• Synthesis and Reactivity of Low Valent Main Group Element Complexes

      Chu, Terry; Department of Chemistry
      The β-diketiminate aluminum(I) complex NacNacAl (III-1) was shown to activate a range of substrates containing robust single and double bonds. Compound III-1 oxidatively adds a variety of H–X bonds (X = H, B, Al, C, Si, N, P, O) to give a series of four-coordinate aluminum hydride derivatives including the first example of an aluminum boryl hydride. In the case of Al–H addition, the reaction was shown to be in equilibrium and reversible. Furthermore, cleavage of aryl and alkyl C–F bonds, the latter a rare reaction with only a handful of examples in the literature, was observed with III-1. Robust C–O and C–S bonds were also activated by III-1 along with RS–SR and R2P–PR2 bonds. All novel aluminum complexes were characterized by spectroscopic methods and X-ray diffraction analysis for the majority of them. Activation of the C=S or P=S bonds in a thiourea or phosphine sulfide, respectively, was accomplished by III-1 to give the first examples of Lewis base-stabilized monomeric terminal aluminum sulfides. The nature of the Al=S bond was examined computationally as well as experimentally. Related reaction with a urea derivative gave an unexpected aluminum hydride while reaction of III-1 with phosphine oxides gave a putative aluminum oxide as a result of P=O bond cleavage. However, the aluminum oxo promptly deprotonates a neighbouring molecule to furnish an aluminum hydroxide as the isolated product. Reduction of the cationic germanium(II) complex IV-1 affords the formally zero valent germanium complex IV-4 stabilized by the bis(imino)pyridine platform. Compound IV-4 was fully characterized by spectroscopic methods and X-ray diffraction analysis. The molecule has a singlet ground state and DFT studies revealed partial delocalization of one of the germanium lone pairs into the ligand framework. Complex IV-4 was unreactive towards H–X bond activation, the lack of reactivity ascribed to the large singlet-triplet energy gap calculated. The same bis(imino)pyridine ligand was also used to prepare reduced zinc complexes. Monoreduction of the zinc dichloride precursor gave the formally Zn(I) compound IV-6. Further reduction of IV-6 in the presence of DMAP gave the formally zero valent zinc complex IV-9. Both compounds were fully characterized by spectroscopic methods, DFT calculations, and X-ray diffraction analysis which revealed that both zinc atoms are four-coordinate and adopt unusual square planar and see-saw geometry, respectively.
    • Synthesis and Reactivity of Low Valent Silicon and Phosphorus Compounds

      Baradzenka, Aliona; Department of Chemistry
      The research described in this thesis is focused on studying the use of phosphinoamidinato ligand NP (NP = [ArNC(Ph)NPiPr2]– (Ar = 2,6-iPr2C6H3)) to stabilize low-valent main group element compounds. Reduction of silane (NP)SiCl3 by magnesium allows for the high-yield preparation of base-stabilized disilylene [(NP)Si-]2. Although it is stable at room temperature, upon heating it rearranges via intermolecular N-P activation into an N,Si-heterocyclic silylene supported by a phosphine donor. The reactivity of [(NP)Si-]2 in the single bond activation of pinacolborane, phenylsilane and diphenylphosphine was tested. Additionally, the phosphidosilylene (NP)SiPPh2 that is formed in the last reaction was found to perform P-P coupling when reacted with diphenylphosphine. Experimental pursuits were taken to elucidate the mechanism of formation of disilylene [(NP)Si-]2, and some insights into its fluxionality in solution were obtained. Disilylene [(NP)Si-]2 was reacted with Si(II) and Ge(II) chlorides to yield the products of tetrylene insertion into the Si-Si bond, the low-valent compounds [(NP)Si-Si(Cl)2-Si(NP)], [(NP)Si(Cl)2Si-Si(NP)] and [(NP)Si(Cl)2Ge-Si(NP)]. Compound [(NP)Si-Si(Cl)2-Si(NP)] is the kinetic product of the direct insertion of SiCl2 fragment into Si-Si bond of [(NP)Si-]2. The thermodynamic product of the insertion of silicon dichloride is disilylene [(NP)Si(Cl)2Si-Si(NP)] that is the consequence of migration of chlorides to terminal Si center. The reaction of [(NP)Si-]2 with GeCl2 produced only one compound [(NP)Si(Cl)2Ge-Si(NP)] that is a rear example of germylene-silylene. Interaction of [(NP)Si-]2 with SiCl4 and SiHCl3 produced a new example of acyclic disilyl silylene. Reduction of (NP)PCl2 with potassium graphite allowed isolation of the base-stabilized phosphinidene (NP)P. Its reactivity was studied. The use of substrates with E-H bonds like pinacolborane, phenylsilane and diphenylphosphine yielded compounds (NP)Bpin (pin = (OC(CH3)2)2) and NPH, (NP)SiH2Ph and NPH, NPH-P-PPh2, respectively, which are the result of N-P and E-H bond metathesis. Upon reaction with tetrachlorobenzoquinone both phosphorus atoms of phosphinidene (NP)P underwent oxidation. (NP)P reacted with benzaldehyde and phenylisocyanate as a phospha-Wittig reagent. Additionally, (NP)P was transformed into phosphinidene oxide (NP)P=O, iminophosphine (NP)P=Np-Tol and phosphinidene sulfide (NP)P=S. Transient (NP)P=O and (NP)P=Np-Tol were captured by para-tolyl isocyanate to form compound (NP)P(N,N-(Np-Tol)2CO). All the compounds were fully characterized by NMR and for most of them single crystal X-ray structure was obtained.
    • Synthesis and Reactivity of Main Group Complexes for Applications in Small Molecule Activation

