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Studies on tear evaporation and ocular surface temperature
No full textIntroduction
Evaporative Dry Eye (EDE), the most prevalent subtype of Dry Eye Disease (DED), is primarily driven by excessive tear loss from the ocular surface due to deficiencies in the tear film’s lipid layer. Accurate and repeatable measurement of Tear Evaporation Rate (TER) and related ocular surface parameters, such as Ocular Surface Temperature (OST), Lipid Layer Thickness (LLT), and Non-Invasive Tear Break-Up Time (NITBUT) is essential for understanding tear film instability and guiding clinical decision-making. However, measurement variability, lack of standardized protocols, and limitations in existing instrumentation have hindered the adoption of TER and OST assessment in routine practice. This thesis addresses these challenges through a series of in vitro and in vivo experiments aimed at quantifying tear film dynamics and optimizing measurement methodologies.
Overall Aims
The primary aim of this research was to characterize tear evaporation and ocular surface thermal behavior under a range of physiological and controlled conditions. This thesis specifically sought to:
1. Quantify the evaporation rates of distilled water versus an aqueous artificial tear solution (TheraTears®) in vitro.
2. Assess how changes in exposed ocular surface area and LLT affect TER using model eyes.
3. Investigate the effect of lipid-based artificial tears on LLT, TER, and NITBUT in vivo (PHASE I).
4. Optimize OST measurement parameters using ResearchIR software to improve accuracy and reproducibility.
5. Examine regional variation in OST and blink-related cooling profiles in vivo (PHASE II).
6. Integrate in vitro and in vivo findings to build a comprehensive model of tear film dynamics with implications for EDE diagnosis.
Methods and Materials
The experiments were conducted using custom-built and commercially available devices. In vitro studies used aluminum model eyes with varied surface areas and lipid layer simulations (via CALMO® Eye Spray) to evaluate their effect on TER, measured using the Waterloo Evaporimeter. In vivo studies were performed on healthy participants using the LipiView® II interferometer, OCULUS Keratograph® 5M, and FLIR A655sc thermal camera integrated with ResearchIR software. Data collection included real-time measurements of TER, LLT, NITBUT, and OST, with particular focus on blink-related cooling and temperature gradient analysis. Each experiment followed standardized protocols for blink control, Region of Interest (ROI) selection, and repeatability validation. Statistical analysis was performed using SPSS, with significance set at p < 0.05.
Results
In vitro results demonstrated no significant difference in TER between distilled water and TheraTears®, suggesting that aqueous-based artificial tears do not provide meaningful evaporative protection. These findings also confirm that both distilled water and TheraTears® may be used interchangeably in laboratory-based evaporation studies where lipid content is not a critical variable. In contrast, increasing LLT using CALMO® spray led to a marked reduction in TER, and model eyes with larger surface areas consistently exhibited higher evaporation rates. In vivo, lipid eye drop instillation produced a significant increase in LLT, a prolongation of NITBUT, and a decrease in TER. OST monitoring revealed distinct blink-related cooling patterns, particularly in eyes with thinner lipid layers. Optimized OST protocols using ResearchIR improved temporal resolution and reproducibility across participants. Phase II confirmed consistent regional temperature variability and strong correlations between LLT, TER, and post-blink cooling.
Conclusions
This research confirms that LLT and ocular surface area are critical determinants of TER. Non-lipid formulations, such as TheraTears®, are ineffective in limiting TER, while lipid-based interventions significantly improve tear film stability both thermally and structurally. OST can be used as a reliable, non-invasive surrogate for assessing tear film dynamics when measured with optimized protocols. The Waterloo Evaporimeter and ResearchIR-enabled thermography provide robust, reproducible platforms for studying tear evaporation and cooling responses. These findings support a multimodal diagnostic approach integrating TER, LLT, NITBUT, and OST for the evaluation and management of EDE
Development of a novel assay for the characterization of germination responses in microsporidian parasites: An investigation into the biology of Spraguea americanus
No full textThe microsporidia are a widespread group of intracellular parasites which infect a broad range of hosts across the animal kingdom. In particular, the microsporidian Spraguea americanus has received considerable attention in recent years due to its role as an endemic pathogen in American anglerfish (Lophius americanus); a species of highly valued finfish currently at risk due to overfishing. However, like many species of microsporidia, the germination responses of S. americanus remain poorly described. This study outlines a novel in vitro germination assay for microsporidia, which is then used to comprehensively survey the germination responses of S. americanus under a variety of conditions. The results of this investigation indicate that S. americanus is responsive to mechanical pressure, hydrogen peroxide, sodium carbonate/bicarbonate and divalent cations, but not to mucin proteins as seen in closely related species. These observations provide evidence to refute the predominant hypothesis that members of Spraguea enter their hosts via the subcutaneous mucosal glands. In addition to providing much needed insight into the transmission of Spraguea spp., this study is among the first to extensively assess the germination responses of a single species of microsporidia; data which may lend itself to a more complete understanding of the mechanisms underlying the initiation of germination in microsporidia or support the establishment of new in vitro models for economically relevant species
Life history and migration patterns of Arctic Char (Salvelinus alpinus) and Dolly Varden (Salvelinus malma malma) in the Coppermine River and Coronation Gulf
No full textArctic Char (Salvelinus alpinus) and Dolly Varden Char (Salvelinus malma malma) are of vital importance to Indigenous communities in Arctic Canada. Both species are facultatively anadromous and anadromous individuals exhibit remarkable diversity in migration tactics. Both species are also iteroparous and relatively long-lived, which allows migration patterns of individuals to be studied over multiple years. The Coppermine River, near Kugluktuk, Nunavut, is the only freshwater location where anadromous individuals of both Arctic Char and Dolly Varden have been confirmed to occur in sympatry, thereby providing a unique opportunity to compare habitat use and migration patterns between species. The overarching goal of this thesis was thus to investigate the diverse life history and migration tactics of Arctic Char and Dolly Varden that use the Coppermine River. To achieve this goal, I used an acoustic telemetry dataset from tagged Arctic Char and Dolly Varden that was collected over six years (2018–2023) in the Coppermine River and nearby marine environment of Coronation Gulf.
