Chronic Toxicity of Lithium to the Water Flea Daphnia pulex and Fingernail Clam Pisidium dubium

Lithium (Li), a metal used in batteries and pharmaceuticals, is increasingly in demand as part of a greener economy. However, its extraction, use, and disposal may elevate environmental concentrations, raising concerns about aquatic ecosystems. This study assessed Li chronic toxicity and bioaccumulation in two freshwater invertebrates: Pisidium dubium (28-day exposure) and Daphnia pulex (21-day exposure). Organisms were exposed to environmentally relevant Li concentrations (0.05-10 mg/L for P. dubium; 0.5-3 mg/L for D. pulex). Results showed reduced survival (EC₅₀ = 1.37 mg/L) and impaired burrowing behavior (EC₅₀ = 1.59 mg/L) in P. dubium, with tissue analysis suggesting internal Li regulation. In D. pulex, reproduction (EC₅₀ = 1.77 mg/L) and growth (EC₅₀ = 3.01 mg/L) were significantly affected. While natural Li levels in surface waters are usually below these thresholds, elevated concentrations near mining and urban areas could harm aquatic invertebrates, highlighting the need for improved waste management strategies

The Realities of Fatigue for Pediatric Residents: A Qualitative Study

Resident physicians are particularly susceptible to fatigue due to the rigorous demands of their training, which requires them to balance patient care, on-call responsibilities, and educational obligations. Resident fatigue is a complex issue in healthcare, one that previous quantitative studies have often overlooked in terms of depth and nuance. My thesis explored the question: What are the realities of fatigue for residents within a pediatric training program? Through an exploratory qualitative study, I conducted in-depth, semi-structured focus groups with pediatric residents to gain insights into their experiences of fatigue within a Canadian training program. Using reflexive thematic analysis, I developed six interrelated themes, which indicated that the realities of fatigue for the study participants involved: (1) a reluctant indoctrination into working hour expectations; (2) reaching the extreme limits of fatigue; (3) an emotional toll of tiredness; (4) feeling disconnected from others; (5) feeling disconnected from self; all of which were (6) compounded by the competing demands of residency and everyday life. The research findings offer a more comprehensive understanding of the fatigue experienced by residents within their clinical learning environments, helping to humanize their experiences and advocate for a more urgent allocation of resources to mitigate fatigue risk in medical education. Furthermore, the findings challenge deeply rooted cultural norms within medicine that have historically hindered open discussion and action on addressing fatigue among trainees

In Vivo Dendritic Dynamics of Somatostatin-Expressing Interneurons (SST-INs) in the Primary Motor Cortex (M1) During Motor Learning

The primary motor cortex (M1) is critical for motor learning. Within M1, excitatory pyramidal neurons (PyrNs) undergo network re-organizations, forming task-specific ensembles. This process was recently discovered to be modulated by a functionally distinct ensemble of somatostatin-expressing inhibitory neurons (SST-INs) in M1 that predominantly express neuronal PAS domain 4 (NPAS4) upon motor learning. NPAS4+ SST-INs reduced inhibition onto postsynaptic PyrNs, facilitating circuit reorganization, and thus, motor learning. NPAS4+SST-IN ensemble hints at learning-associated input integration in SST-INs, however, the underpinning of this process remains unclear. To investigate this, I employ in vivo two photon Ca²⁺ imaging in awake mice to chronically monitor dendritic and synaptic activity of SST-INs throughout training for head-restrained bi-directional disk task, followed by identification of NPAS4+ SST-IN ensemble in M1. Building upon finding of branch-specific Ca²⁺ spikes on layer 5 PyrNs' apical dendrites in M1during motor learning, which induces potentiation of learning-related spines, I hypothesize that motor learning-induced dendritic Ca²⁺ activity will trigger and maintain experience-dependent synaptic plasticity in dendrites of NPAS4+ SST-INs. We observed two distinct SST-IN populations during motor training: neurons showing increased ('positive') or decreased ('negative') dendritic activity. Task-specific NPAS4+ SST-INs displayed a nuanced pattern of synaptic integration. In the early training phase, these neurons exhibited broader, non-specific synaptic engagement, characterized by higher spine-dendrite co-activity. As training progressed, we observed a selective refinement of synaptic connections, suggesting an active mechanism of circuit optimization. Overall, this research elucidates dendritic and synaptic plasticity of SST-INs during motor learning, offering insights into neural plasticity and potential therapeutic strategies for neurological injury rehabilitation