      Nguyen, Minh Tho; Department of Chemistry
      The work described in this thesis is focused on the preparation of a series of novel main group complexes, featuring unusual structural and bonding situations, and the study of their reactivity toward small molecules. The new zinc complexes dimphZnBu (V-2) and dimphZnCl2Li(THF)3 (V-3), supported by a diiminophenyl (dimph) ligand were prepared. The reaction of complex V-3 with LiHBEt3 resulted in hydride transfer to the C=N imine group to give an unusual zinc dimer (V-7). The latter transformation occurs via formation of compound (ɳ1(C),ĸ1(N)- 2,6-(2,6-iPr2C6H3N=CH)2C6H3)2Zn (V-5) which can be also accessed by reduction of V-7 with KC8. Diiminophenyl (dimph) proved to be an excellent ligand platform to stabilise a low-valent phosphorus centre. The resultant compound dimphP (VI-2), which can be rationalised as an imino-stabilised phosphinidene or benzoazaphopshole, shows remarkable chemical stability toward water and oxygen. VI-2 reacts with excess strong acid HCl to generate the P(III) chloride (dimHph)PCl (VI-6). Surprisingly, substitution of the chloride under some nucleophilic (KOBut) and electrophilic conditions (Me3SiOTf) regenerates the parent compound VI-2 by proton removal from the weakly acidic CH2N position. A related species (dimH2ph)P (VI-10) is produced upon thermal rearrangement of the hydride (dimHph)PH (VI-9). The molecular structure and reactivity of compounds VI-2 and other related compounds are also discussed. The reduction of the O,C,O-chelated phosphorus (III) chloride (VI-16) ( O,C,O = 2,6-bis[(2,6-diisopropyl)phenoxyl]phenyl) with KC8 or PMe3 resulted in the formation of a cyclic three-membered phosphorus compound (VI-18). The intermediacy of phosphinidene VI-17 was confirmed by trapping experiments and a VT 31P{1H} NMR study. The reaction of in-situ generated phosphinidene with either PhSiH3 or HBpin resulted in the formation of an unprecedented phosphine (VI-23). The treatment of VI-16 with two equivalents of DippNHC carbene led to ArP(Cl)NHC product (VI-24). The germylone dimNHCGe (dimNHC = diimino N-Heterocyclic Carbene, VII-8) was successfully prepared by the reduction of germanium cation (VII-7) with KC8. The molecular structure of VII-8 was unambiguously established, using NMR spectroscopy and single-crystal X-ray diffraction analysis. The reactivity of VII-8 was investigated. VII-8 is inactive towards butadiene but undergoes an oxidative cyclization with tetrachloro-o-benzoquinone to give a tetragermanium derivative. VII-8 undergoes oxidation addition of CH3I and PhI, followed by an unusual migration of the Me and Ph groups from germanium to the carbene ligand. Related chemistry takes place upon protonation with dry HCl, which results in the migration of the hydride to the carbene ligand.
    • Synthesis of Cyclopropenium-Appended Organocatalysts and Applications

      Smajlagic, Ivor; Department of Chemistry
      Enclosed within this dissertation is the development and application of multiple cyclopropenium-containing compounds formally belonging to two closely-related classes of organocatalysts, namely thioureas and squaramides. The former catalyst, coined as a thiourea-cyclopropenium, is deployed in pyranylation reactions of alcohols and phenols, as well as Friedel–Crafts alkylation, while the latter—a squaramide-cyclopropenium catalyst—targets oxime ether bond formation. Accompanying these innovative synthetic methodologies are comprehensive experimental and computational mechanistic studies that work in synergy to delineate numerous key features, all of which provide valuable information with respect to understanding the multifaceted nature of catalysis. Experimental and spectral data are provided for all new compounds.
    • Synthesis of unnatural analogues of pancratistatin and narciclasine

