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Quantum Optical Metrology Using Two-Photon Interference
No full textOptical quantum metrology uses specially-prepared states of light to probe sensitive samples. Choosing a suitable probe state allows one to extract more information per probe photon about an unknown parameter than is possible using any classical technique. In effect, these techniques improve the sensitivity of the measurement whenever the number of probe photons is constrained in some way.
This thesis presents experimental and theoretical results on the use of pairs of time-frequency entangled photons in precision measurements. It begins with an overview of necessary background knowledge about quantum optics and quantum information. This is followed by a theoretical discussion on the estimation of a single delay using two-photon interference. We show that constraints on the probe photon's bandwidth complicate the measurement problem, requiring suitable optimization of the two-photon quantum state to avoid losing precision.
We then consider the use of two-photon interference for linear spectroscopic measurements. Linear spectroscopy relates the absorption and phase spectrum of a sample to unknown electronic parameters. We describe a proof-of-principle experiment demonstrating that two-photon interferometric spectroscopy can be used for simultaneously measurement of both absorption and phase. This is followed by an information-theoretic discussion of the precision of this technique. For low losses, we show that the method provides phase sensitivity similar to classical interferometry while approaching the optimal absorption precision of any possible measurement. If the absorption and phase values are both related to a single unknown parameter, then our technique provides improved sensitivity to this parameter compared to both classical measurements and other quantum techniques in the presence of realistic levels of loss.
We conclude with a discussion of quantum-optical coherence tomography, which is a two-photon interferometric method for determining the material structure of a sample. We present an ongoing experiment which aims to apply the method to tissue-like samples, where the quantum measurement is limited by a poor signal-to-noise ratio. Preliminary results demonstrate that this noise can be largely reduced by suitable frequency-domain filtering. This allows us to precisely determine the position of a scattering center using a few hundred detected photon pairs despite the presence of large amounts of noise. We follow this with a theoretical discussion of signal artifacts which are known to complicate the measured interferogram. We show these artifacts are due to a distinct interferometric effect, which can be distinguished from the signal of interest using the relative time delay between detected photons. We conclude with a brief discussion on possible techniques for artifact removal
How Neural Dynamics Shape Thought Dimensions
No full textBackground:
Spontaneous thought, particularly exemplified by mind-wandering, is characterized by a complex and multidimensional structure. This structure spans several dimensions: (1) task-relatedness (on-task vs. off-task), (2) thought content quantity (single vs. multiple), (3) thought orientation (externally vs. internally oriented), and (4) deliberate control (deliberate vs. spontaneous). While previous research has investigated these dimensions individually, a comprehensive neurodynamic framework integrating their cognitive and neural mechanisms remains lacking.
Aims and Hypotheses:
This thesis aims to examine the neural underpinnings of spontaneous thought through cognitive testing and electroencephalography (EEG), identifying distinct neural markers for each dimension and exploring their interrelationships. It is hypothesized that:
1. Alpha and theta oscillations will track task-relatedness and thought content quantity,
2. Task-relatedness and thought orientation will be distinguishable through neural and behavioral timescales, with task-relatedness operating on a shorter timescale than thought orientation.
3. Task-relatedness and deliberate control are tightly linked, with on-task thoughts typically being deliberate and off-task thoughts being spontaneous. Pre-stimulus neural oscillatory phase measures will predict post-stimulus task-related behaviors.
Methods:
Three EEG studies were conducted to examine these hypotheses. Study 1 analyzed the relationship between task-relatedness and thought content quantity using EEG measures of alpha and theta peak frequency sliding. Study 2 investigated task-relatedness and thought orientation by comparing their neural and behavioral timescales. Study 3 explored the interaction between task-relatedness and deliberate control, using phase-based neural markers such as peak frequency sliding, sample entropy, and inter-trial phase coherence.
