP process. Recommendations for the new ISP framework included the use of culturally sensitive language and recommendations from Coordinators and Supervisors, including staff support and training in identified areas of concern such as, how to identify needs and wants of persons they support and how to define ISP goals. The methods used in this study may assist other organizations in the evaluation and improvement of their ISP process.
  • On the Efficacy of Treating Escape-Maintained Inappropriate Mealtime Behaviour with and Without Escape Extinction: A Meta‐Analysis of Escape‐Based Interventions

    Scott, Victoria; Center for Applied Disability Studies
    It is estimated that approximately 70% to 89% of children with developmental disabilities and 20% to 50% of neurotypical children exhibit some type of feeding challenge. Inappropriate mealtime behaviour (IMB) is a type of feeding challenge within the broader class of food refusal behaviour. Although there have been some single-case studies examining the extent to which behavioural interventions can aide in reducing IMB, the relative efficacy and generality of these studies is unclear. The purpose of this systematic review was to evaluate the available literature to critically analyze the efficacy of interventions for the treatment of IMB through a meta-analysis of single-subject experimental designs. Through a systematic search of the extant literature, we identified 38 studies involving 307 cases in which IMB was treated with a behavioural intervention. We coded descriptive data and calculated log response ratio as an effect size measure of the efficacy of these interventions. Results indicated that combined escape extinction and non-escape extinction interventions had greater effect sizes than escape extinction alone or non-escape extinction alone. Escape extinction alone had greater effects sizes compared to non-escape extinction; however, escape extinction resulted in a higher percentage of negative side effects than interventions in which escape extinction was combined with non-escape extinction interventions or to non-escape extinction interventions alone. We suggest that escape extinction should not be used as the sole intervention for IMB, rather, in cases where IMB warrants a behavioural intervention, a combination of escape extinction and non-escape extinction interventions should be used.
  • Role of Viral Infections in Rapid Prunus Decline in the Niagara Region

    Prosser, Jessica Carlene; Department of Biological Sciences
    Plant diseases associated with viral infections are a serious issue for growers, causing significant reductions in yield and plant death. Rapid Prunus Decline (RPD) is an emerging disorder resulting in rapid and unexplained death of Prunus species in southern Ontario. In order to better understand RPD, disease symptoms in all major Prunus species in the Niagara region were surveyed, along with identification of major viruses in diseased Prunus trees. Our survey showed that diseased trees often showed symptoms of dehydration, leaf chlorosis, reduced new growth, and death. The average mortality rate in the Niagara region was 20% among all Prunus species with the highest site-specific mortality rate of 67%. In order to understand the contribution of viruses to RPD, RNA sequencing was employed to identify viruses in diseased trees and characterize viral sequence diversity. In total, 20 unique virus species and one viroid were identified in 42 diseased trees, demonstrating a wide diversity of viruses in diseased Prunus trees. Tomato ringspot virus (ToRSV) infection can result in similar symptoms to those observed in RPD trees. Based on these similar symptoms, a total of 507 Prunus trees were surveyed and the frequency of ToRSV infection was determined to be 13%. No direct correlation was identified between the presence of ToRSV and incidence of RPD, suggesting that other factors are involved. Multiple ilarviruses were identified in diseased trees including Grapevine associated ilarvirus (GaIV), Tobacco streak virus (TSV), Tomato necrotic spot virus (ToNSV), Prunus necrotic ringspot virus (PNRSV), and Prune dwarf virus (PDV). GaIV and ToNSV have never been previously reported in Prunus trees, or in Canada. GaIV was the most commonly detected virus and is an emerging concern for stone fruit production. Mixed infection of ilarviruses could have synergistic pathological effects, and the interactions between ilarviruses and other viruses are poorly understood. In summary, over the course of this study, many different viruses were identified in Prunus species exhibiting decline, yet no single virus was identified in all Prunus spp. or in all instances of the disease, suggesting RPD is a complex disease that could have multiple contributing factors.
  • Effect of Augmented Reality (AR) experiential value and flow experience on psychological ownership of product and technology