      Vshyvenko, Sergey; Department of Chemistry (Brock University, 2014-05-07)
      Described herein is the chemoenzymatic synthesis of several different types of unnatural analogues of Amaryllidaceae constituents. Development and refinement of existing and design and execution of new approaches towards the synthesis of C-1 analogues of pancratistatin and A-ring heterocyclic analogues of narciclasine are discussed. Evaluation of the new analogues as cancer growth inhibitory agents is also described
    • TA tales : [re]storying the teaching and learning experiences of university teaching assistants

      Grose, Jill D.; Department of Graduate and Undergraduate Studies in Education (Brock University, 2012-04-04)
      This inquiry examines reported critical incidents that shaped the lived experience of 5 university TAs as they negotiated multiple roles and relationships within the teaching and learning context. Questions and ensuing conversations explore the ways in which these critical incidents in teaching contributed to the TAs' understanding of themselves as teachers, of teaching and learning tensions in higher education, and of the institutional contexts in which they work. The inquiry also explores the ways in which narrative, particularly creative fiction, can represent the stories TAs tell of their experiences.
    • Talking during class, packing up books and name calling: Is it really that big a deal? An exploration of classroom incivility

      Spadafora, Natalie; Department of Child and Youth Studies
      The main goal of my dissertation was to explore and expand our understanding of the concept of adolescent classroom incivility. Specifically, I wanted to expand the current research on classroom incivility in children and youth using a range of methods. Methods comprised validating a measure of engagement in uncivil behavior, including open-ended responses to understand the experiences and viewpoints of both adolescent students and their teachers and exploring social network position in relation to engaging in classroom incivility. In Study 1, I validated a scale of uncivil behavior in the classroom. This validation confirmed subscales of intentional and unintentional classroom incivility in adolescents. This study also assessed construct validity via the examination of associations between classroom incivility with self- and peer-reported behavior and mental health correlates. As well, I investigated differential personality profiles of adolescents who reported engaging in intentional vs. unintentional uncivil behavior. Study 2 focused on comparing and contrasting the perceptions and experiences of classroom incivility of middle and high school teachers and students. This study used both quantitative reporting and qualitative methods to investigate how middle and high school teachers were experiencing and understanding classroom incivility compared to students. The results of this study indicated that there were differences in how uncivil behaviors were being perceived by students and teachers, depending on the classroom or individual circumstances. Finally, Study 3 was an exploratory study that investigated the association between social network position and self-reported engagement in classroom incivility. Results indicated a curvilinear association between social network position and classroom incivility, such that students who engaged in the highest or lowest levels of classroom incivility had lower social network position, while students who engaged in moderate levels of classroom incivility had the highest levels of social network position. Taken together, these studies have expanded our knowledge and understanding of adolescent classroom incivility. These results can inform intervention of uncivil behavior in the classroom and have highlighted the importance of limiting uncivil behavior in adolescence in an effort to promote a civil society.
    • Tea types and their effects on in vitro mineralization and in vivo bone structure and density

      McAlpine, Michael D.; Applied Health Sciences Program
      The consumption of tea has many proposed health benefits thought to likely be the result of an abundance of unique polyphenols. In particular, one exciting potential health benefit of tea is its capacity to have bone supportive effects when consumed throughout life. Prior to testing the potential bone supportive effects, it was important to characterize several types of tea and determine the ideal steeping time for each tea, maximizing the quantity of polyphenols while also maintaining taste (Study 1). Results from this study were congruent with manufacturer’s recommendations. Following this, several types of teas and tisanes were tested in an in vitro osteoblast model to determine if there were any alterations in quantity of mineral produced (Study 2). Findings demonstrated that all teas effectively increased mineralization at a dietary concentration of polyphenols, but red rooibos tea appeared to produce the greatest effects. The next important aspect which needed to be clarified was if there was an optimal concentration of red rooibos tea that elicited maximal results (Study 3). To determine this, a dose response study was conducted in the same osteoblast model as study 2 and mineral quantity was measured. From this study a positive dose-dependent response was observed without any signs of toxicity, suggesting that high concentrations may be beneficial. Following the initial in vitro studies it was important to test red rooibos tea in a physiologically relevant model of elevated bone turnover, pregnancy and lactation (Study 4). Female Sprague-Dawley rats were randomized to one of the following groups: PREG TEA (pregnant and received a supplemental level of red rooibos: ~2.6 g /kg body weight/day in water), PREG WATER (became pregnant and received water), or NONPREG CON (age-matched, non-pregnant control) from 2 weeks prior to pregnancy (age 8 weeks) through to 4 months post-lactation. Results demonstrated that there were immediate losses of both trabecular and cortical bone following lactation. However, cortical bone rapidly recovered in both pregnancy groups while the majority of trabecular outcomes only partially recovered and appeared to have permanent reductions. When comparing the two pregnancy groups, there were no differences in cortical bone post-lactation but there were significant improvements in several of the trabecular outcomes in rats that received red rooibos herbal tea. The findings from this thesis demonstrated in progressively more complex and physiologically relevant models that tea does have the capacity to be bone supportive, particularly during periods of high turnover.
    • Teachers Without Borders: Exploring Experiences, Transitions, and Identities of Refugee Women Teachers from Yugoslavia

