338 research outputs found
Homoleptic Poly(nitrato) Complexes of Group 14 Stable at Ambient Conditions
Using a novel approach in homoleptic nitrate chemistry, Sn(NO3)62ā (3c) as well as the previously unknown hexanitrato complexes Si(NO3)62ā (1c), Ge(NO3)62ā (2c) were synthesized from the element tetranitrates as salt-like compounds which were isolated and characterized using 1H, 14N, and 29Si NMR and IR spectroscopies, elemental and thermal analyses, and single-crystal XRD. All hexanitrates are moderately air-sensitive at 298 K and possess greater thermal stability toward NO2 elimination than their charge-neutral tetranitrato congeners as solids and in solution. The complexes possess distorted octahedral coordination skeletons and adopt geometries that are highly symmetric (3c) or deformed (1c, 2c) depending on the degree of steric congestion of the ligand sphere. As opposed to the Īŗ2O,Oā² coordination mode reported for Sn(NO3)4 previously,1 all nitrato ligands of 3c coordinate in Īŗ1O mode. Six geometric isomers of E(NO3)62ā were identified as minima on the PES using DFT calculations at the B3LYP/6-311+G(d,p) level of which two were observed experimentally
Optimizing components of finite state machines composition based on donāt care input sequences in hardware implementation
The paper is devoted to the problem of optimization of discrete multi-module systems. The proposed optimization is based on iterative component-wise optimization. This approach has established itself as a promising approach due to its good scalability. We consider a technique that is based on the use of the so-called "donāt care" input sequences of the component, i.e. sequences that cannot appear at the input of a component under optimization in the composition and for this purpose, windows with sequential networks are selected. Preliminary experimental results illustrate that a proposed approach for the component-wise iterative optimization is effective for FSM networks when components are optimized for the further FPGA implementation
ETEKOS experimental ecological system
The problem of changes in the ecology resulting, for example, in increases in water temperature because of discharges from large thermal power plants is considered. An experiment creating a model of such an ecological system is described
Electroanalytical methods. Publications in 1999-2004
The scientometric study of publications on electrochemical methods of analysis (EMA) in a number of journals and proceedings of some conferences for 1999-2004 has been carried out. The contribution of papers on EMA to the total number of publications on analytical chemistry and the contribution of papers on individual methods (amperometry, voltammetry, including stripping and cyclic voltammetry, polarography, etc., potentiometry, including potentiometry with ion-selective electrodes, conductometry, coulometry, and other methods) to the total number of publications on EMA are estimated. Significant changes in the subject of publications, as well as in methodology and terminology, are noted over the period under review and compared to those over the earlier period. This is due to going from traditional studies to studies in the field of micro-and nanosized samples. The contributions of amperometry, electrochemiluminescence, chronoamperometry, chronopotentiometry, impedance measurements, spectroelectrochemical methods, and electrochemical microscopy have increased. It is noted that voltammetry and potentiometry are less used, but they are applied to the study of micro-and nanosized samples. In Russian publications, traditional trends of studies are retained. The contribution of publications on EMA to the total number of publications in analytical chemistry for 1946-2004 is estimated. It is ā¼ 20% on the average in the last 25 years. Ā© Nauka/Interperiodica 2006
Term "nano" in electroanalysis: A trendy prefix or a new stage of its development?
The use of term "nano" in electroanalytical methods (electroanalysis) is considered. Attention is paid to the recent trend in the development of electroanalysis in context of modern views on processes in the double electric layer, or interface, as a nanosize structure in an electrochemical nanoreactor determining the nature of the analytical signal. It is shown that the creation of new methods of chemical analysis of usual objects using nanostructures, nanosystems, and nanomaterials immobilized in an electrochemical interface has favored the development of nanoelectroanalytics. The use of terms with the prefix nano- in electroanalysis and some nanotechnologies is considered. It was noticed that the nomenclature in the nanofield has not been established yet. Not only the available terms should be refined and formulated, but also those that have not been adequately translated into Russian. With the application of nanotechnologies, electroanalysis follows the world trend in the choice of priority objects of analysis. Ā© 2013 Pleiades Publishing, Ltd
History of voltammetry in Russia
The paper considers the evolution of electroanalytical methods in the former Soviet Union and Russia for more than 50 years, including the establishment of scientific research centers, the development of new methods, and the formation of scientific schools. The history of voltammetry (VA) can be conventionally subdivided into two periods, the history of polarography (from the late 1930s to 1981-1987) and the history of VA in different versions. The material is obtained from original publications, reviews, and proceedings of specialized conferences. The role of academicians V.I. Vernadsky and A.P. Vinogradov in the formation and development of VA in the former Soviet Union is noted. It is shown that the first work on polarography in the former Soviet Union was published by E.N. Varasova, a colleague of Vernadsky and a former student of J. Heyrovsky and the translator of his first monograph. The statistics of conferences on polarography and conferences on electrochemical methods of analysis is presented; the high scientific and experimental level of Russian research centers is demonstrated; and the role of the school of electrochemistry established by A.N. Frumkin is shown. Ā© 2009 Pleiades Publishing, Ltd
Founder influences on the development of organizations: A comparison between founder and nonāfounder managed Russian firms
The paper deals with the problem of foundersā impact on the process of organizational development and performance. The goal of the research is to provide a comparative analysis of activity in founderārun and nonāfounderārun Russian firms. In order to run this analysis 224 companies created from scratch by Russian entrepreneurs in the period of years from 1992 to 1998 were studied.
