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Large-scale structures in two-dimensional Rayleigh–Bénard convection driven by fixed heat fluxes
No full textExistence of large-scale structures in two-dimensional Rayleigh--B\'enard convection is investigated in the case of boundaries that are no-slip and have fixed heat fluxes. Direct numerical simulations are carried out using the code Dedalus, which implements spectral methods. Simulations are carried out in a horizontally periodic domain, primarily with a horizontal period 20 times the layer height. The large-scale structure of interest is a pair of wide convection rolls. After finding one such two-roll state at fixed values of the Rayleigh number and Prandtl number , the parameters are varied slowly in time to find two-roll states elsewhere in the -- plane. Loss of a two-roll state occurs by transition to a four-roll state, which is detected using several criteria. The -- plane is divided into one region where we have found two-roll states that persist, and one region where we have not. Along part of the boundary between these regions the two-roll states are steady, suggesting that their break-up is a linear instability. Elsewhere in the -- plane the boundary is hard to locate precisely because the two-roll states are unsteady and can display metastable behaviour. The two-roll regime is found only when is sufficiently small and is sufficiently large, and these two-roll states are further classified as steady or unsteady. Contrasting our findings with simulations in the literature that have different boundary conditions and/or are three dimensional, we find that existence or nonexistence of large-scale structures is substantially affected by both thermal and velocity boundary conditions and by dimension. A simple model with one fitting parameter is found to capture the middle region of a wide roll at various parameter values, and partial results are presented towards using this model to understand the region in the -- plane at which two-roll states are found.Graduat
An examination of the use of the chemotherapy drug doxorubicin, gold nanoparticles, and radiation in combined cancer therapy
Full text linkThe chemotherapy drug doxorubicin (DOX) is a widespread and effective treatment for many different types of cancer. However, it is known for causing significant and dangerous side effects due to high cardiotoxicity. Gold nanoparticles (GNPs) are a promising field of nanomedicine due to their stability, customizability, and radiosensitization properties as demonstrated using in vitro and mice models. They accumulate preferentially in tumours due to the enhanced permeability and retention effect. The combination of GNP mediated radiotherapy and DOX has the potential to deliver highly targeted and effective therapeutics while sparing surrounding healthy tissue.
This work used GNPs conjugated with PEG and RGD, DOX, and radiotherapy in combination to investigate possible synergistic cancer therapeutics. MDA-MB-231 cells were dosed for 48 hours with GNPs at a clinically relevant concentration of 7.5 μg/mL. DOX was dosed at the measured IC50 concentration of 144.4 nM for a 48 hour exposure. Radiation doses of 2 Gy and 5 Gy were used, as 2 Gy is commonly used for fractionated radiotherapy and recent clinical trials have also shown 5 Gy to be an effective fractionated radiation dose.
A cytotoxicity assay was conducted to determine the IC50 of DOX which was used as the dosing concentration for all other assays. Live cell images were taken to demonstrate the internalization of DOX and GNPs in the cells. To quantify if DOX affected the uptake of GNPs into the cells, a cellular uptake study was conducted. As previous research has indicated that DOX causes cell cycle arrest, a cell cycle assay was conducted. To assess the cytotoxicity and radiosensitization properties of GNPs and DOX, a cellular proliferation study and a clonogenic assay were conducted. Additionally, a DNA double strand break assay was conducted to assess the amount of DNA damage caused.
The cellular uptake study revealed that DOX caused an increase in GNP uptake, with (1.27±0.16)×10^6 GNPs per cell when treated with DOX, and (0.76±0.05)×10^6 GNPs per cell when untreated. DOX showed evidence of radiosensitization in the proliferation assay with the combination of DOX and radiation causing a (54±2)% reduction in cell growth when 2 Gy was administered, and a (69±8)% reduction in cell growth when 5 Gy was administered. However, this effect was not synergistic. In the other assays conducted, DOX caused cell cycle arrest, extensive DNA damage, and no clonogenic growth. It was concluded that DOX was inducing senescence at the given dose.
GNPs showed some radiosensitization in the proliferation assay at 2 Gy, with (24±2)% reduction in growth after 3 days in the 2 Gy GNP sampled compared to (15±2)% reduction in growth in the 2 Gy control sample. No other significant differences in growth due to GNPs were seen in the proliferation assay. The clonogenic assay showed that 2 Gy radiation caused a (67±5)% decrease and 5 Gy caused a (97.9±0.6)% decrease in clonogenic survival of cells treated with radiation only when compared to the unirradiated control. The GNP incubated sample demonstrated some radiosensitivity in the clonogenic assay as it had a (78±3)% lower surviving fraction when irradiated with 2 Gy then the unirradiated control. The GNPs also showed toxicity in the unirradiated sample, with (30±11)% lower surviving fraction than the control in the clonogenic assay. A Bliss independence test found the GNPs and 2 Gy radiation to have independent effects. There was no significant difference between the GNP and control cells in the clonogenic assay when irradiated with 5 Gy. The DNA double strand break assay showed that 2 Gy radiation caused an increase in DNA damage foci from 2.0±0.2 to 5.1±0.5 foci per cell. No significant difference in foci was seen between the control and the GNP incubated cells.
