# McMaster University

Recent publications
A technique of continuous shaping current waveform to suppress relaxation oscillations (ROs) of distributed feedback (DFB) laser for a high-performance optic system is demonstrated. To effectively suppress ROs, expressions for the shaping current waveform are theoretically derived based on the rate equations and different polynomials for the 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> , 5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> , and 8 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> order Fourier basis functions are introduced. The convolutional neural network (CNN) is employed to predict the multi-parameter values that determine the results of the shaping input current, which exempt from the difficult and time-consuming process of parameter selection. Prior to training, preprocessing of the data obtained from DFB laser forward simulation using min-max normalization aims to improve the training efficiency of the CNN. The shaping current signals obtained from the CNN predicted parameters are put into the equivalent circuit model for the DFB laser to verify the effectiveness of the shaping current technique and CNN parameter optimization. Afterwards, the shaping current waveform is verified in a time division multiplex passive optical network (TDM-PON) utilizing the DFB laser model as a directly modulated source achieving remarkable performance with low cost. The results show that the high-order continuous shaping current modulated technique can successfully suppress the ROs and enhance the performance of the optic system.
About two-thirds of Canadian COVID-19 related deaths occurred in long-term care homes (LTCHs). Multiple jobholding and excessive part-time work among staff have been discussed as vectors of transmission. Using an administrative census of registered nurses (RNs) and registered practical nurses (RPNs) in the Canadian province of Ontario, this paper contrasts the prevalence of multiple jobholding, part-time/casual work, and other job and worker characteristics across health sectors in 2019 and 2020 to establish whether the LTCH sector deviates from the norms in Ontario healthcare. Prior to COVID-19, about 19% of RNs and 21% of RPNs in LTCHs held multiple jobs. For RPNs, this was almost identical to the RPN provincial average, while for RNs this was 2.5 percentage points above the RN provincial average. In 2020, multiple jobholding fell significantly in LTCHs after the province passed a single site order to reduce COVD-19 transmission. Although there are many similarities across sectors, nurses, especially RNs, in LTCHs differ on some dimensions. They are more likely to be internationally educated and, together with nurses in hospitals, those who work part- time/casual are more likely to prefer full-time hours (involuntary part-time/casual). Overall, while multiple jobholding and part-time work among nurses are problematic for infection prevention and control, these employment practices in LTCHs did not substantially deviate from the norms in the rest of healthcare in Ontario.
Witnessing altruistic behaviour can elicit moral elevation, an emotion that motivates prosocial cooperation. This emotion is evoked more strongly when the observer anticipates that other people will be reciprocally cooperative. Coalitionality should therefore moderate feelings of elevation, as whether the observer shares the coalitional affiliation of those observed should influence the observer's assessment of the likelihood that the latter will cooperate with the observer. We examined this thesis in studies contemporaneous with the 2020 Black Lives Matter (BLM) protests. Although BLM protests were predominantly peaceful, they were depicted by conservative media as destructive and antisocial. In two large-scale, pre-registered online studies (total N = 2172), political orientation strongly moderated feelings of state elevation elicited by a video of a peaceful BLM protest (Studies 1 and 2) or a peaceful Back the Blue (BtB) counter-protest (Study 2). Political conservatism predicted less elevation following the BLM video and more elevation following the BtB video. Elevation elicited by the BLM video correlated with preferences to defund police, whereas elevation elicited by the BtB video correlated with preferences to increase police funding. These findings extend prior work on elevation into the area of prosocial cooperation in the context of coalitional conflict.
