arXiv subjects

J. Ilnytskyi

Publications and source records attributed to J. Ilnytskyi.

10 recordsLinked to original sources

arXiv2026

Modelling SARS-CoV-2 epidemics via compartmental and cellular automaton SEIRS model with temporal immunity and vaccination

We consider the SEIRS epidemiology model with such features of the COVID-19 outbreak as: abundance of unidentified infected individuals, limited time of immunity and a possibility of vaccination. The control of the pandemic dynamics is possible by restricting the transmission rate, increasing identification and isolation rate of infected individuals, and via vaccination. For the compartmental version of this model, we found stable disease-free and endemic stationary states. The basic reproductive number is analysed with respect to balancing quarantine and vaccination measures. The positions and heights of the first peak of outbreak are obtained numerically and fitted to simple in usage algebraic forms. Lattice-based realization of this model is studied by means of the asynchronous cellular automaton algorithm. This permitted to study the effect of social distancing by varying the neighbourhood size of the model. The attempt is made to match the quarantine and vaccination effects.

q-bio.PE↗

arXiv2023

Modelling thermoresponsive polymer brush by mesoscale computer simulations

We consider a functional surface comprising thermoresponsive polymer chains, the material that has found numerous technological and biomedical applications. However, to achieve the required time and length scales for computer modelling of such applications, one is compelled to use coarse-grained mesoscopic modelling approaches. The model used here is based on the previous work [Soto-Figueroa et al., Soft Matter, 8, 1871 (2012)], and it mimics the principal feature of the poly(N-iso-propylacrylamide) (PNIPAM), namely, the rapid change of its hydrophilicity at the lower critical solution temperature (LCST). For the case of an isolated chain, we discuss scaling properties of the radius of gyration, end-to-end distance, various distribution functions, and the density profile of monomers below and above the LCST. For the case of the model thermoresposive brush, we search for the optimum grafting density at which the change in the brush height, upon crossing the LCST, reaches its maximum value. The interpretation of the thermoresponse, in terms of the Alexander-de Gennes blobs and the level of solvation of polymer chains in a brush, is provided.

cond-mat.soft↗

arXiv2021

Photo-switchable liquid crystalline brush as an aligning surface for liquid crystals: modelling via mesoscopic computer simulations

We consider the mesoscopic model for the liquid crystalline brush that might serve as a photoswitchable aligning surface for preorientation of low molecular weight liquid crystals in a bulk. The brush is built by grafting the polymer chains of a side-chain molecular architecture, with the side chains terminated by a chromophore unit mimicking the azobenzene unit, to a substrate. When irradiated with ultraviolet light, the chromophores photoisomerize into a non-mesogenic cis state and the whole system turns into an ordinary polymer brush with no orientational order and two states: the collapsed and straightened one, depending on the grafting density. When irradiated with visible light, the chromophores photoisomerize into a mesogenic trans state, resulting in formation of a transient network between chains because of a strong attraction between chromophores. Spontaneous self-assembly of the brush in these conditions results in an orientationally isotropic polydomain structure. The desired uniaxial planar ordering of chromophores within a brush can be achieved at certain temperature and grafting density intervals, as the result of a two-stage preparation protocol. An external stimulus orients chromophores uniaxially at the first stage. The system is equilibrated at the second stage at a given temperature and with the external stimulus switched off. The preoriented chromophores either keep or loose their orientations depending on the strength of the memory effect inherent to a transient network of chains that are formed during the first stage, similarly to the case of the liquid crystalline elastomers, where such effects are caused by the covalent crosslinks.

cond-mat.soft↗

arXiv2021

Experimental and computer simulation studies of the micelles formed by comb-like PEG-containing polymeric surfactants as potential enzyme scaffolds

The industrial implementation of biofuel production from lignocellulosic biomass faces a number of economic obstacles. One of these is the cost of enzymes, typically used for cellulose hydrolysis. Nature provides some hints towards the efficiency of this process, exampled in natural enzyme complexes - cellulosomes, produced by some microorganisms. Therefore, many research groups target synthetic routes to mimic such cellulosomes with synthetic structures when many questions remain to be addressed: the optimal chemical structure and size of such synthetic scaffolds, their adsorption on the cellulosic biomass particles, combinations, and best practices arrangement of enzymes in the complex. In this work, polyethylene glycol (PEG) copolymers that form micelles and accommodate enzymes in the micellar structures are systematically studied using both experimental and computer simulation techniques. Preliminary results indicate that the micelles are efficient polymer - enzymes structures for cellulose hydrolysis. While the direct quantitative comparison between the real and model systems is not always straightforward, both approaches agree on the role of the molecular architecture of the copolymers on micelle formation and their structural characteristics.

