McMaster University
  • Hamilton, Canada
Recent publications
Enhanced insulation and superior thermal characteristics are crucial in advanced packaging for medium voltage (MV) silicon carbide (SiC) power modules. Nonetheless, the reduction in thermal resistance typically compromises insulation level due to the decreased number of insulation layers. In this paper, the forced fluorinated liquid cooling methodology is proposed, whereby fluorinated liquid (3M FC-40) is directed into the power module, substituting silicone gel and diminishing thermal resistance. Through the utilization of forced fluorinated liquid cooling, a reduction of 21°C in junction temperature at full load is demonstrated in the experiment, compared to traditional power modules cooled with water. Furthermore, there is a 35.6% reduction observed in the maximum temperature rise ΔTj, thereby enhancing the lifespan of the power module. Enhanced cooling efficiency with lower flow rates of forced fluorinated liquid cooling offers greater energy savings than water cooling. As dissipation power is transferred from the topside of the chip to the fluorinated liquid, the possibility of unlimited stacking of direct bonded copper (DBC) is enabled to lower the electrical field, thereby facilitating insulation at the bottom side of the chip without any worries regarding heightened thermal resistance. Forced fluorinated liquid cooling resulted in a 39°C reduction in the junction temperature of the double-stacked DBC power module. Moreover, partial discharge (PD) detection under square wave excitation revealed that the DBC immersed in the fluorinated liquid remains free from PD at 10 kV, a significantly higher threshold than observed with silicone gel. A higher partial discharge inception voltage (PDIV) is anticipated for double-stacked DBC when immersed in 3M FC-40. Thus, the forced fluorinated liquid cooling, which simultaneously enhances thermal and insulation performance, can be considered a promising solution for the next generation of MV SiC power modules.
The development of current sensors for wide-bandgap (WBG) applications consistently emphasizes high bandwidth, minimal invasiveness, and integration. Despite the meticulous design that enables current shunts to achieve excellent performance with high bandwidth and low parasitics, their inherent bulkiness remains a significant challenge for their integration into high-integrated applications that depend on the high switching speeds of WBG power devices. This study thoroughly investigates and uncovers the trade-off faced by traditional current shunts in balancing miniaturization and high bandwidth. Building upon this understanding, the miniaturized current shunt (MiniShunt) concept is introduced to overcome inherent limitations and achieve both high performance and compact size. To realize this concept, a physical implementation that involves the high-density stacking of multiple coupled transmission lines is presented. Additionally, a thermal network model specifically for the proposed MiniShunt configuration is developed and a comprehensive thermal analysis methodology for the current shunts is established. By applying this methodology to finite element analysis (FEA), the thermal safe operating area (SOA) for the MiniShunt can be determined, further providing valuable insights into its maximum static power dissipation and maximum energy loss. These findings contribute to the development of a highly compact 9×9-mm, 100-mΩ current shunt with an ultrahigh bandwidth of 3 GHz, near-zero parasitic inductance, and a maximum energy loss of 2.0 J at a reference temperature rise limit of 20°C. Extensive experiments conducted in both the frequency and time domains serve to further validate the advantages of the MiniShunt in terms of its miniaturization, integration, ultrafast response, and low invasiveness for future high-integrated power electronics applications.
An on‐going challenge with COVID‐19, which has huge implications for future pandemics, is the rapid emergence of viral variants that makes diagnostic tools less accurate, calling for rapid identification of recognition elements for detecting new variants caused by mutations. We hypothesize that we can fight mutations of the viruses with mutations of existing recognition elements. We demonstrate this concept via rapidly evolving an existing DNA aptamer originally selected for the spike protein (S‐protein) of wildtype SARS‐CoV‐2 to enhance the interaction with the same protein of the Omicron variants. The new aptamer, MBA5SA1, has acquired 22 mutations within its 40‐nucleotide core sequence and improved its binding affinity for the S‐proteins of diverse Omicron subvariants by >100‐fold compared to its parental aptamer (improved from nanomolar to picomolar affinity). Deep sequencing analysis reveals dynamic competitions among several MBA5SA1 variants in response to increasing selection pressure imposed during in vitro selection, with MBA5SA1 being the final winner of the competition. Additionally, MBA5SA1 was implemented into an enzyme‐linked aptamer binding assay (ELABA), which was applied for detecting Omicron variants in the saliva of infected patients. The assay produced a sensitivity of 86.5 % and a specificity of 100 %, which were established with 83 clinical samples.
