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Recent Submissions
Eye Movements: Measuring Fatigue and Attention in Natural and Urban Scenes
(University of Waterloo, 2025-10-17) Srikantharajah, Jatheesh
Exposure to nature can improve affective and cognitive states, reducing stress and arousal. Across four experiments, I measured eye movements when viewing natural and urban environments in the laboratory, recording changes in visual exploration and fatigue. My dissertation formally investigates the relationship between affective preference and visual exploration. For the first time, I gathered data from microsaccades to measure changes in fatigue and arousal while people view natural and urban environments. Natural scenes involved longer and more frequent fixations than urban scenes. I measured blink rates and microsaccade slopes as eye movement indicators associated with arousal and fatigue. These measures indicated that viewing natural scenes involved lower arousal than urban scenes. For static natural and urban scenes, preference was associated with increased fixation count. In experiment 2, I found that fractal complexity influences visual exploration and preference. More complex scenes elicited shorter saccades and were more pleasant, especially for urban scenes. In experiment 3, I contrasted different types of natural and urban environments. I showed that historic architecture was preferred to modern architecture, and that it involved lower fatigue and more exploratory eye movements. In experiment 4, I showed that differences in visual exploration and arousal between natural and urban scenes remained significant when using video stimuli, and when depleting attention beforehand using a sustained attention task. As eye-tracking grows in popularity for measuring experiences in architectural and natural environments, these experiments provide a valuable resource for understanding the relationship between eye movements, affective processing, and fatigue.
Fourier Analysis of Local Fell Groups
(University of Waterloo, 2025-10-17) Vujičić, Aleksa
In 1972, Bagget showed that a separable locally compact group G is compact if and only if its dual space G^ is discrete. Curiously however, there are non-discrete groups whose duals are compact, and such a group was identified in the same paper. In a similar vein, one can define the “Fell group”, a semidirect product of the units of the p-adic integers 𝕆ₚ* acting via multiplication on the p-adic numbers ℚₚ, which Baggett shows is a noncompact group whose dual is not countable. This Fell group forms a basis of the novel work presented in this thesis.
In Chapters 3 and 4, we look at the more general setting of the p-adic integers and numbers, known respectively as discrete valuation rings (DVRs) and local fields. We compile many known results about these objects, in order to generalise the theory of the Fell group to what we call the “local Fell groups”. While this is primarily background material from a variety of sources, there is additional work required to extend these results so that the theory is coherent and complete. We also briefly study finite-dimensional vector spaces over local fields.
In Chapter 5, we analyse the Fourier and Fourier-Stieltjes algebras of these local Fell groups, which are of the form A ⋊ K for A abelian and K compact. These local Fell groups fall into a particular class of groups induced by actions for which the stabilisers are ‘minimal’, and we call such groups “cheap groups”. For groups of this form, we show that B(G) = B∞(G) ⊕ A(K) ∘ qK, where B∞(G) is the Fourier space generated by purely infinite representations. We also show that in group with countable open orbits (such as the local Fell groups) this simplifies further to B(G) = A(G) ⊕ A(K) ∘ qK. In an attempt to generalise this to higher-dimensional analogues, for which the above does not hold true, we examine the structure of B∞(G). In particular, we obtain a result for dimension two in terms of the projective space, and we show that this is in some sense the ‘best’ decomposition that can be made.
Finally in Chapter 6, we study the amenability of the central Fourier algebra ZA(G) = A(G) ∩ ZL1(G) for G = 𝕆ₚ ⋊ 𝕆ₚ and its local field equivalents. We show that ZA(G) contains as a quotient the Fourier algebra of a hypergroup, which is induced by action of 𝕆ₚ* ↷ 𝕆ₚ. In general, if H is a hypergroup induced by an action K ↷ A, then there is a corresponding dual hypergroup H^ by the dual action. When this is the case, we show that these satisfy A(H) ≅ L1(H^), mimicking the classical result for groups. We also show that if H^ has orbits which ‘grow sufficiently large’, then via a result of Alaghmandan, the algebra L1(H^) is not amenable. In particular, this shows that ZA(G) is also not amenable, reaffirming a conjecture of Alaghmandan and Spronk.