Objective/background: Endoscopic balloon dilatation (EBD) has been shown to be effective and safe in adults with stricturing Crohn's disease (CD) yet pediatric data is sparse. We aimed to assess efficacy and safety of EBD in stricturing pediatric CD. Methods: International collaboration included 11 centers from Europe, Canada and Israel. Recorded data included patient demographics, stricture features, clinical outcomes, procedural adverse events and need for surgery. Primary outcome was surgery-free over 12 months, secondary outcomes were clinical response and adverse events. Results: 88 dilatations were performed over 64 dilatation series in 53 patients. Mean age at CD diagnosis 11.1 (±4.0) years, stricture length 4cm (IQR 2.8-5) and bowel wall thickness 7mm (IQR 5.3-8). 12/64 (19%) patients underwent surgery in the year following the dilatation series, at a median of 89 days (IQR 24-120; range 0-264) following EBD. 7/64 (11%) had subsequent unplanned EBD over the year, of whom two eventually underwent surgical resection. 2/88 (2%) perforations were recorded, one of whom was managed surgically, and 5 patients had minor adverse events managed conservatively.There was a significant improvement in all clinical measures following EBD with wPCDAI-defined remission increasing from 13% at baseline to 44%, 46% and 61%, and absence of obstructive symptoms in 55%, 53% and 64% of patients at week 2, 8 and 24 respectively. Conclusions: In this largest study of EBD in pediatric stricturing CD to date, we demonstrated that EBD is effective in relieving symptoms and avoiding surgery. Adverse events rates were low and consistent with adult data.
Introduction: Health professions training programs increasingly rely on standardized patient (SP) programs to integrate equity-deserving groups into learning and assessment opportunities. However, little is known about the optimal approach, and many SP programs struggle to meet these growing needs. This study explored insights from healthcare educators working with SP programs to deliver curricular content around equity-deserving groups. Methods: We interviewed 14 key informants in 2021 who were involved in creating or managing SP-based education. Verbatim transcripts were analyzed in an iterative coding process, anchored by qualitative content analysis methodology, and informed by two theoretical frameworks: sociologic translation and simulation design. Repeated cycles of data collection and analyses continued until themes could be constructed, aligned with existing theories, and grounded in empirical data, with sufficient relevance and robustness to inform educators and curricular leads. Results: Three themes were constructed: (1) creating safety for SPs paid to be vulnerable, (2) fidelity as an issue broader than who plays the role, and (3) engaging equity deserving groups. SP work involving traditionally marginalized groups risks re-traumatization, highlighting the importance of (1) informed consent in recruiting SPs, (2) separating role portrayal from lived experiences, (3) adequately preparing learners and facilitators, (4) creating time-outs and escapes for SPs, and (5) building opportunity for de-roling with community support. Discussion: SP programs are well positioned to be allies and advocates to equity-deserving groups and to collaborate and share governance of the educational development process from its outset. SP programs can support the delivery of curricular content around equity-deserving groups by advocating with curricular leadership, building relationships with community partners, facilitating co-creation and co-delivery of educational content, and building safety into simulation.
Continuous monitoring of human vital signs using non-contact mmWave radars is attractive due to their ability to penetrate garments and operate under different lighting conditions. Unfortunately, most prior research requires subjects to stay at a fixed distance from radar sensors and to remain still during monitoring. These restrictions limit the applications of radar vital sign monitoring in real life scenarios. In this paper, we address these limitations and present Pi-ViMo, a non-contact P hysiology- i nspired Robust Vi tal Sign Mo nitoring system, using mmWave radars. We first derive a multi-scattering point model for the human body, and introduce a coherent combining of multiple scatterings to enhance the quality of estimated chest-wall movements. It enables vital sign estimations of subjects at any location in a radar’s field of view (FoV). We then propose a template matching method to extract human vital signs by adopting physical models of respiration and cardiac activities. The proposed method is capable to separate respiration and heartbeat in the presence of micro-level random body movements (RBM) when a subject is at any location within the field of view of a radar. Experiments in a radar testbed show average respiration rate errors of $$6\%$$ and heart rate errors of $$11.9\%$$ for the stationary subjects, and average errors of $$13.5\%$$ for respiration rate and $$13.6\%$$ for heart rate for subjects under different RBMs.
