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:20260404T094752Z UID:GSMMA/1 DESCRIPTION:Title: 3-Dimensional Solitons in Nematic Liquid Crystals subject to AC Field s\nby Maria-Carme Calderer (University of Minnesota) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nI will s tart with a survey of liquid crystal models and related mathematics\, and subsequently focus on recent work on dynamics of structures that result fr om the coupling of electrokinetic\, elastic and viscous effects. From poin t of view of applications the work falls into research of the role of liqu id crystal based nanotransport devices. We show that spatially localized t hree-dimensional solitary waves of molecular reorientation can form under the application of an AC field: self-trapped bullets of oscillating molecu lar director\, that move at very high speed perpendicularly to the electri c field and to the initial alignment direction. The bullets or tuxedos are true solitons that preserve spatially confined shapes and survive collisi ons.\n\nWe analyze a model that combines equations of liquid crystal dynam ics coupled with Poisson-Nearst-Planck equations of electrokinetics. Flexo electricity is the main driving mechanism. \n\nWork (joint with Ashley Ear ls) based on laboratory experiments by Lavrentovich et al.\n\nZoom Meeting ended\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Yiwei Wang (Illinois Institute of Technology) DTSTART:20200506T150000Z DTEND:20200506T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/2 DESCRIPTION:Title: Variational Schemes to Generalized Diffusions\, Gradient flows and Be yond: An Discrete Energetic Variational Approach\nby Yiwei Wang (Illin ois Institute of Technology) as part of Global Seminar on Mathematical Mod eling and Applications\n\n\nAbstract\nIn this talk\, we present a systemat ic framework of deriving variational schemes for generalized diffusions an d gradient flows\, by a discrete energetic variational approach\, which pe rforms an energetic variational approach (EnVarA) at a semi-discrete level . In particular\, we apply such an approach to construct variational Lagra ngian schemes and particle methods for porous medium type generalized diff usion and Allen-Cahn type equations. Numerical examples show the advantage s of our schemes in capturing singularities\, thin diffuse interfaces\, an d free boundaries. Our approach also has a potential connection applicatio n in Variational Inference problems in the field of machine learning. This is joint work with Professor Chun Liu (IIT).\n\nZoom meeting ended\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Ryan Murray (North Carolina State University) DTSTART:20200513T150000Z DTEND:20200513T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/3 DESCRIPTION:Title: Vortices\, instabilities\, and non-uniqueness in incompressible fluid s\nby Ryan Murray (North Carolina State University) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nVortices form important structures in many fluids problems\, such as the shear laye rs that form behind airplane wings. These structures also strongly influen ce modelling in turbulent flows. Despite their fundamental importance to f luid dynamics\, vortices involve point singularities and are intimately li nked with well known instabilities in fluids\; for these reasons they are challenging to model and analyze mathematically. I will discuss various ma thematical frameworks for describing vortices in the context of the incomp ressible Euler equation in two dimensions\, drawing connections to both ph ysical motivation and to outstanding questions in mathematical analysis. I will conclude by discussing recent work with Alberto Bressan\, which stud ies how to rigorously link point vortices with non-uniqueness and unpredic tability in solutions of Euler's equation.\n\nthe meeting has ended\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Robert Eisenberg (Rush University\, Illinois Institute of Technolo gy) DTSTART:20200520T150000Z DTEND:20200520T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/4 DESCRIPTION:Title: Ions in channels and bulk: mathematics and molecular biology\nby Robert Eisenberg (Rush University\, Illinois Institute of Technology) as p art of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstr act\nLife and most of chemistry occurs in ionic solutions\, but ionic solu tions have only recently been recognized as the complex fluids that they a re. The molecular view shows ions interacting with surrounding water and n earby ions. Everything is correlated in a complex way because ions and wat er have diameters comparable to their interaction length. The molecular sc ale shows only a small part of the correlation enforced by electrodynamics . Current defined as Maxwell did to include the ethereal current is exactl y conserved\, and therefore correlated\, over all scales reaching to macro scopic boundary conditions some 1e9 larger than atoms crucial in batterie s and nerve cells.\n

\n\n Jinn Liang Liu and I have built a molecul ar field theory PNPB Poisson Nernst Planck Bikerman that deals with water as molecules and describes local interactions with a steric potential that depends on the volume fraction of molecules and voids between them. The c orrelations of electrodynamics are described by a fourth-order differentia l operator that gives (as outputs) ion-ion and ion-water correlations\; th e dielectric response (permittivity) of ionic solutions\; and the polariza tion of water molecules\, all using a single correlation length parameter. The theory fits experimental data on activity and differential capacitanc e in ionic solutions of varying composition and content\, including mixtur es. Potassium channels\, Gramicidin\, L-type calcium channels\, and the Na /Ca transporter are computed in three dimensions from structures in the Pr otein Data Bank.\n

\n\nNumerical analysis faces challenges: \n
    \ n
  1. Geometric singularities of molecular surfaces
    2. \n
  2. strong electric fields (100 mV/nm) and resulting exponential nonlinearities\, an d the
    3. \n
  3. enormous concentrations (> 10 M) often found where ion s are important\, for example\, near electrodes in batteries\, in ion chan nels\, and in active sites of proteins.