      Ratkovic, Snezana; Department of Graduate and Undergraduate Studies in Education (Brock University, 2014-03-20)
      Prior to September 11 2011, Canada was recognized as a leading advocate of international refugee protection and the third largest settlement country in the world. University educated refugees were admitted to the country in part on the basis of their education, but once in Canada their credentials were often ignored. The purpose of this study was to explore, through a transnational feminist lens, immigrant and settlement experiences of refugee female teachers from Yugoslavia who immigrated to Canada during and after the Yugoslav wars; to document the ways in which socially constructed categories such as gender, race, and refugee status have influenced their post-exile experiences and identities; and to identify the government's role in creating conditions where the women were either able or unable to continue in their profession. In this study, I employed both a transnational feminist methodology and narrative inquiry. The analysis process included an emphasis on the storying stories model, poetic transcription, and concentric storying. The women’s voices are represented in various forms throughout the document including individual and collective narratives. Each narrative contributed to a detailed picture of immigration and settlement processes as women spoke of continuing their education, knowing or learning the official language, and contributing to Canadian society and the economy. The findings challenge the image of a victimized and submissive refugee woman, and bring to the centre of discourse the image of the refugee woman as a skilled professional who often remains un- or underemployed in her new country. The dissertation makes an important contribution to an underdeveloped area in the research literature, and has the potential to inform immigration, settlement, and teacher education policies and practices in Canada and elsewhere.
    • Teachers’ Experiences of Implementing a Pedagogical Approach for Meaningful Physical Education

      Beni, Stephanie; Applied Health Sciences Program
      Dominant forms of physical education (PE) have been criticized for their inability to promote lifelong movement, with many scholars arguing in favour of an approach oriented toward meaningful experiences in PE. The Meaningful PE approach has been designed in response to this but has yet to be tested extensively in practice. The purpose of this dissertation has been to study teachers’ experiences of learning about and implementing the Meaningful PE approach. Five teachers based in Ireland and 12 teachers based in Canada participated in two separate studies lasting eight weeks and across two school years, respectively. Qualitative data were collected in the form of semi-structured interviews, non-participant observations, community of practice (CoP) meeting transcripts, and reflections. Results of this dissertation are presented in four articles. Article One highlights the experiences of Irish primary classroom teachers, demonstrating preliminary support for the approach from classroom teachers with little background in PE. Article Two focuses on Canadian elementary teachers’ experiences of implementing the Meaningful PE approach with their students and on the factors that influenced their implementation decisions. Primary factors influencing implementation included teachers’ prior experiences and beliefs, students’ responses to the implementation process, and external organizational pressures. Article Three focuses on Canadian teachers’ experiences of learning about Meaningful PE through a professional (PD) initiative designed around characteristics of effective PD outlined in the literature. Teachers were most supportive of the use of a CoP and modelling of the approach to foster their learning about Meaningful PE, while also highlighting several tensions between ideal and practical forms of PD, taking personal and organizational barriers into account. Article Four focuses on my experience of becoming a facilitator of teachers’ PD through facilitating a CoP for teachers. This article highlights the important role of identity in the process of learning to become a facilitator and navigating the tensions associated with that process. Collectively, this dissertation makes a significant contribution to the literature by a) informing the refinement of the Meaningful PE approach, b) offering insights into educational implementation research, and c) adding to the literature on teachers’ professional learning when being introduced to innovations.
    • Teaching Learners of English as an Additional Language: Re-Conceptualizing Mainstream Teacher Preparedness in the Growing Linguistic Mosaic of Ontario

      Lee, Nina; Department of Graduate and Undergraduate Studies in Education
      As the population of Learners of English as an Additional Language (LEALs) has increased steadily in mainstream classrooms over the last decade, mainstream classroom teachers are challenged with teaching situations for which they are not adequately prepared. Using a Complexity Theory and Mindfulness Mindset lens, this study examined self-perceived preparedness of 15 recently graduated teachers over the course of a 10-workshop series titled Teaching LEALs in Mainstream Classrooms. The following research questions guided the study: (a) How do teachers’ perceptions of their preparedness to teach LEALs change during the workshop series? (b) How did the workshops contribute to changes in teachers’ perceptions? Through datasets created from observational field notes, questionnaires, and semi-structured interview, workshop, and session documentation, this semester-long qualitative case study presents mainstream teachers’ experiences and perceptions. Rather than providing a detailed and prescribed curriculum for change, attention is on the overall direction of teacher preparedness and fostering conditions for change and learning. Study findings capture the intricacies of mainstream teacher preparedness and indicate that change depends on adequate professional development that maximizes teachers’ LEAL-related knowledge. However, in addition to knowledge, self-perceived levels of preparedness were influenced by the discomfort of disequilibrium, feedback, and embracing uncertainty. There are important implications for teacher education practice and professional certification. Ultimately, mainstream teacher training for LEALs cannot be optional. All teachers require targeted and intentional training to effectively address barriers to LEAL teaching and learning.
    • Testing a Hypothesis of Non-REM Sleep Reinforcement and REM Sleep Refinement for the Benefits of Post-Learning Sleep on Memory Retrieval