Emerging memory technologies, such as DDR5, offer increased data rates and storage capacities, at the expense of signal integrity challenges. To address these challenges, the DDR5 standard incorporates a four-tap decision feedback equalizer (DFE). As elaborated in this article, known methods for DFE tuning are limited due to interface complexity and distinct equalization requirements for DDR5. We propose a decision-directed DFE tuning method called thresholding decision-directed descent (T3D). By leveraging DDR5 architectural features, our novel method tracks the eye envelope as it opens, which facilitates rapid convergence compared to the state of the art. To validate the performance of T3D, silicon measurements are presented alongside a virtual testbench methodology. By demonstrating the high correlation between silicon and simulation results, the virtual testbench can be beneficial for the design, validation, and prototyping of future DFE tuning methods.
This paper studies the problem of encoding messages into sequences which can be uniquely recovered from some noisy observations about their substrings. The observed reads comprise consecutive substrings with some given minimum overlap. This coded reconstruction problem has applications in DNA storage. We consider both single-strand reconstruction codes and multi-strand reconstruction codes, where the message is encoded into a single strand or a set of multiple strands, respectively. Various parameter regimes are studied. New codes are constructed, some of whose rates asymptotically attain the upper bounds.
We consider the rate-limited quantum-to-classical optimal transport in terms of output-constrained rate-distortion coding for both finite-dimensional and continuous-variable quantum-to-classical systems with limited classical common randomness. The main coding theorem provides a single-letter characterization of the achievable rate region of a lossy quantum measurement source coding for an exact construction of the destination distribution (or the equivalent quantum state) while maintaining a threshold of distortion from the source state according to a generally defined distortion observable. The constraint on the output space fixes the output distribution to an IID predefined probability mass function. Therefore, this problem can also be viewed as information-constrained optimal transport which finds the optimal cost of transporting the source quantum state to the destination classical distribution via a quantum measurement with limited communication rate and common randomness. We develop a coding framework for continuous-variable quantum systems by employing a clipping projection and a dequantization block and using our finite-dimensional coding theorem. Moreover, for the Gaussian quantum systems, we derive an analytical solution for rate-limited Wasserstein distance of order 2, along with a Gaussian optimality theorem, showing that Gaussian measurement optimizes the rate in a system with Gaussian quantum source and Gaussian destination distribution. The results further show that in contrast to the classical Wasserstein distance of Gaussian distributions, which corresponds to an infinite transmission rate, in the Quantum Gaussian measurement system, the optimal transport is achieved with a finite transmission rate due to the inherent noise of the quantum measurement imposed by Heisenberg’s uncertainty principle.
Introduction Skeletal muscle satellite cells (SC) contribute to the adaptive process of resistance exercise training (RET) and may be influenced by nutritional supplementation. However, little research exists on the impact of multi-ingredient supplementation on the SC response to RET. Purpose We tested the effect of a multi-ingredient supplement (MIS) including whey protein, creatine, leucine, calcium citrate, and vitamin D on SC content and activity as well as myonuclear accretion, SC and myonuclear domain compared with a collagen control (COL) throughout a 10-wk RET program. Methods Twenty-six participants underwent a 10-wk linear RET program while consuming either the MIS or COL supplement twice daily. Muscle biopsies were taken from the vastus lateralis at baseline and 48 h after a bout of damaging exercise, before and after RET. Muscle tissue was analyzed for SC and myonuclear content, domain, acute SC activation, and fiber cross-sectional area (fCSA). Results MIS resulted in a greater increase in type II fCSA following 10 wk of RET (effect size (ES) = 0.89) but not myonuclear accretion or SC content. Change in myonuclei per fiber was positively correlated with type I and II and total fiber hypertrophy in the COL group only, indicating a robust independent effect of MIS on fCSA. Myonuclear domain increased similarly in both groups, whereas SC domain remained unchanged following RET. SC activation was similar between groups for all fiber types in the untrained state but showed a trend toward greater increases with MIS after RET (ES = 0.70). Conclusions SC responses to acute damaging exercise and long-term RET are predominantly similar in MIS and COL groups. However, MIS can induce greater increases in type II fCSA with RET and potentially SC activation following damage in the trained state.