An intriguing chiral soliton phase has recently been identified in the S=12 Kitaev spin chain. Here we show that for S = 1, 2, 3, 4, 5 an analogous phase can be identified, but contrary to the S=12 case the chiral soliton phases appear as islands within the sea of the polarized phase. In fact, a small field applied in a general direction will adiabatically connect the integer spin Kitaev chain to the polarized phase. Only at sizable intermediate fields along symmetry directions does the soliton phase appear centered around the special point hx★=hy★=S where two exact product ground states can be identified. The large-S limit can be understood from a semiclassical analysis, and variational calculations provide a detailed picture of the S=1 soliton phase. Under open boundary conditions, the chain has a single soliton in the ground state, which can be excited, leading to a proliferation of in-gap states. In contrast, even length periodic chains exhibit a gap above a twice-degenerate ground state. The presence of solitons leaves a distinct imprint on the low-temperature specific heat.
Over the past decade, there has been a new “decolonial turn,” albeit less related than before to land and political independence. “To decolonize” is now associated with something less tangible and often under-defined. We argue that scholars, especially Western ones, should avoid depoliticizing the expression “decolonizing” by using it as a buzzword. Scholars and policymakers should use the expression only if it is closely related to the political meaning ascribed to it by Global South and Indigenous activists and scholars. Decoloniality is a political project of human emancipation through collective struggles, entailing at least the following: 1) abolishing racial hierarchies within the hetero-patriarchal and capitalist world order, 2) dismantling the geopolitics of knowledge production, and 3) rehumanizing our relationships with Others and nature. We conclude that there is a need for epistemic humility and that Western scholars and institutions must refrain from using the word too freely.
Purpose: To evaluate a knowledge translation intervention to determine knowledge, attitudes and self-efficacy related to HIV and rehabilitation advocacy in physiotherapy students. Methods: A pre and post-test study was conducted at three physiotherapy-training programs in Sub Saharan Africa - the University of the Witwatersrand (Wits), the University of Zambia (UNZA) and Kenya Medical Technical College (KMTC). For each site, the knowledge, attitude and self-efficacy of physiotherapy students were tested pre- and post-intervention using a standardized questionnaire. Results: Students' knowledge improved with regard to being able to describe the challenges faced by their patients, knowing what resources are available and understanding their role as an advocate. In terms of self-efficacy, they felt more confident clinically, as well as being a resource person to colleagues and an advocate for their patients. Unlabelled: This study highlights the need to contextualize knowledge translation interventions to meet the unique needs of individual academic sites. Students who have clinical experience working with people living with HIV are more likely to embrace their role as advocates in the area of HIV and rehabilitation.Implications for RehabilitationThe knowledge translation process used in this study gives a concrete example of how to use research evidence on HIV knowledge in rehabilitation applied within the advocacy process.Applying the principles of advocacy translates to understanding the management of HIV practically.Clinical experience in managing people living with HIV strengthens knowledge and improves the attitude of physiotherapy studentsPhysiotherapy students need guidance in realizing their potential as advocates for holistic rehabilitation care for people living with HIV.
Background There is a lack of studies focusing on the benefit of liver transplantation (LT) in hepatocellular carcinoma (HCC) patients with > 3 tumors. This study aims to establish a model to effectively predict overall survival in Chinese HCC patients with multiple tumors (> 3 tumors) who undergo LT. Methods This retrospective study included 434 HCC liver transplant recipients from the China Liver Transplant Registry. All HCC patients had more than 3 tumor nodules. Three selection criteria systems (i.e., AFP, Metroticket 2.0, and Up-to-7) were compared regarding the prediction of HCC recurrence. The modified AFP model was established by univariate and multivariate competing risk analyses. Results The AFP score 2 and the AFP score ≥ 3 groups had 5-year recurrence rates of 19.6% and 40.5% in our cohort. The prediction of HCC recurrence based on the AFP model was associated with a c-statistic of 0.606, which was superior to the Up-to-7 and Metroticket 2.0 models. AFP level > 1000 ng/mL, largest tumor size ≥ 8 cm, vascular invasion, and MELD score ≥ 15 were associated with overall survival. The 5-year survival rate in the modified AFP score 0 group was 71.7%. Conclusions The AFP model is superior in predicting tumor recurrence in HCC patients with > 3 tumors prior to LT. With the modified AFP model, patients likely to derive sufficient benefit from LT can be identified.