    Iqbal, Idaf; Faculty of Business Programs
    The emergence of Augmented Reality (AR) technologies has made it possible for marketers to engage and interact with consumers in new ways and thus influence positive behavioral outcome. The interactive nature of the AR technologies provides consumers scope to form attachment with the product and technology in forms of psychological ownership. Although the formation of psychological ownership of both product and technology has been studied, they have been studied separately. As AR being highly interactive provides scope for forming attachment with the product and technology, this study addresses the literature gap by providing a mechanism to understand the formation of both psychological ownership of product and technology and their relationship with AR’s functional and emotional value. By analyzing responses from 480 online survey respondents, we provide empirical evidence that the functional and emotional value has opposite effect on the psychological ownership of consumers. Specifically, our results show that the functional value negatively affects while as emotional value positively affects psychological ownership of product and technology, and flow experience mediates these relationships. Consumers’ perceived control also plays a role in the formation of psychological ownership of product and technology as well as their flow experience. We find empirical evidence that for high (low) perceived control, the positive effect of emotional value of consumers on the psychological ownership of product and technology is strengthened (weakened); while as for high (low) perceived control, the negative effect of functional value on the consumers psychological of product and technology is weakened (strengthened). Although our results show that perceived control does not moderate the relationship of functional values with that of flow experience, it moderates the relationship of emotional values with flow experience such that for high (low) perceived control, the positive effect of emotional value on flow experience is strengthened (weakened). These findings can help marketers in AR app design by helping them understand how different functional and emotional aspects of the AR experience affect consumers’ psychological ownership of product and technology.
  • Enhancing Augmented Reality with Audio: When and why it boosts online purchase intention

    Sharifihosseini, Forough; Faculty of Business Programs
    Augmented reality (AR) can be considered an appealing tool for product evaluation in an online shopping context where the product is unavailable. Although this technology provides a tangible environment for product evaluation, it is mainly based on the visual aspect of product presentation. Vision is a dominant sense, and humans mostly rely on sight to comprehend an event. Nevertheless, it is only from a combination of senses that one can gain an extensive understanding of it. Auditory sensory is the second crucial human sense. The literature documenting AR's impact on customers' decision-making and behavioural intentions has overlooked the role of audio in this environment. This study investigates the role of audio through product sounds in an AR experience, and by using active inference theory, it demonstrates how enhancing AR environments with sound can influence behavioural intentions in customers. Moreover, it presents two important auditory factors (i.e., sound pleasantness and sound controllability), each of which can have impactful roles in different online shopping steps. Using data obtained from the Zappar AR platform, this research examines two products with their related sounds to demonstrate the performance of multisensory AR experience on behavioural intentions of customers who use AR apps for shopping online. The results indicate that enhancing AR with sound has both direct and indirect influence on behavioural intentions of the customers, through customer engagement and decision comfort. Additionally, we show the moderating role of sound controllability on the relationship between audio-enhanced AR and customer engagement.
  • Gay men, well-being, and sport participation: A phenomenological analysis

    Quinton, Jake; Applied Health Sciences Program
    There is a growing interest among scholars and practitioners in LGBTQ+ experiences in sport and leisure. While much of this work has examined homophobia and negative experiences, few studies have examined positive sport experiences of LGBTQ+ athletes. To add to that growing body of literature, the purpose of this study was to explore how gay men navigate potentially stressful environments and derive experiences of well-being, and to gather phenomenological accounts of how gay men derive and experience well-being through sports participation despite the stressful environment they may represent for LGBTQ+ athletes. Specifically, I explored how minority stress theory can provide a deeper understanding of the role stressors play in how gay men derive experiences of well-being through sport participation. Using a phenomenological approach, data were collected through semi-structured interviews with nine gay men between the ages of 32 and 43. Themes that capture the overall phenomenon were constructed. These were Craving Community: Reconciling Past Experiences, Sports and Living Authentically, and Sports as an Escape. The data demonstrated the complexity of the gay men's experiences of well-being and allowed me to explore participants' similar and unique experiences in sport more deeply. The findings highlight the ways in which gay men derive well-being from sports participation and the roles stressors play in how they derive that well-being. This study provides a deeper theoretical understanding of the experiences of gay men participating in sports, as well as highlighting how gay men derive positive outcomes from these experiences.
  • Psychopathy as a Conditional Reproductive Strategy in Boys and Men: An Evolutionary–Developmental Perspective

