University of Ottawa

We consider the problem of learning a neural network classifier. Under the information bottleneck (IB) principle, we associate with this classification problem a representation learning problem, which we call “IB learning”. We show that IB learning is, in fact, equivalent to a special class of the quantization problem. The classical results in rate-distortion theory then suggest that IB learning can benefit from a “vector quantization” approach, namely, simultaneously learning the representations of multiple input objects. Such an approach assisted with some variational techniques, result in a novel learning framework, “Aggregated Learning”, for classification with neural network models. In this framework, several objects are jointly classified by a single neural network. The effectiveness of this framework is verified through extensive experiments on standard image recognition and text classification tasks.

This article examines the possibilities engendered by land-based analyses within the sociology of sport. We examine how “Canada’s” Truth and Reconciliation Commission’s calls to action on sport reproduce a logic of social inclusion, one which assimilates Indigenous athletes and Peoples into settler models of sport. To consider epistemological tools for unsettling settler sport systems, we turn to critical Indigenous scholarship on land-based analyses and pedagogies. To illustrate the possibilities of land-based analyses, we examine lacrosse, an Indigenous sporting practice with roots embedded in relational interconnectedness with the land. A land-based approach to sport offers opportunities for revising the assumptions, values, and ethics underpinning settler models of sport through, for example, emphasizing the importance of community, healing, and land stewardship.

The low-degree method postulates that no efficient algorithm outperforms low-degree polynomials in certain hypothesis-testing tasks. It has been used to understand computational indistinguishability in high-dimensional statistics. We explore the use of the low-degree method in the context of cryptography. To this end, we apply it in the design and analysis of a new public-key encryption scheme whose security is based on Goldreich’s pseudorandom generator. The scheme is a combination of two proposals of Applebaum, Barak, and Wigderson, and inherits desirable features from both.

Background Annual respiratory syncytial virus (RSV) epidemics disproportionately impact infants and young children. Clinical surveillance is often restricted to laboratory-confirmed hospitalizations. Built environmental surveillance through floor sampling may provide population-level insights into RSV transmission dynamics and inform public health action to blunt community outbreaks.Figure:Quantification of viral detection from floor swabs in the pediatric emergency department by multiplex PCR Each point represents the number of viral copies, plus one, detected from a swab captured at a given location (y-axis) on a given date (x-axis). A value of one copy indicates non-detection of RSV. Methods A prospective environmental surveillance study was conducted in Ottawa, Canada from November 24, 2022 to March 24, 2023. Floors were swabbed in six areas of the emergency department (ED) of the sole pediatric acute care facility in Eastern Ontario. Samples were tested for RSV by a validated multiplex PCR assay. Floor swab positivity was compared to hospitalization data of patients with laboratory-confirmed RSV using Pearson’s correlation analysis to determine the degree of their association. Results Over an 18-week period, 432 floor swabs were collected in the ED and 250 pediatric patients were hospitalized. RSV was detected in 65% of floor swabs, with more viral copies detected in congregate areas (waiting rooms, triage) (Figure). The correlation between swab positivity and RSV hospitalizations was 0.64 (95%CI 0.23-0.86). Conclusion RSV was frequently detected on floors in the hospital-built environment and correlated somewhat with hospitalizations, likely reflecting community viral prevalence rather than severe RSV disease. Having real-time floor signals in different areas of the ED allowed for spatial resolution of the signal intensity, identifying higher RSV burden in areas where patients with infectious symptoms were more likely to congregate for prolonged periods of time. Floor sampling may be useful in developing spatially-refined approaches to infection prevention and control measures, particularly in indoor areas with increased respiratory viral transmission risks. Disclosures Evgueni Doukhanine, MSc, DNA Genotek: DNA Genotek provided sampling swabs in-kind for this study in an unrestricted fashion. Michael Fralick, MD, ProofDx: Advisor/Consultant