      MacDonald, Kevin John; Department of Psychology
      It is well established that post-learning sleep benefits later memory retrieval, but there is still much to learn about the processes involved and the nature of these benefits. Sleep is composed of stages of non-REM (NREM) and REM sleep: NREM sleep, especially slow wave activity of NREM sleep, and REM sleep have been implicated in memory performance benefits, but the specific contributions of each state remain unclear. This thesis presents a hypothesis proposing that post-learning NREM sleep supports memory accessibility, benefitting the likelihood of successful memory retrieval, and that post-learning REM sleep supports memory fidelity, allowing for more accurate retrieval when retrieval is successful. This hypothesis was tested over studies examining the effects of an afternoon nap (Chapter 2), targeted memory reactivation during NREM slow wave sleep (Chapter 3), and both targeted memory reactivation during NREM slow wave sleep and selective deprivation of REM sleep (Chapter 4) on measures of memory accessibility and memory fidelity in visuospatial memory tasks. In each study, measures of sleep architecture and electroencephalographic power in sleep were examined as predictors of memory performance. Several identified associations and interactions further inform an understanding of how NREM sleep and REM sleep may benefit memory performance. Most notably, these studies consistently found greater slow wave activity of NREM sleep to be specifically associated with better maintenance of memory accessibility. These studies did not identify a clear effect of REM sleep. It is hoped that the hypothesis and findings presented stimulate additional inquires that will further our understanding of the individual and combined contributions of NREM and REM sleep.
    • Tetrathiafulvalene and 2,2'-Bipyridine: Bridging both Worlds in the Pursuit of Novel Molecular Materials

      Gumbau-Brisa, Roger; Department of Chemistry (Brock University, 2013-04-04)
      The preparation and characterization of two families of building blocks for molecule-based magnetic and conducting materials are described in three projects. In the first project the synthesis and characterization of three bis-imine ligands LI - L3 is reported. Coordination of LI to a series of metal salts afforded the five novel coordination complexes Sn(L4)C4 (I), [Mn(L4)(u-CI)(CI)(EtOH)h (II), [CU(L4)(u-sal) h(CI04)2 (sal = salicylaldehyde anion) (III), [Fe(Ls)2]CI (IV) and [Fe(LI)h(u-O) (V). All complexes have been structurally and magnetically characterized. X-ray diffraction studies revealed that, upon coordination to Lewis acidic metal salts, the imine bonds of LI are susceptible to nucleophilic attack. As a consequence, the coordination complexes (I) - (IV) contain either the cyclised ligand L4 or hydrolysed ligand Ls. In contrast, the dimeric Fe3+ complex (V) comprises two intact ligand LI molecules. In. this complex, the ligand chelates two Fe(III) centres in a bis-bidentate manner through the lone pairs of a phenoxy oxygen and an imine nitrogen atom. Magnetic studies of complexes (II-V) indicate that the dominant interactions between neighbouring metal centres in all of the complexes are antiferromagnetic. In the second project the synthesis and characterization two families of TTF donors, namely the cyano aryl compounds (VI) - (XI) and the his-aryl TTF derivatives (XII) - (XIV) are reported. The crystal structures of compounds (VI), (VII), (IX) and (XII) exhibit regular stacks comprising of neutral donors. The UV -Vis spectra of compounds (VI) - (XIV) present an leT band, indicative of the transfer of electron density from the TTF donors to the aryl acceptor molecules. Chemical oxidation of donors (VI), (VII), (IX) and (XII) with iodine afforded a series of CT salts that where possible have been characterized by single crystal X -ray diffraction. Structural studies showed that the radical cations in these salts are organized in stacks comprising of dimers of oxidized TTF donors. All four salts behave as semiconductors, displaying room temperature conductivities ranging from 1.852 x 10-7 to 9.620 X 10-3 Scm-I. A second series of CT salts were successfully prepared via the technique of electrocrystallization. Following this methodology, single crystals of two CT salts were obtained. The single crystal X-ray structures of both salts are isostructural, displaying stacks formed by trimers of oxidized donors. Variable temperature conductivity measurements carried out on this series of CT salts reveal they also are semiconductors with conductivities ranging from 2.94 x 10-7 to 1.960 X 10-3 S em-I at room temperature. In the third project the synthesis and characterization of a series of MII(hfac)2 coordination complexes of donor ligand (XII) where M2+ = Co2+, Cu2+, Ni2+ and Zn2+ are reported. These complexes crystallize in a head-to-tail arrangement of TTF donor and bipyridine moieties, placing the metal centres and hfac ligands are located outside the stacks. Magnetic studies of the complexes (XV) - (XVIII) indicate that the bulky hfac ligands prevent neighbouring metal centres from assembling in close proximity, and thus they are magnetically isolated.
    • Theory and Application of a Pure-sampling Quantum Monte Carlo Algorithm

