Effect of High Pressures on the Formation of New Compounds in the Al86Ni2Co6Gd6 Alloy

Physics of the Solid State - Using the X-ray diffraction and electron microscopy methods, the structure and the elemental and phase compositions of hypereutectic alloy Al86Ni2Co6Gd6 (hereinafter,...     

Relaxation of microparticles exposed to hydrodynamic forces in microfluidic conduits

The behavior of microparticles exposed to gravitational and lift forces and to the velocity gradient in flow velocity profile formed in microfluidic conduits is studied from the viewpoint of the transient period (the relaxation) between the moment at which a particle starts to be transported by the hydrodynamic flow and the time at which it reaches an equilibrium position, characterized by a balance of all active forces. The theoretical model allowing the calculation of the relaxation time is proposed. The numerical calculus based on the proposed model is compared with the experimental data obtained under different experimental conditions, namely, for different lengths of microfluidic channels, different average linear velocities of the carrier liquid, and different sizes and densities of the particles used in the study. The results are important for the optimization of microfluidic separation units such as microthermal field-flow fractionation channels in which the separation or manipulation of the microparticles of various origin, synthetic, natural, biological, etc., is performed under similar experimental conditions but by applying an additional thermodynamic force.

Structure and thermodynamics of hydrocarbon liquids: Computer simulation based on rism theory

A system of Ornstein-Zernike integral equations is solved numerically to determine the heats of vaporization ΔH_V of liquid ethane, propane, and n-butane. It is shown that the calculations (the deformations of valence bonds and bond angles in the liquid-phase molecules are ignored) give rather accurate values of ΔH_V, which are in agreement with the corresponding experimental data. On the other hand, it is established that if there are intramolecular rotational degrees of freedom, ΔH_V depends on the angle of internal rotation ϕ. The function ΔH_V(ϕ) is minimum for trans-conformations (ϕ=0) and maximum for cis-conformations (ϕ=180°). Hence, intermolecular interactions stabilize compact (convolute) conformations. The energy of this effect is of the order of 1 kJ/mole. Tver State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 5, pp. 808–813, September–October, 1995. Translated by I. Izvekova     

Monodisperse Particles Based on Copolymers of Methyl methacrylate or Styrene with N-Vinylformamide

Sammary: Various techniques of one-step batch emulsion copolymerization of methyl methacrylate (MMA) or styrene (St) with N-vinylformamide (NVF) initiated by 2,2′-azobis(2-methylpropanamidine) (AIBA) or 2,2′-azobis[4,5-dihydroimidazol-2-yl] (AIP) dihydrochlorides in the presence of dextran, cetyltrimethylammonium bromide (CTAB) or without any stabilizers were examined to obtain monodisperse submicron and nano- particles, having both positive surface charge and hydrophilic surface. After hydrolysis in acidic media, the particle surface contained amino groups originating from NVF units along with carboxylic groups from hydrolyzed initiator residues. The obtained particles were tested as building blocks of hierarchic structures. Owing to their amphiphilic surface, the particles were capable of self-assembling from their dispersions into three-dimentional (3D) ordered arrays.     

A Criterion for the Sequence of Roots of Holomorphic Function with Restrictions on Its Growth

Russian Mathematics - The main result of the paper is a criterion for a sequence of points in a domain of the complex plane, giving necessary and sufficient conditions under which this sequence of...     

Nonmonotonous relaxation processes in nonequilibrium nanoforming alloys of Al with transition and rare-earth metals

The temporal dependences of viscosity in Al₈₇Ni₈Y₅, Al₈₆Ni₈Ce₆, and Al₈₆Ni₈La₆ melts were measured at various temperatures after the solid-liquid phase transition. A nonmonotonous change in viscosity with the passage of time was found, due to the destruction of the nonequilibrium microheterogeneous state of melts inherited from the initial multiphase melts. We propose a mechanism of nonmonotonous relaxation of nonequilibrium microheterogeneous melts within the dynamical theory of a molecular field, assuming the emergence of a hierarchy of different relaxation times in the system. A theoretical temporal dependence of viscosity of melts is proposed that is qualitatively consistent with the experimental data.     

Direct opal-like structures consisting of monodisperse polymer particles and synthesis of the related inverse structures

Three-dimensional periodic solid-state film structures with a face-centered cubic lattice and a high degree of perfection have been prepared from monodisperse particles of styrene copolymers with methacrylic acid. It has been shown that these structures can be successfully used not only as model objects for studying specific features of light propagation in photonic crystals but also as templates for synthesizing inverse opal-like structures. The influence of the degree of hydrophilization of the surface layer of polymer particles forming a polymer template and the template synthesis conditions on the quality of an inverse opal-like TiO₂-based structure has been analyzed.     

Effect of polyaniline particle size on the properties of a polyaniline-nylon 6 composite

A method is proposed for the preparation of a conducting polyaniline-nylon 6 composite with controlled morphology of its surface. The method consists of the ammonium persulfate-induced oxidation polymerization of aniline in the presence of nylon 6. As has been established with the use of atomic force microscopy, spherical polyaniline particles are formed on the surface of nylon 6 and their sizes decrease with an increase in the duration of nylon 6 hydrothermal modification at 100° C. It is shown that a decline in polyaniline particle size in the polyaniline-nylon 6 composite enhances its reactivity with respect to KI.     

Microstructure and Physical and Mechanical Properties of the Al90Gd10 Binary Alloy after Barothermal Treatment

Physics of the Solid State - Using the microindentation, X-ray diffraction, optical microscopy, and electron microscopy methods, the microstructure and bulk physical and mechanical properties...     

Potentiometric monitoring DNA hybridization with polyaniline/Nylon-6 working electrode

Electrically conducting polymers are useful in various applications such as transistors and sensors. A potentiometric pH meter has been developed using polyaniline based working electrode and with improved selectivity using ionophores, the polyaniline based potentiometer has been applied to monitor various ions mainly in environmental applications. The polyaniline working electrode can be used to monitor not only the binding of a biological ionic macromolecules on polyaniline surface but also the binding of the adsorbed macromolecule with another macromolecule. We present first how the working electrode was prepared by polymerization of aniline in Nylon-6 matrix to provide the mechanical strength and then how single strand oligonucleotide probe binds with polyaniline surface. We then present how an electrode modification with mercaptoethanol results in a surface protected against non-specific binding and then finally we present the results of monitoring the complimentary strand binding leading to the formation of the double strand DNA. The text was submitted by the authors in English.