On a Simple Nonisothermal Adsorption Experiment with Organic Vapors and an Inertial Microbalance To Study the Surface Properties of Hybrid (Organic/Inorganic) Porous Materials

A nonisothermal adsorption experiment using a controlled flow of cyclopentane in the 333-313 K range is used to simultaneously estimate the specific surface area and micropore volume of a hybrid (organic/inorganic) alcogel. For reference, the method is also applied to an all-inorganic material with a more rigid structure, namely, a high surface area SiO(2)-Al(2)O(3). The proposed data analysis provides guidelines to determine whether adsorption data on a certain adsorbate/adsorbent system can be modeled effectively as a convolution of BET (meso- and macropore) and Dubinin-Radushkevitch (DR, micropore) contributions. Copyright 2000 Academic Press.     

Copolymerization of N-Vinylsuccinimide with Butyl Methacrylate in Pyridine

The kinetics of radical copolymerization of N-vinylsuccinimide with n-butyl methacrylate in pyridine was studied, and the previously unknown copolymerization constants of the monomers were determined. The calculations were performed using appropriate software and a new procedure for approximation of the experimental data, which allow determination of the kinetic parameters at high conversions with the minimum error. The copolymerization kinetics were compared for the reaction systems constituted by N-vinylsuccinimide and n-butyl methacrylate and by N-vinylsuccinimide and n-butyl acrylate.     

The interaction of erythromycin with polymeric sorbents adjusted to the antibiotic molecule

Cross-linked carboxylic cationites adjusted to sorption of the antibacterial antibiotic erythromycin were obtained by radical copolymerization of methacrylic acid, erythromycin methacrylate, and ethylene glycol dimethacrylate as a cross-linking agent. Studies of the sorption and desorption of erythromycin showed that adjusted sorbents had favorable equilibrium and kinetic characteristics of sorption and the ability to reversibly desorb the antibiotic. Original Russian Text ? O.A. Pisarev, N.M. Ezhova, I.S. Garkushina, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 1, pp. 142–146.     

Investigation of a fine structure of deuterium thermal desorption spectra from tungsten

The results of deuterium thermal desorption from tungsten after irradiation by 10 keV ions are discussed. A special heating procedure allows features of the fine structure of the thermal-desorption spectra maxima to be revealed.     

Magnetooptical study of granular silicon oxide films with embedded CoNbTa ferromagnetic particles

Granular silicon oxide films with embedded CoNbTa ferromagnetic particles and different relative contents of the metal and dielectric phases were studied using both steady-state and dynamic magnetooptical techniques with subpicosecond time resolution. Measurements were conducted in the spectral interval from 1.45 to 1.70 eV. The concentration dependences of the linear and photoinduced Kerr effects were found to behave similarly. Both relations are nonmonotonic with a maximum lying near the percolation threshold.     

Classification of holographic fringe patterns inherent in through hole drilling in residual stress field

Comparative analysis of actual fringe patterns, which are induced by combined implementing the hole drilling method and reflection hologram interferometry for residual stresses determination, is presented. Involved considerations are related to plane thin-walled structural elements. A set of interferograms of perfect (ideal) form is selected proceeding from one-side measurements. A base for recognising each specific ideal configuration is a fine coincidence between actual interferograms and analogous reference fringe patterns constructed for the same stress state. Perfect (ideal) both actual and reference fringe patterns are defined as a response of pure membrane 2D stress field on through hole drilling between exposures. Main principles of creating the regular catalogue of reference fringe patterns inherent in through hole drilling in thin-walled components are formulated. Emphasis is made on a careful collecting and classifying actual interferograms with clear indications of bending stress presence in total residual stress field. Evidences needed for a reliable classification of the type of residual stresses field of interest are established and verified. A response of superimposed residual stress field, which consists of both membrane and bending components, is characterised by various deviations of each specific fringe pattern from an ideal form. More deep analysis of fringe patterns related to superimposed residual stress field is based on specially designed technique. The main essence of the approach developed is simultaneous measurements of through hole distortions in two principal strain directions on opposite sides of thin plane specimen. These sides are faces of the drill entrance and exit. Sophisticated optical set-up that is capable of obtaining high-quality fringe patterns in the course of two-side measurements is developed and implemented. Typical set of fringe patterns obtained for single probe hole on opposite specimen faces is presented.     

Electron conductivity of a thermally ionized gas in an electric field

It is well known that the current carriers in a thermally ionized gas vary in composition, but that electrons [1] make the fundamental contribution to the conductivity of the gas, since their mobility is incomparably larger than that of other current-carrying particles. We shall thus be concerned only with electron conductivity. If the gas is under a high pressure in a weak electric field, then in estimating its electrical conductivity by classical means the same concepts are usually employed as those which Drude applied in the theory of metallic conduction. The Drude-Lorentz formula for electrical conductivity was subsequently perfected by Cowling and Chapman who introduced a coefficient to take into account the rate at which the particle interaction forces decrease with distance [2], For electron Coulomb interaction this coefficient takes the value 0.532 instead of 0.500 as compared with the Drude-Lorentz formula.For high pressures and low electric field strengths the electron drift velocity in the field is vanishingly small compared with the mean velocity of random motion, and so it is logical to suppose that the electron free time is independent of the drift velocity, and this supposition leads in the end to the conclusion that Ohm's law is applicable to gases at high pressure in very weak fields.However, we must not overlook the fact that even under the conditions mentioned the conclusion concerning the validity of Ohm's law is only an approximation which becomes less accurate, the lower the gas pressure and the greater the field strength.In what follows the conductivity of the gas is also determined by Drude's method, but with the refinement that in determining the electron free time the drift velocity of these particles in the field is considered.     

Modeling of processes in fuel cells based on sulfonic acid membranes and platinum clusters

The density functional theory with account for gradient correction (DFT/PBE) and periodical boundary conditions was used to model the main stages of processes occurring in hydrogen low-temperature fuel cells. Modeling was carried out at the example of calculation of catalytic anodic and cathodic processes occurring on the surface of the Pt₁₉ catalyst supported on a SnO₂ and water adsorption processes on the surface of a membrane represented by a crystal of metisylene sulfonic acid dihydrate [(CH₃)₃C₆H₂SO ₃ ^? · H₅O ₂ ⁺ ]. It was shown that the most energy-efficient process in the membrane is formation of crystals, in which two stoichiometric water molecules correspond to a single SO₃H group. Superstoichiometric water is adsorbed on the crystal surface with the adsorption energy of 0.3–0.6 eV; its transition inside the crystal is energy-consuming (2 eV). Barriers of surface proton conductivity are 0.2–0.3 eV.     

Spontaneous Magnetodielectric Effect and Its Coupling to the Lattice Dynamics in Fluoroperovskites

Journal of Experimental and Theoretical Physics - Experimental results on temperature dependences of the low-frequency dielectric permittivity of the group of magnetic fluoroperovskites with...