Vìsnik Nacìonalʹnoï akademìï nauk Ukraïni/Vìsnik Nacìonalʹnoï akademìï nauk Ukraïni, Feb 28, 2024
Вельмишановні учасники зборів! Вельмишановні колеги! Доволі часто цитують слова Луї Пастера «La s... more Вельмишановні учасники зборів! Вельмишановні колеги! Доволі часто цитують слова Луї Пастера «La science n'a pas de patrie», що в перекладі звучать як «Наука не має батьківщини». Проте дуже повчально почитати повний виклад відповідного фрагменту тексту, в якому фігурує ця цитата: «Мене пронизують два глибокі враження: перше -наука не має батьківщини, друге, яке, здавалося б, виключає перше, але є його прямим наслідком, -наука повинна бути найвищим уособленням батьківщини. Наука не має батьківщини, оскільки знання -це надбання людства, факел, який освітлює світ. Наука повинна бути найвищим уособленням вітчизни, бо з усіх народів завжди буде першим той, хто буде йти першим ділами думки та інтелекту. Тож борімося на мирній науковій ниві за вищість наших батьківщин». Важко не погодитися з цими словами видатного французького хіміка і мікробіолога, який жив і творив у Франції, був членом Французької академії наук. У Луї Пастера не виникало жодних сумнівів щодо його вітчизни, якою була Франція, де в 1665 р. почали видавати перший у царині гуманітарних наук журнал «Journal des sçavans» (з 1816 р. -Journal des savants; «журнал вчених»), а в 1666 р. король Людовік XIV заснував Французьку академію наук «для заохочення й захисту духу французьких наукових досліджень». Доречно згадати й найстаріше товариство природознавців -Німецьку академію природодослідників «Леопольдина», яку було засновано в Німеччині в 1652 р. У 1687 р. імператор Священної Римської імперії Леопольд І надав їй статус Академії Римської імперії під своїм іменем і так виникла скорочена назва Leopoldina. А найстарішим науковим періодичним виданням у царині природничих наук вважають журнал «Philosophical Transactions of the Royal Society» (Філософські праці Королівського товариства), пер-
Процеси метастабiльної лiквацiї в склоутворюючих системах: огляд лiтературних джерел i розрахунок... more Процеси метастабiльної лiквацiї в склоутворюючих системах: огляд лiтературних джерел i розрахунок фазових дiаграм з метастабiльною лiквацiєю ICMP–03–15U Процеси метастабiльної лiквацiї в склоутворюючих систе-мах: огляд лiтературних джерел i розрахунок фазових дiа-грам з метастабiльною лiквацiєю. Metastable liquid-liquid separation in multi-component glass systems: a review of experimental and theoretical results; phase diagrams with the metastable liquation. Abstract. Present view of the nature of the metastable liquid-liquid separation in multi-component glass-like systems as well as its main features (thermodynamic and kinetic)s are outlined. Based on the thermo-dynamic method the phase diagrams for several binary compounds are calculated.
We present a theoretical study of non-hydrodynamic propagating processes, which correspond to hea... more We present a theoretical study of non-hydrodynamic propagating processes, which correspond to heat waves in liquids. It is shown, that heat waves can propagate in liquids only on a finite spatial scale and do not appear in the long-wavelength region. An expression for a propagation gap for heat waves is derived within a five-variable generalized hydrodynamic treatment. Molecular dynamics simulations were performed for four thermodynamic states of a one-component Lennard-Jones fluid in order to estimate dependence of the propagation gap on temperature. PACS: 61.20.Ja, 61.20.Lc, 05.60.+w
One of the features of modern science is the formation of stable large collaboration of researche... more One of the features of modern science is the formation of stable large collaboration of researchers working together within the projects that require the concentration of huge financial and human resources. Results of such common work are published in scientific papers by large co-authorship teams that include sometimes thousands of names. The goal of this work is to study the influence of such publications on the values of scientometric indicators calculated for individuals, research groups and science of Ukraine in general. Bibliometric data related to Ukraine, sоme academic Institutions and selected individual researchers were collected from Scopus database and used for our study. It is demonstrated that while the relative share of publications by collective authors is comparatively small, their presence in a general pool can lead to statistically significant effects. The obtained results clearly show that traditional quantitative approaches for research assessment should be changed in order to take into account this phenomenon.