      Ospadov, Egor; Department of Physics
      The objective of pure-sampling quantum Monte Carlo is to calculate physical properties that are independent of the importance sampling function being employed in the calculation, save for the mismatch of its nodal hypersurface with that of the exact wave function. To achieve this objective, we describe a pure-sampling algorithm that combines features of forward-walking methods of pure-sampling and reptation quantum Monte Carlo. The importance sampling is performed by using a single-determinant basis set composed of Slater-type orbitals. We implement our algorithm by systematically increasing an algorithmic parameter until the properties sampled from the electron distributions converge to statistically equivalent values, extrapolated in the limit of zero time-step. In doing so, we are able to unambiguously determine the values for the ground-state fixed-node energies and one-electron properties of various molecules. These quantities are free from importance sampling bias, population control bias, time-step bias, extrapolation-model bias, and the finite-field approximation. We applied our algorithm to the ground-states of lithium hydride, water and ethylene molecules, and found excellent agreement with the accepted literature values for the energy and a variety of other properties for those systems. Some of our one-electron properties of ethylene had not been calculated before at any level of theory. In a detailed comparison, we found reptation quantum Monte Carlo, our closest competitor, to be less efficient by at least a factor of two. It requires different sets of time-steps to accurately determine the ground-state energy and one-electron properties, whereas our algorithm can achieve the same objective by using a single set of time-step values.
    • Thermal tasting: methodological considerations and implications for alcohol behaviour.

      Thibodeau, Margaret; Department of Biological Sciences
      Thermal tasting is a phenomenon whereby some individuals perceive thermally-induced taste sensations when their tongue is warmed or cooled. These individuals, known as thermal tasters (TT), report a variety of thermally-induced tastes and the tastes reported can vary with temperature regime used and location on the tongue tested. TT are typically compared to thermal non-tasters (TnT), individuals who do not experience thermally-induced sensations. The literature suggests that TT give higher intensity ratings to orosensory stimuli than TnT; however, small sample sizes and differences in classification schemes between studies confound our understanding of TTS (thermal taste status). It is unknown whether the increased orosensory responsiveness of TT is universal or whether it is driven by a subgroup of TT. Furthermore, up to 50% of individuals are non-classifiable (NC). The largest database of individuals who have undergone TTS screening was compiled to address the literature gaps. Findings indicate that TT are more responsive than TnT to orosensory stimuli, regardless of the classification scheme used. The orosensory responsiveness of NC is not homogeneous, suggesting that NC are not a separate group but rather misclassified TT and TnT. Sweet TT are more likely than non-sweet TT to experience thermally-induced sensations during lingual warming. Similarly, sour TT are more likely than non-sour TT to report thermally-induced tastes during cooling. However, no differences in orosensory responsiveness based on these or other subgroups are identified, suggesting that the heightened orosensory responsiveness of TT is universal across this phenotype. The final study sought to characterize the binary interactions between ethanol and four orosensory stimuli (fructose, quinine, tartaric acid and alum sulphate) both overall and by comparing TT and TnT. In general, TT are more responsive than TnT to all stimuli in the study. Few interactions between TTS and stimulus intensity exist suggesting that TT and TnT perceive the sensations elicited by alcoholic beverages similarly, albeit at different intensities. Together, the thesis helps inform best practices for TTS screening and classification, provides insights into TTS mechanisms and furthers our understanding of alcoholic beverage perception.
    • Top-down and Bottom-up influences on ACC activation: Evaluation of a proposed model of the feedback-related negativity

