Agnieszka Słowicka, Ph.D.

Department of Biosystems and Soft Matter (ZBiMM)
Division of Complex Fluids (PFPZ)
position: assistant professor
telephone: (+48) 22 826 12 81 ext.: 421
room: 322
e-mail: aslowick

Doctoral thesis
2008-10-30Badanie metodą dynamiki molekularnej powstawania wybranych nanostruktur w emulsjach 
supervisor -- Zbigniew Walenta, Ph.D., Dr. Habil., IPPT PAN
616
 
Recent publications
1.Farutin A., Piasecki T., Słowicka A.M., Misbah C., Wajnryb E., Ekiel-Jeżewska M.L., Dynamics of flexible fibers and vesicles in Poiseuille flow at low Reynolds number, SOFT MATTER, ISSN: 1744-683X, DOI: 10.1039/c6sm00819d, Vol.12, pp.7307-7323, 2016
Abstract:

The dynamics of flexible fibers and vesicles in unbounded planar Poiseuille flow at low Reynolds number is shown to exhibit similar basic features, when their equilibrium (moderate) aspect ratio is the same and vesicle viscosity contrast is relatively high. Tumbling, lateral migration, accumulation and shape evolution of these two types of flexible objects are analyzed numerically. The linear dependence of the accumulation position on relative bending rigidity, and other universal scalings are derived from the local shear flow approximation.

Keywords:

Poiseuille flow, Stokes equations, vesicles, flexible fibers

Affiliations:
Farutin A.-Université Grenoble Alpes (FR)
Piasecki T.-IPPT PAN
Słowicka A.M.-IPPT PAN
Misbah C.-CNRS (FR)
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
2.Jas G.S., Rentchler E.C., Słowicka A.M., Hermansen J.R., Johnson C.K., Middaugh C.R., Kuczera K., Reorientation Motion and Preferential Interactions of a Peptide in Denaturants and Osmolyte, JOURNAL OF PHYSICAL CHEMISTRY B, ISSN: 1520-6106, DOI: 10.1021/acs.jpcb.6b00028, Vol.120, pp.3089-3099, 2016
Abstract:

Fluorescence anisotropy decay measurements and all atom molecular dynamics simulations are used to characterize the orientational motion and preferential interaction of a peptide, N-acetyl-tryptophan-amide (NATA) containing two peptide bonds, in aqueous, urea, guanidinium chloride (GdmCl), and proline solution. Anisotropy decay measurements as a function of temperature and concentration showed moderate slowing of reorientations in urea and GdmCl and very strong slowing in proline solution, relative to water. These effects deviate significantly from simple proportionality of peptide tumbling time to solvent viscosity, leading to the investigation of microscopic preferential interaction behavior through molecular dynamics simulations. Examination of the interactions of denaturants and osmolyte with the peptide backbone uncovers the presence of strongest interaction with urea, intermediate with proline, and weakest with GdmCl. In contrast, the strongest preferential solvation of the peptide side chain is by the nonpolar part of the proline zwitterion, followed by urea, and GdmCl. Interestingly, the local density of urea around the side chain is higher, but the GdmCl distribution is more organized. Thus, the computed preferential solvation of the side chain by the denaturants and osmolyte can account for the trend in reorientation rates. Analysis of water structure and its dynamics uncovered underlying differences between urea, GdmCl, and proline. Urea exerted the smallest perturbation of water behavior. GdmCl had a larger effect on water, slowing kinetics and stabilizing interactions. Proline had the largest overall interactions, exhibiting a strong stabilizing effect on both water–water and water–peptide hydrogen bonds. The results for this elementary peptide system demonstrate significant differences in microscopic behavior of the examined solvent environments. For the commonly used denaturants, urea tends to form disorganized local aggregates around the peptide groups and has little influence on water, while GdmCl only forms specific interactions with the side chain and tends to destabilize water structure. The protective osmolyte proline has the strongest and most specific interactions with the tryptophan side chain, and also stabilizes both water–water and water–peptide hydrogen bonds. Our results strongly suggest protein or peptide denaturation triggered by urea occurs by direct interaction, whereas GdmCl interacts favorably with side chains and destabilizes peptide–water hydrogen bonds. The stabilization of biopolymers by an osmolyte such as proline is governed by favorable preferential interaction with the side chains and stabilization of water.