Evidence has ostensibly been accumulating over the past 2 decades suggesting that an external focus on the intended movement effect (e.g., on the golf club during a swing) is superior to an internal focus on body movements (e.g., on your arms during a swing) for skill acquisition. Seven previous meta-studies have all reported evidence of external focus superiority. The most comprehensive of these concluded that an external focus enhances motor skill retention, transfer, and performance and leads to reduced eletromyographic activity during performance and that more distal external foci are superior to proximal external foci for performance. Here, we reanalyzed these data using robust Bayesian meta-analyses that included several plausible models of publication bias. We found moderate to strong evidence of publication bias for all analyses. After correcting for publication bias, estimated mean effects were negligible: g = 0.01 (performance), g = 0.15 (retention), g = 0.09 (transfer), g = 0.06 (electromyography), and g = −0.01 (distance effect). Bayes factors indicated data favored the null for each analysis, ranging from BF01 = 1.3 (retention) to 5.75 (performance). We found clear evidence of heterogeneity in each analysis, suggesting the impact of attentional focus depends on yet unknown contextual factors. Our results contradict the existing consensus that an external focus is always more effective than an internal focus. Instead, focus of attention appears to have a variety of effects that we cannot account for, and, on average, those effects are small to nil. These results parallel previous metascience suggesting publication bias has obfuscated the motor learning literature.
Meningeal innate lymphoid cells guide inhibitory neurons in early life
Background Involving stroke patients in clinical research through patient engagement aims to ensure that studies are patient-centered, and may help ensure they are feasible, ethical, and credible, ultimately leading to enhanced trust and communication between researchers and the patient community. In this study, we have conducted a scoping review to identify existing evidence and gaps in SPSE. Methods The five-step approach outlined by Arksey and O’Malley, in conjunction with the Preferred Reporting Items for Scoping Reviews (PRISMA-ScR) guidelines, provided the structure for this review. To find relevant articles, we searched PubMed, Web of Science, and Embase databases up to February 2024. Additionally, the review team conducted a hand search using Google Scholar, key journals, and references of highly relevant articles. Reviewers screened articles, selecting eligible English-language ones with available full texts, and extracted data from them into a pre-designed table tested by the research team. Result Of the 1002 articles initially identified, 21 proved eligible. Stakeholder engagement primarily occurred during the design phase of studies and within the studies using qualitative methodologies. Although the engagement of stakeholders in the research process is increasing, practice regarding terminology and principles of implementation remains variable. Researchers have recognized the benefits of stakeholder engagement, but have also faced numerous challenges that often arise during the research process. Conclusion The current study identifies stakeholder groups and the benefits and challenges researchers face in implementing their engagement. Given existing challenges and limited specific models or frameworks, it is suggested to explore applied recommendations for stakeholder engagement in future studies, that may enhance stakeholder engagement, overcome obstacles, and unify researchers’ understanding of engagement and implementation.
