Bifurcation in Rotational Spectra of Nonlinear AB2_2 Molecules

A classical microscopic theory of rovibrational motion at high angular momenta in symmetrical non-linear molecules AB$_2$ is derived within the framework of small oscillations near the stationary states of a rotating molecule. The full-dimensional analysis including stretching vibrations has confirmed the existence of the bifurcation predicted previously by means of the rigid-bender model. The formation of fourfold energy clusters has already been experimentally verified for H$_2$Se and it has been demonstrated in fully-dimensional quantum mechanical calculations using the MORBID computer program. We show in the present work that apart from the level clustering, the bifurcation produces physically important effects including molecular symmetry-breaking and a transition from the normal mode to the local mode limit for the stretching vibrations due to rovibrational interaction. The application of the present theory with realistic molecular potentials to the H$_2$Te, H$_2$Se and H$_2$S hydrides results in predictions of the bifurcation points very close to those calculated previously. However for the lighter H$_2$O molecule we find that the bifurcation occurs at higher values of the total angular momentum than obtained in previous estimations. The present work shows it to be very unlikely that the bifurcation in H$_2$O will lead to clustering of energy levels. This result is in agreement with recent variational calculations.Comment: latex, 19 pages including 2 figures provided as *.uu fil

Calculating energy levels of isomerizing tetra-atomic molecules. II. The vibrational states of acetylene and vinylidene

A general, full-dimensional computational method for the accurate calculation of rotationally and vibrationally excited states of tetra-atomic molecules is further developed. The resulting computer program may be run in serial and parallel modes and is particularly appropriate for molecules executing wide-amplitude motions and isomerizations. An application to the isomerizing acetylene∕vinylidene system is presented. Large-scale calculations using a coordinate system based on orthogonal satellite vectors have been performed in six dimensions and vibrational term values and wave functions for acetylene and vinylidene states up to ≈23000cm−1 above the potential minimum have been determined. This has permitted the characterization of acetylene and vinylidene states at and above the isomerization barrier. These calculations employ more extensive vibrational basis sets and hence consider a much higher density of states than in any variational calculations reported hitherto for this system. Comparison of the calculated density of states with that determined empirically suggests that our calculations are the most realistic achieved for this system to date. Indeed more states have been converged than in any previous study of this system. Calculations on lower lying excited states of acetylene based on HC–CH diatom-diatom coordinates give nearly identical results to those based on orthogonal satellite vectors. Comparisons are also made with calculations based on HH–CC diatom-diatom coordinates

Effect of ECAP on microstructure and mechanical properties of Cu-₁₄Fe microcomposite alloy

In current study the Cu-14%(wt.)Fe alloy was subjected to 1-10 ECAP passes via route A and, in addition, to 4 passes via routes Bc and C. Microstructure of the alloy after ECAP was characterized using SEM and EBSD analysis. It was shown that the refinement of Fe particles largely depended on the processing route: route A was the most efficient and route Bc was the less efficient. After 10 passes via route A the average thickness of Fe particles decreased to about 3 μm from about 10 μm in initial state. However, the microstructure development in Cu matrix was found to be not dependent much on ECAP route – the average grain/subgrain reached value of about 0.25 μm (according to EBSD analysis) after 4 passes. The mechanical properties of the alloy were also found to be not sensitive to ECAP route