      Dzyundzyak, Angela; Department of Psychology (Brock University, 2014-07-18)
      The Feedback-Related Negativity (FRN) is thought to reflect the dopaminergic prediction error signal from the subcortical areas to the ACC (i.e., a bottom-up signal). Two studies were conducted in order to test a new model of FRN generation, which includes direct modulating influences of medial PFC (i.e., top-down signals) on the ACC at the time of the FRN. Study 1 examined the effects of one’s sense of control (top-down) and of informative cues (bottom-up) on the FRN measures. In Study 2, sense of control and instruction-based (top-down) and probability-based expectations (bottom-up) were manipulated to test the proposed model. The results suggest that any influences of medial PFC on the activity of the ACC that occur in the context of incentive tasks are not direct. The FRN was shown to be sensitive to salient stimulus characteristics. The results of this dissertation partially support the reinforcement learning theory, in that the FRN is a marker for prediction error signal from subcortical areas. However, the pattern of results outlined here suggests that prediction errors are based on salient stimulus characteristics and are not reward specific. A second goal of this dissertation was to examine whether ACC activity, measured through the FRN, is altered in individuals at-risk for problem-gambling behaviour (PG). Individuals in this group were more sensitive to the valence of the outcome in a gambling task compared to not at-risk individuals, suggesting that gambling contexts increase the sensitivity of the reward system to valence of the outcome in individuals at risk for PG. Furthermore, at-risk participants showed an increased sensitivity to reward characteristics and a decreased response to loss outcomes. This contrasts with those not at risk whose FRNs were sensitive to losses. As the results did not replicate previous research showing attenuated FRNs in pathological gamblers, it is likely that the size and time of the FRN does not change gradually with increasing risk of maladaptive behaviour. Instead, changes in ACC activity reflected by the FRN in general can be observed only after behaviour becomes clinically maladaptive or through comparison between different types of gain/loss outcomes.
    • Towards reverse engineering of Photosystem II: Synergistic Computational and Experimental Approaches

      Mahboob, Abdullah; Centre for Biotechnology (Brock University, 2014-10-01)
      ABSTRACT Photosystem II (PSII) of oxygenic photosynthesis has the unique ability to photochemically oxidize water, extracting electrons from water to result in the evolution of oxygen gas while depositing these electrons to the rest of the photosynthetic machinery which in turn reduces CO2 to carbohydrate molecules acting as fuel for the cell. Unfortunately, native PSII is unstable and not suitable to be used in industrial applications. Consequently, there is a need to reverse-engineer the water oxidation photochemical reactions of PSII using solution-stable proteins. But what does it take to reverse-engineer PSII’s reactions? PSII has the pigment with the highest oxidation potential in nature known as P680. The high oxidation of P680 is in fact the driving force for water oxidation. P680 is made up of a chlorophyll a dimer embedded inside the relatively hydrophobic transmembrane environment of PSII. In this thesis, the electrostatic factors contributing to the high oxidation potential of P680 are described. PSII oxidizes water in a specialized metal cluster known as the Oxygen Evolving Complex (OEC). The pathways that water can take to enter the relatively hydrophobic region of PSII are described as well. A previous attempt to reverse engineer PSII’s reactions using the protein scaffold of E. coli’s Bacterioferritin (BFR) existed. The oxidation potential of the pigment used for the BFR ‘reaction centre’ was measured and the protein effects calculated in a similar fashion to how P680 potentials were calculated in PSII. The BFR-RC’s pigment oxidation potential was found to be 0.57 V, too low to oxidize water or tyrosine like PSII. We suggest that the observed tyrosine oxidation in BRF-RC could be driven by the ZnCe6 di-cation. In order to increase the efficiency of iii tyrosine oxidation, and ultimately oxidize water, the first potential of ZnCe6 would have to attain a value in excess of 0.8 V. The results were used to develop a second generation of BFR-RC using a high oxidation pigment. The hypervalent phosphorous porphyrin forms a radical pair that can be observed using Transient Electron Paramagnetic Resonance (TR-EPR). Finally, the results from this thesis are discussed in light of the development of solar fuel producing systems.
    • Trading nitrogen for carbon: Nitrogen and carbon translocation in a plant/fungal (Metarhizium spp.) symbiosis

      Behie, Scott William; Centre for Biotechnology
      While nitrogen is critical for all plants, they are unable to utilize organically bound nitrogen in soils. Therefore, the majority of plants obtain useable nitrogen through nitrogen fixing bacteria and the microbial decomposition of organic matter. In the majority of cases, symbiotic microorganisms directly furnish plant roots with inorganic forms of nitrogen. More than 80% of all land plants form intimate symbiotic relationships with root colonizing fungi. These common plant/fungal interactions have been defined largely through nutrient exchange, where the plant receives limiting soil nutrients, such as nitrogen, in exchange for plant derived carbon. Fungal endophytes are common plant colonizers. A number of these fungal species have a dual life cycle, meaning that they are not solely plant colonizers, but also saprophytes, insect pathogens, or plant pathogens. By using 15N labeled, Metarhizium infected, wax moth larvae (Galleria mellonella) in soil microcosms, I demonstrated that the common endophytic, insect pathogenic fungi Metarhizium spp. are able to infect living soil borne insects, and subsequently colonize plant roots and furnish ts plant host with useable, insect-derived nitrogen. In addition, I showed that another ecologically important, endophytic, insect pathogenic fungi, Beauveria bassiana, is able to transfer insect-derived nitrogen to its plant host. I demonstrated that these relationships between various plant species and endophytic, insect pathogenic fungi help to improve overall plant health. By using 13C-labeled CO2, added to airtight plant growth chambers, coupled with nuclear magnetic resosnance spectroscopy, I was able to track the movement of carbon from the atmosphere, into the plant, and finally into the root colonized fungal biomass. This indicates that Metarhizium exists in a symbiotic partnership with plants, where insect nitrogen is exchanged for plant carbon. Overall these studies provide the first evidence of nutrient exchange between an insect pathogenic fungus and plants, a relationship that has potentially useful implications on plant primary production, soil health, and overall ecosystem stability.
    • Transmission Dynamics and Epidemiology of West Nile Virus in Ontario, Canada

