167 research outputs found

    Multiscale asymptotic method for Maxwell's equations in composite materials

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    Author name used in this publication: Yanping Lin2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

    A multiscale approach for optimal control problems of linear parabolic equations

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    Author name used in this publication: Lin, Yanping2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

    Multiscale asymptotic method for Steklov eigenvalue equations in composite media

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    Author name used in this publication: Yanping Lin2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

    Coexistence and optimal control problems for a degenerate predator-prey model

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    In this paper we present a predator-prey mathematical model for two biological populations which dislike crowding. The model consists of a system of two degenerate parabolic equations with nonlocal terms and drifts. We provide conditions on the system ensuring the periodic coexistence, namely the existence of two non-trivial non-negative periodic solutions representing the densities of the two populations. We assume that the predator species is harvested if its density exceeds a given threshold. A minimization problem for a cost functional associated with this process and with some other significant parameters of the model is also considered. \ua9 2010 Elsevier Inc

    Finite Element Convergence for the Joule Heating Problem with Mixed Boundary Conditions

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    We prove strong convergence of conforming finite element approximations to the stationary Joule heating problem with mixed boundary conditions on Lipschitz domains in three spatial dimensions. We show optimal global regularity estimates on creased domains and prove a priori and a posteriori bounds for shape regular meshes.Comment: Keywords: Joule heating problem, thermistors, a posteriori error analysis, a priori error analysis, finite element metho

    Computing the first eigenpair of the p-Laplacian via inverse iteration of sublinear supersolutions

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    We introduce an iterative method for computing the first eigenpair (λp,ep)(\lambda_{p},e_{p}) for the pp-Laplacian operator with homogeneous Dirichlet data as the limit of (μq,uq)(\mu_{q,}u_{q}) as qpq\rightarrow p^{-}, where uqu_{q} is the positive solution of the sublinear Lane-Emden equation Δpuq=μquqq1-\Delta_{p}u_{q}=\mu_{q}u_{q}^{q-1} with same boundary data. The method is shown to work for any smooth, bounded domain. Solutions to the Lane-Emden problem are obtained through inverse iteration of a super-solution which is derived from the solution to the torsional creep problem. Convergence of uqu_{q} to epe_{p} is in the C1C^{1}-norm and the rate of convergence of μq\mu_{q} to λp\lambda_{p} is at least O(pq)O(p-q). Numerical evidence is presented.Comment: Section 5 was rewritten. Jed Brown was added as autho

    A functional model, eigenvalues, and finite singular critical points for indefinite Sturm-Liouville operators

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    Eigenvalues in the essential spectrum of a weighted Sturm-Liouville operator are studied under the assumption that the weight function has one turning point. An abstract approach to the problem is given via a functional model for indefinite Sturm-Liouville operators. Algebraic multiplicities of eigenvalues are obtained. Also, operators with finite singular critical points are considered.Comment: 38 pages, Proposition 2.2 and its proof corrected, Remarks 2.5, 3.4, and 3.12 extended, details added in subsections 2.3 and 4.2, section 6 rearranged, typos corrected, references adde

    Retinoids cause apoptosis in pancreatic cancer cells via activation of RAR-γ and altered expression of Bcl-2/Bax

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    All-trans-retinoic acid and 9-cis-retinoic acid have been reported to have inhibitory effects on pancreatic adenocarcinoma cells and we have shown that this is partly due to induction of apoptosis. In this study, the mechanisms whereby 9-cis-retinoic acid induces apoptosis in these cells were investigated. An involvement of the Bcl-2 family of proteins was shown, such that 9-cis-retinoic acid causes a decrease in the Bcl-2/Bax ratio. Overexpression of Bcl-2 also resulted in inhibition of apoptosis induced by 9-cis-retinoic acid. Furthermore, two broad-range caspase inhibitors blocked DNA fragmentation induced by 9-cis-retinoic acid, but had no effect on viability defined by mitochondrial activity. Using synthetic retinoids, which bind selectively to specific retinoic acid receptor subtypes, we further established that activation of retinoic acid receptor-γ is essential for induction of apoptosis. Only pan-retinoic acid receptor and retinoic acid receptor-γ selective agonists reduced viability and a cell line expressing very low levels of retinoic acid receptor-γ is resistant to the effects of 9-cis-retinoic acid. A retinoic acid receptor-β/γ selective antagonist also suppressed the cytotoxic effects of 9-cis-retinoic acid in a dose-dependent manner. This study provides important insight into the mechanisms involved in suppression of pancreatic tumour cell growth by retinoids. Our results encourage further work evaluating the clinical use of receptor subtype selective retinoids in pancreatic carcinoma
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