Information visualisation for risk identification in cyber-physical systems

Cyber-physical systems (CPSs) are defined as combining of computational and physical systems (Lee, 2006). Examples may include production systems and also critical infrastructure systems, such as power and water supply, elecommunication networks, transportation, government and emergency services (Ouyang, 2014). Typically, CPSs are highly complex socio-technical structures on several levels of hierarchy, with various interactions between many actors, objects and processes. As such, modelling has been a common approach to abstraction and understanding of such complex CPSs (Ouyang, 2014). By modelling system entities and their interconnections, hierarchically decomposing them into subsystems, one can analyse the behaviour of CPSs as a whole, track their vulnerabilities and prescribe improvements to mitigate potential risks. While in practice traditionally, text, tables and diagrams are used as visual representations for system modeling, when the systems become too complex, these representations introduce information overload for the users. Though Unified Modelling Language (UML) (Fowler & Scott, 2004) and SysML (Friedenthal et al., 2014) diagrams are based on standardised and clearly defined logical conventions (Patou et al., 2018), the visual techniques used are often subpar and do not allow achieving efficient visual communication of underlying information to its users (Sindiy et al., 2013). Information Visualisation is a branch of Human-Computer Interaction that studies “computer-supported, interactive, visual representations of data to amplify cognition” (Card et al., 1999). By encoding information into a changeable medium, it is said that information visualisations improve the cognitive processing power of users, allow fast information search, and assist recognition of patterns (Card et al., 1999). Using the concept of Uncontrolled Flows of Information and Energy (UFoI-E) (Guzman & Kozin, 2018), it is possible to build interactive diagrams to depict threats and hazards, corresponding detection, prevention and containment measures with respect to cyber-, physical and cyber physical layer states of CPSs. In the present study, we discuss the application of Information Visualisation techniques to design a model representation for UFoI-E-related risk identification in CPSs. Through designing an interactive visualisation that displays CPSs and their behaviour under various attack scenarios, our aim is to improve users’ ability to systemise and make sense of potential hazards, their sources and appropriate defense strategies

Millisecond-range electron spin memory in singly-charged InP quantum dots

We report millisecond-range spin memory of resident electrons in an ensemble of InP quantum dots (QDs) under a small magnetic field of 0.1 T applied along the optical excitation axis at temperatures up to about 5 K. A pump-probe photoluminescence (PL) technique is used for optical orientation of electron spins by the pump pulses and for study of spin relaxation over the long time scale by measuring the degree of circular polarization of the probe PL as a function of pump-probe delay. Dependence of spin decay rate on magnetic field and temperature suggests two-phonon processes as the dominant spin relaxation mechanism in this QDs at low temperatures.Comment: 3 pages, 4 figures, submitted to Appl. Phys. Let

DEVELOPMENT OF NITROFURAN DERIVATIVE: COMPOSITION AND TECHNOLOGY OF EFFERVESCENT TABLETS WITH SOLID DISPERSIONS

Taking into account the current Product specification file, the aim of the work was to develop the composition and technology for obtaining effervescent tablets based on solid dispersions of furazolidone in the form of an aqueous solution for external use.Materials and methods. The used substances were: furazolidone, anhydrous sodium carbonate (chemically pure), polyvinylpyrrolidone-24000±2000 (chemically pure), malic acid (analytically pure), tartaric acid (chemically pure), citric acid (chemically pure), sodium benzoate (chemically pure), ethyl alcohol 96% (chemically pure), purified water. Preparation of granulates is separate wet granulation in a fluidized bed (Mycrolab, BOSCH, Germany). Obtaining tablets is the process of pressing on a manual hydraulic test press ("PRG", VNIR, Russia). The dependence of disintegration, abrasion capacity and crushing resistance on compacting pressure was investigated. Technological parameters of granulates, еру obtained effervescent tablets, shelf life and storage conditions were investigated according to the State Pharmacopoeia of the Russian Federation XIVth ed.Results. Two compositions of effervescent tablets containing solid dispersions of furazolidone as an active substance were obtained, which, when dissolved in 100 ml of water at room temperature (20°C), form a solution of furazolidone with a concentration of 0.004% in less than 5 minutes. The method of quantitative determination of the furazolidone content in the effervescent tablets was validated. A complex of physicochemical methods for the analysis of tablets was carried out. Quality standards have been developed. The developed compositions stability of instant tablets during storage during accelerated and long-term tests has been experimentally confirmed. The preliminary shelf life and storage conditions have been determined.Conclusion. The result of technological and chemical-pharmaceutical research is the creation and evaluation of the quality of a new instant furazolidone dosage form as effervescent tablet formulations