    4. \n
  4. Wide ranging concentr ations of 1e-1 to 1e-8 M in and near almost every protein in biological c ells make matters worse.
    5. \n
\n\nChallenges have been overcome usi ng methods developed over many decades by the large community that works o n the computational electronics of semiconductors.\n\nmeeting ended\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Rolf Ryham (Fordham University) DTSTART:20200527T150000Z DTEND:20200527T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/5 DESCRIPTION:Title: Membrane mechanics and rupture using coarse-grained hydrophobic attra ction potentials\nby Rolf Ryham (Fordham University) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nThe talk goes over key modeling approaches for describing lipid bilayer membranes\ , including particle-based simulation\, theoretical continuum mechanical d escription\, fluid mechanical models and direct connections between theory and experiment. The second part of the talk gives a mesoscopic formulatio n alternative to the standard Helfrich hamiltonian. Motivated by considera tions of hydrophobic surfaces that arise in theoretical studies of membran e fusion\, the formulation is flexible enough to resolve the details of mo lecular transitions while retaining the continuum features of bilayer away from the transitions. The framework assumes coarse-grained lipid 'particl es'\, that interact through the solution of an appropriate second order el liptic PDE in the aqueous phase. Boundary conditions on each particle dire ctly model the amphiphilic property of lipid\, and lead to\, as simulation outputs\, elastic properties previously assumed in membrane mechanics. A manuscript in SIAM J Multiscale Modeling and Simulation (2020) summarizes some of the results.\n\nmeeting has ended\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Bo Li (University of California\, San Diego) DTSTART:20200603T150000Z DTEND:20200603T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/6 DESCRIPTION:Title: Variational implicit-solvent predictions of the ligand-receptor (un)b inding kinetics\nby Bo Li (University of California\, San Diego) as pa rt of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstra ct\nLigand-receptor binding and unbinding are fundamental molecular proces ses\, and are particularly essential to drug efficacy\, whereas water fluc tuations impact the corresponding thermodynamics and kinetics. We develop a variational implicit-solvent model (VISM) to calculate the potential of mean force (PMF) as well as the solute-solvent interfacial structures of d ry and wet states for a model ligand-pocket system. We also combine our VI SM with the string method for transition paths to obtain the dry-wet trans ition rates\, and conduct two-state Brownian dynamics simulations of the l igand stochastic motion\, providing the mean first-passage times for the l igand-pocket binding and unbinding. We find that the dewetting transition around the pocket is slowed down as the ligand approaches the pocket but i s peaked suddenly once the ligand enters the pocket. In contrast to bindin g\, the ligand unbinding involves a much larger timescale due to a high en ergy barrier at the pocket entrance. The dry-wet fluctuation slows down th e binding but accelerates the unbinding process. Without any explicit desc ription of individual water molecules\, our predictions are in a very good \, qualitative and semi-quantitative\, agreement with existing explicit-wa ter molecular dynamics simulations\, providing a promising step in further efficient studies of the ligand-receptor binding/unbinding kinetics. This is joint work with Shenggao Zhou\, R. Gregor Weiss\, Li-Tien Cheng\, Joac him Dzubiella\, and J. Andrew McCammon.\n\ntalk has ended\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Guo-Wei Wei (Michigan State University) DTSTART:20200617T150000Z DTEND:20200617T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/7 DESCRIPTION:Title: Mathematical AI for drug discovery\nby Guo-Wei Wei (Michigan Stat e University) as part of Global Seminar on Mathematical Modeling and Appli cations\n\n\nAbstract\nArtificial intelligence (AI) has fundamentally chan ged the landscape of science\, technology\, industry\, and social media in the past few years. It holds a great future for discovering new drugs sig nificantly faster and cheaper. However\, AI-based drug discovery encounter s obstacles arising from the structural complexity of protein-drug interac tions and the high dimensionality of drug candidates’ chemical space. We tackle these challenges mathematically. Our work focuses on reducing the biomolecular complexity and dimensionality in AI. We have introduced evolu tionary de Rham-Hodge\, algebraic topology\, and persistent spectral graph theory to obtain high-level abstractions of protein-drug interactions and thus significantly enhance AI's ability to handle excessively large datas ets of complex biomolecules in drug discovery. Using our mathematical AI approach\, my team has been a top winner in D3R Grand Challenges\, a world wide annual competition series in computer-aided drug design and discovery in the past three years. I will briefly discuss Math and AI-based drug re positioning for COVID-19.