Extracting muon momentum scale corrections for hadron collider experiments

The quark condensate is calculated within the world-line effective-action formalism, by using for the Wilson loop an ansatz provided by the stochastic vacuum model. Starting with the relation between the quark and the gluon condensates in the heavy-quark limit, we diminish the current quark mass down to the value of the inverse vacuum correlation length, finding in this way a 64?% decrease in the absolute value of the quark condensate. In particular, we find that the conventional formula for the heavy-quark condensate cannot be applied to the c-quark, and that the corrections to this formula can reach 23?% even in the case of the b-quark. We also demonstrate that, for an exponential parametrization of the two-point correlation function of gluonic field strengths, the quark condensate does not depend on the non-confining non-perturbative interactions of the stochastic background Yang?CMills fields.     

Stereospecific [2 + 2]-cross-photocycloaddition in a supramolecular donor–acceptor complex

A bis(propylammonium) derivative of (E)-4-(4-mercaptostyryl)pyridine, which was synthesized for the first time, forms a highly stable bimolecular complex with a bis(18-crown-6 ether) derivative of (E)-stilbene in solution owing to ditopic coordination via hydrogen bonds. The complex formation results in much faster deactivation of the excited states of both compounds, which is explained by photoinduced electron transfer from the stilbene derivative to the styrylpyridinium dye. Despite this, the complexed olefins undergo [2?+?2]-cross-photocycloaddition upon selective excitation of the dye to afford solely the syn-cycloadduct. The retro-photocycloaddition occurs readily upon UV irradiation of the cycloadduct and leads to the initial bimolecular complex.     

The Effect of the Isocyanate–Hydroxyl Ratio on the Structure and Properties of Hard Polyurethanes

A comprehensive study has been carried out of the structure and rheological and physicomechanical properties of low-temperature curing polyurethane compositions based on polyisocyanate and a blend of hydroxyl-containing oligomers of different reactivity. The maximum curing rate and strength parameters (tensile strength and Young’s modulus) have been shown to be achieved at the ratio of the reacting groups NCO : OH = 1.1.     

Silver nanocomposites based on copolymers of N,N-diallyl-N’-acetylhydrazine with N-vinylpyrrolidone

Russian Chemical Bulletin - A method was developed for the preparation of polymer silver nanocomposites using copolymer of N, N-diallyl-N’-acetylliydrazine with N-vinylpyrrolidone as reducing...     

Incorporating C2 into C60 films

The material formed by depositing C(2)(-) anions onto/into thin C(60) films (on graphite) at room temperature has been studied by means of thermal desorption mass spectroscopy, ultraviolet photoionization spectroscopy, atomic force microscopy (AFM), and surface enhanced Raman spectroscopy. As-prepared, C(2)/C(60) films manifest thermal desorption behaviour which differs significantly from pure C(60) films. Whereas the latter can be fully sublimed, we observe decomposition of C(2)/C(60) films to a high-temperature-stable material while predominantly C(60), C(62), and C(64) are desorbed in parallel. Deposition of C(2)(-) also leads to significantly modified electronic and vibrational properties. Based on DFT model calculations of the Raman spectra, we suggest that as-prepared C(2)/C(60) films contain appreciable amounts of polymeric networks comprising -C(2)-C(60)-C(2)-C(60)- chains. Detection of sublimed C(62) and C(64) upon heating implies that thermal decomposition of C(2)/C(60) films involves addition/uptake of C(2) units into individual fullerene cages. Correspondingly, annealing films up to various intermediate temperatures results in significant modifications to valence-band UP spectra as well as to surface topographies as imaged by AFM. The novel carbonaceous material obtained by heating to T > 950 K has a finite density of states at the Fermi level in contrast to as-prepared C(2)/C(60). It comprises fused fullerene cages.     

Analysis of local rearrangements in chains during simulation of the plastic deformation of glassy polymethylene

A molecular-dynamics simulation of the low-temperature (～100 K below T _g) plastic deformation of glassy polymethylene (PM) was conducted. A model system consisting of 64 chains containing 100 CH₂ groups (the united-atoms approach) in each computational cell with periodic boundary conditions was considered. The behavior of 32 such cells was considered. Each cell was subjected to an active isothermal uniaxial compression at a constant temperature of T _def = 50 K to a strain of ? = 30%. An analysis showed that the inelastic deformation of glassy PM proceeded via nonaffine displacements (“gliding”) of chain fragments comprising 11–13 sites -CH₂-. These displacements are correlated and directed mainly along chain axes. Only a small number of conformational rearrangements occur in chains during the deformation of the material. Conformational transitions add only small additional displacements to nonaffine atomic transformations. A free-volume analysis using Voronoi-Delaunay tessellation in the deformed polymer did not show its relation to local plastic rearrangements.     