Reparative Infrastructure: Reimagining Water Kiosks in Ulaanbaatar’s Ger Districts
(University of Waterloo, 2025-10-17) Liu, Yiqing
Over half of Mongolia’s population lives in Ulaanbaatar, with many settling in ger districts on the urban periphery. These areas, where some residents still live in traditional gers on self-claimed plots, resemble other informal settlements lacking basic infrastructure. Following the political reforms of the late twentieth century, many rural migrants relocated here seeking better opportunities, yet their living conditions remain poor. This thesis investigates how architectural interventions can enhance daily life, public space, and a sense of nomadic identity within these rapidly urbanizing areas. Focusing on the water kiosks system, it explores how these kiosks can serve as social and spatial anchors for future development. Based on literature review, secondary data, and remote site analysis, the thesis proposes two architectural upgrades in Bayangol District. The study ultimately frames a community-driven approach for informal settlements that promotes local agency and spatial justice through reparative infrastructure.
Electroretinograms following short-term chromatic light adaptation in high myopes and non-myopes
(University of Waterloo, 2025-10-17) Bidarkar, Ashita
Purpose: Worldwide, myopia cases are on the rise and the need for finding a definitive
mechanism by which myopia develops has become more imperative than ever before.
Axial elongation in myopic eyes is linked to short wavelength (λ) light-dependent increases
in retinal dopamine (DA). DA is associated with enhanced electroretinogram (ERG) amplitudes.
This thesis seeks to examine short-term adaptation to short and long λ light at
moderate and strong levels. I hypothesize that short λ light exposure differentially affects
full-field ERGs (ffERGs) and central ERGs in myopic eyes compared to controls.
Methods: In a multi-visit cross-over design, we compared ERGs before and after
20 minutes of full-field adaptation to long (red LED peak λ (λ 627 nm) or short (blue
LED peak λ 448 nm) λ light (Espion ColorDome™, Diagnosys LLC). Human participants
(ages 18-30) were healthy high myopes (≤-5 diopters (D)) and emmetropes (+1 D to -
0.25 D). Monocular, light-adapted (LA) ffERGs were recorded using skin electrodes and a
handheld system that adjusted for pupil diameter in real time (RETeval™). ERG stimuli
were LA standard white flash and flicker (85 Td.s), presented at 2 and 28.3 Hz, respectively.
The a-wave, b-wave and flicker ERG amplitudes, and implicit times were compared as
a function of pre/post adaption (time), adapting stimulus (λ), and refractive error (RE)
group using a mixed model ANOVA. Monocular multi-focal ERGs (mfERGs; 61 hexagons)
and pattern ERGs (PERGs; 15° field, 15’ reversing checks) were recorded with natural
pupils in keeping with ISCEV standards using DTL electrodes. The Espion™ console and
amplifier (Diagnosys LLC) was used for both ERG tests. The primary outcome measures
analyzed were the amplitudes and implicit times of the mfERG central wavelet, mfERG
average of the surrounding rings and the PERG P50 peak and were compared as a function
of pre/post adaption (time), adapting stimulus (λ), and RE group using a mixed model
ANOVA.
