Browsing by Author "Mathematical Sciences, School of Science"
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Item 3D simulation of a viscous flow past a compliant model of arteriovenous-graft annastomosis(Elsevier, 2019-03) Bai, Zengding; Zhu, Luoding; Mathematical Sciences, School of ScienceHemodialysis is a common treatment for end-stage renal-disease patients to manage their renal failure while awaiting kidney transplant. Arteriovenous graft (AVG) is a major vascular access for hemodialysis but often fails due to the thrombosis near the vein-graft anastomosis. Almost all of the existing computational studies involving AVG assume that the vein and graft are rigid. As a first step to include vein/graft flexibility, we consider an ideal vein-AVG anastomosis model and apply the lattice Boltzmann-immersed boundary (LB-IB) framework for fluid-structure-interaction. The framework is extended to the case of non-uniform Lagrangian mesh for complex structure. After verification and validation of the numerical method and its implementation, many simulations are performed to simulate a viscous incompressible flow past the anastomosis model under pulsatile flow condition using various levels of vein elasticity. Our simulation results indicate that vein compliance may lessen flow disturbance and a more compliant vein experiences less wall shear stress (WSS).Item A Candy Lover Learns to Optimize(University of Regina, 2023-03) Do, Anh Phuong; Rashid, Mamunur; Sarkar, Jyotirmoy; Mathematical Sciences, School of ScienceA container has two types of candies: Type A and Type B. Concerned about her child's well-being, a wise mom pronounces, “Each day, you can choose two candies from the container random. If they are of different types, you can eat them both. If they are of the same type, eat only one and return the other to the container.” We analyze the expected number of days needed to eat all candies in the container and the proportion of days the child eats two candies. Several other variations are either worked out or left for readers to solve.Item A closed model for the respiratory system in mammals(Springer Nature, 2012-07-16) Park, Choongseok; Molkov, Yaroslav; Ben-Tal, Alona; Shevtsova, Natalia; Smith, Jeffrey; Rybak, Ilya; Rubin, Jonathan; Mathematical Sciences, School of ScienceItem A conclusive theorem on Finsler metrics of sectional flag curvature(arXiv, 2018-12-22) Huang, Libing; Shen, Zhongmin; Mathematical Sciences, School of ScienceIf the flag curvature of a Finsler manifold reduces to sectional curvature, then locally either the Finsler metric is Riemannian, or the flag curvature is isotropic.Item A Literature Review of Similarities Between and Among Patients With Autism Spectrum Disorder and Epilepsy(Springer Nature, 2023-01-18) Assuah, Freda B.; Emanuel, Bryce; Lacasse, Brianna M.; Beggs, John; Lou, Jennie; Motta, Francis C.; Nemzer, Louis R.; Worth, Robert; Cravens, Gary D.; Mathematical Sciences, School of ScienceAutism spectrum disorder (ASD) has been shown to be associated with various other conditions, and most commonly, ASD has been demonstrated to be linked to epilepsy. ASD and epilepsy have been observed to exhibit high rates of comorbidity, even when compared to the co-occurrence of other disorders with similar pathologies. At present, nearly one-half of the individuals diagnosed with ASD also have been diagnosed with comorbid epilepsy. Research suggests that both conditions likely share similarities in their underlying disease pathophysiology, possibly associated with disturbances in the central nervous system (CNS), and may be linked to an imbalance between excitation and inhibition in the brain. Meanwhile, it remains unclear whether one condition is the consequence of the other, as the pathologies of both disorders are commonly linked to many different underlying signal transduction mechanisms. In this review, we aim to investigate the co-occurrence of ASD and epilepsy, with the intent of gaining insights into the similarities in pathophysiology that both conditions present with. Elucidating the underlying disease pathophysiology as a result of both disorders could lead to a better understanding of the underlying mechanism of disease activity that drives co-occurrence, as well as provide insight into the