The spatiotemporal pattern formation is studied in the catalytic carbon monoxide oxidation reacti... more The spatiotemporal pattern formation is studied in the catalytic carbon monoxide oxidation reaction that takes into account the diffusion processes over the Pt(110) surface, which may contain structurally different areas. These areas are formed during CO-induced transition from a reconstructed phase with 1 × 2 geometry of the overlayer to a bulk-like (1 × 1) phase with square atomic arrangement. Despite the CO oxidation reaction being non-autocatalytic, we have shown that the analytic conditions of the existence of the Turing and the Hopf bifurcations can be satisfied in such systems. Thus, the system may lose its stability in two ways-either through the Hopf bifurcation leading to the formation of temporal patterns in the system or through the Turing bifurcation leading to the formation of regular spatial patterns. At a simultaneous implementation of both scenarios, spatiotemporal patterns for CO and oxygen coverages are obtained in the system.
A simple ansatz for the study of velocity autocorrelation functions in fluids at different timesc... more A simple ansatz for the study of velocity autocorrelation functions in fluids at different timescales is proposed. The ansatz is based on an effective summation of the infinite continued fraction at a reasonable assumption about convergence of relaxation times of the higher order memory functions, which have a purely kinetic origin. The VAFs obtained within our approach are compared with the results of the Markovian approximation for memory kernels. It is shown that although in the "overdamped" regime both approaches agree to a large extent at the initial and intermediate times of the system evolution, our formalism yields power law relaxation of the VAFs which is not observed at the description with a finite number of the collective modes. Explicit expressions for the transition times from kinetic to hydrodynamic regimes are obtained from the analysis of the singularities of spectral functions in the complex frequency plane.
The mechanism of spatio-temporal pattern formation at the catalytic oxidation of carbon monoxide ... more The mechanism of spatio-temporal pattern formation at the catalytic oxidation of carbon monoxide on the Pt(110) surface has been studied. The surface may contain structurally different areas, which are formed in the course of the CO-induced transition from the reconstructed 1×2 phase to the 1×1 (bulk) one. Temporal and spatial instabilities in the system are analyzed, by using the methods of the linear theory of stability and numerical simulations. Fragments of spatio-temporal structures of the oxygen coverage together with fragments of the surface 1 × 1 structure are shown to emerge on the inhomogeneous surface at certain system parameters. The distribution of the carbon monoxide coverage is found to be almost homogeneous in space and independent of the surface geometry.
ABSTRACT Using the collective variables (CV) method the basic relations of statistical field theo... more ABSTRACT Using the collective variables (CV) method the basic relations of statistical field theory of a multicomponent non-homogeneous fluids are reconsidered. The corresponding CV action depends on two sets of scalar fields - fields $\rho_{\alpha}$ connected to the local density fluctuations of the $\alpha$th species of particles and fields $\omega_{\alpha}$ conjugated to $\rho_{\alpha}$. The explicit expressions for the CV field correlations and their relation to the density correlation functions are found. The perturbation theory is formulated and a mean field level (MF) of the theory is considered in detail.
Advanced Problems of Phase Transition TheoryVolume 3, 2012
ABSTRACT For the last two decades, both phase diagrams and the critical behaviour of ionic fluids... more ABSTRACT For the last two decades, both phase diagrams and the critical behaviour of ionic fluids with dominant Coulomb interactions have been intensively studied using experimental and theoretical methods. In this chapter we present the overview of the progress made in this field. The main attention is focused on the theoretical results obtained for the primitive models of ionic fluids. We discuss the results of the mean field theories, in particular the Debye-Hückel theory and the mean spherical approximation as well as their generalizations related to the explicit inclusion of the ion association. We also review the recent results of statistical field theory that uses functional methods and allows one to go beyond the mean field approximation.