Background Environmental testing for SARS-CoV-2 including assessment of wastewater and the built environment is a useful tool for population-level surveillance for COVID-19. Detection of SARS-CoV-2 on the floor of healthcare facilities has been strongly associated with cases of COVID-19 (1,2). By introducing routine floor-swabbing in hospitals, we may be able to predict outbreaks earlier allowing for additional control measures. Methods We implemented floor swabbing surveillance for SARS-CoV-2 to aid the identification of COVID-19 cases and outbreaks in hospitals. Swabs were taken weekly at eight hospital in-patient wards in healthcare worker-only (HCW) areas at two hospitals in Ontario, Canada, for a 39-week period (July 2022 to March 2023). HCW cases and outbreaks were managed as per usual processes at the facilities. A logistic regression model with ward-level random intercepts was developed using weekly viral copies (VC) to predict a contemporaneous outbreak in the same ward in the same week. Grouped 5-fold cross-validation was used to evaluate model outbreak discrimination. Results SARS-CoV-2 RNA was detected on 537 of 760 collected swabs (71%). Hospital A had more frequent detection and higher levels of SARS-CoV-2 (swab positivity = 90% [95% CI: 85%-93%], mean VC = 23, [19-29]) than Hospital B (swab positivity = 60% [55%-64%], mean VC = 7.9 [6.5-9.7]) (Figure 1). There were seven outbreaks at Hospital A and four at Hospital B. Outbreaks at both hospitals consisted of mostly patient cases (Hospital A: 95%, Hospital B: 82%). The odds ratio of outbreak for every unit increase in viral copies (log-transformed) was 21.0 [5.6-79]. The cross-validated area under the receiver operating curve for SARS-CoV-2 viral copies for predicting a contemporaneous outbreak (Figure 2) was 0.86 [95%CI 0.82 – 0.9]. Figure 1. Distribution of SARS-CoV-2 copies (plus one) values from PCR testing of floor swabs, stratified by hospital and outbreak status at time of sampling. Jittered points show the copies plus one values for each individual swab; boxplots show the median, IQR, and range of these values by site (indicated by colors), in outbreak and non-outbreak periods (indicated on y-axis). Figure 2. Cross-validation receiver operating characteristic (ROC) curves (with mean ROC in blue) for predicting contemporaneous outbreaks from SARS-CoV-2 viral copies. Conclusion Detection of SARS-CoV-2 on floors in HCW-only areas is associated with COVID-19 outbreaks in those hospital wards. Despite swabbing exclusively in HCW-only areas, outbreaks were driven by patient cases at both hospitals. These results support the potential role for built environment sampling to support hospital COVID-19 outbreak identification and may fill gaps in traditional clinical surveillance methods. Disclosures Evgueni Doukhanine, MSc, DNA Genotek: DNA Genotek provided sampling swabs in-kind for this study in an unrestricted fashion. Michael Fralick, MD, ProofDx: Advisor/Consultant

Positron emission tomography (PET) is a highly sensitive molecular imaging technique that uses radioactive tracers to map molecular and metabolic processes in living animals. PET can be performed as a stand-alone modality but is often combined with CT to provide for objective anatomical localization of PET signals in a multimodality approach. In order to outline the general approach to evaluating four mice simultaneously by dynamic PET imaging, the use of the aldehyde-targeted radiotracer [18F]NA3BF3 in mouse models of hepatotoxicity will be described. Indeed the production of aldehydes is upregulated in a wide range of disease and injury, making them a suitable biomarker for PET imaging of numerous pathologies.

Electrical cardioversion for atrial fibrillation/atrial flutter (AF/AFL) is common in the ED. Our previous work showed that hypotension and respiratory events were important adverse events that occurred in patients undergoing electrical cardioversion for AF/AFL. The purpose of this study was to examine if (1) beta-blockers or calcium channel blocker use prior to ECV were associated with hypotension and (2) medications used for procedural sedation were associated with respiratory events. This was a secondary analysis of pooled study data from four previous multicentred studies on AF/AFL. We conducted a multivariable logistic regression to examine predictors of hypotension and respiratory adverse events. There were 1736 patients who received ECV. A hypotensive event occurred in 62 (3.6%) patients. There was no significant difference in the odds of a hypotensive event in patients who received a beta-blocker or calcium channel blocker in the ED compared to no rate control. Procedural sedation with fentanyl (OR 2.01 95% CI 1.15–3.51) and home beta-blocker use (OR 1.92, 95% CI 1.14–3.21) were significantly associated with hypotensive events. A respiratory event occurred in 179 (10.3%) patients. Older age (OR 2.02, 95% CI 1.30- 3.15) and receiving midazolam for procedural sedation were found to be significantly associated with respiratory events (OR 1.99, 95% CI 1.02–3.88). Beta-blocker or calcium channel blocker use prior to ECV for AF/AFL was not associated with hypotension. However, sedation with fentanyl and home beta-blocker use was associated with hypotension. The use of midazolam for procedural sedation was significantly associated with respiratory events.