    Brazil, Kristopher; Department of Child and Youth Studies
    Psychopathic traits (PTs) are a constellation of traits and behavior that places individuals at-risk for engaging in lifelong chronic and severe antisociality, particularly among boys and men. Evolutionary perspectives have suggested some adaptive benefits (e.g., mating) to expressing PTs, whereas developmental perspectives suggest both genes and environment affect its expression. Bringing evolutionary and developmental perspectives together, my thesis addresses whether the expression of psychopathy in boys and men is developmentally contingent on cues of social relationships that inform the costs and benefits of “deciding” to develop PTs. In Study 1, I use Bronfenbrenner’s bioecological theory to survey the developmental literature on PTs to examine whether both immediate and broad environmental features contingently affect the development of PTs. Results suggest that the expression of PTs is affected by multiple and interacting levels of the environment. In Study 2, I examine how PTs in boys might have costs and benefits in social relationships and the possible impact behavior with peers may have on peer reactions. Results showed PTs were associated with more coercive and fewer prosocial behavior with peers, the latter having a negative indirect effect on peer reactions in prosocial, social power, and dating domains. PTs also had a direct and positive association with receiving nominations as someone peers would like to date. The findings suggest PTs may have both costs and benefits in adolescence and suggest boys higher in PTs might deceptively manage their reputations with peers despite engaging in fewer prosocial and more coercive behavior. In Study 3, I examine how PTs affect trade-offs across adaptive domains of somatic (e.g., relationships, health), parental, and mating investment in men. Results suggest that men higher in PTs may trade-off somatic and parental efforts for mating effort, which may create a superficial yet effective mating strategy that enhances mating opportunities while foreclosing other opportunities (e.g., building relationships, skills). Overall, my thesis expands our understanding of psychopathy by considering both evolutionary and developmental perspectives together. In particular, the adaptive benefits and costs of expressing psychopathy may be directed by and located within a developmental ecology that contingently affects its expression.
  • An investigation into the utility of wearable sensor derived biofeedback on the motor control of the lumbar spine

    Battis, Aurora; Applied Health Sciences Program
    Lower back pain (LBP) is a disability that affects a large proportion of the population and treatment for this has been shifting towards a more individualized, patient-centered approach. There has been a recent uptake in the utilization and implementation of wearable sensors that can administer biofeedback in various industrial, clinical, and performance-based settings. The overall aim of this Master’s thesis was to investigate how wearable sensors can be used in a sensorimotor (re)training approach, including how sensory biofeedback from wearable sensors can be used to improve measures of spinal motor control and proprioception. Two complementary research studies were completed to address this overall aim. As a systematic review, Study #1 focused on addressing the lack of consensus surrounding wearable sensor derived biofeedback and spine motor control. The results of this review suggest that haptic/vibrotactile feedback is the most common and that it is administered in an instantaneous real-time manner within most experimental paradigms. Further, study #1 identified clear gaps within the research literature. Specifically, future research would benefit from more clarity regarding study design, and movement instructions, and explicit definitions of biofeedback parameters to enhance reproducibility. The aim of Study #2 was to assess the acute effects of wearable sensor-derived auditory biofeedback on gross lumbar proprioception. To assess this, participants completed a target repositioning protocol, followed by a training period where they were provided with auditory feedback for two of four targets based on a percentage of their lumbar ROM. Results suggest that mid-range targets benefitted most from the acute auditory feedback training. Further, individuals with poorer repositioning abilities in the pre-training assessment showed the greatest improvements from the auditory feedback training. This suggests that auditory biofeedback training may be an effective tool to improve proprioception in those with proprioceptive deficits. Collectively these complimentary research studies will improve the understanding surrounding the ecological utility of wearable sensor derived biofeedback in industrial, clinical, and performance settings to enhance to sensorimotor control of the lumbar region.
  • Semi-synthesis of Unnatural Narciclasine Derivatives

    Thomson, Jared; Department of Chemistry
    The generation of new structural derivatives of narciclasine, an Amaryllidaceae alkaloid, has been explored. The strategy applied to the semi-synthesis of these derivatives involves a key enolization step that produces an enol at the C1 position. This material was converted into a triflate to functionalize the C1 position through cross-coupling. Initial triflation attempts resulted in functionalization at C6 instead, and the C6 triflate was successfully coupled with different functionalities. All the novel C6 derivatives were fully deprotected and subjected to evaluation of their biological activity. Experimental and spectral data are provided for all new compounds
  • Exotic gap structures in multiband superconductors