Keywords:

molecular dynamics simulations, fluorescence anisotropy, peptides, orientational motion

Affiliations:
Jas G.S.-University of Kansas (US)
Rentchler E.C.-University of Kansas (US)
Słowicka A.M.-IPPT PAN
Hermansen J.R.-Central University of the Caribbean (US)
Johnson C.K.-University of Kansas (US)
Middaugh C.R.-University of Kansas (US)
Kuczera K.-other affiliation
3.Kuei S., Słowicka A.M., Ekiel-Jeżewska M.L., Wajnryb E., Stone H.A., Dynamics and topology of a flexible chain: knots in steady shear flow, NEW JOURNAL OF PHYSICS, ISSN: 1367-2630, DOI: 10.1088/1367-2630/17/5/053009, Vol.17, pp.053009-1-15, 2015
Abstract:

We use numerical simulations of a bead–spring model chain to investigate the evolution of the conformations of long and flexible elastic fibers in a steady shear flow. In particular, for rather open initial configurations, and by varying a dimensionless elastic parameter, we identify two distinct conformational modes with different final size, shape, and orientation. Through further analysis we identify slipknots in the chain. Finally, we provide examples of initial configurations of an 'open' trefoil knot that the flow unknots and then knots again, sometimes repeating several times.

Keywords:

knots, low Reynolds number flows, multipole method

Affiliations:
Kuei S.-Princeton University (US)
Słowicka A.M.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
Stone H.A.-Princeton University (US)
4.Słowicka A., Wajnryb E., Ekiel-Jeżewska M., Dynamics of flexible fibers in shear flow, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.4931598, Vol.143, pp.124904-1-6, 2015
Abstract:

Dynamics of flexible non-Brownian fibers in shear flow at low-Reynolds-number are analyzed numerically for a wide range of the ratios A of the fiber bending force to the viscous drag force. Initially, the fibers are aligned with the flow, and later they move in the plane perpendicular to the flow vorticity. A surprisingly rich spectrum of different modes is observed when the value of A is systematically changed, with sharp transitions between coiled and straightening out modes, period-doubling bifurcations from periodic to migrating solutions, irregular dynamics, and chaos.

Keywords:

Shear flows, Chaotic dynamics, Vortex dynamics, Numerical solutions, Periodic solutions

Affiliations:
Słowicka A.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.-IPPT PAN
5.Słowicka A.M., Wajnryb E., Ekiel-Jeżewska M.L., Lateral migration of flexible fibers in Poiseuille flow between two parallel planar solid walls, EUROPEAN PHYSICAL JOURNAL E, ISSN: 1292-8941, DOI: 10.1140/epje/i2013-13031-2, Vol.36, pp.1-12, 2013
Abstract:

Dynamics of non-Brownian flexible fibers in Poiseuille flow between two parallel planar solid walls is evaluated from the Stokes equations which are solved numerically by the multipole method. Fibers migrate towards a critical distance from the wall zc, which depends significantly on the fiber length N and bending stiffness A. This effect can be used to sort fibers. Three types of accumulation are found, depending on a shear-to-bending parameter Γ. In the first type, stiff fibers deform only a little and accumulate close to the wall, where their tendency to drift away from the channel is balanced by the repulsive hydrodynamic interaction with the wall. In the second type, flexible fibers deform significantly and accumulate far from the wall. In both types, the fiber shapes at the accumulation positions are repeatable, while in the third type, they are very compact and non-repeatable. The difference between the second and third accumulation types is a special case of the difference between the regular and irregular modes for the dynamics of migrating fibers. At the regular mode, far from walls, the fiber tumbling frequency satisfies Jeffery’s expression, with the local shear rate and the aspect ratio close to N.

Keywords:

Self-organisation, Supramolecular assemblies

Affiliations:
Słowicka A.M.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
6.Słowicka A.M., Ekiel-Jeżewska M.L., Sadlej K., Wajnryb E., Dynamics of fibers in a wide microchannel, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3678852, Vol.136, pp.044904-1-8, 2012
Abstract:

Dynamics of single flexible non-Brownian fibers, tumbling in a Poiseuille flow between two parallel solid plane walls, is studied with the use of the HYDROMULTIPOLE numerical code, based on the multipole expansion of the Stokes equations, corrected for lubrication. Fibers, which are closer to a wall, more flexible (less stiff) or longer, deform more significantly and, for a wide range of the system parameters, they faster migrate towards the middle plane of the channel. For the considered systems, fiber velocity along the flow is only slightly smaller than (and can be well approximated by) the Poseuille flow velocity at the same position. In this way, the history of a fiber migration across the channel is sufficient to determine with a high accuracy its displacement along the flow.

