BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Maria-Carme Calderer (University of Minnesota) DTSTART:20200429T150000Z DTEND:20200429T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/1 DESCRIPTION:Title: 3- Dimensional Solitons in Nematic Liquid Crystals subject to AC Fields\n by Maria-Carme Calderer (University of Minnesota) as part of Global Semina r on Mathematical Modeling and Applications\n\n\nAbstract\nI will start wi th a survey of liquid crystal models and related mathematics\, and subsequ ently focus on recent work on dynamics of structures that result from the coupling of electrokinetic\, elastic and viscous effects. From point of vi ew of applications the work falls into research of the role of liquid crys tal based nanotransport devices. We show that spatially localized three-di mensional solitary waves of molecular reorientation can form under the app lication of an AC field: self-trapped bullets of oscillating molecular dir ector\, that move at very high speed perpendicularly to the electric field and to the initial alignment direction. The bullets or tuxedos are true s olitons that preserve spatially confined shapes and survive collisions.\n\ nWe analyze a model that combines equations of liquid crystal dynamics cou pled with Poisson-Nearst-Planck equations of electrokinetics. Flexoelectri city is the main driving mechanism. \n\nWork (joint with Ashley Earls) bas ed on laboratory experiments by Lavrentovich et al.\n\nZoom Meeting ended\ n LOCATION:https://researchseminars.org/talk/GSMMA/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Yiwei Wang (Illinois Institute of Technology) DTSTART:20200506T150000Z DTEND:20200506T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/2 DESCRIPTION:Title: Va riational Schemes to Generalized Diffusions\, Gradient flows and Beyond: A n Discrete Energetic Variational Approach\nby Yiwei Wang (Illinois Ins titute of Technology) as part of Global Seminar on Mathematical Modeling a nd Applications\n\n\nAbstract\nIn this talk\, we present a systematic fram ework of deriving variational schemes for generalized diffusions and gradi ent flows\, by a discrete energetic variational approach\, which performs an energetic variational approach (EnVarA) at a semi-discrete level. In pa rticular\, we apply such an approach to construct variational Lagrangian s chemes and particle methods for porous medium type generalized diffusion a nd Allen-Cahn type equations. Numerical examples show the advantages of ou r schemes in capturing singularities\, thin diffuse interfaces\, and free boundaries. Our approach also has a potential connection application in Va riational Inference problems in the field of machine learning. This is joi nt work with Professor Chun Liu (IIT).\n\nZoom meeting ended\n LOCATION:https://researchseminars.org/talk/GSMMA/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Ryan Murray (North Carolina State University) DTSTART:20200513T150000Z DTEND:20200513T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/3 DESCRIPTION:Title: Vo rtices\, instabilities\, and non-uniqueness in incompressible fluids\n by Ryan Murray (North Carolina State University) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nVortices form im portant structures in many fluids problems\, such as the shear layers that form behind airplane wings. These structures also strongly influence mode lling in turbulent flows. Despite their fundamental importance to fluid dy namics\, vortices involve point singularities and are intimately linked wi th well known instabilities in fluids\; for these reasons they are challen ging to model and analyze mathematically. I will discuss various mathemati cal frameworks for describing vortices in the context of the incompressibl e Euler equation in two dimensions\, drawing connections to both physical motivation and to outstanding questions in mathematical analysis. I will c onclude by discussing recent work with Alberto Bressan\, which studies how to rigorously link point vortices with non-uniqueness and unpredictabilit y in solutions of Euler's equation.\n\nthe meeting has ended\n LOCATION:https://researchseminars.org/talk/GSMMA/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Robert Eisenberg (Rush University\, Illinois Institute of Technolo gy) DTSTART:20200520T150000Z DTEND:20200520T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/4 DESCRIPTION:Title: Io ns in channels and bulk: mathematics and molecular biology\nby Robert Eisenberg (Rush University\, Illinois Institute of Technology) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nLi fe and most of chemistry occurs in ionic solutions\, but ionic solutions h ave only recently been recognized as the complex fluids that they are. The molecular view shows ions interacting with surrounding water and nearby i ons. Everything is correlated in a complex way because ions and water have diameters comparable to their interaction length. The molecular scale sho ws only a small part of the correlation enforced by electrodynamics. Curre nt defined as Maxwell did to include the ethereal current is exactly conse rved\, and therefore correlated\, over all scales reaching to macroscopic boundary conditions some 1e9 larger than atoms crucial in batteries and n erve cells.\n

\n\n Jinn Liang Liu and I have built a molecular fiel d theory PNPB Poisson Nernst Planck Bikerman that deals with water as mole cules and describes local interactions with a steric potential that depend s on the volume fraction of molecules and voids between them. The correlat ions of electrodynamics are described by a fourth-order differential opera tor that gives (as outputs) ion-ion and ion-water correlations\; the diele ctric response (permittivity) of ionic solutions\; and the polarization of water molecules\, all using a single correlation length parameter. The th eory fits experimental data on activity and differential capacitance in io nic solutions of varying composition and content\, including mixtures. Pot assium channels\, Gramicidin\, L-type calcium channels\, and the Na/Ca tra nsporter are computed in three dimensions from structures in the Protein D ata Bank.\n

\n\nNumerical analysis faces challenges: \n
    \n
  1. Geometric singularities of molecular surfaces
    2. \n
  2. strong electr ic fields (100 mV/nm) and resulting exponential nonlinearities\, and the < /li>\n
  3. enormous concentrations (> 10 M) often found where ions are i mportant\, for example\, near electrodes in batteries\, in ion channels\, and in active sites of proteins.