Results:
Study 1 revealed that alpha and theta FS tracked task-relatedness and thought content quantity, with increased alpha FS associated with on-task, single-content thoughts and increased theta FS with off-task, multiple-content thoughts. Study 2 found that task-relatedness operates on a shorter timescale than thought orientation at both neural and behavioral levels. Study 3 demonstrated a strong link between task-relatedness and deliberate control, where on-task thoughts were typically deliberate and off-task thoughts were spontaneous. Furthermore, pre-stimulus neural oscillatory phase measures predicted post-stimulus task-related behaviors.
Conclusion:
These findings provide empirical support for the multidimensional nature of spontaneous thought and highlight distinct neural markers for each dimension. By integrating cognitive and neurophysiological evidence, this thesis establishes a neurodynamic framework for spontaneous thought, offering novel insights into the study of thought
On-the-ground realities of health program delivery in addressing community needs: a community-based participatory research approach in the moose Cree First Nation
No full textAbstract Background It has been well documented that Indigenous people in northern remote communities in Canada continue to experience a disproportionate burden of health disparities due to complex interactions of multiple determinants of health, including food insecurity, colonialism, barriers in accessing primary healthcare, and disrupted socioeconomic and political structures. Health promotion programs are essential in building preventive measures and empowering communities to take control over their health by helping them make informed health choices. This study described Indigenous-led nutrition-related health programs, the Healthy Babies, Healthy Children Program (HBHCP) and the Diabetes Prevention Program (DPP), which respond to food insecurity drivers and support community needs in Moose Cree First Nation (MCFN). It also documented the on-the-ground realities of program delivery and highlighted community-informed priorities for improved programming. Methods Grounded in community-based participatory research (CBPR) principles, our approach emphasized the importance of community engagement in supporting the healing process within this cultural context. Data collection included first-hand participation in program delivery alongside program coordinators, participant feedback, and semi-structured interviews from community members (n = 6) and Health Center staff (n = 3). Thematic analysis was used to identify themes across interview data, field notes, and community feedback. Results High food costs, limited access and availability, and poor food quality remain the primary food-related challenges experienced in the community. Health programs serve as frontline responders to community needs and address these challenges through culturally grounded and family-oriented nutrition education activities. Community members valued the programs’ knowledge-sharing approaches, tangible support, and social connections. However, systemic barriers significantly constrain program delivery, including inadequate funding, limited resources, staffing shortages, and the impact of COVID-19. These barriers limited the programs’ capacity to reach their full potential, despite strong community resilience. Conclusion Indigenous-led nutrition programs are vital in addressing food insecurity and promoting health in northern communities. The findings underscore the need for sustainable funding and stronger policy support that reflects the true cost of service delivery in remote Indigenous communities. The findings emphasize the need for policy changes that move beyond top-down approaches toward community-informed policies and Indigenous-led health programming
Spoon-taneous Thoughts: A New Perspective on Children's Episodic Future Thinking as Measured Through Spontaneous Behaviour
No full textEpisodic future thinking (EFT) allows us to mentally project ourselves forward in time, guiding present actions based on future goals and desired outcomes. While adults regularly engage in such future-oriented behaviour of their own volition, it is less clear to what extent children do the same. This uncertainty stems from a reliance on experimenter-prompted tasks in developmental research, which limits our understanding of children's independent, self-initiated EFT. This dissertation addresses that gap by investigating how children spontaneously engage in future thinking through unprompted, volitional behaviours.
Study 1 introduced a novel experimental paradigm to examine spontaneous preparation for a future event among 4- to 9-year-olds. Findings showed that most children aged five and older prepared spontaneously, while most four-year-olds did not (74%). Notably, executive functioning was not correlated with spontaneous performance, but was correlated with prompted performance, suggesting these behaviours may be supported by distinct cognitive processes.