Keywords:

Stokes equations, flexible fiber, Poiseuille flow, solid walls

Affiliations:
Słowicka A.M.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
Sadlej K.-IPPT PAN
Wajnryb E.-IPPT PAN
7.Adamczyk Z., Cichocki B., Ekiel-Jeżewska M.L., Słowicka A., Wajnryb E., Wasilewska M., Fibrinogen conformations and charge in electrolyte solutions derived from DLS and dynamic viscosity measurements, JOURNAL OF COLLOID AND INTERFACE SCIENCE, ISSN: 0021-9797, DOI: 10.1016/j.jcis.2012.07.010, Vol.385, pp.244-257, 2012
Abstract:

Hydrodynamic properties of fibrinogen molecules were theoretically calculated. Their shape was approximated by the bead model, considering the presence of flexible side chains of various length and orientation relative to the main body of the molecule. Using the bead model, and the precise many-multipole method of solving the Stokes equations, the mobility coefficients for the fibrinogen molecule were calculated for arbitrary orientations of the arms whose length was varied between 12 and 18 nm. Orientation averaged hydrodynamic radii and intrinsic viscosities were also calculated by considering interactions between the side arms and the core of the fibrinogen molecule. Whereas the hydrodynamic radii changed little with the interaction magnitude, the intrinsic viscosity exhibited considerable variation from 30 to 60 for attractive and repulsive interactions, respectively. These theoretical results were used for the interpretation of experimental data derived from sedimentation and diffusion coefficient measurements as well as dynamic viscosity measurements. Optimum dimensions of the fibrinogen molecule derived in this way were the following: the contour length 84.7 nm, the side arm length 18 nm, and the total volume 470 nm3, which gives 16% hydration (by volume). Our calculations enabled one to distinguish various conformational states of the fibrinogen molecule, especially the expanded conformation, prevailing for pH < 4 and lower ionic strength, characterized by high intrinsic viscosity of 50 and the hydrodynamic radius of 10.6 nm. On the other hand, for the physiological condition, that is, pH = 7.4 and the ionic strength of 0.15 M NaCl, the semi-collapsed conformation dominates. It is characterized by the average angle equal to = 55, intrinsic viscosity of 35, and the hydrodynamic radius of 10 nm. Additionally, the interaction energy between the arms and the body of the molecule was predicted to be 4 kT units, confirming that they are oppositely charged than the central nodule. Results obtained in our work confirm an essential role of the side chains responsible for a highly anisotropic charge distribution in the fibrinogen molecule. These finding can be exploited to explain anomalous adsorption of fibrinogen on various surfaces.

Keywords:

Bead model of fibrinogen, Charge distribution over fibrinogen, Conformations of fibrinogen molecule, Fibrinogen molecule conformations, Hydrodynamic radius of fibrinogen, Viscosity of fibrinogen solutions

Affiliations:
Adamczyk Z.-Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences (PL)
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Słowicka A.-IPPT PAN
Wajnryb E.-IPPT PAN
Wasilewska M.-other affiliation
8.Słowicka A.M., Walenta Z.A., Szymański Z., Expansion of a multi-component laser-ablated plume, EUROPEAN PHYSICAL JOURNAL-APPLIED PHYSICS, ISSN: 1286-0042, DOI: 10.1051/epjap/2011110056, Vol.56, pp.11101-p1-8, 2011
Abstract:

The expansion of a plume generated during laser ablation is studied with the Direct Simulation Monte Carlo method. The plume is a mixture of four disparate molecular mass components and expands in vacuum or into ambient gas. The time dependence of deposition rate is studied and the transition from an initial vacuum-like to a diffusion-like regime of expansion in ambient gas is shown. The lack of stoichiometry increases with the ratio of molecular masses of ablated particles and at disparate masses the stoichiometry is seriously affected. Ambient gas worsens the stoichiometry unless it supplies particles compensating the backward and sideward flows of plume constituents.

