4 research outputs found
GPU Based Monte Carlo Estimation of Eddy Current Losses in Electromagnetic Coil-Core System
No full textA novel parallelizable probabilistic approach to model eddy currents in AC electromagnets is presented in this research. Consequently, power loss associated with the formation of these eddy currents is estimated and validated using experimental data. Furthermore, predicting the effect of ferromagnetic alternating field enhancement on power loss in the source excitation winding has been an active area of research. Unlike a stationary field, an alternating sinusoidal field diffuses partially into the ferromagnetic material leading to a predictably sub-optimal field enhancement. To model these physics, finite element techniques employ nonlinear iterative solvers which are time consuming. A novel method is developed in this research by packing the ferromagnetic domain with variable sized hard spheres. The interaction of these spherical sub-domains with the inducing background field results in a field enhancement that is theoretically identical to enhancement created by the solid ferromagnetic continuum. The evaluated losses in the winding with and without the ferromagnetic material are further employed to evaluate thermal distributions throughout the system. A holistic multiphysics tool has been realized as part of this research which could be employed to estimate field uniformity and engineer active cooling as part of the development and testing of an electromagnetic coil-core system.
Given the current trend in parallel computing, the probabilistic technique developed by the author has been implemented on General Purpose Graphical Processing Units consisting of 2688 processing cores, each of which handles solution of governing equations at an isolated location in the domain independent of one another. By employing the proposed method, a speed gain of 35% over conventional commercial finite element software is guaranteed for simulating commonly employed coil-core electromagnetic systems. In addition to this primary advantage, the resource intensive ( 20 GB RAM memory) matrix inversion techniques employed by these commercial finite element softwares are bypassed. Since probabilistic techniques intrinsically do not require extensive data storage, on-chip GPU memory of 8GB has been realized to be more than adequate for practical winding simulations.
Experimental validation of the probabilistic model is carried out by employing the Lock-in Amplifier loss determination procedure. The phase shift in voltage with respect to current could be precisely determined by the procedure which is key to evaluating winding losses. To isolate losses in the excitation winding due to ferromagnetic field enhancement, an existing inductive voltage cancellation technique using a compensation winding system has been adapted by the author. A sensitive J-type thermocouple and an IR imager are used to measure and compare temperature predictions made by an existing probabilistic model with the addition of the power loss source term for this study. It has been established that across a range of operating frequencies and drive current, the Monte Carlo probabilistic model results in an overall error of 0.7% in winding losses without the ferromagnetic core material and 2.6% with the core material.
Implementation of developed model to determine losses, field enhancement, field uniformity and multipole characteristics at the required reference radius in the aperture of a novel electromagnet to be used for carbon beam therapy is currently underway. Previously inconceivable simulation domains such as stranded litz wires and thin iron laminates have now become a possibility employing the developed mode
Post-COVID Syndrome in Patients With Comorbid Hypertension or Diabetes: A Narrative Review of Long-Term Outcomes
No full textPost-COVID syndrome (PCS), or long COVID, refers to a cluster of enduring symptoms that extend beyond the acute phase of the initial SARS-CoV-2 infection. Acute infection predominantly impacts the respiratory tract, but there is growing evidence for the multisystem involvement, such as cardiovascular, metabolic, and neurological, to be responsible for the prolonged presentation in PCS. Underlying cardiometabolic vulnerability may contribute to a high degree of susceptibility in patients with comorbidities like hypertension (HTN) and diabetes mellitus (DM). This narrative review summarizes current literature regarding PCS in patients with HTN and/or DM, focusing on proposed pathophysiological mechanisms, clinical manifestations, and reported long-term outcomes. In these populations, PCS has been linked across studies to processes including endothelial dysfunction, chronic low-grade inflammation, autonomic imbalance, and potential dysregulation of the renin-angiotensin-aldosterone system (RAAS). Persistent cardiovascular, metabolic, and neurocognitive symptoms are reported, but the magnitude and patterns of risk vary across studies, while comparative findings across HTN and DM remain heterogeneous. Symptoms reported frequently include fatigue, cognitive impairment (“brain fog”), and psychological distress, supporting the multisystem complexity of PCS. Although, previous work has indicated that cardiometabolic comorbidities could interact and moderate PCS severity and persistence, there is an important shortfall of both causality and prognosis, as well as the management of PCS. Longitudinal studies are needed for future research regarding risk stratification, disease course, and targeted interventions in individuals with PCS with comorbid high blood pressure and diabetes
Evaluating the Implications of a Coronary Artery Calcium Score of Zero (CAC = 0) in Modern Risk Prediction: Is Zero Truly Zero?