Study 2 used a naturalistic, parent-report approach to examine the functionality of children's spontaneous future-oriented statements and actions in everyday life. A thematic analysis revealed four key functions: Future-oriented information seeking, Expressing future desires or intentions, Connecting present actions to future outcomes, and Predicting future mental or physiological states. These findings suggest future-oriented information seeking may be a function of future thinking that is unique to childhood.
Study 3 adapted the methodology from Study 2 to a larger sample size and identified five overlapping themes: Future-oriented information seeking, Expressing future desires or intentions, Preparing for the future, Predicting the future, and Optimizing the future. Study 3 also explored what triggered children's spontaneous future-oriented behaviour, with findings suggesting that most instances were internally cued and had been previously observed.
Together, these studies highlight an important and underexplored area of children's cognitive development. They also provide novel, replicable methodologies for investigating spontaneous EFT, opening avenues for future research about how young children use their future thinking in self-directed and everyday contexts
The Role of PARylation in Inflammatory Mediated Subclass of Preeclampsia
No full textPreeclampsia (PE) is a leading cause of maternal and neonatal morbidity and mortality, diagnosed after 20 weeks of gestation. Several subclasses of PE have been identified, each with distinct pathophysiology. Notably, the inflammation-mediated subclass (I-PE) is characterized by a pronounced increase in placental PARylation and a marked depletion of NAD+. This study investigates the mechanistic basis of this phenotype by profiling placental NAD+ -consuming enzymes and assessing whether selective inhibition of PARylating enzymes can restore trophoblast function and placenta health. HTR-8/SVneo trophoblast cells were exposed to TNF-α to mimic the I-PE inflammatory environment in vitro. Cells were also co-treated with Olaparib (a PARP1/2 inhibitor) or XAV939 (a PARP5a/5b inhibitor), as PARP1/2 and PARP5a/5b have been identified as key PARylating enzymes in the placenta. Total protein PARylation, cellular viability, mitochondrial func-on, and migratory capacity were assessed as cellular health and functional outcomes. TNF-α exposure increased total protein PARylation and impaired mitochondrial health by decreasing oxygen consumption rates during respiration, cellular viability and migration. Co- treatment with Olaparib reduced protein PARylation within 1h and restored cellular viability and migration, and mitochondrial respiration despite the continued pro-inflammatory conditions. In contrast, co-treatment with XAV939 showed no improvement in cellular health or function. These findings suggest that inflammation-induced PARP1/2 activation may contribute to placental PARylation and NAD+ depletion in I-PE and highlight the PARP1/2- NAD+ axis as a potential therapeutic target to improve placental health and func-on in affected pregnancies
Molecular Imaging of Dopaminergic Neurotransmission in Subclinical Paranoia
No full textElevated dopamine system function in the striatum is a hallmark of psychotic illness. However, the extent to which genetic risk factors contribute to striatal hyperdopaminergia remains largely unexplored. Here, we examined dopaminergic correlates of psychosis risk in those with and without a first-degree relative with psychosis. In the first study, we examined neuromelanin-sensitive magnetic resonance imaging (NM-MRI), which is a proxy of dopamine released over the lifespan and has been shown to be associated with positive symptoms in psychosis. We show that despite lack of a group difference in NM-MRI between those with and without a first-degree relative with psychosis, frequency of subclinical paranoid thought is associated with elevated NM-MRI in the dorsomedial substantia nigra and ventral tegmental area complex. In the second study, we examined task-based dopamine release in the same population using simultaneous [¹¹C]raclopride positron emission tomography (PET) and functional MRI (fMRI) during fear conditioning. First, we confirmed the validity of the PET/fMRI experiment to capture dopamine release during the fear conditioning task. We show that fear conditioning elicits dopamine release in the dorsoposterior striatum of humans, which for the first time, confirms fear-elicited dopamine release in the analogous rodent tail of the