Soft Matter and Complex Systems Seminar
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2022-03-11 (Friday)
join us at 09:30 
John Shaw (University of Arkansas, IFT UW)Two necessary conditions for the stability of simple loops
Many self-formed flow networks in nature are loopy, and these loops can occur because of adaptation to fluctuating boundary conditions. However, this control has not been thoroughly tested at the scale of a single loop. We explore two conditions that control loop formation in a three-node equilateral network. First, we find that the location of the absolute maximum discharge to the network must change for a loop to form. Second, if there is a super-linear relationship between link conductivity and discharge, then there is a limit to how unequal link conductivities can be. This preliminary work suggests that the switching of dominant nodes, and parity of link conductivites should be hallmarks of stable loops in nature.
The seminar will be held on Zoom
https://us02web.zoom.us/j/82784273907
The seminar will be held on Zoom
https://us02web.zoom.us/j/82784273907
2022-01-28 (Friday)
join us at 09:30
Małgorzata Domańska, Kamil Gmiterek, Malek Harb, Zlatica Kalužná, Jan Kołodziejczyk, Marcin Pruszczyk (IFT UW)Student talks
On Friday 28 January 2022 at 9:30 AM we are hosting the final seminar of this term, during which we will hear short presentations by:
Małgorzata Domańska
Flash introduction to Magnetorheology
Magnetic Soft Matter is a quickly evolving discipline with fundamental and experimental interest. This is due to the fact that its physical properties can be easily controlled through external magnetic fields. In this flash talk I would like to present a short introduction to this kind of materials and their properties. My talk will be based on publication:
Morillas, J. R., & de Vicente, J. (2020). Magnetorheology: a review. Soft Matter, 16(42), 9614–9642. [doi:10.1039/d0sm01082k]
Kamil Gmiterek
Weak solutions of Euler equations in 2D
The global existence of classical solutions of Euler equations for sufficiently smooth initial data was proven by Wolibner. In 2D case (where vorticity can be treated as a scalar) Yudovich provided the global (in time) existence and uniqueness of weak solutions for initial data having bounded vorticity.
Malek Harb
Epileptic seizures
Epileptic seizures: signs, causes, mechanisms. The simulation of these seizures in the NEURON simulation environment (simulation of Local Field Potentials).
Zlatica Kalužná
Molecular memristors
Growing demand for new devices is rapidly changing every day’s world with pressure for smaller and more effective circuit components. Low cost, long lifetime and outstanding performance properties are common in search for such devices. Miniaturization and combining several devices in one are solutions for our current needs. Molecular electronics offers a solution by miniaturization of devices into molecular scale.
Jan Kołodziejczyk
Stability and electronic structure of functionalized 2D molybdenum nitrides MXenes
MXenes are a relatively new family of low dimensional materials, which has been gaining more and more popularity in recent years. In this study ab initio DFT calculations are employed to determine the electronic structure and stability of bare and functionalized (with fluorine and oxygen atoms) two-dimensional molybdenum nitride from the MXene family. It occurs that functionalization has a significant impact on properties of these compounds, opening the band gap and leading to the emergence of semiconductivity.
Marcin Pruszczyk
Continuum mechanics of epithelial monolayers and bilayers
To investigate the mechanics of deformed biological tissues, one may ask for continuum theory, i.e. a continuous description of energy in terms of variables well-defined for a system, in which the tissues are treated as continuous entities. It is far from obvious whether linear elastic theory is sufficient for describing biological tissues. We derive the continuum theories from simple microscopic models of cellular interactions and look into the "devil in the detail", i.e. the dependence of the continuum theories on the details of the underlying microscopic models.
The seminar will be held on Zoom
https://us02web.zoom.us/j/82784273907
Małgorzata Domańska
Flash introduction to Magnetorheology
Magnetic Soft Matter is a quickly evolving discipline with fundamental and experimental interest. This is due to the fact that its physical properties can be easily controlled through external magnetic fields. In this flash talk I would like to present a short introduction to this kind of materials and their properties. My talk will be based on publication:
Morillas, J. R., & de Vicente, J. (2020). Magnetorheology: a review. Soft Matter, 16(42), 9614–9642. [doi:10.1039/d0sm01082k]
Kamil Gmiterek
Weak solutions of Euler equations in 2D
The global existence of classical solutions of Euler equations for sufficiently smooth initial data was proven by Wolibner. In 2D case (where vorticity can be treated as a scalar) Yudovich provided the global (in time) existence and uniqueness of weak solutions for initial data having bounded vorticity.