I offer a theory of advice. The theory has two parts: an account of the nature of advice, and an account of the quality of advice. In Sect. 2 I defend this definition: Advice: P advises R to X iff P communicates about X-ing to R in a manner that intentionally presents X-ing as worth reasoning to by R. In Sect. 4, I defend a tripartite account of the quality of advice: the standards relevant to whether advice is good concern rational agency in general, the advisee’s particular situation, and the topic of the advice. These accounts of the nature and quality of advice are superior to extant alternatives on the basis of both descriptive adequacy and absurdity.

During the recent pandemic of COVID-19 (SARS-CoV-2), influential public health agencies such as the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) have favored the view that SARS CoV-2 spreads predominantly via droplets. Many experts in aerobiology have openly opposed that stance, forcing a vigorous debate on the topic. In this review, we discuss the various proposed modes of viral transmission, stressing the interdependencies between droplet, aerosol, and fomite spread. Relative humidity and temperature prevailing determine the rates at which respiratory aerosols and droplets emitted from an expiratory event (sneezing, coughing, etc .) evaporate to form smaller droplets or aerosols, or experience hygroscopic growth. Gravitational settling of droplets may result in contamination of environmental surfaces (fomites). Depending upon human, animal and mechanical activities in the occupied space indoors, viruses deposited on environmental surfaces may be re-aerosolized (re-suspended) to contribute to aerosols, and can be conveyed on aerial particulate matter such as dust and allergens. The transmission of respiratory viruses may then best be viewed as resulting from dynamic virus spread from infected individuals to susceptible individuals by various physical states of active respiratory emissions, instead of the current paradigm that emphasizes separate dissemination by respiratory droplets, aerosols or by contaminated fomites. To achieve the optimum outcome in terms of risk mitigation and infection prevention and control (IPAC) during seasonal infection peaks, outbreaks, and pandemics, this holistic view emphasizes the importance of dealing with all interdependent transmission modalities, rather than focusing on one modality.

Objective: To evaluate open science policies of imaging journals, and compliance to these policies in published articles. Methods: From imaging journals listed we extracted open science policy details: protocol registration, reporting guidelines, funding, ethics and conflicts of interest (COI), data sharing, and open access publishing. The 10 most recently published studies from each journal were assessed to determine adherence to these policies. We calculated the proportion of open science policies into an Open Science Score (OSS) for all journals and articles. We evaluated relationships between OSS and journal/article level variables. Results: 82 journals/820 articles were included. The OSS of journals and articles was 58.3% and 31.8%, respectively. Of the journals, 65.9% had registration and 78.1% had reporting guideline policies. 79.3% of journals were members of COPE, 81.7% had plagiarism policies, 100% required disclosure of funding, and 97.6% required disclosure of COI and ethics approval. 81.7% had data sharing policies and 15.9% were fully open access. 7.8% of articles had a registered protocol, 8.4% followed a reporting guideline, 77.4% disclosed funding, 88.7% disclosed COI, and 85.6% reported ethics approval. 12.3% of articles shared their data. 51% of articles were available through open access or as a preprint. OSS was higher for journal with DOAJ membership (80% vs 54.2%; P < .0001). Impact factor was not correlated with journal OSS. Knowledge synthesis articles has a higher OSS scores (44.5%) than prospective/retrospective studies (32.6%, 30.0%, P < .0001). Conclusion: Imaging journals endorsed just over half of open science practices considered; however, the application of these practices at the article level was lower.

Distinct from the dynamical phase, in a cyclic evolution, a system’s state may acquire an additional component, a.k.a. geometric phase. Recently, it has been demonstrated that geometric phases can be induced by a sequence of generalized measurements implemented on a single qubit. Furthermore, it has been predicted that these geometric phases may exhibit a topological transition as a function of the measurement strength. We demonstrate and study this transition experimentally by using an optical platform where the qubit is represented by the polarization of light and the weak measurement is performed by means of coupling with the spatial degree of freedom. Our protocol can be interpreted in terms of environment-induced geometric phases, whose values are topologically determined by the environment-system coupling strength. Our results show that the two limits of geometric phase induced by sequences of either weak or projective measurements are topologically distinct.