Climate change exerts wide-ranging and significant effects on global mental health via multifactorial pathways, including food insecurity. Indigenous Peoples and pregnant women inequitably experience the harms associated with climate change and food insecurity. This study explores food security and maternal mental health during pregnancy among rural Ugandan Bakiga and Indigenous Batwa women in the context of climate change. Using a community-based research approach, we conducted a series of focus group discussions about climate, food security, and health during pregnancy in four Indigenous Batwa communities and four Bakiga communities in rural Kanungu District, Uganda, as well as longitudinal follow up interviews later in the year. Data were evaluated using a qualitative thematic analysis. Women consistently identified mental health as an important factor affecting maternal-fetal wellbeing during pregnancy. Many women identified that weather and climate extremes, such as prolonged droughts and unpredictable weather events, have made it more difficult for them to obtain sufficient food for themselves and their families during pregnancy, resulting in significant mental distress. More extreme weather conditions have made physical labour difficult or impossible during pregnancy, and resultant hunger further decreased ability to obtain food—a vicious cycle. Women described how anxiety was compounded by worry about future famine, as they anticipated further decreases in crop yields and rising food prices in a changing climate. Indigenous Batwa women experienced additional distress around their lack of access to Indigenous lands and its nutritious food sources. Overall, mothers in rural Uganda described food insecurity and climate extremes as major sources of stress during pregnancy, and they anticipate challenges will worsen. Interventions to enhance adaptive capacity to climate change are needed and should have a focus on the intricate connections with food insecurity and mental health as drivers of overall maternal health.
Objectives Long-term exposure to air pollution has been associated with higher risk of cardiovascular mortality. Less is known about the association of air pollution with initial development of cardiovascular disease. Herein, the association between low-level exposure to air pollutants and subclinical carotid atherosclerosis in adults without known clinical cardiovascular disease was investigated. Design Cross-sectional analysis within a prospective cohort study. Setting The Canadian Alliance for Healthy Hearts and Minds Cohort Study; a pan-Canadian cohort of cohorts. Participants Canadian adults (n = 6645) recruited between 2014–2018 from the provinces of British Columbia, Alberta, Ontario, Quebec, and Nova Scotia, were studied, for whom averages of exposures to nitrogen dioxide (NO2), ozone (O3), and fine particulate matter (PM2.5) were estimated for the years 2008–2012. Main outcome measure Carotid vessel wall volume (CWV) measured by magnetic resonance imaging (MRI). Results In adjusted linear mixed models, PM2.5 was not consistently associated with CWV (per 5 μg/m³ PM2.5; adjusted estimate = -8.4 mm³; 95% Confidence Intervals (CI) -23.3 to 6.48; p = 0.27). A 5 ppb higher NO2 concentration was associated with 11.8 mm³ lower CWV (95% CI -16.2 to -7.31; p<0.0001). A 3 ppb increase in O3 was associated with 9.34 mm³ higher CWV (95% CI 4.75 to 13.92; p<0.0001). However, the coarse/insufficient O3 resolution (10 km) is a limitation. Conclusions In a cohort of healthy Canadian adults there was no consistent association between PM2.5 or NO2 and increased CWV as a measure of subclinical atherosclerosis by MRI. The reasons for these inconsistent associations warrant further study.
Background Biosampling studies in critically ill patients traditionally involve bedside collection of samples followed by local processing (ie. centrifugation, aliquotting, and freezing) and storage. However, community hospitals, which care for the majority of Canadian patients, often lack the infrastructure for local processing and storage of specimens. A potential solution is a “simplified” biosampling protocol whereby blood samples are collected at the bedside and then shipped to a central site for processing and storage. One potential limitation of this approach is that delayed processing may alter sample characteristics. Objective To determine whether delays in blood sample processing affect the stability of cytokines (IL-6, TNF, IL-10, IFN-γ), chemokines (IL-8, IP-10, MCP-1, MCP-4, MIP-1α, MIP-1β), cell-free DNA (cfDNA) (released by dying cells), and blood clotting potential in human blood samples. Methods Venous blood was collected into EDTA and citrate sample tubes and stored at room temperature (RT) or 4°C for progressive intervals up to 72 hours, prior to processing. Plasma cytokines and chemokines were quantified using single or multiplex immunoassays. cfDNA was measured using Picogreen DNA Quantification. Blood clotting potential was measured using a thrombin generation assay. Results Blood samples were collected from 9 intensive care unit (ICU) patients and 7 healthy volunteers. Admission diagnoses for the ICU patients included sepsis, trauma, ruptured abdominal aortic aneurysm, intracranial hemorrhage, gastrointestinal bleed, and hyperkalemia. After pre-processing delays of up to 72 hours at RT or 4°C, no significant changes were observed in plasma cytokines, chemokines, cfDNA, or thrombin formation. Conclusions Delayed sample processing for up to 72 hours at either RT or 4°C did not significantly affect cytokines, chemokines, cfDNA, or blood clotting potential in plasma samples from healthy volunteers and ICU patients. A “simplified” biosampling protocol is a feasible solution for conducting biosampling research at hospitals without local processing capacity.