    Nanchian, Hooman; Department of Physics
    The symmetry-based approach is a capable method in the theory of superconductivity. To understand how the gap function transforms under the point group operation, one needs to know the transformation properties of the single-electron states. Accord- ing to the Ueda-Rice prescription, the transformation of the Bloch states, under the operation of a point group element, is described by the pure spin-1/2 rotation matrices, even in the presence of spin-orbit coupling. In the presence of spin-orbit coupling, we show that the Bloch states in a centrosymmetric and non-magnetic crystal are not the eigenstates of the pure spin-1/2 operators. In this case, the transformation of the Bloch states depends on the symmetry of the bands participating in the pairing. This transformation is not necessarily equivalent to the transformation of the pure spin-1/2 Bloch states. In this work, we study a hexagonal multiband superconductor with a D6h point group in the presence of spin-orbit coupling. We discovered that the Bloch states in some specific bands do not transform like pure spin-1/2 states. This behavior of the electron bands leads to an exotic gap nodal structure that we study in two pairing channels. In an interband s-wave pairing, some nodes appear in the gap structure of the superconductor. In an interband i-wave pairing, the gap nodes move by changing the strength of the interband pairing. The pseudospin symmetry-based approach, presented in the textbooks, does not predict these results.
  • Deadly Wounds in the US-Mexico Borderlands: A Rhetorical Analysis of the Anti-Illegal-Immigration News Media Coverage of the El Paso Shooting and the Viral Video of the United Constitutional Patriots

    Lopez Nava, Elvia; Social Justice and Equity Studies Program
    This thesis focuses on two key events that took place at the US/Mexican border in 2019 and the anti-illegal-immigration media coverage of those two events: 1) The El Paso Walmart Shooting and 2) the viral video of the United Constitutional Patriots detaining migrants at the US-Mexico border. I explore the discursive practices used to discuss the El Paso shooting and the UCP’s actions and connect these practices to anti-immigrant rhetoric that has been ingrained in the public discourse of the U.S. I argue the anti-illegal-immigration news media coverage of the El Paso shooting and the UCP reflect, produce, and embody anti-immigrant rhetoric as well as portray white nationalist behavior under the guise of patriotism. I found 5 figures that emerged from my data used by the anti-illegal-immigration media outlets: the “Illegal alien”, the Immigrant Child, the Spectator, the Patriot or the White Nationalist, and the “Monster”.
  • Evaluating Preference Stability Across Psychotropic Medication Changes in Persons with Intellectual and Developmental Disabilities

    Kozluk, Autumn; Applied Health Sciences Program
    Research in applied behaviour analysis evaluating psychotropic medication impact on persons with intellectual and developmental disabilities (IDD) is relatively limited (Cox & Virués-Ortega, 2016). Even though evidence supporting the efficacy of psychotropic medication in treating challenging behaviour has been described as controversial, an Ontario study reported between 39% to 56% of adults with IDD are prescribed at least one psychotropic medication (Lunksy et al., 2018). The overall prevalence of medication use within this population, combined with the lack of research showcasing efficacious outcomes, suggests that further evaluation of psychotropic medication impacts is required. Behaviour analytic researchers have hypothesized that psychotropic medications may function as motivating operations (Conine & Vollmer, 2019). Therefore, it may be important to systematically monitor clinically indicated medication changes for their effect on an individuals preference stability, as well as on stimulus class displacement. Two participants with IDD who engage in challenging behaviour and were undergoing medication changes (e.g., medication increases, decreases, addition, and removal) took part in repeated weekly preference assessments (edible-item, leisure-item, and combined-class). Analysis included a Spearman rank correlation analysis, a non-parametric partial correlation analyses, and visual analysis to these data. Results indicated that psychotropic medication changes appeared to affect non-selection, preference stability, and class displacement differentially across the two participants. Clinical implications, limitations, and future directions are discussed.
  • Deep Evolutionary Generative Molecular Modeling for RNA Aptamer Drug Design