While the results from this work did not demonstrate a conclusive benefit from the combined therapy of doxorubicin, GNPs, and radiation, the system is still of interest. Future experiments could be performed using a reduced doxorubicin concentration such as the IC20, to reduce the toxicity while still causing an effect. If a synergistic effect can be observed, it could be exploited to significantly reduce normal tissue toxicity in cancer patients while still delivering a lethal dose of chemotherapy and radiotherapy to the tumour.Graduat
Artificial Intelligence and Primary Care: Perceptions and Applications in Medical Clinic Operations
No full textArtificial intelligence (AI) has the potential to improve health care, both for clinical and non-clinical purposes. Primary care is the entry point for patients into the health care system. Recent years has seen an increase in the demand for primary care, as well as issues such as staffing shortages, and increasing costs. AI can help to alleviate these issues by streamlining administrative and operational processes.
This study investigates the perspectives and applications of AI in medical clinic operations. A mixed-methods approach was utilized, involving a scoping review, survey, and interviews. The scoping review intends to identify relevant literature and the state of knowledge. A survey to local clinic managers and physicians was also conducted to determine their perspectives of AI. The survey received 15 responses from 22 individual invited medical clinics in the Victoria region, resulting in a final response rate of 68.2%. Survey respondents were also invited to participate in interviews to gather more contextual information about their survey responses.
This study finds that there is significant interest in the potential application of AI, including for health care operations. However, AI technologies are still largely not being used yet. This is supported by the findings of the scoping review and survey. Interviewed clinics also highlight their current usages of ChatGPT for non-clinical workflows.Jamie Cassels Undergraduate Research Awards (JCURA)UndergraduateReviewe
Joint adaptive transmission and numerology selection for 5G NR PDSCH with DQN-based reinforcement learning solution
No full textThe mission critical applications such as industrial automation, remote surgery and autonomous transportation systems demand low-latency, high-reliability communications service. As such, there is an urgent need to optimize transmission technologies in 5G New Radio (NR) to support Ultra-Reliable Low-Latency Communication (URLLC).
This project introduces a joint adaptive transmission and numerology selection scheme for Physical Downlink Shared Channel (PDSCH) in 5G NR, targeting URLLC support. The transmission scheme selection problem is modeled as a Markov Decision Process (MDP). A Deep Q-Network (DQN) reinforcement learning agent is trained to dynamically adjust Modulation and Coding Scheme (MCS) and numerology based on real-time channel conditions and latency constraints.
To evaluate the performance, we develop custom simulation environment by implementing PDSCH transmission model under frequency-selective fading channels, incorporating the Hybrid Automatic Repeat reQuest (HARQ) mechanism. The results demonstrate that the DQN agent effectively reduces transmission delays and improves reliability by optimizing transmission parameters. This approach enhances performance for 5G NR in URLLC support, achieving both higher reliability and lower latency than conventional adaptive transmission system.Graduat
Examining and comparing the energy expenditure of two modes of a virtual reality fitness game (Supernatural): Indirect calorimetry study
Full text linkBackground: The effectiveness of virtual reality (VR) fitness games as a form of moderate to vigorous physical activity has yet to be thoroughly quantified through gold standard energy expenditure measures.
Objective: The purpose of this study was to examine the energy expenditure of 2 medium-intensity modes (“Flow and “Boxing”) of a VR fitness game, Supernatural, using indirect calorimetry.
Methods: Indirect calorimetry was used to examine relative and objective maximal oxygen consumption (VO2 max), metabolic equivalents of task (METs), and calories burned during medium-intensity bouts of both Flow and Boxing gameplay modes in young (mean age 25.42, SD 3.25 years), active individuals (n=12 female and n=11 male). METs and calories were also compared using a triaxial waist-worn accelerometer, an Apple smartwatch, and a VR headset. Mood states were assessed pre- and postbout using the shortened Profile of Mood States Questionnaire. Paired 2-tailed t tests were used to examine differences in game modes, between sexes, and pre-post exercise sessions.
Results: Objective and relative VO2 max averaged 1.93 (SD 0.44) L/min and 27.61 (SD 5.60) mL/kg/min, respectively, between modes. Flow (mean 8.2, SD 1.54 METs) and Boxing (mean 7.6, SD 1.66 METs) are both classified as high energy expenditure, vigorous activities. Calorie expenditure data of the accelerometer and VR headset differed significantly from the metabolic cart. Mood changes pre- to post exercise were consistent with expected values for moderate- to vigorous-intensity physical activity, with participants reporting that they felt more “active,” “full of pep,” “vigorous,” and “lively” (P<.05) following bouts. Male individuals reported higher objective oxygen consumption (VO2) for both Flow and Boxing modes; no other sex-specific differences were observed.