    4. \n
  4. Wide ranging concentrations of 1e-1 to 1e-8 M in and near almost every protein in biological cells ma ke matters worse.
    5. \n
\n\nChallenges have been overcome using meth ods developed over many decades by the large community that works on the c omputational electronics of semiconductors.\n\nmeeting ended\n LOCATION:https://researchseminars.org/talk/GSMMA/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Rolf Ryham (Fordham University) DTSTART:20200527T150000Z DTEND:20200527T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/5 DESCRIPTION:Title: Me mbrane mechanics and rupture using coarse-grained hydrophobic attraction p otentials\nby Rolf Ryham (Fordham University) as part of Global Semina r on Mathematical Modeling and Applications\n\n\nAbstract\nThe talk goes o ver key modeling approaches for describing lipid bilayer membranes\, inclu ding particle-based simulation\, theoretical continuum mechanical descript ion\, fluid mechanical models and direct connections between theory and ex periment. The second part of the talk gives a mesoscopic formulation alter native to the standard Helfrich hamiltonian. Motivated by considerations o f hydrophobic surfaces that arise in theoretical studies of membrane fusio n\, the formulation is flexible enough to resolve the details of molecular transitions while retaining the continuum features of bilayer away from t he transitions. The framework assumes coarse-grained lipid 'particles'\, t hat interact through the solution of an appropriate second order elliptic PDE in the aqueous phase. Boundary conditions on each particle directly mo del the amphiphilic property of lipid\, and lead to\, as simulation output s\, elastic properties previously assumed in membrane mechanics. A manuscr ipt in SIAM J Multiscale Modeling and Simulation (2020) summarizes some of the results.\n\nmeeting has ended\n LOCATION:https://researchseminars.org/talk/GSMMA/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Bo Li (University of California\, San Diego) DTSTART:20200603T150000Z DTEND:20200603T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/6 DESCRIPTION:Title: Va riational implicit-solvent predictions of the ligand-receptor (un)binding kinetics\nby Bo Li (University of California\, San Diego) as part of G lobal Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nLig and-receptor binding and unbinding are fundamental molecular processes\, a nd are particularly essential to drug efficacy\, whereas water fluctuation s impact the corresponding thermodynamics and kinetics. We develop a varia tional implicit-solvent model (VISM) to calculate the potential of mean fo rce (PMF) as well as the solute-solvent interfacial structures of dry and wet states for a model ligand-pocket system. We also combine our VISM with the string method for transition paths to obtain the dry-wet transition r ates\, and conduct two-state Brownian dynamics simulations of the ligand s tochastic motion\, providing the mean first-passage times for the ligand-p ocket binding and unbinding. We find that the dewetting transition around the pocket is slowed down as the ligand approaches the pocket but is peake d suddenly once the ligand enters the pocket. In contrast to binding\, the ligand unbinding involves a much larger timescale due to a high energy ba rrier at the pocket entrance. The dry-wet fluctuation slows down the bindi ng but accelerates the unbinding process. Without any explicit description of individual water molecules\, our predictions are in a very good\, qual itative and semi-quantitative\, agreement with existing explicit-water mol ecular dynamics simulations\, providing a promising step in further effici ent studies of the ligand-receptor binding/unbinding kinetics. This is joi nt work with Shenggao Zhou\, R. Gregor Weiss\, Li-Tien Cheng\, Joachim Dzu biella\, and J. Andrew McCammon.\n\ntalk has ended\n LOCATION:https://researchseminars.org/talk/GSMMA/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Guo-Wei Wei (Michigan State University) DTSTART:20200617T150000Z DTEND:20200617T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/7 DESCRIPTION:Title: Ma thematical AI for drug discovery\nby Guo-Wei Wei (Michigan State Unive rsity) as part of Global Seminar on Mathematical Modeling and Applications \n\n\nAbstract\nArtificial intelligence (AI) has fundamentally changed the landscape of science\, technology\, industry\, and social media in the pa st few years. It holds a great future for discovering new drugs significan tly faster and cheaper. However\, AI-based drug discovery encounters obsta cles arising from the structural complexity of protein-drug interactions a nd the high dimensionality of drug candidates’ chemical space. We tackle these challenges mathematically. Our work focuses on reducing the biomole cular complexity and dimensionality in AI. We have introduced evolutionary de Rham-Hodge\, algebraic topology\, and persistent spectral graph theory to obtain high-level abstractions of protein-drug interactions and thus s ignificantly enhance AI's ability to handle excessively large datasets of complex biomolecules in drug discovery. Using our mathematical AI approac h\, my team has been a top winner in D3R Grand Challenges\, a worldwide an nual competition series in computer-aided drug design and discovery in the past three years. I will briefly discuss Math and AI-based drug repositio ning for COVID-19.