Wykłady i seminaria

Instytutowe Seminarium Mechaniki im. W. Olszaka i A. Sawczuka

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2023-03-27	11:00, Sala zdalnie Prof. Roeland Merks Mathematical Institute and Institute of Biology, Leiden University, The Netherlands *Computational modeling of cell-extracellular matrix interactions during blood vessel formation* To form the patterns and behaviors that we observe during blood vessel formation, cells must carefully coordinate their behavior through biophysical and biochemical cues. My team analyzes single cell behavior and multicellular development using a combination of mathematical, computational and experimental approaches. I will present a series of our recent computational results, which are based on the cellular Potts model and additional models to represent the mechanics of the ECM, including molecular-dynamics and finite-element approaches. We use these to simulate how properties of how cross-talk between the extracellular matrix (ECM) and the forces exerted by cells can determine cell shape and cell migration. After introducing single cell-behavior model, I will move on to extend these insights to the analysis of mechanical cell-cell communication, giving rise to mechanically-regulated collective cell behavior and morphogenesis. I will first discuss a series of models used to analyze the effect of extracellular matrix stiffness on cell shape, cellular force transduction in fibrous ECMs , and models of anisotropic force generation. Recent versions of our cell-ECM interaction models focus on how our descriptions of focal adhesions, the mechanosensitive ‘feet’ of cells by which they hold on the extracellular matrix, must be improved to analyze mechanical cell-ECM interactions in fibrous matrices. Also we invest in computational improvements to advance towards more detailed multicellular models. Time permitting, I will also discuss our recent work on Delta-Notch signaling, a key cell-cell signaling pathway that is active during angiogensis. Altogether, I will present the use computational approaches for analyzing how local cell-microenvironment interactions coordinate cell behavior during multicellular patterning. Uwagi: The seminar will be held online via gotomeeting program under the link: https://global.gotomeeting.com/join/810943621
2023-03-20	Prof. Bernold Fiedler Institute of Mathematics, Free University of Berlin *Reaction and diffusion in one to three space dimensions – an invitation* We consider the qualitative dynamics of reaction-diffusion systems like u_t = D ∆u + f(u) in one, two and three space dimensions. Examples include convective fluids, surface catalysis, heart tissue, and the Belousov-Zhabotinsky medium. Rotating spiral wave patterns are a characteristic feature of planar excitable media systems. Scroll waves are three-dimensional stacks of rotating spirals, with tips aligned along filament curves. Elementary singularity theory, properly applied, provides a framework to systematically understand • nodal properties, in one spatial dimension • spiral wave annihilation, in two dimensions, and • crossover collisions of scroll wave filaments, in 3d. The latter is the only generic possibility for 3d scroll wave filaments to change their topological knot or linking type. For old numerical simulations, joint work with Rolf Mantel, see www.mathematik.uni-bielefeld.de/documenta/vol-05/21.html Experimental confirmation has been obtained by Marcus Hauser (University of Magdeburg). Uwagi: The seminar will be held online via gotomeeting program under the link: https://global.gotomeeting.com/join/810943621
2023-03-13	Prof. Piotr Biler University of Wroclaw *Barenblatt profiles for a nonlocal porous medium equation* A degenerate nonlinear nonlocal evolution equation is considered; it can be understood as a porous medium equation whose pressure law is nonlinear and nonlocal. We show the existence of sign changing weak solutions to the corresponding Cauchy problem. Moreover, we construct explicit compactly supported self-similar solutions which generalize Barenblatt profiles - the well-known solutions of the classical porous medium equation. Uwagi: The seminar will be held online via gotomeeting program under the link: https://global.gotomeeting.com/join/810943621
2023-03-06	Prof. Tadeusz Wibig Department of Physics, University of Lodz *CREDO-Maze Project. Extensive system of local EAS mini-arrays* The CREDO-Maze project was developed at the University of Łódź to extend the CREDO Program with a system of local, school-based mini-arrays for small EAS registration. We designed minimal detector systems for monitoring cosmic ray showers, with minimization focused on construction costs. The idea is that such ready-made detector stations are to be lent to the schools concerned, which will commit to keeping them in good shape and regularly uploading data to the CREDO-Maze Project's central server, eventually to the CREDO database. Several of them are currently in operation at high schools in Lodz.