\n\nthe meeting ended\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Chun Liu (Illinois Institute of Technology) DTSTART:20200715T150000Z DTEND:20200715T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/8 DESCRIPTION:Title: Law of mass action and energetic variational approaches\nby Chun Liu (Illinois Institute of Technology) as part of Global Seminar on Mathem atical Modeling and Applications\n\n\nAbstract\nIn this talk\, we'll prese nt a systematic variational derivation to generalize the mass action kinet ics of chemical reactions with detailed balance using an energetic variati onal approach. Our approach starts with an energy dissipation law for a ch emical reaction system\,which could be argued to carry all the information of the dynamics. The dynamics of the system is determined by both the cho ice of the free energy\, as well as the dissipation\, the entropy producti on. This approach enables us to capture the coupling and competition of va rious mechanisms\, including mechanical effects such as diffusion\, drift in an electric field\, as well as the thermal effects. We will also discus s several practical examples under this approach\, in particular\, the mod eling of wormlike micellar solutions. This is a joint work with Bob Eisenb erg\, Pei Liu\, Yiwei Wang and Tengfei Zhang.\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Leili Shahriyari (University of Massachusetts Amherst) DTSTART:20200624T150000Z DTEND:20200624T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/9 DESCRIPTION:Title: A path toward personalized cancer treatments\nby Leili Shahriyari (University of Massachusetts Amherst) as part of Global Seminar on Mathem atical Modeling and Applications\n\n\nAbstract\nA major clinical challenge for cancer therapies is to obtain an effective treatment strategy for eac h patient or at least identify a subset of patients who could benefit fro m a particular treatment. Since each cancer has its own unique features\, it is very important to obtain personalized cancer treatments and find a way to tailor treatment strategies for each patient. Recently\, mathematic al models 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 ex tremely difficult. Existing parameter estimation methods for these models often use assembled data from various sources rather than a single curate d dataset. These datasets are usually obtained through various biological experiments\, in vitro and in vivo animal studies. To arrive at personaliz ed treatments\, we need to obtain values of parameters of the model for ea ch patient separately. Since the set of variables of the model includes re lative amount of each cell type and cytokines in the tumor\, we developed a tumor deconvolution software\, which is a combination of recently develo ped methods\, to predict the relative amount of these variables from the g ene expression profile of the tumor. The output of the tumor deconvolution software can be used to predict the values of the parameters for each pat ient. In other words\, we propose to use patients’ gene expression data of primary tumor to estimate the values of parameters of the mathematical model for each patient separately\, instead of the common approach of assu ming these parameters have the same values across all patients and using a nimal studies to estimate them. This new approach provides us with a uniqu e opportunity to suggest the optimal treatment strategy for each patient a nd predict the efficacy of each treatment for each patient.