    Andress, Cameron; Department of Computer Science
    Deep Aptamer Evolutionary Model (DAPTEV Model). Typical drug development processes are costly, time consuming and often manual with regard to research. Aptamers are short, single-stranded oligonucleotides (RNA/DNA) that bind to, and inhibit, target proteins and other types of molecules similar to antibodies. Compared with small-molecule drugs, these aptamers can bind to their targets with high affinity (binding strength) and specificity (designed to uniquely interact with the target only). The typical development process for aptamers utilizes a manual process known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX), which is costly, slow, and often produces mild results. The focus of this research is to create a deep learning approach for the generating and evolving of aptamer sequences to support aptamer-based drug development. These sequences must be unique, contain at least some level of structural complexity, and have a high level of affinity and specificity for the intended target. Moreover, after training, the deep learning system, known as a Variational Autoencoder, must possess the ability to be queried for new sequences without the need for further training. Currently, this research is applied to the SARS-CoV-2 (Covid-19) spike protein’s receptor-binding domain (RBD). However, careful consideration has been placed in the intentional design of a general solution for future viral applications. Each individual run took five and a half days to complete. Over the course of two months, three runs were performed for three different models. After some sequence, score, and statistical comparisons, it was observed that the deep learning model was able to produce structurally complex aptamers with strong binding affinities and specificities to the target Covid-19 RBD. Furthermore, due to the nature of VAEs, this model is indeed able to be queried for new aptamers of similar quality based on previous training. Results suggest that VAE-based deep learning methods are capable of optimizing aptamer-target binding affinities and specificities (multi-objective learning), and are a strong tool to aid in aptamer-based drug development.
  • Low-dimensional purple and blue bronzes: Crystal growth, characterization and optical properties

    Ahmadi, Mohammad; Department of Physics
    The molybdenum oxide bronzes are a family of charge-density-wave (CDW) conductors with distinctive properties originating from their low-dimensional crystal structure and associated Fermi surface instabilities. Single crystals of potassium blue and purple bronzes and sodium purple bronze have been synthesized using a temperature flux technique and XRD measurement was deployed to investigate the formation of the correct phase. Optical spectroscopy and electrical resistivity measurements were carried out on sodium purple bronze and potassium blue bronze. Sodium purple bronze crystals were found to exhibit a clear anisotropy in their natural cleavage (a-b) plane. Electrical resistivity measurements were performed along the different crystallographic directions which displayed two distinct metallic axes perpendicular to each other in the a-b plane. The optical conductivity obtained from Kramers-Kronig analysis of reflectance spectroscopy data was in good agreement with the resistivity measurements. The two in-plane metallic axes undergo CDW transitions at two different temperatures Tp, suggesting a distinction in electronic and phononic subsystems along each axis. Potassium blue bronze samples exhibit various temperature dependent anomalies in the electrical resistivity measurements, which are associated with CDW instability in this compound. The absolute values of resistivity at room temperature along both in-plane crystallographic axes, were compared to the literature to verify the accuracy of our measurement techniques. The ac-current effects on linear and non-linear regimes of resistivity were closely investigated, and the results support the sliding of the CDW, and the existence of a small-threshold field ET of CDW depinning in this sample. Hysteresis in resistivity, which has been detected in many CDW compounds, has been observed in our measurements and is associated with the instability of the CDW possibly due to the presence of defects.
  • Synthesis of unnatural analogues of narciclasine: Chemoenzymatic synthesis of 2-epi-1-hydroxymethylnarciclasine

    Bedard, Korey; Department of Chemistry
    An approach to the synthesis of novel C-1 analogues of narciclasine has been developed. The synthesis relies on chemoenzymatic dihydroxylation of an arene, Stille coupling, and an intramolecular Heck reaction to affect key transformations. The synthesis of the targeted C-1 analogues addresses a gap in literature where few narciclasine analogues have been prepared, with no C-1 homologues existing to date. The synthetic route to 2-epi-1-hydroxymethylnarciclasine, as well as a possible route to several other derivatives, is described in detail. Experimental and spectral data are provided for all newly synthesized compounds.
  • Synthesis of C-1 Homologues of Narciclasine

    Habaz, Lihi; Department of Chemistry
    This thesis describes current progress towards the total synthesis of C1-homologues of the Amaryllidaceae alkaloid narciclasine (1), a powerful anticancer agent which suffers from a poor solubility profile. A 15-step chemoenzymatic total synthesis of C-1 carboxymethyl narciclasine (248) was accomplished. A key step in this convergent synthesis is the formation of the C ring syn-diol moiety via the chemoenzymatic dihydroxylation of ortho-dibromobenzene to provide the corresponding cis-dihydrodiene diol as a single enantiomer, which constitutes an efficient method of generating chiral substrates from readily available commercial materials. The dense A ring functionalities are derived from another commercially available unit; ortho-vanillin, via previously established protocols. Further key steps involve a nitroso Diels-Alder reaction and an intramolecular Heck reaction. The C-1 homologue that was prepared, 248, was then tested for its biological activity against natural narciclasine as the positive control. Experimental and spectral data are provided for all novel compounds.
  • Old Wines in New Bottles: Repurposing and Leveraging of Existing Resources for Crafting Novel Information System-Based Organizational Innovations

