Spillway construction at the Irganai HPP in Dagestan

Experience with the opening of inclined workings is presented. Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 6, June 2008, pp. 2–6.     

Confined Catalytic Janus Swimmers in a Crowded Channel: Geometry‐Driven Rectification Transients and Directional Locking

Self‐propelled Janus particles, acting as microscopic vehicles, have the potential to perform complex tasks on a microscopic scale, suitable, e.g., for environmental applications, on‐chip chemical information processing, or in vivo drug delivery. Development of these smart nanodevices requires a better understanding of how synthetic swimmers move in crowded and confined environments that mimic actual biosystems, e.g., network of blood vessels. Here, the dynamics of self‐propelled Janus particles interacting with catalytically passive silica beads in a narrow channel is studied both experimentally and through numerical simulations. Upon varying the area density of the silica beads and the width of the channel, active transport reveals a number of intriguing properties, which range from distinct bulk and boundary‐free diffusivity at low densities, to directional “locking” and channel “unclogging” at higher densities, whereby a Janus swimmer is capable of transporting large clusters of passive particles.     

Image Approximation by Rectangular Wavelet Transform

We study image approximation by a separable wavelet basis and ϕ,ψ are elements of a standard biorthogonal wavelet basis in L₂(ℝ). Because k₁≠ k₂, the supports of the basis elements are rectangles, and the corresponding transform is known as the rectangular wavelet transform. We provide a self-contained proof that if one-dimensional wavelet basis has M dual vanishing moments then the rate of approximation by N coefficients of rectangular wavelet transform is for functions with mixed derivative of order M in each direction. These results are consistent with optimal approximation rates for such functions. The square wavelet transform yields the approximation rate is for functions with all derivatives of the total order M. Thus, the rectangular wavelet transform can outperform the square one if an image has a mixed derivative. We provide experimental comparison of image approximation which shows that rectangular wavelet transform outperform the square one. Vyacheslav Zavadsky got his M.Sc. (with distinction) in computer science and applied mathematics from Belarusian State University in 1994 and his Ph.D. in mathematics and statistics in 1998 from Belarusian Academy of Sciences and Belarusian State University. He worked at Institute of Mathematics of Belarusian Academy of sciences, and Belarusian center for medical technologies. He also held progressively responsible technical and research positions in the industry: at MZOR, eBusiness technologies, and Webmotion. At present, he is the principal software architect with Semiconductor insights. His research interests include mathematical and statistical methods in vision; machine learning, and structural data mining. Vyacheslav is author of more then ten peer reviewed papers and conference presentation, and 7 pending inventions.     

Thermodynamic Studies of Interactions between Sertraline Hydrochloride and Randomly Methylated β-Cyclodextrin Molecules Supported by Circular Dichroism Spectroscopy and Molecular Docking Results

The interaction between sertraline hydrochloride (SRT) and randomly methylated β-cyclodextrin (RMβCD) molecules have been investigated at 298.15 K under atmospheric pressure. The method used—Isothermal Titration Calorimetry (ITC) enabled to determine values of the thermodynamic functions like the enthalpy (ΔH), the entropy (ΔS) and the Gibbs free energy (ΔG) of binding for the examined system. Moreover, the stoichiometry coefficient of binding (n) and binding/association constant (K) value have been calculated from the experimental results. The obtained outcome was compared with the data from the literature for other non-ionic βCD derivatives interacting with SRT and the enthalpy-entropy compensation were observed and interpreted. Furthermore, the connection of RMβCD with SRT was characterized by circular dichroism spectroscopy (CD) and complexes of βCD derivatives with SRT were characterized through the computational studies with the use of molecular docking (MD).     

Emerging 2D magnetic states in a graphene-based monolayer of EuC6

Recent discoveries of intrinsic two-dimensional(2D)magnets open up vast opportunities to address fundamental problems in condensed matter physics,giving rise to applications from ultra-compact spintronics to quantum computing.The ever-growing material landscape of 2D magnets lacks,however,carbon-based systems,prominent in other areas of 2D research.Magnetization measurements of the Eu/graphene compound-a monolayer of the EuC₆ stoichiometry-reveal the emergence of 2D ferromagnetism but detailed studies of competing magnetic states are still missing.Here,we employ element-selective X-ray absorption spectroscopy(XAS)and magnetic circular dichroism(XMCD)to establish the magnetic structure of monolayer EuC6.The system exhibits the anomalous Hall effect,negative magnetoresistance,and magnetization consistent with a ferromagnetic state but the saturation magnetic moment(about 2.5/%/Eu)is way too low for the half-filled f-shells of Eu²⁺ions.Combined XAS/XMCD studies at the Eu L3 absorption edge probe the EuC6 magnetism in high fields and reveal the nature of the missing magnetic moments.The results are set against XMCD studies in Eu/silicene and Eu/germanene to establish monolayer EuC6 as a prominent member of the family of Eu-based 2D magnets combining the celebrated graphene properties with a strong magnetism of europium.     

Synthesis and Properties of BiFeO3–DyMnO3 Solid Solutions

(1 – x)BiFeO₃–xDyMnO₃ solid solutions with x= 0.03–0.30 are synthesized for the first time, and their dielectric and magnetic properties are studied. The solid solutions with x 0.08 have a rhombohedrally distorted perovskite structure, and those with x = 0.10–0.30 have an orthorhombically distorted structure. The 1-kHz electrical conductivity of the solid solutions exhibits semiconducting behavior and rises exponentially with temperature. The dielectric properties of the solid solutions are investigated in the microwave range (0.5–2.5 GHz) between room temperature and 250°C. The real part of their room-temperature dielectric permittivity reaches a maximum at x= 0.20, while the largest tan is observed at x = 0.03. The solid solutions with x= 0.03–0.08 exhibit high dielectric losses and are, therefore, candidate microwave absorbing materials. The magnetic and electrical ordering temperatures in the composition range studied exceed room temperature; that is, these solid solutions are new high-temperature seignettomagnetic materials.     

Laminar Forced Convection in Curved Channel with Vortex Structures

Theoretical and experimental investigations of heat transfer in flat curvilinear channel have been carried out. Linear and non-linear effects of Dean vortexes on intensity of heat transfer were taken into account. The linear effect, which describe harmonic (sinuous) variation of the heat transfer coefficient near the concave surface of the channel and the non-linear effect causes the general increase of the heat transfer coefficient due to augmentation of heat transfer engendered by the Dean vortexes. For both effects, mathematical relations were obtained in the form of quadratures. These numerical results were modified to the form convenient in engineering calculations. The investigations have shown that both linear and nonlinear components grow up with the Dean number. Nonlinear component Q0T increases more abruptly, while the linear one Q1T is more conservative. This is a confirmation of stability of vortex structures.