\n\nthe meeting ended\n LOCATION:https://researchseminars.org/talk/GSMMA/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Chun Liu (Illinois Institute of Technology) DTSTART:20200715T150000Z DTEND:20200715T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/8 DESCRIPTION:Title: La w of mass action and energetic variational approaches\nby Chun Liu (Il linois Institute of Technology) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nIn this talk\, we'll present a sy stematic variational derivation to generalize the mass action kinetics of chemical reactions with detailed balance using an energetic variational ap proach. Our approach starts with an energy dissipation law for a chemical reaction system\,which could be argued to carry all the information of the dynamics. The dynamics of the system is determined by both the choice of the free energy\, as well as the dissipation\, the entropy production. Thi s approach enables us to capture the coupling and competition of various m echanisms\, including mechanical effects such as diffusion\, drift in an e lectric field\, as well as the thermal effects. We will also discuss sever al practical examples under this approach\, in particular\, the modeling o f wormlike micellar solutions. This is a joint work with Bob Eisenberg\, P ei Liu\, Yiwei Wang and Tengfei Zhang.\n LOCATION:https://researchseminars.org/talk/GSMMA/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Leili Shahriyari (University of Massachusetts Amherst) DTSTART:20200624T150000Z DTEND:20200624T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/9 DESCRIPTION:Title: A path toward personalized cancer treatments\nby Leili Shahriyari (Unive rsity of Massachusetts Amherst) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nA major clinical challenge for ca ncer therapies is to obtain an effective treatment strategy for each patie nt or at least identify a subset of patients who could benefit from a par ticular treatment. Since each cancer has its own unique features\, it is v ery important to obtain personalized cancer treatments and find a way to tailor treatment strategies for each patient. Recently\, mathematical mode ls have been commonly used to discover\, validate\, and test drugs. Since these models are a complex system of nonlinear equations with many unknown parameters\, estimating the values of the model's parameters is extremely difficult. Existing parameter estimation methods for these models often use assembled data from various sources rather than a single curated datas et. These datasets are usually obtained through various biological experim ents\, in vitro and in vivo animal studies. To arrive at personalized trea tments\, we need to obtain values of parameters of the model for each pati ent separately. Since the set of variables of the model includes relative amount of each cell type and cytokines in the tumor\, we developed a tumor deconvolution software\, which is a combination of recently developed met hods\, to predict the relative amount of these variables from the gene exp ression profile of the tumor. The output of the tumor deconvolution softwa re can be used to predict the values of the parameters for each patient. I n other words\, we propose to use patients’ gene expression data of prim ary tumor to estimate the values of parameters of the mathematical model f or each patient separately\, instead of the common approach of assuming th ese parameters have the same values across all patients and using animal s tudies to estimate them. This new approach provides us with a unique oppor tunity to suggest the optimal treatment strategy for each patient and pred ict the efficacy of each treatment for each patient.