Computer simulation of rearrangements in chains of glassy polymethylene subjected at low temperature inelastic deformation

Molecular dynamics simulation of glassy polymethylene (PM) plastic deformation is performed up to ? = 30% in uniaxial compression regime at a temperature of 50 K, which is ～140 K below T _g of the polymer. All atoms of PM chains are represented explisitly (all-atom model). Calculations were performed for two series of samples with different molecular mass distribution of chains: Samples have average degree of polymerization DP ≈ 212 with Mn ≈ 3000 and Mw ≈ 9500 (the first series) and DP ≈ 350, Mn ≈ 5000 and Mw ≈ 9500 (the second series). Each sample contains 12288 -CH₂- monomeric units per computational sell. Nonaffine displacements of carbon atoms and conformational rearrangements in chains during deformation are visualized and analyzed. The transformation of relatively fragments of chains up to 16–20 monomer units length are basic structural units, non-conformational displacements of which controls plastic process. Relatively large nonaffine displacements are observed even in the range of low strains, which are usually interpreted as Hookean strains. In the range of yield tooth and steady plastic flow, the number of these displacements increases along with their amplitude. Conformational set of PM chains does not show a serious change during deformation. Analysis had shown that the number of conformational rearrangements of trans-gauche type in PM chains during deformation is small and such rearrangements do not play decisive role in the considered range of PM plasticity, even at ? > 15%, at the stage of the developed plastic flow.     

Extraction of triply charged metal cations in aqueous phase-separating system antipyrine–sulfosalicylic acid–water

Extraction of macro amounts of triply charged metal cations (0.01–0.05 mol L^?1) in aqueous phase-separating system antipyrine–sulfosalicylic acid–water containing no organic solvent is studied. Optimum conditions for phase separation are established and the influence of the concentrations of the major components, inorganic acids (H₂SO₄, HCl), salting-out agents, and the volume of the aqueous phase on the process in question is determined. It was found that the optimum antipyrine/sulfosalicylic acid ratio in the system was (1.5–2.0): 1.0. The introduction of inorganic salting-out agents causes the volume of the organic phase (0.8–1.8 mL) to increase to 2 mL and more. The extractability series of triply charged metal ions is as follows: Tl > Fe > Sc > In > Ga. It was shown that inorganic salts and hexamine influence the degree of extraction of metal cations and that inorganic acids and water affect the distribution mechanism and the composition of the complexes. The half-extraction pH values (pH₁/₂) of the cations are calculated and correlations between the pH₁/₂ values, the ionic radii of the cations, and the polarization ability of the metal ions are established.

     

A Generalized High-Elasticity Model to Describe the Stress-Strain Dependence for Polyurethane Elastomers When Stretched at a Constant Rate

The stress versus strain relationships for cross-linked polyetherurethane and polybutadieneurethane elastomers were investigated on samples when simply stretched at a constant rate. Use of the generalized approach earlier developed for equilibrium strain, with related improvements taking into account the relaxation nature of the elastomers, permitted successfully describing the investigated dependences.     

Coarse-grained polyethylene: 1. The simplest model for the orthorhombic crystal

The coarse-grained model of polyethylene and alkanes (the united-atom model, in which each CH₂ group is represented by a single bead) was proposed several decades ago. It is widely applied in molecular dynamics simulations. For different tasks, the models with different geometrical and force parameters are used. Until now, it was thought that the coarse-grained model of polyethylene cannot reproduce the orthorhombic crystalline phase, which is typical of this polymer. In the present study, we analyze the simplest coarse-grained model of polyethylene. In this model, the Lennard-Jones potential (6–12) is adopted for van der Waals interactions between the beads of different chains. Of the bonded interactions, only the “valence” bonds between beads and the “bond” and “torsion” angles are taken into account, whereas the cross terms between them are disregarded. We consider the model variation in which the bead (the force center with the mass of a CH₂ group) is displaced from the center of the carbon atom and all the interactions, both bonded and nonbonded, are defined by the positions of these beads. For this model, we find the area of geometrical parameters (the displacement value and the van der Waals radius of the bead) in which all the three known crystalline phases of polyethylene are at equilibrium at low temperatures. We choose the force field constants for the model so that its oscillation spectrum reproduces the low-frequency part of the inelastic neutron scattering spectrum of the orthorhombic polyethylene. It proved to be that this choice can be made unambiguously. We compare the dispersion curves in the terahertz range with experimental data on the Raman scattering and infrared spectroscopy, and discuss the advantages and disadvantages of the analyzed simplest coarse model.