    Nayeri, Ehsan; Faculty of Business Programs
    In this research, we propose, define and empirically examine the idea of resource repurposing for innovation (RRI). Firms are increasingly introducing innovative products and services by repurposing their existing resources, products and services instead of trying to build something completely new from scratch. While these practices have become prevalent, they have remained overlooked by researchers. We introduce the construct of RRI by drawing on the related and relevant theories of architectural innovation, bricolage, exaptation and recombination. Further, we argue that our conceptualization of RRI is built on the basis of two important dimensions: the extent of resource modification, and the site of innovation manifestation. Therefore, RRI can be practiced in four different ways. We proposed a preliminary framework to study the RRI approach and its relevant dimensions and antecedents. Through a qualitative exploratory study, we interviewed 22 informants from 20 firms in North America that are active in a wide range of different industries. We performed content analysis by conducting an extensive coding process on the transcribed interviews. Our findings reinforced that RRI is a multidimensional construct with four different facets. Also, the patterns of RRI practices can be influenced by key organizational characteristics such as company size, technology, innovation and knowledge management, and employee training policies and activities. Further analysis of the emergent themes in the empirical data reinforced our preliminary assumptions that knowledge creation capabilities, resource digitalization, resource diversity and IT integration capabilities may influence different types of RRI practices. The constructs, findings and conjectures provided by this study may pave the way for future research on the novel construct RRI.
  • Characterizing the Development of Reward Evaluation Across Adolescence in Female and Male Long-Evans Rats

    Murray, Shealin; Department of Psychology
    Adolescence is a developmental stage describing the transition from childhood to adulthood, that is a heightened period of sensitivity to influence from the environment due to extensive physical, physiological, and psychological maturation. Adolescents, both human and rat, have been observed to evaluate reward differently than other ages, however little is known about how reward evaluation may change throughout adolescence, and how these developmental trajectories may vary between reward types and between sexes. My thesis work focused on characterizing changes in sensitivity to and motivation for reward across adolescence in female and male Long-Evans rats. In chapter 2, I used a free-access drinking task to compare how testing conditions (within- group or between-group) influenced intake of diluted sweetened condensed milk and found that previous test experience was necessary to facilitate a peak in adolescent male rats intake normalized for body mass as reported in previous research. However, this peak did not occur in female rats, and when intake was not normalized per body mass the peak was not found in male rats either. In chapter 3, I used an operant conditioning paradigm to investigate social motivation across adolescence and found that male rats overall were more socially directed than female rats when using a fixed ratio, however there was a lack of sex differences when using a progressive ratio, except for male rats at postnatal day (P) 40. At P40 male rats were less socially motivated than P40 female rats, and less socially motivated than male rats at younger and older ages. Overall, my thesis work suggests that the development of reward processing is dynamic across the adolescent period, and that peaks in reward evaluation depend on sex and procedure.
  • Age Differences in Working Memory Filtering of Distracting Information

    Torres Hernandez, Rosa; Department of Psychology
    Previous research has demonstrated that as people age, cognitive processes such as visual working memory (VWM) performance decline. One potential explanation for this age-related decline in VWM is that older adults have decreased inhibitory control relative to younger adults. This impairs older adults’ ability to ignore irrelevant information, which contributes to VWM filtering ability deficits. While most research investigating filtering ability deficits in older adults has tended to use positive cues, it is unclear whether older adults can also effectively use negative cues to ignore irrelevant information. The current study tested whether older adults can filter out irrelevant information from their VWM using negative cues. Across two experiments, young and older adults were presented with 2 (Experiment 1) or 4 (Experiment 2) display items. Participants were given three different cue types: neutral, negative, or positive. After a delay, participants reported the target’s orientation in a continuous-response task. Our results demonstrate that both age groups’ VWM performance benefitted from being provided a cue (positive or negative) as opposed to no cue (i.e., the neutral condition). However, for both age groups, negative cues were less effective at improving VWM filtering (i.e., more non-target errors) compared to positive cues. Thus, although negative cues aid in filtering of VWM contents, they are less efficient than positive cues. Additionally, older adults are similarly efficient to young adults at inhibiting negatively cued information, resulting in a reduction of distractor intrusions into VWM when using the negative cue, although this benefit is reduced (for both age groups) at higher set sizes.

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