Vìsnik Nacìonalʹnoï akademìï nauk Ukraïni/Vìsnik Nacìonalʹnoï akademìï nauk Ukraïni, Feb 28, 2024
Вельмишановні учасники зборів! Вельмишановні колеги! Доволі часто цитують слова Луї Пастера «La s... more Вельмишановні учасники зборів! Вельмишановні колеги! Доволі часто цитують слова Луї Пастера «La science n'a pas de patrie», що в перекладі звучать як «Наука не має батьківщини». Проте дуже повчально почитати повний виклад відповідного фрагменту тексту, в якому фігурує ця цитата: «Мене пронизують два глибокі враження: перше -наука не має батьківщини, друге, яке, здавалося б, виключає перше, але є його прямим наслідком, -наука повинна бути найвищим уособленням батьківщини. Наука не має батьківщини, оскільки знання -це надбання людства, факел, який освітлює світ. Наука повинна бути найвищим уособленням вітчизни, бо з усіх народів завжди буде першим той, хто буде йти першим ділами думки та інтелекту. Тож борімося на мирній науковій ниві за вищість наших батьківщин». Важко не погодитися з цими словами видатного французького хіміка і мікробіолога, який жив і творив у Франції, був членом Французької академії наук. У Луї Пастера не виникало жодних сумнівів щодо його вітчизни, якою була Франція, де в 1665 р. почали видавати перший у царині гуманітарних наук журнал «Journal des sçavans» (з 1816 р. -Journal des savants; «журнал вчених»), а в 1666 р. король Людовік XIV заснував Французьку академію наук «для заохочення й захисту духу французьких наукових досліджень». Доречно згадати й найстаріше товариство природознавців -Німецьку академію природодослідників «Леопольдина», яку було засновано в Німеччині в 1652 р. У 1687 р. імператор Священної Римської імперії Леопольд І надав їй статус Академії Римської імперії під своїм іменем і так виникла скорочена назва Leopoldina. А найстарішим науковим періодичним виданням у царині природничих наук вважають журнал «Philosophical Transactions of the Royal Society» (Філософські праці Королівського товариства), пер-
Процеси метастабiльної лiквацiї в склоутворюючих системах: огляд лiтературних джерел i розрахунок... more Процеси метастабiльної лiквацiї в склоутворюючих системах: огляд лiтературних джерел i розрахунок фазових дiаграм з метастабiльною лiквацiєю ICMP–03–15U Процеси метастабiльної лiквацiї в склоутворюючих систе-мах: огляд лiтературних джерел i розрахунок фазових дiа-грам з метастабiльною лiквацiєю. Metastable liquid-liquid separation in multi-component glass systems: a review of experimental and theoretical results; phase diagrams with the metastable liquation. Abstract. Present view of the nature of the metastable liquid-liquid separation in multi-component glass-like systems as well as its main features (thermodynamic and kinetic)s are outlined. Based on the thermo-dynamic method the phase diagrams for several binary compounds are calculated.
We present a theoretical study of non-hydrodynamic propagating processes, which correspond to hea... more We present a theoretical study of non-hydrodynamic propagating processes, which correspond to heat waves in liquids. It is shown, that heat waves can propagate in liquids only on a finite spatial scale and do not appear in the long-wavelength region. An expression for a propagation gap for heat waves is derived within a five-variable generalized hydrodynamic treatment. Molecular dynamics simulations were performed for four thermodynamic states of a one-component Lennard-Jones fluid in order to estimate dependence of the propagation gap on temperature. PACS: 61.20.Ja, 61.20.Lc, 05.60.+w
One of the features of modern science is the formation of stable large collaboration of researche... more One of the features of modern science is the formation of stable large collaboration of researchers working together within the projects that require the concentration of huge financial and human resources. Results of such common work are published in scientific papers by large co-authorship teams that include sometimes thousands of names. The goal of this work is to study the influence of such publications on the values of scientometric indicators calculated for individuals, research groups and science of Ukraine in general. Bibliometric data related to Ukraine, sоme academic Institutions and selected individual researchers were collected from Scopus database and used for our study. It is demonstrated that while the relative share of publications by collective authors is comparatively small, their presence in a general pool can lead to statistically significant effects. The obtained results clearly show that traditional quantitative approaches for research assessment should be changed in order to take into account this phenomenon.