Keywords:

laser deposition, plume expansion, DSMC

Affiliations:
Słowicka A.M.-IPPT PAN
Walenta Z.A.-IPPT PAN
Szymański Z.-IPPT PAN
9.Słowicka A., Walenta Z.A., Creating thin layers at the contact surface of two nonmixing liquids, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, Vol.55, pp.173-178, 2007
Abstract:

The paper presents the results of numerical simulation of processes aimed at production of nanostructures with the use of oil emulsions in water. The appropriate molecular models of water and oil, as well as the model of the substance which would sediment at the water – oil interface, are looked for. Such substance, after suitable solidification, would become the main component of the produced material. For the described simulations, the Molecular Dynamics method has been used throughout this paper.

Keywords:

thin layers, contact surface, nonmixing liquids

Affiliations:
Słowicka A.-IPPT PAN
Walenta Z.A.-IPPT PAN
10.Słowicka A., Walenta Z.A., Powstawanie nanostruktur w emulsjach, Systems, Vol.11, pp.255-267, 2006
Abstract:

Współczesne technologie materiałowe są jedną z najszybciej rozwijających się dziedzin nauki i techniki. Szczególnie prężnie rozwijaj się nano- i mikrotechnologie. Jedna z takich nowoczesnych nanotechnologii, badana obecnie w kilku europejskich ośrodkach, wykorzystuje efekt gromadzenia się substancji na granicy faz emulsji. Użyta emulsja ma bardzo drobną strukturę nano-kropli oleju w wodzie. Trzecia substancja, dzięki odpowiednim właściwościom molekularnym, osiadając na powierzchni styku faz cieczy pokrywa powierzchnie kropel oleju. Po usunięciu emulsji substancja ta, zachowując strukturę, zostaje utwardzona i tworzy nano-materiał . W prezentowanej technologii emulsja spełnia rolę matrycy, na której powstaje struktura wytwarzanego materiału. Technik rozdrabniania emulsji jest wiele; stosuje się m.in. aparaty miksujące (homogenizatory), które w przepływie ścinającym rozrywają krople oleju na mniejsze lub mikrokanały o podobnym działaniu [2]. Nanomateriały o prezentowanej strukturze będą miały wiele interesujących właściwości, takich jak lekkość, elastyczność czy wytrzymałość mechaniczną, co zapewniają silne oddziaływania międzyatomowe w układzie oraz porowatość substancji. Tworzywa o takiej budowie mogą znaleźć zastosowanie w różnych dziedzinach np. medycynie czy aerodynamice. Celem naszych prac nad omawianą technologią wytwarzania nanomateriałów było stworzenie numerycznego modelu zjawiska powstawania nanostruktur w emulsjach. Ponieważ tak drobne układy wymagają modelowania na poziomie atomowym, do opisu procesów zachodzących w cieczach posłużono się metodą Dynamiki Molekularnej. Bazując na symulacjach numerycznych zbudowano modele molekularne cieczy tworzących emulsję oraz zaproponowano kilka typów substancji, które mogłyby wytworzyć pożądaną warstwę na granicy faz. Zaproponowane modele testowano numerycznie, poszukując kombinacji oddziaływań międzyatomowych zapewniającej powstawanie oczekiwanej nanostruktury

Keywords:

nanostruktury, emulsje, nanomateriały

Affiliations:
Słowicka A.-IPPT PAN
Walenta Z.A.-IPPT PAN

List of chapters in recent monographs
1.
549
Słowicka A.M., Walenta Z.A., Hoffman J., Chrzanowska J., Mościcki T., 30th International Symposium on Shock Waves 2, rozdział: Structure and Expansion of a Plume Emitted During Laser Ablation of Multicomponent Materials, Springer International Publishing AG 2017, 2, pp.869-873, 2017

Conference papers
1.Walenta Z.A., Słowicka A.M., Extinguishing detonation in pipelines – optimization of the process, ISIS 2016, 22nd International Shock Interaction Symposium, 2016-07-04/07-08, Glasgow (GB), pp.1-5, 2016
Abstract:

The necessity of extinguishing detonation, which may occur in pipelines transporting gaseous fuels, is nowadays a very important technological problem. The standard devices used for it consist of matrices of very narrow channels. Cooling the gas by cold walls of such channels may extinguish the flame and stop detonation. Detonation may also be extinguished if the cross-section of the channel transporting gas increases abruptly at some place. The desired effect may be achieved if the generated rarefaction waves decrease sufficiently the temperature of the flame (Teodorczyk et al. 1988, Cai et al. 2002, Dremin 1999, Walenta et al. 2004). It might be expected, that simultaneous use of both methods – using narrow channels with variable cross-section – should give even better results. Additional profit might come from the fact, that the flow in narrow channels is usually laminar; the abrupt increase of the cross-section would introduce some turbulence and this way enhance cooling by the walls. However, if the cross-section of the channel increases and decreases, the unwanted heating of the gas may occur. To estimate the net esult, which is not obvious, it is necessary to perform suitable simulations and experiments. The present paper is devoted to numerical simulation of the phenomenon.

