Recherche uO, le dépôt numérique de l'Université d'Ottawa, réunit le matériel de recherche et d'enseignement créé par notre communauté universitaire et nos partenaires. Le savoir de l'Université est ainsi disponible à long terme et en accès libre, ce qui lui procure de la visibilité et facilite sa diffusion.

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    Ageing and the Impact of Cognitive Demand on the Strength of Functional Connectivity Throughout the Brain
    (Université d'Ottawa | University of Ottawa, 2026-10-09) Othman, Rawan; Steffener, Jason
    Functional connectivity refers to the way brain regions interact during various cognitive tasks. The current study examined how functional connectivity changes with increasing task difficulty and whether these effects are influenced by age. Two hypotheses were tested in the current study. The first hypothesis is that the strength of functional connectivity during increasing cognitive demand will differ with age in some brain regions. The second hypothesis is that the strength of functional connectivity will change due to cognitive demand, independent of age in other regions. Results showed that increasing cognitive demand was associated with increased connectivity in regions such as the middle temporal gyrus and the right planum temporale, while other regions showed decreased connectivity independent of age. These findings suggest that cognitive demand and age may have different effects on functional connections within the brain.
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    Optical Thermometry with Organoeuropium(II) Complexes
    (Université d'Ottawa | University of Ottawa, 2026-10-09) Diaz-Rodriguez, Roberto Manuel; Murugesu, Muralee
    The measurement of temperature is of critical importance to a diverse array of fields and industries, such as heating, ventilation, and cooling, nutrition, molecular biology, medicine, engineering of all denominations, chemistry, climate science, and computing technologies, to name a few. As technologies in all these areas progress, measuring temperature more accurately and precisely under increasingly challenging conditions is an ever-evolving problem. One strategy to address these challenges is optical thermometry, which correlates changes in the optical characteristics (e.g. luminescence intensity, emission lifetime, colour, etc.) of a thermosensitive system to changes in temperature. In contrast to common thermometric methods employing thermistors, thermocouples, or even infrared thermography, optical thermometry is a remote-detection, minimally invasive technique with very high attainable spatial resolution, making it well-suited to probing temperature in difficult environments and sensitive systems. Due to their favourable (magneto-)optical properties, lanthanide-based materials are well-studied as optical thermometers. However, most of these materials operate via a ratiometric approach monitoring thermosensitive emission intensities on account of comprising trivalent lanthanides, which exhibit characteristic narrow, Laporte-forbidden 4f-4f absorbance and emission bands whose positions are almost invariant with temperature. This thesis explores a less-studied approach to lanthanide-based optical thermometry, exploring divalent europium and its Laporte-allowed, environment-sensitive, intense and broad 5d-4f transitions for thermal sensing, with a focus on emission band-shift. Moreover, organometallic complexes were targeted for these studies, as these are also not well-known for optical thermometry and the unique structure and bonding of such systems was envisioned to lead to unique properties. Starting from the brightly emissive, synthetically convenient starting material [EuII(BH4)2(THF)2] (which was revealed to itself be a well-performing luminescence thermometer), the hemimetallocene dimer [Cp*Eu(μ-BH4)(THF)2]2 (Cp* = pentamethylcyclopentadienyl) was prepared and characterized. This complex exhibits strongly thermochromic luminescence, with the maximum of the 5d4f emission band red-shifting by nearly 1900 cm-1 as the temperature is increased from 60-320 K. This defines a thermometric system that demonstrates the highest absolute sensitivity of any lanthanide-based band shift thermometer to date, reaching 8.2 cm-1 K-1 at 320 K. An opto-structural correlation study via variable-temperature single-crystal X-ray diffraction revealed that small changes in metrical parameters with temperature were correlated to these rather large changes in emission wavelength/energy, unveiling the potential of organoeuropium(II) systems as sensitive luminescence thermometers. Building upon this discovery, a series of isostructural hemimetallocene dimers [CpREu(μ-BH4)(solv)n]m (solv = tetrahydrofuran, 1,2-dimethoxyethane; n = 1 or 2; m = 2 or ∞) bearing systematically varying ligand sets was synthesized and examined for their thermometric performance, with an eye toward elucidating some of the factors governing the thermochromic luminescence that is clearly intrinsic to this type of system. Members of this series show widely varying emission properties despite their compositional similarities, demonstrating the tunability of the europium(II) hemimetallocene architecture. Optostructural correlation studies via variable-temperature single-crystal X-ray diffraction revealed a convoluted dependence of the emission properties on various factors, which are difficult to disambiguate. However, a few factors of particular importance are identified, such as the distance between the europium(II) ion and the basal plane of the square-pyramidal coordination polyhedron, the presence of pendant electron density that might further interact with the excited-state 5d orbitals, and metal-ligand flexibility. These findings represent a step toward enabling the rational design of organoeuropium(II) luminescence thermometers for bespoke characteristics. Finally, one of the substituted cyclopentadienides from the previous study, 1-(bis(dimethylamino)phosphino)-2,3,4,5-tetramethylcyclopentadienyl, was selected for further investigation due to the good thermometric performance exhibited by its hemieuropocene(II), and the possibility of further functionalizing the free phosphine moiety. Oxidizing this moiety with elemental sulfur, selenium, or tellurium yielded a corresponding series of novel phosphinochalcogenoylcyclopentadienides, which were coordinated to europium(II) to give a family of homoleptic europocenes(II) bound by both the cyclopentadienyl fragment and the pendant phosphinochalcogenoyl arms of the ligands. These complexes were characterized structurally and optically and, though they are not suited to band-shift luminescence thermometry, turn out to be extremely sensitive magneto-optical thermometers via magnetic circular dichroism, with relative sensitivity values reaching 170 % K-1 at ultralow temperatures inaccessible to conventional luminescence thermometry. This result corroborates our previous work introducing the concept of magnetic circular dichroism thermometry, and further strengthens the position of europium(II) as a valuable foundation for thermosensitive optical materials.
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    Glacial Meltwater is Associated with Gene-Specific Diversification of Metal Resistance Genes in High Arctic Soil Microbiomes
    (Université d'Ottawa | University of Ottawa, 2026-10-09) Ouedraogo, Franck Joel; Aris-Brosou, Stéphane; Poulain, Alexandre
    Climate warming accelerates the delivery of glacial meltwater to Arctic lakes, mobilizing metals from thawing catchments and reshaping the selective landscape experienced by resident microbes. Whether these gradients leave detectable signatures of diversification in environmental resistance genes remains unclear. We investigated four metal resistance genes (merA, arsC, cadA, and chrR) in metagenomic datasets from Lake Hazen (Nunavut, Canada), the largest High Arctic freshwater lake, sampled across a natural hydrological gradient of Control, Low-runoff, and High-runoff regimes. Using a space-for-time substitution design, we combined population-genetic and codon-based approaches to quantify diversity and candidate selection signals, including nucleotide diversity, Tajima's D, non-synonymous-to-synonymous diversity ratios, McDonald-Kreitman tests with outgroup-sensitivity analysis, site-level episodic selection (MEME with false-discovery-rate correction), and gene-wide tests (BUSTED and BUSTED-E) and complemented these with ortholog clustering, within-clade re-analysis, taxonomic profiling, rarefaction, and phylogenetic beta-diversity. Marked heterogeneity emerged among genes. merA showed increasing diversity and diversification along the runoff gradient, and these signals were preserved within the largest orthologous cluster (90% of haplotypes), supporting an interpretation of within-orthogroup diversification. cadA displayed the strongest McDonald-Kreitman signal under low and high runoff, but its gene-wide BUSTED-E signal collapsed within a single ortholog cluster, suggesting that part of the apparent diversifying signal at the gene-family level reflects inter-subfamily heterogeneity. chrR exhibited the strongest regime structure but its largest orthologous cluster was dominated by Control sequences and 93% of High-regime haplotypes were affiliated with a single bacterial order (Hyphomicrobiales), indicating that the regime contrast for this gene reflects compositional turnover rather than within-lineage evolution. arsC remained largely consistent with neutral or purifying evolution across regimes. Because these inferences derive from metagenomic gene pools sampled across only three hydrological regimes and aggregate variants across taxa, we interpret them as exploratory, hypothesis-generating patterns rather than as demonstrations of population-level adaptation. Our findings highlight environmental resistance genes as candidate indicators of changing biogeochemical conditions in rapidly warming polar ecosystems, while underscoring the importance of orthology and community-composition controls when inferring selection from metagenomic data.
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    Remédiance après la catastrophe : enquête anthropologique sur la reconfiguration des milieux à Minamisōma, Fukushima
    (Université d'Ottawa | University of Ottawa, 2026-10-09) Chateauneuf, Michael; Mirza, Vincent; Boret, Sébastien
    Cette thèse propose une enquête anthropologique sur les transformations du milieu à Minami-Sōma, dans la préfecture de Fukushima, plus d’une décennie après la triple catastrophe du 11 mars 2011 (séisme, tsunami et accident nucléaire). Plutôt que de concevoir la catastrophe comme un événement ponctuel suivi d’une reconstruction linéaire, elle l’aborde comme une rupture ontologique durable, affectant simultanément les dimensions sociales, économiques, symboliques et environnementales de l’existence. S’appuyant sur une année de terrain ethnographique réparti entre 2023 et 2024, cette recherche suit principalement des prêtres shintō et leurs communautés. À travers l’observation participante, des entretiens semi-dirigés et une immersion dans les matsuri locaux – notamment le Sōma Nomaoi et le Hibuse Matsuri – j’analyse la manière dont les habitants recomposent leur rapport au milieu dans un contexte marqué par la contamination radioactive, le déclin démographique et la transformation des réseaux communautaires. Au cœur de la thèse se trouve le concept de remédiance, développé à partir de la notion de fûdosei (Watsuji Tetsurō) et des travaux d’Augustin Berque sur le milieu. Le milieu y est défini comme une co-constitution dynamique entre humains et environnement. La catastrophe apparaît alors comme une rupture de la médiance, un moment de désarticulation des relations constitutives de l’habiter. La remédiance désigne le processus par lequel les communautés tentent de recréer des formes d’habitabilité à travers la recomposition des liens sociaux, des conditions matérielles et des cadres symboliques. Sur le plan théorique, la thèse contribue aux débats contemporains en anthropologie de l’environnement et des catastrophes en proposant une approche ontologique du milieu, articulant héritage herméneutique, théorie des champs et critique du dualisme moderne. L’analyse montre que les rituels shintō, les festivals saisonniers, les pratiques agricoles et les initiatives communautaires ne constituent pas de simples survivances culturelles, mais des opérateurs actifs de remédiance. Ils permettent d’inscrire la catastrophe dans une temporalité plus longue, sans en effacer les fractures. Ce que l'on trouvera ici n'est donc pas le récit d'une reconstruction achevée, mais celui, bien plus troublant, d'un milieu qui continue de se faire – et des femmes et des hommes qui, chaque jour, le font avec lui.
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    Peptide-Centric Computational Frameworks for Taxonomic and Functional Interpretation in Metaproteomics
    (Université d'Ottawa | University of Ottawa, 2026-10-09) Wu, Qing; Figeys, Daniel
    Metaproteomics provides direct molecular evidence of the expression of specific proteins in microbial communities by identifying and quantifying peptides from complex biological samples. However, the interpretation of metaproteomic data remains challenging because experimentally observed peptide evidence must be converted into biological conclusions across multiple analytical layers, including reference database construction, protein inference, shared peptide ambiguity, taxonomic assignment, functional annotation, statistical testing, and visualization of hierarchical outputs. This thesis develops peptide-centric computational frameworks for taxonomic and functional interpretation in metaproteomics, with the goal of transforming metaproteomic peptide identifications into taxonomically resolved, functionally interpretable, statistically supported, and visually organized microbiome profiles. First, a metagenomics-informed hamster gut metaproteomics workflow was established for the study of SARS-CoV-2 infection. In this application-driven study, metagenomic assembly, annotation, binning, and database generation provided the reference foundation for downstream metaproteomic analysis and enabled deep profiling of microbial and host-associated proteins in young and old hamsters. This work demonstrates the importance of host- and sample-specific reference construction for metaproteomic studies of complex microbiome systems. Second, MetaUmbra was developed to address genome-level presence inference from metaproteomic peptides. By evaluating unique and shared peptide evidence within a formal statistical framework, MetaUmbra provides genome-level p-values and false discovery rate-controlled support for interpreting peptide lists against user-defined genome panels. This framework addresses the ambiguity introduced by shared peptides and helps distinguish statistically supported genome-level evidence from raw peptide matching. Third, MetaX was developed as an integrated peptide-centric metaproteomics analysis platform. MetaX combines database construction and updating, peptide-level taxonomic and functional annotation, Operational Taxon-Function analysis, data preprocessing, downstream statistical analysis, and visualization tools within a unified workflow. By supporting comparative analysis across peptides, proteins, taxa, functions, and taxon-function units, MetaX provides the central analytical framework for taxonomic and functional interpretation in this thesis. Fourth, MetaTree was developed to extend hierarchical visualization and multi-group comparison of MetaX-derived and other hierarchical outputs. MetaTree focuses on topology-consistent visualization, aligned comparison across samples and groups, comparison matrices, and publication-ready figure export. Together, these studies establish a connected set of peptide-centric computational frameworks that link metaproteomic peptide evidence to reference database construction and peptide identification, genome-level inference, taxon-function analysis, statistical interpretation, and hierarchical visualization. Collectively, this thesis advances metaproteomics from peptide and protein identification toward integrated biological interpretation of complex microbial communities.