\n LOCATION:https://researchseminars.org/talk/GSMMA/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Shawn D. Ryan (Cleveland State University) DTSTART:20200701T150000Z DTEND:20200701T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/10 DESCRIPTION:Title: M athematics Provides Insight Into Self-Organization in Active Biosystems\nby Shawn D. Ryan (Cleveland State University) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nIn this talk we will consider how mathematical modeling\, analysis\, and simulation can be used to provide new insight into biological phenomena. In particular\, we focus on the self-organization of large-scale groups of insects and swimm ing bacteria. This talk will show how simple models for active biosystems can address complex ecological problems as well as lead to the development of novel biomaterials. What makes these problems interesting is that ind ividual interactions at the microscale lead to the onset of mesoscale and then macroscale patterns. In addition\, when animals exhibit collective be havior one can observe remarkable properties such as enhanced movement spe ed\, pattern formation\, and increased mixing. Mathematics provides a deep understanding of how and why these properties emerge and is fundamental t o pressing biological problems.\n\nJoin Zoom Meeting\nMeeting ID: 970 1588 0121\nPassword: 283709\n LOCATION:https://researchseminars.org/talk/GSMMA/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Yekaterina Epshteyn (The University of Utah) DTSTART:20200708T150000Z DTEND:20200708T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/11 DESCRIPTION:Title: G rain structure\, grain growth and evolution of the grain boundary network in polycrystalline materials: theory\, simulations\, and experiments\n by Yekaterina Epshteyn (The University of Utah) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nMost technologica lly useful materials are polycrystalline microstructures\ncomposed of myri ad small monocrystalline cells/grains separated by grain\nboundaries/inter faces. Grains and grain boundaries play a crucial role in\ndetermining the properties of materials across multiple scales.\n\nOne method by which th e grain structure is engineered is through grain\ngrowth or coarsening of a starting structure. Grain growth can be viewed\nas the evolution of a la rge metastable network\, and can be mathematically\nmodeled by a set of de terministic local evolution laws for the growth of\nan individual\ngrain c ombined with stochastic models to describe the interaction between\ngrains . Thus\, to develop a predictive and prescriptive theory for\npolycrystall ine materials\, investigation of a broad range of statistical\nmeasures fo r microstructure evolution during grain growth is needed. In\nthis talk\, we will discuss recent progress on modeling\, simulation\,\nanalysis and e xperiments of the evolution of the grain boundary network in\npolycrystall ine materials.\n LOCATION:https://researchseminars.org/talk/GSMMA/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Wenzhong Zhang (Southern Methodist University) DTSTART:20200722T150000Z DTEND:20200722T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/12 DESCRIPTION:Title: F ast multipole method for Helmholtz equation in layered media\nby Wenzh ong Zhang (Southern Methodist University) as part of Global Seminar on Mat hematical Modeling and Applications\n\n\nAbstract\nThe fast multipole meth od (FMM) has been a revolutionary development in modern computational algo rithms for many-body problems\, which reduces the complexity of long-range interactions among N particles from O(N^2) to O(N) or O(N log N). In this talk we generalize the FMM for Helmholtz equation to handle the layered m edia. Our approach starts from the 2-D case. The multipole expansion (ME) and the multipole-to-local translation (M2L) are introduced in the frequen cy domain together with theoretical analysis showing their exponential con vergence using the Cagniard--de Hoop transform. The analysis further sugge sts the FMM framework for layered media should use polarized sources for t he far-field separation. Finally we apply the FMM to the 3-D layered probl em and discuss the numerical result. This is a joint work with Bo Wang and Wei Cai.\n\nMeeting ID: 970 1588 0121\nPasscode: 835247\n LOCATION:https://researchseminars.org/talk/GSMMA/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Xiaozhe Hu (Tufts University) DTSTART:20200729T150000Z DTEND:20200729T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/13 DESCRIPTION:Title: R obust Preconditioners for Mixed-dimemsional Models of Flow in Fractured Po rous Media\nby Xiaozhe Hu (Tufts University) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nMixed-dimensiona l partial differential equations arise in many physical applications inclu ding flow in fractured porous media\, where the fractures and their inters ections form a hierarchy of lower-dimensional submanifolds. An essential c omponent\, and usually the most time-consuming part of simulating PDEs\, i s solving the large-scale and ill-conditioned linear systems of equations arising from discretizations. In this work\, we generalize the traditional framework of designing preconditioners for the saddle point systems and d evelop effective preconditioners that are robust with respect to the physi cal and