\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Shawn D. Ryan (Cleveland State University) DTSTART:20200701T150000Z DTEND:20200701T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/10 DESCRIPTION:Title: Mathematics Provides Insight Into Self-Organization in Active Biosys tems\nby Shawn D. Ryan (Cleveland State University) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nIn this t alk we will consider how mathematical modeling\, analysis\, and simulation can be used to provide new insight into biological phenomena. In particul ar\, we focus on the self-organization of large-scale groups of insects an d swimming bacteria. This talk will show how simple models for active bios ystems can address complex ecological problems as well as lead to the deve lopment of novel biomaterials. What makes these problems interesting is t hat individual interactions at the microscale lead to the onset of mesosca le and then macroscale patterns. In addition\, when animals exhibit collec tive behavior one can observe remarkable properties such as enhanced movem ent speed\, pattern formation\, and increased mixing. Mathematics provides a deep understanding of how and why these properties emerge and is fundam ental to pressing biological problems.\n\nJoin Zoom Meeting\nMeeting ID: 9 70 1588 0121\nPassword: 283709\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Yekaterina Epshteyn (The University of Utah) DTSTART:20200708T150000Z DTEND:20200708T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/11 DESCRIPTION:Title: Grain structure\, grain growth and evolution of the grain boundary n etwork in polycrystalline materials: theory\, simulations\, and experiment s\nby Yekaterina Epshteyn (The University of Utah) as part of Global S eminar on Mathematical Modeling and Applications\n\n\nAbstract\nMost techn ologically useful materials are polycrystalline microstructures\ncomposed of myriad small monocrystalline cells/grains separated by grain\nboundarie s/interfaces. Grains and grain boundaries play a crucial role in\ndetermin ing the properties of materials across multiple scales.\n\nOne method by w hich the grain structure is engineered is through grain\ngrowth or coarsen ing of a starting structure. Grain growth can be viewed\nas the evolution of a large metastable network\, and can be mathematically\nmodeled by a se t of deterministic local evolution laws for the growth of\nan individual\n grain combined with stochastic models to describe the interaction between\ ngrains. Thus\, to develop a predictive and prescriptive theory for\npolyc rystalline materials\, investigation of a broad range of statistical\nmeas ures for microstructure evolution during grain growth is needed. In\nthis talk\, we will discuss recent progress on modeling\, simulation\,\nanalysi s and experiments of the evolution of the grain boundary network in\npolyc rystalline materials.\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Wenzhong Zhang (Southern Methodist University) DTSTART:20200722T150000Z DTEND:20200722T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/12 DESCRIPTION:Title: Fast multipole method for Helmholtz equation in layered media\nb y Wenzhong Zhang (Southern Methodist University) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nThe fast multipo le method (FMM) has been a revolutionary development in modern computation al algorithms for many-body problems\, which reduces the complexity of lon g-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 la yered media. Our approach starts from the 2-D case. The multipole expansio n (ME) and the multipole-to-local translation (M2L) are introduced in the frequency domain together with theoretical analysis showing their exponent ial convergence using the Cagniard--de Hoop transform. The analysis furthe r suggests the FMM framework for layered media should use polarized source s for the far-field separation. Finally we apply the FMM to the 3-D layere d problem and discuss the numerical result. This is a joint work with Bo W ang and Wei Cai.\n\nMeeting ID: 970 1588 0121\nPasscode: 835247\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Xiaozhe Hu (Tufts University) DTSTART:20200729T150000Z DTEND:20200729T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/13 DESCRIPTION:Title: Robust Preconditioners for Mixed-dimemsional Models of Flow in Fract ured Porous Media\nby Xiaozhe Hu (Tufts University) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nMixed-dim ensional partial differential equations arise in many physical application s including flow in fractured porous media\, where the fractures and their intersections form a hierarchy of lower-dimensional submanifolds. An esse ntial component\, and usually the most time-consuming part of simulating P DEs\, is solving the large-scale and ill-conditioned linear systems of equ ations arising from discretizations. In this work\, we generalize the trad itional framework of designing preconditioners for the saddle point system s and develop effective preconditioners that