Statistical analyses were performed on two independent samples of companies, namely 162 companies managed by the founders and 62 companies that were run by hired professional managers. As a result of the analysis, statistical differences were found in relation to the criteria of number of employees and hierarchical levels; firms managed by founders usually have less staff and fewer hierarchical levels than the nonāfounder companies. Nevertheless the dynamics in sales of the two samples of founder and nonāfounder companies during the last 3 years were quite similar.
First published online:Ā 14 Oct 201
The exact solution of a shock wave reflection problem from a wall shielded by a gas suspension layer
The paper is devoted to solving the shockwave reflection problem from a wall shielded by a gas suspension layer. The dynamics of the gas suspension are described in a two-speed two-temperature formulation. In contrast to the known approximate models of dusty gas based on the application of classical self-similar solutions by correcting gas dynamic
parameters and physical constants, an asymptotically exact solution is obtained. The analytical solution to the problem
is constructed in the form of a composition of elementary decays discontinuities. The nonequilibrium solution converges
to the exact one with a decrease in the characteristic times of dynamic and thermal relaxation of the carrier gas and
suspended particles of arbitrary concentration. Calculations based on the nonequilibrium model are performed by the
hybrid large-particle method of the second-order approximation in space and time. Both for the exact and calculate
profiles of the relative values of the pressure and density of the mixture, the normalized velocity of the dispersed phase
obtained from the nonequilibrium model are given. The influence of the intensity of the incident shock wave, as well
as the concentration of particles in the gas suspension layer on the parameters of the impact of the shock wave pulse
on the wall, is studied. The presence of a shielding layer leads to an increase in the reflection pressure from the wall
compared to the reflection of the shock wave in a pure gas. The analysis of the influence of the relaxation properties of the gas suspension layer with a change in particle sizes from 1 to 8 Ī¼m is carried out. For sufficiently small particles of 1 micron and the accepted scales of the problem, the nonequilibrium solution reproduces the shock-wave structure well and corresponds to the asymptotics. With the increase in the size of dispersed inclusions, the spatial relaxation zones, smoothing the profiles of the parameters, increase. The error in calculating the velocity and other parameters for
a nonequilibrium gas suspension with particles of 1 Ī¼m compared to the exact solution is in the range from 10ā7 to 10ā5. The results obtained are of practical importance in substantiating the influence of inert particle impurities on the dynamic loading of structures. The analytical solution to the problem may be in demand when testing various numerical schemes
Fraud in a digital society in the context of social change
The article analyzes the problems of fraud in the modern digital society in the context of social changes caused by both the COVID-19 pandemic and the current geopolitical situation. The authors study in detail the types of financial fraud in this area. They pay special attention to the types of digital fraud: telephone fraud and IP-telephony, SMS fraud, phishing, sniffering (message interception), skimming (theft of card data), which are associated with the emergence of cryptocurrencies. The article presents the data of the authorsā sociological research conducted by the method of an online questionnaire survey (n = 765). The study showed that only 44 % of respondents are sufficiently informed about the types of fraud to protect themselves from modern internet scammers. An analysis of data on certain types of digital fraud showed that 20 % of respondents lost money due to telephone or Internet fraud, 16 % of respondents personally encountered IP telephony, and 40 % have no idea about such a type of fraud as sniffering and existing anti-virus protection against it. The research also showed the vulnerability, first of all, of the male half of the population over 40 years of age in the field of internet fraud. Therefore, public authorities, together with the media, business and other actors of Russian society, need to strengthen the policy in the field of improving the level of financial and digital literacy of the population
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