discretization parameters for mixed-dimensional models for flow in fractured porous media. Preliminary numerical experiments are presented t o support the theory and demonstrate the robustness of our preconditioners . This is joint work with Wietse Boon (KTH) and Ana Budisa (Simula)\n\nMe eting ID: 970 1588 0121\nPasscode: 614469\n LOCATION:https://researchseminars.org/talk/GSMMA/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Giordano Tierra (University of North Texas) DTSTART:20200902T150000Z DTEND:20200902T160000Z DTSTAMP:20260422T212830Z UID:GSMMA/14 DESCRIPTION:Title: E nergy-stable numerical schemes for fluid vesicles with internal nematic or der\nby Giordano Tierra (University of North Texas) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nModels of flows containing vesicles membranes with liquid crystalline phases have b een widely studied in recent times due to its connection with biological a pplications.\n\nDuring the seminar I will present the main ideas to derive a new model to represent the interaction between flows and vesicle membra nes with internal nematic order and preferential orientation of their mole cules in the membrane. In fact\, the dynamics of this system is determined by the dissipation of an energy that regulates the competition between di fferent effects\, through the kinetic\, bending\, elastic and anchoring en ergies.\n\nMoreover\, I will introduce a new unconditionally energy-stable numerical scheme to approximate the model\, and I will present several nu merical results in order to show the well behavior of the proposed scheme and the dynamics of this type of vesicle membranes.\n\nThis contribution i s based on joint work with Francisco Guill ́en-Gonzal ́ez (Universidad d e Sevilla\,\nSpain) and Mar ́ıa Angeles Rodr ́ıguez-Bellido (Universid ad de Sevilla\, Spain).\n\nZoom Meeting ID: 970 1588 0121\nPasscode: 78150 7\n LOCATION:https://researchseminars.org/talk/GSMMA/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Francesco De Anna (Universität Würzburg) DTSTART:20201111T160000Z DTEND:20201111T170000Z DTSTAMP:20260422T212830Z UID:GSMMA/15 DESCRIPTION:Title: O n classical solutions for some Oldroyd-B model of viscoelastic fluids\ nby Francesco De Anna (Universität Würzburg) as part of Global Seminar o n Mathematical Modeling and Applications\n\n\nAbstract\nThis talk is devot ed to the analysis of an Oldroyd-B system of PDEs which models the evoluti on of certain viscoelastic fluids. A particular emphasis is spent on the s o called "corotational" model. We are interested in the well-posedness the ory of classical solutions. We show in a bidimensional setting that\, with out any restriction on the initial data\, the solutions exist globally in time and they are unique.\n\nThis result is due to the particular structur e of the system which allows to propagate high regularities of the solutio ns\, in particular a Lipschitz regularity of the velocity field. A specifi c toolbox of Fourier Analysis is presented to address the mentioned result .\n LOCATION:https://researchseminars.org/talk/GSMMA/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Navid Mohammad Mirzaei (University of Massachusetts Amherst) DTSTART:20201202T160000Z DTEND:20201202T170000Z DTSTAMP:20260422T212830Z UID:GSMMA/16 DESCRIPTION:Title: S imple model of atherosclerosis in cylindrical arteries: impact of anisotro pic growth on Glagov remodeling\nby Navid Mohammad Mirzaei (University of Massachusetts Amherst) as part of Global Seminar on Mathematical Model ing and Applications\n\n\nAbstract\nIn 1987\, Seymour Glagov observed that arteries went through a two-stage remodeling process as a result of plaqu e growth: first\, a compensatory phase where the lumen area remains approx imately constant and second\, an encroachment phase where the lumen area d ecreases over time. In this paper we investigate the effect of growth anis otropy on Glagov remodeling in five different cases: pure radial\, pure ci rcumferential\, pure axial\, isotropic and general anisotropic growth wher e the elements of the growth tensor are chosen to minimize the total energ y. We suggest that the nature of anisotropy is inclined towards the growth direction that requires the least amount of energy. Our framework is the theory of morphoelasticity on an axisymmetric arterial domain. For each ca se we explore their specific effect on the Glagov curves. For the latter t wo cases we also provide the changes in collagen fiber orientation and len gth in the intimate\, media and adventitia. In addition\, we compare the t otal energy produced by growth in radial\, circumferential and axial direc tion and deduce that using a radially dominant anisotropic growth leads to lower strain energy than isotropic growth.\n LOCATION:https://researchseminars.org/talk/GSMMA/16/ END:VEVENT END:VCALENDAR