2023-02-27	Prof. PŚl Robert Andrzej Michnik Silesian Technical University, Faculty of Biomedical Engineering *Application of modeling and experimental research of the musculoskeletal system in diagnostics and physioprophylaxis* During the lecture, biomechanical methods to assess the functioning of the musculoskeletal system in various aspects of human physical activity will be presented. In particular, the following will be presented: 1. biomechanical measurement techniques such as: motion analysis, measurements of external forces acting on the human body, measurements of muscle activity using the EMG method. 2. methods of computer modeling of musculoskeletal system loads enabling non-invasive determination of forces acting on joint surfaces and forces generated by individual muscles. The second part of the lecture will discuss the possibilities of using biomechanical research to support the diagnosis and monitoring of therapy of patients with cerebral palsy and the results of multi-variant simulations of numerical loads operating within the lumbar spine in order to develop assumptions for physioprophylactic and physiotherapeutic programs. Uwagi: The seminar will be held online via gotomeeting program under the link: https://global.gotomeeting.com/join/810943621
2023-02-20	Prof. dr Angela Stevens University of Münster, Institut für Analysis und Numerik *Mathematical Models for the Regeneration of Flatworms* Planarians are flatworms which possess the ability to regenerate after rather severe injuries to their body. Even very small tissue parts cut from the flatworm can regenerate to a fully functioning and intact organism, similar to the phenomena seen in hydra. Based on experimental data, a system of reaction-diffusion equations for the regeneration of planarian flatworms is discussed. This system correctly reproduces typical cut and graft experiments. Uwagi: The seminar will be held online via gotomeeting program under the link: https://global.gotomeeting.com/join/810943621
2023-02-13	Dr Federico Guglielmo Morelli Laboratoire de Physique Theorique de la Matiere Condensee,Sorbonne Universite, Paris, France *Crises propagation and behavioural effects in multi agents self-reflexive real business cycle models* The Global Financial Crisis of 2008 left was also a crisis for macroeconomic models. On the one hand, orthodox economists persist in using the skeleton of classical models, while on the other hand, various groups of heterodoxes have proposed different ways to change the foundations of Economics. Our research aims to bridge the gap between Neo-classical Economics and complexity Economics using methods and techniques from statistical physics. Beginning with standard economic models, we study the addition of a self-reflexive feedback impacting the confidence of individual economic agents. This induces large output swings despite only minor variations in economic conditions. Within this framework, economic crises propagate endogenously and are amplified by interactions. Later on, we enrich the previous framework by taking into account heterogeneities, studying how economic recessions propagate through the different strata of society. Uwagi: The seminar will be held online via gotomeeting program under the link:https://global.gotomeeting.com/join/810943621
2023-02-06	Prof. Ryszard Rudnicki Institute of Mathematics of Polish Academy of Sciences *Ergodic and chaotic behaviour of some partial differential equations and applications to some biological models.* We present a brief introduction to the mathematical theory of chaotic systems. We focus mainly on the ergodic approach. The main idea is to show that the semiflow has an invariant mixing measure positive on open sets. From this it follows that every trajectory is unstable, there are trajectories whose closure is the whole space and trajectories are turbulent in the sense of Bass. Then we consider flows generated by semilinear partial differential equations of the first order. Such equations generate semiflows on some spaces of functions. Using measures defined by stochastic processes or by random fields, we construct ergodic measures invariant with respect to semiflows generated by PDEs. Next we present three cell population models which lead to chaotic systems. The first one describes the evolution of the spatial distribution of a population developing from a single source. The second model characterises the uncontrolled evolution of the maturity of blood cell precursors cells. The last one is a classical size structured model given by a partial differential equation with a non-local division term. It should be noted that most of the recent papers on chaos for semigroups of operators are based on the study of the spectral properties of their infinitesimal generators. This approach seems to be easier than ours, but our approach reveals why these semiflows are chaotic. The second advantage of the approach based on ergodic theory is that we can prove much stronger results on chaos. Uwagi: The seminar will be held online via gotomeeting program under the link: https://global.gotomeeting.com/join/810943621