Keywords:

extinguishing detonation, DSMC

Affiliations:
Walenta Z.A.-IPPT PAN
Słowicka A.M.-IPPT PAN
2.Walenta Z.A., Słowicka A., Structure of shock waves in complex molecular liquids, 29th International Symposium on Shock Waves, 2013-07-14/07-19, Madison (US), pp.1437-1441, 2013
Abstract:

The present paper is a continuation of our earlier work on the
structure of shock waves in dense media. Simple, monoatomic gas, argon, was con
sidered first [1]. It was found, that the shock thickness in dense argon, when re
lated to the mean distance between the molecules (as suggested by P.W. Bridgm
an [2]) decreased with increasing density. To illustrate the dependence of the thickness of the
shock wave on density of the medium, the results for liquid sulfur hexafluoride were
compared with experimental, shock tube results in gas phase at low density.

Keywords:

molecular dynamics simulations, complex liquids, shock waves

Affiliations:
Walenta Z.A.-IPPT PAN
Słowicka A.-IPPT PAN
3.Walenta Z.A., Słowicka A.M., Structure of shock waves in dense gases and liquids - Molecular Dynamics Simulation, 20th International Shock Interaction Symposium, 2012-08-20/08-24, Stockholm (SE), pp.1-4, 2012
Abstract:

In our earlier paper [3] we reported the investigation of the shock structure in dense, monatomic gas - argon. Here we extend our work to dense molecular gases and to liquids. We investigate, in particular, the influence of the electric charges (electric dipoles, quadrupoles etc.) of the molecules on the shock wave structure.

Keywords:

Shock structure, Dense media, Molecular Dynamics

Affiliations:
Walenta Z.A.-IPPT PAN
Słowicka A.M.-IPPT PAN
4.Słowicka A.M., Walenta Z.A., Szymański Z., Structure of the plume emitted during laser ablation of materials, ISSW28, 28th International Symposium on Shock Waves, 2011-07-17/07-22, Manchester (GB), pp.777-782, 2012
Keywords:

laser ablation, plume expansion, DSMC

Affiliations:
Słowicka A.M.-IPPT PAN
Walenta Z.A.-IPPT PAN
Szymański Z.-IPPT PAN
5.Walenta Z.A., Słowicka A.M., Structure of shock waves in dense media, ISSW28, 28th International Symposium on Shock Waves, 2011-07-17/07-22, Manchester (GB), pp.771-776, 2012
Keywords:

shock waves, dense fluids, molecular dynamics simulations

Affiliations:
Walenta Z.A.-IPPT PAN
Słowicka A.M.-IPPT PAN

Conference abstracts
1.Ekiel-Jeżewska M.L., Słowicka A.M., Wajnryb E., Dynamics of flexible fibers in shear flows, Flowing matter, 2016-01-11/01-15, Porto (PT), pp.74-75, 2016
2.Słowicka A.M., Stone H.A., Wajnryb E., Ekiel-Jeżewska M.L., Three modes of the dynamics of flexible fibers in shear flow, ICTAM XXIV, 24th International Congress of Theoretical and Applied Mechanics, 2016-08-21/08-26, Montréal (CA), pp.1142-1143, 2016
Abstract:

Dynamics of a single non-Brownian flexible fiber in shear flow at low Reynolds number is investigated numerically. Initially, the fiber is straight and at the equilibrium. For different initial orientations and values of bending stiffness, three generic scenarios are observed: the fiber tends to: align along the vorticity direction, tumble within the plane perpendicular to vorticity, or perform a periodic motion superposed with translation along the flow.