Objectives The primary aim was to describe the characteristics and prevalence of musculoskeletal complaints of a large group of non-professional golfers. Secondary aims were to compare golfers different in (A) skill-level, (B) presence of low back pain (LBP) and (C) performance of prevention exercises. Methods A sample of 1170 male golfers (mean age 54.98, SD=13.3) were surveyed online on personal and golf-specific characteristics, medical history and complaints in the preceding 7 days. Subgroups (A) with different golfing handicap (0 to 5, >5 to 10, >10), (B) with and without LBP and (C) who performed versus did not perform injury prevention exercises were compared using analysis of variance and χ ² test. Results The prevalence and severity of musculoskeletal complaints was similar in everyday life and when playing golf. More than one-third of the golfers (n=436; 37.3%) reported LBP in the preceding 7 days, while other frequently affected body parts were the shoulder and knee. Golfers with different skill level differed in age and most golf-related characteristics but not in prevalence and severity of musculoskeletal complaints. Golfers with and without LBP were similar in almost all variables. Golfers who performed prevention exercises (n=371; 27.1%) were older and had a higher prevalence of complaints. Conclusion The prevalence and severity of musculoskeletal complaints in golfers were similar to the wider population. It seems that injury prevention exercises were implemented after injury, rather than as primary prevention. Prospective studies looking at the epidemiology of injury, risk factors and interventions are required.
We introduce a deep learning model that can universally approximate regular conditional distributions (RCDs). The proposed model operates in three phases: first, it linearizes inputs from a given metric space X\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {X}$$\end{document} to Rd\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathbb {R}^d$$\end{document} via a feature map, then a deep feedforward neural network processes these linearized features, and then the network’s outputs are then transformed to the 1-Wasserstein space P1(RD)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {P}_1(\mathbb {R}^D)$$\end{document} via a probabilistic extension of the attention mechanism of Bahdanau et al. (Neural machine translation by jointly learning to align and translate, 2014. arXiv:1409.0473). Our model, called the probabilistic transformer (PT), can approximate any continuous function from Rd\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathbb {R}^d$$\end{document} to P1(RD)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {P}_1(\mathbb {R}^D)$$\end{document} uniformly on compact sets, quantitatively. We identify two ways in which the PT avoids the curse of dimensionality when approximating P1(RD)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {P}_1(\mathbb {R}^D)$$\end{document}-valued functions. The first strategy builds functions in C(Rd,P1(RD))\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C(\mathbb {R}^d,\mathcal {P}_1(\mathbb {R}^D))$$\end{document} which can be efficiently approximated by a PT, uniformly on any given compact subset of Rd\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathbb {R}^d$$\end{document}. In the second approach, given any function f in C(Rd,P1(RD))\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C(\mathbb {R}^d,\mathcal {P}_1(\mathbb {R}^D))$$\end{document}, we build compact subsets of Rd\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathbb {R}^d$$\end{document} whereon f can be efficiently approximated by a PT.
Microglia are immune brain cells implicated in stress-related mental illnesses including posttraumatic stress disorder (PTSD). Their role in the pathophysiology of PTSD, and on neurobiological systems that regulate stress, is not completely understood. We tested the hypothesis that microglia activation, in fronto-limbic brain regions involved in PTSD, would be elevated in participants with occupation-related PTSD. We also explored the relationship between cortisol and microglia activation. Twenty participants with PTSD and 23 healthy controls (HC) completed positron emission tomography (PET) scanning of the 18-kDa translocator protein (TSPO), a putative biomarker of microglia activation using the probe [¹⁸F]FEPPA, and blood samples for measurement of cortisol. [¹⁸F]FEPPA VT was non-significantly elevated (6.5–30%) in fronto-limbic regions in PTSD participants. [¹⁸F]FEPPA VT was significantly higher in PTSD participants reporting frequent cannabis use compared to PTSD non-users (44%, p = 0.047). Male participants with PTSD (21%, p = 0.094) and a history of early childhood trauma (33%, p = 0.116) had non-significantly higher [¹⁸F]FEPPA VT. Average fronto-limbic [¹⁸F]FEPPA VT was positively related to cortisol (r = 0.530, p = 0.028) in the PTSD group only. Although we did not find a significant abnormality in TSPO binding in PTSD, findings suggest microglial activation might have occurred in a subgroup who reported frequent cannabis use. The relationship between cortisol and TSPO binding suggests a potential link between hypothalamic–pituitary–adrenal-axis dysregulation and central immune response to trauma which warrants further study.
