Two-dimensional liquid chromatography of diblock copolymers: Simulation at various adsorption interaction conditions

Diblock copolymers, which are heterogeneous in both molar mass and composition, can be fully characterized by using two-dimensional chromatography. Since the size-exclusion, the adsorption, and the critical interaction based modes of chromatography are possible for each of the polymers A and B, this leads to a variety of options for 2D-chromatography of copolymers AB. Using the theory of chromatography of block copolymers, 2D-chromatograms are simulated that correspond to the most interesting of these options. Orthogonal 2D-chromatograms are expected, if in the 1st dimension the critical condition is created for A, while in the 2nd dimension – for B. The situations, where A and B are both adsorbable, as well as those where the conditions of adsorption for A and SEC for B are created, are also considered. In particular, it is shown that the 2nd dimension combination of the critical condition for A and SEC – for B is preferable than that with SEC condition for both A and B. The simulated 2D-chromatograms of low- and high molar mass diblock copolymers, as well as of copolymers with one short block are compared with the reported real ones; it is concluded that the corresponding virtual and real 2D-chromatograms are qualitatively very similar.     

Rejector Filters with Regulated Rejection Frequency Based on RC-Structures with Distributed Parameters Constructed on the Basis of Superionic Conductors

Application of RC-structures with distributed parameters for converting low- and infralow-frequency signals in analog microelectronics is studied. Two classic RC-circuits with distributed parameters as elements of rejector filters are studied. Functions of the transmission coefficient by voltage and current and calculated amplitude–frequency characteristics are presented. The rejection frequency in either circuit is regulated by electrically restructuring the overall resistance or overall capacitance of the RC-structure.     

Electromagnetic secondaries and punch-through effects in the CMS ME1/1

The aim of this work is to estimate the shower leakage from the CMS Endcap Hadron calorimeter (HE) due to electromagnetic secondaries and punch-through in the region of the ME1/1 Forward Muon Station. Two configurations are considered: with and without the CMS Endcap Electromagnetic calorimeter (EE). The experimental data have been taken during the combined beam test of CMS subdetectors (HE, ME, RPC, DT) at the CERN H2 beam facility in 2004. Serial CSC chambers (ready for installation in CMS) fully equipped with readout electronics have been exposed. Simulation of a beam test setup has been performed using the GEANT4-based simulation software package OSCAR. The text was submitted by the authors in English.     

Optical properties of thin films of closely packed SiO2 spheres

Ordered, closely packed, defect-free one-, two-, and three-layer thick films of SiO₂ spheres of diameter D varying from 0.6 to 1.4 μm were obtained. Their optical transmittance and reflectance spectra were measured in the range 0.3–2.5 eV. The one-layer structures reveal a transmittance minimum whose spectral position is described by the Bragg law with the plane separation equal to the sphere radius D/2. As the number of the layers increases, a spectral feature appears which signals the formation of a photonic gap in the 〈111〉 direction of the fcc crystal lattice and is determined by the distance between the {111} planes equal to 0.816D. The spectra of two-and three-layer structures measured with a diverging light beam contain additional lines originating from the formation of photonic gaps by the {111} and {221} planes. __________ Translated from Fizika Tverdogo Tela, Vol. 44, No. 6, 2002, pp. 1026–1031. Original Russian Text Copyright ? 2002 by Bazhenov, Gorbunov, Aldushin, Masalov, Emel’chenko.     

Liquid metal flow in a finite-length cylinder with a rotating magnetic field

A liquid metal flow induced by a rotating magnetic field in a cylindrical container of finite height was investigated experimentally. It was demonstrated that the flow in a rotating magnetic field is similar to geophysical flows: the fluid rotates uniformly with depth and the Ekman layer exists at the container bottom. Near the vertical wall the flow is depicted in the form of a confined jet whose thickness determines the instability onset in a rotating magnetic field. It was shown that the critical Reynolds number can be found by using the jet velocity u ₀ for Re _cr =u ² ₀/ u/ r. The effect of frequency of a magnetic field on the fluid flow was also studied. An approximate theoretical model is presented for describing the fluid flow in a uniform rotating magnetic field.List of Symbols U _r , U , U _z radial, azimuthal and vertical velocity components, respectively - B _r , U , B _z radial, azimuthal and vertical magnetic induction components - A vector potential of magnetic field - j induced electric current density - electrical conductivity of fluid - electrical potential - kinematic viscosity - tf electromagnetic volume force - angular velocity of fluid rotation - R container radius - H container height - aspect ratio - E Ekman number - Re _cr critical Reynolds number - r, z radial and axial coordinates     

Conditions of Rayleigh-Bénard convection onset and heat transfer in a near-critical medium

Thermal gravity convection in a horizontal layer of compressible perfect gas heated from below and a van der Waals gas near the critical state is investigated. The characteristics of the isentropic equilibrium of a compressible medium with a van der Waals equation of state are considered. The known conditions of convection onset in the perfect and van der Waals gases are checked on the basis of a solution of the complete and linearized equations. The restrictions imposed in deriving the known formulas for the adiabatic temperature gradients used in the conditions of absence and onset of convection are discussed. The characteristics of the convective heat transfer are examined, including the causes of the heat-transfer deterioration in the near-critical medium above the hydrostatic equilibrium threshold.     

Synthesis and proton conductivity of adsorption-saturated and solvated porous hydroxyethylated cyclam layers on the surface of PVC-coated cellulose fabric

Porous layers of associates of adsorption-saturated and benzene- and hexane-solvated chloride and sulfate of hydroxyethylated cyclams with acid aqua complexes were synthesized on the surface of PVC-coated cellulose fabric. The porous structure of the layers includes a system of internal pores connected with the external pores via the diamine rings of the common walls of the hydroxyethylated cyclam nets; the internal pores are filled with the associates; the solvent molecules are adsorbed on the developed surface of the layers or solvate it. The H⁺ motion rate in a layer placed in solvent vapors or liquid solvents was measured; the layers were found to be nonlinear H⁺ conductors. The potential of H⁺ transition from the acid solution into the layer, the H⁺ mobility constant, and the field variation constant of the H⁺ mobility of the layer depend on the layer composition. The adsorption and solvation are accompanied by the formation of host-guest molecular complexes between the diamine rings of the cyclam nets and the benzene or hexane molecules, affecting the resistance of the associates to the incorporation of H⁺ ions and the H⁺ mobility in the associates.     

Alkylation of pyrocatechol in <Emphasis Type="Italic">tert</Emphasis>-butyl alcohol-sulfuric acid-benzene

Alkylation of pyrocatechol with tert-butyl alcohol in benzene in the presence of sulfuric acid gave 3,5-di-tert-butylbenzene-1,2-diol in a higher yield than in analogous reaction with tert-butyl alcohol. This result was rationalized by reduction of inhibitory effect of liberated water, formation of heterogeneous system, and occurrence of the alkylation process in nonpolar organic phase. Intermediate products were identified and found to undergo intra- and intermolecular tert-butyl group transfer with formation of more stable 3,5-di-tertbutylbenzene-1,2-diol. The formation of p-di-tert-butylbenzene indicated participation of benzene in crossalkylation processes.     

Reachability of Optimal Convergence Rate Estimates for High-Order Numerical Convex Optimization Methods

Doklady Mathematics - The Monteiro–Svaiter accelerated hybrid proximal extragradient method (2013) with one step of Newton’s method used at every iteration for the approximate solution...