Keywords:

Stokes equations, flexible fibers, shear flow

Affiliations:
Słowicka A.M.-IPPT PAN
Stone H.A.-Princeton University (US)
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
3.Farutin A., Piasecki T., Słowicka A.M., Misbah C., Wajnryb E., Ekiel-Jeżewska M.L., Migration of vesicles and flexible fibers in poiseuille flow, ICTAM XXIV, 24th International Congress of Theoretical and Applied Mechanics, 2016-08-21/08-26, Montréal (CA), pp.1344-1345, 2016
Abstract:

Dynamics of flexible fibers and vesicles in unbounded planar Poiseuille flow at the low-Reynolds-number are shown to exhibit similar basic features, when their equilibrium (moderate) aspect ratio is the same and vesicle viscosity contrast is relatively high. The lateral migration and accumulation of these two types of flexible objects are analyzed numerically.

Keywords:

Stokes equations, vesicles, flexible fibers

Affiliations:
Farutin A.-Université Grenoble Alpes (FR)
Piasecki T.-IPPT PAN
Słowicka A.M.-IPPT PAN
Misbah C.-CNRS (FR)
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
4.Słowicka A.M., Wajnryb E., Ekiel-Jeżewska M.L., Flexible Fibers in Shear Flow, 6th International Symposium on Bifurcations and Instabilities in Fluid Dynamics, 2015-07-15/07-17, Paryż (FR), pp.61, 2015
Abstract:

Modes of the dynamics of flexible fibers in shear flow in a plane perpendicular to vorticity are analyzed numerically.

Dynamics of flexible fibers in shear flow are analyzed numerically for a wide range of the ratios A of the fiber bending force to the hydrodynamic force. The Reynolds number is much smaller that unity, and the Péclet number much greater than one. A fiber is modeled as a chain of solid beads as in Ref. [1]. The centers of the consecutive beads are linked by springs. The equilibrium length of each spring is such that the consecutive beads almost touch each other. The spring constant is large, and the fiber’s length practically does not change with time. At the equilibrium, the fiber is straight. At a deformed configuration, there appear a bending force exerted on each bead, proportional to the bending parameter A. The details of the model and the numerical method can be found in Ref. [2]. Velocities of the beads at given positions are evaluated with the use of the HYDROMULTIPOLE numerical code, based on solving the Stokes equations by the multipole expansion [3]. The time-dependent positions of the beads are determined by the adaptive fourth order Runge-Kutta method.

Initially, the fiber is aligned with the flow, and the springs are at the equilibrium. Owing to symmetry, the centers of all the beads move in the plane perpendicular to the vorticity direction. The fiber end-to-end vector tumbles, in a similar way as a rigid elongated body [4]. While the fiber turns, its shape evolves accordingly, and the center-of-mass oscillates across the flow. A surprisingly rich spectrum of different modes is observed when the value of A is systematically changed, with regular and chaotic trajectories. (For the details, see Ref. [5].)

For some ranges of small and large values of A, the center-of-mass trajectories are periodic with a single tumbling time τ, and there is no migration across the flow. For a certain range of small values of A, evolutions during every second tumbling time are the same, but consecutive tumbling times differ from each other, what leads to regular migrating trajectories of the fiber center-of-mass. For moderate values of A, a chaotic behavior is observed - a large sensitivity of the dynamics to a small change of A, with (typically) many irregular, erratic trajectories or (exceptionally) some regular migrating trajectories. At a moderate value of A, a transition is observed between a ‘straightening out’ mode of more stiff fibers to the coiled mode of more flexible fibers. In the straightening out mode, the fiber significantly changes its shape while tumbling - from almost straight and aligned with the flow to S-shaped. In the coiled mode, the fiber is always compact, it never aligns with the flow.

References
[1] E. Gauger, H. Stark, Numerical study of a microscopic artificial swimmer , Phys. Rev. E 74, 021907 (2006).
[2] A. M. Słowicka, E. Wajnryb, M. L. Ekiel-Jeżewska, Lateral migration of flexible fibers in Poiseuille flow between two parallel planar solid walls , Eur. Phys. J. E 36, 1-12 (2013).
[3] B. Cichocki, M. L. Ekiel-Jeżewska, E. Wajnryb, Lubrication corrections for three-particle contribution to short-time self-diffusion coefficients in colloidal dispersions , J. Chem. Phys. 111, 3265 (1999).
[4] G. Jeffery, The Motion of Ellipsoidal Particles Immersed in a Viscous Fluid , Proc. R. Soc. Lond. A. 102, 161-179 (1922).
[5] A. M. Słowicka, E. Wajnryb, M. L. Ekiel-Jeżewska Dynamics of flexible fibers in shear flow , arXiv [cond-mat.soft] (2015).