2023-01-30	Prof. Adelia Sequeira Department of Mathematics and CEMAT, Instituto Superior Tecnico, University of Lisbon, Lisbon, Portugal () *Cardiovascular Modeling and Simulations. A Mathematical Challenge* Mathematical modeling and simulations of the human circulatory system is a challenging and complex wide-range multidisciplinary research field that has seen a tremendous growth in the last few years. This field, with a strong socio-economic impact in the cost and overall status of healthcare, is rapidly progressing, motivated by the fact that cardiovascular diseases are a major cause of death in developed countries. In this talk we will consider some mathematical models and simulations of the cardiovascular system and comment on their significance to yield realistic and accurate numerical results, using stable, reliable and efficient computational methods. Results on the simulation of some image-based patient-specific clinical cases will also be presented. References: [1] A. Fasano and A. Sequeira, Hemomath - The Mathematics of Blood, MS&A Modeling, Simulation and Applications, vol. 18, Springer, 2017. [2] L. Formaggia, A. Quarteroni, A. Veneziani (Eds.), Cardiovascular Mathematics: Modeling and simulation of the circulatory system, MS&A - Modeling, Simulation and Applications, vol. 1, Springer, 2009. Uwagi: The seminar will be held online via gotomeeting program under the link: https://global.gotomeeting.com/join/810943621
2023-01-23	Prof. Roman Srzednicki Jagiellonian University, Cracow *On applications of topology in the theory of differential equations* We present an overview of selected applicatons of topology in the qualitative theory of ordinary differential equations, including the Ważewski retract method, the Conley index, and the Brouwer degree. Uwagi: The seminar will be held online via gotomeeting program. The access will be activated at 10:40 under the link: https://global.gotomeeting.com/join/810943621
2023-01-09	Prof. Jan Sokołowski Systems Research Institute, Polish Academy of Sciences (IBSPAN) *Geometric aspects of shape optimization* Review of known results in shape optimization from the point of view of Geometrical Analysis is presented [1]. This presentation is devoted to the mathematical aspects of the shape optimization theory. We focus on the theory of gradient flows of objective functions and their regularization. Shape optimization is a part of calculus of variations which uses the geometry. Shape optimization is also related to the free boundary problems in the theory of Partial Differential Equations. We consider smooth perturbations of geometrical domains in order to develop the shape calculus for the analysis of shape optimization problems. There are many applications of such a framework, in solid and fluid mechanics as well as in the solution of inverse problems. For the sake of simplicity we consider model problems, in principle in two spatial dimensions. However, the methods presented are used as well in three spatial dimensions. We present a result on the convergence of the shape gradient method for a model problem. To our best knowledge it is the first result of convergence in shape optimization. The complete proofs of some results are presented in [2]. 1. P.I. Plotnikov, J. Sokołowski, Geometric aspects of shape optimization, J. Geometrical Analysis, invited review paper in the special issue on Shape Optimization. 2. P.I. Plotnikov, J. Sokołowski, Gradient flow for Kohn-Vogelius functional, HAL preprint Uwagi: The seminar will be held IN PERSON in the INSTITUTE AULA.
2022-12-12	Prof. Andrzej Dragan Institute of Theoretical Physics, University of Warsaw *Quantum theory vs black holes* I will explain basics of quantum theory and discuss what happens to it, when strong gravity of black holes is involved. Uwagi: The seminar will be held IN PERSON in the INSTITUTE AULA.
2022-12-05	Prof. Maciej Paszyński AGH University of Science and Technology, Krakow, Poland *Application of neural networks to support challenging computer simulations* This talk will explain how, in three related different ways, it is possible to apply neural networks to support challenging computer simulations of difficult problems that require special stabilization efforts. First, we will discuss an example of such a problem, namely, the advection-dominated diffusion ( see, e.g., Section 5.1 in [1] or Section 4.2 in [2]). We will discuss why this problem is difficult to solve using the standard Galerkin method and finite element analysis. We will explain what it means to stabilize the problem, and we will show how the residual minimization method [1,2] allows for obtaining a correct numerical solution. With this example in mind, we will introduce the Physics Informed Neural Network (PINN) method and its generalization, the Variational Physics Informed Neural Network (VPINN) method, introduced in 2019 by George Karniadakis [3,4]. We will show that PINN and VPINN fail when applied to difficult unstable problems, like the advection-dominated diffusion.I will also present that it is possible to transfer the knowledge from the theory of the classical finite element method to PINN/VPINN world in order to "stabilize" the PINN/VPINN solvers and obtain the correct numerical solution. We will also show that the residual minimization method is equivalent to the Petrov-Galerkin formulation with the optimal test functions. Then, we will explain how neural networks can learn the coefficients of the optimal test functions. By using the optimal test functions as provided by the neural networks, we obtain the stabilization of the difficult computational problems practically for free (in a linear computational cost). Finally, we will show that it is possible to train the neural network the optimal hp refinements of the computational mesh. The neural network once trained the optimal refinements for a given class of problems it, can guide the refinements further without using expensive solvers [5,6]. We will also discuss the differences between the finite element method supported by neural networks and PINN/VPINN [1] https://apps.dtic.mil/sti/pdfs/ADA587495.pdf [2] https://www.sciencedirect.com/science/article/pii/S0045782520303996 [3] https://arxiv.org/abs/2209.05844 [4] https://link.springer.com/chapter/10.1007/978-3-030-77961-0_11 [5] https://www.sciencedirect.com/science/article/pii/S0021999118307125 [6] https://arxiv.org/abs/1912.00873 [7] https://arxiv.org/abs/2201.00904 Uwagi: The seminar will be held IN PERSON in the INSTITUTE AULA.