      Giordano, Bryan; Centre for Biotechnology
      The resurgence of West Nile virus (WNV; Family Flaviviridae, genus Flavivirus) in Ontario, Canada in 2012 demonstrated that there is a great need for a reassessment of the local mosquito fauna, estimation of risk of WNV transmission, and the creation of effective arboviral awareness campaigns. A review of the current literature and collection databases revealed that there are 68 mosquito species known from Ontario (Chapter 2). Ten species were added to the list of species including Culex erraticus (Chapter 3) and Aedes albopictus (Chapter 4), both of which are capable of transmitting West Nile virus. Ae. albopictus was repeatedly collected from Windsor, Ontario in 2016 (Chapter 4). Immatures (n=78) were collected from tires, StyrofoamTM containers, and discarded garbage. Adult female (n=17) and male (n=2) specimens were collected from light traps (n=7) and Biogents-Sentinel traps (n=10). Additional specimens were obtained from Franklin County, Ohio. The generated gene tree and Bayesian cluster analysis grouped sequences described from Ohio and Windsor together on the same branches. Together these data suggest that the population in Windsor originated as a founder population of North American origin by means of human-aided dispersal. Mosquito abundance predication surfaces and seasonal distributions were attempted for each vector species to identify where and when vector species are most abundant in southern Ontario (Chapter 5). Spatial prediction surfaces using kriging were created for Aedes vexans, Aedes japonicus, Culex pipiens, Culex restuans, and Ochlerotatus trivittatus. Proximity to landscape variables was observed to improve model prediction. An epidemiological analysis of WNV human case prevalence and mosquito infection was conducted (Chapter 6). A strong quadratic relationship between the number of human cases and positive mosquito pools at the end of each year was observed (R2=0.9783, p < 0.001). Spearman rank correlation tests identified mosquito infection rates as the strongest predictors of human case prevalence at a one-week lag period. Average temperature was a strong predictor of mosquito infection rates. Cumulative positive Culex pools recorded by epidemiological week 34 is a sufficient action threshold for West Nile virus epidemics. These data have the potential to contribute to a more efficient West Nile virus awareness campaign.
    • Trends Shaping Education and Innovative Learning Environments: A Discourse Analysis of OECD CERI Projects

      Rigas, Bob; Department of Graduate and Undergraduate Studies in Education
      The Organization for Economic Co-operation and Development (OECD) was created in 1960 to advance economic expansion and world trade. Although it lacks a specific mandate for education, it has shaped national educational policy through the dissemination of ideas and transnational research. The Centre for Educational Research and Innovation (CERI), a branch of the OECD, was created in 1968. Its potential influence on the educational policy of nation states suggests a need to investigate its vision for K-12 education. The purpose of this research was to critically analyse two major projects undertaken by CERI: Trends Shaping Education and Innovative Learning Environments, with respect to the nature of their embedded political discourse, as well as their constructions of K-12 schooling, teachers, and learners. Additionally, it critically explored how the discourse of innovation, accountability, and governance shapes education in particular ways. Drawing from Fairclough’s methods of critical discourse analysis (CDA), as adapted by Grewal, it examined the ideological and discursive nature of the CERI projects. Texts were interpreted through a liberal theoretical framework. Findings suggest the CERI Projects frame a neoliberal vision for K-12 education focussed primarily on economic ends. Although the social dimension of education is recognized with respect to its need to foster equity, equality and social cohesion, its discourse is best characterized as a form of flanking and roll-out neoliberalism. Both Projects embrace a human capital approach to education and advance a neoliberal subjectivity in which learners are defined by their economic utility and are framed as future workers who are flexible, adaptable, resilient, responsible, innovative, entrepreneurial, and good problem solvers. The ILE Project’s promotion of networks and partnerships with other sectors and business reflects a transition away from government to governance as promoted by New Public Governance, which also reflects a neoliberal orientation. In both Projects, innovation, accountability, and governance are nominalizations that reinforce a neoliberal policy perspective of education.