striatum. We then compared dopamine release during fear conditioning in those with and without a first-degree relative with psychosis. We report that dopamine release is blunted in the dorsoposterior striatum in those with a first-degree relative. Finally, we report that lack of dopamine release in the dorsoposterior striatum is associated with increased frequency of subclinical paranoid thought. We also show that poor recall of the CS+ is associated with increased frequency of subclinical paranoid thought. For the first time, our findings suggest a lack of adaptive dopamine release is associated with subclinical positive symptomatology. Altogether, these two studies demonstrate that a static measure of dopamine released over the lifespan may be associated with paranoid thought, but that this increased release may not be occurring at relevant times and that a lack of adaptive dopamine release may be also contributing to paranoia, a prominent positive symptom in psychosis
Vivre dans la dignité et le respect des capacités : une ethnographie institutionnelle auprès de personnes âgées hébergées vivant avec un trouble neurocognitif
No full textLe vieillissement de la population entraîne de nombreux questionnements quant à la qualité de vie des individus qui atteignent le grand âge. Ces derniers risquent de faire face à la perte d'autonomie et dans certains cas, au développement d'un trouble neurocognitif (TNC), une famille de conditions, incluant la maladie d'Alzheimer, qui est particulièrement crainte socialement. C'est entre autres en raison des représentations sociales funestes des TNC, dont la perte de la dignité, que se perpétue la stigmatisation de la condition. Lorsque nécessaire, les personnes qui vivent avec un TNC peuvent se voir « placées » dans un centre d'hébergement et de soins de longue durée (CHSLD). Au Québec, les CHSLD souffrent d'une piètre réputation depuis leur mise sur pied. Les enjeux systémiques y persistent, malgré les tentatives répétées d'y améliorer les conditions. Lors de la pandémie de COVID-19, ces milieux ont été ciblés par les foudres de la population. Perçus comme des mouroirs où s'éteint la dignité humaine, les CHSLD demeurent pourtant essentiels au fonctionnement de notre société telle qu'organisée actuellement. La présente thèse s'inscrit dans une ère postpandémique, où le « retour à la normale » n'est pas forcément souhaitable et le retour aux questions fondamentales est nécessaire. À travers une série d'articles, la présente thèse décrit une ethnographie institutionnelle déployée dans un CHSLD public québécois auprès de résident.e.s qui ont un TNC. L'observation participative non structurée (133h) et des entrevues non dirigées basées sur des loisirs (n=4) avec des résident.e.s qui ont un TNC ont permis de composer un corpus de données robuste. Nos résultats nous informent notamment sur le paradoxe des portées multiples du CHSLD (milieux de vie, de soins et de travail), les pratiques institutionnalisantes et les avenues d'humanisation et de maintien de la dignité en CHSLD. Notre projet fait également montre d'innovation sur le plan méthodologique auprès de la population concernée. Cette thèse soulève de nombreuses questions, tant sur le plan de la recherche que de la pratique et des politiques en matière de santé et de bien-être des personnes âgées qui ont un TNC. À son essence, cette dissertation fait réfléchir au rapport, en tant que société, que nous entretenons avec le vieil âge
Development of the Canadian Eating Practices Screener for Adolescents to assess eating practices based on Canada’s Food Guide 2019 recommendations
No full textAbstract Background In addition to guidance on food choices, the Canada’s Food Guide 2019 (CFG-2019) provides recommendations to support healthy eating habits. A brief self-administered eating practices questionnaire informed by CFG-2019 recommendations was recently developed and validated among adults, but no such measure is available for adolescents. The objective of this study was to develop and assess the content validity of a self-administered screener to measure eating practices based on CFG-2019 recommendations among English- and French-speaking adolescents aged 10 to 17 years. Methods Following a literature review of existing measures and the identification of guiding principles for questionnaire development, a 26-item draft screener was created. The content validity of the draft screener was assessed by an expert panel with expertise in nutrition, eating behaviours, public health and/or questionnaire validation (English n = 