Acoustic telemetry is widely used in aquatic environments to study animal movement, behaviour, and ecology, but many studies that employ acoustic telemetry neglect to consider the possibility that some detections may be from mortalities or expelled tags, and this can result in biased results. To assist acoustic telemetry practitioners in identifying detections from potential mortalities or expelled tags in a simple and reproducible manner, I developed the R package mort. In Chapter 2, the methods and package are described, and application is demonstrated using three diverse acoustic telemetry datasets that represent: 1) a mobile freshwater fish ((Arctic Grayling (Thymallus arcticus)) in a river network; 2) a relatively sedentary marine fish (Greenland Cod (Gadus ogac)); and, 3) a highly mobile marine fish (Atlantic Salmon (Salmo salar)). Detections flagged by mort were reviewed and removed from the acoustic telemetry datasets that were analyzed in subsequent thesis chapters (Chapter 3, Chapter 4, and Chapter 5).
Marine feeding is of critical importance for anadromous Arctic Char and Dolly Varden; individuals of both species must acquire sufficient resources for growth and reproduction during the brief ice-free seasons. In Chapter 3, I used network analysis and local spatial statistics to identify and describe high use locations and movement patterns in the marine environment for char (Arctic Char or Dolly Varden; species was unknown at the time of writing) that overwintered either above or below Kugluk or Bloody Falls (“the falls”; a large cascade). Char exhibited preference for coastal habitats (relative to offshore or island habitats) and habitat use did not appear to be associated with overwintering location. Timing of return to fresh water was associated with overwintering location, however; char that overwintered above the falls returned to fresh water earlier than char that overwintered below the falls, which suggests that length and difficulty of the migratory pathway was associated with migration timing. Timing of return migration to fresh water was earlier in years when the river froze earlier; this indicates that the timing of char returning to fresh water is responsive to environmental conditions in the system.
Environmental influences on timing of return migration to fresh water are largely unknown for both Arctic Char and Dolly Varden. In Chapter 4, I investigated how environmental variables were related to: 1) timing of return to fresh water by both Arctic Char and Dolly Varden; and, 2) ascension of the falls by Dolly Varden (no Arctic Char were observed ascending the falls in any year). The primary environmental cue for return to fresh water was sea surface temperature (SST); all char returned to fresh water as SST increased. Dolly Varden that overwintered above the falls returned to fresh water at colder SST (earlier) than Arctic Char and Dolly Varden that overwintered below the falls. For Dolly Varden that overwintered above the falls, river temperatures were warm and potentially stressful at the time of return. It is possible that these individuals experienced decoupling between the cue to return to fresh water (SST) and suitable conditions for migration (river temperature). Tide may have facilitated ascension of the falls but was not associated with timing of return to fresh water for Dolly Varden that overwintered above the falls. In contrast, tide was associated with timing of return to fresh water for Arctic Char and Dolly Varden that overwintered below the falls. Together, these results suggest that Dolly Varden that overwintered above the falls made directed return and upstream movements, whereas fish that overwintered below the falls returned to fresh water more passively. Differences in threshold (SST) for return migration and influence of tide between Dolly Varden that overwintered above and below the falls suggests that there may be an underlying physiological cue for migration timing and/or overwintering location.
