A study of cryostructuring of polymer systems. 45. Effect of porosity of dispersed filler on physicochemical characteristics of composite poly(vinyl alcohol) cryogels

Composite cryogels simulating the properties of waterproof screens of hydraulic structures, such as protruding dykes and dams, have been obtained by a cryogenic treatment (freezing at –10…–30°C followed by incubation in the frozen state for 12 h and defrosting at a rate of 0.03°C/min) of suspensions of calcium-carbonate-containing (marble or coquina) or cellulose-containing (microcrystalline cellulose or sawdust) particles in aqueous poly(vinyl alcohol) solutions. Viscometric examinations of initial suspensions have shown that adhesion contacts arise between filler particles, as well as discrete and continuous phases, already at the stage of suspension preparation, thereby affecting the properties of resulting cryogels. This is most pronounced when high-porosity sawdust is used as a filler. It has been shown that all the dispersed materials used in the work are “active” fillers for poly(vinyl alcohol) cryogels, these fillers increasing the rigidity of the formed composites. Therewith, porous particles, into which the polymer solution can penetrate, are more efficient. The dependence of the composite rigidity on the temperature of the cryogenic treatment has, as a rule, a bell-shaped pattern with a maximum in the region of –20°C. Being tested for water permeability, the obtained model composite cryogels have exhibited pronounced antifiltration properties (the filtration coefficient is ≤(1–2) × 10^–9 cm/s), thus indicating that such materials are promising for solving problems relevant to the protection of fascine hydraulic structures from erosion with snow water.     

Effect of competing binding modes on retention in chromatography and capillary electrophoresis. A theoretical consideration

A mathematical formalism has been developed to describe equilibrium in a system involving a single selector and a selectand molecule capable of binding to this selector by different modes. The generalization of this model to a multiselector system has also been considered. Applications of the developed equations in chromatography and CE are discussed.     

Metal derivatives of diterpenoid isosteviol

Metal salts (including transition metals salts) of chiral natural diterpenoid isosteviol and its hydrophosphoryl derivative were obtained for the first time. The compounds obtained can be used in pharmaceutics, metal catalysis, and also for creating new materials with magnetic properties.     

Search for the νμ → ντ oscillation with the OPERA hybrid detector

This work reviews the status of the international OPERA experiment aimed at searching for the ν_μ → ν_τ oscillation. Development of the emulsion techniques in the preceding DONUT and CHORUS experiments is described. A brief overview of the NOMAD experiment is given, in which properties of ν_τ interactions were thoroughly investigated. Characteristics of the CERN-Gran Sasso (CNGS) neutrino beam are given, the structure of the OPERA hybrid detector and the functions of its subsystems are considered, and the automatic emulsion scanning technique is briefly reviewed. Uncertainties in reconstruction of event parameters using the electronic and emulsion detectors are discussed and the procedure adopted in the experiment for identification of ν_τ interactions is described. The main sources of background in the search for ν_μ → ν_τ oscillation are considered. Topologies of the first two ν_τ candidates observed in the OPERA emulsion detector are presented. Possibilities of increasing the ν_τ interaction selection efficiency using multidimensional criteria are briefly discussed.     

Mixed implicit/explicit solvation models in quantum mechanical calculations of binding enthalpy for protein–ligand complexes

An approach to quantum mechanical investigation of interactions in protein–ligand complexes has been developed that treats the solvation effect in a mixed scheme combining implicit and explicit solvent models. In this approach, the first solvation shell of the solvent around the solute is modeled with a limited number of hydrogen bonded explicit solvent molecules. The influence of the remaining bulk solvent is treated as a surrounding continuum in the conductor‐like screening model (COSMO). The enthalpy term of the binding free energy for the protein–ligand complexes was calculated using the semiempirical PM3 method implemented in the MOPAC package, applied to a trimmed model of the protein–ligand complex constructed with special rules. The dependence of the accuracy of binding enthalpy calculations on size of the trimmed model and number of optimized parameters was evaluated. Testing of the approach was performed for 12 complexes of different ligands with trypsin, thrombin, and ribonuclease with experimentally known binding enthalpies. The root‐mean‐square deviation (RMSD) of the calculated binding enthalpies from experimental data was found as ～1 kcal/mol over a large range. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Effect of Pt and Pd Additives on the Hydrogen Sensitivity of Semiconductor Sensors and Their Catalytic Activity in Oxidation of Hydrogen

We have studied the effect of small additives of Pt and Pd on the hydrogen sensitivity of semiconductor adsorption sensors based on SnO₂ and on the catalytic activity of sensor materials of the same composition in oxidation of hydrogen. We have shown that as the amount of Pt or Pd increases, the catalytic activity increases and the sensitivity of the sensors passes through a maximum. The results obtained are explained taking into account the hydrogen spillover phenomenon. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 302–306, September–October, 2005.     

Sulfatbestimmung

Ohne Zusammenfassung     

Fluorescence spectra of some cross-conjugate ketones: Experiment and calculations based on the model of two-well adiabatic potentials

Fluorescent properties of some cross-conjugate ketones were studied at 4.2, 77, and 300 K. Anomalies were observed in the fluorescence and fluorescence-excitation spectra of one of the studied compounds; these anomalies consisted in a pronounced upset of mirror symmetry of the spectra and a large Stokes shift. The experimental spectra and the spectra calculated theoretically using the theory of two-well adiabatic potentials were subjected to a comparative analysis.     

On oscillations of a frictional pendulum

Conditions are established under which a standard limit cycle occurs in the system under consideration, or the trajectory closes under the influence of a stagnation domain. It is pointed out that when the solution falls into the stagnation domain it makes no sense to use the asymptotic method because of a large error __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 2, pp. 104–112, February 2006.     

Organylthiochloroacetylenes: III. Nucleophilic Addition of Di(2-phenylethyl)phosphine Oxide to Alkylthiochloroacetylenes: Configuration and Conformation of Adducts

Alkylthiochloroacetylenes regio- and stereospecifically react with di(2-phenylethyl)phosphine oxide in dioxane at 20-22°C in the presence of potassium hydroxide to form 1-chloro-2-(alkylthio)vinyl[di(2-phenylethyl)]phosphine oxides in a 78-85% yield. According to IR and ¹H and ^{3 1}P NMR data, dielectrometric measurements, and quantum-chemical calculations, the obtained adducts have the Z configuration and exist mainly in the sp,sp conformation.