are robust with respect to th e physical and discretization parameters for mixed-dimensional models for flow in fractured porous media. Preliminary numerical experiments are pres ented to support the theory and demonstrate the robustness of our precondi tioners. This is joint work with Wietse Boon (KTH) and Ana Budisa (Simula )\n\nMeeting ID: 970 1588 0121\nPasscode: 614469\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Giordano Tierra (University of North Texas) DTSTART:20200902T150000Z DTEND:20200902T160000Z DTSTAMP:20260404T094752Z UID:GSMMA/14 DESCRIPTION:Title: Energy-stable numerical schemes for fluid vesicles with internal nem atic order\nby Giordano Tierra (University of North Texas) as part of Global Seminar on Mathematical Modeling and Applications\n\n\nAbstract\nMo dels of flows containing vesicles membranes with liquid crystalline phases have been widely studied in recent times due to its connection with biolo gical applications.\n\nDuring the seminar I will present the main ideas to derive a new model to represent the interaction between flows and vesicle membranes with internal nematic order and preferential orientation of the ir molecules in the membrane. In fact\, the dynamics of this system is det ermined by the dissipation of an energy that regulates the competition bet ween different effects\, through the kinetic\, bending\, elastic and ancho ring energies.\n\nMoreover\, I will introduce a new unconditionally energy -stable numerical scheme to approximate the model\, and I will present sev eral numerical results in order to show the well behavior of the proposed scheme and the dynamics of this type of vesicle membranes.\n\nThis contrib ution is based on joint work with Francisco Guill ́en-Gonzal ́ez (Univer sidad de Sevilla\,\nSpain) and Mar ́ıa Angeles Rodr ́ıguez-Bellido (Un iversidad de Sevilla\, Spain).\n\nZoom Meeting ID: 970 1588 0121\nPasscode : 781507\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Francesco De Anna (Universität Würzburg) DTSTART:20201111T160000Z DTEND:20201111T170000Z DTSTAMP:20260404T094752Z UID:GSMMA/15 DESCRIPTION:Title: On classical solutions for some Oldroyd-B model of viscoelastic flui ds\nby Francesco De Anna (Universität Würzburg) as part of Global Se minar on Mathematical Modeling and Applications\n\n\nAbstract\nThis talk i s devoted to the analysis of an Oldroyd-B system of PDEs which models the evolution of certain viscoelastic fluids. A particular emphasis is spent o n the so called "corotational" model. We are interested in the well-posedn ess theory of classical solutions. We show in a bidimensional setting that \, without any restriction on the initial data\, the solutions exist globa lly in time and they are unique.\n\nThis result is due to the particular s tructure of the system which allows to propagate high regularities of the solutions\, in particular a Lipschitz regularity of the velocity field. A specific toolbox of Fourier Analysis is presented to address the mentioned result.\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Navid Mohammad Mirzaei (University of Massachusetts Amherst) DTSTART:20201202T160000Z DTEND:20201202T170000Z DTSTAMP:20260404T094752Z UID:GSMMA/16 DESCRIPTION:Title: Simple model of atherosclerosis in cylindrical arteries: impact of a nisotropic growth on Glagov remodeling\nby Navid Mohammad Mirzaei (Uni versity of Massachusetts Amherst) as part of Global Seminar on Mathematica l Modeling and Applications\n\n\nAbstract\nIn 1987\, Seymour Glagov observ ed that arteries went through a two-stage remodeling process as a result o f plaque growth: first\, a compensatory phase where the lumen area remains approximately constant and second\, an encroachment phase where the lumen area decreases over time. In this paper we investigate the effect of grow th anisotropy on Glagov remodeling in five different cases: pure radial\, pure circumferential\, pure axial\, isotropic and general anisotropic grow th where the elements of the growth tensor are chosen to minimize the tota l energy. 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 case we explore their specific effect on the Glagov curves. For the l atter two cases we also provide the changes in collagen fiber orientation and length in the intimate\, media and adventitia. In addition\, we compar e the total energy produced by growth in radial\, circumferential and axia l direction and deduce that using a radially dominant anisotropic growth l eads to lower strain energy than isotropic growth.\n LOCATION:https://stable.researchseminars.org/talk/GSMMA/16/ END:VEVENT END:VCALENDAR