2022-11-28	Prof. Wladyslaw Mielczarski Institute of Electric Power Engineering, Lodz University of Technology *Energy Transition* The European energy and climate policy aims to reduce greenhouse gas emissions by introducing the Green Deal as an economy with neutral CO2 emissions. They target electricity supply systems, transportation, operation of industry and ways of public living. The operation is called Energy Transition and embraces all member states by imposing legal regulations on fuels and energy. The presentation is focused on the power supply systems as one of the largest greenhouse gas emitters. The climate policy sets targets for 2030 to reduce CO2 emissions by 55%, achieve 32% shares of renewables in energy production, and improve energy efficiency by 32,5%. However, the climate targets are very ambitious and expensive. So the EU directs billions of Euros to support the climate policy. Nevertheless, emissions reduction does not only depend on legal regulations, and financial support as energy plants operate under the laws of physics, which seems to be the most significant barrier for politically based decisions. The main idea of reducing CO2 emissions in the power supply industry was to replace fossil fuel power stations with renewable energy sources (RES), particularly coal power stations. However, the RES can operate for a limited time during the year. For example, PV panels can produce electricity with instaled nominal power only for 1000 hours per year in Central Europe. On the other hand, on-shore wind plants operate for 2300 hours, off-shore windmills in the Baltic Sea for about 3500 hours per year, while the year counts for 8760 hours and requires a continuous electricity supply. Societies and economies demand more electrical energy every year as the most advanced technologies, such as eMobility, IT technologies, heat pumps, and others, require a robust supply of electrical energy. On the other hand, electricity has specific features: the demand and supply should be balanced each second as electricity stores do not exist because electrical energy is a movement of electrons, and no movement can be stored. Instead, energy can be stored as chemical or mechanical energy in a limited volume and time. Security of power supply requires the operation of dispatchable power plants which can generate electricity in any weather condition, as “lights must be on 24 hours a day and seven days a week”. Unfortunately, only three available technologies are dispatchable at any time: coal power stations, natural gas plants and nuclear installations. The use of coal should be banned as it emits a large amount of carbon dioxide. Coal was to be replaced by natural gas, at least as a transitional fuel; however, the war in Ukraine verified the idea of replacing coal with natural gas. Nuclear technologies are expensive and dangerous, and some European countries, such as Germany and Austria, have reservations about nuclear power plants. The crucial question that should be addressed is: how to ensure a continuous and robust electrical energy supply to societies and economies reaching the Energy Transition targets aiming at emission-neutrality. Uwagi: The seminar will be held online via gotomeeting program. The access will be activated at 10:40 under the link: https://global.gotomeeting.com/join/810943621
2022-11-21	Prof. Erdogan Madenci Department of Aerospace and Mechanical Engineering, University of Arizona, USA *Peridynamics for domain agnostic analysis* Peridynamics (PD) gained approval in the solid mechanics community since its inception in 2000. It was originally introduced for modeling of progressive failure in materials and structures. It permits long-range interactions occurring over a finite domain which makes it a nonlocal continuum theory. It enables differentiation through integration, removes mathematical singularities, restores nonlocal interactions, introduces an internal length parameter, links different length scales and enables damage initiation and growth at multiple sites. The governing equations of PD are integro-differential in nature and do not require the smoothness of field variables. Over the past 20 years, a considerable number of research articles have been published on PD. The success in accurately predicting crack propagation in various materials and for a large range of space, time, and loading scales, has established PD as an effective tool for engineers and scientists. The purpose of this presentation is to share recent applications concerning multi-physics modeling, multi-scale modeling, material failure, data recovery, data manipulation and model discovery from large data. Uwagi: The seminar will be held online via gotomeeting program. The access will be activated at 10:40 under the link: https://global.gotomeeting.com/join/810943621