Background Despite efforts to provide evidence-based care for people living with kidney disease, health care provider goals and priorities are often misaligned with those of individuals with lived experience of disease. Coupled with competing interests of time, resources, and an abundance of suitable guideline topics, identifying and prioritizing areas of focus for the Canadian nephrology community with a patient-oriented perspective is necessary and important. Similar priority-setting exercises have been undertaken to establish research priorities for kidney disease and to standardize outcomes for kidney disease research and clinical care; however, research priorities are distinct from priorities for guideline development. Inclusion of people living with health conditions in the selection and prioritization of guideline topics is suggested by patient engagement frameworks, though the process to operationalizing this is variable. We propose that the Canadian Society of Nephrology Clinical Practice Guideline Committee (CSN CPGC) takes the opportunity at this juncture to incorporate evidence-based prioritization exercises with involvement of people living with kidney disease and their caregivers to inform future guideline activities. In this protocol, we describe our planned research methods to address this. Objective To establish consensus-based guideline topic priorities for the CSN CPGC using a modified Delphi survey with involvement of multidisciplinary stakeholders, including people living with kidney disease and their caregivers. Study design Protocol for a Modified Delphi Survey. Setting Pilot-tested surveys will be distributed via email and conducted using the online platform SurveyMonkey, in both French and English. Participants We will establish a group of multidisciplinary clinical and research stakeholders (both within and outside CSN membership) from Canada, in addition to people living with kidney disease and/or their caregivers. Methods A comprehensive literature search will be conducted to generate an initial list of guideline topics, which will be organized into three main categories: (1) International nephrology-focused guidelines that may require Canadian commentary, (2) Non-nephrology specific guidelines from Canada that may require CSN commentary, and (3) Novel topics for guideline development. Participants will engage in a multi-round Modified Delphi Survey to prioritize a set of “important guideline topics.” Measures Consensus will be reached for an item based on both median score on the Likert-type scale (≥ 7) and the percentage agreement (≥ 75%); the Delphi process will be complete when consensus is reached on each item. Guideline topics will then be given a priority score calculated from the total Likert ratings across participants, adjusted for the number of participants. Limitations Potential limitations include participant response rates and compliance to survey completion. Conclusions We propose to incorporate evidence-based prioritization exercises with the engagement of people living with kidney disease and their caregivers to establish consensus-based guideline topics and inform future guidelines activities of the CSN CPGC.

Background Lumbar stiffness leads to greater hip dependance to achieve sagittal motion and increases instability after total hip arthroplasty (THA). We aimed to determine parameters that influence lumbar stiffness amongst patients with hip pathology. We hypothesized that modifiable (degenerative changes, spinal canal stenosis, facet orientation) and non‐modifiable factors (muscle condition) would be associated with lumbar spine stiffness. Methods In this retrospective case‐cohort study from a tertiary referral center, consecutive patients presenting at a hip specialist clinic underwent standing and deep‐seated radiographic assessment to measure lumbar lordosis (∆LL) (stiffness: ∆LL<20°), hip flexion (∆PFA: pelvic‐femoral angle) and degree of degenerative‐disc‐disease (DDD) (facet osteoarthritis, disc height, endplate proliferative changes). Of these, 65 patients were selected with previous lumbar spine Magnetic Resonance Imaging (MRI), allowing to determine lumbar facet orientation, spinal canal stenosis (Schizas classification) and flexor‐ and extensor‐ muscle atrophy (Goutallier classification). Results Mean ∆LL was 45° (range: 11°‐72°) and 4 patients (6%) exhibited spine stiffness. Patients with multilevel DDD (n=22) had less ∆LL than those with no/single level (n=43) DDD [34° (range: 11°‐53°) vs. 51° (21°‐72°); p<0.001]. Number of DDD levels correlated strongly with ∆LL (rho=‐0.642; p<0.001). Spinal stiffness was only seen in patients with ≥4 DDD‐levels. There was no correlation between ∆LL and facet orientation (p>0.05). ∆LL correlated strongly with extensor atrophy at L3‐L4 (rho=‐0.473), L4‐L5 (rho=‐0.520) and L5‐S1 (rho=‐0.473), and poorly with flexors at L4‐L5 (rho=‐0.134) and L5‐S1 (rho=‐0.227). Conclusion Lumbar stiffness is dependent on modifiable‐ (muscle atrophy) and non‐modifiable‐ (extend of DDD) factors. This can guide non‐operative management of hip pathology, emphasizing relevance of core muscle rehabilitation to improve posture and stiffness. Identification ≥4 DDD‐levels should alert surgeons of increased THA instability‐risk. This article is protected by copyright. All rights reserved.