Malek Harb
Epileptic seizures
Epileptic seizures: signs, causes, mechanisms. The simulation of these seizures in the NEURON simulation environment (simulation of Local Field Potentials).
Zlatica Kalužná
Molecular memristors
Growing demand for new devices is rapidly changing every day’s world with pressure for smaller and more effective circuit components. Low cost, long lifetime and outstanding performance properties are common in search for such devices. Miniaturization and combining several devices in one are solutions for our current needs. Molecular electronics offers a solution by miniaturization of devices into molecular scale.
Jan Kołodziejczyk
Stability and electronic structure of functionalized 2D molybdenum nitrides MXenes
MXenes are a relatively new family of low dimensional materials, which has been gaining more and more popularity in recent years. In this study ab initio DFT calculations are employed to determine the electronic structure and stability of bare and functionalized (with fluorine and oxygen atoms) two-dimensional molybdenum nitride from the MXene family. It occurs that functionalization has a significant impact on properties of these compounds, opening the band gap and leading to the emergence of semiconductivity.
Marcin Pruszczyk
Continuum mechanics of epithelial monolayers and bilayers
To investigate the mechanics of deformed biological tissues, one may ask for continuum theory, i.e. a continuous description of energy in terms of variables well-defined for a system, in which the tissues are treated as continuous entities. It is far from obvious whether linear elastic theory is sufficient for describing biological tissues. We derive the continuum theories from simple microscopic models of cellular interactions and look into the "devil in the detail", i.e. the dependence of the continuum theories on the details of the underlying microscopic models.
The seminar will be held on Zoom
https://us02web.zoom.us/j/82784273907
2022-01-21 (Friday)
join us at 09:30
Jeffrey Everts (IChF PAN)Manipulating ionic charges by flexing and melting orientational order
The control and manipulation of electrical charge is of paramount importance for a wide variety of scientific disciplines. In this talk I address how ionic charge control can be achieved by using the orientational, i.e., liquid crystalline, order of materials. Liquid crystalline order occurs in many types of materials, which range from molecular to colloidal building blocks and (bio)polymers. Together with their possible applicability in energy storage, material science, device physics, microelectronics, and biology, it shows that the confluence of electrostatics with orientational order can lead to many interesting phenomena for a wide variety of systems. Specifically, we will demonstrate the manipulation of ionic charges by discussing anisotropic screening of charged colloid particles dispersed in nematic solvents, surface charge control mediated by liquid-crystal topological defects, and finally, the charging of point and line defects in nematic liquid crystals.
The seminar will be held on Zoom:
https://us02web.zoom.us/j/82784273907
The seminar will be held on Zoom:
https://us02web.zoom.us/j/82784273907
2022-01-14 (Friday)
room 1.40, Pasteura 5 at 09:30
Magdalena Załuska-Kotur (Institute of Physics, Polish Academy of Sciences)Step bunches, nanowires and other vicinal “creatures” resulting from surface dynamics
Different patterns are created on the surface of the growing crystals, among which the step bunches and/or step meanders are of most studied. The Ehrlich-Schwoebel effect on surface steps is considered to be one of the “usual suspects” of such patterning. A direct step barrier means it is easier to attach a particle to the step from the lower terrace than from the upper terrace. In the process of crystal growth it leads to the formation of meanders, while an inverse barrier leads to the step bunching. I will show that the cellular automata model can be used to study surface patterning process. The proper combination of a direct and inverse step barrier and the correct selection of the potential of the well between them lead to the formation of bunched step structures, followed by the formation of anti-bands, and then changes in the height of the direct step barrier lead to the growth of nanocolumns, nanowires, and nanopyramids or meanders, in the same system. The universality of surface dynamics will be further explored by differential equations describing the evolution of the surface slope. The time scaling of the bunching process resulting from these equations is further compared with the experimental results.
2021-12-17 (Friday)
room 1.40, Pasteura 5 at 09:30
Paweł Żuk (Lancaster University, IChF PAN)Transient dynamics in outflow of energy from system in nonequilibrium stationary state
We investigate the thermal relaxation of an ideal gas in a nonequilibrium stationary state. The gas is enclosed between two walls, which initially have different temperatures. After making one of the walls adiabatic, the system returns to equilibrium. We notice two distinct modes of heat transport and associated time scales: one connected with traveling heat front and the other with internal energy diffusion. At the heat front, which moves at the speed of sound, pressure, temperature, and density change abruptly, leaving lower values behind. It is unlike shock, sound wave, or thermal wave. The front moves multiple times between the walls and is the dominant heat transport mode until surpassed by diffusion. We found that it can constitute an order 1 factor in shaping the dynamics of internal energy outflow. We found that cooling such a system is quicker than heating and that hotter bodies cool down quicker than colder ones. The latter is known as Mpemba effect.