The spatiotemporal pattern formation is studied in the catalytic carbon monoxide oxidation reacti... more The spatiotemporal pattern formation is studied in the catalytic carbon monoxide oxidation reaction that takes into account the diffusion processes over the Pt(110) surface, which may contain structurally different areas. These areas are formed during CO-induced transition from a reconstructed phase with 1 × 2 geometry of the overlayer to a bulk-like (1 × 1) phase with square atomic arrangement. Despite the CO oxidation reaction being non-autocatalytic, we have shown that the analytic conditions of the existence of the Turing and the Hopf bifurcations can be satisfied in such systems. Thus, the system may lose its stability in two ways-either through the Hopf bifurcation leading to the formation of temporal patterns in the system or through the Turing bifurcation leading to the formation of regular spatial patterns. At a simultaneous implementation of both scenarios, spatiotemporal patterns for CO and oxygen coverages are obtained in the system.
A simple ansatz for the study of velocity autocorrelation functions in fluids at different timesc... more A simple ansatz for the study of velocity autocorrelation functions in fluids at different timescales is proposed. The ansatz is based on an effective summation of the infinite continued fraction at a reasonable assumption about convergence of relaxation times of the higher order memory functions, which have a purely kinetic origin. The VAFs obtained within our approach are compared with the results of the Markovian approximation for memory kernels. It is shown that although in the "overdamped" regime both approaches agree to a large extent at the initial and intermediate times of the system evolution, our formalism yields power law relaxation of the VAFs which is not observed at the description with a finite number of the collective modes. Explicit expressions for the transition times from kinetic to hydrodynamic regimes are obtained from the analysis of the singularities of spectral functions in the complex frequency plane.
The mechanism of spatio-temporal pattern formation at the catalytic oxidation of carbon monoxide ... more The mechanism of spatio-temporal pattern formation at the catalytic oxidation of carbon monoxide on the Pt(110) surface has been studied. The surface may contain structurally different areas, which are formed in the course of the CO-induced transition from the reconstructed 1×2 phase to the 1×1 (bulk) one. Temporal and spatial instabilities in the system are analyzed, by using the methods of the linear theory of stability and numerical simulations. Fragments of spatio-temporal structures of the oxygen coverage together with fragments of the surface 1 × 1 structure are shown to emerge on the inhomogeneous surface at certain system parameters. The distribution of the carbon monoxide coverage is found to be almost homogeneous in space and independent of the surface geometry.
ABSTRACT Using the collective variables (CV) method the basic relations of statistical field theo... more ABSTRACT Using the collective variables (CV) method the basic relations of statistical field theory of a multicomponent non-homogeneous fluids are reconsidered. The corresponding CV action depends on two sets of scalar fields - fields $\rho_{\alpha}$ connected to the local density fluctuations of the $\alpha$th species of particles and fields $\omega_{\alpha}$ conjugated to $\rho_{\alpha}$. The explicit expressions for the CV field correlations and their relation to the density correlation functions are found. The perturbation theory is formulated and a mean field level (MF) of the theory is considered in detail.
Advanced Problems of Phase Transition TheoryVolume 3, 2012
ABSTRACT For the last two decades, both phase diagrams and the critical behaviour of ionic fluids... more ABSTRACT For the last two decades, both phase diagrams and the critical behaviour of ionic fluids with dominant Coulomb interactions have been intensively studied using experimental and theoretical methods. In this chapter we present the overview of the progress made in this field. The main attention is focused on the theoretical results obtained for the primitive models of ionic fluids. We discuss the results of the mean field theories, in particular the Debye-Hückel theory and the mean spherical approximation as well as their generalizations related to the explicit inclusion of the ion association. We also review the recent results of statistical field theory that uses functional methods and allows one to go beyond the mean field approximation.
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