No full textCoronary artery calcium (CAC) scoring is a well-validated screening tool used to calculate the amount of calcified plaque deposited in coronary arteries from a computed tomography (CT) scan. It stratifies patients by risk to predict their future probability of cardiovascular disease and helps establish the ideal preventive therapies. Considering these factors, the purpose of this narrative review is to evaluate the latest research on the effectiveness of CAC scoring, explore the various limitations and challenges faced in utilizing this tool, and discuss alternative investigations commonly used to supplement it for risk stratification. To achieve this, a narrative review was conducted by searching recent literature through databases such as PubMed, Cochrane, and Google Scholar. Identified literature included large population cohort studies and systematic reviews from the last five years, focusing on CAC scoring, cardiovascular risk prediction, ethnicity, artificial intelligence (AI) integration, and secondary prevention. The literature identified generally shows that the validity of CAC scoring is strongly debated due to its variable efficacy in symptomatic versus asymptomatic patients and in the context of ethnic variations, with many studies having supported the validity of this scoring tool, but others challenging its ability to prognosticate cardiovascular disease due to the presence of these external factors, which could lead to an inaccurate representation of the score. As a result, a major recommendation has been to combine the calculated score with pre-existing patient risk factors when making clinical judgments to guide prompt, individualized primary and secondary preventive care. Studies have shown that patients with varying ethnic backgrounds and also those who are symptomatic for stable cardiovascular disease have confounding risk factors that can lead to a false representation of their score and could potentially be at a higher than predicted risk of major cardiovascular events even with a score of zero. In conclusion, the use of CAC scoring remains a valuable prognostic tool for predicting a patient’s cardiovascular prognosis; however, its interpretation must consider correlation with clinical, biochemical, and demographic contexts to optimize decision-making. The literature has also identified the potential for improving the precision and effectiveness of major adverse cardiovascular event (MACE) prediction using traditional scoring methods by incorporating AI, including automated scoring tools and calcium-omics models, into CAC scoring
Erythropoiesis-Stimulating Agents (ESAs) in Chronic Kidney Disease and Cancer-Related Anemia: A Narrative Review of Literature
No full textAnemia associated with chronic kidney disease (CKD) and cancer is conventionally managed with packed red blood cell (PRBC) transfusions or erythropoietin-stimulating agents (ESAs) like epoetin alfa; however, transfusions are limited by complications such as alloimmunization and infection risk, which has led to ESAs becoming the preferred standard of care. Additional therapy may include iron supplementation, which potentially causes complications such as iron overload and infection risks in respective patient populations. The introduction of recombinant human erythropoietin (rhEPO) in 1989 improved anemia management but also raised concerns about adverse cardiovascular outcomes in many studies. Current guidelines promote careful ESA use to balance benefits and risks, while alternatives like hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) show promise in reducing such adverse effects. This review explores ESA trends, challenges, and emerging therapies for anemia in CKD and cancer patients and their implications in clinical use.
The literature search for this narrative review was conducted on PubMed in January 2025. The search was restricted to articles published between January 2020 and January 2025, focusing on randomized controlled trials (RCTs), narrative reviews, systematic reviews, and meta-analyses. The initial PubMed search yielded 454 articles, which were subsequently screened according to the inclusion and exclusion criteria, resulting in a final selection of 58 publications that satisfied the eligibility requirements.
Overall, evidence from these studies suggests that ESAs are considerably beneficial in correcting anemia and lowering the need for blood transfusions in adult patients with CKD. However, concerns about adverse cardiovascular outcomes and their effects on optimal hemoglobin targets have indicated the need to shift treatment approaches. These articles have also suggested recent developments, including the advent of HIF-PHIs and sodium-glucose cotransporter-2 (SGLT-2) inhibitors, which have been shown to offer safer and therapeutically promising alternatives in anemia of CKD and cancer-related anemia. Tailored approaches that take patient-specific factors into account are necessary for optimizing outcomes, suggesting that further research is required to evaluate the efficacy and risks of these novel treatments within clinical settings.
The narrative review has summarized the benefits and drawbacks of ESAs as a widely used treatment for anemia of CKD and cancer-related anemia. Studies identified in this review have shown that ESAs are linked to increased risks of adverse cardiovascular events, tumor progression in cancers, and higher mortality rates. The emerging alternative of HIF-PHIs shows promise in mitigating these adverse risks with a similar treatment efficacy to ESAs. However, there is still a lack of long-term safety data on these treatment options, and future research should focus on determining this risk profile as well as potential dosing strategies to potentially guide the use of HIF-PHIs in future clinical practice as a novel therapeutic alternative for anemia of CKD and cancer-related anemia