Results: There were no significant differences between controls and myopes prior to
adaptation (all p≥0.05) for ffERG tests. The luminance of the light had an effect such
that changes in b-wave implicit time decreased with adaptation to 300 cd/m² light in
controls (blue 30: -0.451 ± 1.28%; blue 300: -2.28 ± 2.56%; p≤0.001, η2G=0.14) but less
so in the high myope group (blue 30: +0.05 ± 1.3%; blue 300: -1.26 ± 2.43%; p=0.01,
η2G=0.05). Changes in flicker implicit time decreased with the stronger luminance level
but were not different between refractive error groups (i.e. controls: blue 30: 0.15 ± 1.0%;
blue 300: -1.05 ± 1.61%, myopes: blue 30: +0.44 ± 2.74%; blue 300: -1.1 ± 1.50%,
p≤0.001, η2G=0.13). Stronger light conditions caused b-wave amplitudes to become less
negative (smaller) (i.e. controls: blue 30: –5.38 ± 15.6%; blue 300: –3.50 ± 17.7%, myopes:
blue 30: –10.9 ± 15.4%; blue 300: +0.85 ± 10.9%, p=0.02, η2G=0.05). Similarly, with
v
flicker amplitudes, they became less negative (smaller) with stronger luminance adaptation
(i.e. controls: blue 30: –4.1 ± 13.4%; blue 300: –0.62 ± 17.1%, myopes: blue 30: –9.9 ±
18.3%; blue 300: +4.7 ± 12.0%, p=0.00, η2G=0.07). When comparing between controls
and high myopes or between short and long wavelengths, changes in b-wave amplitudes
did not differ. There was a significant difference between RE groups for the PERG P50
amplitude prior to adaptation (p=0.03; Cohen’s d=1.06) such that they were significantly
smaller in myopes (2.63 ± 1.0 μV) than controls (3.95 ± 1.5 μV). The N95 amplitudes
were also smaller (i.e. less negative) in myopes (-4.39 ± 1.82 μV) than controls (-6.58 ±
1.55 μV; p= 0.01; Cohen’s d=-1.3). The mfERGs showed no significant pre-adaptation
RE differences (all p≥ 0.05; all η2G≤ 0.07). For the PERG, in both controls and myopes,
the change in N95 amplitudes decreased more with long λ light (controls: -16.6 ± 23.4%;
myopes: -24.7 ± 43.4%) than short λ light (controls: +10.4 ± 23.5%; myopes: +1.88 ±
26.7%; p≤ 0.001; η2G=0.541). There were no effects of adaptation on the P50 amplitude
or implicit time. For mfERG, the change in N1P1 magnitude was not different between
controls and myopes and was not different when comparing λs for any of the five rings (p≥
0.05).
Conclusions: There is no evidence that chromatic adaptation has a differential effect
on post-adaptation ffERGs in high myopes. Long λ adaptation, especially with stronger
luminance, prolongs ERG implicit times, probably reflecting relatively reduced input from
the faster long cone system. There is evidence to suggest smaller central retinal responses
with the PERG P50 but not with the central wavelet of the mfERG, indicating altered
retinal ganglion cell function but not altered central inner retinal function in young adults
with myopia. Further studies should focus on confirming whether altered central retinal
function persists in adult myopes and whether longer adaptation times would yield a greater
RE difference.
IN BETWEEN LAND AND SEA: Adaptive Redevelopement of the Indigenous Fishing Villages at Mumbai’s Coastal Fringes
(University of Waterloo, 2025-10-17) Dasgupta, Ahan
Architecture is often understood through the spaces it produces, but its more significant role
lies in framing the relationships between people, economies, and environments. When
these relationships are disrupted by ecological change and urban expansion, the focus of
architecture shifts from form to the conditions that allow communities to endure.
In the city of Mumbai, this shift is most visible along the coastline, where reclamation,
large-scale infrastructure, and speculative real estate have steadily eroded ecological
systems. Within this changing landscape, the fishing villages of the Koli community, the city's
native inhabitants, continue to function as active settlements that support both livelihoods
and cultural practices, even as they are reclassified as informal and placed under pressure
from redevelopment.
This thesis proposes a framework that responds to the challenges faced by the Koli
community through an integrated approach. Ecological restoration is established as the
foundation, focusing on mangrove regeneration, wetland protection, and the preservation
of tidal flows. Economic resilience is addressed through cooperative infrastructure,
including fishing hubs, repair yards, and storage facilities, which strengthen small-scale
fishing practices. Cultural presence is supported through plazas, markets, and promenades
that keep Koli life embedded within the public realm of the city. Through this lens, the thesis
reframes the coastline of the Khar-Danda Village as a shared edge where ecological
systems, livelihoods, and cultural practices are sustained together.