2022-11-14	MSc Eng Anna Mackojć Faculty of Automotive and Construction Machinery, Warsaw University of Technology / Fathom Group, UK *Analytical approach to modelling, analysis and dynamics studies on parametrically induced payload pendulation during offshore lifting operations* The subject of research outlines a relevant maritime problem regarding offshore lifting operations. One of the challenges during offshore lifts is the need to deal with the surrounding environment, which under unfavourable conditions can significantly reduce the operating window or increase the risk of an operational failure, which at best may result in damage to the lifted payload, deck crane or ship structure. The worst case scenario is an accident involving the ship's crew assisting in the operation. Due to increasing exploitation of either renewable (offshore wind farms) or underwater hydrocarbon energy resources, the intensification of offshore activities becomes more and more obvious and vessel crane operations are the basis of offshore installations. To assist the industry, engineers have developed several technologies and operational practices, however, access to appropriate modelling methods and methodologies is still significantly limited. In order to support the industry in a better understanding of the complexity of problems undertaken and provide fit-to-purpose solutions, the author proposed a novel approach to modelling offshore lifting operations. The concept of the model and extensive studies on its dynamics on regular and irregular waves are published in the article "Proposal of 3DoF model as an approach to modelling offshore lifting dynamics" in Ocean Engineering (2020). Further research allowed to propose an extended model (payload-vessel) with 5 degrees of freedom, which enables the analysis of operations in a wide spectrum of payload masses ("Preliminary modelling methodology of a coupled payload-vessel system for offshore lifts of light and heavyweight objects", Bulletin of Polish Academy of Science, Technical Sciences, 2021). One of the most important scientific achievements was development of the analytical solution for the payload dynamic response under conditions of parametric excitation on regular waves. The analytical solution was obtained based on perturbative methods - the method of multiple time scales. This solution was confirmed with the solution resulting from the numerical integration of the equation of motion, and its convergence was assessed as very good. The proposed approach allows to determine the working conditions - regions of dynamic instability. Moreover, it enables a description of dynamics of the lifting process and the lifted object response in an analytical form due to explicit physical dependencies. Another benefit is seen in reducing the computationally expensive design process and in the possibility of an efficient recognition of a potentially problematic scenario at early conceptual stages in order to plan an optimal lifting operation. A detailed analysis is available in Ocean Engineering journal, in the article, “Analytical solution of parametrically induced payload nonlinear pendulation in offshore lifting” (2022). Uwagi: he seminar will be held online via gotomeeting program. The access will be activated at 10:40 under the link: https://global.gotomeeting.com/join/810943621
2022-11-07	Prof. Takeharu Yoshii Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Japan *Advanced temperature-programmed desorption as a new characterization method for heteroatoms* Temperature-programmed desorption (TPD) has been popularly used for the analysis of inorganic catalysts and carbon materials. In conventional TPD, a sample is heated to typically around 1000C at a fixed heating rate and the desorbed gases are detected for chemical identification as a function of temperature. For example, when TPD is applied to carbon materials, oxygen-functional groups which exist at carbon edge sites can be quantified. However, it has not been developed as a quantitative method for an effective determination of the nitrogen (N) species, mainly due to the higher thermal stability of N in carbon materials than oxygen. Recently, we extended the maximum TPD temperature up to 2100C, realizing the complete determination of N species in carbon materials. Combined with the results of XPS and DFT calculations, we found that the gas emission patterns of NH3, HCN, and N2 obtained by TPD can provide quantitative and qualitative information on the different types of N species including pyrrolic N, pyridinic N, and graphitic N. These results demonstrate that high-temperature TPD analysis is a promising new method for analysis of N species in carbon materials. The presentation will further discuss the potential of high-temperature TPD, including its extension to other heteroatoms and its application to non-carbon materials such as oxides.
