Jan Jadżyn

Bio: Jan Jadżyn is an academic researcher from Polish Academy of Sciences. The author has contributed to research in topics: Liquid crystal & Dielectric. The author has an hindex of 25, co-authored 234 publications receiving 2453 citations. Previous affiliations of Jan Jadżyn include Katholieke Universiteit Leuven.

The Influence of Magnetic Particles on the Nematic Droplets Formation in Liquid Crystal

Abstract: In this work the thermotropic nematic liquid crystal 4-trans-4′-n-hexyl-cyclohexyl-isothiocyanato-benzene (6CHBT) was dissolved in phenyl-isothiocyanate and doped with spherical magnetic particles with volume concentration φ1 = 10−4 and φ2 = 10−3. The influence of the volume concentration on the phase transitions from isotropic to nematic phase was studied by three experimental methods: optical microscopy, differential scanning calorimetry, and dielectric measurements. The obtained results confirmed the coexistence of isotropic and nematic phase, i.e. nematic or ferronematic droplets in isotropic phase in a wide temperature range between nematic and isotropic phase.

Modeling of the Viscosity Behavior in the Interface Area of Two Miscible Liquids

Abstract: The paper presents the results of the share viscosity (η) investigations performed for binary mixtures composed of the liquids of extremely different viscosities: a high-viscous α-tocopherol acetate (η ≈ 10 Pa s) is mixed with 4-n-propylcyclohexyl-4′-n-pentylphenyl (η ≈ 10 mPa s) and mesitilene (η ≈ 1 mPa s), the two low-viscous solvents composed of the non-polar molecules of an essentially different shape. It was found that the viscosities of the mixtures, disregarding the molecular shape of the non-polar admixture, exhibit a strong nonlinear dependence on tocopherol mole fraction and, at a given temperature, the dependence can be described with an exponential function. For a constant tocopherol concentration in the mixtures, the viscosity temperature dependences are well described with the Vogel–Fulcher–Tammann relation. The results can be considered as a model of the viscosity behavior related to the laminar flow of miscible liquids of a different viscosity being in contact to each other.

Magnetic-Field Induced Isotropic-Nematic Phase Transition in PDLC Doped with Magnetic Nanoparticles

Abstract: Z. Mitroovaa,∗, N. Toma2ovi£ova, M. Timko, M. Koneracka, L. Tom£o, J. Jad»yn, T. Palewski, and P. Kop£anský and O.V. Kovalchuk Institute of Experimental Physics, SAS, Watsonova 47, 040 01 Ko2ice, Slovakia Faculty of Aeronautics, Technical University, Rampova 7, 041 21, Ko2ice, Slovakia Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Pozna«, Poland International Laboratory of High Magnetic Fields and Low Temperatures, Polish Academy of Sciences

The structural transitions in the thermotropic ferronematics

Abstract: The structural transitions in thermotropic ferronematic, i.e. nematic liquid crystal (8CB) doped with fine magnetic particles (d ~10 nm), exposed to combined electric and magnetic fields, were studied within the Burylov and Raikher's theory. Using the found formulas for the threshold fields of studied transitions and their values obtained by the capacitance measurements, the anchoring energy W of liquid crystal molecules on the magnetic particles surfaces, as well as parameter ω, determining the type of anchoring, were calculated. The calculated values indicated the presence of soft, or some intermediate state between soft and rigid anchoring, in studied ferronematic. These results are in agreement with the Burylov and Raikher's theory of thermotropic ferronematics.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The restaurant at the end of the random walk: recent developments in the description of anomalous transport by fractional dynamics

Abstract: Fractional dynamics has experienced a firm upswing during the past few years, having been forged into a mature framework in the theory of stochastic processes. A large number of research papers developing fractional dynamics further, or applying it to various systems have appeared since our first review article on the fractional Fokker–Planck equation (Metzler R and Klafter J 2000a, Phys. Rep. 339 1–77). It therefore appears timely to put these new works in a cohesive perspective. In this review we cover both the theoretical modelling of sub- and superdiffusive processes, placing emphasis on superdiffusion, and the discussion of applications such as the correct formulation of boundary value problems to obtain the first passage time density function. We also discuss extensively the occurrence of anomalous dynamics in various fields ranging from nanoscale over biological to geophysical and environmental systems.

A Medicinal Chemist’s Guide to Molecular Interactions

Abstract: Molecular recognition in biological systems relies on the existence of specific attractive interactions between two partner molecules. Structure-based drug design seeks to identify and optimize such interactions between ligands and their host molecules, typically proteins, given their three-dimensional structures. This optimization process requires knowledge about interaction geometries and approximate affinity contributions of attractive interactions that can be gleaned from crystal structure and associated affinity data. Here we compile and review the literature on molecular interactions as it pertains to medicinal chemistry through a combination of careful statistical analysis of the large body of publicly available X-ray structure data and experimental and theoretical studies of specific model systems. We attempt to extract key messages of practical value and complement references with our own searches of the CSDa,(1) and PDB databases.(2) The focus is on direct contacts between ligand and protein functional groups, and we restrict ourselves to those interactions that are most frequent in medicinal chemistry applications. Examples from supramolecular chemistry and quantum mechanical or molecular mechanics calculations are cited where they illustrate a specific point. The application of automated design processes is not covered nor is design of physicochemical properties of molecules such as permeability or solubility. Throughout this article, we wish to raise the readers’ awareness that formulating rules for molecular interactions is only possible within certain boundaries. The combination of 3D structure analysis with binding free energies does not yield a complete understanding of the energetic contributions of individual interactions. The reasons for this are widely known but not always fully appreciated. While it would be desirable to associate observed interactions with energy terms, we have to accept that molecular interactions behave in a highly nonadditive fashion.3,4 The same interaction may be worth different amounts of free energy in different contexts, and it is very hard to find an objective frame of reference for an interaction, since any change of a molecular structure will have multiple effects. One can easily fall victim to confirmation bias, focusing on what one has observed before and building causal relationships on too few observations. In reality, the multiplicity of interactions present in a single protein−ligand complex is a compromise of attractive and repulsive interactions that is almost impossible to deconvolute. By focusing on observed interactions, one neglects a large part of the thermodynamic cycle represented by a binding free energy: solvation processes, long-range interactions, conformational changes. Also, crystal structure coordinates give misleadingly static views of interactions. In reality a macromolecular complex is not characterized by a single structure but by an ensemble of structures. Changes in the degrees of freedom of both partners during the binding event have a large impact on binding free energy. The text is organized in the following way. The first section treats general aspects of molecular design: enthalpic and entropic components of binding free energy, flexibility, solvation, and the treatment of individual water molecules, as well as repulsive interactions. The second half of the article is devoted to specific types of interactions, beginning with hydrogen bonds, moving on to weaker polar interactions, and ending with lipophilic interactions between aliphatic and aromatic systems. We show many examples of structure−activity relationships; these are meant as helpful illustrations but individually can never confirm a rule.

Supercooled dynamics of glass-forming liquids and polymers under hydrostatic pressure

Abstract: An intriguing problem in condensed matter physics is understanding the glass transition, in particular the dynamics in the equilibrium liquid close to vitrification Recent advances have been made by using hydrostatic pressure as an experimental variable These results are reviewed, with an emphasis in the insight provided into the mechanisms underlying the relaxation properties of glass-forming liquids and polymers

Ionic Liquid Crystals: Versatile Materials.

Abstract: This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.