underlying mechanisms of each condition individually.Item A minimal model for a slow pacemaking neuron(Springer Nature, 2012-07-16) Kuznetsov, Alexey; Zakharov, Denis; Mathematical Sciences, School of ScienceItem A randomized trial comparing weight loss treatment delivered in large versus small groups(Springer Nature, 2014-09-24) Dutton, Gareth R.; Nackers, Lisa M.; Dubyak, Pamela J.; Rushing, Nicole C.; Huynh, Tuong-Vi T.; Tan, Fei; Anton, Stephen D.; Perri, Michael G.; Mathematical Sciences, School of ScienceBackground: Behavioral interventions for obesity are commonly delivered in groups, although the effect of group size on weight loss has not been empirically evaluated. This behavioral weight loss trial compared the 6- and 12-month weight changes associated with interventions delivered in a large group (LG) or small groups (SG). Methods: Obese adults (N = 66; mean age = 50 years; mean BMI = 36.5 kg/m2; 47% African American; 86% women) recruited from a health maintenance organization were randomly assigned to: (1) LG treatment (30 members/group), or (2) SG treatment (12 members/group). Conditions were comparable in frequency and duration of treatment, which included 24 weekly group sessions (months 1-6) followed by six monthly extended care contacts (months 7-12). A mixed effects model with unstructured covariance matrix was applied to analyze the primary outcome of weight change while accounting for baseline weight and dependence among participants' measurements over time. Results: SG participants lost significantly more weight than LG participants at Month 6 (-6.5 vs. -3.2 kg; p = 0.03) and Month 12 (-7.0 vs. -1.7 kg; p < 0.002). SG participants reported better treatment engagement and self-monitoring adherence at Months 6 and 12, ps < 0.04, with adherence fully mediating the relationship between group size and weight loss. Conclusions: Receiving obesity treatment in smaller groups may promote greater weight loss and weight loss maintenance. This effect may be due to improved adherence facilitated by SG interactions. These novel findings suggest that the perceived efficiency of delivering behavioral weight loss treatment to LGs should be balanced against the potentially better outcomes achieved by a SG approach.Item A System with Two Spare Units, Two Repair Facilities, and Two Types of Repairers(MDPI, 2022-03-08) Andalib, Vahid; Sarkar, Jyotirmoy; Mathematical Sciences, School of ScienceAssuming exponential lifetime and repair time distributions, we study the limiting availability 𝐴∞ as well as the per unit time-limiting profit 𝜔 of a one-unit system having two identical, cold standby spare units using semi-Markov processes. The failed unit is repaired either by an in-house repairer within an exponential patience time T or by an external expert who works faster but charges more. When there are two repair facilities, we allow the regular repairer to begin repair or to continue repair beyond T if the expert is busy. Two models arise accordingly as the expert repairs one or all failed units during each visit. We show that (1) adding a second spare to a one-unit system already backed by a spare raises 𝐴∞ as well as 𝜔; (2) thereafter, adding a second repair facility improves both criteria further. Finally, we determine whether the expert must repair one or all failed units to maximize these criteria and fulfill the maintenance management objectives better than previously studied models.Item Ability and Diversity of Skills(AMS, 2023) Geller, William; Misiurewicz, Michał; Mathematical Sciences, School of ScienceItem Accessibility of the Boundary of the Thurston Set(Taylor & Francis, 2023) Silvestri, Stefano; Pérez, Rodrigo A.; Mathematical Sciences, School of ScienceConsider two objects associated to the Iterated Function System (IFS) {1+𝜆𝑧,−1+𝜆𝑧}: the locus ℳ of parameters 𝜆∈𝔻∖{0} for which the corresponding attractor is connected; and the locus ℳ0 of parameters for which the related attractor contains 0. The set ℳ can also be characterized as the locus of parameters for which the attractor of the IFS {1+𝜆𝑧,𝜆𝑧,−1+𝜆𝑧} contains 𝜆−1. Exploiting the asymptotic similarity of ℳ and ℳ0 with the respective associated attractors, we give sufficient conditions on 𝜆∈∂ℳ or ∂ℳ0 to guarantee it is path accessible from the complement 𝔻∖ℳ.