2021-12-10 (Friday)
room 1.40, Pasteura 5 at 09:30
Antoine Sellier (LadHyX, Ecole Polytechnique, France.)Axisymmetric viscous MHD flow about a solid body of revolution translating in an unbounded or bounded conducting Newtonian liquid
The axisymmetric slow viscous MHD flow of a conducting liquid about a solid insulating body of revolution, translating parallel with bothits axis of revolution and a uniform magnetic ambient field, is considered. A new boundary formulation is proposed to efficiently calculate such a flow subject to a non-uniform Lorentz body force. The advocated procedure, also providing the force exerted on the body, is illustrated for a sphere translating either in an unbounded liquid or along the axis of a solid cylindrical no-slip tube bounding the liquid.
2021-12-03 (Friday)
room 1.40, Pasteura 5 at 09:30
Stanisław Żukowski (IFT UW)Jellyfish gastrovascular system as an example of spatial network with reconnections
Jellyfish gastrovascular system consists of channels through which seawater flows carrying nutrients and oxygen (similar to the circulatory system in our bodies). As the jellyfish grows, new channels grow from the outer rim of its umbrella and develop towards the stomach. These channels form a quasi two-dimensional network, the dynamics of which are our main focus. Usually, modeling of spatial network dynamics includes elongation of branches, their splitting (to create ramified network) and events of reconnection between branches (creating closed loops in network). The latter interests us the most as there is still a lack of a simple physical model leading to reconnections.
2021-11-26 (Friday)
room 1.40, Pasteura 5 at 09:30
Christian Liggett (University of Edinburgh, UK)Evaluation of Machine Learning Techniques Using Raw Multiphase Flow Data: Classification and Regression
An introduction into the use of Machine Learning techniques with raw pipeline data, giving examples into both Classification and Regression problems in industry. Description of models followed by an evaluation of results using two different types of industrial flow data: univariate time series and multi-input numerical data. The first project investigates time series classification to detect flow regimes from the change in liquid holdup over time. The flow regimes of multiphase flow can have huge effects on systems, the project focuses specifically on classifying Slug Flow which can cause large pressure drops as well as damage to components over time. The second project investigates sensor data from a multiphase flow meter. This data is typically fed into physical models to make decisions for the downstream processes from the extraction site. These flow models are limited in accuracy and rely on analytical solutions; this project looks to see if real data can be used to predict important parameters more accurately. Are data driven solutions better for industry? In what ways could Machine Learning help to improve other fluid systems.
2021-11-19 (Friday)
room 1.40, Pasteura 5 at 09:30
Rishabh Sharma (IFT UW)Study of geometrical measures of wormholes using 4D-tomography
In this work, we have used 4D micro-tomography (XCT) to study the dissolution channels aka wormholes. 16-bit grayscale scans of dissolving samples are obtained at constant time-interval during the dissolution experiments. The grayscale scans are segmented to binary images by a novel volume-based segmentation technique to preserve the maximum features of the wormhole. Finally, image-processing techniques such as connected-component labelling, smoothing median filters and skeletonization are used to extract the wormholes and their geometrical properties. Several measures such as tip-propagation, wastefulness and branchedness have been proposed which show a high correlation of wormhole propagation speed with rock internal structure.
2021-11-05 (Friday)
room 1.40, Pasteura 5 at 09:30
Krzysztof Mizerski (IGF PAN)Negative diffusion effects in magnetohydrodynamic turbulence induced by fluctuations of the Lorentz force
The turbulent hydro-magnetic dynamo is a process of magnetic field amplification by a chaotic flow of an electrically conducting fluid, responsible for generation of the magnetic fields of planets and stars. Here we demonstrate a curious effect of the Lorentz force, which can act to intensify the magnetic fields, counter intuitively in light of the Lenz law according to which the Lorentz force acts to retard motions and saturate the dynamo-induced magnetic field. However, the net effect of its small-scale fluctuations in a turbulent flow is far from obvious and it is shown that it can lead to amplification rather than saturation of the magnetic energy through creation of negative turbulent diffusivity.