Conclusions: Both Flow and Boxing gameplay modes of Supernatural classify as vigorous physical activity and demonstrate the potential to promote mental and physical health benefits. Supernatural may be an effective exercise modality in a VO2 training program.This research was commissioned and funded by Supernatural.FacultyReviewe
A methodological approach to extracting patterns of service utilization from a cross-continuum high dimensional healthcare dataset to support care delivery optimization for patients with complex problems
Full text linkBackground: Optimizing care for patients with complex problems entails the integration of clinically appropriate problem-specific clinical protocols, and the optimization of service-system-encompassing clinical pathways. However, alignment of service system operations with Clinical Practice Guidelines (CPGs) is far more challenging than the time-bounded alignment of procedures with protocols. This is due to the challenge of identifying longitudinal patterns of service utilization in the cross-continuum data to assess adherence to the CPGs. Method: This paper proposes a new methodology for identifying patients’ patterns of service utilization (PSUs) within sparse high-dimensional cross-continuum health datasets using graph community detection. Result: The result has shown that by using iterative graph community detections, and graph metrics combined with input from clinical and operational subject matter experts, it is possible to extract meaningful functionally integrated PSUs. Conclusions: This introduces the possibility of influencing the reorganization of some services to provide better care for patients with complex problems. Additionally, this introduces a novel analytical framework relying on patients’ service pathways as a foundation to generate the basic entities required to evaluate conformance of interventions to cohort-specific clinical practice guidelines, which will be further explored in our future research.FacultyReviewe
Let's C the phase of photons for quantum computers
No full textPhysics - Three Minute Thesis FinalistA thesis exploring the mysterious nature of photons and their potential for technological advancements, focused on manipulating single photons by constructing a gate that controls the phase of light, which can be seen as a time delay.Graduat
Improving situation awareness to reduce healthcare-acquired urinary tract infection
Full text linkReducing healthcare-acquired urinary tract infections (HAUTI) is a common goal among healthcare providers and organizations. Nurses' situation awareness (SA) skills would likely improve patient status recognition and prevent healthcare-acquired urinary tract infections. Healthcare providers, such as nurses, need eHealth systems that support their situation awareness as they provide care.
Integrating Endsley's design principles with machine learning offers a promising approach for developing an SA-oriented dashboard that could help reduce HAUTI. This study takes an initial step toward this goal by exploring context-based variables contributing to HAUTI. I included a comprehensive list of nursing assessments and implemented multiple methodologies to handle the datasets and address missing data. The XGBoost model emerged as the most effective model in predicting HAUTI, isolating factors such as improving skin integrity and mobility and monitoring neurological status as key factors in reducing HAUTI rates. However, these results should be carefully interpreted, given this study's significant missing data. The finding of this study reinforces the necessity of high-quality data to support the interpretation of Machine Learning (ML) models in clinical settings.Graduat
Differential cross-section measurements of WbWb production in the lepton+jets channel at √s = 13 TeV with the ATLAS detector
Full text linkThe top quark provides a unique opportunity to test the Standard Model of particle physics. Its heavy mass causes it to decay before it can hadronize, allowing for the study of the properties of a bare quark. This thesis presents differential cross-section measurements stemming from various top quark processes. This measurement is conducted in the presently uncovered semileptonic channel, where one W boson decays leptonically and the other decays hadronically. The analysis is motivated by the need to improve the modeling of the interference effects between singly-resonant and doubly-resonant top quark decays. This effect has been the source of significant modeling uncertainties in other top-sector analyses. The data and simulation used to perform this analysis correspond to the full ATLAS Run 2 dataset, collected 2015-2018. This data corresponds to an integrated luminosity of 140 fb^{-1} and a center of mass energy of √s = 13 TeV. The measured cross-sections are compared to predictions using different combinations of MC generators. Together with a complementary analysis in the dileptonic channel, this thesis provides a means to constrain modeling uncertainties towards the development of an all-inclusive bb4l generator. This generator could model all top quark processes while accurately accounting for all interference effects.Graduat
Erosion of stumble correction evoked with superficial peroneal nerve stimulation in older adults during walking
Full text linkIn healthy young adults, electrical stimulation of the superficial peroneal cutaneous nerve (SPn) innervating the dorsum of the foot has been shown to elicit functionally relevant reflexes during walking that are similar to those evoked by mechanical perturbation to the dorsum of the foot during walking and are referred to as stumble corrective (obstacle avoidance) responses. Though age-related differences in reflexes induced by mechanical perturbation have been studied, toe clearance has not been measured. Further, age-related differences in reflexes evoked by electrical stimulation of SPn have yet to be determined. Thus, the purpose of this study was to characterize age-related differences between healthy young adults and older adults with no history of falls in stumble correction responses evoked by electrical stimulation of the SPn at the ankle during walking. Toe clearance relative to the walking surface along with joint displacement and angular velocity at the ankle and knee and EMG of the tibialis anterior, medial gastrocnemius, biceps femoris and vastus lateralis were measured. The combined background and reflex toe clearance was reduced in the older adults compared with the young in mid-early swing (p = 0.011). These age-related differences likely increase fall risk in the older adult cohort. Further, age-related changes were seen in joint kinematics and EMG in older adults compared with the young such as decreased amplitude of the plantarflexion reflex in early swing in older adults (p < 0.05). These altered reflexes reflect the degradation of the stumble corrective response in older adults.FacultyReviewe