Diffusion of a passive scalar by convective flows under parametric disorder

We study transport of a weakly diffusive pollutant (a passive scalar) by thermoconvective flow in a fluid-saturated horizontal porous layer heated from below under frozen parametric disorder. In the presence of disorder (random frozen inhomogeneities of the heating or of macroscopic properties of the porous matrix), spatially localized flow patterns appear below the convective instability threshold of the system without disorder. Thermoconvective flows crucially effect the transport of a pollutant along the layer, especially when its molecular diffusion is weak. The effective (or eddy) diffusivity also allows to observe the transition from a set of localized currents to an almost everywhere intense "global" flow. We present results of numerical calculation of the effective diffusivity and discuss them in the context of localization of fluid currents and the transition to a "global" flow. Our numerical findings are in a good agreement with the analytical theory we develop for the limit of a small molecular diffusivity and sparse domains of localized currents. Though the results are obtained for a specific physical system, they are relevant for a broad variety of fluid dynamical systems.Comment: 12 pages, 4 figures, the revised version of the paper for J. Stat. Mech. (Special issue for proceedings of 5th Intl. Conf. on Unsolved Problems on Noise and Fluctuations in Physics, Biology & High Technology, Lyon (France), June 2-6, 2008

Advectional enhancement of eddy diffusivity under parametric disorder

Frozen parametric disorder can lead to appearance of sets of localized convective currents in an otherwise stable (quiescent) fluid layer heated from below. These currents significantly influence the transport of an admixture (or any other passive scalar) along the layer. When the molecular diffusivity of the admixture is small in comparison to the thermal one, which is quite typical in nature, disorder can enhance the effective (eddy) diffusivity by several orders of magnitude in comparison to the molecular diffusivity. In this paper we study the effect of an imposed longitudinal advection on delocalization of convective currents, both numerically and analytically; and report subsequent drastic boost of the effective diffusivity for weak advection.Comment: 14 pages, 6 figures, for Topical Issue of Physica Scripta "2nd Intl. Conf. on Turbulent Mixing and Beyond

Synthesis, optical and electrochemical properties of new thieno[2,3-b]indole-based dyes

Three new push-pull dyes consisting of a thieno[2,3-b]indole ring system as an electron donor, thiophene spacer as a π-bridge, and electron-withdrawing moieties such as 2-methylene malonitrile, 2-methylene-1Hindene- 1,3(2H)-dione, and 2-(2-methylene-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile, have been synthesized and studied for their application in organic electronics devices. Investigation of their optical and electrochemical properties reveal that these compounds possess narrow band gaps (1.7-2 eV) and an effective absorption in the visible spectral range (440-740 nm). Therefore, these chromophores can be regarded as promising light-harvesting materials. © 2018 ARKAT USA, Inc.Russian Science Foundation, RSF: 16-13-10435This research study was financially supported by the Russian Science Foundation (Project No. 16-13-10435)

ROLE OF BUSINESS-INCUBATOR IN SOCIAL PROTECTION OF ABLE-BODIED POPULATION

В статье рассматривается роль бизнес-инкубатора в социальной защите трудоспособного населения. Выявлены основные цели создания бизнес-инкубатора в зарубежных странах. Определены направления социально-экономического развития муниципального образования, которые могут развиваться за счет деятельности бизнес-инкубатора.In article, the role of business incubator in social protection of able-bodied population is considered. Main objectives of creation of business incubator in foreign countries are revealed. The directions of social and economic development of municipality, which can develop due to activity of business incubator, are defined

Forensic within the Framework of Expert-Analytical and Auditing Activities: Theoretical Research of the Concept

Topic. Economic development along with an increase in the number of companies leads to the growth of the number of economic (financial) crimes, including various types of fraud. The activities of many companies are currently aimed at identifying the facts of such fraud, in this connection there is a need for a forensic service. The article explores a new concept of “forensic” that is poorly studied both in Russian and foreign economies but is gaining popularity among people engaged in the economic sphere, as the number of economic crimes increases. The study of the concept was conducted with the aim of introducing the term into scientific circulation and contributing to correct understanding of its meaning. The definitions of the concepts “forensic” and “financial investigation” offered in the scientific literature by modern authors are presented. The main features that distinguish forensic from such forms of control as revision and examination are examined and analyzed. The list of forensic services offered by audit and consulting companies is presented and the directions of their implementation of the forensic service are described. Purpose. Complex author’s research of the term “forensic” which is new for Russian practice and represents a new direction in audit together with the study of national and foreign sources of literature to define the concept of forensic. Methodology. The study is based on the application of such methods as comparison, analysis and statistical method. Results. Forensic is one of the promising directions in the economic sphere that exists today and requires knowledge of various subjects: accounting, audit, criminalistics, psychology, sociology and some others. Forensic is an independent activity to investigate, analyze and develop procedures to counteract all types of financial fraud. Conclutions. The definition of the concept “forensic” is correlated with the concepts proposed by a number of foreign and domestic authors, but has a more extensive interpretation covering several definitions, which helps to better understand the essence of the new service. Forensic is a promising area of activity in the service sector as every year there is a growing trend of economic crimes

New tetrathiafulvalenes with thienyl- and other aromatic substituents, including fluorinated ones

A set of new tetrathiafulvalenes incorporating thienyl, aromatic, fluorinated aromatic substituens as well as oxadiazole moieties, attached to the tetrathiafulvalene core by long aliphatic chains, were synthesized. Key words. tetrathiafulvalene – thiophene – fluorine.

Synthesis, optical and electrochemical study of bipolar heterocyclic systems, including 1,2,4-oxadiazole moiety

Two new 3,5-dihetarylsubstituted 1,2,4- oxadiazoles 8 a,b, including N-alkyl substituted carbazole and thiophene moieties, were synthesized as potential components of materials for organic electronics devices. Optical and electrochemical properties of all new compounds were investigated. On the basis of the experimental UV absorption data, the values of bandgap energies equal to 3.44 eV (8a) and 3.05 eV (8b) were determined. The values of their ionization potentials, HOMO levels (−5.62 eV for 8a, −5.46 eV – for 8b), as well as their electron affinity levels, LUMO levels (−2.2 eV for 8a, −2.4 eV – for 8b), were calculated from the results of electrochemical studies. The energy of the triplet excited states of 8 a,b was defined with the help of time-dependent density functional theory (TD-DFT), comprising 2.68 eV (8a) and 2.32 eV (8b), where the greatest value of this parameter was for the compound with a shorter conjugation chain

New electroactive asymmetrical chalcones and therefrom derived 2-amino- / 2-(1H-pyrrol-1-yl)pyrimidines, containing an N-[ω-(4-methoxyphenoxy)alkyl]carbazole fragment: synthesis, optical and electrochemical properties

In this paper we present a synthetic approach to six new D–π–A–D conjugated chromophores containing the N-[ω-(4-methoxyphenoxy)alkyl]carbazole fragment. Such readily functionalizable heterocycle as carbazole was used as a main starting compound for their preparation. The investigation of the optical properties has shown that the positive solvatochromism is inherent to the chromophores containing an electron-withdrawing prop-2-en-1-one fragment, while the compounds containing a 2-aminopyrimidine moiety exhibit both positive and negative solvatochromism. The fluorescence quantum yields were experimentally determined for some of the synthesized chromophores; e.g., 1-(5-arylthiophen-2-yl)ethanones quantum yields were found to lie in an interval of 60–80%. Electrochemical oxidation of the synthesized chromophores has resulted in the formation of colored thin oligomeric films that became possible due to the presence of carbazole or pyrrole fragments with free electron-rich positions