Product Structure, Separating Systems, Freeze-Tag Problem, and Planar Multicolor Turan Number

This thesis is based on a collection of papers focused on graph theory and computational geometry. The first paper focuses on the Product Structure Theorem for planar graphs, which asserts that any planar graph can be embedded in the strong product of a planar 3-tree, a path, and a 3-cycle. The paper presents a simple linear-time algorithm to find this decomposition for an n-vertex planar graph, improving on the previous O(n log n) time algorithm. In the second paper, the concept of vertex-separating systems is explored, where a separating system is a collection of vertex subsets that is used to distinguish between any two distinct elements of the vertex set. The paper investigates the minimum size of vertex-separating path and tree systems for various types of graphs, including trees, grids, and maximal outerplanar graphs. The third paper tackles the geometric freeze-tag problem, an optimization problem where the goal is to minimize the total wake-up time for a swarm of robots starting with a single active robot. The authors prove a conjecture by Bonichon et al. regarding an upper bound on the wake-up time for robots in convex position and provide an upper bound of 4.63r for robots located in a disk of radius r in the $\ell_2$-norm, improving the best known bound of $5\sqrt{2}r \approx 7.07r$. Finally, the fourth paper addresses the planar rainbow Turan problem, where the objective is to determine the smallest number of maximal planar graphs required on the same set of n vertices to guarantee a rainbow triangle (a triangle formed by edges from three distinct graphs). The paper establishes both upper and lower bounds, showing that a sequence of at least 0.75n planar graphs guarantees a rainbow triangle, and provides an almost linear lower bound using Behrend’s construction for three-term arithmetic progression-free sets. Together, these works contribute to both theoretical and algorithmic advancements in graph decompositions, separating systems, and optimization problems within geometric and graph theoretic settings

Canadian Varsity Student-Athletes’ Perceived Institutional Mental Health Support: Are Universities Extending the Care Needed for Flourishing in an Endemic World?

Canadian university student-athletes regularly face a combination of academic-related stressors (e.g., assignments due, tuition to pay) and sport-related stressors (e.g., travel to competitions, injury, fatigue). In fact, evidence suggests that university student-athletes are at an increased risk for mental health concerns. To further understand student-athletes’ particular experiences, the present master’s thesis research investigated student-athletes’ perspectives on institutional mental health support and whether they believe the support provided is enabling them to flourish in an endemic world. Grounded in Keyes’ two-continua model of mental health and Basic Psychological Needs Theory, this study explored how institutional environments and need satisfaction influence student-athletes’ well-being. A multi-method qualitative approach combining timelining and semi-structured interviews was used with eight varsity student-athletes from multiple sports. Narrative analysis was used to create storylines within and across student-athletes’ experiences. From these storylines, three composite creative nonfictions (CNFs) were built. The first CNF was written using a first-person narrative exploring a student-athlete’s internal thoughts and feelings on mental health supports at their institution, as well as the barriers they faced accessing these supports. The second and third CNFs were written as an all-knowing narrator (i.e., third-person omniscient) detailing two student-athletes’ divergent experiences of flourishing and languishing. Based on the results, recommendations are offered to help universities adapt and develop initiatives aimed at better supporting student-athletes’ mental health

Investigating the Role of Chronic OPA1 Loss in Muscle Stem Cell Maintenance and Activity

Adult muscle stem cells (MuSCs) play a crucial role in tissue regeneration, yet the mechanisms governing their dysfunction and depletion during aging remain unclear. However, during aging, regulators of mitochondrial dynamics, a key regulator of MuSC activity and fate, decline in expression. This loss of mitochondrial fission and fusion modulators has been associated with premature aging phenotypes in whole muscle and MuSC dysregulation with age. To date, how mitochondrial dynamics contribute to senescent and aged-like phenotypes in MuSCs has not been fully described. Our lab has previously implemented a Pax7CreERT2 inducible system to conditionally knock-out the mitochondrial fusion protein OPA1 specifically within MuSCs (OPA1-KO) and found that with chronic loss of OPA1, MuSCs have enhanced activation kinetics, significant proliferation defects, and evidence of mitochondrial dysfunction. In this current work, we sought to address the role of chronic OPA1 loss in MuSCs, particularly in the contexts of aging and senescence. We found that with chronic loss of OPA1, MuSCs accumulate biomarkers of senescence, experience cell cycle dysregulation at the transcriptional level, and have a dysregulated metabolome. However, the proliferative defects associated with chronic OPA1 ablation may be partially mitigated via supplementation of exogenous metabolites. Notably, at 9 months of OPA1 loss, the phenotype of MuSC dysfunction was found to progress to the extent of stem cell depletion basally. Further, whole-muscle defects were observed at this time, including the onset of a muscle wasting phenotype (with a reduction in the myofiber cross-sectional area and the number of myonuclei per myofiber) and increased fatiguability of the muscle. These findings suggest that mitochondrial dynamics are a critical regulator of MuSC activity and maintenance in an aging context, and that whole muscle health during aging is dependent on the presence of functional MuSCs. This research offers novel therapeutic insight that may be leveraged to improve muscle stem cell health and function with age

Cognitive-Communication Disorders and Mindfulness-Based Interventions in Children and Adolescents with Acquired Brain Injuries

Objectives: Cognitive-communication disorders (communication difficulties due to underlying cognitive impairments) are a common consequence of acquired brain injuries (ABI) in children and adolescents, with devastating effects on daily functioning. Mindfulness-based interventions (MBIs) have shown promise in improving cognitive, emotional, and behavioural outcomes, yet their application in pediatric populations remains poorly understood. Addressing these gaps is critical to advancing evidence-based rehabilitation practices for children and adolescents with ABI. This thesis aimed to (1) synthesize existing evidence on MBIs for children and adolescents, (2) examine current cognitive-communication rehabilitation practices for pediatric ABI, and (3) assess the feasibility and acceptability of a smartphone MBI for adolescents with ABI. Methods: Three studies were conducted to achieve these objectives. Study 1 was a scoping review examining MBIs in pediatric populations. Study 2 involved a retrospective chart review of cognitive-communication rehabilitation practices in a pediatric inpatient ABI setting. Study 3 was a pilot study evaluating the feasibility and acceptability of an application (app)-based MBI for adolescents with ABI. Results: The scoping review identified heterogeneity in MBI types, adaptations and populations, and underspecified intervention ingredients and targets. The chart review revealed infrequent interprofessional collaboration and limited speech-language pathologist (SLP) involvement in cognitive rehabilitation. The feasibility study demonstrated that an app-based MBI was feasible and acceptable, with participants reporting improved mindfulness skills, well-being, and fatigue, but recruitment and adherence challenges prevailed. Conclusions: The findings of this thesis reveal the complexities of providing comprehensive and collaborative rehabilitation services for children and adolescents with ABIs, as well as the fragmented state of mindfulness research and use in pediatric populations. This work advocates for greater involvement of SLPs in cognitive rehabilitation and emphasizes the potential of integrating mindfulness into ABI care. The scoping review and chart review establish a foundational understanding of these challenges, while the feasibility study offers preliminary evidence for the use of digital MBIs to support the needs of this population. Overall, this thesis lays the groundwork for advancing evidence-based, innovative approaches to improve outcomes for children and adolescents with ABI

Decoding the impact of environmental shifts on snail density dynamics in the Yangtze River basin: a 26-year study

Abstract Background With the intensification of climate change and human engineering activities, environmental changes have affected schistosome-transmitting snails. This study explored the influence of environmental changes on the evolution of snail populations. Methods Data from annual snail surveys and related factors such as hydrology, temperature, vegetation, etc., on nine bottomlands from 1997 to 2022 were collected retrospectively from multiple sources. Interpretable machine learning and the Bayesian spatial-temporal model assessed the relationship between environmental change and snail density. Results Between 1997 and 2003, mean snail density was in a high-level fluctuation stage. From 2003 to 2012, it declined significantly from 0.773/0.1 m2 to 0.093/0.1 m2. However, it increased by 27.6% between 2013 (0.098/0.1 m2) and 2022 (0.125/0.1 m2). Since operation of the Three Gorges Dam (TGD) began in 2003, the duration of bottomland flooding decreased from 122 days (1997–2003) to 57 days (2003–2012) and then rebounded in 2012–2022, which was noticeable in the Anhui Section. The ground surface temperature and night light index of the bottomlands increased from 1997 to 2022. After adjusting for confounding factors (e.g. rainfall, temperature, and vegetation), the relative risk (RR) of increased snail density rose with flooding duration of between 20 and 100 days but decreased with flooding duration of > 100 days. Snail density showed an “L”-shaped relationship with the night light index, and the RR of increased snail density was lower at a higher night light index. Compared with bottomlands in the first quartile cluster of ground surface temperature, bottomlands in the second, third, and fourth quartile clusters of ground surface temperature had higher snail density RR values of 1.271 (95% CI 1.082–1.493), 1.302 (95% CI 1.146–1.480), and 1.278 (1.048, 1.559), respectively. Conclusions The TGD lowered the water level and flooding duration, which were not conducive to snail population growth. However, over time, the inhibitory effect of the TGD on snails may have been weakening, especially in areas far from the TGD. In recent years, the rebound of snail density may have been related to the rise in water levels and the change in the microenvironment. Establishing an efficient monitoring and response system is crucial for precisely controlling snails. Graphical Abstrac

Placental Abruption: Clinical Indicators, Histological Findings, and its Impact on Neonatal Health

Placental abruption involves premature placental separation from the uterine wall, resulting in adverse maternal and neonatal outcomes. Using data from 287 confirmed cases at two large Canadian hospitals, we examined clinical, lifestyle, imaging, and postpartum histological measures, alongside neonatal health indicators. Canonical correlation analysis revealed moderate relationships among these variables, suggesting potential markers for earlier detection and timely intervention. Specific clinical indicators and histological features were associated with preterm birth and low birth weight. The analysis highlighted the placenta's role in reflecting maternal conditions and emphasized the need for proactive prenatal care. Although limited by the lack of histological data from healthy pregnancy, these findings support targeted follow-up studies to assess diagnostic and predictive accuracy. Identifying such markers may aid clinicians in refining management strategies, potentially improving maternal and neonatal outcomes while addressing ethical considerations surrounding delivery timing. Further confirmatory research with healthy pregnancies and other complications is needed

Analysis of Time-Periodic Navier-Stokes Equations in a Moving Domain and Numerical Computations with Radial Basis Neural Networks: Application to Artificial Hearts Blood Flow

The dynamics of blood flow within an artificial heart (AH) chamber are governed by the time-periodic Navier-Stokes (NS) equations. These equations are coupled with a hyperbolic partial differential equation (PDE) that describes the dynamic behavior of the membrane (diaphragm). This coupled system of PDEs is subject to a moving boundary. In this work, we decouple the system by assuming that the solution of the membrane equation is known within a well-defined Banach space. Subsequently, we solve only the NS problem and not the coupled fluid-structure problem. We conduct an analysis, specifically examining the existence and uniqueness of a time-periodic strong solution for the Navier-Stokes (NS) problem in dimensions = 2, 3 within a moving domain. The moving domain Ωₜ is supposed to be a ^∞(^{2,2̂*}) ∩ ^1(^2) ∩ ^2(^2) local perturbation of a ^{1,1} reference domain Ω₀ where 2̂* = 2 + {4 / }, > 0 if = 2 and 2̂* = 3 + { / (4 - )}, ∈ (0, 3] if = 3. Typically, our moving domain Ωₜ is of class ^∞(^{2, 2̂*}) ∩ ^1(^2) ∩ ^2(^2), which is weaker that the ^3 in space regularity presented in the literature. Subsequently, we proceed to numerically solve the problem in dimension = 2 using radial basis neural network (RBNN) functions. To validate our computational framework, we compare our results against existing literature, particularly by solving benchmark-driven cavity problems up to a Reynolds number = 10,000$. Finally, we solve numerically the time-periodic NS equations for different AH geometries. The results we obtain demonstrate the strong dependence of the blood flow behavior on the AH geometry and motivate the optimal shape design of AH, which we plan to address in future work