Background Geriatric Emergency Department (ED) Guidelines recommend optimizing transitions of care for older patients with complex needs. In this study, we investigated referral patterns to interprofessional services, including occupational therapy, physiotherapy, dietician, social work, home care, and specialized geriatric services, among older adults presenting to the ED with high‐risk characteristics. Methods We recruited community‐dwelling older adults presenting to 10 EDs across Ontario, Quebec, and Newfoundland, Canada, from April 2017 to July 2018. To observe processes of care in the ED, we deployed a two‐stage high‐risk case‐finding and focused comprehensive assessment process based on the interRAI ED‐Screener and ED Contact Assessment to identify and characterize older adults at high risk. We analyzed the secondary data using descriptive statistics and logistic regression. Results We screened 5265 individuals with the ED Screener, further assessed 1479 with the ED Contact Assessment, and analyzed data from a subset of 1055 community‐dwelling older adults assessed with the ED Contact Assessment. Participants in our study sample had a mean age of 83 years, 58% were female, and many had a complex burden of cognitive and functional impairment and social needs. Over half of this high‐needs sample were referred to general home care services (62.7%), occupational therapy (59.3%), and physiotherapy services (55.2%), while 16% were referred to specialized geriatric services. We also found a significant positive association between interprofessional referrals and the Assessment Urgency Algorithm and Institutional Risk Scale. The most important determinants of referral to interprofessional services were hospital province, functional, clinical, and social burden and support measures. Conclusions The referral patterns identified suggest that patient needs and risk intensity did not always guide referral patterns in the Canadian EDs investigated. We suggest that EDs critically examine the appropriateness of their documentation and referral systems for supporting person‐centered care provision.
Giant cell arteritis can present with atypical manifestations that delay treatment and risk severe complications. To comprehensively describe all atypical signs/symptoms of giant cell arteritis. In this systematic review, we searched MEDLINE, Embase, and Cochrane Central Register of Controlled Trials from inception to October 2022. Primary research articles that included at least one participant with an atypical sign/symptom of biopsy-proven giant cell arteritis were included. Study screening and data extraction were performed in duplicate. The primary outcome was the proportion of participants with atypical giant cell arteritis features. Time to treatment was compared between participants with atypical giant features only and participants with both typical and atypical features. Of 21,828 screened records, 429 studies corresponding to 746 individuals (median [IQR] age 72 [IQR, 66–78] years, 63% female) with at least one atypical feature of GCA were included. Eighty-two percent had both atypical and at least one concurrent typical giant cell arteritis feature, whereas 18% of patients with atypical signs and symptoms only presented with atypical features. Patients with atypical symptoms presented to clinicians earlier than patients with typical features (p < 0.001). There was no difference between groups in proportion to elevated ESR and CRP (82.3% vs. 83.35%, p = 0.91) or mortality rate (8.2% vs. 10.8%, p = 0.42). Patients with atypical features only experienced greater delay in treatment initiation (p < 0.001). The most commonly reported atypical signs/symptoms were vertigo (11.9%), scalp necrosis/ulceration (7.9%), and dry cough (5.8%). Eighteen percent of biopsy-proven giant cell arteritis cases with at least one atypical feature have only atypical features and are more likely to experience delays in treatment. Clinicians should be aware of atypical signs/symptoms of giant cell arteritis and order inflammatory markers early to prevent giant cell arteritis–associated morbidity.
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
20,401 members
Behnam Sadeghirad
  • Departments of Anethesia and Clinical Epidemiology & Biostatistics
Shannon Lane
  • School of Rehabilitation Science
Matiar Howlader
  • Department of Electrical and Computer Engineering
Carlos Alberto Cuello-Garcia
  • Health Research Methods Evidence and Impact
Loubna Akhabir
  • Department of Medicine
Information
Address
Hamilton, Canada