13, French n = 7) and through two rounds of cognitive interviews with adolescents (English n = 18, French n = 13). Results The number of items was reduced from 26 to 12 following review by the expert panel, and further reduced to 11 after the cognitive interviews with adolescents. Minor wording changes were made to improve clarity of a few items. Conclusions This study resulted in the development of the 11-item Canadian Eating Practices Screener for Adolescents/Questionnaire court canadien sur les pratiques alimentaires des adolescents designed for use among adolescents aged 10 to 17 years. Further work is needed to test the screener for construct validity and reliability. After which, this measure can be used for research and nutrition surveillance of eating practices among adolescents living in Canada
Decorin Role in Extracellular Vesicles Used to Prevent Post-Operative Atrial Fibrillation
No full textPostoperative atrial fibrillation (AF) affects one-third of patients following cardiac surgery, increasing the risk of stroke. Inflammation-driven atrial fibrosis contributes to postoperative AF. Our lab is investigating the use of extracellular vesicles (EVs) derived from human atrial explant cells to mitigate atrial fibrosis and prevent AF. While EVs have demonstrated protective effects, the underlying mechanisms remain incompletely understood. Recently, our proteomic analysis revealed that EVs are enriched in decorin, an extracellular matrix protein known for its antifibrotic properties. This study investigates whether decorin helps EVs reduce atrial fibrosis by inhibiting profibrotic pathways. This investigation involves a comparison between EVs that contain decorin and those depleted of it. My findings confirm that decorin is highly enriched in EVs and demonstrate that decorin treatment reduces fibroblast proliferation stimulated by TGF-β1. Additionally, DsiRNA knockdown depletes decorin from EVs, providing a model to assess its role. Decorin-enriched EVs significantly reduced cell proliferation compared to decorin-depleted EVs. This suggests that decorin plays a significant role in addition to other factors contributing to the antifibrotic effect of EVs
Developmental Programming by In Utero Opioid and Cannabis Exposure: Impacts on Offspring Neurocognitive and Cardiometabolic Health
No full textIntroduction: Opioid and cannabis use during pregnancy poses risks to both maternal and fetal health. While prenatal exposure to each drug has been studied in isolation, health outcomes associated with polysubstance use, particularly regarding long-term neurocognitive health in offspring, remain unclear. Opioid agonist therapy such as buprenorphine (BUP) is the prevalent harm reduction strategy employed for opioid use during pregnancy, but its long-term developmental effects remain uncertain. This study examines the impact of prenatal exposure to fentanyl (FEN) and Δ9-tetrahydrocannabinol (THC) on fetal neurocognitive and cardiometabolic programming. The effects of two harm reduction strategies on improving these outcomes are further explored, specifically involving the transition to an opioid agonist therapy and/or removing cannabis exposure by mid-gestation.
Methods: Pregnant CD1 dams were administered FEN alone or a combination of FEN and THC throughout gestation. Additional groups were transitioned at mid-gestation to BUP with or without continued THC exposure. Offspring were monitored from birth to adulthood and underwent longitudinal behavioural assessments of working memory, sociability, and motor coordination across key developmental stages. Cardiometabolic health was evaluated through repeated measures of growth trajectories, blood pressure, glucose regulation, and body composition.
Results: Combined FEN+THC exposure produced the most pronounced disruptions, impairing working memory, social behaviour, temperature regulation, and cardiometabolic health in a sex-dependent manner. FEN alone also affected neurocognitive and metabolic outcomes, but to a lesser extent. Transitioning from FEN to BUP without the presence of THC altered offspring development. When THC exposure continued throughout gestation, BUP transition failed to normalize behavioural or metabolic trajectories and, in some cases, exacerbated weight gain and neurocognitive effects. When THC was discontinued, transitioning to BUP attenuated adverse outcomes.
Conclusion: Prenatal opioid and cannabinoid exposures have complex and sex-dependent effects. The efficacy of harm reduction via BUP is critically influenced by concurrent THC exposure