This paper is an examination of the methodological and theoretical perspectives of a study with an inquiry focus on the experiences and perspectives of staff who worked at an injectable opiate assisted (iOAT) clinic. Twenty-two staff members, including nurses, social workers, and peer support workers, were interviewed. The goal of the study was to uncover how the clinic staff provided care to the clients who attend the clinic, their perspectives on how the clinic program impacted both them and their clients, and their experiences with the program itself. This interpretive descriptive study was underpinned by critical social theory. Thematic analysis was undertaken to identify recurring, converging, and contradictory patterns of interaction, key concepts and emerging themes. In this paper we examine and discuss how the relationship between critical social theory and interpretive description enhanced the study. Examples from the study are presented to provide insight into the relationship.

The objective of this study is to identify the top five most influential papers published on the use of point-of-care ultrasound (POCUS) in cardiac arrest and the top five most influential papers on the use of POCUS in shock in adult patients. An expert panel of 14 members was recruited from the Canadian Association of Emergency Physicians (CAEP) Emergency Ultrasound Committee and the Canadian Ultrasound Fellowship Collaborative. The members of the panel are ultrasound fellowship trained or equivalent, are engaged in POCUS research, and are leaders in POCUS locally and nationally in Canada. A modified Delphi process was used, consisting of three rounds of sequential surveys and discussion to achieve consensus on the top five most influential papers for the use of POCUS in cardiac arrest and shock. The panel identified 39 relevant papers on POCUS in cardiac arrest and 42 relevant papers on POCUS in shock. All panel members participated in all three rounds of the modified Delphi process, and we ultimately identified the top five most influential papers on POCUS in cardiac arrest and also on POCUS in shock. Studies include descriptions and analysis of safe POCUS protocols that add value from a diagnostic and prognostic perspective in both populations during resuscitation. We have developed a reading list of the top five influential papers on the use of POCUS in cardiac arrest and shock to better inform residents, fellows, clinicians, and researchers on integrating and studying POCUS in a more evidence-based manner.

Background Extravasation of iodinated contrast material during computed tomography (CT) is a rare complication. A few patients may develop severe complications such as compartment syndrome. Objective The purpose of this study was to retrospectively assess the prevalence, severity, management, and outcome of contrast extravasations in our institution and to perform a comparison to what has been reported in the existing literature. Materials and methods This is a research ethics board (REB)–approved retrospective study comprising 11 patients who had intravenous contrast-enhanced CT between 2019 and 2022 in a tertiary pediatric center, and experienced extravasation of iodinated contrast as a complication. Age, weight, sex, co-morbidities, angiocatheter size, venous access location, total contrast volume, flow rate, patient’s symptoms, severity of injury, and management were collected. For the systematic review, PRISMA guidelines were followed. Results Only 11 (0.3%) (0.17-0.54 (95%CI)) contrast extravasations occurred in a total of 3638 CTs performed with intravenous contrast during the same period in children. The median age (IQR) was 12.5 (10.0, 15.0) years. In our cohort, 1/11 patients developed compartment syndrome and required fasciotomy. The systematic review assessed 12 articles representing a population of 110 children with extravasations. Pooled prevalence from articles stratified by age was 0.32% (0.06-0.58% (95%CI)). Only three children experienced moderate to severe complications. Conclusions We confirm that severe complications of contrast extravasation are rare and can occur at any age. No strong associations were seen with the need for surgical consultation (including age, sex, weight, flow rate, injection site, catheter size, and type of contrast).

A recent study of the health of Indigenous children in four First Nations Communities in remote northwestern Ontario found that 21% of children had been admitted to hospital for respiratory infections before age 2 years. Here we report a detailed analysis of the housing conditions in these communities. We employed a variety of statistical methods, including linear regression, mixed models, and logistic regression, to assess the correlations between housing conditions and loadings of biocontaminants (dust mite allergens, fungal glucan, and endotoxin) and indoor concentrations of PM 2.5 , CO 2 , benzene, and formaldehyde. The houses (n = 101) were crowded with an average of approximately 7 people. Approximately 27% of the homes had sustained CO 2 concentrations above 1500 ppm. Most homes had more than one smoker. Commercial tobacco smoking and the use of non-electric heating (e.g., wood, oil) were associated with increased fine particle concentrations. Over 90% of the homes lacked working Heat Recovery Ventilators (HRVs), which was associated with increased fine particle concentrations and higher CO 2 . Of the 101 homes, 12 had mold damage sufficient to increase the relative risk of respiratory disease. This resulted from roof leaks, through walls or around the windows due to construction defects or lack of maintenance. A similar percentage had mold resulting from condensation on windows. Endotoxin loadings were much higher than any previous study in Canada. This work provides evidence for the need for more effort to repair existing houses and to ensure the HRVs are properly installed and maintained.