cond-mat.soft↗

arXiv2014

Description of interfaces of fluid-tethered chains: advances in density functional theories and off-lattice computer simulations

Many objects of nanoscopic dimensions involve fluid-tethered chain interfaces. These systems are of interest for basic science and for several applications, in particular for design of nanodevices for specific purposes. We review recent developments of theoretical methods in this area of research and in particular of density functional (DF) approaches, which provide important insights into microscopic properties of such interfaces. The theories permit to describe the dependence of adsorption, wettability, solvation forces and electric interfacial phenomena on thermodynamic states and on characteristics of tethered chains. Computer simulations for the problems in question are overviewed as well. Theoretical results are discussed in relation to simulation results and to some experimental observations.

cond-mat.soft↗

arXiv2012

Marian Smoluchowski: A story behind one photograph

We discuss the photograph procured from the archives of the V. Stefanyk Lviv National Scientific Library of Ukraine dated by 1904 which shows Marian Smoluchowski together with professors and graduate students of the Philosophy department of the Lviv University. The personalia includes both the professors and the graduates depicted on the photograph with the emphasis on the graduates as being much less known and studied. The photograph originates from the collection of the Shevchenko Scientific Society, therefore a brief historical background on the activities of physicists in this society around that period of time is provided as well.

physics.hist-ph↗

arXiv2009

On the universality class of the 3d Ising model with long-range-correlated disorder

We analyze a controversial question about the universality class of the three-dimensional Ising model with long-range-correlated disorder. Whereas both analytical and numerical studies performed so far support an extended Harris criterion (A. Weinrib, B. I. Halperin, Phys. Rev. B 27 (1983) 413) and bring about the new universality class, the numerical values of the critical exponents found so far differ essentially. To resolve this discrepancy we perform extensive Monte Carlo simulations of a 3d Ising magnet with non-magnetic impurities arranged as lines with random orientation. We apply Wolff cluster algorithm accompanied by a histogram reweighting technique and make use of the finite-size scaling to extract the values of critical exponents governing the magnetic phase transition. Our estimates for the exponents differ from the results of the two numerical simulations performed so far and are in favour of a non-trivial dependency of the critical exponents on the peculiarities of long-range correlations decay.

cond-mat.dis-nn↗

arXiv2006

Local and cluster critical dynamics of the 3d random-site Ising model

We present the results of Monte Carlo simulations for the critical dynamics of the three-dimensional site-diluted quenched Ising model. Three different dynamics are considered, these correspond to the local update Metropolis scheme as well as to the Swendsen-Wang and Wolff cluster algorithms. The lattice sizes of L=10-96 are analysed by a finite-size-scaling technique. The site dilution concentration p=0.85 was chosen to minimize the correction-to-scaling effects. We calculate numerical values of the dynamical critical exponents for the integrated and exponential autocorrelation times for energy and magnetization. As expected, cluster algorithms are characterized by lower values of dynamical critical exponent than the local one: also in the case of dilution critical slowing down is more pronounced for the Metropolis algorithm. However, the striking feature of our estimates is that they suggest that dilution leads to decrease of the dynamical critical exponent for the cluster algorithms. This phenomenon is quite opposite to the local dynamics, where dilution enhances critical slowing down.

cond-mat.dis-nn↗

arXiv2005

Static and dynamic critical behaviour of 3d random site Ising model: different Monte Carlo algorithms

We perform numerical simulations to study static and dynamic critical behaviour of the 3d random-site Ising model. A distinct feature of our approach is a combination of the Metropolis, Swendsen-Wang, and Wolff Monte Carlo algorithms. For the static critical behaviour, these approaches are the complementary ones, whereas in dynamics they correspond to three different types of relaxation, being a particular subject of our study.

cond-mat.dis-nn↗

arXiv2005

Criticality of the random-site Ising model: Metropolis, Swendsen-Wang and Wolff Monte Carlo algorithms

We apply numerical simulations to study the criticality of the 3D Ising model with random site quenched dilution. The emphasis is given to the issues not being discussed in detail before. In particular, we attempt a comparison of different Monte Carlo techniques, discussing regions of their applicability and advantages/disadvantages depending on the aim of a particular simulation set. Moreover, besides evaluation of the critical indices we estimate the universal ratio $Γ^+/Γ^-$ for the magnetic susceptibility critical amplitudes. Our estimate $Γ^+/Γ^- = 1.67 \pm 0.15$ is in a good agreement with the recent MC analysis of the random-bond Ising model giving further support that both random-site and random-bond dilutions lead to the same universality class.

cond-mat.stat-mech↗