Fluvial overwintering habitats used by both Arctic Char and Dolly Varden below the falls in the Coppermine River are unusual in that there are no known groundwater inputs. In Chapter 5, I assessed evidence for several potential mechanisms that could explain overwintering below the falls: spawning status, foraging opportunities in the marine environment, and failure to ascend the falls. I found no evidence of foraging from stomach contents, although spatial and temporal coverage of samples was limited. Consistent with intent to overwinter below the falls, Arctic Char staged longer at the river mouth and moved upstream more slowly than Dolly Varden that overwintered above the falls. Dolly Varden that overwintered below the falls exhibited inconsistent movement patterns and I suggested that some Dolly Varden may thus intend to overwinter below the falls, whereas others may fail to ascend the falls. I found no confirmed evidence of spawning activity below the falls for either Dolly Varden or Arctic Char. Telemetry data indicated that Arctic Char overwintered in alternate rivers in some years, which suggests that spawning could occur in alternate rivers and that the lower reaches of the Coppermine River represent easily accessible overwintering habitat in non-spawning years. Dolly Varden that overwintered below the falls were smaller and younger than Dolly Varden that overwintered above the falls, and I suggested that it is likely that Dolly Varden migrate above the falls in spawning years. Spawning locations and frequency remain unknown for both species that use the Coppermine River.
The research presented in this thesis describes the life history and migration tactics of anadromous Arctic Char and Dolly Varden that use the Coppermine River, the only freshwater system that is known to support anadromous life history types of both species. Similarities in marine habitat use and movement patterns between Arctic Char and Dolly Varden and between overwintering groups (above or below falls) of Dolly Varden may present challenges for fisheries management if conservation concerns are identified in future. I observed inter individual and inter-annual (within individual) diversity in migration tactics in Arctic Char and Dolly Varden that use the Coppermine River and Coronation Gulf, as well as influences of environmental conditions on migration timing. The observed plasticity in responses among individuals and years may promote resilience of the two species, but future research on spawning locations and spawning frequency is necessary to provide a comprehensive assessment of potential stressors that could affect the species’ persistence and inform fisheries management.
Nainaakhimayok Unipkangat
(Inuinnaqtun translation of Abstract)
Ikalukpiit (Salvelinus alpinus) tahapkualu Dolly Varden-mik attiktaohimayot Ikaluit ihuukit (Salvelinus malma malma) pimagioyot ikaluit nunakakaktot nikkigingmatjuk tahamani Ukkiuktaktumi Kanatami. Tahapkua tamakmik ikaluit ilangit hittuvaktut tagiokmut ilangitaok aullayuitot tattini. Ikaluit hittuvaktut tagiokmut ajikingitot iliitkuhiit hittugangamik, ilangit kakkugungugangat nammutlu hittuvaktot. Tamakmik hapkua ikaluit iglingmingni igniokpaktot kakkugungagangat tatvalu innughaakataktot, taimatot naunaiyaikatagungnaktavut kanok iliitkuhiitnik hittunahuagangata kaffiktaklugit ukkiuni. Tatvani kugluktumi Kuukmi, kanninganiitok Kugluktuk, Nunavut, tatvatuanguyok kaoyimayavut immagiktok hittuviat tahapkua ikalukpiit tatvalu tahapkua ikaluit ihuukit attiktaohimayot Dolly Varden, una Kuuk nayugagiyat attaotikut. Tukkikaktok tahamna Kuuk atjikutakangitok nayugagiyat hittuvigivakhutjuk tahapkua ikaluit. Taimatot ihomagiloaktavut tahamna naunaiyaiyot havagiyomavlutjuk kanok allangayaghaita hittuvigikatakhutjuk tahapkua ikalukpiit tatvalu hapkua Dolly Varden ikaluit ihuukit nayogagiyat tahamna Kugluktumi Kuuk. Tatva taimatot havagiyomavlutjuk, tahapkua ikalukpiit Dolly Varden ikaluit ihuukit attaataliktoktaovaktot nallauhiktokhugitlo tauktoktaovaktot namungaokatakmangata 6-sinik ukkiunik havagivlutjuk (2018-min 2023-mut) tahamani Kugluktup Kuukmi tatvalu kaningani tahamani tagiokmi Coronation Gulf-mi.
Ataataktuinik tatvalu tammalaitkutinik nallauhiktoinik atogaokataktot imakmi nauyaiyaotigivlutjuk ikaluit namungauningitnik, iliitkuhiitnik tatvalu nayogagiyaitnik, kihiani ammihuyut tahapkua tammalaitkutinik nallauhiktoinik ihomagingitait immakak illangit hapkua naunaiyaotait pihimayungnakhiyat ataatakhimayunit ikalunit tukkuhimayunit uvalunin ataatait kattaktitaonikata, taimatot nallukhaotaungmiyot. Ikkayotaongmat inuknun naunaiyaiyunot ummayunik immakak tahapkua ataatait tukkuhimayuningakhimayot ikalunit uvalunin kattakhimayonik ataatanit, ihuaghaihimaliktunga naunaitkutikhamik kagitaoyakukutimik attikaktok mort-mik. Tatvani unipkat Naunaipkutani 2-mi, naunaiyakhimayaga unipkagivlugo kanok atoktaoyagiakaktok una kagitaoyakut naunaiyaotaoyok, ayogiktoitjutigiyaga kano kuna kagitaoyakut naunaiyaotaoyok atoktaoyungnaktok pingahut allatkit naunaipkutini: 1) tattiniotak una ikaluk (Hulukpaugak (Thymallus arcticus)) kukanikataktok; 2) tagiokmiotak ikaluk una hangukatangitok (Uugak (Gadus ogac)); tatvalu, 3) ungahiktoliakataktok una tagiokmiotak ikaluk (Atlantic Salmon (Salmo salar)). Tahapkua naunaipkutaoyot naunaiyaktaohimayot kagitaoyakut ahivaktaokataktot tahapkunanga naunaiyaotaoyonit takkuktaohimayot ahianit unipkangita naunaipkutaitni (Naunaipkutani 3, Naunaipkutani 4, tatvanilo Naunaipkutani 5).
Tagiokmi nigginiakviat tahapkua ikaluit pimagioyok; tahapkua ikaluit allatkiit nikkikatiagiakaktot akliyamingnik tatvalu igniugiamingnik hikkukangititlugo. Tatvani unipkami Naunaipkutani 3, naunaiyakhimayatka titigakhugit tahapkua nayogagiloaktaitnik namungaokatakningitiklo tahamani tagiokmi hapkua ikalukpiit ikaluitlo ihuukit hapkua Dolly Varden; kanogitungmangata tahapkua ikaluit nallukhaotaoyut titigakpalialiktitlugo tahamna unipkalioktaoyok, tahapkua ukkikataktot nalliakni kullani uvalunin natkani tahaffuma Kugluk-mik attikaktuk Kuuk. Ikalukpiit nayogagiyakaktot hinnanikhiokhutik takkunakpalangitot ittinikmi uvalunin kikiktani. Tahapkua nayogagikataktait ikaluit ihomagiyaovalangitat nannikatakmangata ukkiumi. Uttigangata tagiokmit tahamunga tattinut immagiktunut ihomanaktok nanikatakmangata ukkiumi, kihianitaok; hapkua ikalukpiit ukkikataktot kulani tahaffuma kukluakviani Kuukmi uttikataktut immagiktunut tattinut pinnagikataktot ikalukpiitnit ukkihimayunit natkanit haffuma kukluakviani Kuukmi, ihomannaktok tatva hivituninga tatvalu ayoknautigikataktat tahamna ingilgayatik mayogahualigangamik kinguvautivagungnakhiyok. Kakugu mayokvikikataktat tattinut immagiktunut pinnagikatakhimayot ukkiuni kinguani tahamna Kuuk hikkunagikatagaluakmat; taima naunaikhimaliktok tatva kakugo mayokvighaat tahapkua ikalukpiit tattinut immagiktunut hillap kannugininganik nayogiyagiakaliktok.
Hillap kanogininga pitjutaokatakmat kakugo mayokvighaatnik tahapkua ikalukpiit tatvalu ikaluit ihuukit Dolly Varden nallukhaotaoyut. Tatvani unipkami Naunaipkutani 4, naunaiyaihimayunga kanok tahamna hillap kanogininganik pitjutaokataka tahapkuninga: 1) Kakugo mayokatakat tattinut immagiktunut tahapkua ikalukpiit tatvalu ikaluit ihuukit Dolly Varden; tatvalu, 2) mayokpakhutik kullanut kukluaktup Kuukmi tahapkua ikaluit ihuukit Dolly Varden (naunaiyakhimangitot mayoktunik kullannut Kuukmi huli). Ihomagiluaktavut hilla allangugangat mayokvikhaat tattinut immagiktunut tagiok niklakpalialigangat; tahapkua ikalukpiit mayokataktot tattinut immagiktunut tagiok unnakpaliatitlugo. Tahapkua ikaluit ihuukit ukkikataktot kullani kukluaktumi kuukmi mayokatakmiyot tagiok niklakpalialigangat tahapkuataok ikaluit ihuukit Dolly Varden ukkikataktot natkani tahaffuma kukluaktumi kuukmi. Tahapkua ikaluit ihuukit Dolly Varden ukkikataktot kullani kuukmi, kuukap unnakninga unnatkiyaokatakmat ummilgungnaktokhaoyok mayokpalianiaktitlugit. Immakak tahapkua ikaluit ayughaotigikataktat mayokvikhatik tattinut uttakivagungnakhiyat unnakninganik kukkap. Immaokaomagangat ikkayotaovagungnakhikmiyok kihiani pitjutaovalangituyaaktok mayokvikhaatnik tahapkua ikaluit ihuukit Dolly Varden ukkikataktot kullani kuukmi. Kihianitaok, immaokagangat pitjutaungmiyok mayokvikhaitnik tahapkua ikalukpiit tatvalu ikaluit ihuukit Dolly Varden ukkikataktot natkani kuukmi. taimaitkaluaktitlugit, naunaiyakhimayavut ihomangnaktok tahapkua ikaluit ihuukit Dolly Varden ukkikataktot kullani kukluakviani kuukmi ayoghakhimaitomik mayokataktot tattinut, tatvataok tahapkua ikaluit ukkikataktot natkani kuukmi mayokatakmiyot tattinut immagiktunut kayumiitunuamik. Ikaluit ihuukit Dolly Varden ukkikataktot kullani kukluakviani Kuukmi ahianik tagiop unnakpalianinganik pitjutikakmiyot mayokvighait tattinut immagiktunut immaokaknialo allangangmiyok tahapkunanganin ikaluit ihuukit Dolly Varden tatvanganin ukkikataktunit kullani kukliaviani kuukmi. Ihomanaktok immakak ahianik pitjutikakpagungnakhiyot mayokvikhaat tatvalu/uvalunin ukkiumi namungaovikhaitnik inmingnik ikpigiyakagangamik tahapku tamaita ikaluit taima ihomanaktok.
Tahamna Kuuk ikalukaknik atogagiyat tahakmik hapkua ikalukpiit tatvalu ikaluit ihuukit Dolly Varden ukkiukmi natkani tahaffuma Kukluktumi Kuukmi allangayok pitakangituyaakmat tahamna mannigak immak nakingaakmangata illitugingitnamku. Tatvani unipkami naunaipkutani 5-mi, takkukhimayaga kaffiit ihomagivlugit huok ilangit tahapku ikalukpit ukkikatakat natkani tahaffumja kukkiktuk kuukani: igligiyaitlu igniokvigikataktaitniklo naunaiyagahuaklugit, nigginiakvigiyataktaitlo naninmangata tagiokmi, huoklo maayokatangitpat kuukiktumi kuukmit. Tahapkuataok ikaluit ukkiukataktot natkani tahaffuma kuukiktumi kuukmi, takkuhimangitunga hunnanik igginiakatakmangata akkiagoit illuhikangitmata, kihianitaok naunaiyaihimangitnamta ammihunik ikaluknik nannilunin takkukhimangitnaptigo huli. Taima illiitkuhiktuyaaktot tahamaninaakniaktok ukkiugalok naatkani tahaffuma kukluakviani Kuukmi; tahamaniikhatkiyaongmiyot kukkap pannani tatvalu maayoknahaatkiyaovakhutik tatvanganin ikaluit ihuukit Dolly Varden mayoknagikataktot ukkikatakhutik kulani tahaffuma kukluakviani Kuukmi. Tahapkua ikaluit ihuukit Dolly Varden ukkikataktot naatkani kukluakviani Kuukmi ajikingitut ingilgayangit, ilangit tahapkua ikaluit ihuukit ukkikataktot naatkani kukuakviani Kuukmi, ilangitaok ammukatangitot naatkanit haffuma kukluakvianin Kuukmi. Illiitkugingitatka pikagiaghaita igliitnik naatkani tahaffuma kukluakviani Kuukmi tahapkua ikaluit ihuukit uvaluni ikalukpiit. Tahapkua ikaluit naalautait naunaipkutigivlugit illiitugihimayavut ukkikataktutaok ahinni kukkani ilangitni ukkiuni, taima ihomanaktok iglikakpagungnaghiyok tahapkua ikaluit ahinni kukkani tatvalu ukkiyaktokpakhutik tahamunga Kuglumtumi Kuukmit ukkiuni igliliungitagangamik igniukvikhamingnik, ayungnaitkiyaoyungnakhingmat. Tahapkua ikaluit ihuukit Dolly Varden ukkiktaktaktot tahamani naatkani Kuukmi mikitkiyaovakhutik ikalukpiakjuit tatvanganin tahapkuninga ikaluit ihuukitnit Dolly Varden ukkikatakmata kullani tahaffuma kukluakviata Kuukmi, ihomanaktok immakak tahapkua ikaluit ihuukit Dolly ammukpagungnakhiyot kullanut kukluakviani Kuukmi igliliogiaktokhutik igniokvikhamingnik. Igliliokviit tatvalu kanovalaak igliliokatakmangata tammakmik tahapkua allatkik ikaluit nalluyaoyut huli tahamani Kugluktumi Kuukmi.
Tahamna naunaiyaktaohimayok unipkalioktaovluni tahapkuninga ikaluit hiitokataktot iliitkuhiitnik ikalukpiit tatvalu hapkua Dolly Varden ikaluit ihuukit nayogagiyat tahamna Kugluktuk Kuukmi, ahiani taima pittakangitok immagiktumik Kuukmik hittuviovaktumik tahapkuninga allatkinguyunik ikalungnik. Ajikiiktoktut tagiokmut hiitovakhutik namungaokatakmangatalo tahapkua ikalukpiit tahapkulo ikaluit ihuukit Dolly Varden tatvalu ammugangata ukkiukhivikhamingnut (kullanut uvalunin natkannut tahaffuma Kuukmi kuukikningani) tahapkua ikaluit ihuukit Dolly Varden ayungnavakniaktot tatva hapkua ikaluknik naunaiyaiyiit havagiyaitnik hivunighami ihomalutaovaliaklikatjuk ikkilivalianingit. Hapkua ikalukpiit tatvalu hapkua ikaluit ihuukit Dolly Varden hiitukataktot Kugluktuni Kuukmit tatvalu tagiokmut Coronation Gulf-mut, uvanga takkukhimayatka tahapkua allatkit ikaluit ajitkingitot hiitugangat ingilgayangit ajikikatangitot ukkiuni. Takkukhimangmiyaga tahamna nuna manigaak hulitjutaongmiyok hittuniahaaktitlugit ikaluit tagiokmut. Taima atjikikatangitmata ikaluit hittuviat namungaukatakniitlo ikkayutaoniakuktat tahapkua ikaluit annaumatjutaitnik hila kannugininganik. Kihiani hivunikhami naunaiyainik pivaligiakaktok naninmangata tahapkua ikaluit igliliokviit tatvalu kannuvaklaak igliliokatakat kaoyivaliotiginahuaklugit kanok hunaniklo ullugiangaktomitjutait tatvalu kanok annaomatjuktikaohighaitnik tahapkua allatkik ikaluit tatvalu tuhaktinahuakutikhaitnik tahapkua ikaluhikinikut ataniktoiyot
Intelligent IoT Based Supply Chain For Fresh Produce: A Hybrid Reinforcement Learning And Optimization Approach
No full textFruits and vegetables form a vital component of the global economy; however, their distribution poses complex logistical challenges due to high perishability, supply fluctuations, strict quality and safety standards, and environmental sensitivity. In this thesis, we propose an adaptive optimization model that accounts for delays, travel time, and temperature variations impacting produce shelf life, and compare its performance against traditional methods such as Robust Optimization (RO), Distributionally Robust Optimization (DRO), and Stochastic Programming (SP).
Our adaptive model significantly outperforms traditional methods by enabling real-time route and temperature adjustments during transit. Empirical results using synthetic and IoT-derived data inspired by a realistic last mile delivery in Toronto show that the adaptive model improves average product shelf life by over 18% and reduces freshness deviation by 80%, with only a marginal increase in travel time. Furthermore, we introduce a Hybrid Model that combines pre-optimized static routes with real-time RL-based corrections. This approach mitigates the limitations of both static and reactive planning by following optimal routes under normal conditions and dynamically overriding them in response to disruptions such as traffic delays or temperature excursions.
Our results demonstrate that the proposed framework retains global efficiency while providing localized adaptability, making it a robust and practical solution for cold-chain logistics. This thesis thus offers a comprehensive, data-driven strategy to enhance sustainability, minimize spoilage, and increase responsiveness in fresh produce supply chains
Statistical Mechanics of Finite Length Semiflexible Wormlike Polymers
No full textThe wormlike chain is a fundamental model in polymer physics used for describing the statistics of semiflexible polymers. It is a general model applicable to many polymers, with double-stranded DNA being a notable example. Previous theoretical work has focused on long polymers, where subtle differences in the choice of statistical ensemble are not relevant. This worked well in explaining early data on polymer stretching, but as more modern techniques have allowed for the stretching of shorter, more rodlike polymers, finite length ensemble effects have become visible in experimental measurements and computer simulations. Here, these effects are computed, and a full picture of wormlike chain statistical mechanics is presented. The new results are compared against several decades of polymer stretching literature, and are found to describe previously unexplained behaviour. Finally, the broad use of the model is demonstrated by applying it to DNA wrapped carbon nanotubes, a system that requires considering polymer flexibility, and predicting the pitch of the helical structure formed by these complexes
Experimental investigation of the Structural Perfomance of Engineered Bamboo Composites (Dragonwood) in Jacking Applications
No full textClimate change has necessitated gravitation towards bio-based building materials. Many innovative, bio-based, structural products with exceptional strength and resistance, such as mass timber and bamboo composites have emanated from advances in adhesive chemistry and manufacturing to mitigate climate issues.
This study was conducted to investigate the structural performance of an engineered bamboo composite, namely Dragonwood, in jacking applications. While tropical hardwoods have been the common choice for jacking applications across North America; the decline in quality is now raising high level concerns with regards to their performance in jacking applications.
Engineered bamboo composites (EBCs) have been observed to be highly durable, resistant to fungal infection and show high strength to weight ratio. In terms of environmental sustainability, EBCs are a great substitute for tropical hardwoods since it can take as long as 60-80 years for hardwood to mature but bamboo can mature in 2-6 years. Furthermore, with EBCs showing superior long-term behavior under varying environmental exposure, many heavy-duty engineering companies involved in day-to-day jacking applications are incentivized to gravitate EBCs, soon.
The mechanical properties of the Dragonwood specimens were investigated experimentally in bending and compression based on the principal modes of failure to ascertain the performance of these beams in different orientations and loadings. Since the manufacture of Dragonwood involves face bonding two sections of parallel strand bamboo (PSB) boards to form a larger laminated veneer bamboo (LVB) section, glue line failure was also observed.
It was found that in bending, the primary failure mode in the specimens was simple tension as the fibers on the underside of the beams broke due to deflection. Horizontal shear failure was also observed along the glue line in some of the Dragonwood specimens. In compression, the failure mode of the Dragonwood specimens was an overall section buckling characterized by cracks and splits at the end. Regardless, the specimens still demonstrate bilinear behavior both in bending and compression as observed in the stress-strain graphs. With the Ekki specimens, the flexural response was independent of orientation. However, in compression, vertically oriented Ekki specimens were observed to fail in less time than horizontally oriented ones.
From the experimental results, the strength and modulus properties were evaluated, resulting deviations and variances were obtained, and Kolmogorov-Smirnov (K-S) tests were employed to determine the goodness of fit for comparison with known theoretical distributions. From the K-S tests, the experimental data demonstrated conformity with normal distribution
Will Canada's Bill C-8 Impact the Future of EU-Canada Cross-border Data Flows?
No full textCanada's proposed cyber security for critical infrastructure bill, Bill C-8, which reintroduces Bill C-26 from the previous Parliament (with minor tweaks), could lead to a re-evaluation of the European Commission's adequacy decision concerning Canada's data protection laws. As such, the bill could push Canada to the brink of a disruption in the framework governing cross-border data flows between the two jurisdictions. Such a scenario would create tremendous uncertainty for actors in the digital economy who routinely process European's personal data, such as airlines, financial institutions, information management service providers, cloud and data storage companies, and e-commerce platforms
Aging Under Pressure: Stress, Inflammation, and Cognitive Change in Immigrant and Non-Immigrant Canadians
No full textBackground
Cognitive impairment and its risk factors are a growing global concern, particularly among understudied populations such as immigrants. Physical health, psychosocial, and mental health stressors (“stress”) are all linked to poorer cognitive function. While immigrants are more likely than non-immigrants to experience adverse effects of stress, likely due to greater exposure to stressors, they may also experience unique psychosocial and mental health stressors. At the same time, they may benefit from physical health protective factors such as the “healthy immigrant effect”. However, whether their distinct stress profile increases their vulnerability to cognitive impairment remains unclear and was therefore the key focus of this dissertation. Further, because stress can elevate systemic inflammation, this research examined whether inflammation mediated the association between stress and cognitive function. The role of sex in this association was also explored, as immigrant women often experience higher levels of stress, which may amplify inflammatory responses and contribute to worse cognitive outcomes compared to immigrant men and non-immigrants.
Methods
All studies used data from the Canadian Longitudinal Study on Aging’s (CLSA) Comprehensive cohort, a prospective, population-based study of Canadians aged 45-85 at baseline (n = 30,097, including 5,449 immigrants). Structural equation models examined the association between baseline physical health (measured by physical health conditions), psychosocial (measured by barriers to social activities, financial need, and housing problems), and mental health (measured by psychological distress) stressors with executive function and memory at baseline and three-year follow-up. Analyses were stratified by immigrant status and sex, with inflammation (measured by C-reactive protein; CRP) tested as a potential mediator. Models were adjusted for age, education, and congruence between the participant’s first language learned and the language of the cognitive testing.
Results
Study 1: Physical health stress. Negative associations of physical health conditions with executive function and episodic memory were more consistent among non-immigrants than immigrants. In non-immigrants, significant negative associations were observed at both baseline and follow-up, whereas among immigrants, effects varied by sex. While immigrant women showed no association between physical health conditions and baseline episodic memory, they exhibited significant associations with all other cognitive outcomes. In contrast, for immigrant men, physical health conditions were only associated with baseline episodic memory and not with any other cognitive outcomes. These findings suggest that stress related to physical health conditions had a more limited role in cognitive outcomes for immigrant men compared to immigrant women and non-immigrant women and men. Although CRP significantly mediated some associations, the effects were clinically negligible.
Study 2: Psychosocial stress. Associations of psychosocial stress with executive function and episodic memory were observed in both immigrants and non-immigrants. However, immigrant women were the least likely to show significant associations between psychosocial stress and cognitive outcomes, while immigrant men were the most likely, showing stronger associations than immigrant women and non-immigrant women and men across all of the cognitive domains and time points. This pattern highlights the disproportionate impact of psychosocial stress on cognitive outcomes among immigrant men. While there were statistically significant mediations by CRP, they were clinically negligible.
Study 3: Mental health stress. Negative associations of psychological distress with executive function and episodic memory were observed in both immigrants and non-immigrants. However, immigrant women and men experienced more pronounced associations between psychological distress and baseline executive function than non-immigrant women and men. Notably, immigrant men also showed a strong association with baseline episodic memory, further emphasizing their susceptibility to the effects of mental health stress on cognition. While there were statistically significant mediations by CRP, they were clinically negligible.
Contribution
To our knowledge, no previous studies globally have measured the complex effects of stress and inflammation on cognition in aging immigrants. The findings align with the “healthy immigrant effect” as, despite physical health conditions being generally similar between immigrants and non-immigrants, their impact on cognition was greater among non-immigrants. This suggests that while stress related to physical health conditions was less strongly linked to cognition in immigrants, psychosocial and mental health stress may be more strongly associated with cognitive outcomes in this group. Notably, immigrant men were the most likely to show significant negative associations of psychosocial and mental health stressors with cognition, highlighting their particular vulnerability and a potential area for targeted intervention. While stress-related cognitive vulnerabilities were evident across all of the groups, the strength and consistency of these associations varied, suggesting that certain subgroups may be more vulnerable to stress and may benefit from targeted support. Although CRP significantly mediated some associations across all categories of stressors, the effects were consistently negligible, suggesting that systemic inflammation, as measured by baseline CRP, was not the primary mechanism linking chronic stress to cognition in these studies. By providing much-needed data on a diverse immigrant population—unlike much of the existing literature, which focuses on more homogeneous groups—these studies contribute to a broader global understanding of how stress impacts cognitive function in aging adults, with implications for public health and policy across different immigration contexts
Unraveling the Influence of Natural Organic Matter on Lead Release in Drinking Water Distribution Systems
No full textLead release in drinking water distribution systems remains a critical public health challenge, governed by chemistry of corrosion scales and their interactions with bulk water chemistry. Parameters such as pH, dissolved inorganic carbon, residual disinfectants, aluminum residuals, and corrosion inhibitors exert direct control over the solubility, transformation, and stability of lead-bearing components. Natural organic matter (NOM)—a heterogeneous assemblage of compounds produced by biological and geochemical processes—further complicates these processes. NOM can enhance metal mobilization through surface complexation, colloid stabilization, and modification of corrosion product surfaces.
This thesis investigates the role of NOM on lead in drinking water systems with emphasis on its characterization, its influence on corrosion scales, and its effects on lead release under variable chemical conditions. NOM from Southern Ontario, Canada, riverine and lacustrine sources was analyzed using complementary techniques like liquid chromatography–organic carbon detection (LC-OCD), fluorescence excitation–emission matrix (FEEM) spectroscopy, and solid-state 13C NMR. These methods identified distinct compositional differences between riverine and lacustrine NOM. Such compositional contrasts can be translated into differential affinities for forming complexes with corrosion products and varying propensities to generate mobile colloids.
A series of bench-scale galvanic corrosion cells simulating partial lead service line replacement were used to assess the effects of NOM type , NOM concentration, pH, dissolved inorganic carbon (DIC), residual aluminum, and orthophosphate on lead release under chloraminated conditions. Two-level factorial or half-fractional designs were used for experimental design. Statistical analyses, generalized additive mixed models (GAMM) and factorial analysis, were employed to evaluate the influence of studied factors and their combined impacts on lead release. These analyses consistently demonstrated that higher pH and DIC reduced total and dissolved lead release, while NOM enhanced dissolved lead mobilization. While aluminum had minimal impact in NOM-free conditions, its presence under NOM-rich conditions reduced lead concentrations. NOM also diminished the effectiveness of orthophosphate in reducing lead concentration, even under elevated pH.
Corrosion scales were analyzed to identify mineral phases and morphologies. Scale analysis confirmed the predominance of smaller hydrocerussite and/or cerussite in the presence of NOM.
Collectively, these findings provide mechanistic insight into the interplay between NOM, water chemistry, and corrosion control strategies. This research advances understanding of NOM–metal interactions and supports the development of more resilient strategies for managing lead in drinking water systems
Greenhouse gas fluxes from stormwater ponds and urban wetlands in southern Ontario
No full textUrban wetlands and stormwater ponds are an established component of stormwater management integrated with green infrastructure elements. The main aim of these developments is to serve as receptacles for stormwater runoff and mitigate the adverse impact of urbanization on water quality and quantity. While created for stormwater management, urban wetlands and stormwater ponds also provide essential ecosystem services, including sequestration of carbon and preservation of biodiversity while enhancing the aesthetic value of the surrounding environment. Despite these services, these small water bodies accumulate loads of organic matter and nutrients, which undergo different conditions (aerobic/anaerobic) and microbial processes, releasing significant amounts of greenhouse gases (GHGs) such as methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O). Design specification and exposure to aspects of the urban environment may affect the amount of GHGs released. Hence, this study aimed to quantify GHG emissions from 24 distinct stormwater ponds and urban wetlands in the Kitchener- Waterloo region, Southern Ontario, over a seven-month period from May to November and assess the impact of selected environmental, physical and chemical parameters on these GHG emissions. The average daily fluxes across the sampling period were 760 mg CO2 m-2 d-1, 417 mg CH4 m-2 d-1, and 0.23 mg N2O m-2 d-1. Seasonal variation was evident for CO2 and CH4 fluxes, whereas N2O fluxes showed minimal seasonal variation. For CO2, significant predictors included water temperature, pH, dissolved oxygen (DO), dissolved organic carbon and NO3- concentrations, and physical features, including sediment depth, pond depth, catchment area and dredging. Methane emissions were primarily driven by in-situ environmental variables, including water temperature, DO concentration and pH, while chemical and physical factors did not significantly influence CH4 fluxes. For N2O, key drivers included NO3- concentration, DO concentration, electrical conductivity and sediment depth. These findings highlight the complex and dynamic role of stormwater management facilities in GHG emissions and the importance of seasonal changes and abiotic factors in shaping emission patterns