Objectives: We conducted a systematic review and meta-analysis of randomized controlled trials comparing direct oral anticoagulants (DOACs) to vitamin K antagonists (VKAs) in the first 90 days after bioprosthetic valve implantation. Methods: We systematically searched EMBASE, MEDLINE, and CENTRAL. We screened titles, abstracts, and full texts, extracted data, and assessed risk of bias in duplicate. We pooled data using the Mantel-Haenzel method and random effects modelling. We conducted subgroup analyses based on type of valve (transcatheter versus surgical) and timing of initiation of anticoagulation (<7 days versus >7 days after valve implantation). We assessed the certainty of evidence using the Grading of Recommendations, Assessments, Development and Evaluation (GRADE) approach. Results: We included 4 studies of 2284 patients with a median follow-up of 12 months. Two studies examined transcatheter valves (1877/2284 = 83%) and two examined surgical valves (407/2284 = 17%). We found no statistically significant differences between DOACs and VKAs with regard to thrombosis, bleeding, death, or subclinical valve thrombosis. However, there was a subgroup trend towards more bleeding with DOACs when initiated within 7 days of valve implantation. Conclusions: In the existing randomized literature on DOACs versus VKAs in the first 90 days after bioprosthetic valve implantation, there appears to be no difference with regard to thrombosis, bleeding, or death. Interpretation of the data is limited by small numbers of events and wide confidence intervals. Future studies should focus on surgical valves and should include long-term follow-up to assess any potential impact of randomized therapy on valve durability.
Purpose: Health Teams Advancing Patient Experience: Strengthening Quality (Health TAPESTRY) is a complex primary care program aimed at assisting older adults to stay healthier for longer. This study evaluated the feasibility of implementation across multiple sites, and the reproducibility of the effects found in the previous randomized controlled trial. Methods: This was a pragmatic, unblinded, 6-month parallel group randomized controlled trial. Participants were randomized (intervention or control) using a computer-generated system. Eligible patients, aged 70 years and older, were rostered to 1 of 6 participating interprofessional primary care practices (urban and rural). In total, 599 (301 intervention, 298 control) patients were recruited from March 2018 through August 2019. Intervention participants received a home visit from volunteers to collect information on physical and mental health, and social context. An interprofessional care team created and implemented a plan of care. The primary outcomes were physical activity and number of hospitalizations. Results: Based on the Reach, Effectiveness, Adoption, Implementation, Maintenance (RE-AIM) framework, Health TAPESTRY had widespread reach and adoption. In the intention-to-treat analysis (257 intervention, 255 control), there were no statistically significant between-group differences for hospitalizations (incidence rate ratio = 0.79; 95% CI, 0.48-1.30; P = .35) or total physical activity (mean difference = -0.26; 95% CI, -1.18 to 0.67; P = .58). There were 37 non-study related serious adverse events (19 intervention, 18 control). Conclusions: We found Health TAPESTRY was successfully implemented for patients in diverse primary care practices; however, implementation did not reproduce the effect on hospitalizations and physical activity found in the initial randomized controlled trial.
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• Departments of Anethesia and Clinical Epidemiology & Biostatistics
• Department of Mathematics and Statistics
• Department of Electrical and Computer Engineering
• Health Research Methods Evidence and Impact
• Department of Medicine
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