2022-10-24	Prof. Tomasz Lipniacki Instytut Podstawowych Problemow Techniki PAN *Dissecting innate immunity responses to viral infection at the single-cell level* Recognition of viral RNA initiates a signaling cascade culminating in synthesis of interferons (IFNs). Secreted IFNs, by activation of transcription factors of STAT family in surrounding cells, prompt them to prepare for viral infection. Viruses, in turn, convey non-structural proteins to impede the innate immune response. Based on results obtained using single-cell techniques, we proposed an agent (single cell)-based, stochastic, computational model and used it to explain how a infected population of cells can stratify into distinct subpopulations. The winning cells, in response to viral RNA, produce IFNβ (warning yet not infected cells), loosing cells express viral proteins that inhibit innate immune signaling. The proposed model reproduces the experimentally observed complex spatial patterns of respiratory syncytial virus (RSV) spread and dichotomous cell responses Coauthors: Frederic Grabowski, Marek Kochańczyk, Maciej Czerkies, Zbigniew Korwek, Wiktor Prus. This research is funded by the Norwegian Financial Mechanism GRIEG-1 (grant 2019/34/H/NZ6/00699, operated by the National Science Centre, Poland) Uwagi: he seminar will be held online via gotomeeting program. The access will be activated at 10:40 under the link: https://global.gotomeeting.com/join/810943621 Video z seminarium
2022-10-17	Prof. Masoud Tahani Ferdowsi University of Mashhad, IPPT PAN *Mechanical design of orthopedic internal and external implants for the fracture fixation of lower extremities considering bone healing process* Diaphyseal bone fracture is a common orthopedic problem, which may stem from deteriorative effects of aging or other comorbidities, lack of enough nutrition, genetic disorders, traumatic injuries, or progressive damage accumulation. To mechanically stabilize and anatomically align the mobile fragments of a broken bone, a functional reduction and a stable fixation must be employed. Several plating systems have been developed and improved to enhance the healing outcome and reduce the associated complications to date. The performance of the locking compression plate (LCP) is a multifactorial function. The control parameters of plating, such as geometries, material properties, and physical constraints of the LCP components, affect basic functions associated with bone fixation, including the extent of stress shielding and subsequent bone remodeling, strength and stability of the bone-LCP construct, and performance of secondary bone healing. The appropriate values of design parameters of an LCP construct also a unilateral-uniplanar external fixator to achieve the optimized performance throughout bone healing will be discussed. Uwagi: The access will be activated at 10:40 under the link: https://global.gotomeeting.com/join/810943621
2022-10-10	Professor Paolo Colombo - Dept. of Industrial Engineering, University of Padova, Italy Institute Seminar of Mechanics *Additive Manufacturing of Ceramics using Preceramic Polymers* Preceramic polymers are precursors for ceramic phases of different compositions. They convert into nano-structured ceramic materials in the system Si(X)OCN (with X = Al, Ti, Zr, etc.), also called PDCs or Polymer-Derived-Ceramics, by high temperature pyrolysis. The resulting materials can have useful structural and functional properties. This talk will discuss the fabrication of (mainly) porous structures starting from pure preceramic polymers (e.g. silicone resins) or silicone resins plus reactive fillers to produce advanced silicate ceramic phases, including bioceramics, suitable for different potential applicationsand Ceramic Matrix Composites. Different types of additive 3D manufacturing techniques were employed, in particular: a) stereolithography(DLP); b) 2 Photon Polymerization fabrication (TPP); c) volumetric additive manufacturing; d) ink extrusion (DIW); e) fused deposition (FDM); f) powder bedbinder jetting(BJ)plus hybrid technologies such DIW+UV or DLP+TPP. Advantages and disadvantages of the different processing techniques employed, in relation to the use of preceramic polymers, will be discussed, and examples of produced and characterized structures for potential use in different applications will be presented. Uwagi: The seminar will be held online via gotomeeting program. The access will be activated at 10:40 under the link: https://global.gotomeeting.com/join/810943621
2022-10-03	Professor Francois Hamel I2M INSTITUT DE MATHEMATIQUES DE MARSEILLE, Aix-Marseille Universite *Spreading speeds and one-dimensional symmetry for reaction-diffusion equations in R^N* The talk will focus on the large-time dynamics of bounded solutions of reaction-diffusion equations in R^N with unbounded initial support. I will discuss the existence of spreading sets and Freidlin-Gartner formulas for the spreading speeds of the solutions in any direction, in connection with the existence of planar traveling waves. I will also explain some results on the asymptotic one-dimensional symmetry of the elements of the omega-limit set of the solutions, in the spirit of a famous De Giorgi conjecture on solutions of some elliptic equations in R^N. The talk is based on joint works with Luca Rossi. Uwagi: The seminar will be held online via gotomeeting program. The access will be activated at 10:40 under the link: https://global.gotomeeting.com/join/810943621