Keywords:

Stokes equations, flexible fibers, shear flow

Affiliations:
Słowicka A.M.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
5.Słowicka A., Walenta Z., Szymański Z., Hoffman J., Mościcki T., Structure and expansion of a plume emitted during laser ablation of multi-component materials, ISSW30, 30th International Symposium on Shock Waves, 2015-07-19/07-24, Tel-Aviv (IL), pp.562-571, 2015
Abstract:

Pulsed laser deposition is a method frequently used for creating thin films of various materials on
solid substrates. High energy laser pulse causes evaporation of the target material, forming a
plume which subsequently
expands and moves with high speed from the target. Thin film of the
evaporated material is deposited on the substrate placed at some distance in front of the target.
The behavior of the plume influences both the stoichiometry and homogeneity of the deposit
ed
layer

the final product of the process. Better understanding of the process of expansion of the
plume, variation of its structure as well as deposition of the material itself is therefore very
important and should give us opportunity for better contro
l of formation of the deposited layer.

Keywords:

laser ablation, plume expansion, DSMC

Affiliations:
Słowicka A.-IPPT PAN
Walenta Z.-IPPT PAN
Szymański Z.-IPPT PAN
Hoffman J.-IPPT PAN
Mościcki T.-IPPT PAN
6.Walenta Z.A., Słowicka A.M., Similarity Parameters for Shock Waves in Dense Fluids, ISSW30, 30th International Symposium on Shock Waves, 2015-07-19/07-24, Tel-Aviv (IL), pp.536-537, 2015
Keywords:

shock waves, dense fluids, molecular dynamics simulations

Affiliations:
Walenta Z.A.-IPPT PAN
Słowicka A.M.-IPPT PAN
7.Walenta Z.A., Słowicka A.M., Influence of moments of inertia of molecules on the structure of shocks in molecular liquids, KKNM, 4th National Conference on Nano- and Micromechanics, 2014-07-08/07-10, Wrocław (PL), pp.76, 2014
Keywords:

shock waves, dense media, molecular dynamics symulations

Affiliations:
Walenta Z.A.-IPPT PAN
Słowicka A.M.-IPPT PAN
8.Słowicka A.M., Wajnryb E., Ekiel-Jeżewska M.L., Migration of flexible fibers entrained by Poiseuille flow in microchannel, ICTAM XXIII, 23rd International Congress of Theoretical and Applied Mechanics, 2012-08-19/08-24, Beijing (CN), pp.1-2, 2012
Abstract:

In this work, we consider a single non-Brownian mobile and flexible fiber immersed in Poiseuille flow in a channel consisting of two parallel infinite walls. The dynamics of the fiber is evaluated numerically from the Stokes equations by a multipole code HYDROMULTIPOLE. Investigating the fiber dynamics we found out that fibers migrate to a critical position across the channel. The distance between the wall and a limiting position depends on the fiber elongation and flexibility. For more stiff fibers the critical position results from the interplay between their tendency to drift away from the channel and the repulsive hydrodynamic interaction with the wall. For less stiff fibers the limiting position is not influenced by the presence of the wall. Differences between the critical position for different fibers can be used in the process of microfibers separation by the flow.

Keywords:

Stokes equations, hydrodynamic interactions, Poiseuille flow, flecible fiber

Affiliations:
Słowicka A.M.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
9.Walenta Z.A., Słowicka A.M., Structure of shock waves in dense gases and liquids - Molecular Dynamics Simulation, III National Conference of Nano and Micromechanics, 2012-07-04/07-06, Warszawa (PL), pp.99-100, 2012
Keywords:

shock waves, dense fluids, molecular dynamics simulations

Affiliations:
Walenta Z.A.-IPPT PAN
Słowicka A.M.-IPPT PAN
10.Słowicka A.M., Wajnryb E., Ekiel-Jeżewska M.L., Migration of microfibers entrained by Poiseuille flow in microchannel, III National Conference of Nano and Micromechanics, 2012-07-04/07-06, Warszawa (PL), pp.71-72, 2012
Keywords:

Stokes equations, Poiseuille flow, flexible fibers, migration

Affiliations:
Słowicka A.M.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN